Thermoregulation is the process by which the body maintains a steady temperature. The body can detect temperature changes from sensitive nerve endings in the brain and near the surface of the skin called thermoreceptors.
The body tries to heat or cool itself based on readings of the thermoreceptors.
When the body is not able to lower a high temperature effectively, a heat-related illness occurs. Cold-related injuries, such as frostbite, occur when body temperature falls too low.
WebMD Medical Reference from Healthwise