Which body system is NOT primarily involved in skin heat regulation?

• A. Nervous system
• B. Circulatory system
• C. Integumentary system
• D. Endocrine system

Answer: (D)

Heat regulation on the skin is controlled mainly by immediate nervous system responses that direct sweat production and the tightening or widening of surface blood vessels. The circulatory system moves blood to and from the skin, carrying heat with it, so it plays a central role in heat transfer. The integumentary system is the actual site where heat exchange happens—sweat glands produce cooling from evaporation, and surface vessels adjust heat loss. The endocrine system, while it can influence overall metabolic heat production through hormones, does not drive the rapid, localized adjustments in sweating and skin blood flow that regulate skin heat. So the endocrine system isn’t the primary player in skin heat regulation.