Question: what is the role of t tubules

What Is the Function of Transverse Tubules? What Is the Function of Transverse Tubules?
What Is the Function of Transverse Tubules? What Is the Function of Transverse Tubules? What Is the Function of Transverse Tubules? By Staff Writer Last Updated Mar 24, 2020 5:20:01 PM ET
The primary duty of transverse tubules, or T-tubules, is to allow the conduction of electrical impulses. Transverse tubules exist as invaginations of sarcolemma, which are muscle fiber membranes. Transverse tubules comprise a triad, along with two parallel strands of sarcoplasmic reticulum, which varies in size and shape depending on muscle cell. Transverse tubules exist in plasma membranes within skeletal muscle and cardiac muscle cells. They appear as deep in invaginations within surrounding sheaths of sarcoplasmic reticulum, which is further broken down into myoglobin and mitochondria. In the process of creating invaginations, transverse tubules allow impulses to permeate the cell membrane, and ultimately excite, or activate, the sarcoplasmic reticulum. The sarcoplasmic reticulum, in turn, creates a network around sensitive myofibrils, which store and release critical supplies of calcium that enable muscle contractions. Transverse tubules act as transmitters and receivers of information during the process of conducting electrical impulses.

What Is the Function of Transverse Tubules?

What Is the Function of Transverse Tubules?
What Is the Function of Transverse Tubules?

What Is the Function of Transverse Tubules? What Is the Function of Transverse Tubules? By Staff Writer Last Updated Mar 24, 2020 5:20:01 PM ET
The primary duty of transverse tubules, or T-tubules, is to allow the conduction of electrical impulses. Transverse tubules exist as invaginations of sarcolemma, which are muscle fiber membranes. Transverse tubules comprise a triad, along with two parallel strands of sarcoplasmic reticulum, which varies in size and shape depending on muscle cell. Transverse tubules exist in plasma membranes within skeletal muscle and cardiac muscle cells. They appear as deep in invaginations within surrounding sheaths of sarcoplasmic reticulum, which is further broken down into myoglobin and mitochondria. In the process of creating invaginations, transverse tubules allow impulses to permeate the cell membrane, and ultimately excite, or activate, the sarcoplasmic reticulum. The sarcoplasmic reticulum, in turn, creates a network around sensitive myofibrils, which store and release critical supplies of calcium that enable muscle contractions. Transverse tubules act as transmitters and receivers of information during the process of conducting electrical impulses.

What is the T tubules function in muscle contraction? What is the T tubules function in muscle contraction?
Asked by: Ibrahym Antinori
What is the T tubules function in muscle contraction?
 The function of T-TUBULES is to conduct impulses from the surface of the cell (SARCOLEMMA) down into the cell and, specifically, to another structure in the cell called the SARCOPLASMIC RETICULUM. Click to see full answer. In this way, what are T tubules in muscle? T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the centre of skeletal and cardiac muscle cells. Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronising calcium release throughout the cell. Similarly, do T tubules have voltage gated channels? Action potentials are conducted into the interior of muscle fibers via the T-tubules and there activate voltage-gated channels known as dihydropyridine receptors (DHPR). Unlike in cardiac muscle, very little calcium enters the muscle fiber from the extracellular space (via the DHPR). Regarding this, how would you explain skeletal muscle cell contraction were there no T tubules? 2012).

What is the T tubules function in muscle contraction?

What is the T tubules function in muscle contraction?
Asked by: Ibrahym Antinori
What is the T tubules function in muscle contraction?

The function of T-TUBULES is to conduct impulses from the surface of the cell (SARCOLEMMA) down into the cell and, specifically, to another structure in the cell called the SARCOPLASMIC RETICULUM. Click to see full answer. In this way, what are T tubules in muscle? T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the centre of skeletal and cardiac muscle cells. Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronising calcium release throughout the cell. Similarly, do T tubules have voltage gated channels? Action potentials are conducted into the interior of muscle fibers via the T-tubules and there activate voltage-gated channels known as dihydropyridine receptors (DHPR). Unlike in cardiac muscle, very little calcium enters the muscle fiber from the extracellular space (via the DHPR). Regarding this, how would you explain skeletal muscle cell contraction were there no T tubules? 2012).

What is the T tubules function in muscle contraction? What is the T tubules function in muscle contraction?
Asked by: Ibrahym Antinori
What is the T tubules function in muscle contraction?
 What is the T tubules function in muscle contraction? Asked by: Ibrahym Antinori
asked in category: General Last Updated: 24th January, 2020
What is the T tubules function in muscle contraction? The function of T-TUBULES is to conduct impulses from the surface of the cell (SARCOLEMMA) down into the cell and, specifically, to another structure in the cell called the SARCOPLASMIC RETICULUM. Click to see full answer. In this way, what are T tubules in muscle? T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the centre of skeletal and cardiac muscle cells. Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronising calcium release throughout the cell.

What is the T tubules function in muscle contraction? Asked by: Ibrahym Antinori
asked in category: General Last Updated: 24th January, 2020
What is the T tubules function in muscle contraction? The function of T-TUBULES is to conduct impulses from the surface of the cell (SARCOLEMMA) down into the cell and, specifically, to another structure in the cell called the SARCOPLASMIC RETICULUM. Click to see full answer. In this way, what are T tubules in muscle? T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the centre of skeletal and cardiac muscle cells. Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronising calcium release throughout the cell.

What is the function of the t-tubules in a muscle contraction? | Yahoo Answers What is the function of the t-tubules in a muscle contraction?
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What is the function of the t-tubules in a muscle contraction?
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5 Answers
Calcium flows through t-tubules.
In response to stimulation, calcium channels in t-tubules open and allow calcium to flow down it's electro-chemical gradient into the cell. In skeletal muslce it contributes greatly to muscle contraction.
The purpose of t-tubules is to allow depolarization to quickly penetrate to the interior of the cell. The t-tubules help to bring the extracellular environment to all parts of the muscle cell more quickly which better coordinates muscle contraction.
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RE:
What is the function of the t-tubules in a muscle contraction?
What is passed through the t-tubules to allow for a muscle contraction?
The T-tubules are part of the triad that interconnect the sarcoplasmic reticulum (SR). They make contact with the terminal cisternae of the SR.
Their function is to conduct the action potential throughout the muscle fiber, deeper into the muscle for contraction.
How do you think about the answers? You can sign in to vote the answer.
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the_man_60
the_man_60
asked in Science & Mathematics Biology · 1 decade ago
What is the function of the t-tubules in a muscle contraction? What is passed through the t-tubules to allow for a muscle contraction? 5 Answers
Relevance
Sondra
1 decade ago
Favorite Answer
Calcium flows through t-tubules. In response to stimulation, calcium channels in t-tubules open and allow calcium to flow down it's electro-chemical gradient into the cell. In skeletal muslce it contributes greatly to muscle contraction. The purpose of t-tubules is to allow depolarization to quickly penetrate to the interior of the cell. The t-tubules help to bring the extracellular environment to all parts of the muscle cell more quickly which better coordinates muscle contraction. ...Show more
Source (s): Degree in molecular biology and am currently in medical school.

What is the function of the t-tubules in a muscle contraction? | Yahoo Answers

What is the function of the t-tubules in a muscle contraction?
Trending News
What is the function of the t-tubules in a muscle contraction?
What is passed through the t-tubules to allow for a muscle contraction?
5 Answers
Calcium flows through t-tubules.
In response to stimulation, calcium channels in t-tubules open and allow calcium to flow down it's electro-chemical gradient into the cell. In skeletal muslce it contributes greatly to muscle contraction.
The purpose of t-tubules is to allow depolarization to quickly penetrate to the interior of the cell. The t-tubules help to bring the extracellular environment to all parts of the muscle cell more quickly which better coordinates muscle contraction.
This Site Might Help You.
RE:
What is the function of the t-tubules in a muscle contraction?
What is passed through the t-tubules to allow for a muscle contraction?
The T-tubules are part of the triad that interconnect the sarcoplasmic reticulum (SR). They make contact with the terminal cisternae of the SR.
Their function is to conduct the action potential throughout the muscle fiber, deeper into the muscle for contraction.
How do you think about the answers? You can sign in to vote the answer.

'Dirty secret' plagues women in retirement, expert warns
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Promoted
the_man_60
the_man_60
asked in Science & Mathematics Biology · 1 decade ago
What is the function of the t-tubules in a muscle contraction? What is passed through the t-tubules to allow for a muscle contraction? 5 Answers
Relevance
Sondra
1 decade ago
Favorite Answer
Calcium flows through t-tubules. In response to stimulation, calcium channels in t-tubules open and allow calcium to flow down it's electro-chemical gradient into the cell. In skeletal muslce it contributes greatly to muscle contraction. The purpose of t-tubules is to allow depolarization to quickly penetrate to the interior of the cell. The t-tubules help to bring the extracellular environment to all parts of the muscle cell more quickly which better coordinates muscle contraction. ...Show more
Source (s): Degree in molecular biology and am currently in medical school.

What is the function of the t-tubules in a muscle contraction? | Yahoo Answers What is the function of the t-tubules in a muscle contraction?
Trending News
What is the function of the t-tubules in a muscle contraction?
What is passed through the t-tubules to allow for a muscle contraction?
5 Answers
Calcium flows through t-tubules.
In response to stimulation, calcium channels in t-tubules open and allow calcium to flow down it's electro-chemical gradient into the cell. In skeletal muslce it contributes greatly to muscle contraction.
The purpose of t-tubules is to allow depolarization to quickly penetrate to the interior of the cell. The t-tubules help to bring the extracellular environment to all parts of the muscle cell more quickly which better coordinates muscle contraction.
This Site Might Help You.
RE:
What is the function of the t-tubules in a muscle contraction?
What is passed through the t-tubules to allow for a muscle contraction?
The T-tubules are part of the triad that interconnect the sarcoplasmic reticulum (SR). They make contact with the terminal cisternae of the SR.
Their function is to conduct the action potential throughout the muscle fiber, deeper into the muscle for contraction.
How do you think about the answers? You can sign in to vote the answer.
 In skeletal muslce it contributes greatly to muscle contraction. The purpose of t-tubules is to allow depolarization to quickly penetrate to the interior of the cell. The t-tubules help to bring the extracellular environment to all parts of the muscle cell more quickly which better coordinates muscle contraction. ...Show more
Source (s): Degree in molecular biology and am currently in medical school. Garrott
6 years ago
This Site Might Help You. RE: What is the function of the t-tubules in a muscle contraction? What is passed through the t-tubules to allow for a muscle contraction? ...Show more
Source (s):

In skeletal muslce it contributes greatly to muscle contraction. The purpose of t-tubules is to allow depolarization to quickly penetrate to the interior of the cell. The t-tubules help to bring the extracellular environment to all parts of the muscle cell more quickly which better coordinates muscle contraction. ...Show more
Source (s): Degree in molecular biology and am currently in medical school. Garrott
6 years ago
This Site Might Help You. RE: What is the function of the t-tubules in a muscle contraction? What is passed through the t-tubules to allow for a muscle contraction? ...Show more
Source (s):

What is the function of the t-tubules in a muscle contraction? | Yahoo Answers What is the function of the t-tubules in a muscle contraction?
Trending News
What is the function of the t-tubules in a muscle contraction?
What is passed through the t-tubules to allow for a muscle contraction?
5 Answers
Calcium flows through t-tubules.
In response to stimulation, calcium channels in t-tubules open and allow calcium to flow down it's electro-chemical gradient into the cell. In skeletal muslce it contributes greatly to muscle contraction.
The purpose of t-tubules is to allow depolarization to quickly penetrate to the interior of the cell. The t-tubules help to bring the extracellular environment to all parts of the muscle cell more quickly which better coordinates muscle contraction.
This Site Might Help You.
RE:
What is the function of the t-tubules in a muscle contraction?
What is passed through the t-tubules to allow for a muscle contraction?
The T-tubules are part of the triad that interconnect the sarcoplasmic reticulum (SR). They make contact with the terminal cisternae of the SR.
Their function is to conduct the action potential throughout the muscle fiber, deeper into the muscle for contraction.
How do you think about the answers? You can sign in to vote the answer.
 function tubules muscle contraction: https://shortly.im/cnfo3
HulaGirl5
1 decade ago
The T-tubules are part of the triad that interconnect the sarcoplasmic reticulum (SR). They make contact with the terminal cisternae of the SR. Their function is to conduct the action potential throughout the muscle fiber, deeper into the muscle for contraction. ...Show more
doolin
Lv 4
5 years ago
T Tubules
Source (s): https://shrink.im/a8fe4
How do you think about the answers? You can sign in to vote the answer. Dr. L
Lv 5
1 decade ago
why ask when you can look it up and learn more
http://en.wikipedia.org/wiki/T-tubule
Still have questions? Get your answers by asking now. Ask Question

function tubules muscle contraction: https://shortly.im/cnfo3
HulaGirl5
1 decade ago
The T-tubules are part of the triad that interconnect the sarcoplasmic reticulum (SR). They make contact with the terminal cisternae of the SR. Their function is to conduct the action potential throughout the muscle fiber, deeper into the muscle for contraction. ...Show more
doolin
Lv 4
5 years ago
T Tubules
Source (s): https://shrink.im/a8fe4
How do you think about the answers? You can sign in to vote the answer. Dr. L
Lv 5
1 decade ago
why ask when you can look it up and learn more
http://en.wikipedia.org/wiki/T-tubule
Still have questions? Get your answers by asking now. Ask Question

T-Tubule Function in Mammalian Cardiac Myocytes | Circulation Research T-Tubule Function in Mammalian Cardiac Myocytes
T-Tubule Function in Mammalian Cardiac Myocytes
Abstract
Occurrence and Morphology of the T-Tubules
T-Tubule Development Is Labile
Proteins Present in the T-Tubule Membrane
Ca2+-Handling Proteins
Na+-Handling Proteins
K+-Handling Proteins
Anion-Handling Proteins
Second-Messenger Pathways
Interpretation of Immunohistochemical Data
Protein Colocalization Within, and With Proteins Adjacent to, the T-Tubules
Localization of Function
Cells Lacking T-Tubules
Diffusion Studies
Scanning Pipette
Detubulation
Functional Role
Electrical Properties of T-Tubules
Coupling of Ca 2+ Entry and Ca 2+ Release
Ca 2+ Efflux
Signal Transduction
Changes During Development and Disease
T-Tubule Development and Morphology in Hypertrophy and Failure
Changes in Protein Expression in Development, Hypertrophy, and Failure
Relevance of Changes in T-Tubule Structure and Protein Expression to Function
Conclusions and Unanswered Questions
Footnotes
References
 2003;92:1182–1192
Abstract
The transverse tubules (t-tubules) of mammalian cardiac ventricular myocytes are invaginations of the surface membrane. Recent studies have suggested that the structure and function of the t-tubules are more complex than previously believed; in particular, many of the proteins involved in cellular Ca 2+ cycling appear to be concentrated at the t-tubule. Thus, the t-tubules are an important determinant of cardiac cell function, especially as the main site of excitation-contraction coupling, ensuring spatially and temporally synchronous Ca 2+ release throughout the cell. Changes in t-tubule structure and protein expression occur during development and in heart failure, so that changes in the t-tubules may contribute to the functional changes observed in these conditions. The purpose of this review is to provide an overview of recent studies of t-tubule structure and function in cardiac myocytes. The transverse tubules (t-tubules) of mammalian cardiac ventricular myocytes are invaginations of the surface membrane that occur at the Z line and have both transverse and longitudinal elements. Many of the proteins involved in excitation-contraction coupling appear to be concentrated at the t-tubules. Therefore, it has been suggested that the t-tubules play a central role in cell activation. In the present review, we will consider the immunohistochemical and functional evidence for protein localization at the t-tubules, potential problems in the interpretation of such data, and the functional consequences of such localization.

T-Tubule Function in Mammalian Cardiac Myocytes | Circulation Research

T-Tubule Function in Mammalian Cardiac Myocytes
T-Tubule Function in Mammalian Cardiac Myocytes
Abstract
Occurrence and Morphology of the T-Tubules
T-Tubule Development Is Labile
Proteins Present in the T-Tubule Membrane
Ca2+-Handling Proteins
Na+-Handling Proteins
K+-Handling Proteins
Anion-Handling Proteins
Second-Messenger Pathways
Interpretation of Immunohistochemical Data
Protein Colocalization Within, and With Proteins Adjacent to, the T-Tubules
Localization of Function
Cells Lacking T-Tubules
Diffusion Studies
Scanning Pipette
Detubulation
Functional Role
Electrical Properties of T-Tubules
Coupling of Ca 2+ Entry and Ca 2+ Release
Ca 2+ Efflux
Signal Transduction
Changes During Development and Disease
T-Tubule Development and Morphology in Hypertrophy and Failure
Changes in Protein Expression in Development, Hypertrophy, and Failure
Relevance of Changes in T-Tubule Structure and Protein Expression to Function
Conclusions and Unanswered Questions
Footnotes
References

2003;92:1182–1192
Abstract
The transverse tubules (t-tubules) of mammalian cardiac ventricular myocytes are invaginations of the surface membrane. Recent studies have suggested that the structure and function of the t-tubules are more complex than previously believed; in particular, many of the proteins involved in cellular Ca 2+ cycling appear to be concentrated at the t-tubule. Thus, the t-tubules are an important determinant of cardiac cell function, especially as the main site of excitation-contraction coupling, ensuring spatially and temporally synchronous Ca 2+ release throughout the cell. Changes in t-tubule structure and protein expression occur during development and in heart failure, so that changes in the t-tubules may contribute to the functional changes observed in these conditions. The purpose of this review is to provide an overview of recent studies of t-tubule structure and function in cardiac myocytes. The transverse tubules (t-tubules) of mammalian cardiac ventricular myocytes are invaginations of the surface membrane that occur at the Z line and have both transverse and longitudinal elements. Many of the proteins involved in excitation-contraction coupling appear to be concentrated at the t-tubules. Therefore, it has been suggested that the t-tubules play a central role in cell activation. In the present review, we will consider the immunohistochemical and functional evidence for protein localization at the t-tubules, potential problems in the interpretation of such data, and the functional consequences of such localization.

What is the function of the t-tubules in a muscle contraction? | Yahoo Answers What is the function of the t-tubules in a muscle contraction?
Trending News
What is the function of the t-tubules in a muscle contraction?
What is passed through the t-tubules to allow for a muscle contraction?
5 Answers
Calcium flows through t-tubules.
In response to stimulation, calcium channels in t-tubules open and allow calcium to flow down it's electro-chemical gradient into the cell. In skeletal muslce it contributes greatly to muscle contraction.
The purpose of t-tubules is to allow depolarization to quickly penetrate to the interior of the cell. The t-tubules help to bring the extracellular environment to all parts of the muscle cell more quickly which better coordinates muscle contraction.
This Site Might Help You.
RE:
What is the function of the t-tubules in a muscle contraction?
What is passed through the t-tubules to allow for a muscle contraction?
The T-tubules are part of the triad that interconnect the sarcoplasmic reticulum (SR). They make contact with the terminal cisternae of the SR.
Their function is to conduct the action potential throughout the muscle fiber, deeper into the muscle for contraction.
How do you think about the answers? You can sign in to vote the answer.
 Garrott
6 years ago
This Site Might Help You. RE: What is the function of the t-tubules in a muscle contraction? What is passed through the t-tubules to allow for a muscle contraction? ...Show more
Source (s): function tubules muscle contraction: https://shortly.im/cnfo3
HulaGirl5
1 decade ago
The T-tubules are part of the triad that interconnect the sarcoplasmic reticulum (SR). They make contact with the terminal cisternae of the SR. Their function is to conduct the action potential throughout the muscle fiber, deeper into the muscle for contraction. ...Show more
doolin
Lv 4
5 years ago
T Tubules
Source (s):

Garrott
6 years ago
This Site Might Help You. RE: What is the function of the t-tubules in a muscle contraction? What is passed through the t-tubules to allow for a muscle contraction? ...Show more
Source (s): function tubules muscle contraction: https://shortly.im/cnfo3
HulaGirl5
1 decade ago
The T-tubules are part of the triad that interconnect the sarcoplasmic reticulum (SR). They make contact with the terminal cisternae of the SR. Their function is to conduct the action potential throughout the muscle fiber, deeper into the muscle for contraction. ...Show more
doolin
Lv 4
5 years ago
T Tubules
Source (s):

 T-tubule - Wikipedia
T-tubule
From Wikipedia, the free encyclopedia
  (Redirected from Transverse tubule)
Jump to navigationJump to search
Invagination of the plasma membrane of a muscle cell that extends inward from the cell surface around each myofibril; the ends of T-tubules make contact with the sarcoplasmic reticulum membrane
T-tubule
Skeletal muscle, with T-tubule labelled in zoomed in image. T-tubule structure and relationship to the sarcoplasmic reticulumin skeletal muscle
Details
Part of
Cell membraneof Skeletal muscleand cardiac musclecells. Identifiers
Latin
tubulus transversus
TH
H2.00.05.2.01018, H2.00.05.2.02013
Anatomical terminology
[edit on Wikidata]
T-tubules(transverse tubules) are extensions of the  cell membrane that penetrate into the centre of skeletaland cardiac musclecells. With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potentialinto the cell, and also play an important role in regulating cellular calcium concentration. Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronising calcium release throughout the cell.[1] T-tubule structure may be affected by disease, potentially contributing to heart failureand arrhythmias. Although these structures were first seen in 1897, research into T-tubule biology is ongoing. Contents
1Structure
1.1Regulators
2Function
2.1Excitation-contraction coupling
2.2Calcium control
2.3Detubulation
3History
4Clinical significance
5See also
6References
Structure[edit]
T-tubules are tubules formed from the same phospholipid bilayeras the surface membrane or sarcolemmaof skeletal or cardiac muscle cells.[1] They connect directly with the sarcolemma at one end before travelling deep within the cell, forming a network of tubules with sections running both perpendicular (transverse) to and parallel (axially) to the sarcolemma.[1] Due to this complex orientation, some refer to T-tubules as the transverse-axial tubular system.[2] The inside or lumen of the T-tubule is open at the cell surface, meaning that the T-tubule is filled with fluid containing the same constituents as the solution that surrounds the cell (the extracellular fluid). Rather than being just a passive connecting tube, the membrane that forms T-tubules is highly active, being studded with proteins including L-type calcium channels, sodium-calcium exchangers, calcium ATPases and Beta adrenoceptors. [ 1]
T-tubules are found in both atrialand ventricularcardiac muscle cells (cardiomyocytes), in which they develop in the first few weeks of life.[3] They are found in ventricular muscle cells in most species, and in atrial muscle cells from large mammals.[4] In cardiac muscle cells, T-tubules are between 20 and 450 nanometers in diameter and are usually located in regions called Z-discswhere the actin filaments anchor within the cell.[1] T-tubules within the heart are closely associated with the intracellular calcium store known as the sarcoplasmic reticulumin specific regions referred to as terminal cisternae.

What is the function of the t-tubules in a muscle contraction? | Yahoo Answers What is the function of the t-tubules in a muscle contraction?
Trending News
What is the function of the t-tubules in a muscle contraction?
What is passed through the t-tubules to allow for a muscle contraction?
5 Answers
Calcium flows through t-tubules.
In response to stimulation, calcium channels in t-tubules open and allow calcium to flow down it's electro-chemical gradient into the cell. In skeletal muslce it contributes greatly to muscle contraction.
The purpose of t-tubules is to allow depolarization to quickly penetrate to the interior of the cell. The t-tubules help to bring the extracellular environment to all parts of the muscle cell more quickly which better coordinates muscle contraction.
This Site Might Help You.
RE:
What is the function of the t-tubules in a muscle contraction?
What is passed through the t-tubules to allow for a muscle contraction?
The T-tubules are part of the triad that interconnect the sarcoplasmic reticulum (SR). They make contact with the terminal cisternae of the SR.
Their function is to conduct the action potential throughout the muscle fiber, deeper into the muscle for contraction.
How do you think about the answers? You can sign in to vote the answer.
 What is the function of the t-tubules in a muscle contraction? | Yahoo Answers
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Promoted
the_man_60
the_man_60
asked in Science & Mathematics Biology · 1 decade ago
What is the function of the t-tubules in a muscle contraction? What is passed through the t-tubules to allow for a muscle contraction? 5 Answers
Relevance
Sondra
1 decade ago
Favorite Answer
Calcium flows through t-tubules. In response to stimulation, calcium channels in t-tubules open and allow calcium to flow down it's electro-chemical gradient into the cell.

What is the function of the t-tubules in a muscle contraction? | Yahoo Answers
Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page. Trending News
Trip to frozen yogurt shop leaves Lovato fuming
Real-life tragedy behind surprise Oscar nominee
Least vaccinated counties include many Trump voters
Chick-fil-A is moving in on Popeyes' key chicken turf
Childlike Empress in fantasy film offered nude roles
One America News Network stays true to Trump
Another 'horrifying' public health issue plaguing the U.S.
As mask mandates end, 1 state bucks trend
Sikhs mourn FedEx shooting victims as questions linger
YouTube star recovering after rolling car in Wyo. 'Dirty secret' plagues women in retirement, expert warns
More trending news? Visit Yahoo Home
Promoted
the_man_60
the_man_60
asked in Science & Mathematics Biology · 1 decade ago
What is the function of the t-tubules in a muscle contraction? What is passed through the t-tubules to allow for a muscle contraction? 5 Answers
Relevance
Sondra
1 decade ago
Favorite Answer
Calcium flows through t-tubules. In response to stimulation, calcium channels in t-tubules open and allow calcium to flow down it's electro-chemical gradient into the cell.

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 T-tubule - Wikipedia
T-tubule
From Wikipedia, the free encyclopedia
(Redirected from T-tubules)
Jump to navigation Jump to search
Invagination of the plasma membrane of a muscle cell that extends inward from the cell surface around each myofibril; the ends of T-tubules make contact with the sarcoplasmic reticulum membrane
T-tubule
Skeletal muscle, with T-tubule labelled in zoomed in image. T-tubule structure and relationship to the sarcoplasmic reticulum in skeletal muscle
Details
Part of
Cell membrane of Skeletal muscle and cardiac muscle cells. Identifiers
Latin
tubulus transversus
TH
H2.00.05.2.01018, H2.00.05.2.02013
Anatomical terminology
T-tubules ( transverse tubules) are extensions of the cell membrane that penetrate into the centre of skeletal and cardiac muscle cells. With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potential into the cell, and also play an important role in regulating cellular calcium concentration. Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronising calcium release throughout the cell. T-tubule structure may be affected by disease, potentially contributing to heart failure and arrhythmias. Although these structures were first seen in 1897, research into T-tubule biology is ongoing. Contents
1 Structure
1.1 Regulators
2 Function
2.1 Excitation-contraction coupling
2.2 Calcium control
2.3 Detubulation
3 History
4 Clinical significance
5 See also
6 References
Structure
T-tubules are tubules formed from the same phospholipid bilayer as the surface membrane or sarcolemma of skeletal or cardiac muscle cells. They connect directly with the sarcolemma at one end before travelling deep within the cell, forming a network of tubules with sections running both perpendicular (transverse) to and parallel (axially) to the sarcolemma.

T-tubule - Wikipedia

T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 T-tubule - Wikipedia
T-tubule
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Invagination of the plasma membrane of a muscle cell that extends inward from the cell surface around each myofibril; the ends of T-tubules make contact with the sarcoplasmic reticulum membrane
T-tubule
Skeletal muscle, with T-tubule labelled in zoomed in image. T-tubule structure and relationship to the sarcoplasmic reticulum in skeletal muscle
Details
Part of
Cell membrane of skeletal muscle and cardiac muscle cells. Identifiers
Latin
tubulus transversus
TH
H2.00.05.2.01018, H2.00.05.2.02013
Anatomical terminology
T-tubules ( transverse tubules) are extensions of the cell membrane that penetrate into the centre of skeletal and cardiac muscle cells. With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potential into the cell, and also play an important role in regulating cellular calcium concentration. Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronising calcium release throughout the cell. T-tubule structure and function are affected beat-by-beat by cardiomyocyte contraction, as well as by diseases, potentially contributing to heart failure and arrhythmias. Although these structures were first seen in 1897, research into T-tubule biology is ongoing. Contents
1 Structure
1.1 Regulators
2 Function
2.1 Excitation-contraction coupling
2.2 Calcium control
2.3 Detubulation
3 History
4 Clinical significance
5 See also
6 References
Structure
T-tubules are tubules formed from the same phospholipid bilayer as the surface membrane or sarcolemma of skeletal or cardiac muscle cells. They connect directly with the sarcolemma at one end before travelling deep within the cell, forming a network of tubules with sections running both perpendicular (transverse) to and parallel (axially) to the sarcolemma.

