Which statement best describes the local vascular response to heat applied to tissue?

• A. Local vasodilation and hyperemia
• B. Local vasoconstriction
• C. No change in local blood flow
• D. Local edema as the primary effect

Answer: (A)

Heat applied to tissue triggers dilation of local blood vessels, increasing blood flow to the area—a process called hyperemia. This rise in perfusion helps dissipate heat and brings more warm blood to the surface where heat can be lost to the surroundings. Mechanistically, heat causes direct relaxation of vascular smooth muscle, reduces sympathetic tone in the skin, and promotes release of relaxing factors from the endothelium (like nitric oxide) along with local metabolic byproducts (such as CO2 and adenosine) that further promote vasodilation. The net result is more blood in the area and a reddening from increased flow. In contrast, vasoconstriction would occur with cold exposure, and no-change or edema-focused explanations don’t capture the primary vascular response to heating.