The Cardiac Cycle
The pathway of the electrical impulses can best be seen by looking in detail at a single heart cycle. The period from the beginning of one heartbeat to the next is called the cardiac cycle. The cardiac cycle consists of a period of contraction, called systole, followed by a period of relaxation, called diastole. During the diastole phase, your heart relaxes and allows blood to flow into the two ventricles; during the systole phase, the ventricles contract, driving blood to the lungs and throughout the body. In a healthy, resting adult, the heart beats about 60 to 80 times a minute, so that the cardiac cycle lasts only about .8 seconds.
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