T-tubule - Wikipedia

The Muscular System
 One of the three polypeptides (TnI) is an inhibitory subunit that binds to actin. Another (TnT) binds to tropomyosin and helps to position it on actin, while a third one (TnC) binds calcium ions. IV) The Sarcoplasmic Reticulum (SR) acts to regulate intracellular levels of ionic calcium in that it stores calcium and releases it on demand when the muscle fiber is stimulated to contract. The SR is the endoplasmic reticulum of the muscle cell and consists of interconnecting tubules that surround each of the myofibrils. The tubules run longitudinally along the myofibrils and some form perpendicular cross channels called terminal cisternae (end sacs) at the A-I junctions and they also occur in pairs. V) The T tubules or transverse tubules are elongated tubes formed at the A band-I band junction by the sarcolemma penetrating into the cell at this point. The lumen (inside of each T tubule) is continuous with the extracellular space. Each T tubule runs between the paired terminal cisternae of the SR forming triads (successive groupings of the three membranous structures of a Tubule between two terminal cisternae). The T tubules also encircle each sarcomere as they pass from one myofibril to the next. The T tubules can conduct impulses from the sarcolemma to each of the sarcomeres.

The Muscular System

One of the three polypeptides (TnI) is an inhibitory subunit that binds to actin. Another (TnT) binds to tropomyosin and helps to position it on actin, while a third one (TnC) binds calcium ions. IV) The Sarcoplasmic Reticulum (SR) acts to regulate intracellular levels of ionic calcium in that it stores calcium and releases it on demand when the muscle fiber is stimulated to contract. The SR is the endoplasmic reticulum of the muscle cell and consists of interconnecting tubules that surround each of the myofibrils. The tubules run longitudinally along the myofibrils and some form perpendicular cross channels called terminal cisternae (end sacs) at the A-I junctions and they also occur in pairs. V) The T tubules or transverse tubules are elongated tubes formed at the A band-I band junction by the sarcolemma penetrating into the cell at this point. The lumen (inside of each T tubule) is continuous with the extracellular space. Each T tubule runs between the paired terminal cisternae of the SR forming triads (successive groupings of the three membranous structures of a Tubule between two terminal cisternae). The T tubules also encircle each sarcomere as they pass from one myofibril to the next. The T tubules can conduct impulses from the sarcolemma to each of the sarcomeres.

Muscle Membrane, T Tubules, and Sarcoplasmic Reticulum | Neupsy Key Muscle Membrane, T Tubules, and Sarcoplasmic Reticulum
Muscle Membrane, T Tubules, and Sarcoplasmic Reticulum
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 Muscle Membrane, T Tubules, and Sarcoplasmic Reticulum | Neupsy Key
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Showing most revelant items. Click here or hit Enter for more. Muscle Membrane, T Tubules, and Sarcoplasmic Reticulum
T tubules are specialized invaginations of the sarcolemma, with which it is continuous at multiple points. T tubules run transverse to the muscle fibers themselves and the sarcolemma and encircle individual muscle fibrils. T tubules form deep invaginations into the sarcolemma. This provides not only more rapid dispersal of muscle membrane depolarization along the muscle fiber, but it allows for propagation along both the surface of the sarcolemma and into the muscle fiber, where it can interact with deep sarcoplasmic reticulum. T tubules interact directly with components of the sarcoplasmic reticulum, leading to Ca 2+ release into the sarcoplasm. They also harbor voltage-gated Ca 2+ channels, L-type Ca 2+ channels. These Ca 2+ channels do not contribute to depolarization or the muscle fiber action potential but, rather, act as voltage sensors of muscle membrane depolarization. The sarcoplasmic reticulum forms a network of tubules surrounding muscle fibrils inside the sarcolemma.

Muscle Membrane, T Tubules, and Sarcoplasmic Reticulum | Neupsy Key

Muscle Membrane, T Tubules, and Sarcoplasmic Reticulum
Muscle Membrane, T Tubules, and Sarcoplasmic Reticulum
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T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases | Skeletal Muscle | Full Text T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
Abstract
Introduction
T-tubule plasticity
Morphological aspects of triad biogenesis
Sarcoplasmic reticulum
Transverse tubule
Molecular mechanisms involved in T-tubule biogenesis and triad formation and maintenance
Table 1 Proteins implicated in triad organization, roles and associated human diseasesa
Caveolin 3
Amphiphysin 2 (BIN1)
Dysferlin
Mitsugumins
Junctophilins
Myotubularin
The RyR-DHPR complex
Conclusion
References
Acknowledgements
Author information
Affiliations
Corresponding author
Additional information
Competing interests
Authors' contributions
Authors’ original submitted files for images
Authors’ original file for figure 1
Authors’ original file for figure 2
Authors’ original file for figure 3
Authors’ original file for figure 4
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Keywords
 T-tubule plasticity
The T-tubule membrane possesses a high plasticity which provides the stability required during muscle contraction, and facilitates repair upon damage. In addition to its principal function in EC coupling, the plasticity of T-tubules confers to this system non-related EC functions. It has been reported that the treatment of isolated muscle fibers with glycerol efflux-influx or with other low molecular weight nonelectrolytes (such as sugars) physically affects T-tubules morphology. Such osmotic shock can convert the T-tubule network into many membrane-bound vacuoles, which can either remain interconnected by normal T-tubules, or become separated (Figure 2) [ 9, 10 ]. Surprisingly, this vacuolation which results in 5-15 fold increase in the relative volume of T-tubule system is reversed spontaneously [ 11, 12 ]. Moreover, this observation is specific to transverse tubule membranes, as no other intracellular membrane systems appear to be involved [ 12 ], probably due to the fact that their lumen connects to the extracellular space. Figure 2
Dynamics of T-tubule vacuolation produced by the efflux of glycerol. A single frog skeletal muscle fiber stained with a lipophilic fluorescence probe is shown. Shown are serial confocal microscopic images of the same fiber (a) 5 minutes, (b) 12 minutes and (c) 30 minutes after the fiber was transferred from a solution containing 110 mM glycerol to a solution without glycerol (reprinted from [ 10 ]; © 2001 with permission from Elsevier).

T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases | Skeletal Muscle | Full Text

T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
Abstract
Introduction
T-tubule plasticity
Morphological aspects of triad biogenesis
Sarcoplasmic reticulum
Transverse tubule
Molecular mechanisms involved in T-tubule biogenesis and triad formation and maintenance
Table 1 Proteins implicated in triad organization, roles and associated human diseasesa
Caveolin 3
Amphiphysin 2 (BIN1)
Dysferlin
Mitsugumins
Junctophilins
Myotubularin
The RyR-DHPR complex
Conclusion
References
Acknowledgements
Author information
Affiliations
Corresponding author
Additional information
Competing interests
Authors' contributions
Authors’ original submitted files for images
Authors’ original file for figure 1
Authors’ original file for figure 2
Authors’ original file for figure 3
Authors’ original file for figure 4
Rights and permissions
About this article
Cite this article
Share this article
Keywords

T-tubule plasticity
The T-tubule membrane possesses a high plasticity which provides the stability required during muscle contraction, and facilitates repair upon damage. In addition to its principal function in EC coupling, the plasticity of T-tubules confers to this system non-related EC functions. It has been reported that the treatment of isolated muscle fibers with glycerol efflux-influx or with other low molecular weight nonelectrolytes (such as sugars) physically affects T-tubules morphology. Such osmotic shock can convert the T-tubule network into many membrane-bound vacuoles, which can either remain interconnected by normal T-tubules, or become separated (Figure 2) [ 9, 10 ]. Surprisingly, this vacuolation which results in 5-15 fold increase in the relative volume of T-tubule system is reversed spontaneously [ 11, 12 ]. Moreover, this observation is specific to transverse tubule membranes, as no other intracellular membrane systems appear to be involved [ 12 ], probably due to the fact that their lumen connects to the extracellular space. Figure 2
Dynamics of T-tubule vacuolation produced by the efflux of glycerol. A single frog skeletal muscle fiber stained with a lipophilic fluorescence probe is shown. Shown are serial confocal microscopic images of the same fiber (a) 5 minutes, (b) 12 minutes and (c) 30 minutes after the fiber was transferred from a solution containing 110 mM glycerol to a solution without glycerol (reprinted from [ 10 ]; © 2001 with permission from Elsevier).

 The association of the T-tubule with a terminal cistern is known as a diad. [ 5]
In skeletal muscle cells, T-tubules are between 20 and 40 nm in diameter and are typically located either side of the myosin strip, at the junction of overlap between the A and I bands. T-tubules in skeletal muscle are associated with two terminal cisternae, known as a triad. [ 1][6]
Regulators[edit]
The shape of the T-tubule system is produced and maintained by a variety of proteins. The protein amphiphysin-2is encoded by the gene BIN1and is responsible for forming the structure of the T-tubule and ensuring that the appropriate proteins (in particular L-type calcium channels) are located within the T-tubule membrane.[7] Junctophilin-2 is encoded by the gene JPH2and helps to form a junction between the T-tubule membrane and the sarcoplasmic reticulum, vital for excitation-contraction coupling.[5] Titin capping protein or Telethonin is encoded by the gene TCAPand helps with T-tubule development and is potentially responsible for the increasing number of T-tubules seen as muscles grow. [ 5]
Function[edit]
Excitation-contraction coupling[edit]
See also: Excitation-contraction coupling
T-tubules are an important link in the chain from electrical excitation of a cell to its subsequent contraction (excitation-contraction coupling). When contraction of a muscle is needed, stimulation from a nerve or an adjacent muscle cell causes a characteristic flow of charged particlesacross the cell membrane known as an action potential. At rest, there are fewer positively charged particles on the inner side of the membrane compared to the outer side, and the membrane is described as being polarised. During an action potential, positively charged particles (predominantly sodium and calcium ions) flow across the membrane from the outside to the inside.

The association of the T-tubule with a terminal cistern is known as a diad. [ 5]
In skeletal muscle cells, T-tubules are between 20 and 40 nm in diameter and are typically located either side of the myosin strip, at the junction of overlap between the A and I bands. T-tubules in skeletal muscle are associated with two terminal cisternae, known as a triad. [ 1][6]
Regulators[edit]
The shape of the T-tubule system is produced and maintained by a variety of proteins. The protein amphiphysin-2is encoded by the gene BIN1and is responsible for forming the structure of the T-tubule and ensuring that the appropriate proteins (in particular L-type calcium channels) are located within the T-tubule membrane.[7] Junctophilin-2 is encoded by the gene JPH2and helps to form a junction between the T-tubule membrane and the sarcoplasmic reticulum, vital for excitation-contraction coupling.[5] Titin capping protein or Telethonin is encoded by the gene TCAPand helps with T-tubule development and is potentially responsible for the increasing number of T-tubules seen as muscles grow. [ 5]
Function[edit]
Excitation-contraction coupling[edit]
See also: Excitation-contraction coupling
T-tubules are an important link in the chain from electrical excitation of a cell to its subsequent contraction (excitation-contraction coupling). When contraction of a muscle is needed, stimulation from a nerve or an adjacent muscle cell causes a characteristic flow of charged particlesacross the cell membrane known as an action potential. At rest, there are fewer positively charged particles on the inner side of the membrane compared to the outer side, and the membrane is described as being polarised. During an action potential, positively charged particles (predominantly sodium and calcium ions) flow across the membrane from the outside to the inside.

Cardiac T-Tubule Microanatomy and Function | Physiological Reviews Cardiac T-Tubule Microanatomy and Function
Cardiac T-Tubule Microanatomy and Function
Abstract
I. INTRODUCTION
II. CARDIAC T-TUBULE STRUCTURE
A. History of T-Tubule Structure-Related Research
B. Gross Morphology and Geometry
C. Membrane Ultrastructure and Microdomains
1. cBIN1 microfolds: microdomains supporting LTCC-RyR dyads
2. Caveoli (caveolae): β-AR/LTCC signaling hubs
3. Ankyrin B microdomains: NCX/NKA/InsP 3 macromolecular complex
D. Peri-Membrane Cytoskeleton Scaffolds at Cardiac T-Tubules
1. Actin filaments, tropomyosin, and N-WASP
2. Costamere complex and t-tubule membrane-associated scaffolds
3. Myofilament structural proteins
E. Variation in Cardiac T-Tubule Geometry
III. TRANSMEMBRANE PROTEINS AT CARDIAC T-TUBULES
A. Ion Handling Proteins (Channels/Transporters/Pumps)
1. Ca 2+ handling proteins
2. Na + handling proteins
3. K + handling proteins
B. Signaling Molecules at Cardiac T-Tubules
IV. FUNCTION OF CARDIAC T-TUBULES
A. Dyad and EC Coupling
1. LTCC trafficking and clustering to dyads through BIN1
2. RyR recruitment to dyads through BIN1
3. Junctophilin-2 in t-tubule-jSR junctional membrane complex formation
B. Ion Diffusion and Membrane Excitability
C. Other Microdomain-Related Functions
V. LIFE CYCLE OF CARDIAC T-TUBULES
A. Membrane Biogenesis, Maintenance, and Turnover
B. Ion Channel Trafficking and Half-Life
VI. ALTERATION OF T-TUBULE STRUCTURE AND FUNCTION IN HEART FAILURE
VII. CONCLUSIONS
GRANTS
DISCLOSURES
Acknowledgments
 Lastly, we discuss the dynamic nature of t-tubules including membrane turnover, trafficking of transmembrane proteins, and the life cycles of membrane subdomains such as the cardiac BIN1-microdomain, as well as t-tubule remodeling and alteration in diseased hearts. Understanding cardiac t-tubule biology in normal and failing hearts is providing novel diagnostic and therapeutic opportunities to better treat patients with failing hearts. I. INTRODUCTION
Cardiac transverse tubules (t-tubules) are highly branched invaginations of cardiomyocyte sarcolemma that are rich in ion channels important for excitation-contraction (EC) coupling, maintenance of resting membrane potential, action potential initiation and regulation, and signaling transduction. Specific to striated muscle cells, t-tubules are invaginations of the sarcolemma, penetrating into the intracellular space of myocytes. These tubular invaginations form a complex network with transverse tubules that are interconnected within the cytoplasm by longitudinal tubules. The transverse tubules occur around myofilaments, anchoring to sarcomeric z-discs through costameres. The phospholipid-rich t-tubule lipid bilayers are shaped and maintained by membrane scaffolding proteins and intracellular cytoskeleton, as well as surrounding extracellular matrix. T-tubule membrane contains microdomains that compartmentalize transmembrane ion handling proteins and signaling molecules. Together, t-tubules are effective organelles that serve as a centralized signaling hub controlling cardiac contractile function and electrophysiology. The most recognized function of t-tubules is regulation of cardiac EC coupling by concentrating voltage-gated L-type calcium channels (LTCCs) and positioning them in close proximity to calcium sense and release channels, ryanodine receptors (RyRs), at the junctional membrane of sarcoplasmic reticulum (jSR).

Cardiac T-Tubule Microanatomy and Function | Physiological Reviews

Cardiac T-Tubule Microanatomy and Function
Cardiac T-Tubule Microanatomy and Function
Abstract
I. INTRODUCTION
II. CARDIAC T-TUBULE STRUCTURE
A. History of T-Tubule Structure-Related Research
B. Gross Morphology and Geometry
C. Membrane Ultrastructure and Microdomains
1. cBIN1 microfolds: microdomains supporting LTCC-RyR dyads
2. Caveoli (caveolae): β-AR/LTCC signaling hubs
3. Ankyrin B microdomains: NCX/NKA/InsP 3 macromolecular complex
D. Peri-Membrane Cytoskeleton Scaffolds at Cardiac T-Tubules
1. Actin filaments, tropomyosin, and N-WASP
2. Costamere complex and t-tubule membrane-associated scaffolds
3. Myofilament structural proteins
E. Variation in Cardiac T-Tubule Geometry
III. TRANSMEMBRANE PROTEINS AT CARDIAC T-TUBULES
A. Ion Handling Proteins (Channels/Transporters/Pumps)
1. Ca 2+ handling proteins
2. Na + handling proteins
3. K + handling proteins
B. Signaling Molecules at Cardiac T-Tubules
IV. FUNCTION OF CARDIAC T-TUBULES
A. Dyad and EC Coupling
1. LTCC trafficking and clustering to dyads through BIN1
2. RyR recruitment to dyads through BIN1
3. Junctophilin-2 in t-tubule-jSR junctional membrane complex formation
B. Ion Diffusion and Membrane Excitability
C. Other Microdomain-Related Functions
V. LIFE CYCLE OF CARDIAC T-TUBULES
A. Membrane Biogenesis, Maintenance, and Turnover
B. Ion Channel Trafficking and Half-Life
VI. ALTERATION OF T-TUBULE STRUCTURE AND FUNCTION IN HEART FAILURE
VII. CONCLUSIONS
GRANTS
DISCLOSURES
Acknowledgments

T-tubule | Psychology Wiki | Fandom T-tubule
T-tubule
Contents
Structure
Excitation-contraction coupling
Detubulation
See also
External links
 T-tubule | Psychology Wiki | Fandom
T-tubule
T-tubule
[ [Image:|190px|center|]]

Latin
tubulus transversus
Gray's
subject #
System

MeSH
[1]
[ [Image:|190px|center|]]

A T-tubule (or transverse tubule) is a deep invagination of the sarcolemma, which is the plasma membrane, only found in skeletal and cardiac muscle cells. These invaginations allow depolarization of the membrane to quickly penetrate to the interior of the cell. Contents
1
Structure
2
Excitation-contraction coupling
3
Detubulation
4
See also
5
External links
Structure
Each muscle fiber is surrounded by a sarcolemma (the muscle fiber's plasma membrane) which invaginates perpendicular to the length of the fiber to form what is called a T-tubule. At these invaginations the sarcolemma is studded with a large number of L-type calcium channels. In skeletal muscle cells specifically, T-tubule invaginations are typically located at the junction overlap between the A and I bands of the sarcomere, and together with a pair of terminal cisternae (bulbous enlarged areas of the sarcoplasmic reticulum) it forms an arrangement called a triad. Cardiac muscle has a similar structure; instead of a triad there is a diad, which is composed of a T-tubule and a single terminal cisterna, and it occurs at the Z line. It is physiologically important for excitation-contraction coupling (see section below) that the T-tubules are positioned close to the terminal cisternae of the sarcoplasmic reticulum as the triad or diad arrangement allows physical and functional contact by voltage dependent L-type calcium channels. So, an action potential along the sarcolemma causes calcium channels to open in the terminal cisternae / sarcoplasmic reticulum which enables calcium to move from the sarcoplasmic reticulum into cytoplasm and the intracellular calcium concentration to increase. Excitation-contraction coupling
See Excitation-contraction coupling
T-tubules are the major sites for the coupling of excitation and contraction, which is the process whereby the spreading depolarization is converted into force production by muscle fibers.

T-tubule | Psychology Wiki | Fandom

T-tubule
T-tubule
Contents
Structure
Excitation-contraction coupling
Detubulation
See also
External links

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronising calcium release throughout the cell. T-tubule structure and function are affected beat-by-beat by cardiomyocyte contraction, as well as by diseases, potentially contributing to heart failure and arrhythmias. Although these structures were first seen in 1897, research into T-tubule biology is ongoing. Contents
1 Structure
1.1 Regulators
2 Function
2.1 Excitation-contraction coupling
2.2 Calcium control
2.3 Detubulation
3 History
4 Clinical significance
5 See also
6 References
Structure
T-tubules are tubules formed from the same phospholipid bilayer as the surface membrane or sarcolemma of skeletal or cardiac muscle cells. They connect directly with the sarcolemma at one end before travelling deep within the cell, forming a network of tubules with sections running both perpendicular (transverse) to and parallel (axially) to the sarcolemma. Due to this complex orientation, some refer to T-tubules as the transverse-axial tubular system. The inside or lumen of the T-tubule is open at the cell surface, meaning that the T-tubule is filled with fluid containing the same constituents as the solution that surrounds the cell (the extracellular fluid). Rather than being just a passive connecting tube, the membrane that forms T-tubules is highly active, being studded with proteins including L-type calcium channels, sodium-calcium exchangers, calcium ATPases and Beta adrenoceptors. T-tubules are found in both atrial and ventricular cardiac muscle cells ( cardiomyocytes ), in which they develop in the first few weeks of life. They are found in ventricular muscle cells in most species, and in atrial muscle cells from large mammals.

T-tubule - Wikipedia

Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronising calcium release throughout the cell. T-tubule structure and function are affected beat-by-beat by cardiomyocyte contraction, as well as by diseases, potentially contributing to heart failure and arrhythmias. Although these structures were first seen in 1897, research into T-tubule biology is ongoing. Contents
1 Structure
1.1 Regulators
2 Function
2.1 Excitation-contraction coupling
2.2 Calcium control
2.3 Detubulation
3 History
4 Clinical significance
5 See also
6 References
Structure
T-tubules are tubules formed from the same phospholipid bilayer as the surface membrane or sarcolemma of skeletal or cardiac muscle cells. They connect directly with the sarcolemma at one end before travelling deep within the cell, forming a network of tubules with sections running both perpendicular (transverse) to and parallel (axially) to the sarcolemma. Due to this complex orientation, some refer to T-tubules as the transverse-axial tubular system. The inside or lumen of the T-tubule is open at the cell surface, meaning that the T-tubule is filled with fluid containing the same constituents as the solution that surrounds the cell (the extracellular fluid). Rather than being just a passive connecting tube, the membrane that forms T-tubules is highly active, being studded with proteins including L-type calcium channels, sodium-calcium exchangers, calcium ATPases and Beta adrenoceptors. T-tubules are found in both atrial and ventricular cardiac muscle cells ( cardiomyocytes ), in which they develop in the first few weeks of life. They are found in ventricular muscle cells in most species, and in atrial muscle cells from large mammals.

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronising calcium release throughout the cell. T-tubule structure may be affected by disease, potentially contributing to heart failure and arrhythmias. Although these structures were first seen in 1897, research into T-tubule biology is ongoing. Contents
1 Structure
1.1 Regulators
2 Function
2.1 Excitation-contraction coupling
2.2 Calcium control
2.3 Detubulation
3 History
4 Clinical significance
5 See also
6 References
Structure
T-tubules are tubules formed from the same phospholipid bilayer as the surface membrane or sarcolemma of skeletal or cardiac muscle cells. They connect directly with the sarcolemma at one end before travelling deep within the cell, forming a network of tubules with sections running both perpendicular (transverse) to and parallel (axially) to the sarcolemma. Due to this complex orientation, some refer to T-tubules as the transverse-axial tubular system. The inside or lumen of the T-tubule is open at the cell surface, meaning that the T-tubule is filled with fluid containing the same constituents as the solution that surrounds the cell (the extracellular fluid). Rather than being just a passive connecting tube, the membrane that forms T-tubules is highly active, being studded with proteins including L-type calcium channels, sodium-calcium exchangers, calcium ATPases and Beta adrenoceptors. T-tubules are found in both atrial and ventricular cardiac muscle cells ( cardiomyocytes ), in which they develop in the first few weeks of life. They are found in ventricular muscle cells in most species, and in atrial muscle cells from large mammals.

T-tubule - Wikipedia

Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronising calcium release throughout the cell. T-tubule structure may be affected by disease, potentially contributing to heart failure and arrhythmias. Although these structures were first seen in 1897, research into T-tubule biology is ongoing. Contents
1 Structure
1.1 Regulators
2 Function
2.1 Excitation-contraction coupling
2.2 Calcium control
2.3 Detubulation
3 History
4 Clinical significance
5 See also
6 References
Structure
T-tubules are tubules formed from the same phospholipid bilayer as the surface membrane or sarcolemma of skeletal or cardiac muscle cells. They connect directly with the sarcolemma at one end before travelling deep within the cell, forming a network of tubules with sections running both perpendicular (transverse) to and parallel (axially) to the sarcolemma. Due to this complex orientation, some refer to T-tubules as the transverse-axial tubular system. The inside or lumen of the T-tubule is open at the cell surface, meaning that the T-tubule is filled with fluid containing the same constituents as the solution that surrounds the cell (the extracellular fluid). Rather than being just a passive connecting tube, the membrane that forms T-tubules is highly active, being studded with proteins including L-type calcium channels, sodium-calcium exchangers, calcium ATPases and Beta adrenoceptors. T-tubules are found in both atrial and ventricular cardiac muscle cells ( cardiomyocytes ), in which they develop in the first few weeks of life. They are found in ventricular muscle cells in most species, and in atrial muscle cells from large mammals.

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 As T-tubules bring the sarcolemma very close to the sarcoplasmic reticulum at all regions throughout the cell, calcium can then be released from the sarcoplasmic reticulum across the whole cell at the same time. This synchronisation of calcium release allows muscle cells to contract more forcefully. In cells lacking T-tubules such as smooth muscle cells, diseased cardiomyocytes, or muscle cells in which T-tubules have been artificially removed, the calcium that enters at the sarcolemma has to diffuse gradually throughout the cell, activating the ryanodine receptors much more slowly as a wave of calcium leading to less forceful contraction. As the T-tubules are the primary location for excitation-contraction coupling, the ion channels and proteins involved in this process are concentrated here - there are 3 times as many L-type calcium channels located within the T-tubule membrane compared to the rest of the sarcolemma. Furthermore, beta adrenoceptors are also highly concentrated in the T-tubular membrane, and their stimulation increases calcium release from the sarcoplasmic reticulum. Calcium control
As the space within the lumen of the T-tubule is continuous with the space that surrounds the cell (the extracellular space), ion concentrations between the two are very similar. However, due to the importance of the ions within the T-tubules (particularly calcium in cardiac muscle), it is very important that these concentrations remain relatively constant. As the T-tubules are very thin, they essentially trap the ions. This is important as, regardless of the ion concentrations elsewhere in the cell, T-tubules still have enough calcium ions to permit muscle contraction. Therefore, even if the concentration of calcium outside the cell falls ( hypocalcaemia ), the concentration of calcium within the T-tubule remains relatively constant, allowing cardiac contraction to continue.

T-tubule - Wikipedia

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 Regulators
The shape of the T-tubule system is produced and maintained by a variety of proteins. The protein amphiphysin-2 is encoded by the gene BIN1 and is responsible for forming the structure of the T-tubule and ensuring that the appropriate proteins (in particular L-type calcium channels) are located within the T-tubule membrane. Junctophilin-2 is encoded by the gene JPH2 and helps to form a junction between the T-tubule membrane and the sarcoplasmic reticulum, vital for excitation-contraction coupling. Titin capping protein known as telethonin is encoded by the TCAP gene and helps with T-tubule development and is potentially responsible for the increasing number of T-tubules seen as muscles grow. Function
Excitation-contraction coupling
See also: Excitation-contraction coupling
T-tubules are an important link in the chain from electrical excitation of a cell to its subsequent contraction (excitation-contraction coupling). When contraction of a muscle is needed, stimulation from a nerve or an adjacent muscle cell causes a characteristic flow of charged particles across the cell membrane known as an action potential. At rest, there are fewer positively charged particles on the inner side of the membrane compared to the outer side, and the membrane is described as being polarised. During an action potential, positively charged particles (predominantly sodium and calcium ions) flow across the membrane from the outside to the inside. This reverses the normal imbalance of charged particles and is referred to as depolarisation.

T-tubule - Wikipedia

Regulators
The shape of the T-tubule system is produced and maintained by a variety of proteins. The protein amphiphysin-2 is encoded by the gene BIN1 and is responsible for forming the structure of the T-tubule and ensuring that the appropriate proteins (in particular L-type calcium channels) are located within the T-tubule membrane. Junctophilin-2 is encoded by the gene JPH2 and helps to form a junction between the T-tubule membrane and the sarcoplasmic reticulum, vital for excitation-contraction coupling. Titin capping protein known as telethonin is encoded by the TCAP gene and helps with T-tubule development and is potentially responsible for the increasing number of T-tubules seen as muscles grow. Function
Excitation-contraction coupling
See also: Excitation-contraction coupling
T-tubules are an important link in the chain from electrical excitation of a cell to its subsequent contraction (excitation-contraction coupling). When contraction of a muscle is needed, stimulation from a nerve or an adjacent muscle cell causes a characteristic flow of charged particles across the cell membrane known as an action potential. At rest, there are fewer positively charged particles on the inner side of the membrane compared to the outer side, and the membrane is described as being polarised. During an action potential, positively charged particles (predominantly sodium and calcium ions) flow across the membrane from the outside to the inside. This reverses the normal imbalance of charged particles and is referred to as depolarisation.

