What happens as the ventricles relax?

• A. Blood begins to flow backward.
• B. Blood flows forward into the arteries.
• C. The atria contract to fill the ventricles.
• D. The heart stops beating.

Answer: (A)

During ventricular relaxation, the pressure in the ventricles falls. Blood in the arteries is moving back toward the heart, which causes the semilunar valves to close to prevent blood from flowing back into the ventricles. This brief backward flow helps seal those valves and signals the start of diastole. Once the semilunar valves are closed, the atrioventricular valves open and blood can flow passively from the atria into the ventricles, with atrial contraction often topping off ventricular filling. Forward flow into the arteries happens during ventricular contraction, not relaxation, and the heart does not stop beating during this phase.