Which statement best describes the effect of heat exposure on thermoregulation?

• A. In cold environments, sweating is predominant
• B. In hot environments, vasoconstriction and shivering predominate
• C. In hot environments, vasodilation and sweating predominate
• D. In cold environments, there is no change in skin blood flow

Answer: (C)

During heat exposure, the body mainly uses mechanisms to lose heat: vasodilation of skin blood vessels and sweating. When core temperature rises in a hot environment, the vessels near the skin dilate to bring more blood to the surface, increasing heat transfer to the environment. Simultaneously, sweat glands secrete sweat; as that sweat evaporates, it removes heat from the body. This combination—increased skin blood flow and evaporative cooling from sweating—is the dominant thermoregulatory response to heat.

In cold environments, sweating is not the main response. The body tends to conserve heat by constricting skin vessels (vasoconstriction) to reduce heat loss and by generating heat through shivering. The idea of no change in skin blood flow isn’t accurate either because vasoconstriction reduces skin blood flow to preserve core temperature.