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 Regulators
The shape of the T-tubule system is produced and maintained by a variety of proteins. The protein amphiphysin-2 is encoded by the gene BIN1 and is responsible for forming the structure of the T-tubule and ensuring that the appropriate proteins (in particular L-type calcium channels) are located within the T-tubule membrane. Junctophilin-2 is encoded by the gene JPH2 and helps to form a junction between the T-tubule membrane and the sarcoplasmic reticulum, vital for excitation-contraction coupling. Titin capping protein or Telethonin is encoded by the gene TCAP and helps with T-tubule development and is potentially responsible for the increasing number of T-tubules seen as muscles grow. Function
Excitation-contraction coupling
See also: Excitation-contraction coupling
T-tubules are an important link in the chain from electrical excitation of a cell to its subsequent contraction (excitation-contraction coupling). When contraction of a muscle is needed, stimulation from a nerve or an adjacent muscle cell causes a characteristic flow of charged particles across the cell membrane known as an action potential. At rest, there are fewer positively charged particles on the inner side of the membrane compared to the outer side, and the membrane is described as being polarised. During an action potential, positively charged particles (predominantly sodium and calcium ions) flow across the membrane from the outside to the inside. This reverses the normal imbalance of charged particles and is referred to as depolarisation.

T-tubule - Wikipedia

Regulators
The shape of the T-tubule system is produced and maintained by a variety of proteins. The protein amphiphysin-2 is encoded by the gene BIN1 and is responsible for forming the structure of the T-tubule and ensuring that the appropriate proteins (in particular L-type calcium channels) are located within the T-tubule membrane. Junctophilin-2 is encoded by the gene JPH2 and helps to form a junction between the T-tubule membrane and the sarcoplasmic reticulum, vital for excitation-contraction coupling. Titin capping protein or Telethonin is encoded by the gene TCAP and helps with T-tubule development and is potentially responsible for the increasing number of T-tubules seen as muscles grow. Function
Excitation-contraction coupling
See also: Excitation-contraction coupling
T-tubules are an important link in the chain from electrical excitation of a cell to its subsequent contraction (excitation-contraction coupling). When contraction of a muscle is needed, stimulation from a nerve or an adjacent muscle cell causes a characteristic flow of charged particles across the cell membrane known as an action potential. At rest, there are fewer positively charged particles on the inner side of the membrane compared to the outer side, and the membrane is described as being polarised. During an action potential, positively charged particles (predominantly sodium and calcium ions) flow across the membrane from the outside to the inside. This reverses the normal imbalance of charged particles and is referred to as depolarisation.

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 In cardiac muscle cells, T-tubules are between 20 and 450 nanometers in diameter and are usually located in regions called Z-discs where the actin filaments anchor within the cell. T-tubules within the heart are closely associated with the intracellular calcium store known as the sarcoplasmic reticulum in specific regions referred to as terminal cisternae. The association of the T-tubule with a terminal cistern is known as a diad. In skeletal muscle cells, T-tubules are between 20 and 40 nm in diameter and are typically located either side of the myosin strip, at the junction of overlap between the A and I bands. T-tubules in skeletal muscle are associated with two terminal cisternae, known as a triad. Regulators
The shape of the T-tubule system is produced and maintained by a variety of proteins. The protein amphiphysin-2 is encoded by the gene BIN1 and is responsible for forming the structure of the T-tubule and ensuring that the appropriate proteins (in particular L-type calcium channels) are located within the T-tubule membrane. Junctophilin-2 is encoded by the gene JPH2 and helps to form a junction between the T-tubule membrane and the sarcoplasmic reticulum, vital for excitation-contraction coupling. Titin capping protein known as telethonin is encoded by the TCAP gene and helps with T-tubule development and is potentially responsible for the increasing number of T-tubules seen as muscles grow. Function
Excitation-contraction coupling
See also:

T-tubule - Wikipedia

In cardiac muscle cells, T-tubules are between 20 and 450 nanometers in diameter and are usually located in regions called Z-discs where the actin filaments anchor within the cell. T-tubules within the heart are closely associated with the intracellular calcium store known as the sarcoplasmic reticulum in specific regions referred to as terminal cisternae. The association of the T-tubule with a terminal cistern is known as a diad. In skeletal muscle cells, T-tubules are between 20 and 40 nm in diameter and are typically located either side of the myosin strip, at the junction of overlap between the A and I bands. T-tubules in skeletal muscle are associated with two terminal cisternae, known as a triad. Regulators
The shape of the T-tubule system is produced and maintained by a variety of proteins. The protein amphiphysin-2 is encoded by the gene BIN1 and is responsible for forming the structure of the T-tubule and ensuring that the appropriate proteins (in particular L-type calcium channels) are located within the T-tubule membrane. Junctophilin-2 is encoded by the gene JPH2 and helps to form a junction between the T-tubule membrane and the sarcoplasmic reticulum, vital for excitation-contraction coupling. Titin capping protein known as telethonin is encoded by the TCAP gene and helps with T-tubule development and is potentially responsible for the increasing number of T-tubules seen as muscles grow. Function
Excitation-contraction coupling
See also:

T-Tubule Function in Mammalian Cardiac Myocytes | Circulation Research T-Tubule Function in Mammalian Cardiac Myocytes
T-Tubule Function in Mammalian Cardiac Myocytes
Abstract
Occurrence and Morphology of the T-Tubules
T-Tubule Development Is Labile
Proteins Present in the T-Tubule Membrane
Ca2+-Handling Proteins
Na+-Handling Proteins
K+-Handling Proteins
Anion-Handling Proteins
Second-Messenger Pathways
Interpretation of Immunohistochemical Data
Protein Colocalization Within, and With Proteins Adjacent to, the T-Tubules
Localization of Function
Cells Lacking T-Tubules
Diffusion Studies
Scanning Pipette
Detubulation
Functional Role
Electrical Properties of T-Tubules
Coupling of Ca 2+ Entry and Ca 2+ Release
Ca 2+ Efflux
Signal Transduction
Changes During Development and Disease
T-Tubule Development and Morphology in Hypertrophy and Failure
Changes in Protein Expression in Development, Hypertrophy, and Failure
Relevance of Changes in T-Tubule Structure and Protein Expression to Function
Conclusions and Unanswered Questions
Footnotes
References
 T-Tubule Function in Mammalian Cardiac Myocytes | Circulation Research
Home Circulation Research Vol. 92, No. 11 T-Tubule Function in Mammalian Cardiac Myocytes
T-Tubule Function in Mammalian Cardiac Myocytes
Fabien Brette
and
Clive Orchard
Fabien Brette
Fabien Brette From the School of Biomedical Sciences, University of Leeds, Leeds, UK. Search for more papers by this author
and
Clive Orchard
Clive Orchard From the School of Biomedical Sciences, University of Leeds, Leeds, UK. Search for more papers by this author
Originally published 13 Jun 2003 https://doi.org/10.1161/01.RES.0000074908.17214.FD Circulation Research. 2003;92:1182–1192
Abstract
The transverse tubules (t-tubules) of mammalian cardiac ventricular myocytes are invaginations of the surface membrane. Recent studies have suggested that the structure and function of the t-tubules are more complex than previously believed; in particular, many of the proteins involved in cellular Ca 2+ cycling appear to be concentrated at the t-tubule. Thus, the t-tubules are an important determinant of cardiac cell function, especially as the main site of excitation-contraction coupling, ensuring spatially and temporally synchronous Ca 2+ release throughout the cell. Changes in t-tubule structure and protein expression occur during development and in heart failure, so that changes in the t-tubules may contribute to the functional changes observed in these conditions.

T-Tubule Function in Mammalian Cardiac Myocytes | Circulation Research
Home Circulation Research Vol. 92, No. 11 T-Tubule Function in Mammalian Cardiac Myocytes
T-Tubule Function in Mammalian Cardiac Myocytes
Fabien Brette
and
Clive Orchard
Fabien Brette
Fabien Brette From the School of Biomedical Sciences, University of Leeds, Leeds, UK. Search for more papers by this author
and
Clive Orchard
Clive Orchard From the School of Biomedical Sciences, University of Leeds, Leeds, UK. Search for more papers by this author
Originally published 13 Jun 2003 https://doi.org/10.1161/01.RES.0000074908.17214.FD Circulation Research. 2003;92:1182–1192
Abstract
The transverse tubules (t-tubules) of mammalian cardiac ventricular myocytes are invaginations of the surface membrane. Recent studies have suggested that the structure and function of the t-tubules are more complex than previously believed; in particular, many of the proteins involved in cellular Ca 2+ cycling appear to be concentrated at the t-tubule. Thus, the t-tubules are an important determinant of cardiac cell function, especially as the main site of excitation-contraction coupling, ensuring spatially and temporally synchronous Ca 2+ release throughout the cell. Changes in t-tubule structure and protein expression occur during development and in heart failure, so that changes in the t-tubules may contribute to the functional changes observed in these conditions.

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 Due to this complex orientation, some refer to T-tubules as the transverse-axial tubular system. The inside or lumen of the T-tubule is open at the cell surface, meaning that the T-tubule is filled with fluid containing the same constituents as the solution that surrounds the cell (the extracellular fluid). Rather than being just a passive connecting tube, the membrane that forms T-tubules is highly active, being studded with proteins including L-type calcium channels, sodium-calcium exchangers, calcium ATPases and Beta adrenoceptors. T-tubules are found in both atrial and ventricular cardiac muscle cells ( cardiomyocytes ), in which they develop in the first few weeks of life. They are found in ventricular muscle cells in most species, and in atrial muscle cells from large mammals. In cardiac muscle cells, T-tubules are between 20 and 450 nanometers in diameter and are usually located in regions called Z-discs where the actin filaments anchor within the cell. T-tubules within the heart are closely associated with the intracellular calcium store known as the sarcoplasmic reticulum in specific regions referred to as terminal cisternae. The association of the T-tubule with a terminal cistern is known as a diad. In skeletal muscle cells, T-tubules are between 20 and 40 nm in diameter and are typically located either side of the myosin strip, at the junction of overlap between the A and I bands. T-tubules in skeletal muscle are associated with two terminal cisternae, known as a triad.

T-tubule - Wikipedia

Due to this complex orientation, some refer to T-tubules as the transverse-axial tubular system. The inside or lumen of the T-tubule is open at the cell surface, meaning that the T-tubule is filled with fluid containing the same constituents as the solution that surrounds the cell (the extracellular fluid). Rather than being just a passive connecting tube, the membrane that forms T-tubules is highly active, being studded with proteins including L-type calcium channels, sodium-calcium exchangers, calcium ATPases and Beta adrenoceptors. T-tubules are found in both atrial and ventricular cardiac muscle cells ( cardiomyocytes ), in which they develop in the first few weeks of life. They are found in ventricular muscle cells in most species, and in atrial muscle cells from large mammals. In cardiac muscle cells, T-tubules are between 20 and 450 nanometers in diameter and are usually located in regions called Z-discs where the actin filaments anchor within the cell. T-tubules within the heart are closely associated with the intracellular calcium store known as the sarcoplasmic reticulum in specific regions referred to as terminal cisternae. The association of the T-tubule with a terminal cistern is known as a diad. In skeletal muscle cells, T-tubules are between 20 and 40 nm in diameter and are typically located either side of the myosin strip, at the junction of overlap between the A and I bands. T-tubules in skeletal muscle are associated with two terminal cisternae, known as a triad.

T-tubule - Wikipedia

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 As well as T-tubules being a site for calcium entry into the cell, they are also a site for calcium removal. This is important as it means that calcium levels within the cell can be tightly controlled in a small area (i.e. between the T-tubule and sarcoplasmic reticulum, known as local control). Proteins such as the sodium-calcium exchanger and the sarcolemmal ATPase are located mainly in the T-tubule membrane. The sodium-calcium exchanger passively removes one calcium ion from the cell in exchange for three sodium ions. As a passive process it can therefore allow calcium to flow into or out of the cell depending on the combination of the relative concentrations of these ions and the voltage across the cell membrane (the electrochemical gradient ). The calcium ATPase removes calcium from the cell actively, using energy derived from adenosine triphosphate (ATP). Detubulation
In order to study T-tubule function, T-tubules can be artificially uncoupled from the surface membrane using a technique known as detubulation. Chemicals such as glycerol or formamide (for skeletal and cardiac muscle respectively) can be added to the extracellular solution that surrounds the cells. These agents increase the osmolarity of the extracellular solution, causing the cells to shrink. When these agents are withdrawn, the cells rapidly expand and return to their normal size.

T-tubule - Wikipedia

As well as T-tubules being a site for calcium entry into the cell, they are also a site for calcium removal. This is important as it means that calcium levels within the cell can be tightly controlled in a small area (i.e. between the T-tubule and sarcoplasmic reticulum, known as local control). Proteins such as the sodium-calcium exchanger and the sarcolemmal ATPase are located mainly in the T-tubule membrane. The sodium-calcium exchanger passively removes one calcium ion from the cell in exchange for three sodium ions. As a passive process it can therefore allow calcium to flow into or out of the cell depending on the combination of the relative concentrations of these ions and the voltage across the cell membrane (the electrochemical gradient ). The calcium ATPase removes calcium from the cell actively, using energy derived from adenosine triphosphate (ATP). Detubulation
In order to study T-tubule function, T-tubules can be artificially uncoupled from the surface membrane using a technique known as detubulation. Chemicals such as glycerol or formamide (for skeletal and cardiac muscle respectively) can be added to the extracellular solution that surrounds the cells. These agents increase the osmolarity of the extracellular solution, causing the cells to shrink. When these agents are withdrawn, the cells rapidly expand and return to their normal size.

T-tubule - Wikipedia

 5]
Function[edit]
Excitation-contraction coupling[edit]
See also: Excitation-contraction coupling
T-tubules are an important link in the chain from electrical excitation of a cell to its subsequent contraction (excitation-contraction coupling). When contraction of a muscle is needed, stimulation from a nerve or an adjacent muscle cell causes a characteristic flow of charged particlesacross the cell membrane known as an action potential. At rest, there are fewer positively charged particles on the inner side of the membrane compared to the outer side, and the membrane is described as being polarised. During an action potential, positively charged particles (predominantly sodium and calcium ions) flow across the membrane from the outside to the inside. This reverses the normal imbalance of charged particles and is referred to as depolarisation. One region of membrane depolarises adjacent regions, and the resulting wave of depolarisation then spreads along the cell membrane.[8] The polarisation of the membrane is restored as potassium ions flow back across the membrane from the inside to the outside of the cell. In cardiac muscle cells, as the action potential passes down the T-tubules it activates L-type calcium channels in the T-tubular membrane. Activation of the L-type calcium channel  allows calcium to pass into the cell. T-tubules contain a higher concentration of L-type calcium channels than the rest of the sarcolemma and therefore the majority of the calcium that enters the cell occurs via T-tubules.[9] This calcium binds to and activates a receptor, known as a ryanodine receptor, located on the cell's own internal calcium store, the sarcoplasmic reticulum.

5]
Function[edit]
Excitation-contraction coupling[edit]
See also: Excitation-contraction coupling
T-tubules are an important link in the chain from electrical excitation of a cell to its subsequent contraction (excitation-contraction coupling). When contraction of a muscle is needed, stimulation from a nerve or an adjacent muscle cell causes a characteristic flow of charged particlesacross the cell membrane known as an action potential. At rest, there are fewer positively charged particles on the inner side of the membrane compared to the outer side, and the membrane is described as being polarised. During an action potential, positively charged particles (predominantly sodium and calcium ions) flow across the membrane from the outside to the inside. This reverses the normal imbalance of charged particles and is referred to as depolarisation. One region of membrane depolarises adjacent regions, and the resulting wave of depolarisation then spreads along the cell membrane.[8] The polarisation of the membrane is restored as potassium ions flow back across the membrane from the inside to the outside of the cell. In cardiac muscle cells, as the action potential passes down the T-tubules it activates L-type calcium channels in the T-tubular membrane. Activation of the L-type calcium channel  allows calcium to pass into the cell. T-tubules contain a higher concentration of L-type calcium channels than the rest of the sarcolemma and therefore the majority of the calcium that enters the cell occurs via T-tubules.[9] This calcium binds to and activates a receptor, known as a ryanodine receptor, located on the cell's own internal calcium store, the sarcoplasmic reticulum.

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 Excitation-contraction coupling
T-tubules are an important link in the chain from electrical excitation of a cell to its subsequent contraction (excitation-contraction coupling). When contraction of a muscle is needed, stimulation from a nerve or an adjacent muscle cell causes a characteristic flow of charged particles across the cell membrane known as an action potential. At rest, there are fewer positively charged particles on the inner side of the membrane compared to the outer side, and the membrane is described as being polarised. During an action potential, positively charged particles (predominantly sodium and calcium ions) flow across the membrane from the outside to the inside. This reverses the normal imbalance of charged particles and is referred to as depolarisation. One region of membrane depolarises adjacent regions, and the resulting wave of depolarisation then spreads along the cell membrane. The polarisation of the membrane is restored as potassium ions flow back across the membrane from the inside to the outside of the cell. In cardiac muscle cells, as the action potential passes down the T-tubules it activates L-type calcium channels in the T-tubular membrane. Activation of the L-type calcium channel allows calcium to pass into the cell. T-tubules contain a higher concentration of L-type calcium channels than the rest of the sarcolemma and therefore the majority of the calcium that enters the cell occurs via T-tubules.

T-tubule - Wikipedia

Excitation-contraction coupling
T-tubules are an important link in the chain from electrical excitation of a cell to its subsequent contraction (excitation-contraction coupling). When contraction of a muscle is needed, stimulation from a nerve or an adjacent muscle cell causes a characteristic flow of charged particles across the cell membrane known as an action potential. At rest, there are fewer positively charged particles on the inner side of the membrane compared to the outer side, and the membrane is described as being polarised. During an action potential, positively charged particles (predominantly sodium and calcium ions) flow across the membrane from the outside to the inside. This reverses the normal imbalance of charged particles and is referred to as depolarisation. One region of membrane depolarises adjacent regions, and the resulting wave of depolarisation then spreads along the cell membrane. The polarisation of the membrane is restored as potassium ions flow back across the membrane from the inside to the outside of the cell. In cardiac muscle cells, as the action potential passes down the T-tubules it activates L-type calcium channels in the T-tubular membrane. Activation of the L-type calcium channel allows calcium to pass into the cell. T-tubules contain a higher concentration of L-type calcium channels than the rest of the sarcolemma and therefore the majority of the calcium that enters the cell occurs via T-tubules.

T-tubule - Wikipedia

T-tubule | Psychology Wiki | Fandom T-tubule
T-tubule
Contents
Structure
Excitation-contraction coupling
Detubulation
See also
External links
 The L-type calcium channels in T-tubules activate in response to electrical stimulation; their opening allows calcium to flow down its electrochemical gradient and into the cell. Activation of the L-type channel also causes a mechanical interaction between it and calcium-release channels located on the adjacent sarcoplasmic reticulum membrane. In skeletal muscle, the influx of calcium through the L-type calcium channel on the T-tubule contributes little to excitation-contraction coupling, whereas it is crucial to the proper function of cardiac muscle ( see Cardiac action potential ). Conversely, the mechanical interaction between the T-tubule's L-type calcium channel and the calcium-release channel is critical to proper skeletal muscle contraction, whereas it contributes little to the contraction of cardiac muscle. Detubulation
It is possible to physically and functionally uncouple T-tubules from the surface membrane using a technique known as detubulation. This relies on osmotically active chemicals, such as glycerol (for skeletal muscle) or formamide (mainly for cardiac muscle ). Addition of these chemicals to the solution surrounding muscle cells causes the cells to shrink; when the chemical is withdrawn the cells rapidly expand before returning to their normal size. The rapid expansion is thought to cause the t-tubules to detach from the surface membrane, which reseals, and to reseal within the cell.

T-tubule | Psychology Wiki | Fandom

The L-type calcium channels in T-tubules activate in response to electrical stimulation; their opening allows calcium to flow down its electrochemical gradient and into the cell. Activation of the L-type channel also causes a mechanical interaction between it and calcium-release channels located on the adjacent sarcoplasmic reticulum membrane. In skeletal muscle, the influx of calcium through the L-type calcium channel on the T-tubule contributes little to excitation-contraction coupling, whereas it is crucial to the proper function of cardiac muscle ( see Cardiac action potential ). Conversely, the mechanical interaction between the T-tubule's L-type calcium channel and the calcium-release channel is critical to proper skeletal muscle contraction, whereas it contributes little to the contraction of cardiac muscle. Detubulation
It is possible to physically and functionally uncouple T-tubules from the surface membrane using a technique known as detubulation. This relies on osmotically active chemicals, such as glycerol (for skeletal muscle) or formamide (mainly for cardiac muscle ). Addition of these chemicals to the solution surrounding muscle cells causes the cells to shrink; when the chemical is withdrawn the cells rapidly expand before returning to their normal size. The rapid expansion is thought to cause the t-tubules to detach from the surface membrane, which reseals, and to reseal within the cell.

T-tubule plasticity
The T-tubule membrane possesses a high plasticity which provides the stability required during muscle contraction, and facilitates repair upon damage. In addition to its principal function in EC coupling, the plasticity of T-tubules confers to this system non-related EC functions. It has been reported that the treatment of isolated muscle fibers with glycerol efflux-influx or with other low molecular weight nonelectrolytes (such as sugars) physically affects T-tubules morphology. Such osmotic shock can convert the T-tubule network into many membrane-bound vacuoles, which can either remain interconnected by normal T-tubules, or become separated (Figure 2) [ 9, 10 ]. Surprisingly, this vacuolation which results in 5-15 fold increase in the relative volume of T-tubule system is reversed spontaneously [ 11, 12 ]. Moreover, this observation is specific to transverse tubule membranes, as no other intracellular membrane systems appear to be involved [ 12 ], probably due to the fact that their lumen connects to the extracellular space. Figure 2
Dynamics of T-tubule vacuolation produced by the efflux of glycerol. A single frog skeletal muscle fiber stained with a lipophilic fluorescence probe is shown. Shown are serial confocal microscopic images of the same fiber (a) 5 minutes, (b) 12 minutes and (c) 30 minutes after the fiber was transferred from a solution containing 110 mM glycerol to a solution without glycerol (reprinted from [ 10 ]; © 2001 with permission from Elsevier).

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 One region of membrane depolarises adjacent regions, and the resulting wave of depolarisation then spreads along the cell membrane. The polarisation of the membrane is restored as potassium ions flow back across the membrane from the inside to the outside of the cell. In cardiac muscle cells, as the action potential passes down the T-tubules it activates L-type calcium channels in the T-tubular membrane. Activation of the L-type calcium channel allows calcium to pass into the cell. T-tubules contain a higher concentration of L-type calcium channels than the rest of the sarcolemma and therefore the majority of the calcium that enters the cell occurs via T-tubules. This calcium binds to and activates a receptor, known as a ryanodine receptor, located on the cell's own internal calcium store, the sarcoplasmic reticulum. Activation of the ryanodine receptor causes calcium to be released from the sarcoplasmic reticulum, causing the muscle cell to contract. In skeletal muscle cells, however, the L-type calcium channel is directly attached to the ryanodine receptor on the sarcoplasmic reticulum allowing activation of the ryanodine receptor directly without the need for an influx of calcium. The importance of T-tubules is not solely due to their concentration of L-type calcium channels, but lies also within their ability to synchronise calcium release within the cell. The rapid spread of the action potential along the T-tubule network activates all of the L-type calcium channels near-simultaneously.

T-tubule - Wikipedia

One region of membrane depolarises adjacent regions, and the resulting wave of depolarisation then spreads along the cell membrane. The polarisation of the membrane is restored as potassium ions flow back across the membrane from the inside to the outside of the cell. In cardiac muscle cells, as the action potential passes down the T-tubules it activates L-type calcium channels in the T-tubular membrane. Activation of the L-type calcium channel allows calcium to pass into the cell. T-tubules contain a higher concentration of L-type calcium channels than the rest of the sarcolemma and therefore the majority of the calcium that enters the cell occurs via T-tubules. This calcium binds to and activates a receptor, known as a ryanodine receptor, located on the cell's own internal calcium store, the sarcoplasmic reticulum. Activation of the ryanodine receptor causes calcium to be released from the sarcoplasmic reticulum, causing the muscle cell to contract. In skeletal muscle cells, however, the L-type calcium channel is directly attached to the ryanodine receptor on the sarcoplasmic reticulum allowing activation of the ryanodine receptor directly without the need for an influx of calcium. The importance of T-tubules is not solely due to their concentration of L-type calcium channels, but lies also within their ability to synchronise calcium release within the cell. The rapid spread of the action potential along the T-tubule network activates all of the L-type calcium channels near-simultaneously.

T-tubule - Wikipedia

Cardiac muscle - Wikipedia Cardiac muscle
Cardiac muscle
Contents
Structure
Gross anatomy
Histology
Cardiac muscle cells
T-tubules
Intercalated discs
Fibroblasts
Extracellular matrix
Physiology
Regeneration
Differences between atria and ventricles
Clinical significance
See also
References
External links
 Cardiomyocytes contain T-tubules, pouches of membrane that run from the surface to the cell's interior which help to improve the efficiency of contraction. The majority of these cells contain only one nucleus (although they may have as many as four), unlike skeletal muscle cells which typically contain many nuclei. Cardiac muscle cells contain many mitochondria which provide the energy needed for the cell in the form of adenosine triphosphate (ATP), making them highly resistant to fatigue. T-tubules
Main article: T-tubules
T-tubules are microscopic tubes that run from the cell surface to deep within the cell. They are continuous with the cell membrane, are composed of the same phospholipid bilayer, and are open at the cell surface to the extracellular fluid that surrounds the cell. T-tubules in cardiac muscle are bigger and wider than those in skeletal muscle, but fewer in number. In the centre of the cell they join together, running into and along the cell as a transverse-axial network. Inside the cell they lie close to the cell's internal calcium store, the sarcoplasmic reticulum. Here, a single tubule pairs with part of the sarcoplasmic reticulum called a terminal cisterna in a combination known as a diad.

Cardiac muscle - Wikipedia

Cardiac muscle
Cardiac muscle
Contents
Structure
Gross anatomy
Histology
Cardiac muscle cells
T-tubules
Intercalated discs
Fibroblasts
Extracellular matrix
Physiology
Regeneration
Differences between atria and ventricles
Clinical significance
See also
References
External links

Cardiomyocytes contain T-tubules, pouches of membrane that run from the surface to the cell's interior which help to improve the efficiency of contraction. The majority of these cells contain only one nucleus (although they may have as many as four), unlike skeletal muscle cells which typically contain many nuclei. Cardiac muscle cells contain many mitochondria which provide the energy needed for the cell in the form of adenosine triphosphate (ATP), making them highly resistant to fatigue. T-tubules
Main article: T-tubules
T-tubules are microscopic tubes that run from the cell surface to deep within the cell. They are continuous with the cell membrane, are composed of the same phospholipid bilayer, and are open at the cell surface to the extracellular fluid that surrounds the cell. T-tubules in cardiac muscle are bigger and wider than those in skeletal muscle, but fewer in number. In the centre of the cell they join together, running into and along the cell as a transverse-axial network. Inside the cell they lie close to the cell's internal calcium store, the sarcoplasmic reticulum. Here, a single tubule pairs with part of the sarcoplasmic reticulum called a terminal cisterna in a combination known as a diad.

Cardiac muscle - Wikipedia Cardiac muscle
Cardiac muscle
Contents
Structure
Gross anatomy
Microanatomy
Cardiac muscle cells
T-tubules
Intercalated discs
Fibroblasts
Extracellular matrix
Physiology
Regeneration
Differences between atria and ventricles
Clinical significance
See also
References
External links
 Cardiomyocytes contain T-tubules, pouches of membrane that run from the surface to the cell's interior which help to improve the efficiency of contraction. The majority of these cells contain only one nucleus (although they may have as many as four), unlike skeletal muscle cells which typically contain many nuclei. Cardiac muscle cells contain many mitochondria which provide the energy needed for the cell in the form of adenosine triphosphate (ATP), making them highly resistant to fatigue. T-tubules
Main article: T-tubules
T-tubules are microscopic tubes that run from the cell surface to deep within the cell. They are continuous with the cell membrane, are composed of the same phospholipid bilayer, and are open at the cell surface to the extracellular fluid that surrounds the cell. T-tubules in cardiac muscle are bigger and wider than those in skeletal muscle, but fewer in number. In the centre of the cell they join together, running into and along the cell as a transverse-axial network. Inside the cell they lie close to the cell's internal calcium store, the sarcoplasmic reticulum. Here, a single tubule pairs with part of the sarcoplasmic reticulum called a terminal cisterna in a combination known as a diad.

