Maintaining body temperature - Thermoregulation
There are sensors throughout the body called thermoreceptors if they detect a change in the body’s temperature they send signals to the hypothalamus at the base of the brain. This then sends signals to the skin and muscles to respond. Too cold and the signals tell the muscles attached to the hairs on the skin to contract and make the hairs stand up to trap a layer of air as insulation. They reduce sweating and contract the blood vessels close to the skin to divert it deeper into the skin to retain heat. If it’s very cold, the muscles will begin to twitch and we shiver to make heat.
Too hot and the sweat glands are signalled to increase sweating, the blood vessels near the surface of the skin dilate (open up) and the muscles attached to the hairs relax so they lay down to allow heat to escape.