Which statement about diastole is true?

Which statement about diastole is true?

• A. It is the phase of ventricular relaxation
• B. It is the phase of ventricular contraction
• C. It occurs after systole in all animals
• D. It does not involve the heart valves

Answer: (A)

Diastole is the ventricular relaxation phase of the cardiac cycle. During this time the ventricles relax after contracting, allowing them to fill with blood from the atria. The atrioventricular valves (mitral and tricuspid) are open to let blood flow into the ventricles, while the semilunar valves (aortic and pulmonary) are closed to prevent blood from flowing back into the heart. This is the opposite of systole, when the ventricles actively contract to push blood out to the body and to the lungs. The idea that diastole occurs after systole in the cardiac cycle is correct, though the exact timing can vary among species.

Diastole is the ventricular relaxation phase of the cardiac cycle. During this time the ventricles relax after contracting, allowing them to fill with blood from the atria. The atrioventricular valves (mitral and tricuspid) are open to let blood flow into the ventricles, while the semilunar valves (aortic and pulmonary) are closed to prevent blood from flowing back into the heart. This is the opposite of systole, when the ventricles actively contract to push blood out to the body and to the lungs. The idea that diastole occurs after systole in the cardiac cycle is correct, though the exact timing can vary among species.