Cardiac muscle - Wikipedia

Cardiac muscle
Cardiac muscle
Contents
Structure
Gross anatomy
Microanatomy
Cardiac muscle cells
T-tubules
Intercalated discs
Fibroblasts
Extracellular matrix
Physiology
Regeneration
Differences between atria and ventricles
Clinical significance
See also
References
External links

Cardiac muscle - Wikipedia Cardiac muscle
Cardiac muscle
From Wikipedia, the free encyclopedia
Contents
Structure
Gross anatomy
Microanatomy
Cardiac muscle cells
T-tubules
Intercalated discs
Fibroblasts
Extracellular matrix
Physiology
Regeneration
Differences between atria and ventricles
Clinical significance
See also
References
External links
 Cardiomyocytes contain T-tubules, pouches of membrane that run from the surface to the cell's interior which help to improve the efficiency of contraction. The majority of these cells contain only one nucleus (although they may have as many as four), unlike skeletal muscle cells which typically contain many nuclei. Cardiac muscle cells contain many mitochondria which provide the energy needed for the cell in the form of adenosine triphosphate (ATP), making them highly resistant to fatigue. T-tubules
Main article: T-tubules
T-tubules are microscopic tubes that run from the cell surface to deep within the cell. They are continuous with the cell membrane, are composed of the same phospholipid bilayer, and are open at the cell surface to the extracellular fluid that surrounds the cell. T-tubules in cardiac muscle are bigger and wider than those in skeletal muscle, but fewer in number. In the centre of the cell they join together, running into and along the cell as a transverse-axial network. Inside the cell they lie close to the cell's internal calcium store, the sarcoplasmic reticulum. Here, a single tubule pairs with part of the sarcoplasmic reticulum called a terminal cisterna in a combination known as a diad.

Cardiac muscle - Wikipedia

Cardiac muscle
Cardiac muscle
From Wikipedia, the free encyclopedia
Contents
Structure
Gross anatomy
Microanatomy
Cardiac muscle cells
T-tubules
Intercalated discs
Fibroblasts
Extracellular matrix
Physiology
Regeneration
Differences between atria and ventricles
Clinical significance
See also
References
External links

 Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronising calcium release throughout the cell.[1] T-tubule structure may be affected by disease, potentially contributing to heart failureand arrhythmias. Although these structures were first seen in 1897, research into T-tubule biology is ongoing. Contents
1Structure
1.1Regulators
2Function
2.1Excitation-contraction coupling
2.2Calcium control
2.3Detubulation
3History
4Clinical significance
5See also
6References
Structure[edit]
T-tubules are tubules formed from the same phospholipid bilayeras the surface membrane or sarcolemmaof skeletal or cardiac muscle cells.[1] They connect directly with the sarcolemma at one end before travelling deep within the cell, forming a network of tubules with sections running both perpendicular (transverse) to and parallel (axially) to the sarcolemma.[1] Due to this complex orientation, some refer to T-tubules as the transverse-axial tubular system.[2] The inside or lumen of the T-tubule is open at the cell surface, meaning that the T-tubule is filled with fluid containing the same constituents as the solution that surrounds the cell (the extracellular fluid). Rather than being just a passive connecting tube, the membrane that forms T-tubules is highly active, being studded with proteins including L-type calcium channels, sodium-calcium exchangers, calcium ATPases and Beta adrenoceptors. [ 1]
T-tubules are found in both atrialand ventricularcardiac muscle cells (cardiomyocytes), in which they develop in the first few weeks of life.[3] They are found in ventricular muscle cells in most species, and in atrial muscle cells from large mammals.[4] In cardiac muscle cells, T-tubules are between 20 and 450 nanometers in diameter and are usually located in regions called Z-discswhere the actin filaments anchor within the cell.[1] T-tubules within the heart are closely associated with the intracellular calcium store known as the sarcoplasmic reticulumin specific regions referred to as terminal cisternae. The association of the T-tubule with a terminal cistern is known as a diad. [ 5]
In skeletal muscle cells, T-tubules are between 20 and 40 nm in diameter and are typically located either side of the myosin strip, at the junction of overlap between the A and I bands. T-tubules in skeletal muscle are associated with two terminal cisternae, known as a triad. [ 1][6]
Regulators[edit]
The shape of the T-tubule system is produced and maintained by a variety of proteins. The protein amphiphysin-2is encoded by the gene BIN1and is responsible for forming the structure of the T-tubule and ensuring that the appropriate proteins (in particular L-type calcium channels) are located within the T-tubule membrane.[7] Junctophilin-2 is encoded by the gene JPH2and helps to form a junction between the T-tubule membrane and the sarcoplasmic reticulum, vital for excitation-contraction coupling.[5] Titin capping protein or Telethonin is encoded by the gene TCAPand helps with T-tubule development and is potentially responsible for the increasing number of T-tubules seen as muscles grow. [

T-tubule | Psychology Wiki | Fandom T-tubule
T-tubule
Contents
Structure
Excitation-contraction coupling
Detubulation
See also
External links
 Cardiac muscle has a similar structure; instead of a triad there is a diad, which is composed of a T-tubule and a single terminal cisterna, and it occurs at the Z line. It is physiologically important for excitation-contraction coupling (see section below) that the T-tubules are positioned close to the terminal cisternae of the sarcoplasmic reticulum as the triad or diad arrangement allows physical and functional contact by voltage dependent L-type calcium channels. So, an action potential along the sarcolemma causes calcium channels to open in the terminal cisternae / sarcoplasmic reticulum which enables calcium to move from the sarcoplasmic reticulum into cytoplasm and the intracellular calcium concentration to increase. Excitation-contraction coupling
See Excitation-contraction coupling
T-tubules are the major sites for the coupling of excitation and contraction, which is the process whereby the spreading depolarization is converted into force production by muscle fibers. The L-type calcium channels in T-tubules activate in response to electrical stimulation; their opening allows calcium to flow down its electrochemical gradient and into the cell. Activation of the L-type channel also causes a mechanical interaction between it and calcium-release channels located on the adjacent sarcoplasmic reticulum membrane. In skeletal muscle, the influx of calcium through the L-type calcium channel on the T-tubule contributes little to excitation-contraction coupling, whereas it is crucial to the proper function of cardiac muscle ( see Cardiac action potential ). Conversely, the mechanical interaction between the T-tubule's L-type calcium channel and the calcium-release channel is critical to proper skeletal muscle contraction, whereas it contributes little to the contraction of cardiac muscle.

T-tubule | Psychology Wiki | Fandom

Cardiac muscle has a similar structure; instead of a triad there is a diad, which is composed of a T-tubule and a single terminal cisterna, and it occurs at the Z line. It is physiologically important for excitation-contraction coupling (see section below) that the T-tubules are positioned close to the terminal cisternae of the sarcoplasmic reticulum as the triad or diad arrangement allows physical and functional contact by voltage dependent L-type calcium channels. So, an action potential along the sarcolemma causes calcium channels to open in the terminal cisternae / sarcoplasmic reticulum which enables calcium to move from the sarcoplasmic reticulum into cytoplasm and the intracellular calcium concentration to increase. Excitation-contraction coupling
See Excitation-contraction coupling
T-tubules are the major sites for the coupling of excitation and contraction, which is the process whereby the spreading depolarization is converted into force production by muscle fibers. The L-type calcium channels in T-tubules activate in response to electrical stimulation; their opening allows calcium to flow down its electrochemical gradient and into the cell. Activation of the L-type channel also causes a mechanical interaction between it and calcium-release channels located on the adjacent sarcoplasmic reticulum membrane. In skeletal muscle, the influx of calcium through the L-type calcium channel on the T-tubule contributes little to excitation-contraction coupling, whereas it is crucial to the proper function of cardiac muscle ( see Cardiac action potential ). Conversely, the mechanical interaction between the T-tubule's L-type calcium channel and the calcium-release channel is critical to proper skeletal muscle contraction, whereas it contributes little to the contraction of cardiac muscle.

T-tubule - Wikipedia

 This is important as, regardless of the ion concentrations elsewhere in the cell, T-tubules still have enough calcium ions to permit muscle contraction. Therefore, even if the concentration of calcium outside the cell falls (hypocalcaemia), the concentration of calcium within the  T-tubule remains relatively constant, allowing cardiac contraction to continue. [ 5]
As well as T-tubules being a site for calcium entry into the cell, they are also a site for calcium removal. This is important as it means that calcium levels within the cell can be tightly controlled in a small area (i.e. between the T-tubule and sarcoplasmic reticulum, known as local control).[15] Proteins such as the sodium-calcium exchanger and the sarcolemmal ATPase are located mainly in the T-tubule membrane.[5] The sodium-calcium exchanger passively removes one calcium ion from the cell in exchange for three sodium ions. As a passive process it can therefore allow calcium to flow into or out of the cell depending on the combination of the relative concentrations of these ions and the voltage across the cell membrane (the electrochemical gradient).[8] The calcium ATPase removes calcium from the cell actively, using energy derived from  adenosine triphosphate(ATP). [ 8]
Detubulation[edit]
In order to study T-tubule function, T-tubules can be artificially uncoupled from the surface membrane using a technique known as detubulation. Chemicals such as glycerol[16]or formamide[12](for skeletal and cardiac muscle respectively) can be added to the extracellular solution that surrounds the cells. These agents increase the osmolarity of the extracellular solution, causing the cells to shrink. When these agents are withdrawn, the cells rapidly expand and return to their normal size. This shrinkage and re-expansion of the cell causes T-tubules to detach from the surface mem

This is important as, regardless of the ion concentrations elsewhere in the cell, T-tubules still have enough calcium ions to permit muscle contraction. Therefore, even if the concentration of calcium outside the cell falls (hypocalcaemia), the concentration of calcium within the  T-tubule remains relatively constant, allowing cardiac contraction to continue. [ 5]
As well as T-tubules being a site for calcium entry into the cell, they are also a site for calcium removal. This is important as it means that calcium levels within the cell can be tightly controlled in a small area (i.e. between the T-tubule and sarcoplasmic reticulum, known as local control).[15] Proteins such as the sodium-calcium exchanger and the sarcolemmal ATPase are located mainly in the T-tubule membrane.[5] The sodium-calcium exchanger passively removes one calcium ion from the cell in exchange for three sodium ions. As a passive process it can therefore allow calcium to flow into or out of the cell depending on the combination of the relative concentrations of these ions and the voltage across the cell membrane (the electrochemical gradient).[8] The calcium ATPase removes calcium from the cell actively, using energy derived from  adenosine triphosphate(ATP). [ 8]
Detubulation[edit]
In order to study T-tubule function, T-tubules can be artificially uncoupled from the surface membrane using a technique known as detubulation. Chemicals such as glycerol[16]or formamide[12](for skeletal and cardiac muscle respectively) can be added to the extracellular solution that surrounds the cells. These agents increase the osmolarity of the extracellular solution, causing the cells to shrink. When these agents are withdrawn, the cells rapidly expand and return to their normal size. This shrinkage and re-expansion of the cell causes T-tubules to detach from the surface mem

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 In cardiac muscle cells, T-tubules are between 20 and 450 nanometers in diameter and are usually located in regions called Z-discs where the actin filaments anchor within the cell. T-tubules within the heart are closely associated with the intracellular calcium store known as the sarcoplasmic reticulum in specific regions referred to as terminal cisternae. The association of the T-tubule with a terminal cistern is known as a diad. In skeletal muscle cells, T-tubules are between 20 and 40 nm in diameter and are typically located either side of the myosin strip, at the junction of overlap between the A and I bands. T-tubules in skeletal muscle are associated with two terminal cisternae, known as a triad. Regulators
The shape of the T-tubule system is produced and maintained by a variety of proteins. The protein amphiphysin-2 is encoded by the gene BIN1 and is responsible for forming the structure of the T-tubule and ensuring that the appropriate proteins (in particular L-type calcium channels) are located within the T-tubule membrane. Junctophilin-2 is encoded by the gene JPH2 and helps to form a junction between the T-tubule membrane and the sarcoplasmic reticulum, vital for excitation-contraction coupling. Titin capping protein or Telethonin is encoded by the gene TCAP and helps with T-tubule development and is potentially responsible for the increasing number of T-tubules seen as muscles grow. Function
Excitation-contraction coupling
See also:

T-tubule - Wikipedia

In cardiac muscle cells, T-tubules are between 20 and 450 nanometers in diameter and are usually located in regions called Z-discs where the actin filaments anchor within the cell. T-tubules within the heart are closely associated with the intracellular calcium store known as the sarcoplasmic reticulum in specific regions referred to as terminal cisternae. The association of the T-tubule with a terminal cistern is known as a diad. In skeletal muscle cells, T-tubules are between 20 and 40 nm in diameter and are typically located either side of the myosin strip, at the junction of overlap between the A and I bands. T-tubules in skeletal muscle are associated with two terminal cisternae, known as a triad. Regulators
The shape of the T-tubule system is produced and maintained by a variety of proteins. The protein amphiphysin-2 is encoded by the gene BIN1 and is responsible for forming the structure of the T-tubule and ensuring that the appropriate proteins (in particular L-type calcium channels) are located within the T-tubule membrane. Junctophilin-2 is encoded by the gene JPH2 and helps to form a junction between the T-tubule membrane and the sarcoplasmic reticulum, vital for excitation-contraction coupling. Titin capping protein or Telethonin is encoded by the gene TCAP and helps with T-tubule development and is potentially responsible for the increasing number of T-tubules seen as muscles grow. Function
Excitation-contraction coupling
See also:

Cardiac T-Tubule Microanatomy and Function | Physiological Reviews Cardiac T-Tubule Microanatomy and Function
Cardiac T-Tubule Microanatomy and Function
Abstract
I. INTRODUCTION
II. CARDIAC T-TUBULE STRUCTURE
A. History of T-Tubule Structure-Related Research
B. Gross Morphology and Geometry
C. Membrane Ultrastructure and Microdomains
1. cBIN1 microfolds: microdomains supporting LTCC-RyR dyads
2. Caveoli (caveolae): β-AR/LTCC signaling hubs
3. Ankyrin B microdomains: NCX/NKA/InsP 3 macromolecular complex
D. Peri-Membrane Cytoskeleton Scaffolds at Cardiac T-Tubules
1. Actin filaments, tropomyosin, and N-WASP
2. Costamere complex and t-tubule membrane-associated scaffolds
3. Myofilament structural proteins
E. Variation in Cardiac T-Tubule Geometry
III. TRANSMEMBRANE PROTEINS AT CARDIAC T-TUBULES
A. Ion Handling Proteins (Channels/Transporters/Pumps)
1. Ca 2+ handling proteins
2. Na + handling proteins
3. K + handling proteins
B. Signaling Molecules at Cardiac T-Tubules
IV. FUNCTION OF CARDIAC T-TUBULES
A. Dyad and EC Coupling
1. LTCC trafficking and clustering to dyads through BIN1
2. RyR recruitment to dyads through BIN1
3. Junctophilin-2 in t-tubule-jSR junctional membrane complex formation
B. Ion Diffusion and Membrane Excitability
C. Other Microdomain-Related Functions
V. LIFE CYCLE OF CARDIAC T-TUBULES
A. Membrane Biogenesis, Maintenance, and Turnover
B. Ion Channel Trafficking and Half-Life
VI. ALTERATION OF T-TUBULE STRUCTURE AND FUNCTION IN HEART FAILURE
VII. CONCLUSIONS
GRANTS
DISCLOSURES
Acknowledgments
 Cardiac t-tubules contain membrane microdomains enriched with ion channels and signaling molecules. The microdomains serve as key signaling hubs in regulation of cardiomyocyte function. Dyad microdomains formed at the junctional contact between t-tubule membrane and neighboring sarcoplasmic reticulum are critical in calcium signaling and excitation-contraction coupling necessary for beat-to-beat heart contraction. In this review, we provide an overview of the current knowledge in gross morphology and structure, membrane and protein composition, and function of the cardiac t-tubule network. We also review in detail current knowledge on the formation of functional membrane subdomains within t-tubules, with a particular focus on the cardiac dyad microdomain. Lastly, we discuss the dynamic nature of t-tubules including membrane turnover, trafficking of transmembrane proteins, and the life cycles of membrane subdomains such as the cardiac BIN1-microdomain, as well as t-tubule remodeling and alteration in diseased hearts. Understanding cardiac t-tubule biology in normal and failing hearts is providing novel diagnostic and therapeutic opportunities to better treat patients with failing hearts. I. INTRODUCTION
Cardiac transverse tubules (t-tubules) are highly branched invaginations of cardiomyocyte sarcolemma that are rich in ion channels important for excitation-contraction (EC) coupling, maintenance of resting membrane potential, action potential initiation and regulation, and signaling transduction. Specific to striated muscle cells, t-tubules are invaginations of the sarcolemma, penetrating into the intracellular space of myocytes. These tubular invaginations form a complex network with transverse tubules that are interconnected within the cytoplasm by longitudinal tubules.

Cardiac t-tubules contain membrane microdomains enriched with ion channels and signaling molecules. The microdomains serve as key signaling hubs in regulation of cardiomyocyte function. Dyad microdomains formed at the junctional contact between t-tubule membrane and neighboring sarcoplasmic reticulum are critical in calcium signaling and excitation-contraction coupling necessary for beat-to-beat heart contraction. In this review, we provide an overview of the current knowledge in gross morphology and structure, membrane and protein composition, and function of the cardiac t-tubule network. We also review in detail current knowledge on the formation of functional membrane subdomains within t-tubules, with a particular focus on the cardiac dyad microdomain. Lastly, we discuss the dynamic nature of t-tubules including membrane turnover, trafficking of transmembrane proteins, and the life cycles of membrane subdomains such as the cardiac BIN1-microdomain, as well as t-tubule remodeling and alteration in diseased hearts. Understanding cardiac t-tubule biology in normal and failing hearts is providing novel diagnostic and therapeutic opportunities to better treat patients with failing hearts. I. INTRODUCTION
Cardiac transverse tubules (t-tubules) are highly branched invaginations of cardiomyocyte sarcolemma that are rich in ion channels important for excitation-contraction (EC) coupling, maintenance of resting membrane potential, action potential initiation and regulation, and signaling transduction. Specific to striated muscle cells, t-tubules are invaginations of the sarcolemma, penetrating into the intracellular space of myocytes. These tubular invaginations form a complex network with transverse tubules that are interconnected within the cytoplasm by longitudinal tubules.

T-Tubule Function in Mammalian Cardiac Myocytes | Circulation Research T-Tubule Function in Mammalian Cardiac Myocytes
T-Tubule Function in Mammalian Cardiac Myocytes
Abstract
Occurrence and Morphology of the T-Tubules
T-Tubule Development Is Labile
Proteins Present in the T-Tubule Membrane
Ca2+-Handling Proteins
Na+-Handling Proteins
K+-Handling Proteins
Anion-Handling Proteins
Second-Messenger Pathways
Interpretation of Immunohistochemical Data
Protein Colocalization Within, and With Proteins Adjacent to, the T-Tubules
Localization of Function
Cells Lacking T-Tubules
Diffusion Studies
Scanning Pipette
Detubulation
Functional Role
Electrical Properties of T-Tubules
Coupling of Ca 2+ Entry and Ca 2+ Release
Ca 2+ Efflux
Signal Transduction
Changes During Development and Disease
T-Tubule Development and Morphology in Hypertrophy and Failure
Changes in Protein Expression in Development, Hypertrophy, and Failure
Relevance of Changes in T-Tubule Structure and Protein Expression to Function
Conclusions and Unanswered Questions
Footnotes
References
 The purpose of this review is to provide an overview of recent studies of t-tubule structure and function in cardiac myocytes. The transverse tubules (t-tubules) of mammalian cardiac ventricular myocytes are invaginations of the surface membrane that occur at the Z line and have both transverse and longitudinal elements. Many of the proteins involved in excitation-contraction coupling appear to be concentrated at the t-tubules. Therefore, it has been suggested that the t-tubules play a central role in cell activation. In the present review, we will consider the immunohistochemical and functional evidence for protein localization at the t-tubules, potential problems in the interpretation of such data, and the functional consequences of such localization. We will also consider the possible role of the t-tubules in the functional changes that occur during cardiac development, hypertrophy, and failure. Occurrence and Morphology of the T-Tubules
T-tubules are present in the cardiac tissue of all species of mammals so far investigated (eg, mice, 1 rats, 2 guinea pigs, 3 rabbits, 4 dogs, 5 pigs, 1 and humans 6) but appear to be absent in avian, 7 reptile 8 and amphibian 8 cardiac tissue. Within mammalian cardiac tissue, t-tubules occur predominantly in ventricular myocytes, being either absent or far less developed in atrial, pacemaking, and conducting tissue, 9 although a recent report has suggested that ≈50% of atrial myocytes possess a sparse irregular tubular system. 10 The following discussion will concentrate on mammalian ventricular myocytes. The t-tubules are invaginations of the sarcolemma and glycocalyx, which appears to remain associated with the sarcolemma within the t-tubules.

The purpose of this review is to provide an overview of recent studies of t-tubule structure and function in cardiac myocytes. The transverse tubules (t-tubules) of mammalian cardiac ventricular myocytes are invaginations of the surface membrane that occur at the Z line and have both transverse and longitudinal elements. Many of the proteins involved in excitation-contraction coupling appear to be concentrated at the t-tubules. Therefore, it has been suggested that the t-tubules play a central role in cell activation. In the present review, we will consider the immunohistochemical and functional evidence for protein localization at the t-tubules, potential problems in the interpretation of such data, and the functional consequences of such localization. We will also consider the possible role of the t-tubules in the functional changes that occur during cardiac development, hypertrophy, and failure. Occurrence and Morphology of the T-Tubules
T-tubules are present in the cardiac tissue of all species of mammals so far investigated (eg, mice, 1 rats, 2 guinea pigs, 3 rabbits, 4 dogs, 5 pigs, 1 and humans 6) but appear to be absent in avian, 7 reptile 8 and amphibian 8 cardiac tissue. Within mammalian cardiac tissue, t-tubules occur predominantly in ventricular myocytes, being either absent or far less developed in atrial, pacemaking, and conducting tissue, 9 although a recent report has suggested that ≈50% of atrial myocytes possess a sparse irregular tubular system. 10 The following discussion will concentrate on mammalian ventricular myocytes. The t-tubules are invaginations of the sarcolemma and glycocalyx, which appears to remain associated with the sarcolemma within the t-tubules.

Renal system - Tubule function | Britannica
Tubule function
Reabsorption from the proximal tubule
Reabsorption from the loop of Henle
Reabsorption from the distal convoluted tubule
 Renal system - Tubule function | Britannica
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Tubule function
The role of the tubules may be assessed by comparing the amounts of various substances in the filtrate and in the urine ( Table 2). Effect of tubular reabsorption on urine
(illustrative 24-hour figures)

glomerular
filtrate
urine
tubular
reabsorption
(percent)
water
170 l
1.5
99.1
glucose
170 g
—
100
sodium
560 g
5 g
99.1
chloride
620 g
9 g
98.5
phosphate
5.1 g
1.2 g
76.5
calcium
17 g
0.2 g
98.8
urea
51 g
30 g
41.4
sulfate
3.4 g
2.7 g
20.6
It is apparent that the filtrate must be modified in the tubules to account for the differing compositions of filtrate and final urine—e.g., to allow for the total absence of glucose in the latter, the much smaller volume of urine than filtrate, or for the acidity of urine compared with the neutrality of the filtrate. As the filtrate passes along the proximal tubule, most of its water and salts are reabsorbed into the blood of the network of capillaries around the tubules. Of other substances, some are reabsorbed completely, others in part, because this portion of the nephron separates substances that must be retained in the body from those destined for excretion in the urine. The function of the proximal tubule is essentially reabsorption of filtrate in accordance with the needs of homeostasis (equilibrium), whereas the distal part of the nephron and collecting duct are mainly concerned with the detailed regulation of water, electrolyte, and hydrogen-ion balance. All of these processes occur in the tubules through both chemical and physical means, and all are subject to hormonal regulation. Although the urine normally differs markedly from filtrate, if tubule function is progressively reduced in experimental situations by cooling or poisoning, the urine will come increasingly to resemble the filtrate. Also, the more rapidly filtration occurs, the less time there is for the urine to be modified during its passage through the tubules. Reabsorption from the proximal tubule
Reabsorption affects all the glucose of the filtrate, up to 70 percent of its water and sodium (the remainder is absorbed in the distal tubule), most of the potassium and chloride ions, some of the uric acid, 40 percent of the urea, and little or none of the sulfate.

Renal system - Tubule function | Britannica

Tubule function
Reabsorption from the proximal tubule
Reabsorption from the loop of Henle
Reabsorption from the distal convoluted tubule

T-Tubule - an overview | ScienceDirect Topics T-Tubule
T-Tubule
Ion Channel Trafficking
T-Tubules
Skeletal Muscle
T-tubules Are Surface Invaginations; the SR Is an Internal Membrane System
Structure and Function of Calcium Release Channels
2 T Tubules and CRUs Revert to More Primitive Forms Under Pathological Conditions
Muscles
Coupling Action Potentials to Contraction
The Cellular Basis of Cardiac Contractility
The SR Releases Stored Ca 2+ to Activate Contraction
Disorders of Muscle Excitability
Calcium couples muscle membrane excitation to filament contraction
Muscle physiology
Excitation–contraction coupling
EXERCISE | Muscle
Voltage-dependent Sarcoplasmic Reticulum Ca 2+ Release
 T-Tubule - an overview | ScienceDirect Topics
T-Tubule
T tubules extend from the free surface throughout the cells in a generally transverse direction, coursing around the myofibrils at the levels of the Z bands. From: Haschek and Rousseaux's Handbook of Toxicologic Pathology (Third Edition), 2013
Download as PDF
About this page
Ion Channel Trafficking
T.T. Hong, R.M. Shaw, in Ion Channels in Health and Disease, 2016
T-Tubules
T-tubule membrane is associated with a unique set of ion channels supported by membrane structural subdomains.23 Immunocytochemistry and patch clamp data indicate that 80% of the sarcolemma LTCCs are concentrated at T-tubules. Localization of LTCCs to T-tubules is critical in bringing LTCCs to the vicinity of calcium sense and release channel RyR at SR membrane. Approximation of LTCCs and RyRs form a functional microdomain, the cardiac dyads, which are the individual calcium-releasing units in cardiomyocytes. As discussed earlier, Targeted Delivery also applies to Cav1.2 channel localization to T-tubule surface, which requires a membrane scaffolding protein BIN1. 26 Interestingly, BIN1 also forms minifolds within T-tubules, affecting extracellular ion diffusion thereby controlling the driving force of Cav1.2 channel activity. 6 BIN1-folded subdomains within T-tubules may also limit LTCC lateral diffusion once the channels are inserted into T-tubule membrane, to maintain functional LTCC-RyR dyads. Therefore, BIN1-like membrane scaffold proteins may help localize particular pools of ion channel proteins to membrane subdomains for compartmentalized regulation of ion channel activity and function. Similarly, ankyrin B can play a role similar to BIN1 in clustering NCX/NKA/InsP3 complex to microdomains distinct from the dyads.

T-Tubule - an overview | ScienceDirect Topics

T-Tubule
T-Tubule
Ion Channel Trafficking
T-Tubules
Skeletal Muscle
T-tubules Are Surface Invaginations; the SR Is an Internal Membrane System
Structure and Function of Calcium Release Channels
2 T Tubules and CRUs Revert to More Primitive Forms Under Pathological Conditions
Muscles
Coupling Action Potentials to Contraction
The Cellular Basis of Cardiac Contractility
The SR Releases Stored Ca 2+ to Activate Contraction
Disorders of Muscle Excitability
Calcium couples muscle membrane excitation to filament contraction
Muscle physiology
Excitation–contraction coupling
EXERCISE | Muscle
Voltage-dependent Sarcoplasmic Reticulum Ca 2+ Release

T-Tubule - an overview | ScienceDirect Topics
T-Tubule
T tubules extend from the free surface throughout the cells in a generally transverse direction, coursing around the myofibrils at the levels of the Z bands. From: Haschek and Rousseaux's Handbook of Toxicologic Pathology (Third Edition), 2013
Download as PDF
About this page
Ion Channel Trafficking
T.T. Hong, R.M. Shaw, in Ion Channels in Health and Disease, 2016
T-Tubules
T-tubule membrane is associated with a unique set of ion channels supported by membrane structural subdomains.23 Immunocytochemistry and patch clamp data indicate that 80% of the sarcolemma LTCCs are concentrated at T-tubules. Localization of LTCCs to T-tubules is critical in bringing LTCCs to the vicinity of calcium sense and release channel RyR at SR membrane. Approximation of LTCCs and RyRs form a functional microdomain, the cardiac dyads, which are the individual calcium-releasing units in cardiomyocytes. As discussed earlier, Targeted Delivery also applies to Cav1.2 channel localization to T-tubule surface, which requires a membrane scaffolding protein BIN1. 26 Interestingly, BIN1 also forms minifolds within T-tubules, affecting extracellular ion diffusion thereby controlling the driving force of Cav1.2 channel activity. 6 BIN1-folded subdomains within T-tubules may also limit LTCC lateral diffusion once the channels are inserted into T-tubule membrane, to maintain functional LTCC-RyR dyads. Therefore, BIN1-like membrane scaffold proteins may help localize particular pools of ion channel proteins to membrane subdomains for compartmentalized regulation of ion channel activity and function. Similarly, ankyrin B can play a role similar to BIN1 in clustering NCX/NKA/InsP3 complex to microdomains distinct from the dyads.

