Relating to biologic variations or rhythms with a cycle of about 24 hours. Compare: infradian, ultradian.
a pattern based on a 24-hour cycle, especially the repetition of certain physiological phenomena, such as sleeping and eating.
The diurnal cadence which, in humans (without cyclical cues provided by natural light), is 24.1–24.2 hours (older data had put this figure at 25.4 hours). Photoperiodic information from the eyes synchronises the circadian pacemaker with the light-dark cycle; circadian rhythm affects drug metabolism (e.g., antacids, halothane), serum levels of various substances (in particular adrenocortical hormones) that are routinely measured to detect and monitor disease, physiologic activities (e.g., blood pressure, myocardial blood flow and oxygen demand), psychosomatic disease and sleep cycles, cell division, haematopoiesis and natural killer cell activity.
Diurnal rhythm, ultradian rhythm Physiology An innate, daily, fluctuation of physiologic and behavioral functions–eg sleep waking, generally tied to the 24 hr day-night cycle; the diurnal cadence in humans without cyclical cues provided by natural light, is 25.4 hrs; CR affects drug metabolism, serum levels of various substances–eg, ACTH, physiologic activities–eg, BP, myocardial blood flow and O2 demand, psychosomatic disease and sleep cycles, cell division, hematopoiesis, NK cell activity. See Biorhythm, Circadian pacemaker, Insomnia, Jet lag, Melatonin, Shift work.
A biological 24 hour cycle that applies to many physiological processes and variables and is synchronized to the day-night cycle occasioned by the rotation of the earth. See also BIORHYTHMS.
the basic rhythm with a periodicity of approximately 24 hours that organisms undergo when isolated from the daily rhythmical changes of the environment and are, for example, kept entirely in the dark. This rhythm demonstrates the ability of the organs to measure time, but the physiological basis of this is largely unknown. See DIURNAL RHYTHM, BIOLOGICAL CLOCK.
Any body rhythm that recurs in 24-hour cycles. The sleep-wake cycle is an example of a circadian rhythm.
physiological variations over 24 h, generated by a 'clock' in the brain (nerve centres in the hypothalamus, with input from the eyes); normally synchronized to the light-dark cycle, but effective even in conditions without cues from light or time. Influenced by the hormone melatonin from the pineal gland. Circadian means 'about a day'. Variables affected include body temperature, alertness and sleepiness, urine output, cortisol secretion. See also jet lag.
n person's biological patterns within a 24-hour cycle, circa a day. See also chronobiology.
The characteristic of some processes to repeat at approximately 24-hour intervals. Examples: intraocular pressure is at its lowest every evening and highest every morning; corneal sensitivity is at its lowest every morning and highest every evening. Syn. diurnal cycle (provided the variation in activity or behaviour is more or less divided equally between night and day). See melanopsin.
denoting a period of about 24 hours.
the daily rhythm of physiological activity as expressed by the Chinese circadian clock. This explains the flow of energy or Qi through the body, via the meridians, each meridian having two hours of maximum and two of minimum function in every day.
the regular recurrence of certain phenomena in cycles of approximately 24 hours, e.g. biological activities that occur at about the same time each day (or night) regardless of constant darkness or other conditions of illumination.
Thus, maintaining appropriate sleep habits such as a consistent sleep-wake schedule and engaging in relaxing activities prior to bedtime are one way parents can help support their children's optimal sleep.
Individuals with BP are often characterized by a decreased need for sleep or dysregulated sleep-wake schedules.
However, one symptom that is characteristic of BP that distinguishes it from these other disorders of childhood is a decreased need for sleep (Kowatch, Youngstrom, Danielyan, & Findling, 2005) and dysregulated sleep-wake schedules (Faedda, Baldessarini, Glovinsky, & Austin, 2004).
Irregularity in children's sleep-wake schedules are also related to poor teacher ratings of school functioning in fifth graders (Acebo & Carskadon, 1993).
Adults typically set children's bedtimes and in doing so night after night, they also set their children's internal clocks and establish their sleep-wake schedules.
A recent systematic review with metaanalysis of 37 clinical investigations determined that stimulus control was the most effective CBT intervention) Stimulus control consists of 5 basic instructions (TABLE) designed to help the patient reassociate sleep stimuli (ie, bed/ bedroom) with falling asleep and establishing consistent sleep-wake schedules.
Which nondrug alternatives can help with insomnia?
Results show that overall synchrony in sleep-wake schedules among couples was high, as those who slept in the same bed were awake or asleep at the same time about 75 percent of the time.
Using their computational method, researchers simulated shifting sleep-wake schedules and the subsequent light interventions for realigning internal clocks with local time.