AS Applied Science AQA Unit 2 Biology Key Terms

Aerobic - chemical reactions that require the presence of oxygen Alveoli - thin-walled microscopic air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place Anaerobic - process that does not require oxygen Arrhythmia - an abnormal rate of muscle contractions in the heart ATP - (adenosine triphosphate) main energy source that cells use for most of their work Atrioventricular Node - neurological tissue in the center of the heart that receives and amplifies the conduction of impulses from the SA node to the bundle of His Atrioventricular Valve - A valve in the heart between each atrium and ventricle that prevents a backflow of blood when the ventricles contract. Atrium - upper chamber of the heart that receives and holds blood that is about to enter the ventricle Baroreceptors - Receptors in the body that detect changes in blood pressure. Blood Pressure - measurement of the force exerted by the heart against the arterial walls when the heart contracts and re