View source for 36. Warm-defense and heat-induced disorders

The body’s defence against heat includes:

* Skin vasodilation – increases heat loss by allowing heat to conduct away from the skin, increasing ''conduction''
* Sweating – as the sweat evaporates heat is lost by ''evaporative cooling''
* Arrector pili muscles relax – the flat hairs on the skin increase air flow around skin, increasing ''convection''

To lose as much heat as possible, cardiac output increases (probably due to sympathetic activation), which, in combination with skin vasodilation, leads to larger amounts of blood being exposed to the relatively cooler air.

The warm-defence is different between people who live in warmer and colder countries. Those that live in warmer countries are better adapted and sweat less than a non-adapted individual would under the same circumstances.

The humidity of the air is important in the warm-defence. The higher the humidity the harder it is for sweat to evaporate, meaning that sweating is less effective in causing heat loss.

As described in topic 22 would the BMR by itself cause the body temperature to increase by 1°C every hour. From this it’s easy to understand that normal heat loss is very important in preventing hyperthermia.