Cardiac T-Tubule Microanatomy and Function | Physiological Reviews Cardiac T-Tubule Microanatomy and Function
Cardiac T-Tubule Microanatomy and Function
Abstract
I. INTRODUCTION
II. CARDIAC T-TUBULE STRUCTURE
A. History of T-Tubule Structure-Related Research
B. Gross Morphology and Geometry
C. Membrane Ultrastructure and Microdomains
1. cBIN1 microfolds: microdomains supporting LTCC-RyR dyads
2. Caveoli (caveolae): β-AR/LTCC signaling hubs
3. Ankyrin B microdomains: NCX/NKA/InsP 3 macromolecular complex
D. Peri-Membrane Cytoskeleton Scaffolds at Cardiac T-Tubules
1. Actin filaments, tropomyosin, and N-WASP
2. Costamere complex and t-tubule membrane-associated scaffolds
3. Myofilament structural proteins
E. Variation in Cardiac T-Tubule Geometry
III. TRANSMEMBRANE PROTEINS AT CARDIAC T-TUBULES
A. Ion Handling Proteins (Channels/Transporters/Pumps)
1. Ca 2+ handling proteins
2. Na + handling proteins
3. K + handling proteins
B. Signaling Molecules at Cardiac T-Tubules
IV. FUNCTION OF CARDIAC T-TUBULES
A. Dyad and EC Coupling
1. LTCC trafficking and clustering to dyads through BIN1
2. RyR recruitment to dyads through BIN1
3. Junctophilin-2 in t-tubule-jSR junctional membrane complex formation
B. Ion Diffusion and Membrane Excitability
C. Other Microdomain-Related Functions
V. LIFE CYCLE OF CARDIAC T-TUBULES
A. Membrane Biogenesis, Maintenance, and Turnover
B. Ion Channel Trafficking and Half-Life
VI. ALTERATION OF T-TUBULE STRUCTURE AND FUNCTION IN HEART FAILURE
VII. CONCLUSIONS
GRANTS
DISCLOSURES
Acknowledgments
 TRANSMEMBRANE PROTEINS AT CARDIAC T-TUBULES
A. Ion Handling Proteins (Channels/Transporters/Pumps)
B. Signaling Molecules at Cardiac T-Tubules
IV. FUNCTION OF CARDIAC T-TUBULES
A. Dyad and EC Coupling
B. Ion Diffusion and Membrane Excitability
C. Other Microdomain-Related Functions
V. LIFE CYCLE OF CARDIAC T-TUBULES
A. Membrane Biogenesis, Maintenance, and Turnover
B. Ion Channel Trafficking and Half-Life
VI. ALTERATION OF T-TUBULE STRUCTURE AND FUNCTION IN HEART FAILURE
VII. CONCLUSIONS
GRANTS
DISCLOSURES
Acknowledgments
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Abstract
Unique to striated muscle cells, transverse tubules (t-tubules) are membrane organelles that consist of sarcolemma penetrating into the myocyte interior, forming a highly branched and interconnected network. Mature t-tubule networks are found in mammalian ventricular cardiomyocytes, with the transverse components of t-tubules occurring near sarcomeric z-discs. Cardiac t-tubules contain membrane microdomains enriched with ion channels and signaling molecules. The microdomains serve as key signaling hubs in regulation of cardiomyocyte function. Dyad microdomains formed at the junctional contact between t-tubule membrane and neighboring sarcoplasmic reticulum are critical in calcium signaling and excitation-contraction coupling necessary for beat-to-beat heart contraction. In this review, we provide an overview of the current knowledge in gross morphology and structure, membrane and protein composition, and function of the cardiac t-tubule network. We also review in detail current knowledge on the formation of functional membrane subdomains within t-tubules, with a particular focus on the cardiac dyad microdomain.

TRANSMEMBRANE PROTEINS AT CARDIAC T-TUBULES
A. Ion Handling Proteins (Channels/Transporters/Pumps)
B. Signaling Molecules at Cardiac T-Tubules
IV. FUNCTION OF CARDIAC T-TUBULES
A. Dyad and EC Coupling
B. Ion Diffusion and Membrane Excitability
C. Other Microdomain-Related Functions
V. LIFE CYCLE OF CARDIAC T-TUBULES
A. Membrane Biogenesis, Maintenance, and Turnover
B. Ion Channel Trafficking and Half-Life
VI. ALTERATION OF T-TUBULE STRUCTURE AND FUNCTION IN HEART FAILURE
VII. CONCLUSIONS
GRANTS
DISCLOSURES
Acknowledgments
PDF (4 MB)
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Abstract
Unique to striated muscle cells, transverse tubules (t-tubules) are membrane organelles that consist of sarcolemma penetrating into the myocyte interior, forming a highly branched and interconnected network. Mature t-tubule networks are found in mammalian ventricular cardiomyocytes, with the transverse components of t-tubules occurring near sarcomeric z-discs. Cardiac t-tubules contain membrane microdomains enriched with ion channels and signaling molecules. The microdomains serve as key signaling hubs in regulation of cardiomyocyte function. Dyad microdomains formed at the junctional contact between t-tubule membrane and neighboring sarcoplasmic reticulum are critical in calcium signaling and excitation-contraction coupling necessary for beat-to-beat heart contraction. In this review, we provide an overview of the current knowledge in gross morphology and structure, membrane and protein composition, and function of the cardiac t-tubule network. We also review in detail current knowledge on the formation of functional membrane subdomains within t-tubules, with a particular focus on the cardiac dyad microdomain.

T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases | Skeletal Muscle | Full Text T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
Abstract
Introduction
T-tubule plasticity
Morphological aspects of triad biogenesis
Sarcoplasmic reticulum
Transverse tubule
Molecular mechanisms involved in T-tubule biogenesis and triad formation and maintenance
Table 1 Proteins implicated in triad organization, roles and associated human diseasesa
Caveolin 3
Amphiphysin 2 (BIN1)
Dysferlin
Mitsugumins
Junctophilins
Myotubularin
The RyR-DHPR complex
Conclusion
References
Acknowledgements
Author information
Affiliations
Corresponding author
Additional information
Competing interests
Authors' contributions
Authors’ original submitted files for images
Authors’ original file for figure 1
Authors’ original file for figure 2
Authors’ original file for figure 3
Authors’ original file for figure 4
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About this article
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Share this article
Keywords
 At E16, RyR containing elements become abundant and start to be associated with the edges of A bands (A-I junctions) of the newly formed sarcomeres. This association results in a distinct banding pattern of a discrete SR network at the I-band with thin longitudinal connecting SR elements [ 17 ]. During the next days (E17 and E18), junctional SR acquires a predominant transverse distribution taking their final position by forming triad rows at each side of the Z-line (two SR sacs connecting one T-tubule in each triad) [ 17 ]. During the maturation of SR membranes, the frequency of feet increases, in particular, between E16 and E18, when all junctions become filled by feet. The width of the junctional gap is between 9 and 12 nm. The maturation of the RyR containing elements is accomplished at birth [ 17 ]. Elegant experiments using tagged SR proteins in differentiating myotubes showed that the SR organization was paralleled by a dynamic localization of longitudinal and junctional SR proteins [ 19 ]. Transverse tubule
T-tubules are invaginations of the plasma membrane, which are present exclusively in striated muscle. Their role is to maintain the SR calcium store under the tight control of membrane depolarization via the volta

At E16, RyR containing elements become abundant and start to be associated with the edges of A bands (A-I junctions) of the newly formed sarcomeres. This association results in a distinct banding pattern of a discrete SR network at the I-band with thin longitudinal connecting SR elements [ 17 ]. During the next days (E17 and E18), junctional SR acquires a predominant transverse distribution taking their final position by forming triad rows at each side of the Z-line (two SR sacs connecting one T-tubule in each triad) [ 17 ]. During the maturation of SR membranes, the frequency of feet increases, in particular, between E16 and E18, when all junctions become filled by feet. The width of the junctional gap is between 9 and 12 nm. The maturation of the RyR containing elements is accomplished at birth [ 17 ]. Elegant experiments using tagged SR proteins in differentiating myotubes showed that the SR organization was paralleled by a dynamic localization of longitudinal and junctional SR proteins [ 19 ]. Transverse tubule
T-tubules are invaginations of the plasma membrane, which are present exclusively in striated muscle. Their role is to maintain the SR calcium store under the tight control of membrane depolarization via the volta

T-tubule | Psychology Wiki | Fandom T-tubule
T-tubule
Contents
Structure
Excitation-contraction coupling
Detubulation
See also
External links
 The L-type calcium channels in T-tubules activate in response to electrical stimulation; their opening allows calcium to flow down its electrochemical gradient and into the cell. Activation of the L-type channel also causes a mechanical interaction between it and calcium-release channels located on the adjacent sarcoplasmic reticulum membrane. In skeletal muscle, the influx of calcium through the L-type calcium channel on the T-tubule contributes little to excitation-contraction coupling, whereas it is crucial to the proper function of cardiac muscle ( see Cardiac action potential ). Conversely, the mechanical interaction between the T-tubule's L-type calcium channel and the calcium-release channel is critical to proper skeletal muscle contraction, whereas it contributes little to the contraction of cardiac muscle. Detubulation
It is possible to physically and functionally uncouple T-tubules from the surface membrane using a technique known as detubulation. This relies on osmotically active chemicals, such as glycerol (for skeletal muscle) or formamide (mainly for cardiac muscle ). Addition of these chemicals to the solution surrounding muscle cells causes the cells to shrink; when the chemical is withdrawn the cells rapidly expand before returning to their normal size. The rapid expansion is thought to cause the t-tubules to detach from the surface membrane, which reseals, and to reseal within the cell.

T-tubule | Psychology Wiki | Fandom

The Muscular System
 One of the three polypeptides (TnI) is an inhibitory subunit that binds to actin. Another (TnT) binds to tropomyosin and helps to position it on actin, while a third one (TnC) binds calcium ions. IV) The Sarcoplasmic Reticulum (SR) acts to regulate intracellular levels of ionic calcium in that it stores calcium and releases it on demand when the muscle fiber is stimulated to contract. The SR is the endoplasmic reticulum of the muscle cell and consists of interconnecting tubules that surround each of the myofibrils. The tubules run longitudinally along the myofibrils and some form perpendicular cross channels called terminal cisternae (end sacs) at the A-I junctions and they also occur in pairs. V) The T tubules or transverse tubules are elongated tubes formed at the A band-I band junction by the sarcolemma penetrating into the cell at this point. The lumen (inside of each T tubule) is continuous with the extracellular space. Each T tubule runs between the paired terminal cisternae of the SR forming triads (successive groupings of the three membranous structures of a Tubule between two terminal cisternae). The T tubules also encircle each sarcomere as they pass from one myofibril to the next. The T tubules can conduct impulses from the sarcolemma to each of the sarcomeres.

The Muscular System

One of the three polypeptides (TnI) is an inhibitory subunit that binds to actin. Another (TnT) binds to tropomyosin and helps to position it on actin, while a third one (TnC) binds calcium ions. IV) The Sarcoplasmic Reticulum (SR) acts to regulate intracellular levels of ionic calcium in that it stores calcium and releases it on demand when the muscle fiber is stimulated to contract. The SR is the endoplasmic reticulum of the muscle cell and consists of interconnecting tubules that surround each of the myofibrils. The tubules run longitudinally along the myofibrils and some form perpendicular cross channels called terminal cisternae (end sacs) at the A-I junctions and they also occur in pairs. V) The T tubules or transverse tubules are elongated tubes formed at the A band-I band junction by the sarcolemma penetrating into the cell at this point. The lumen (inside of each T tubule) is continuous with the extracellular space. Each T tubule runs between the paired terminal cisternae of the SR forming triads (successive groupings of the three membranous structures of a Tubule between two terminal cisternae). The T tubules also encircle each sarcomere as they pass from one myofibril to the next. The T tubules can conduct impulses from the sarcolemma to each of the sarcomeres.

T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases | Skeletal Muscle | Full Text T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
Abstract
Introduction
T-tubule plasticity
Morphological aspects of triad biogenesis
Sarcoplasmic reticulum
Transverse tubule
Molecular mechanisms involved in T-tubule biogenesis and triad formation and maintenance
Table 1 Proteins implicated in triad organization, roles and associated human diseasesa
Caveolin 3
Amphiphysin 2 (BIN1)
Dysferlin
Mitsugumins
Junctophilins
Myotubularin
The RyR-DHPR complex
Conclusion
References
Acknowledgements
Author information
Affiliations
Corresponding author
Additional information
Competing interests
Authors' contributions
Authors’ original submitted files for images
Authors’ original file for figure 1
Authors’ original file for figure 2
Authors’ original file for figure 3
Authors’ original file for figure 4
Rights and permissions
About this article
Cite this article
Share this article
Keywords
 Moreover, this observation is specific to transverse tubule membranes, as no other intracellular membrane systems appear to be involved [ 12 ], probably due to the fact that their lumen connects to the extracellular space. Figure 2
Dynamics of T-tubule vacuolation produced by the efflux of glycerol. A single frog skeletal muscle fiber stained with a lipophilic fluorescence probe is shown. Shown are serial confocal microscopic images of the same fiber (a) 5 minutes, (b) 12 minutes and (c) 30 minutes after the fiber was transferred from a solution containing 110 mM glycerol to a solution without glycerol (reprinted from [ 10 ]; © 2001 with permission from Elsevier). Full size image
In addition to this artificial condition, this vacuolation phenomenon is observed upon muscle fatigue or diseases [ 10, 13 ]. Based on this plasticity and on the large membrane surface of the T-tubules network which corresponds to about 80% of the sarcolemma surface, several functions non-related to EC coupling are proposed for the T-tubules system [ 10, 13 ]. These include: i) water balance and regulation of cell volume, ii) recovery from muscle fatigue, iii) transport pathways including endocytosis, exocytosis and the penetration of foreign DNA. The molecular mechanisms involved in these processes are still to be investigated.

Moreover, this observation is specific to transverse tubule membranes, as no other intracellular membrane systems appear to be involved [ 12 ], probably due to the fact that their lumen connects to the extracellular space. Figure 2
Dynamics of T-tubule vacuolation produced by the efflux of glycerol. A single frog skeletal muscle fiber stained with a lipophilic fluorescence probe is shown. Shown are serial confocal microscopic images of the same fiber (a) 5 minutes, (b) 12 minutes and (c) 30 minutes after the fiber was transferred from a solution containing 110 mM glycerol to a solution without glycerol (reprinted from [ 10 ]; © 2001 with permission from Elsevier). Full size image
In addition to this artificial condition, this vacuolation phenomenon is observed upon muscle fatigue or diseases [ 10, 13 ]. Based on this plasticity and on the large membrane surface of the T-tubules network which corresponds to about 80% of the sarcolemma surface, several functions non-related to EC coupling are proposed for the T-tubules system [ 10, 13 ]. These include: i) water balance and regulation of cell volume, ii) recovery from muscle fatigue, iii) transport pathways including endocytosis, exocytosis and the penetration of foreign DNA. The molecular mechanisms involved in these processes are still to be investigated.

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 The calcium ATPase removes calcium from the cell actively, using energy derived from adenosine triphosphate (ATP). Detubulation
In order to study T-tubule function, T-tubules can be artificially uncoupled from the surface membrane using a technique known as detubulation. Chemicals such as glycerol or formamide (for skeletal and cardiac muscle respectively) can be added to the extracellular solution that surrounds the cells. These agents increase the osmolarity of the extracellular solution, causing the cells to shrink. When these agents are withdrawn, the cells rapidly expand and return to their normal size. This shrinkage and re-expansion of the cell causes T-tubules to detach from the surface membrane. Alternatively, the osmolarity of the extracellular solution can be decreased, using for example hypotonic saline, causing a tran

T-tubule - Wikipedia

The calcium ATPase removes calcium from the cell actively, using energy derived from adenosine triphosphate (ATP). Detubulation
In order to study T-tubule function, T-tubules can be artificially uncoupled from the surface membrane using a technique known as detubulation. Chemicals such as glycerol or formamide (for skeletal and cardiac muscle respectively) can be added to the extracellular solution that surrounds the cells. These agents increase the osmolarity of the extracellular solution, causing the cells to shrink. When these agents are withdrawn, the cells rapidly expand and return to their normal size. This shrinkage and re-expansion of the cell causes T-tubules to detach from the surface membrane. Alternatively, the osmolarity of the extracellular solution can be decreased, using for example hypotonic saline, causing a tran

Tubule - Wikipedia Tubule
Tubule
Examples of tubules
References
 It begins with a descending limb (comprising the proximal straight tubule and the thin tubule ), followed by the ascending limb (the distal straight tubule ), and ending at the distal convoluted tubule
Malpighian tubule: any of the excretory organs in insects that lie in the abdominal body cavity and empty into the junction between the midgut and hindgut
Mesonephric tubule: tubules comprising the mesonephros or temporary kidney of amniotes
Metanephric tubule: tubules comprising the permanent kidney of amniotes
Microtubule: a microscopically small tubule
Proximal convoluted tubule: the portion of the nephron immediately after the glomerulus
Renal tubule: the minute canals made up of basement membrane and lined with epithelium, composing the substance of the kidney and secreting, reabsorbing, collecting and conducting the urine. Include proximal convoluted, the nephron loop (containing the proximal straight tubule, descending and ascending thin, and the distal straight tubules) and the distal convoluted tubules
Seminiferous tubules: any of the numerous long convoluted tubules in the testis which are the sites where spermatozoa mature
T tubule: transverse intracellular tubules invaginating from the cell membrane and surrounding the myofibrils of the T system of skeletal and cardiac muscle, serving as a pathway for the spread of electrical excitation within a muscle cell
Trachea:

Tubule - Wikipedia

Tubule
Tubule
Examples of tubules
References

It begins with a descending limb (comprising the proximal straight tubule and the thin tubule ), followed by the ascending limb (the distal straight tubule ), and ending at the distal convoluted tubule
Malpighian tubule: any of the excretory organs in insects that lie in the abdominal body cavity and empty into the junction between the midgut and hindgut
Mesonephric tubule: tubules comprising the mesonephros or temporary kidney of amniotes
Metanephric tubule: tubules comprising the permanent kidney of amniotes
Microtubule: a microscopically small tubule
Proximal convoluted tubule: the portion of the nephron immediately after the glomerulus
Renal tubule: the minute canals made up of basement membrane and lined with epithelium, composing the substance of the kidney and secreting, reabsorbing, collecting and conducting the urine. Include proximal convoluted, the nephron loop (containing the proximal straight tubule, descending and ascending thin, and the distal straight tubules) and the distal convoluted tubules
Seminiferous tubules: any of the numerous long convoluted tubules in the testis which are the sites where spermatozoa mature
T tubule: transverse intracellular tubules invaginating from the cell membrane and surrounding the myofibrils of the T system of skeletal and cardiac muscle, serving as a pathway for the spread of electrical excitation within a muscle cell
Trachea:

T-tubule | Psychology Wiki | Fandom T-tubule
T-tubule
Contents
Structure
Excitation-contraction coupling
Detubulation
See also
External links
 Detubulation
It is possible to physically and functionally uncouple T-tubules from the surface membrane using a technique known as detubulation. This relies on osmotically active chemicals, such as glycerol (for skeletal muscle) or formamide (mainly for cardiac muscle ). Addition of these chemicals to the solution surrounding muscle cells causes the cells to shrink; when the chemical is withdrawn the cells rapidly expand before returning to their normal size. The rapid expansion is thought to cause the t-tubules to detach from the surface membrane, which reseals, and to reseal within the cell. This technique can be used to investigate the function of the t-tubules. There is some evidence that heart failure precipitates the loss of the T-tubule network, again indicating their importance. [ How to reference and link to summary or text]
See also
Muscle contraction
External links
Histology at Boston University 22502loa - "Ultrastructure of the Cell: cardiac muscle, intercalated disk "
Dictionary at eMedicine T+tubule
Physiology at MCG 2/2ch3/communic
This box: view • talk • edit
Histology:

T-tubule | Psychology Wiki | Fandom

Detubulation
It is possible to physically and functionally uncouple T-tubules from the surface membrane using a technique known as detubulation. This relies on osmotically active chemicals, such as glycerol (for skeletal muscle) or formamide (mainly for cardiac muscle ). Addition of these chemicals to the solution surrounding muscle cells causes the cells to shrink; when the chemical is withdrawn the cells rapidly expand before returning to their normal size. The rapid expansion is thought to cause the t-tubules to detach from the surface membrane, which reseals, and to reseal within the cell. This technique can be used to investigate the function of the t-tubules. There is some evidence that heart failure precipitates the loss of the T-tubule network, again indicating their importance. [ How to reference and link to summary or text]
See also
Muscle contraction
External links
Histology at Boston University 22502loa - "Ultrastructure of the Cell: cardiac muscle, intercalated disk "
Dictionary at eMedicine T+tubule
Physiology at MCG 2/2ch3/communic
This box: view • talk • edit
Histology:

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 Calcium control
As the space within the lumen of the T-tubule is continuous with the space that surrounds the cell (the extracellular space), ion concentrations between the two are very similar. However, due to the importance of the ions within the T-tubules (particularly calcium in cardiac muscle), it is very important that these concentrations remain relatively constant. As the T-tubules are very thin, they essentially trap the ions. This is important as, regardless of the ion concentrations elsewhere in the cell, T-tubules still have enough calcium ions to permit muscle contraction. Therefore, even if the concentration of calcium outside the cell falls ( hypocalcaemia ), the concentration of calcium within the T-tubule remains relatively constant, allowing cardiac contraction to continue. As well as T-tubules being a site for calcium entry into the cell, they are also a site for calcium removal. This is important as it means that calcium levels within the cell can be tightly controlled in a small area (i.e. between the T-tubule and sarcoplasmic reticulum, known as local control). Proteins such as the sodium-calcium exchanger and the sarcolemmal ATPase are located mainly in the T-tubule membrane. The sodium-calcium exchanger passively removes one calcium ion from the cell in exchange for three sodium ions. As a passive process it can therefore allow calcium to flow into or out of the cell depending on the combination of the relative concentrations of these ions and the voltage across the cell membrane (the electrochemical gradient ).

T-tubule - Wikipedia

Calcium control
As the space within the lumen of the T-tubule is continuous with the space that surrounds the cell (the extracellular space), ion concentrations between the two are very similar. However, due to the importance of the ions within the T-tubules (particularly calcium in cardiac muscle), it is very important that these concentrations remain relatively constant. As the T-tubules are very thin, they essentially trap the ions. This is important as, regardless of the ion concentrations elsewhere in the cell, T-tubules still have enough calcium ions to permit muscle contraction. Therefore, even if the concentration of calcium outside the cell falls ( hypocalcaemia ), the concentration of calcium within the T-tubule remains relatively constant, allowing cardiac contraction to continue. As well as T-tubules being a site for calcium entry into the cell, they are also a site for calcium removal. This is important as it means that calcium levels within the cell can be tightly controlled in a small area (i.e. between the T-tubule and sarcoplasmic reticulum, known as local control). Proteins such as the sodium-calcium exchanger and the sarcolemmal ATPase are located mainly in the T-tubule membrane. The sodium-calcium exchanger passively removes one calcium ion from the cell in exchange for three sodium ions. As a passive process it can therefore allow calcium to flow into or out of the cell depending on the combination of the relative concentrations of these ions and the voltage across the cell membrane (the electrochemical gradient ).

T-tubule - Wikipedia

T-tubule - Wikipedia

T-tubule - Wikipedia

T-tubule | Psychology Wiki | Fandom

Kidneys and Regulation of Water and Inorganic Ions - Biology Online Tutorial Kidneys and Regulation of Water and Inorganic Ions
Kidneys and Regulation of Water and Inorganic Ions
Table of Contents
Renal Functions
Structure of Kidneys and Urinary System
Basic Renal Processes
Glomerular filtration
Tubular reabsorption
Tubular secretion
Regulation
Renal clearance
Micturition
Basic renal processes for sodium and water
The Countercurrent Multiplier System
Renal Sodium Regulation
Renal Water Regulation
Potassium Regulation
Calcium Regulation
Hydrogen Ion Regulation
Bicarbonate Handling
Quiz
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The Dinosaurs
Cell Biology
Biological Viruses
Early Mammals on Earth
Respiration
Ecology & Biodiversity: New Zealand Flora & Fauna
 Tubule cells can synthesize glucose, ammonia, etc. and add it to blood as needed. It can catabolize peptides etc. and remove them from the body. Regulation
Hormones and neurotransmitters regulate channels and transporters. In order to excrete waste products, GFR must be large resulting in large filtered loads of substances. The primary role of the proximal tubule and loop of Henle is to reabsorb large quantities of substances. Such extensive reabsorption ensures that distal segments receive small amounts of substances and that their quantities in urine can be fine-tuned and regulated. Most homeostatic controls are therefore exerted on distal segments. Renal clearance
Renal clearance is the measure of the volume of plasma from which a substance is completely removed by kidneys per unit time.

Kidneys and Regulation of Water and Inorganic Ions - Biology Online Tutorial

Kidneys and Regulation of Water and Inorganic Ions
Kidneys and Regulation of Water and Inorganic Ions
Table of Contents
Renal Functions
Structure of Kidneys and Urinary System
Basic Renal Processes
Glomerular filtration
Tubular reabsorption
Tubular secretion
Regulation
Renal clearance
Micturition
Basic renal processes for sodium and water
The Countercurrent Multiplier System
Renal Sodium Regulation
Renal Water Regulation
Potassium Regulation
Calcium Regulation
Hydrogen Ion Regulation
Bicarbonate Handling
Quiz
More worksheets:
You will also like...
The Dinosaurs
Cell Biology
Biological Viruses
Early Mammals on Earth
Respiration
Ecology & Biodiversity: New Zealand Flora & Fauna

Tubule cells can synthesize glucose, ammonia, etc. and add it to blood as needed. It can catabolize peptides etc. and remove them from the body. Regulation
Hormones and neurotransmitters regulate channels and transporters. In order to excrete waste products, GFR must be large resulting in large filtered loads of substances. The primary role of the proximal tubule and loop of Henle is to reabsorb large quantities of substances. Such extensive reabsorption ensures that distal segments receive small amounts of substances and that their quantities in urine can be fine-tuned and regulated. Most homeostatic controls are therefore exerted on distal segments. Renal clearance
Renal clearance is the measure of the volume of plasma from which a substance is completely removed by kidneys per unit time.

Transverse Tubular System - an overview | ScienceDirect Topics Transverse Tubular System
Transverse Tubular System
Cardiovascular Physiology
Transverse Tubules
Ion Channel Trafficking
T-Tubules
Functional Organization of Vertebrate Plasma Membrane
2.4 T-tubules, physiology, and disease
Skeletal Muscle
T-tubules Are Surface Invaginations; the SR Is an Internal Membrane System
Cardiac Rhythm
4.2.1 Ca++ Regulation
Cardiovascular Physiology
Membrane Depolarization and Activator Calcium
Structure and Function of Calcium Release Channels
2 T Tubules and CRUs Revert to More Primitive Forms Under Pathological Conditions
Ion Channel Trafficking in the Heart
Ca V 1.2 Channel Trafficking in the Heart
Ca V 1.2 Forward Trafficking in Normal Heart Physiology
Ca V 1.2 Forward Trafficking in Heart Pathophysiology
Accessory Proteins Involved in Ca V 1.2 Targeted Delivery
T-Tubules and Ca V 1.2 Regulation in Normal Heart Physiology
T-Tubules and Ca V 1.2 Regulation in Heart Pathophysiology
Ca V 1.2 Internalization
Muscles
Coupling Action Potentials to Contraction
Skeletal Muscle Excitability
AIII Further Evidence that the T-Tubules Fire Na + -Dependent AP s
 From their data, the authors proposed that the dysfunction was due to a gain in the CICR process, implicating T-tubule structural disorganization in the pathophysiology of the failing myocyte. Follow-up studies also demonstrated that failing myocytes have increased Ca 2 + spark frequency, consistent with an uncoupling of the Ca 2 + release machinery and disruption of the T-tubules. It has also been argued that such a mechanism would produce only transient/short-lived changes in the size of the Ca 2 + transient and that it is more likely that a decrease in SR Ca 2 + content underlies the decrease in Ca 2 + transients. However, a reduction in T-tubule density could desynchronize Ca 2 + following electric stimulation, reducing peak Ca 2 + and slowing the time course. Although the loss of T-tubules cannot be completely responsible for the changes in Ca 2 + handling observed in heart failure, it is important to note that many of the functional changes exhibited in heart failure are observed in detubulation experiments, suggesting that the loss of T-tubules in heart failure may contribute to or exacerbate the phenotype observed in models of heart failure. View chapter Purchase book
Read full chapter
URL: https://www.sciencedirect.com/science/article/pii/B9780124170278000040
Skeletal Muscle
Clara Franzini-Armstrong, Andrew G. Engel, in Muscle, 2012
T-tubules Are Surface Invaginations; the SR Is an Internal Membrane System
T-tubules have a random, mostly longitudinal, disposition between the myofibrils during their initial formation but even at this stage they immediately form junctions with SR elements. The mature position of T-tubules within planes perpendicular to the fiber long axis ( Figure 53.1A,B) is acquired gradually during the coordinated differentiation of myofibrils and membrane system. This reorientation takes up to a month in chick and mouse muscles and the association of the whole triad assembly with the appropriate myofibril location drives it, perhaps via ankyrin and the giant protein obscurin.

