Fast heart rate: Tachycardia means fast heart beat. Sinus node is the structure where normally heart rhythm and beat is originated, and it naturally responds to stimuli when the heart needs to beat faster. Inappropriate sinus tachycardia is when the heart is beating fast, when it shouldn't. ...Read more.
The atom is the smallest subdivision of an element which still retains the properties of that element. In fact, a very good definition of an atom is: the smallest part of an element that can enter into a chemical combination. There are around 118 elements known to man, of which 20-30 are really, really important.he parallel definition (to the element one above) for the molecule is: the smallest part of a compound that can enter into a chemical combination. Another definition, equally good, is that a molecule is the smallest stable part of a compound. Water is a typical example of a compound.
The Building Blocks of Matter All matter, from a rock to an animal to the magma at the center of the Earth, is made from different combinations of 92 naturally occurring substances known as elements. The smallest quantity of an element that still exhibits the characteristics of that element is known as an atom. One atom of carbon, for example, is the smallest piece of matter that still retains the chemical and physical characteristics of carbon.