The stage of the heart cycle in which the heart muscle is relaxed, allowing the chambers to fill with blood.

• A. Diastole
• B. Systole
• C. Blood Pressure
• D. Diastolic Pressure

Answer: (A)

During the cardiac cycle, the heart alternates between a relaxation phase and a contraction phase. The relaxation phase is when the heart muscle is relaxed and the chambers fill with blood. In this phase, the atrioventricular valves are open, allowing blood to flow from the atria into the ventricles, with a final push from atrial contraction at the end. This relaxation phase is diastole. It contrasts with the contraction phase, when the ventricles squeeze blood out. Terms like diastolic pressure refer to the arterial pressure during this relaxation period, but the stage itself is diastole.