Major thermoregulatory defenses: Sweating, vasoconstriction, shivering

The major thermoregulatory defenses in humans. The threshold (triggering core temperature) for each response is shown on the Y-axis. Temperatures between the sweating and vasoconstriction thresholds define the interthreshold range, usually a few tenths of a degree Celsius (°C), temperatures that do not activate thermoregulatory defenses and thus define normal core temperature (dashed oval). Sweating activates active pre-capillary vasodilation, which moves heat towards the skin surface for dissipation to the environment. The shivering threshold is 1°C below the vasoconstriction threshold; by the time humans begin to shiver, they are thus already fairly hypothermic.