why do you yawn when u get tired?

Answer 1

"Why do we yawn? Dr. Barry Make, a pulmonologist at National Jewish Medical and Research Center in Denver, says the answer is not because we are tired or bored — although that’s the common perception. Read on for his explanation.

The most plausible explanation, and the one that is taught in medical school, is that we yawn because oxygen levels in our lungs are low.



THE TRUTH IS that we don’t completely understand why people, or animals for that matter, yawn. It’s widely assumed that yawning occurs because we are tired or bored or because we see someone else doing it, but there isn’t any hard evidence to support these beliefs.

The most plausible explanation, and the one that is taught in medical school, is that we yawn because oxygen levels in our lungs are low. Studies have shown that during normal, at-rest breathing, we don’t use anywhere near our lung capacity; for the most part, we just use the air sacs at the bottom of the lungs. If the air sacs, called alveoli, don’t get fresh air, they partially collapse and the lungs stiffen a bit. As a result, it’s believed, our brain prompts the body to either sigh or take a yawn to get more air into the lungs.

But certain aspects of yawning remain even more mysterious. Fetuses, for instances, have been observed yawning in the womb, yet it’s known that they don’t take oxygen in through their lungs. And yawning seems to be a symptom of multiple sclerosis and other medical conditions, for reasons unclear.

Another puzzling phenomenon is that some male animals, men included, yawn in association with penile erection (although it’s presumptuous to assume they’re bored with their sex lives)."

Answer 2

i read somewhere a few years ago that yawns are caused by a lack of oxygen in the brain. i don't understand what that has to do with being tired though. maybe because the body slows down when it needs rest, and oxygen doesn't flow as quick.

Answer 3

See the links below for some fun medical and yawn facts.

Answer 4

you actually don't yawn when you're tired, yawning is an auto-reflex of your lungs to inhale more oxygen when you lack them. People do yawn to get more oxygen into their lungs :) peace out!

Answer 5

you dont actually yawn when your tired. yawning is due to a lack of oxygen. the lack of oxygen is due to you being tired though...

Answer 6

It's your body's way of gaining more oxygen. Your tired, your body needs more oxygen than usual, so it "yawns".

Answer 7

I have always been told You yawn because you arent getting enough oxygen to the brain. So you Yawn to get what you are lacking. I dunno. That is what I have been told.

Answer 8

Some because its it increase blood flow...
others say its a involuntary action that is caused when the body is fatigued...
I believe two are related....fatigue and the body's way of increasing blood flow to increase energy.