What term describes narrowing of arteriolar walls?

• A. Vasodilate
• B. Vasoconstrict
• C. Venodilate
• D. Venoconstrict

Answer: (B)

Narrowing of the arteriolar walls happens when the smooth muscle in their walls contracts. This action reduces the radius of the arterioles, which is called vasoconstriction. Because the radius appears to the fourth power in the equation governing flow, even a small decrease in diameter greatly increases vascular resistance and can raise blood pressure, while reducing blood flow to tissues. The opposite process, widening of the arterioles, is vasodilation. Terms involving veins (venodilation, venoconstrict) describe veins, not arterioles, so they don’t fit here. In the given option, the concept is captured by vasoconstrict (the action form of vasoconstriction).