Human Body 101: Muscle Facts #20
Your body needs to keep a core temperature of about 36.9°C. To prevent hypothermia and other consequences of a chilled core, your brain monitors temperature very closely.
If the surface of your skin gets too chilly, skin receptors send signals to the brain, which sets into motion a series of warming tricks .
Shivering is one such tactic, in which your muscles contract and expand in speedy bursts. In addition to quaky limbs, your jaw muscles might begin to shiver, making your teeth chatter.
This twitching exercise produces heat, which helps to raise body temperature. It's also your signal to find a toasty haven and a warm drink.