Heart beat

A heartbeat is a coordinated, electrical, and muscular process driven by the sinoatrial (SA) node (the heart's pacemaker), which sends electrical impulses causing the upper chambers (atria) to contract, followed by the lower chambers (ventricles) to pump blood. This cycle, which repeats 60–100 times per minute, consists of contraction (systole) and relaxation (diastole), regulated by valves that ensure one-way blood flow.