7.17—Homeostasis and thermoregulation

When body temperature rises, vasodilation and sweating increase heat loss; when it falls, vasoconstriction, shivering and raised metabolic rate reduce heat loss or generate heat. Receptors and effectors maintain a narrow operating range for enzymes.

Vasoconstriction reduces heat loss rather than directly warming the blood. Sweating works by evaporation, so humidity changes its effectiveness.

In humid air, sweat may remain on the skin while evaporation slows; in cold air, vasoconstriction diverts blood from surface capillaries and shivering raises respiration.

Thermoregulation is not a single “set temperature” response and skin redness does not itself mean core temperature is safe.