Temperature control is important for the normal operation of enzymes and cells.

The brain has a key role in co-ordinating this function. Near the bottom of the brain is a place called the hypothalamus, which monitors a number of key things in the body, including temperature.

When the hypothalamus detects a change in the temperature of the blood it sends impulses down neurones to the skin.

Why is the skin important?

The skin is described as the biggest organ in the body. An average person has about 2 square metres of skin. (Try measuring yourself to check!)

The skin keeps our water in, has a layer of fat to keep us warm and is tough enough to keep out microbes that might cause disease. It is also a great place for nerve receptors.

In addition to all of this, the skin has some interesting mechanisms to help control temperature. It can alter blood flow, hair position and the amount of sweating.

What happens when your temperature starts to move away from the normal 37 degrees?

When we get too hot the hypothalamus sends impulses to the skin which cause 3 things to happen:

1. Our hairs lie flat: so letting more heat out.
2. We sweat: the evaporation of this cools us down.
3. More blood goes through the skin: this acts like a radiator to radiate out heat.

We also tend to take off some clothing to allow more heat to escape.

If we get too cold the hypothalamus sends other impulses so that the reverse happens:

1. Our hairs stand up: this traps a layer of air which acts like an insulator.
2. We stop sweating: this stops the heat loss by evaporation.
3. less blood goes through the skin: the skin will appear paler and colder.

As well as the above, impulses reach the liver and cause it to increase respiration and so create more heat. Like turning up the central heating!

And we put more clothes on. This traps an insulating layer of air near our bodies.