The brain controls the activity of the sweat glands and the arterioles in the skin which dilate (vasodilation) to allow more blood to flow through the skin. The skin receives more heat which is lost by radiation, convection and conduction.The sweat glands are also stimulated. There is a greater production of sweat.
As more sweat evaporates from the surface of the skin, more latent heat is removed from the body. This is an efficient means of losing heat. Rapid breathing helps to remove heat and the metabolic rate of the body slows down, so that less heat is produced. The result is that the body temperature remains constant.
The extra heat produced during vigorous muscular activity is removed at a greater rate so that there is no appreciable rise in body temperature.The same reaction is brought about by a rise in the external temperature.
If the temperature of the surroundings is higher than body temperature, the mammal will tend to absorb heat rather than lose it. Under this condition the only way it can lose heat is by evaporation of sweat from its body.
