How the Heart’s Beat Is Controlled

The heart’s beat is controlled by a repeating electrical pattern called the cardiac cycle. It combines contraction, or systole, with relaxation, or diastole. This rhythm keeps blood moving through the heart in a steady sequence.

The cycle begins when electrical signals leave the sinoatrial, or SA...

The heart beats rhythmically in a sequence called the Cardiac Cycle, a rapid coordination of contraction, systole, and relaxation, diastole. An electrical signal sent from the sinoatrial node, near the right atrial wall causes both atria to simultaneously contract and push blood into the ventricles.

When the pulse reaches the atrioventric...