Fever, also known as pyrexia and febrile response, is defined as having a temperature above the normal range due to an increase in the body's temperature set-point. The increase in set-point triggers increased muscle contraction and causes a feeling of cold. This results in greater heat production and efforts to conserve heat. When the set-point temperature returns to normal a person feels hot, becomes flushed and may begin to sweat. Temperature is regulated in the hypothalamus. The hypothalamus works like a thermostat. When the set point is raised, the body increases its temperature through both active generation of heat and retention of heat.