The time of cardiac cycle in different types of mammals varies along with the rate of heart beat. It is in reverse ratio of the rate of heart beat, eg, in man, the rate of heart beat is about 72 times per minute. Hence, the time of a cardiac cycle is 60/72=0.8 seconds approx. The time taken, respectively in systole and diastole of atria is 0.1 and 0.7 seconds and that of ventricles is 0.3 and 0.5 seconds.