Glossary A

Glossary A

Atomic weight refers to the number indicating the weight of an atom relative to a weight of one for a proton

Atonia refers to lack of normal muscular tension or tonus

Atonic seizures refer to a kind of seizure which are characterized by a sudden loss of muscle tone and may result in a fall. They last no longer than 15 seconds while the person remains conscious.

ATP (Adenosine Triphosphate) refers to a compound that stores energy and is also used as a neuromodulator

ATP-PC system is a term used to describe the metabolic pathway involving muscle stores of ATP and the use of phosphocreatine to rephosphorylate ADP. This pathway is used at the onset of exercise and during short-term, high-intensity work.

ATPase refers to enzyme capable of breaking down ATP to ADP + Pi + energy.

Atria refer to the upper and thinner-walled chambers on each side of the heart

Atrial fibrillation refers to a disorder that upsets the heart's rhythm, which may cause it to not pump enough blood to meet the body's needs. A normal heart contracts and relaxes to a regular beat. In Atrial fibrillation, the heart contracts at a very irregular and sometimes very rapid rate, which results in an irregular heart rhythm.