Which of the following describes the dilation and contraction of blood vessels?

The correct answer is vasodilation, which refers to the process where blood vessels expand or widen. This occurs when the smooth muscles in the vessel walls relax, leading to an increase in blood flow and a decrease in blood pressure within the vessels. Vasodilation is essential for regulating blood flow to various tissues, responding to increased metabolic demands, and helping to control body temperature.

The terms related to blood vessel activity include vasoconstriction, which involves the narrowing of blood vessels, leading to reduced blood flow and increased blood pressure. Vasoactivity is not a standard term commonly used in the context of blood vessel dilation and contraction. Vasotension also does not accurately describe the mechanism of blood vessel diameter changes; it relates more to the tension within the vessel walls rather than their dilation or contraction. Thus, vasodilation is the most precise term describing the widening of blood vessels.