Transverse Tubular System - an overview | ScienceDirect Topics

Transverse Tubular System
Transverse Tubular System
Cardiovascular Physiology
Transverse Tubules
Ion Channel Trafficking
T-Tubules
Functional Organization of Vertebrate Plasma Membrane
2.4 T-tubules, physiology, and disease
Skeletal Muscle
T-tubules Are Surface Invaginations; the SR Is an Internal Membrane System
Cardiac Rhythm
4.2.1 Ca++ Regulation
Cardiovascular Physiology
Membrane Depolarization and Activator Calcium
Structure and Function of Calcium Release Channels
2 T Tubules and CRUs Revert to More Primitive Forms Under Pathological Conditions
Ion Channel Trafficking in the Heart
Ca V 1.2 Channel Trafficking in the Heart
Ca V 1.2 Forward Trafficking in Normal Heart Physiology
Ca V 1.2 Forward Trafficking in Heart Pathophysiology
Accessory Proteins Involved in Ca V 1.2 Targeted Delivery
T-Tubules and Ca V 1.2 Regulation in Normal Heart Physiology
T-Tubules and Ca V 1.2 Regulation in Heart Pathophysiology
Ca V 1.2 Internalization
Muscles
Coupling Action Potentials to Contraction
Skeletal Muscle Excitability
AIII Further Evidence that the T-Tubules Fire Na + -Dependent AP s

 This reverses the normal imbalance of charged particles and is referred to as depolarisation. One region of membrane depolarises adjacent regions, and the resulting wave of depolarisation then spreads along the cell membrane.[8] The polarisation of the membrane is restored as potassium ions flow back across the membrane from the inside to the outside of the cell. In cardiac muscle cells, as the action potential passes down the T-tubules it activates L-type calcium channels in the T-tubular membrane. Activation of the L-type calcium channel  allows calcium to pass into the cell. T-tubules contain a higher concentration of L-type calcium channels than the rest of the sarcolemma and therefore the majority of the calcium that enters the cell occurs via T-tubules.[9] This calcium binds to and activates a receptor, known as a ryanodine receptor, located on the cell's own internal calcium store, the sarcoplasmic reticulum. Activation of the ryanodine receptor causes calcium to be released from the sarcoplasmic reticulum, causing the muscle cell to contract.[10] In skeletal musclecells, however, the L-type calcium channel is directly attached to the ryanodine receptor on the sarcoplasmic reticulum allowing activation of the ryanodine receptor directly without the need for an influx of calcium. [ 11]
The importance of T-tubules is not solely due to their concentration of L-type calcium channels, but lies also within their ability to synchronise calcium release within the cell. The rapid spread of the action potential along the T-tubule network activates all of the L-type calcium channels near-simultaneously. As T-tubules bring the sarcolemma very close to the sarcoplasmic reticulum at all regions throughout the cell,  calcium can then be released from the sarcoplasmic reticulum across the whole cell at the same time. This synchronisation of calcium release allows muscle cells to contract more forcefully.[12] In cells lacking T-tubules such as smooth muscle cells, diseased cardiomyocytes, or muscle cells in which T-tubules have been artificially removed, the calcium that enters at the sarcolemma has to diffuse gradually throughout the cell, activating the ryanodine receptors much more slowly as a wave of calcium leading to less forceful contraction. [

Nephron - Structure, Functions and Types of Nephron Nephron- Function Of Renal Tubules
Nephron- Function Of Renal Tubules
Nephron Definition
Table of Contents
What is Nephron?
Structure of Nephron
Renal Tubule
Collecting Duct
Renal Corpuscle
Types of Nephron
Functions of Nephron
Conclusion
Frequently Asked Questions
What is the main function of a nephron?
How does a nephron filter blood?
What are the two main parts of a nephron structure?
Where are the nephrons located?
What is the cup-shaped structure surrounding the renal corpuscle called?
 Renal Tubule
Renal Corpuscle
Renal Tubule
The renal tubule is a long and convoluted structure that emerges from the glomerulus and can be divided into three parts based on function. The first part is called the proximal convoluted tubule (PCT) due to its proximity to the glomerulus; it stays in the renal cortex. The second part is called the loop of Henle, or nephritic loop because it forms a loop (with descending and ascending limbs) that goes through the renal medulla. The third part of the renal tubule is called the distal convoluted tubule (DCT) and this part is also restricted to the renal cortex. The capillaries of the glomerulus are enclosed by a cup-like structure called Bowman’s capsule. This structure extends to form highly coiled tubules called PCT. PCT continues to form the loop of Henle which ascends to DCT, which in turn opens into the collecting duct. The major function of tubules is reabsorption and the process can either be through active transport or passive transport. In addition, secretions by tubules help in the urine formation without affecting the electrolyte balance of the body.

Nephron - Structure, Functions and Types of Nephron

Nephron- Function Of Renal Tubules
Nephron- Function Of Renal Tubules
Nephron Definition
Table of Contents
What is Nephron?
Structure of Nephron
Renal Tubule
Collecting Duct
Renal Corpuscle
Types of Nephron
Functions of Nephron
Conclusion
Frequently Asked Questions
What is the main function of a nephron?
How does a nephron filter blood?
What are the two main parts of a nephron structure?
Where are the nephrons located?
What is the cup-shaped structure surrounding the renal corpuscle called?

Renal Tubule
Renal Corpuscle
Renal Tubule
The renal tubule is a long and convoluted structure that emerges from the glomerulus and can be divided into three parts based on function. The first part is called the proximal convoluted tubule (PCT) due to its proximity to the glomerulus; it stays in the renal cortex. The second part is called the loop of Henle, or nephritic loop because it forms a loop (with descending and ascending limbs) that goes through the renal medulla. The third part of the renal tubule is called the distal convoluted tubule (DCT) and this part is also restricted to the renal cortex. The capillaries of the glomerulus are enclosed by a cup-like structure called Bowman’s capsule. This structure extends to form highly coiled tubules called PCT. PCT continues to form the loop of Henle which ascends to DCT, which in turn opens into the collecting duct. The major function of tubules is reabsorption and the process can either be through active transport or passive transport. In addition, secretions by tubules help in the urine formation without affecting the electrolyte balance of the body.

Skeletal muscle physiology | BJA Education | Oxford Academic Skeletal muscle physiology
Skeletal muscle physiology
Published:
Subject
Issue Section:
Key points
Electrical events in muscle contraction
Excitation-contraction coupling
Contractile structures
Force transmission
Determinants of force of contraction
Summation
Recruitment
Energy for contraction
Muscle fibre-types
Further reading
 Skeletal muscle sarcolemma is characterized by invaginations called transverse- or t-tubules that run perpendicular to the surface of the cell deep into its body. By passing down the t-tubular membrane, the action potential is carried to the structures responsible for transducing an electrical into a chemical signal that will trigger activation of the contractile elements. Excitation-contraction coupling
This term encompasses the processes by which the surface membrane action potential leads to interaction of the intracellular contractile elements. The t-tubular membrane contains the highest density in the body of binding sites for dihydropyridine compounds, such as nifedipine. This finding was initially assumed to suggest that arrival of the action potential in the t-tubules opened voltage-gated Ca 2+ channels. We now know that, although the t-tubular dihydropyridine receptors show marked amino acid homology with L-type voltage gated Ca 2+ channels of other tissues, they do not function as Ca 2+ channels. Their role in skeletal muscle is that of voltage sensors. When the action potential arrives in the t-tubule, the change in membrane potential leads to a conformational change in the α-subunit of the dihydropyridine receptor. This subunit consists of four transmembrane domains each of six segments ( Fig. 1 ).

Skeletal muscle physiology | BJA Education | Oxford Academic

Skeletal muscle physiology
Skeletal muscle physiology
Published:
Subject
Issue Section:
Key points
Electrical events in muscle contraction
Excitation-contraction coupling
Contractile structures
Force transmission
Determinants of force of contraction
Summation
Recruitment
Energy for contraction
Muscle fibre-types
Further reading

Skeletal muscle sarcolemma is characterized by invaginations called transverse- or t-tubules that run perpendicular to the surface of the cell deep into its body. By passing down the t-tubular membrane, the action potential is carried to the structures responsible for transducing an electrical into a chemical signal that will trigger activation of the contractile elements. Excitation-contraction coupling
This term encompasses the processes by which the surface membrane action potential leads to interaction of the intracellular contractile elements. The t-tubular membrane contains the highest density in the body of binding sites for dihydropyridine compounds, such as nifedipine. This finding was initially assumed to suggest that arrival of the action potential in the t-tubules opened voltage-gated Ca 2+ channels. We now know that, although the t-tubular dihydropyridine receptors show marked amino acid homology with L-type voltage gated Ca 2+ channels of other tissues, they do not function as Ca 2+ channels. Their role in skeletal muscle is that of voltage sensors. When the action potential arrives in the t-tubule, the change in membrane potential leads to a conformational change in the α-subunit of the dihydropyridine receptor. This subunit consists of four transmembrane domains each of six segments ( Fig. 1 ).

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 The calcium ATPase removes calcium from the cell actively, using energy derived from adenosine triphosphate (ATP). Detubulation
In order to study T-tubule function, T-tubules can be artificially uncoupled from the surface membrane using a technique known as detubulation. Chemicals such as glycerol or formamide (for skeletal and cardiac muscle respectively) can be added to the extracellular solution that surrounds the cells. These agents increase the osmolarity of the extracellular solution, causing the cells to shrink. When these agents are withdrawn, the cells rapidly expand and return to their normal size. This shrinkage and re-expansion of the cell causes T-tubules to detach from the surface membrane. Alternatively, the osmolarity of the extracellular solution can be decreased, using f

T-tubule - Wikipedia

The calcium ATPase removes calcium from the cell actively, using energy derived from adenosine triphosphate (ATP). Detubulation
In order to study T-tubule function, T-tubules can be artificially uncoupled from the surface membrane using a technique known as detubulation. Chemicals such as glycerol or formamide (for skeletal and cardiac muscle respectively) can be added to the extracellular solution that surrounds the cells. These agents increase the osmolarity of the extracellular solution, causing the cells to shrink. When these agents are withdrawn, the cells rapidly expand and return to their normal size. This shrinkage and re-expansion of the cell causes T-tubules to detach from the surface membrane. Alternatively, the osmolarity of the extracellular solution can be decreased, using f

Transverse Tubular System - an overview | ScienceDirect Topics Transverse Tubular System
Transverse Tubular System
Cardiovascular Physiology
Transverse Tubules
Ion Channel Trafficking
T-Tubules
Functional Organization of Vertebrate Plasma Membrane
2.4 T-tubules, physiology, and disease
Skeletal Muscle
T-tubules Are Surface Invaginations; the SR Is an Internal Membrane System
Cardiac Rhythm
4.2.1 Ca++ Regulation
Cardiovascular Physiology
Membrane Depolarization and Activator Calcium
Structure and Function of Calcium Release Channels
2 T Tubules and CRUs Revert to More Primitive Forms Under Pathological Conditions
Ion Channel Trafficking in the Heart
Ca V 1.2 Channel Trafficking in the Heart
Ca V 1.2 Forward Trafficking in Normal Heart Physiology
Ca V 1.2 Forward Trafficking in Heart Pathophysiology
Accessory Proteins Involved in Ca V 1.2 Targeted Delivery
T-Tubules and Ca V 1.2 Regulation in Normal Heart Physiology
T-Tubules and Ca V 1.2 Regulation in Heart Pathophysiology
Ca V 1.2 Internalization
Muscles
Coupling Action Potentials to Contraction
Skeletal Muscle Excitability
AIII Further Evidence that the T-Tubules Fire Na + -Dependent AP s
 Transverse Tubular System - an overview | ScienceDirect Topics
Transverse Tubular System
Download as PDF
About this page
Cardiovascular Physiology
Duncan de Souza, ... Victor C. Baum, in Smith's Anesthesia for Infants and Children (Eighth Edition), 2011
Transverse Tubules
Transverse tubules, or T-tubules, invaginations of the sarcolemma in ventricular, but not atrial, myocardial cells have been mentioned in the discussion of myocardial performance. They allow transmission of the action potential, with its attendant ion shifts, to all parts of the cell, which allows rapid activation of the entire cell. T-tubules are thus a required component of larger cells ( Gotoh, 1983 ). Maturation of T-tubules is associated with the increased size of mature myocardial cells, with the sarcolemmal calcium channels further from the contractile apparatus. Species that have a relatively mature myocardium at birth have well-developed T-tubules at birth, whereas animals with immature myocardium at birth do not. T-tubules first appear at about 30 weeks gestation in humans ( Kim et al., 1992 ). View chapter Purchase book
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URL: https://www.sciencedirect.com/science/article/pii/B9780323066129000043
Ion Channel Trafficking
T.T. Hong, R.M. Shaw, in Ion Channels in Health and Disease, 2016
T-Tubules
T-tubule membrane is associated with a unique set of ion channels supported by membrane structural subdomains. 23 Immunocytochemistry and patch clamp data indicate that 80% of the sarcolemma LTCCs are concentrated at T-tubules.

Transverse Tubular System - an overview | ScienceDirect Topics
Transverse Tubular System
Download as PDF
About this page
Cardiovascular Physiology
Duncan de Souza, ... Victor C. Baum, in Smith's Anesthesia for Infants and Children (Eighth Edition), 2011
Transverse Tubules
Transverse tubules, or T-tubules, invaginations of the sarcolemma in ventricular, but not atrial, myocardial cells have been mentioned in the discussion of myocardial performance. They allow transmission of the action potential, with its attendant ion shifts, to all parts of the cell, which allows rapid activation of the entire cell. T-tubules are thus a required component of larger cells ( Gotoh, 1983 ). Maturation of T-tubules is associated with the increased size of mature myocardial cells, with the sarcolemmal calcium channels further from the contractile apparatus. Species that have a relatively mature myocardium at birth have well-developed T-tubules at birth, whereas animals with immature myocardium at birth do not. T-tubules first appear at about 30 weeks gestation in humans ( Kim et al., 1992 ). View chapter Purchase book
Read full chapter
URL: https://www.sciencedirect.com/science/article/pii/B9780323066129000043
Ion Channel Trafficking
T.T. Hong, R.M. Shaw, in Ion Channels in Health and Disease, 2016
T-Tubules
T-tubule membrane is associated with a unique set of ion channels supported by membrane structural subdomains. 23 Immunocytochemistry and patch clamp data indicate that 80% of the sarcolemma LTCCs are concentrated at T-tubules.

T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases | Skeletal Muscle | Full Text T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
Abstract
Introduction
T-tubule plasticity
Morphological aspects of triad biogenesis
Sarcoplasmic reticulum
Transverse tubule
Molecular mechanisms involved in T-tubule biogenesis and triad formation and maintenance
Table 1 Proteins implicated in triad organization, roles and associated human diseasesa
Caveolin 3
Amphiphysin 2 (BIN1)
Dysferlin
Mitsugumins
Junctophilins
Myotubularin
The RyR-DHPR complex
Conclusion
References
Acknowledgements
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Corresponding author
Additional information
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Authors’ original file for figure 1
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 In cardiac myofiber, RyR2-mediated calcium release is induced by extracellular calcium entry via DHPR in a mechanism called calcium-induced calcium release (CICR) [ 8 ]. Moreover, in fibers of small diameter, such as the body muscles of Amphioxus, peripheral couplings between SR and the plasmalemma have similar function to triads. In addition, all differentiating muscle fibers pass through a stage where T-tubules are not present and EC coupling is mediated by such peripheral couplings. In this review, we will focus on the molecular mechanisms underlying T-tubules biogenesis and triad formation specifically in skeletal muscle. Triad defects linked to human monogenic diseases will also be highlighted. T-tubule plasticity
The T-tubule membrane possesses a high plasticity which provides the stability required during muscle contraction, and facilitates repair upon damage. In addition to its principal function in EC coupling, the plasticity of T-tubules confers to this system non-related EC functions. It has been reported that the treatment of isolated muscle fibers with glycerol efflux-influx or with other low molecular weight nonelectrolytes (such as sugars) physically affects T-tubules morphology. Such osmotic shock can convert the T-tubule network into many membrane-bound vacuoles, which can either remain interconnected by normal T-tubules, or become separated (Figure 2) [ 9, 10 ]. Surprisingly, this vacuolation which results in 5-15 fold increase in the relative volume of T-tubule system is reversed spontaneously [ 11, 12 ].

In cardiac myofiber, RyR2-mediated calcium release is induced by extracellular calcium entry via DHPR in a mechanism called calcium-induced calcium release (CICR) [ 8 ]. Moreover, in fibers of small diameter, such as the body muscles of Amphioxus, peripheral couplings between SR and the plasmalemma have similar function to triads. In addition, all differentiating muscle fibers pass through a stage where T-tubules are not present and EC coupling is mediated by such peripheral couplings. In this review, we will focus on the molecular mechanisms underlying T-tubules biogenesis and triad formation specifically in skeletal muscle. Triad defects linked to human monogenic diseases will also be highlighted. T-tubule plasticity
The T-tubule membrane possesses a high plasticity which provides the stability required during muscle contraction, and facilitates repair upon damage. In addition to its principal function in EC coupling, the plasticity of T-tubules confers to this system non-related EC functions. It has been reported that the treatment of isolated muscle fibers with glycerol efflux-influx or with other low molecular weight nonelectrolytes (such as sugars) physically affects T-tubules morphology. Such osmotic shock can convert the T-tubule network into many membrane-bound vacuoles, which can either remain interconnected by normal T-tubules, or become separated (Figure 2) [ 9, 10 ]. Surprisingly, this vacuolation which results in 5-15 fold increase in the relative volume of T-tubule system is reversed spontaneously [ 11, 12 ].

Transverse Tubular System - an overview | ScienceDirect Topics Transverse Tubular System
Transverse Tubular System
Cardiovascular Physiology
Transverse Tubules
Ion Channel Trafficking
T-Tubules
Functional Organization of Vertebrate Plasma Membrane
2.4 T-tubules, physiology, and disease
Skeletal Muscle
T-tubules Are Surface Invaginations; the SR Is an Internal Membrane System
Cardiac Rhythm
4.2.1 Ca++ Regulation
Cardiovascular Physiology
Membrane Depolarization and Activator Calcium
Structure and Function of Calcium Release Channels
2 T Tubules and CRUs Revert to More Primitive Forms Under Pathological Conditions
Ion Channel Trafficking in the Heart
Ca V 1.2 Channel Trafficking in the Heart
Ca V 1.2 Forward Trafficking in Normal Heart Physiology
Ca V 1.2 Forward Trafficking in Heart Pathophysiology
Accessory Proteins Involved in Ca V 1.2 Targeted Delivery
T-Tubules and Ca V 1.2 Regulation in Normal Heart Physiology
T-Tubules and Ca V 1.2 Regulation in Heart Pathophysiology
Ca V 1.2 Internalization
Muscles
Coupling Action Potentials to Contraction
Skeletal Muscle Excitability
AIII Further Evidence that the T-Tubules Fire Na + -Dependent AP s
 Therefore, BIN1-like membrane scaffold proteins may help localize particular pools of ion channel proteins to membrane subdomains for compartmentalized regulation of ion channel activity and function. Similarly, ankyrin B can play a role similar to BIN1 in clustering NCX/NKA/InsP3 complex to microdomains distinct from the dyads. 71 Integrity of NCX/NKA/InsP3 complex is critical in removing calcium from the clefts between T-tubule surface and SR membrane, facilitating calcium decline during relaxation. Therefore, intracellular calcium equilibrium can be achieved by balancing calcium entry through LTCC clustered at BIN1-membrane and calcium removal by NCX anchored at ankyrin B-induced membrane. View chapter Purchase book
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URL: https://www.sciencedirect.com/science/article/pii/B9780128020029000029
Functional Organization of Vertebrate Plasma Membrane
Crystal F. Kline, Peter J. Mohler, in Current Topics in Membranes, 2013
2.4 T-tubules, physiology, and disease
T-tubule structure and function is severely compromised in human heart failure and in small and large animal models of cardiovascular disease ( Balijepalli et al., 2003; Louch et al., 2004 ). Animal models of heart failure exhibit T-tubule disorganization that appears to result from various myocardial insults, including sustained tachycardia ( Balijepalli et al.,

Therefore, BIN1-like membrane scaffold proteins may help localize particular pools of ion channel proteins to membrane subdomains for compartmentalized regulation of ion channel activity and function. Similarly, ankyrin B can play a role similar to BIN1 in clustering NCX/NKA/InsP3 complex to microdomains distinct from the dyads. 71 Integrity of NCX/NKA/InsP3 complex is critical in removing calcium from the clefts between T-tubule surface and SR membrane, facilitating calcium decline during relaxation. Therefore, intracellular calcium equilibrium can be achieved by balancing calcium entry through LTCC clustered at BIN1-membrane and calcium removal by NCX anchored at ankyrin B-induced membrane. View chapter Purchase book
Read full chapter
URL: https://www.sciencedirect.com/science/article/pii/B9780128020029000029
Functional Organization of Vertebrate Plasma Membrane
Crystal F. Kline, Peter J. Mohler, in Current Topics in Membranes, 2013
2.4 T-tubules, physiology, and disease
T-tubule structure and function is severely compromised in human heart failure and in small and large animal models of cardiovascular disease ( Balijepalli et al., 2003; Louch et al., 2004 ). Animal models of heart failure exhibit T-tubule disorganization that appears to result from various myocardial insults, including sustained tachycardia ( Balijepalli et al.,

Skeletal muscle tissue: Histology | Kenhub Skeletal muscle histology
Skeletal muscle histology: want to learn more about it?
Skeletal muscle histology
Contents
Terminology
Skeletal muscle fibers
Structure
Types
Sarcomeres
Sarcoplasmic structures
Accessory proteins
Neuromuscular junction
Contraction
Control of the skeletal muscle contraction
Golgi tendon organs
Muscle spindle fibers
Clinical correlations
Muscular dystrophy
Actin aggregate myopathy
Myotubular (centronuclear) myopathies
Skeletal muscle histology: want to learn more about it?
 It is made up of a network of tubules with a reservoir at either end. This reservoir is referred to as the terminal cisterna. Terminal cisterna - enlarged regions on either end of the sarcoplasmic reticulum. The terminal cisternae sequester calcium to be used in the contraction cycle. There is a terminal cisterna on either side of a t-tubule. All together they are called a triad. T-tubules - also called transverse tubules. The t-tubules are pits along the surface of the muscle cells. Their walls are continuous with the sarcolemma, meaning the internal surface of the t-tubule is exposed to the extracellular matrix. The t-tubules are responsible for moving action potentials to the inner region of the muscle cell.

Skeletal muscle tissue: Histology | Kenhub

Skeletal muscle histology
Skeletal muscle histology: want to learn more about it?
Skeletal muscle histology
Contents
Terminology
Skeletal muscle fibers
Structure
Types
Sarcomeres
Sarcoplasmic structures
Accessory proteins
Neuromuscular junction
Contraction
Control of the skeletal muscle contraction
Golgi tendon organs
Muscle spindle fibers
Clinical correlations
Muscular dystrophy
Actin aggregate myopathy
Myotubular (centronuclear) myopathies
Skeletal muscle histology: want to learn more about it?

It is made up of a network of tubules with a reservoir at either end. This reservoir is referred to as the terminal cisterna. Terminal cisterna - enlarged regions on either end of the sarcoplasmic reticulum. The terminal cisternae sequester calcium to be used in the contraction cycle. There is a terminal cisterna on either side of a t-tubule. All together they are called a triad. T-tubules - also called transverse tubules. The t-tubules are pits along the surface of the muscle cells. Their walls are continuous with the sarcolemma, meaning the internal surface of the t-tubule is exposed to the extracellular matrix. The t-tubules are responsible for moving action potentials to the inner region of the muscle cell.

 12]
As the T-tubules are the primary location for excitation-contraction coupling, the ion channels and proteins involved in this process are concentrated here - there are 3 times as many L-type calcium channels located within the T-tubule membrane compared to the rest of the sarcolemma. Furthermore, beta adrenoceptors are also highly concentrated in the T-tubular membrane,[13]and their stimulation increases calcium release from the sarcoplasmic reticulum. [ 14]
Calcium control[edit]
As the space within the lumen of the T-tubule is continuous with the space that surrounds the cell (the extracellular space), ion concentrations between the two are very similar. However, due to the importance of the ions within the T-tubules (particularly calcium in cardiac muscle), it is very important that these concentrations remain relatively constant. As the T-tubules are very thin, they essentially trap the ions. This is important as, regardless of the ion concentrations elsewhere in the cell, T-tubules still have enough calcium ions to permit muscle contraction. Therefore, even if the concentration of calcium outside the cell falls (hypocalcaemia), the concentration of calcium within the  T-tubule remains relatively constant, allowing cardiac contraction to continue. [ 5]
As well as T-tubules being a site for calcium entry into the cell, they are also a site for calcium removal. This is important as it means that calcium levels within the cell can be tightly controlled in a small area (i.e. between the T-tubule and sarcoplasmic reticulum, known as local control).[15] Proteins such as the sodium-calcium exchanger and the sarcolemmal ATPase are located mainly in the T-tubule membrane.[5] The sodium-calcium exchanger passively removes one calcium ion from the cell in exchange for three sodium ions. As a passive process it can therefore allow calcium to flow into or out of the cell depending on the combination of the relative concentrations of these ions and the voltage across the cell membrane (the electrochemical gradient).[8] The calcium ATPase removes calcium from the cell actively, using energy derived from  adenosine triphosphate(ATP). [

T-tubule - Wikipedia T-tubule
T-tubule
Contents
Structure
Regulators
Function
Excitation-contraction coupling
Calcium control
Detubulation
History
Clinical significance
See also
References
 This calcium binds to and activates a receptor, known as a ryanodine receptor, located on the cell's own internal calcium store, the sarcoplasmic reticulum. Activation of the ryanodine receptor causes calcium to be released from the sarcoplasmic reticulum, causing the muscle cell to contract. In skeletal muscle cells, however, the L-type calcium channel is directly attached to the ryanodine receptor on the sarcoplasmic reticulum allowing activation of the ryanodine receptor directly without the need for an influx of calcium. The importance of T-tubules is not solely due to their concentration of L-type calcium channels, but lies also within their ability to synchronise calcium release within the cell. The rapid spread of the action potential along the T-tubule network activates all of the L-type calcium channels near-simultaneously. As T-tubules bring the sarcolemma very close to the sarcoplasmic reticulum at all regions throughout the cell, calcium can then be released from the sarcoplasmic reticulum across the whole cell at the same time. This synchronisation of calcium release allows muscle cells to contract more forcefully. In cells lacking T-tubules such as smooth muscle cells, diseased cardiomyocytes, or muscle cells in which T-tubules have been artificially removed, the calcium that enters at the sarcolemma has to diffuse gradually throughout the cell, activating the ryanodine receptors much more slowly as a wave of calcium leading to less forceful contraction. As the T-tubules are the primary location for excitation-contraction coupling, the ion channels and proteins involved in this process are concentrated here - there are 3 times as many L-type calcium channels located within the T-tubule membrane compared to the rest of the sarcolemma. Furthermore, beta adrenoceptors are also highly concentrated in the T-tubular membrane, and their stimulation increases calcium release from the sarcoplasmic reticulum.

