Vasoconstriction refers to

• A. Blood flow to the extremities and skin is increased.
• B. Blood is directed away from vital organs.
• C. Blood is redistributed toward the brain during alertness.
• D. Blood flow is restricted from the extremities and skin, redirecting toward vital organs.

Answer: (D)

Vasoconstriction is the narrowing of blood vessels, which raises resistance and reduces blood flow to the areas affected. In a fight-or-flight situation, vessels in the skin and extremities constrict, cutting back flow there and redirecting blood toward vital organs and muscles that need oxygen and nutrients. This makes the description that blood flow is restricted from the extremities and skin, redirecting toward vital organs the best match. The other ideas describe vasodilation (increased flow to extremities/skin), or misstate the redistribution (blood away from vital organs), or oversimplify brain involvement.