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What's behind this mysterious epidemic of yawning? First, let's look at what a yawn is. Yawning is an involuntary action that causes us to open our mouths wide and breathe in deeply. We know it's involuntary because we do it even before we are born. Research shows that 11-week-old fetuses yawn. There are many parts of the body that are in action when you yawn. First, your mouth opens and jaw drops, allowing as much air to be taken in as possible. When you inhale, the air taken in is filling your lungs. Your abdominal muscles flex and your diaphragm is pushed down. The air you breath in expands the lungs to capacity and then some of the air is blown back out.
Interesting Yawning Facts
* The average yawn lasts about six seconds.
* Your heart rate can rise as much as 30 percent during a yawn.
* 55 percent of people will yawn within five minutes of seeing someone else yawn.
* Blind people yawn more after hearing an audio tape of people yawning. * Reading about yawning will make you yawn.
* Olympic athletes often yawn before competition.
Scientists do not purport to know all of the biological mechanisms of the yawn, but tend to agree that a yawn is an involuntary respiratory reflex, which regulates the carbon dioxide and oxygen levels in the blood. Technically, a yawn is the reflex opening of the mouth followed by the deep inhalation and slow exhalation of oxygen. The very act of yawning is but one of a number of involuntary reflexes controlled by the spinal and nerve centers. Scientists speculate that the onset of a yawn is triggered either by fatigue, or by sheer boredom as, at those times, breathing is shallow, and little oxygen is carried to the lungs by the oxygen-toting cardiovascular system. When one yawns, his or her alertness is heightened, as the sudden intake of oxygen increases the heart rate, rids the lungs and the bloodstream of the carbon dioxide buildup, and forces oxygen through blood vessels in the brain, while restoring normal breathing and ventilating the lungs.
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.
The psychologists, who studied yawning in college students, concluded that people do not yawn because they need oxygen, since experiments show that raising or lowering oxygen and carbon dioxide in the blood fails to produce the reaction. Rather, yawning acts as a brain-cooling mechanism. The brain burns up to a third of the calories we consume, and as a consequence generates heat.
According to Gallup and Gallup, our brains, not unlike computers, operate more efficiently when cool, and yawning enhances the brain’s functioning by increasing blood flow and drawing in cooler air.
Spying someone yawning often makes us yawn. Now, a new study shows your canine buddy can catch yawns from you, too. The results suggest domestic dogs have the capacity for a fundamental form of empathy, the researchers say....
Originally posted by BluegrassRevolutionary
I remember once learning that yawning is a hold over from evolution. If my memory holds, it was stated that animals yawn, ironically, to wake themselves up. This explains why yawns are contagious. When an animal in a group yawns, thus forcing the other animals in the group to yawn, it helps to ensure that someone is staying awake, and thus, keeping watch over the pride, herd, or flock. However, I am pretty sure that it was at least a decade ago that I learned this and given that science is continually changing, this opinion may be out of date. Actually, in typing this post I think it may have been that yawning was a way for members in a group of animals to give an indication to other members of the group that they may fall asleep soon and that they would no longer be keeping watch, thus ensuring that someone would take over their duties. But again, this theory may be out of date.
Originally posted by KRISKALI777
reply to post by baseball101
We yawn to equalise pressure between the outer and inner ear, via the eustacian Tubes. Loss of pressure is more apparent when tired.