Increasing the volume of circulating blood has what effect on blood pressure?

• A. It decreases blood pressure.
• B. It has no effect.
• C. It increases blood pressure.
• D. It only affects diastolic pressure.

Answer: (C)

Increasing circulating blood volume raises arterial pressure because it boosts venous return to the heart, increasing preload. The greater preload stretches the heart more and enhances stroke volume via the Frank-Starling mechanism. If systemic vascular resistance stays the same, the higher cardiac output lifts the mean arterial pressure, so blood pressure increases. This effect influences both systolic and diastolic pressures, not just diastolic. Over time, the kidneys can adjust fluid balance to reestablish pressure, but acutely more circulating volume elevates blood pressure.