T-tubule - Wikipedia

T-tubule - Wikipedia

 Activation of the ryanodine receptor causes calcium to be released from the sarcoplasmic reticulum, causing the muscle cell to contract.[10] In skeletal musclecells, however, the L-type calcium channel is directly attached to the ryanodine receptor on the sarcoplasmic reticulum allowing activation of the ryanodine receptor directly without the need for an influx of calcium. [ 11]
The importance of T-tubules is not solely due to their concentration of L-type calcium channels, but lies also within their ability to synchronise calcium release within the cell. The rapid spread of the action potential along the T-tubule network activates all of the L-type calcium channels near-simultaneously. As T-tubules bring the sarcolemma very close to the sarcoplasmic reticulum at all regions throughout the cell,  calcium can then be released from the sarcoplasmic reticulum across the whole cell at the same time. This synchronisation of calcium release allows muscle cells to contract more forcefully.[12] In cells lacking T-tubules such as smooth muscle cells, diseased cardiomyocytes, or muscle cells in which T-tubules have been artificially removed, the calcium that enters at the sarcolemma has to diffuse gradually throughout the cell, activating the ryanodine receptors much more slowly as a wave of calcium leading to less forceful contraction. [ 12]
As the T-tubules are the primary location for excitation-contraction coupling, the ion channels and proteins involved in this process are concentrated here - there are 3 times as many L-type calcium channels located within the T-tubule membrane compared to the rest of the sarcolemma. Furthermore, beta adrenoceptors are also highly concentrated in the T-tubular membrane,[13]and their stimulation increases calcium release from the sarcoplasmic reticulum. [ 14]
Calcium control[edit]
As the space within the lumen of the T-tubule is continuous with the space that surrounds the cell (the extracellular space), ion concentrations between the two are very similar. However, due to the importance of the ions within the T-tubules (particularly calcium in cardiac muscle), it is very important that these concentrations remain relatively constant. As the T-tubules are very thin, they essentially trap the ions.

Cardiac T-Tubule Microanatomy and Function | Physiological Reviews Cardiac T-Tubule Microanatomy and Function
Cardiac T-Tubule Microanatomy and Function
Abstract
I. INTRODUCTION
II. CARDIAC T-TUBULE STRUCTURE
A. History of T-Tubule Structure-Related Research
B. Gross Morphology and Geometry
C. Membrane Ultrastructure and Microdomains
1. cBIN1 microfolds: microdomains supporting LTCC-RyR dyads
2. Caveoli (caveolae): β-AR/LTCC signaling hubs
3. Ankyrin B microdomains: NCX/NKA/InsP 3 macromolecular complex
D. Peri-Membrane Cytoskeleton Scaffolds at Cardiac T-Tubules
1. Actin filaments, tropomyosin, and N-WASP
2. Costamere complex and t-tubule membrane-associated scaffolds
3. Myofilament structural proteins
E. Variation in Cardiac T-Tubule Geometry
III. TRANSMEMBRANE PROTEINS AT CARDIAC T-TUBULES
A. Ion Handling Proteins (Channels/Transporters/Pumps)
1. Ca 2+ handling proteins
2. Na + handling proteins
3. K + handling proteins
B. Signaling Molecules at Cardiac T-Tubules
IV. FUNCTION OF CARDIAC T-TUBULES
A. Dyad and EC Coupling
1. LTCC trafficking and clustering to dyads through BIN1
2. RyR recruitment to dyads through BIN1
3. Junctophilin-2 in t-tubule-jSR junctional membrane complex formation
B. Ion Diffusion and Membrane Excitability
C. Other Microdomain-Related Functions
V. LIFE CYCLE OF CARDIAC T-TUBULES
A. Membrane Biogenesis, Maintenance, and Turnover
B. Ion Channel Trafficking and Half-Life
VI. ALTERATION OF T-TUBULE STRUCTURE AND FUNCTION IN HEART FAILURE
VII. CONCLUSIONS
GRANTS
DISCLOSURES
Acknowledgments
 Cardiac t-tubules are also substantially remodeled during heart failure ( 38, 52, 89, 97, 98, 108, 130 - 134, 180, 202, 207, 208, 220, 224, 230 ). In addition to the observed loss and gross diminishment of the t-tubule network, protein components at t-tubules including ion channels and signaling molecules are reported to be either reduced at the t-tubule surface or redistributed elsewhere to non-t-tubule sarcolemma ( 20, 93, 134 ). Loss of complex t-tubules in heart failure not only causes impaired contractile function due to disrupted dyads and the resultant EC uncoupling, but also alters local concentration gradients and increases susceptibility to ventricular arrhythmia ( 66, 85, 91, 157, 163, 179, 181, 213 ). The molecular and cellular mechanisms of t-tubule remodeling in failing cardiomyocytes, in particular the alterations in t-tubule membrane ultrastructure and subdomains, is an active area of interest among cardiac biologists. This review summarizes and cites the current knowledge of cardiac t-tubule morphology, structure, components, and physiological functions, with emphasis on the organization and function of microdomains within t-tubules. The dynamic life cycle of t-tubule membrane and protein components, as well as the current understanding of microdomain remodeling in heart failure, will also be discussed. II. CARDIAC T-TUBULE STRUCTURE
A. History of T-Tubule Structure-Related Research
Striated muscle cells have a unique membrane system, the transverse-tubules (t-tubules), or more precisely, the transverse-axial-tubular system. T-tubules are sarcolemma invaginations formed by membrane tubules that are primarily perpendicular to myocyte longitudinal edges. These membrane tubular structures are interconnected in a complex network.

Cardiac t-tubules are also substantially remodeled during heart failure ( 38, 52, 89, 97, 98, 108, 130 - 134, 180, 202, 207, 208, 220, 224, 230 ). In addition to the observed loss and gross diminishment of the t-tubule network, protein components at t-tubules including ion channels and signaling molecules are reported to be either reduced at the t-tubule surface or redistributed elsewhere to non-t-tubule sarcolemma ( 20, 93, 134 ). Loss of complex t-tubules in heart failure not only causes impaired contractile function due to disrupted dyads and the resultant EC uncoupling, but also alters local concentration gradients and increases susceptibility to ventricular arrhythmia ( 66, 85, 91, 157, 163, 179, 181, 213 ). The molecular and cellular mechanisms of t-tubule remodeling in failing cardiomyocytes, in particular the alterations in t-tubule membrane ultrastructure and subdomains, is an active area of interest among cardiac biologists. This review summarizes and cites the current knowledge of cardiac t-tubule morphology, structure, components, and physiological functions, with emphasis on the organization and function of microdomains within t-tubules. The dynamic life cycle of t-tubule membrane and protein components, as well as the current understanding of microdomain remodeling in heart failure, will also be discussed. II. CARDIAC T-TUBULE STRUCTURE
A. History of T-Tubule Structure-Related Research
Striated muscle cells have a unique membrane system, the transverse-tubules (t-tubules), or more precisely, the transverse-axial-tubular system. T-tubules are sarcolemma invaginations formed by membrane tubules that are primarily perpendicular to myocyte longitudinal edges. These membrane tubular structures are interconnected in a complex network.

It is the segment between 2 successive Z-Lines. What are the T tubules and what is their chief function? - T tubules are transverse tubules formed by inward extensions of the sarcolemma. -Function is to allow electrical impulses traveling along the sarcomere to move deeper into the cell. What do impulses from the T tubules do to the sarcoplasmic reticulum? - It stimulates the membranes forming the sacs of sarcoplasmic reticulum. - This stimulation causes the SR to release its stored calcium ions. What types of protein are found in thick and thin myofilaments? Where is each type of protein found? Thick myofilaments:

It is the segment between 2 successive Z-Lines. What are the T tubules and what is their chief function? - T tubules are transverse tubules formed by inward extensions of the sarcolemma. -Function is to allow electrical impulses traveling along the sarcomere to move deeper into the cell. What do impulses from the T tubules do to the sarcoplasmic reticulum? - It stimulates the membranes forming the sacs of sarcoplasmic reticulum. - This stimulation causes the SR to release its stored calcium ions. What types of protein are found in thick and thin myofilaments? Where is each type of protein found? Thick myofilaments:

Cardiac excitation-contraction coupling - Osmosis Cardiac excitation-contraction coupling
Cardiac excitation-contraction coupling
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Cardiac excitation-contraction coupling
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Cardiac excitation-contraction coupling
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 Another feature of cardiomyocytes are passageways called transverse tubules, or T-tubules. T-tubules are extensions of the outside environment. They increase the surface area of the cardiomyocyte and they look like the letter T, so it’s easy to remember their name. Think of a large walk-through aquarium: you can walk through tunnels and look at the sea creatures all around you, but you’re not in the water with them. Finally, there’s the sarcoplasmic reticulum, which is an organelle that stores intracellular calcium, the calcium that is sequestered inside the cell. When a depolarization wavefront hits a cardiomyocyte, a few calcium ions flow through gap junctions, and if a threshold membrane potential is reached, then sodium channels start to open up. If there’s a depolarization, then ions start to move across the cell membrane, and that’s where the T-tubules play a key role. During the part of the cardiomyocyte action potential when calcium ions flow into the cell, the presence of T-tubules helps bring calcium deep into the cell. Once this extracellular calcium gets inside, it binds to the ryanodine receptors on the sarcoplasmic reticulum, which releases even more calcium into the cell - a process called calcium-induced calcium release.

Cardiac excitation-contraction coupling - Osmosis

Cardiac excitation-contraction coupling
Cardiac excitation-contraction coupling
Continue learning with us!
Jessica Moore
Cardiovascular system
Auscultation of the heart
Electrocardiography
Assessments
Cardiac excitation-contraction coupling
Flashcards
High Yield Notes
Flashcards
Cardiac excitation-contraction coupling
Transcript

Another feature of cardiomyocytes are passageways called transverse tubules, or T-tubules. T-tubules are extensions of the outside environment. They increase the surface area of the cardiomyocyte and they look like the letter T, so it’s easy to remember their name. Think of a large walk-through aquarium: you can walk through tunnels and look at the sea creatures all around you, but you’re not in the water with them. Finally, there’s the sarcoplasmic reticulum, which is an organelle that stores intracellular calcium, the calcium that is sequestered inside the cell. When a depolarization wavefront hits a cardiomyocyte, a few calcium ions flow through gap junctions, and if a threshold membrane potential is reached, then sodium channels start to open up. If there’s a depolarization, then ions start to move across the cell membrane, and that’s where the T-tubules play a key role. During the part of the cardiomyocyte action potential when calcium ions flow into the cell, the presence of T-tubules helps bring calcium deep into the cell. Once this extracellular calcium gets inside, it binds to the ryanodine receptors on the sarcoplasmic reticulum, which releases even more calcium into the cell - a process called calcium-induced calcium release.

T-Tubule - an overview | ScienceDirect Topics T-Tubule
T-Tubule
Ion Channel Trafficking
T-Tubules
Skeletal Muscle
T-tubules Are Surface Invaginations; the SR Is an Internal Membrane System
Structure and Function of Calcium Release Channels
2 T Tubules and CRUs Revert to More Primitive Forms Under Pathological Conditions
Muscles
Coupling Action Potentials to Contraction
The Cellular Basis of Cardiac Contractility
The SR Releases Stored Ca 2+ to Activate Contraction
Disorders of Muscle Excitability
Calcium couples muscle membrane excitation to filament contraction
Muscle physiology
Excitation–contraction coupling
EXERCISE | Muscle
Voltage-dependent Sarcoplasmic Reticulum Ca 2+ Release
 Inside the muscle cell, T tubules interact extensively with the smooth endoplasmic reticulum (SER) surrounding each myofibril. Historically, this SER was called sarcoplasmic reticulum. Terminal cisternae of SER are closely associated with T tubules at foot processes that can be visualized by electron microscopy. Together, T tubules and SER constitute a signal-transducing apparatus that converts depolarizations of the plasma membrane into a spike of cytoplasmic Ca 2+ to trigger contraction ( Fig. 39.14 ). An action potential moving through a T tubule triggers the release of Ca 2+ from SER into the cytoplasm ( Fig. 39.14 ). Ca 2+ binding to troponin allows myosin to interact with the thin filament, initiating contraction. This signal transduction process is called excitation–contraction coupling. Three transmembrane proteins located in the T tubule and the terminal cisternae of the SER cooperate to generate the transient Ca 2+ signal ( Fig.

Inside the muscle cell, T tubules interact extensively with the smooth endoplasmic reticulum (SER) surrounding each myofibril. Historically, this SER was called sarcoplasmic reticulum. Terminal cisternae of SER are closely associated with T tubules at foot processes that can be visualized by electron microscopy. Together, T tubules and SER constitute a signal-transducing apparatus that converts depolarizations of the plasma membrane into a spike of cytoplasmic Ca 2+ to trigger contraction ( Fig. 39.14 ). An action potential moving through a T tubule triggers the release of Ca 2+ from SER into the cytoplasm ( Fig. 39.14 ). Ca 2+ binding to troponin allows myosin to interact with the thin filament, initiating contraction. This signal transduction process is called excitation–contraction coupling. Three transmembrane proteins located in the T tubule and the terminal cisternae of the SER cooperate to generate the transient Ca 2+ signal ( Fig.

Distal convoluted tubule - Wikipedia Distal convoluted tubule
Distal convoluted tubule
Contents
Physiology
Clinical significance
Histology
Additional images
References
External links
 Distal convoluted tubule - Wikipedia
Distal convoluted tubule
From Wikipedia, the free encyclopedia
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Distal convoluted tubule
Kidney nephron ("1st proximal convoluted tubule", "2nd distal convoluted tubule")
Section of cortex of human kidney. Details
Precursor
Metanephrogenic blastema
Identifiers
Latin
tubulus contortus distalis
FMA
17721
Anatomical terminology
The distal convoluted tubule ( DCT) is a portion of kidney nephron between the loop of Henle and the collecting tubule . Contents
1 Physiology
2 Clinical significance
3 Histology
4 Additional images
5 References
6 External links
Physiology
It is partly responsible for the regulation of potassium, sodium, calcium, and pH.
On its apical surface (lumen side), cells of the DCT have a thiazide-sensitive Na-Cl cotransporter and are permeable to Ca, via the TRPV5 channel. On the basolateral surface (peritubular capillary side) there is an ATP-dependent Na/K antiporter pump, a secondary active Na/Ca transporter, and an ATP dependent Ca transporter. The basolateral ATP dependent Na/K pump produces the gradient for Na to be absorbed from the apical surface via the Na/Cl symporter, and for Ca to be reclaimed into the blood by the Na/Ca basolateral antiporter. It regulates pH by absorbing bicarbonate and secreting protons (H +) into the filtrate, or by absorbing protons and secreting bicarbonate into the filtrate. Sodium and potassium levels are controlled by secreting K + and absorbing Na +. Sodium absorption by the distal tubule is mediated by the hormone aldosterone. Aldosterone increases sodium reabsorption. Sodium and chloride (salt) reabsorption is also mediated by a group of kinases called WNK kinases.

Distal convoluted tubule - Wikipedia

Distal convoluted tubule
Distal convoluted tubule
Contents
Physiology
Clinical significance
Histology
Additional images
References
External links

Distal convoluted tubule - Wikipedia
Distal convoluted tubule
From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Distal convoluted tubule
Kidney nephron ("1st proximal convoluted tubule", "2nd distal convoluted tubule")
Section of cortex of human kidney. Details
Precursor
Metanephrogenic blastema
Identifiers
Latin
tubulus contortus distalis
FMA
17721
Anatomical terminology
The distal convoluted tubule ( DCT) is a portion of kidney nephron between the loop of Henle and the collecting tubule . Contents
1 Physiology
2 Clinical significance
3 Histology
4 Additional images
5 References
6 External links
Physiology
It is partly responsible for the regulation of potassium, sodium, calcium, and pH.
On its apical surface (lumen side), cells of the DCT have a thiazide-sensitive Na-Cl cotransporter and are permeable to Ca, via the TRPV5 channel. On the basolateral surface (peritubular capillary side) there is an ATP-dependent Na/K antiporter pump, a secondary active Na/Ca transporter, and an ATP dependent Ca transporter. The basolateral ATP dependent Na/K pump produces the gradient for Na to be absorbed from the apical surface via the Na/Cl symporter, and for Ca to be reclaimed into the blood by the Na/Ca basolateral antiporter. It regulates pH by absorbing bicarbonate and secreting protons (H +) into the filtrate, or by absorbing protons and secreting bicarbonate into the filtrate. Sodium and potassium levels are controlled by secreting K + and absorbing Na +. Sodium absorption by the distal tubule is mediated by the hormone aldosterone. Aldosterone increases sodium reabsorption. Sodium and chloride (salt) reabsorption is also mediated by a group of kinases called WNK kinases.

Distinguish Between Renal Corpuscle and Renal Tubule | Definition, Anatomy, Physiology Distinguish Between Renal Corpuscle and Renal Tubule
Distinguish Between Renal Corpuscle and Renal Tubule
Main Difference – Renal Corpuscle vs Renal Tubule
Key Areas Covered
What is Renal Corpuscle
Figure 1: Renal Corpuscle
What is Renal Tubule
Figure 2: Renal Tubule
Similarities Between Renal Corpuscle and Renal Tubule
Difference Between Renal Corpuscle and Renal Tubule
Definition
Composition
Vasculature
Function
Conclusion
Reference:
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 What is Renal Tubule
Renal tubule refers to the long convoluted tubules, which transports urine from the glomeruli to the renal pelvis. It produces urine from the plasma filtrate. The structural parts of the renal tubule are the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and the collecting duct. Different types of molecules are reabsorbed in the different parts of the renal tubule. Proximal convoluted tubule is located in the renal cortex and it mainly reabsorbs water, glucose, amino acids, and ions. The loop of Henle penetrates to the renal medulla. The descending limb of the loop of Henle reabsorbs water while the ascending limb of the loop of Henle reabsorbs sodium ions and chloride ions. The distal convoluted tubule is located in the renal medulla and it reabsorbs water and ions such as sodium, calcium, and chloride. Collecting duct is again located in the renal medulla, reabsorbing water and ions. The differential absorption occurs based on the type of epithelial cells in each part of the renal tubule.

Distinguish Between Renal Corpuscle and Renal Tubule | Definition, Anatomy, Physiology

Distinguish Between Renal Corpuscle and Renal Tubule
Distinguish Between Renal Corpuscle and Renal Tubule
Main Difference – Renal Corpuscle vs Renal Tubule
Key Areas Covered
What is Renal Corpuscle
Figure 1: Renal Corpuscle
What is Renal Tubule
Figure 2: Renal Tubule
Similarities Between Renal Corpuscle and Renal Tubule
Difference Between Renal Corpuscle and Renal Tubule
Definition
Composition
Vasculature
Function
Conclusion
Reference:
Image Courtesy:
About the Author: Lakna
Leave a Reply
Cancel reply

What is Renal Tubule
Renal tubule refers to the long convoluted tubules, which transports urine from the glomeruli to the renal pelvis. It produces urine from the plasma filtrate. The structural parts of the renal tubule are the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and the collecting duct. Different types of molecules are reabsorbed in the different parts of the renal tubule. Proximal convoluted tubule is located in the renal cortex and it mainly reabsorbs water, glucose, amino acids, and ions. The loop of Henle penetrates to the renal medulla. The descending limb of the loop of Henle reabsorbs water while the ascending limb of the loop of Henle reabsorbs sodium ions and chloride ions. The distal convoluted tubule is located in the renal medulla and it reabsorbs water and ions such as sodium, calcium, and chloride. Collecting duct is again located in the renal medulla, reabsorbing water and ions. The differential absorption occurs based on the type of epithelial cells in each part of the renal tubule.

Essay L9 - 1 2 3 4 Summarize the process and purpose of tubular secretion Discuss the importance of countercurrent flow to nephron function Predict the | Course Hero Essay L9 - 1 2 3 4 Summarize the process and purpose of...
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 Tubular secretion is the third stage in the process of urine formation; it comes after filtration and reabsorption. The process of tubular secretion involves of a movement of substances such as potassium, ammonium, creatinine, hydrogen, and drugs such as penicillin from peritubular capillaries into the lumen of the renal tubules via active transport. Tubular secretion occurs at three different locations in nephron of kidney: at the proximal convoluted tubule, at the distal convoluted tubules and at the collecting duct. The purpose of tubular secretion is to regulate blood ph (by the secretion of the hydrogen ions) and removing unwanted substances from the body such as uric acid & ammonium. In other words the role of tubule secretion is to eliminate
body such as uric acid & ammonium. In other words the role of tubule secretion is to eliminate substances that can be toxic to the body via urine. 2. In nephron countercurrent flow occurs in the loop of Henley, this mechanism is called countercurrent multiplication.

Essay L9 - 1 2 3 4 Summarize the process and purpose of tubular secretion Discuss the importance of countercurrent flow to nephron function Predict the | Course Hero

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Tubular secretion is the third stage in the process of urine formation; it comes after filtration and reabsorption. The process of tubular secretion involves of a movement of substances such as potassium, ammonium, creatinine, hydrogen, and drugs such as penicillin from peritubular capillaries into the lumen of the renal tubules via active transport. Tubular secretion occurs at three different locations in nephron of kidney: at the proximal convoluted tubule, at the distal convoluted tubules and at the collecting duct. The purpose of tubular secretion is to regulate blood ph (by the secretion of the hydrogen ions) and removing unwanted substances from the body such as uric acid & ammonium. In other words the role of tubule secretion is to eliminate
body such as uric acid & ammonium. In other words the role of tubule secretion is to eliminate substances that can be toxic to the body via urine. 2. In nephron countercurrent flow occurs in the loop of Henley, this mechanism is called countercurrent multiplication.

T Tubule Medical Definition | Merriam-Webster Medical Dictionary T tubule
T tubule
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 T Tubule Medical Definition | Merriam-Webster Medical Dictionary
T tubule
noun
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Medical Definition of T tubule
: any of the small tubules which run transversely through a striated muscle fiber and through which electrical impulses are transmitted from the sarcoplasm to the fiber's interior
Learn More about T tubule
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T system
TTP
T-tube
T tubule
tubal
tubal abortion
tubal ligation
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Cite this Entry
“T tubule.” Merriam-Webster.com Medical Dictionary, Merriam-Webster, https://www.merriam-webster.com/medical/T%20tubule. Accessed 1 Jun. 2021. Style: MLA
MLA Chicago APA Merriam-Webster
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T Tubule Medical Definition | Merriam-Webster Medical Dictionary

T tubule
T tubule
Medical Definition of T tubule
Learn More about T tubule
Dictionary Entries near T tubule
T tubule
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Style: MLA
Love words? Need even more definitions?

T Tubule Medical Definition | Merriam-Webster Medical Dictionary
T tubule
noun
Save Word
To save this word, you'll need to log in. Log In
Medical Definition of T tubule
: any of the small tubules which run transversely through a striated muscle fiber and through which electrical impulses are transmitted from the sarcoplasm to the fiber's interior
Learn More about T tubule
Dictionary Entries near T tubule
T system
TTP
T-tube
T tubule
tubal
tubal abortion
tubal ligation
See More Nearby Entries
Cite this Entry
“T tubule.” Merriam-Webster.com Medical Dictionary, Merriam-Webster, https://www.merriam-webster.com/medical/T%20tubule. Accessed 1 Jun. 2021. Style: MLA
MLA Chicago APA Merriam-Webster
Love words? Need even more definitions? Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free! Merriam-Webster unabridged

Tubule - Wikipedia Tubule
Tubule
Examples of tubules
References
 Tubule - Wikipedia
Tubule
From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
In biology, a tubule is a general term referring to small tube or similar type of structure. Specifically, tubule can refer to: a small tube or fistular structure
a minute tube lined with glandular epithelium
any hollow cylindrical body structure
a minute canal found in various structures or organs of the body
a slender elongated anatomical channel
a minute tube, especially as an anatomical structure. Examples of tubules
Collecting tubules: terminal channels of the nephrons
Cuvierian tubules: clusters of sticky tubules located at the base of the respiratory tree, which may be discharged by some sea cucumbers ( holothurians) when mechanically stimulated (i.e. being threatened by a predator)
Dentinal tubules or dental canaliculi: minute channels in the dentine of a tooth that extend from the pulp cavity to the cementum or the enamel
Distal convoluted tubule: the convoluted portion of the vertebrate nephron that lies between the loop of Henle and the nonsecretory part of the nephron and that is concerned especially with the concentration of urine
Galactophorous tubule or lactiferous ducts: small channels for the passage of milk from the secreting cells in the mammary gland to the nipple
Loop of Henle: the long U-shaped part of the renal tubule, extending through the medulla from the end of the proximal convoluted tubule.

Tubule - Wikipedia

Tubule - Wikipedia
Tubule
From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
In biology, a tubule is a general term referring to small tube or similar type of structure. Specifically, tubule can refer to: a small tube or fistular structure
a minute tube lined with glandular epithelium
any hollow cylindrical body structure
a minute canal found in various structures or organs of the body
a slender elongated anatomical channel
a minute tube, especially as an anatomical structure. Examples of tubules
Collecting tubules: terminal channels of the nephrons
Cuvierian tubules: clusters of sticky tubules located at the base of the respiratory tree, which may be discharged by some sea cucumbers ( holothurians) when mechanically stimulated (i.e. being threatened by a predator)
Dentinal tubules or dental canaliculi: minute channels in the dentine of a tooth that extend from the pulp cavity to the cementum or the enamel
Distal convoluted tubule: the convoluted portion of the vertebrate nephron that lies between the loop of Henle and the nonsecretory part of the nephron and that is concerned especially with the concentration of urine
Galactophorous tubule or lactiferous ducts: small channels for the passage of milk from the secreting cells in the mammary gland to the nipple
Loop of Henle: the long U-shaped part of the renal tubule, extending through the medulla from the end of the proximal convoluted tubule.

What Is the Function of Transverse Tubules? What Is the Function of Transverse Tubules?
What Is the Function of Transverse Tubules? Transverse tubules exist in plasma membranes within skeletal muscle and cardiac muscle cells. They appear as deep in invaginations within surrounding sheaths of sarcoplasmic reticulum, which is further broken down into myoglobin and mitochondria. In the process of creating invaginations, transverse tubules allow impulses to permeate the cell membrane, and ultimately excite, or activate, the sarcoplasmic reticulum. The sarcoplasmic reticulum, in turn, creates a network around sensitive myofibrils, which store and release critical supplies of calcium that enable muscle contractions. Transverse tubules act as transmitters and receivers of information during the process of conducting electrical impulses. As receivers, they allow the infiltration of calcium into chambers called L-type calcium channels. These channels then absorb and transmit calcium through the cell into calcium-release channels, which are essential for enabling proper skeletal muscle contractions. While transverse tubules help promote proper movement of skeletal tissues and fibers, they only appear in skeletal muscles, and are absent in skeletal muscles. More From Reference
1
What Is Maslow's Hierarchy of Needs — & What are Its Advantages & Disadvantages? 2
Life After COVID-19:

What Is the Function of Transverse Tubules?

What Is the Function of Transverse Tubules?
What Is the Function of Transverse Tubules?

