More sweat is produced by sweat glands. Sweat travels up sweat ducts and out of sweat pores onto the surface of the skin. Heat from the skin causes the water in sweat to evaporate, cooling you down.
Too cold (sweat)
Less sweat produced and it is not released at the sweat pore.
Too hot (blood vessels)
Vasodilation - blood vessels become wider, increasing blood flow to the surface of the skin. This allows more heat to be lost from the blood by radiation.
Too cold (blood vessels)
Vasoconstriction - diameter of blood vessels become narrower. Less blood flows to the surface of the skin and therefore less heat is radiated away from the skin.
Too hot (hairs)
Erector muscle relaxes, hairs lie flat, less insulating air is trapped so more heat lost.
Too cold (hairs)
Erector muscle contracts pulling hairs up. More insulating air trapped so less heat lost.
Too cold (whole body)
Shivering generates heat from muscles contracting and relaxing.
