What effect does vasoconstriction have on vascular resistance?

Vasoconstriction refers to the narrowing of blood vessels, which occurs when smooth muscle in the blood vessel walls contracts. This process has a direct impact on vascular resistance. When blood vessels constrict, the diameter of the vessel decreases. According to Poiseuille's Law, vascular resistance is inversely related to the fourth power of the radius of the blood vessel. Therefore, even a small decrease in vessel diameter results in a significant increase in resistance to blood flow.

This mechanism is critical in various physiological scenarios, such as when the body needs to redirect blood flow to vital organs or maintain blood pressure during periods of low volume or shock. Hence, when vasoconstriction occurs, it increases vascular resistance, making it the correct interpretation of the effect of this physiological response.