The first physiological response to high environmental temperature is
Under mechanisms activated by heat cutaneous vasodilation comes first followed by sweating increased respiration, decreased heat production, anorexia, apathy, and ineia. Ref: Ganong&;s review of medical physiology; 23rd edition; pg: 285; Table 18-4.
Sweating
Vasodilatation
Decreased heat production
Non-shivering thermogenesis
Nervous system