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What Happens When You YAWN?

When you feel sleepy, you yawn.

When you feel bored, you yawn.

The kid next to you yawns. You yawn, too--even if you are wide awake and having a good time.

So why are you yawning? Let's check it out.

Your body needs oxygen. You get oxygen by breathing in air.

Your body also needs to get rid of carbon dioxide. When you breathe out, this carbon dioxide is carried out of your body.

Your brain makes sure you have the right amount of oxygen and carbon dioxide in your body. If you have too much carbon dioxide in your body, your brain tells your mouth to open. It tells your throat to tighten. And it tells your chest to take a deep breath.

In other words, your brain makes you yawn. Oxygen rushes ill. Carbon dioxide rushes out. And everything goes back to normal again.

How do you get too much carbon dioxide in the first place? In a crowded room, carbon dioxide builds up. You breathe it in, get too much carbon dioxide and ... YAWN!

But why do you yawn when you see other people yawning? If you are in the same room, you are probably getting too much carbon dioxide, just as they are.

Scientists wonder if people might have another reason for yawning.

Baboons yawn to warn one another to stay out of their territory.

Doctors have noticed that adult humans also yawn at one another, even when they are not in a crowded room.

So the next time your teacher yawns, ask her if she's tired--or if she just wants you to stay out of her territory!
COPYRIGHT 1999 Children's Better Health Institute
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1999 Gale, Cengage Learning. All rights reserved.

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Author:Stickney, Nancy
Publication:U.S. Kids
Article Type:Brief Article
Date:Jan 1, 1999
Words:272
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