The widening of blood vessels, which increases blood flow to the skin and helps to dissipate heat.

• A. Vasodilation
• B. Vasoconstriction
• C. Hypertension
• D. Tachycardia

Answer: (A)

Vasodilation is the widening of blood vessels. When the body needs to lose heat, the smooth muscle in the skin’s arterioles relaxes, increasing blood flow to the skin. This brings warmer blood to the surface where heat can be released to the environment, cooling the body. This process helps dissipate heat through radiation, convection, and evaporative cooling as sweat facilitates cooling. It’s opposite to vasoconstriction, which reduces skin blood flow to conserve heat. Hypertension and tachycardia describe high blood pressure and rapid heart rate, not the specific widening of vessels to cool the body.