The Circulatory System — Biology STD 10 — Question

Cardiac Cycle:
It is the sequential phenomenon of contraction and relaxation of the heart. The action potential causes atria and then ventricles to undergo contraction (systole) followed by their relaxation (diastole). Systole forces blood to move from the atria to the ventricles and to the pulmonary artery and the aorta, then. The heart beats 72 times in a minute. So several cardiac cycles are done per minute. The duration of the cardiac cycle is 0-8 seconds. Two heart sounds are heard by a stethoscope during each cardiac cycle.