Which statement correctly differentiates systolic blood pressure from diastolic blood pressure?

• A. Systolic is during relaxation; diastolic during contraction
• B. Both are measured during systole
• C. Systolic is the pressure during ventricular contraction; diastolic is the pressure during relaxation between beats
• D. Diastolic is the pressure during contraction

Answer: (C)

Systolic pressure reflects the force in the arteries when the heart is actively pumping blood (ventricular contraction), while diastolic pressure is the force in the arteries when the heart is relaxed between beats. The peak pressure occurs during systole as the left ventricle ejects blood into the aorta; the trough occurs during diastole when the heart is filling and at rest between beats. This is why blood pressure is expressed as a systolic over a diastolic value (for example, 120/80 mmHg). Statements that place systole on relaxation or claim both values are measured during contraction misstate the timing of the cardiac cycle, and assigning diastolic pressure to contraction is also incorrect.