The sequence of events, lasting for less than a second, that make up each beat of the heart. A heartbeat has 3 phases. In diasystole, the heart relaxes. During atrial systole, the atria contract, and in ventricular systole, the ventricles contract. The sinoatrial node (the heart’s pacemaker) regulates the timing of the phases by sending electrical impulses to the atria and ventricles.
Cardiac cycle |
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