Hey Doc, why do I yawn when I am tired?
Dr. Charlotte Grayson: People have been asking that question for years, and you know what, you have stumped me, I don't know why people yawn but I'm not alone on that. No one has the real answer but there are a lot of theories out there.
One hypothesis says, that when you are tired or board your breathing slows down, so carbon-dioxide builds up in your blood, that means less oxygen gets in, the message that your oxygen deprive raises to your brain, which then sends out a wake up call to the rest of your body. And trying to get back in balance your brain tells you to open your mouth wide to suck more oxygen in and then as you exhale out that extra carbon-dioxide. Another school of thought cause yawning a type of work out for the lungs.
Stretching them and keeping them limber or may be yawning just helps distribute a substance called suffocative which keep the lungs well lubricated. None of these ideas has been proven but one thing is for sure yawning is contagious. Try yawning in a room full of people and see what happens, you are likely to set of an open mouth chain reaction with stump the doc and I'm Doctor Charlotte Grayson.
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