Why Do Teeth Chatter in the Cold?

You must have come across headlines like "Bone-chilling cold disrupts daily life" in the newspaper. But cold essentially does not shake your bones. It feels that way when the chill has reached right to your bones through your flesh, but all of us know the phenomenon of chattering teeth. On a chilly day, our teeth knock against each other out of our will. Why does this happen?

Warm-blooded animals, also known as endotherms, produce body heat internally. Most mammals, including humans, and few insects are endothermic. They cannot perform their bodily functions unless the body temperature is maintained within a range. This is called thermoregulation, or "heat control."

We do a lot of physiological and habit-forming actions to increase the body's temperature. Shivering is a physiological activity. Wearing warm clothes is a habit.

Imagine not wearing warm clothes in freezing weather and not doing anything to keep yourself warm. Under these conditions, your brain will have to send signals to your body to raise its temperature. This is because if body temperature falls below normal, then normal function of other organs may stop and can have a serious effect on your brain.

The part of your brain that checks on body temperature is the hypothalamus. It keeps checking the temperature of your blood constantly. When you start to feel cold, it sends signals throughout the nervous system to your skin. The signals cause the attached muscles to each hair follicle to erictor making your hair to stand on end. This traps a thin layer of air between the skin and the atmosphere that acts like an insulator, conserving a little body heat. This mechanism helps hairy animals to keep warm.

Humans are, however, not as hairy as bears. As we don't have the density in our hair for this mechanism to work, this is not very effective against the cold. At this point, the brain sends another signal to all the muscles in the body to contract. Contractions in muscles can produce heat at a fast rate, so the body starts to shiver. The jaw muscles, along with the remaining limbs, contract and result in chattering of teeth.

In other words, if your teeth start to chatter in cold, this simply means you need to put on more warm clothes right now. This reaction, though nothing out of the ordinary, but ignoring such cautions given by the brain is far from wisdom.