True or false: Diastole is the phase where the ventricles contract.

• A. True
• B. False
• C. Not applicable
• D. Both true and false

Answer: (B)

Diastole is the relaxation phase of the cardiac cycle, when the ventricles fill with blood from the atria. The ventricles contract during the other phase, systole, which pumps blood out to the lungs and rest of the body. So this statement is false. During diastole the atrioventricular valves are open and the semilunar valves are closed; during systole the ventricles contract, the AV valves close, and the semilunar valves open to eject blood. Understanding this helps you see why diastole is about filling, not contraction.