fact of the day 11-15-05

[urso8up]

The technical reason for why we yawn is because we need extra oxygen.

[BBAddict]

So why don't we yawn during exercise? I know we yawn because of excessive carbon dioxide in our lungs causing us to get insufficient O2, so shouldn't we yawn when we're not getting enough O2 during exercise??

[shortz]

*yawn* This thread is boring.

[Stonecold54]

I believe yawning is a feedback mechanism from the brain not from lack of oxygen but of a too high concentration of CO2 in the bloodstream... its almost on the same lines and part of me still wonders why that is only when I am bored, lol.

[Lmg2701]

Actually that isn't a fact. The fact is that there are only a bunch of theories and none of them have been proven. Like I said though, this is one of the many theories.

[Scrumhalf]

From Wikipedia:

A long-standing hypothesis is that yawning is caused by an excess of carbon dioxide and lack of oxygen in the blood. The brain stem detects this and triggers the yawn reflex. The mouth stretches wide and the lungs inhale deeply, bringing oxygen into the lungs and hence to the bloodstream. It is almost certain however, that this hypothesis is not correct; a more recent hypothesis is that yawning is used for regulation of body temperature. Another hypothesis is that yawns are caused by the same chemicals (neurotransmitters) in the brain that affect emotions, mood, appetite and other phenomena. These chemicals include serotonin, dopamine, glutamic acid and nitric oxide. As more of these compounds are activated in the brain, the frequency of yawning increases. Conversely, a greater presence in the brain of opiate neurotransmitters such as endorphins, reduces the frequency of yawning. Patients taking the serotonin reuptake inhibitor Paxil (Paroxetine HCl) have been observed yawning abnormally often.

http://en.wikipedia.org/wiki/Yawning

[Lmg2701]

Originally Posted by Scrumhalf

From Wikipedia:

A long-standing hypothesis is that yawning is caused by an excess of carbon dioxide and lack of oxygen in the blood.

http://en.wikipedia.org/wiki/Yawning

RE:Why do people yawn?

Message:

This is a very interesting question, but I'm afraid that the answer as to why we yawn is still quite a mystery to science. Actually, there are several aspects of human/vertebrate behavior that remain quite mysterious - such as yawning, shedding tears while crying, sleeping, etc. Scientists have simply failed to provide satisfying reasons for these behaviors to exist - though there are of course many theories - all unproven.

So let us consider yawning. When do we yawn? Generally when it is very late and we are tired, but also in the morning when we get up. We also have other associated behaviors - such as stretching, having "heavy" eyelids, etc. So why do we do these things? I will offer several popular theories and then present evidence that suggests that each of these ideas is probably false. Then I will present my own theory and propose several simple experiments to test these ideas.

The standard theories.

1. Yawning is induced by hypoxia (low oxygen levels in the blood stream).

The idea behind this (the most popular) theory is that yawning causes you to take a deep breath when you need some extra oxygen - perhaps because you are tired are have not been breathing enough. These are MANY problems with this idea, but the main problem is that yawning occurs only when you are tired and does not occur in the many other instances of hypoxia. For example, if you exercise hard you need more oxygen - but your body makes you breath harder, not yawn! If you are brought from, say, sea-level to an elevation of 20,000 feet within a time period of 5 min, you will immediately faint due to severe hypoxia, but you will not yawn.

2. Yawning is a method for communicating to other individuals your physiological state of being tired.

This idea is that several human behaviors are for communication purposes. Thus, smiling is to let people know that you're happy, crying is to tell people that you are very sad (and possibly need help), the facial expressions of anger and to let people know that you are mad, and yawning is simply to let people know that you're tired. The problem with this idea is that nearly all vertebrates yawn, including fish, alligators, turtles, etc. Yet it is hard to believe that your goldfish is trying to communicate its feelings or tiredness! These lower vertebrates don't show any other "feeling" communication behaviors (such as smiling, purring, crying, etc.) Thus it does not seem likely that they yawn as a communication device. This does not mean that humans don't use yawning to communicate feelings, but yawning certainly didn't originate for this reason.

3. Yawning is used to stretch out the lungs to prepare them for use.

Perhaps the lungs need a little stretching every once in a while to get out the wrinkles, etc. This would explain why yawning is often associated with stretching other muscles (like the arms, etc.) So all you are doing is preparing the body for a hard day of work. However, this would not explain why you yawn when you get tired before bed - because sleeping definitely does not qualify as a "hard day of work." You don't need to prepare you lungs for sleep since sleep requires much less oxygen than being awake.

Now I will do my best to provide a possible rational explanation/theory for human yawning. That me first suggest that there are actually two different types of yawning - let's call them type I and type II. These are defined as yawning associated with skeletal muscle stretching (type II), or yawning by itself (type I). My proposition is that type I yawning ONLY occurs at night before you go to bed, and that type II yawning ONLY occurs in the morning as you are waking up. Thus, type II yawning is explained by theory #3 - that you are stretching your lungs to prepare them for a day of breathing. Type I yawning is explained by theory #2 - that you are communicating the fact that you're tired to other people. So my theory is actually a combination of theories #2 and #3.

My idea would be that Type II yawning is the only form of yawning used by lower vertebrates and even most mammals, like cats for example. Cats very often yawn and stretch when waking up in the morning, but you will rarely see a cat yawn when it is tired in the evening - so they only have type II yawning. The idea would be that we evolved from a mammal that, like the cat, only had type II yawning. However, for very social animals like our ancestors, evolution selected for a way to communicate being tired. Basically, yawning was adopted for this purpose - and hence type I yawning evolved. This might have been useful for many purposes, such as synchronizing the sleeping schedules of a group of social animals that lived together. This would be the reason yawning seems contagious. When you see someone yawn, your brain makes you become more tired yourself, and so you start yawning as well. This helps everyone go to sleep at about the same time.

So - in science when you propose a theory or idea, you should also propose experiments that might be done to test your ideas. For example, my idea proposes that in the evening (when type I occurs) yawning is for communication or display purposes only - i.e. there is no reason to take a huge deep breath to stretch the lungs out. Thus, a prediction might be that someone would take much larger breaths while yawning in the morning than in the evening - and this could easily be tested. It should also be tested that animals like cats and alligators definitely don't have type I yawning since I'm only going by my own anecdotal observations - this needs to be tested more carefully in a controlled study. Another prediction is that only type I (but not type II) yawning is contagious - also easily testable. I'm sure you could think of lots of other tests to either support or refute this theory. In fact, I REALLY encourage you to try to carry out some of these experiments yourself!!! I'm not aware of anyone doing these very simple experiments - so you would be making new discoveries!

[Scrumhalf]

The wikipedia snippet that I posted did indicate that the hypoxia theory is almost certainly not true.

[njjuicer]

did u make that shit up yourself or did u get it form sumwhere? thats pretty invloved post if u did it yourself either way makes u think b/c persoanlly i enver gave a shit why ppl yawn lol and guess what i yawned alot reading this lol interesting eitherway

[njjuicer]

hey urso so much for ur "fact" of the day LOL







better luck tomorrow bro :p

[Timma]

Originally Posted by BBAddict

So why don't we yawn during exercise? I know we yawn because of excessive carbon dioxide in our lungs causing us to get insufficient O2, so shouldn't we yawn when we're not getting enough O2 during exercise??

Maybe it's me but I yawn all the time when I workout.