How do our bodies regulate heat?

As warm-blooded organisms we have the capacity of maintaining a constant inner ‘operating temperature’, independent of surrounding environmental conditions. This gives us the advantage of being able to maintain our level of activity even during the cold season, unlike cold-blooded animals, which have difficulty staying active at low temperatures. The human body’s optimum internal operating temperature is about 37 °C, a level also referred to as normal body core temperature. Researchers differ somewhat as to what the actual body core temperature is and where this can be best measured. High temperatures predominate in the liver for instance, which serves as the body’s biochemical laboratory. Rectal temperature measurement is still today considered the most reliable method.

Biochemical processes in the organs are carried out the most efficiently at about 37 °C. Yet the efficiency level is still only moderate, between 40 and 60 percent depending on the area of metabolism. The remaining energy is given off as ‘caloric energy’ from biochemical processes. Modern electric motors by comparison attain an efficiency level of more than 90%. In other words, 90% of the invested electricity is actually converted into kinetic energy. Only 10% is lost as heat.

In order for the body to eliminate excess heat in a regulated way, heat from within the body is transported by the blood to the extremities and the skin. This thermal energy is then given off through the skin to the environment in the form of infrared C radiation (heat emission). This process cools the blood, which then flows back into the interior of the body. Heat emission can thus be controlled through blood circulation to the periphery of the body and the skin. When heat needs to be given off, circulation in the periphery is increased and the skin appears red. If this is not enough, perspiration sets in. Sweat evaporates, producing a cooling effect, whereby the required thermal energy is taken from the skin - cooling of the skin and blood results. Sweat drops thus have no benefit for regulating temperature. When it is too cold, circulation in the periphery is reduced to a minimum in order to keep as much heat as possible in the body. Muscles feel stiff and the skin appears pale and cold. If we are then still cold, we begin to tremble: our muscles are put to work to generate additional warmth (active heat production).