Diastole is best described as when the heart relaxes to receive blood.

• A. During Atrial Systole.
• B. During Ventricular Systole.
• C. During Diastole.
• D. Immediately After Contraction.

Answer: (C)

The main concept is the relaxation phase of the heart cycle, when the chambers fill with blood. During diastole, the ventricles and atria relax, the atrioventricular valves are open, and blood flows from the atria into the ventricles. This is the period between heartbeats when the heart receives blood to prepare for the next contraction. Atrial systole is the final push by the atria to top off ventricular filling and occurs during diastole, but the overall phase described by diastole is the relaxation and filling phase. Ventricular systole, by contrast, is when the ventricles contract to eject blood. Immediately after contraction could hint at the start of diastole, but the standard definition of diastole is specifically the relaxation phase during which the heart receives blood. So describing diastole as the heart relaxing to receive blood is correct.