Hi I'm Craig. I've never worn braces because I think my gap tooth is cute and this is Mental Floss on YouTube. Today I'm gonna answer A Bond Unboken's big question: Why do our teeth chatter when we're cold?

Well A Bond Unbroken, your body doesn't love being cold so when it gets cold it does some stuff to try to get warm again. Teeth chattering is one of those things. I'm going to tell you how that works today. Let's get started. (Zips up hoodie and puts up hood) Brr.

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Humans are warm-blooded mammals. Our bodies prefer an internal temperature of 98.6 degrees Fahrenheit or bladady-bla degrees Celsius 'cause I don't  know 'cause I'm just a dumb American who doesn't understand that Celsius is what the majority of the rest of the world uses, not like you were upset about that in a previous video when I made a joke like that were you. Hrrr. Or 37 degrees Celsius. (0:51)

Their ability to stay at around that temperature is known as thermoregulation and it happens thanks to things like the circulatory system and the digestive system. So when your skin gets colder than expected, your body takes note because it really doesn't want to get hypothermia. Then it does things like decreasing sweat production and decreasing the size of blood vessels towards the body's surface. (1:09)

The temperature receptors in your skin also get involved. They send signals to the hypothalamus in the brain which is what controls body temperature. It's basically your body's own personal thermostat so you don't need to go swallowing a thermostat, OK. You got one right up there in the hypothalamus, young whippersnapper. (1:23)

The hypothalamus contains something known as the shivering center which causes involuntary shivering. That shaking you experience happens because the body's muscles are contracting and relaxing repeatedly. Or you're making a stupid joke like me. Those muscles include your face muscles and when your face muscles begin to shiver, you guessed it, teeth chattering is a side effect of that. (1:42)

In 2014, a group of scientists who work for the National Institutes of Health studied how 10 adults reacted to cold temperatures. The scientists concluded that shivering actually boosts metabolism, like exercise does, so shivering is kind of good for you. Hrrr. I should mention that shivering is not a recommended workout. I don't want a bunch of people going out in the cold and getting hypothermia because that's not actually going to help you in the long run. You know what might help? A long run. (2:04)
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Thanks for watching Mental Floss on YouTube which is made by these shivering people. If you have a big question of your own leave it in the comments and it might just get answered. I'll see you next week. Hrrr. Hrrr. Hrrr.
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