(Image credit: Wikimedia Commons under Creative Commons licence)

When we are in a cold environment, our body shivers. This means that our body shakes (sometimes violently) and our teeth chatters. Why does our body do that?

Human bodies need to keep a constant temperature of about 36.9 degrees.

This is to prevent hypothermia and other effects of being too cold. Our brain thus keeps a very close watch on our body temperature and will try to warn us when the temperature drops.

Shivering is just one of the ways our brain signals to us that our body is too cold. When shivering, our muscles contract and expand at a very fast speed. Our jaw muscles will also shiver and that causes our teeth to chatter.

Another way of our body trying to warm up itself is by causing our hairs to stand on ends when we are cold. When our body feels cold, the muscles at the end of our hair shafts will contract. This causes our hairs to stand. By doing so,

the standing hairs form a layer of insulating air which helps to keep us warm.

These quick reactions of the body's muscles produce heat which then helps to warm up our body. It is also a physical sign for us to try and warm ourselves by covering with a blanket or taking a hot drink.

(Image credit: Wikimedia Commons under Creative Commons licence)