Body temperature regulation in mammals

A mammal’s internal body temperature can change when it gains or loses heat. The brain coordinates responses that oppose these changes, keeping the internal temperature relatively constant rather than allowing it to follow every change in the surroundings.

Responses when the body is too warm

Sweat glands release sweat onto the skin. As the sweat evaporates, it takes heat from the skin, cooling the body.

Arterioles supplying capillaries near the skin surface dilate (widen). This increases blood flow near the surface, so more heat is transferred from the blood to the surroundings.

Responses when the body is too cold

Shivering produces heat through rapid, repeated muscle contractions.

Arterioles supplying capillaries near the skin surface constrict (narrow). This reduces blood flow near the surface, limiting heat loss to the surroundings.

These warming and cooling responses act in opposite directions: each opposes the departure from the normal internal temperature.