Diastolic blood pressure represents the relaxation phase of the cardiac cycle.

• A. Systole
• B. Peak pressure
• C. Pulse rate
• D. Relaxation

Answer: (D)

During the cardiac cycle the heart alternates between contraction and relaxation. Systole is the phase when the ventricles contract and push blood into the arteries, producing the peak arterial pressure. Diastole is the relaxation phase when the heart muscle relaxes and the ventricles fill with blood, causing arterial pressure to fall to its minimum. Diastolic blood pressure, therefore, reflects this relaxation period. The other terms don’t fit: the peak pressure corresponds to systole, pulse rate is about heartbeats per minute rather than a pressure value, and the relaxation term here captures the phase during which diastolic pressure is measured.