What happens when blood volume is lost from the body?

• A. Arterial Blood Is Diverted to the Skin and Muscles
• B. Widespread Vasodilation Causes Blood Pressure to Decrease
• C. The Veins Dilate to Increase Systemic Perfusion
• D. The Arteries Contract to Increase the Blood Pressure

Answer: (D)

Loss of blood volume triggers a rapid compensatory response to maintain arterial pressure. When volume drops, venous return and cardiac output fall, causing arterial pressure to decline. The body then activates the sympathetic system, leading to constriction of the arteries. This increases systemic vascular resistance, helping to raise mean arterial pressure and preserve blood flow to vital organs like the brain and heart. Veins constricting could help with venous return, but dilation would lower return and worsen hypotension, and widespread vasodilation would further drop blood pressure. Redirecting blood flow to the skin and muscles isn’t the primary protective action in acute blood loss. The key protective mechanism is arterial constriction to increase blood pressure.