Explain Cardiac cycle?
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The cardiac cycle is the sequence of events in one heartbeat.
It can be divided into three stages:
1) Diastole: the chambers of the heart (atria and ventricles) are relaxed and filling up with blood from the veins. The atrioventricular valves (bicuspid on the left and tricuspid on the right) are open and the semilunar valves (pulmonary and aortic) are closed. This stage lasts for about 0.4 second.
2) Atrial systole: the atria contract and top up the ventricles. This takes about 0.1 second.
3) Ventricular systole: the ventricles contract and pump blood out of the heart into the arteries. During this stage the atrioventricular valves are closed and the semilunar valves are open. This takes about 0.3 second.
The total cycle takes about 0.8 second while the subject is resting. This gives a heart rate of about 75 beats per minute.