Why do humans yawn?
A very interesting topic which was brought up during a conversation I had this morning with a friend.
Why do humans yawn? Ever wondered about it?
Many would claim that they know the answer, and some egoistic people might say "Cos we lack of oxygen lah! Simple things like that also dunno..." Ok, just in case your self-esteem has been brought down to the negative levels, think Hmm...do these people know then? Are they right, proving that we're really that dense?
This was the first thing I decided to do, after washing up of cos (duh)...to find out the reason to why humans (even animals!) yawn.
Unfortunately, there's insufficient research being done on yawning, and no one really knows the real reason for it. However, suggestions have been made to why.
Wait wait..don't go "aiyah.....chey...."...cos I'm gonna tell you how you can "slap" those people who think they are some whiz kid as they try to bring you down with their "lack of oxygen" theory.
Apparently, their suggestion of the oxygen lack isn't totally invalid, BUT it is incorrect!!!! *Yay*
Perhaps it's wise to consider abt this "oxygen lack" theory first. It is assumed that our body makes yawning a way to rid excess carbon dioxide and to increase oxygen in our body. When people are bored or tired, they usually yawn, and that's because their breathing rate slows down. This results in lesser oxygen getting to the lungs, and as a result of the increase in carbon dioxide concentration in the blood, a signal is transmitted to the brain, triggering yawns to occur. Makes sense? Sure it does huh..
In 1987, Dr Robert Provine and his research team decided to carry out an experiment to test this theory. He did this by giving college students different concentrations of gases to inhale for 30 minutes, and calculated the number of times they yawn. For those who inhaled 100% oxygen or carbon dioxide of above normal concentrations, their breathing rate increased, but the number of yawns were indifferent from those who inhaled normal air.
They then went on with their research by having people to exercise. The breathing rate increased, but there was no change in the number of yawns before and after exercise!
Mark A. W. Andrews, the Associate Professor of Physiology and Director of the Independent Study Program at the Lake Erie College of Osteopathic Medicine, said that lungs do not necessarily sense oxygen levels. Fetuses yawn in utero although their lungs are not ventilated yet. If there is no ventilation, where does the "oxygen lack" theory come into place?
Now, does that prove that oxygen levels in the blood has nothing to do with yawning?
Dr Provine then came up with a suggestion that yawning is similar to stretching. Both increase the heart rate and the blood pressure as well as muscle and joint flexion. This relationship between yawns and stretches are substantiated with the evidence that if we try to prevent a yawn by clenching our jaws shut, the yawn seems to be "unsatisfying".
Mark Andrews said that studies have shown that yawning occurs when we just wake up, fatigued, or when our state of alertness is changing (is that why I yawned so much when I was tipsy yesterday?). But this is also not true. Low oxygen levels in the paraventricular nucleus (PVN) in the hypothalamus of our brain induces yawning. Yet, it is also known that PVN plays a role in penile erection (hur hur...), which is TYPICALLY not an event associated with boredom (hmm..isit? *quite doubtful* what caused the baby boom after WW2 in Asia?).
The PVN has indeed proved itself to be one of the "yawning" centers in the brain. Yawning is induced by the number of chemical messengers (dopamine, glycine, oxytocin, ACTH) in our brain. For example, ACTH is found to be at high levels before we sleep and wake up, causing us to yawn and stretch.
Despite the above theory which makes perfect sense, there are still numerous questions which linger.
So what's the conclusion? Yawning has got nothing to do with oxygen levels in the blood and the actual reason of this normal ability of human is still not proven despite the given suggestions making lots of sense..
Hmm..isn't this topic interesting? I'm amazed by it..
Why do humans yawn? Ever wondered about it?
Many would claim that they know the answer, and some egoistic people might say "Cos we lack of oxygen lah! Simple things like that also dunno..." Ok, just in case your self-esteem has been brought down to the negative levels, think Hmm...do these people know then? Are they right, proving that we're really that dense?
This was the first thing I decided to do, after washing up of cos (duh)...to find out the reason to why humans (even animals!) yawn.
Unfortunately, there's insufficient research being done on yawning, and no one really knows the real reason for it. However, suggestions have been made to why.
Wait wait..don't go "aiyah.....chey...."...cos I'm gonna tell you how you can "slap" those people who think they are some whiz kid as they try to bring you down with their "lack of oxygen" theory.
Apparently, their suggestion of the oxygen lack isn't totally invalid, BUT it is incorrect!!!! *Yay*
Perhaps it's wise to consider abt this "oxygen lack" theory first. It is assumed that our body makes yawning a way to rid excess carbon dioxide and to increase oxygen in our body. When people are bored or tired, they usually yawn, and that's because their breathing rate slows down. This results in lesser oxygen getting to the lungs, and as a result of the increase in carbon dioxide concentration in the blood, a signal is transmitted to the brain, triggering yawns to occur. Makes sense? Sure it does huh..
In 1987, Dr Robert Provine and his research team decided to carry out an experiment to test this theory. He did this by giving college students different concentrations of gases to inhale for 30 minutes, and calculated the number of times they yawn. For those who inhaled 100% oxygen or carbon dioxide of above normal concentrations, their breathing rate increased, but the number of yawns were indifferent from those who inhaled normal air.
They then went on with their research by having people to exercise. The breathing rate increased, but there was no change in the number of yawns before and after exercise!
Mark A. W. Andrews, the Associate Professor of Physiology and Director of the Independent Study Program at the Lake Erie College of Osteopathic Medicine, said that lungs do not necessarily sense oxygen levels. Fetuses yawn in utero although their lungs are not ventilated yet. If there is no ventilation, where does the "oxygen lack" theory come into place?
Now, does that prove that oxygen levels in the blood has nothing to do with yawning?
Dr Provine then came up with a suggestion that yawning is similar to stretching. Both increase the heart rate and the blood pressure as well as muscle and joint flexion. This relationship between yawns and stretches are substantiated with the evidence that if we try to prevent a yawn by clenching our jaws shut, the yawn seems to be "unsatisfying".
Mark Andrews said that studies have shown that yawning occurs when we just wake up, fatigued, or when our state of alertness is changing (is that why I yawned so much when I was tipsy yesterday?). But this is also not true. Low oxygen levels in the paraventricular nucleus (PVN) in the hypothalamus of our brain induces yawning. Yet, it is also known that PVN plays a role in penile erection (hur hur...), which is TYPICALLY not an event associated with boredom (hmm..isit? *quite doubtful* what caused the baby boom after WW2 in Asia?).
The PVN has indeed proved itself to be one of the "yawning" centers in the brain. Yawning is induced by the number of chemical messengers (dopamine, glycine, oxytocin, ACTH) in our brain. For example, ACTH is found to be at high levels before we sleep and wake up, causing us to yawn and stretch.
Despite the above theory which makes perfect sense, there are still numerous questions which linger.
So what's the conclusion? Yawning has got nothing to do with oxygen levels in the blood and the actual reason of this normal ability of human is still not proven despite the given suggestions making lots of sense..
Hmm..isn't this topic interesting? I'm amazed by it..
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