Transverse tubules exist in plasma membranes within skeletal muscle and cardiac muscle cells. They appear as deep in invaginations within surrounding sheaths of sarcoplasmic reticulum, which is further broken down into myoglobin and mitochondria. In the process of creating invaginations, transverse tubules allow impulses to permeate the cell membrane, and ultimately excite, or activate, the sarcoplasmic reticulum. The sarcoplasmic reticulum, in turn, creates a network around sensitive myofibrils, which store and release critical supplies of calcium that enable muscle contractions. Transverse tubules act as transmitters and receivers of information during the process of conducting electrical impulses. As receivers, they allow the infiltration of calcium into chambers called L-type calcium channels. These channels then absorb and transmit calcium through the cell into calcium-release channels, which are essential for enabling proper skeletal muscle contractions. While transverse tubules help promote proper movement of skeletal tissues and fibers, they only appear in skeletal muscles, and are absent in skeletal muscles. More From Reference
1
What Is Maslow's Hierarchy of Needs — & What are Its Advantages & Disadvantages? 2
Life After COVID-19:

Cardiac T-Tubule Microanatomy and Function | Physiological Reviews Cardiac T-Tubule Microanatomy and Function
Cardiac T-Tubule Microanatomy and Function
Abstract
I. INTRODUCTION
II. CARDIAC T-TUBULE STRUCTURE
A. History of T-Tubule Structure-Related Research
B. Gross Morphology and Geometry
C. Membrane Ultrastructure and Microdomains
1. cBIN1 microfolds: microdomains supporting LTCC-RyR dyads
2. Caveoli (caveolae): β-AR/LTCC signaling hubs
3. Ankyrin B microdomains: NCX/NKA/InsP 3 macromolecular complex
D. Peri-Membrane Cytoskeleton Scaffolds at Cardiac T-Tubules
1. Actin filaments, tropomyosin, and N-WASP
2. Costamere complex and t-tubule membrane-associated scaffolds
3. Myofilament structural proteins
E. Variation in Cardiac T-Tubule Geometry
III. TRANSMEMBRANE PROTEINS AT CARDIAC T-TUBULES
A. Ion Handling Proteins (Channels/Transporters/Pumps)
1. Ca 2+ handling proteins
2. Na + handling proteins
3. K + handling proteins
B. Signaling Molecules at Cardiac T-Tubules
IV. FUNCTION OF CARDIAC T-TUBULES
A. Dyad and EC Coupling
1. LTCC trafficking and clustering to dyads through BIN1
2. RyR recruitment to dyads through BIN1
3. Junctophilin-2 in t-tubule-jSR junctional membrane complex formation
B. Ion Diffusion and Membrane Excitability
C. Other Microdomain-Related Functions
V. LIFE CYCLE OF CARDIAC T-TUBULES
A. Membrane Biogenesis, Maintenance, and Turnover
B. Ion Channel Trafficking and Half-Life
VI. ALTERATION OF T-TUBULE STRUCTURE AND FUNCTION IN HEART FAILURE
VII. CONCLUSIONS
GRANTS
DISCLOSURES
Acknowledgments
 The transverse tubules occur around myofilaments, anchoring to sarcomeric z-discs through costameres. The phospholipid-rich t-tubule lipid bilayers are shaped and maintained by membrane scaffolding proteins and intracellular cytoskeleton, as well as surrounding extracellular matrix. T-tubule membrane contains microdomains that compartmentalize transmembrane ion handling proteins and signaling molecules. Together, t-tubules are effective organelles that serve as a centralized signaling hub controlling cardiac contractile function and electrophysiology. The most recognized function of t-tubules is regulation of cardiac EC coupling by concentrating voltage-gated L-type calcium channels (LTCCs) and positioning them in close proximity to calcium sense and release channels, ryanodine receptors (RyRs), at the junctional membrane of sarcoplasmic reticulum (jSR). The closely approximated LTCCs and RyRs form calcium releasing units, dyads, where calcium transients are initiated following each beat-to-beat action potential. With recent advances in high-resolution imaging technologies, detailed t-tubule microdomain structural organization and newly recognized functions are starting to emerge. For instance, the t-tubular invagination is not smooth, but consists of extensive membrane microfolds sculpted by a cardiac isoform of a BAR domain containing protein bridging integrator 1 (BIN1 or amphiphysin 2) ( 91 ). Cardiac BIN1 (cBIN1) organized membrane microfolds generate diffusion barriers which slow t-tubule-associated extracellular ionic diffusion, preserving electrical stability of myocytes during tachycardia-related fluctuations of ionic concentrations in the local extracellular and possibly intracellular environment ( 91 ). In addition, cBIN1-microfolds also organize local microdomains for efficient and dynamic regulation of cardiac dyad function, regulating EC coupling ( 66, 93, 94 ).

Cardiac T-Tubule Microanatomy and Function
Cardiac T-Tubule Microanatomy and Function
Abstract
I. INTRODUCTION
II. CARDIAC T-TUBULE STRUCTURE
A. History of T-Tubule Structure-Related Research
B. Gross Morphology and Geometry
C. Membrane Ultrastructure and Microdomains
1. cBIN1 microfolds: microdomains supporting LTCC-RyR dyads
2. Caveoli (caveolae): β-AR/LTCC signaling hubs
3. Ankyrin B microdomains: NCX/NKA/InsP 3 macromolecular complex
D. Peri-Membrane Cytoskeleton Scaffolds at Cardiac T-Tubules
1. Actin filaments, tropomyosin, and N-WASP
2. Costamere complex and t-tubule membrane-associated scaffolds
3. Myofilament structural proteins
E. Variation in Cardiac T-Tubule Geometry
III. TRANSMEMBRANE PROTEINS AT CARDIAC T-TUBULES
A. Ion Handling Proteins (Channels/Transporters/Pumps)
1. Ca 2+ handling proteins
2. Na + handling proteins
3. K + handling proteins
B. Signaling Molecules at Cardiac T-Tubules
IV. FUNCTION OF CARDIAC T-TUBULES
A. Dyad and EC Coupling
1. LTCC trafficking and clustering to dyads through BIN1
2. RyR recruitment to dyads through BIN1
3. Junctophilin-2 in t-tubule-jSR junctional membrane complex formation
B. Ion Diffusion and Membrane Excitability
C. Other Microdomain-Related Functions
V. LIFE CYCLE OF CARDIAC T-TUBULES
A. Membrane Biogenesis, Maintenance, and Turnover
B. Ion Channel Trafficking and Half-Life
VI. ALTERATION OF T-TUBULE STRUCTURE AND FUNCTION IN HEART FAILURE
VII. CONCLUSIONS
GRANTS
DISCLOSURES
Acknowledgments

Think of it this way. Your biceps muscle is composed of many different muscle cells working together. When your brain tells your biceps to contract, does it send individual nerves to every single muscle cell? No it doesn't (I guess that really isn't an obvious answer). This is where the T-tubules come in. They transmit electrical impulses from one muscle cell to another. This way, only some muscle cells need to be activated by a nerve--the rest will be signaled through the T-tubule network, so that all of the muscle cells will contract together. So what happens when you block the T-tubules? Your muscle doesn't work so well anymore. You might still get cell-to-cell communication (I'm not sure), but even if you did, it would be slow so that the muscle fibers would not contract synchronously.

Think of it this way. Your biceps muscle is composed of many different muscle cells working together. When your brain tells your biceps to contract, does it send individual nerves to every single muscle cell? No it doesn't (I guess that really isn't an obvious answer). This is where the T-tubules come in. They transmit electrical impulses from one muscle cell to another. This way, only some muscle cells need to be activated by a nerve--the rest will be signaled through the T-tubule network, so that all of the muscle cells will contract together. So what happens when you block the T-tubules? Your muscle doesn't work so well anymore. You might still get cell-to-cell communication (I'm not sure), but even if you did, it would be slow so that the muscle fibers would not contract synchronously.

The Renal Tubule: Definition, Function & Terms - Video & Lesson Transcript | Study.com The Renal Tubule: Definition, Function & Terms
The Renal Tubule: Definition, Function & Terms
The Ultrafiltrate in the Renal Tubule
Proximal Convoluted Tubule
The Loop of Henle
Distal Convoluted Tubule and Connecting Tubule
The Role of PTH in the Regulation of Calcium
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 This difference in functionality is what establishes the kidney's medullary osmotic gradient for maximal conservation of water. Distal Convoluted Tubule and Connecting Tubule
Once the filtrate passes through the thick ascending limb of Henle, it enters the distal convoluted tubule, which is a duct of the renal tubule located in the kidney's cortex that reabsorbs calcium, sodium, and chloride and regulates the pH of urine by secreting protons and absorbing bicarbonate. The reason this is called the distal, as opposed to proximal, convoluted tubule is because it is the segment farthest away in terms of position and connection to the renal corpuscle. The distal convoluted tubule will then connect to a section called the connecting tubule, which will do many of the same things as the distal convoluted tubule, but it is not, however, considered to be a part of the renal tubule. The Role of PTH in the Regulation of Calcium
It's important to know that a hormone in your body, called parathyroid hormone, or PTH for short, plays a role in the distal and proximal convoluted tubules. Recall that the majority of calcium is reabsorbed, through passive means, in the proximal convoluted tubule. This is the case under normal conditions. However, if PTH is secreted in response to low levels of calcium in the blood, then the proximal convoluted tubule will not be allowed to reabsorb calcium. Instead, the majority of calcium will be reabsorbed actively in the distal convoluted tubule and connecting segment as well as part of the loop of Henle. In addition, PTH will prevent the proximal tubule from reabsorbing phosphate, causing a net excretion of phosphate out of the body via urine.

The Renal Tubule: Definition, Function & Terms - Video & Lesson Transcript | Study.com

The Renal Tubule: Definition, Function & Terms
The Renal Tubule: Definition, Function & Terms
The Ultrafiltrate in the Renal Tubule
Proximal Convoluted Tubule
The Loop of Henle
Distal Convoluted Tubule and Connecting Tubule
The Role of PTH in the Regulation of Calcium
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Are you a student or a teacher?
The Renal Tubule: Definition, Function & Terms
Related Study Materials

This difference in functionality is what establishes the kidney's medullary osmotic gradient for maximal conservation of water. Distal Convoluted Tubule and Connecting Tubule
Once the filtrate passes through the thick ascending limb of Henle, it enters the distal convoluted tubule, which is a duct of the renal tubule located in the kidney's cortex that reabsorbs calcium, sodium, and chloride and regulates the pH of urine by secreting protons and absorbing bicarbonate. The reason this is called the distal, as opposed to proximal, convoluted tubule is because it is the segment farthest away in terms of position and connection to the renal corpuscle. The distal convoluted tubule will then connect to a section called the connecting tubule, which will do many of the same things as the distal convoluted tubule, but it is not, however, considered to be a part of the renal tubule. The Role of PTH in the Regulation of Calcium
It's important to know that a hormone in your body, called parathyroid hormone, or PTH for short, plays a role in the distal and proximal convoluted tubules. Recall that the majority of calcium is reabsorbed, through passive means, in the proximal convoluted tubule. This is the case under normal conditions. However, if PTH is secreted in response to low levels of calcium in the blood, then the proximal convoluted tubule will not be allowed to reabsorb calcium. Instead, the majority of calcium will be reabsorbed actively in the distal convoluted tubule and connecting segment as well as part of the loop of Henle. In addition, PTH will prevent the proximal tubule from reabsorbing phosphate, causing a net excretion of phosphate out of the body via urine.

What Is the Function of the Proximal Convoluted Tubule? What Is the Function of the Proximal Convoluted Tubule?
What Is the Function of the Proximal Convoluted Tubule? What Is the Function of the Proximal Convoluted Tubule? What Is the Function of the Proximal Convoluted Tubule? By Staff Writer Last Updated Apr 8, 2020 3:04:34 PM ET
The proximal convoluted tubules, or PCTs, are part of a system of absorption and reabsorption as well as secretion from within the kidneys. Specifically, PCTs are part of a complex system that reabsorbs most of the water and ions from the urinary space back into the body, which is a process called tubular reabsorption. The PCTs are part of the duct system within the nephrons of the kidneys. They connect the Bowman's capsule to the Loop of Henle and are primary located where dissolved materials and solutes are reabsorbed back into the body. Only one part of a larger system, these materials eventually make their way back into the blood through the cells of each tubule in a process called tubular reabsorption. The cells linking the PCT have the ability to pick up dissolved solutes such as glucose and electrolytes from filtrate in the kidney. From there, the cells send those materials into the interstitial fluid where they then diffuse back into the blood via peritubular capillaries. Through this process, the PCTs regulate the pH of the filtrate and reabsorb 65 percent of the materials that need to be reabsorbed.

What Is the Function of the Proximal Convoluted Tubule?

What Is the Function of the Proximal Convoluted Tubule?
What Is the Function of the Proximal Convoluted Tubule?

What Is the Function of the Proximal Convoluted Tubule? What Is the Function of the Proximal Convoluted Tubule? By Staff Writer Last Updated Apr 8, 2020 3:04:34 PM ET
The proximal convoluted tubules, or PCTs, are part of a system of absorption and reabsorption as well as secretion from within the kidneys. Specifically, PCTs are part of a complex system that reabsorbs most of the water and ions from the urinary space back into the body, which is a process called tubular reabsorption. The PCTs are part of the duct system within the nephrons of the kidneys. They connect the Bowman's capsule to the Loop of Henle and are primary located where dissolved materials and solutes are reabsorbed back into the body. Only one part of a larger system, these materials eventually make their way back into the blood through the cells of each tubule in a process called tubular reabsorption. The cells linking the PCT have the ability to pick up dissolved solutes such as glucose and electrolytes from filtrate in the kidney. From there, the cells send those materials into the interstitial fluid where they then diffuse back into the blood via peritubular capillaries. Through this process, the PCTs regulate the pH of the filtrate and reabsorb 65 percent of the materials that need to be reabsorbed.

What is the Renal Tubule? (with pictures) What is the Renal Tubule? (with pictures)
What is the Renal Tubule? (with pictures)
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 The distal convoluted tubule also helps regulate sodium, potassium, and calcium levels in the blood. Niki Foster
In addition to her role as a InfoBloom editor, Niki enjoys educating herself about interesting and unusual topics in order to get ideas for her own articles. She is a graduate of UCLA, where she majored in Linguistics and Anthropology. Niki Foster
In addition to her role as a InfoBloom editor, Niki enjoys educating herself about interesting and unusual topics in order to get ideas for her own articles. She is a graduate of UCLA, where she majored in Linguistics and Anthropology. Readers Also Love
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A diagram of a kidney. The renal tubule is part of the filtration system in the nephrons of the kidneys.

What is the Renal Tubule? (with pictures)

What is the Renal Tubule? (with pictures)
What is the Renal Tubule? (with pictures)
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The distal convoluted tubule also helps regulate sodium, potassium, and calcium levels in the blood. Niki Foster
In addition to her role as a InfoBloom editor, Niki enjoys educating herself about interesting and unusual topics in order to get ideas for her own articles. She is a graduate of UCLA, where she majored in Linguistics and Anthropology. Niki Foster
In addition to her role as a InfoBloom editor, Niki enjoys educating herself about interesting and unusual topics in order to get ideas for her own articles. She is a graduate of UCLA, where she majored in Linguistics and Anthropology. Readers Also Love
26 Incredibly Wealthy Hollywood Stars Can You Guess Which Team These Athletes Played For? Any American Should Pass This US History Quiz Do You Recognize The Stars Who Wore These Iconic Outfits? The Most Beautiful Women Forecasting the Weather Amazing Optical Illusions That Will Play Tricks on Your Mind 40 Wedding Picture Fails You Don't Want to Miss 17 Interesting Maps That Will Change Your Worldview
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A diagram of a kidney. The renal tubule is part of the filtration system in the nephrons of the kidneys.

Release of Calcium Ions by the Sarcoplasmic Reticulum - Medical Physiology Release of Calcium Ions by the Sarcoplasmic Reticulum
Release of Calcium Ions by the Sarcoplasmic Reticulum
Figure 7-5
 Note that the T tubules communicate with the outside of the cell membrane, and deep in the muscle fiber, each T tubule lies adjacent to the ends of longitudinal sarcoplasmic reticulum tubules that surround all sides of the actual myofibrils that contract. This illustration was drawn from frog muscle, which has one T tubule per sarcomere, located at the Z line. A similar arrangement is found in mammalian heart muscle, but mammalian skeletal muscle has two T tubules per sarcomere, located at the A-I band junctions. ( Redrawn from Bloom W, Fawcett DW: A Textbook of Histology. Philadelphia: WB Saunders, 1986. Modified after Peachey LD: J Cell Biol 25:209, 1965. Drawn by Sylvia Colard Keene .)

Release of Calcium Ions by the Sarcoplasmic Reticulum - Medical Physiology

Release of Calcium Ions by the Sarcoplasmic Reticulum
Release of Calcium Ions by the Sarcoplasmic Reticulum
Figure 7-5

Note that the T tubules communicate with the outside of the cell membrane, and deep in the muscle fiber, each T tubule lies adjacent to the ends of longitudinal sarcoplasmic reticulum tubules that surround all sides of the actual myofibrils that contract. This illustration was drawn from frog muscle, which has one T tubule per sarcomere, located at the Z line. A similar arrangement is found in mammalian heart muscle, but mammalian skeletal muscle has two T tubules per sarcomere, located at the A-I band junctions. ( Redrawn from Bloom W, Fawcett DW: A Textbook of Histology. Philadelphia: WB Saunders, 1986. Modified after Peachey LD: J Cell Biol 25:209, 1965. Drawn by Sylvia Colard Keene .)

T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases | Skeletal Muscle | Full Text T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
Abstract
Introduction
T-tubule plasticity
Morphological aspects of triad biogenesis
Sarcoplasmic reticulum
Transverse tubule
Molecular mechanisms involved in T-tubule biogenesis and triad formation and maintenance
Table 1 Proteins implicated in triad organization, roles and associated human diseasesa
Caveolin 3
Amphiphysin 2 (BIN1)
Dysferlin
Mitsugumins
Junctophilins
Myotubularin
The RyR-DHPR complex
Conclusion
References
Acknowledgements
Author information
Affiliations
Corresponding author
Additional information
Competing interests
Authors' contributions
Authors’ original submitted files for images
Authors’ original file for figure 1
Authors’ original file for figure 2
Authors’ original file for figure 3
Authors’ original file for figure 4
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About this article
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Keywords
 Here, we provide a description of triad structure and plasticity and review the role of proteins that have been linked to T-tubule biogenesis and triad formation and/or maintenance specifically in skeletal muscle: caveolin 3, amphiphysin 2, dysferlin, mitsugumins, junctophilins, myotubularin, ryanodine receptor, and dihydhropyridine Receptor. The importance of these proteins in triad biogenesis and subsequently in muscle contraction is sustained by studies on animal models and by the direct implication of most of these proteins in human myopathies. Introduction
To trigger skeletal muscle contraction, the action potential generated by motor neurons is transmitted through motor nerves to muscle cells. The excitation-contraction (EC) coupling, i.e. signal transmission from the sarcolemma to the actin/myosin apparatus, is mediated by a second messenger, calcium ions. Indeed, muscle fibers contain large internal calcium stores with the ability to quickly release and retrieve calcium (Figure 1, right panel). For a fast and fine-tuning of muscle contraction, these stores are maintained under the control of the action potential, which ensures calcium release simultaneously within the whole interior of the muscle fiber. As myofibers are 50-100 μm in diameter and several millimeters to centimeters long, a highly specialized structure named the triad is necessary to overcome spatial limits in using calcium as secondary messenger, and connect the sarcolemma with the calcium stores. The sarcolemma forms regular invaginations which insert between myofibrils, termed transverse tubules (T-tubules). In skeletal muscle, T-tubules tightly associate with the sarcoplasmic reticulum (SR), in a region called terminal cisternae/junctional SR.

T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases | Skeletal Muscle | Full Text

T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
Abstract
Introduction
T-tubule plasticity
Morphological aspects of triad biogenesis
Sarcoplasmic reticulum
Transverse tubule
Molecular mechanisms involved in T-tubule biogenesis and triad formation and maintenance
Table 1 Proteins implicated in triad organization, roles and associated human diseasesa
Caveolin 3
Amphiphysin 2 (BIN1)
Dysferlin
Mitsugumins
Junctophilins
Myotubularin
The RyR-DHPR complex
Conclusion
References
Acknowledgements
Author information
Affiliations
Corresponding author
Additional information
Competing interests
Authors' contributions
Authors’ original submitted files for images
Authors’ original file for figure 1
Authors’ original file for figure 2
Authors’ original file for figure 3
Authors’ original file for figure 4
Rights and permissions
About this article
Cite this article
Share this article
Keywords

Here, we provide a description of triad structure and plasticity and review the role of proteins that have been linked to T-tubule biogenesis and triad formation and/or maintenance specifically in skeletal muscle: caveolin 3, amphiphysin 2, dysferlin, mitsugumins, junctophilins, myotubularin, ryanodine receptor, and dihydhropyridine Receptor. The importance of these proteins in triad biogenesis and subsequently in muscle contraction is sustained by studies on animal models and by the direct implication of most of these proteins in human myopathies. Introduction
To trigger skeletal muscle contraction, the action potential generated by motor neurons is transmitted through motor nerves to muscle cells. The excitation-contraction (EC) coupling, i.e. signal transmission from the sarcolemma to the actin/myosin apparatus, is mediated by a second messenger, calcium ions. Indeed, muscle fibers contain large internal calcium stores with the ability to quickly release and retrieve calcium (Figure 1, right panel). For a fast and fine-tuning of muscle contraction, these stores are maintained under the control of the action potential, which ensures calcium release simultaneously within the whole interior of the muscle fiber. As myofibers are 50-100 μm in diameter and several millimeters to centimeters long, a highly specialized structure named the triad is necessary to overcome spatial limits in using calcium as secondary messenger, and connect the sarcolemma with the calcium stores. The sarcolemma forms regular invaginations which insert between myofibrils, termed transverse tubules (T-tubules). In skeletal muscle, T-tubules tightly associate with the sarcoplasmic reticulum (SR), in a region called terminal cisternae/junctional SR.

T-Tubule Function in Mammalian Cardiac Myocytes | Circulation Research T-Tubule Function in Mammalian Cardiac Myocytes
T-Tubule Function in Mammalian Cardiac Myocytes
Abstract
Occurrence and Morphology of the T-Tubules
T-Tubule Development Is Labile
Proteins Present in the T-Tubule Membrane
Ca2+-Handling Proteins
Na+-Handling Proteins
K+-Handling Proteins
Anion-Handling Proteins
Second-Messenger Pathways
Interpretation of Immunohistochemical Data
Protein Colocalization Within, and With Proteins Adjacent to, the T-Tubules
Localization of Function
Cells Lacking T-Tubules
Diffusion Studies
Scanning Pipette
Detubulation
Functional Role
Electrical Properties of T-Tubules
Coupling of Ca 2+ Entry and Ca 2+ Release
Ca 2+ Efflux
Signal Transduction
Changes During Development and Disease
T-Tubule Development and Morphology in Hypertrophy and Failure
Changes in Protein Expression in Development, Hypertrophy, and Failure
Relevance of Changes in T-Tubule Structure and Protein Expression to Function
Conclusions and Unanswered Questions
Footnotes
References
 Although the diversity of estimates of the extent of the t-tubules within a species makes it impossible to determine whether there may be differences between species, it is tempting to speculate that the extent of the t-tubules varies between species depending on cell size (surface area/volume ratio) and heart rate if the t-tubules are necessary to produce synchronous Ca 2+ release throughout the cell (see Coupling of Ca 2+ Entry and Ca 2+ Release, later) and, hence, synchronous contraction. Although we are unaware of any differences related to cell size, the density of the t-tubular network is greater in the mouse, which has a resting heart rate of 300 to 400 bpm, than in the pig, which has a heart rate of <100 bpm. 1
T-Tubule Development Is Labile
Ventricular myocytes isolated from neonatal hearts show little evidence of t-tubule development, 4,18 and cells kept in culture for 6 days show a progressive decrease of t-tubule density. 19 T-tubule structure has also been reported to change in myocytes from failing hearts (see T-Tubule Development and Morphology in Hypertrophy and Failure). However, the mechanisms underlying the expression and maintenance of the t-tubules are not clear. Once formed, the ability of the tubular system to maintain its remarkable degree of structure despite the forces exerted during the normal contraction cycle may be due to the presence of a “scaffold” of focal adhesion molecules, membrane-associated proteins, and basal lamina proteins. 20
Proteins Present in the T-Tubule Membrane
The function of the t-tubules depends not only on their structure but also on the proteins within, and adjacent to, the t-tubule membrane. Immunohistochemical techniques have been widely used to investigate the location of proteins within cardiac ventricular myocytes. Such studies have shown marked variations in the distribution of membrane proteins, although a distinction needs to be drawn between the fraction of a particular type of protein located at the t-tubule and whether this is greater than the fraction of the total cell membrane located within the t-tubules, ie, whether protein density is higher (concentrated) at the t-tubule. This is discussed further in Interpretation of Immunohistochemical Data and in Conclusions and Unanswered Questions.

T-Tubule Function in Mammalian Cardiac Myocytes | Circulation Research

T-Tubule Function in Mammalian Cardiac Myocytes
T-Tubule Function in Mammalian Cardiac Myocytes
Abstract
Occurrence and Morphology of the T-Tubules
T-Tubule Development Is Labile
Proteins Present in the T-Tubule Membrane
Ca2+-Handling Proteins
Na+-Handling Proteins
K+-Handling Proteins
Anion-Handling Proteins
Second-Messenger Pathways
Interpretation of Immunohistochemical Data
Protein Colocalization Within, and With Proteins Adjacent to, the T-Tubules
Localization of Function
Cells Lacking T-Tubules
Diffusion Studies
Scanning Pipette
Detubulation
Functional Role
Electrical Properties of T-Tubules
Coupling of Ca 2+ Entry and Ca 2+ Release
Ca 2+ Efflux
Signal Transduction
Changes During Development and Disease
T-Tubule Development and Morphology in Hypertrophy and Failure
Changes in Protein Expression in Development, Hypertrophy, and Failure
Relevance of Changes in T-Tubule Structure and Protein Expression to Function
Conclusions and Unanswered Questions
Footnotes
References

 These are organized into sarcomeres, the fundamental contractile units of muscle cells. The regular organization of myofibrils into sarcomeres gives cardiac muscle cells a striped or striatedappearance when looked at through a microscope, similar to skeletal muscle. These striations are caused by lighter I bandscomposed mainly of a protein called actin, and darker A bandscomposed mainly of myosin. [ 3]
Cardiomyocytes contain T-tubules, pouches of membrane that run from the surface to the cell's interior which help to improve the efficiency of contraction. The majority of these cells contain only one nucleus(although they may have as many as four), unlike skeletal muscle cells which typically contain many nuclei. Cardiac muscle cells contain many mitochondriawhich provide the energy needed for the cell in the form of adenosine triphosphate(ATP), making them highly resistant to fatigue. [ 5][3]
T-tubules[edit]
Main article: T-tubules
T-tubules are microscopic tubes that run from the cell surface to deep within the cell. They are continuous with the cell membrane, are composed of the same phospholipid bilayer, and are open at the cell surface to the extracellular fluidthat surrounds the cell. T-tubulesin cardiac muscle are bigger and wider than those in skeletal muscle, but fewer in number.[5] In the centre of the cell they join together, running into and along the cell as a transverse-axial network.

These are organized into sarcomeres, the fundamental contractile units of muscle cells. The regular organization of myofibrils into sarcomeres gives cardiac muscle cells a striped or striatedappearance when looked at through a microscope, similar to skeletal muscle. These striations are caused by lighter I bandscomposed mainly of a protein called actin, and darker A bandscomposed mainly of myosin. [ 3]
Cardiomyocytes contain T-tubules, pouches of membrane that run from the surface to the cell's interior which help to improve the efficiency of contraction. The majority of these cells contain only one nucleus(although they may have as many as four), unlike skeletal muscle cells which typically contain many nuclei. Cardiac muscle cells contain many mitochondriawhich provide the energy needed for the cell in the form of adenosine triphosphate(ATP), making them highly resistant to fatigue. [ 5][3]
T-tubules[edit]
Main article: T-tubules
T-tubules are microscopic tubes that run from the cell surface to deep within the cell. They are continuous with the cell membrane, are composed of the same phospholipid bilayer, and are open at the cell surface to the extracellular fluidthat surrounds the cell. T-tubulesin cardiac muscle are bigger and wider than those in skeletal muscle, but fewer in number.[5] In the centre of the cell they join together, running into and along the cell as a transverse-axial network.

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Immunolocalization studies showed MGP localized in embryonic ureters and collecting tubules also contained abundant fibronectin. Matrix Gla protein binds to fibronectin and enhances cell attachment and spreading on fibronectin
ghanensis mites had initiated infection by invading the skin through the orifices of the hair follicles and meibomian glands through the main collecting tubules of the meibomian glands, respectively. A study on the nature of association between Demodex mites and bacteria involved in skin and meibomian gland lesions of demodectic mange in cattle
The medullary interstitium is often scarred and collecting tubules typically contain elongated or rectangular urate crystals. Crystalline nephropathies
DDAVP also results in a potent antidiuretic effect through the impairment of free water absorption by the distal tubules, collecting tubules, and collecting ducts by binding to the arginine vasopressin receptor and reducing water permeability [8]. Pitfalls in Interventional Pain Medicine: Hyponatremia after DDAVP for a Patient with Von Willebrand Disease Undergoing an Epidural Steroid Injection
There were very largely dilated collecting tubules and ducts with granular degeneration & sloughing out of lining epithelia. Effect of fluoride on kidney of albino rabbit-an experimental study
TH inhibition with potassium perchlorate did not affect the expression of E-cadherin in the proximal tubules, but it down-regulates E-cadherin expression in the distal and collecting tubules during premetamorphosis. Expression of cell adhesion molecules in the normal and T3 blocked development of the tadpole's kidney of Bufo arenarum (Amphibian, Anuran, Bufonidae)/ Expressao das moleculas de adesao celular no desenvolvimento normal e com a inibicao do hormonio tireoidea do rim nas larvas do Bufo arenarum (Amphibia, Anura, Bufonidae)
Glomeruli, distal convoluted tubules, and collecting tubules were relatively spared in the vultures that had early lesions. J Wildl Dis: Pathology and proposed pathophysiology of diclofenac poisoning in free-living and experimentally exposed oriental white-backed vultures (Gyps bengalensis)
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