I'm So (yawn) Tired!

Sometimes I stay up late and watch one of my favorite movies. When the final credits roll, I groggily make my way to bed. The next morning when I wake up, I am so tired. I cannot stop yawning! Why do we yawn when we are tired? Yawning is a reflex. It is something that our body does without us even having to think about it. Some people believe that our bodies yawn when we need more oxygen. They think that when there is not enough oxygen in our lungs, the nerves in our body tell the muscles in our mouth to open wide. When we do this, we take in an extra large breath of air. This .....


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