Which statement best describes vasoconstriction?

• A. Increase in diameter of blood vessels
• B. Stimulation of sweat glands
• C. Decrease in blood vessel diameter
• D. Enlargement of pores

Answer: (C)

Vasoconstriction is the narrowing of blood vessels due to the contraction of smooth muscle in their walls. This squeeze reduces the diameter of the vessel, which slows or limits blood flow through that vessel and can raise overall vascular resistance. The statement that describes a decrease in blood vessel diameter matches this process exactly, making it the best description. Increasing diameter would be vasodilation, not vasoconstriction. Stimulation of sweat glands or enlargement of pores relates to skin thermoregulation and skin surface features, not to changing the size of blood vessels.