is it due 2 lack of oxygen, that we yawn?
473733
lack of oxygen in your brain\n\nyes\n\nand you do it when your tired bc your body is like i want to sleep bc when you sleep you get more oxygen\ni think\n\nand when you yawn you breathe in a lot of oxygen\n\nand without oxygen you feel tired\n\nso yeah
307772
Just a guess...  When you yawn, you take in more air than normal.  This means you get more oxygen than normal.  In a situation where it might be important to get more oxygen than your normal breathing urge will provide, an animal that yawns will have an advantage over one that doesn't yawn.  Since there is no disadvantage to yawning and occassionally there is an advantage, a mutation that causes an animal to yawn in response to another yawn would be passed on.
261027
Why is this the second most asked question on here?  If the guys would stop asking about the size of their "manhood", this would be number one!\n\nWhy we yawn when we see others yawning has baffled scientists for ages and a number of suggestions have been put forward to explain this phenomenon. What we do know is that yawning is an involuntary action- our brain does it without us thinking about it, even very young babies yawn showing that it's a built in action (Chimps do it too by the way). Just thinking about yawning can trigger the bit of the brain that causes a yawn. http://www.ratlab.co.uk/yawn.htm...\n\nMore theories can be found at the links below: \n\nhttp://www.world-science.net/exclusives/...\nhttp://www.yesmag.bc.ca/questions/yawn.h...
294378
yah, scientific studies show that it is,\n\nhttp://www.world-science.net/exclusives/050309_yawnfrm.htm
632459
Causes of yawning\n1.An indication of tiredness, stress, over-work or boredom. \n2.An action indicating psychological decompression after a state of high alert. \n3.A means of expressing powerful emotions like anger, rejection or apathy. \n4.A sign that one is not breathing deeply, and not receiving enough oxygen through the body. \nA yawn can express strong anti-social messages, and so in some cultures people try to mute or mask them by placing a concealing hand over the yawning mouth.\n\nA 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. One study documented that this effect does not exist ("Yawning" by Robert R. Provine, pages 532-539, American Scientist, November-December 2005, Vol 93, No. 6). 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.\n\nAnother theory is that yawning is similar to stretching. Yawning, like stretching, increases blood pressure and heart rate while also flexing many muscles and joints. Some have observed that if you try to stifle or prevent a yawn by clenching your jaws shut, the yawn is unsatisfying. As such, the stretching of jaw and face muscles seems to be necessary for a good yawn.\n\nThe yawn reflex is often described as contagious: if one person yawns, this will cause another person to "sympathetically" yawn.[2] The reasons for this are unclear; however, recent research suggests that yawning might be a herd instinct.[3] Other theories suggest that the yawn serves to synchronize mood behavior among gregarious animals, similar to the howling of the wolf pack during a full moon. It signals tiredness to other members of the group in order to synchronize sleeping patterns and periods of activity. It can serve as a warning in displaying large, canine teeth, thus proclaiming, "don't attack while I am sleeping..." The contagion of yawning is interspecific (i.e., try yawning in front of your dog). Yawning in public is generally regarded as impolite in the West, but came into fashion in polite French society for a brief period in the late 18th century. Oddly, sometimes sympathetic yawning may be caused by simply looking at a picture of a person or animal yawning, or even seeing the word "yawn".\n\nAdelie Penguins employ yawning as part of their courtship ritual. Penguin couples face off and the males engage in what is described as an "ecstatic display," their beaks open wide and their faces pointed skyward.
41848
I have a theory on this to share.\nMay be yawning is not a chain reaction at all.\nIts just our reaction to the state of things, outside as well as inside our body.\nFor instance, we feel sleepy when our brains are tired or refuse to process. Result is that we all yawn when after a tired game, after a boring speech.\nMay be even when there is lack of sufficient oxygen.\nWe all have different reaction times though. Thats probably the reason why its being mistaken to be a chain reaction.
196592
It is the brain requiring more oxygen. Which is why when someone else yawns you do to, it is your brain making sure that it has enough in case the other person takes it all. Not very likely to happen unless in a confined space, but the brain is always on survival mode.
763987
It sounds like your not drinking enough water. I could be wrong but, usually when you are falling asleep like that, it is lack of oxygen in your blood stream. Your VO2 max has mostly to do with oxygen getting to the muscles while you workout. No, your VO2 max has nothing to do with this. How much are you sleeping? If you ride alot, you need at least 7-8 hours of rest a night.
56870
The dictionary tells us that yawning is caused by being fatigued, drowsy or bored, scientists are discovering that there is more to yawning than what most people think. Not much is known about why we yawn or if it serves any useful function, and very little research has been done on the subject. However, there are several theories about why we yawn.\nThe Physiological Theory -- Our bodies induce yawning to drawn in more oxygen or remove a build-up of carbon dioxide. This theory helps explain why we yawn in groups. Larger groups produce more carbon dioxide, which means our bodies would act to draw in more oxygen and get rid of the excess carbon dioxide. However, if our bodies make us yawn to drawn in needed oxygen, wouldn't we yawn during exercise? Robert Provine, a psychologist at the University of Maryland, Baltimore County, and a leading expert on yawning, has tested this theory. Giving people additional oxygen didn't decrease yawning and decreasing the amount of carbon dioxide in a subject's environment also didn't prevent yawning. \nThe Evolution Theory -- Some think that yawning is something that began with our ancestors, who used yawning to show their teeth and intimidate others. An offshoot of this theory is the idea that yawning developed from early man as a signal for us to change activities. \nThe Boredom Theory -- In the dictionary, yawning is said to be caused by boredom, fatigue or drowsiness. Although we do tend to yawn when bored or tired.
64755
Personally, I think it's a sub-conscience action since you don't have to be aware of someone else yawning. Think of it this way, you weren't hungry until you saw, smelled, or someone mentioned food. So as you idle your body equates lack of action as rest. As we all know, rest is equated to sleep, so your idle body wasn't tired until someone yawned. \n\nI know it sounds odd but, have you ever yawned while your cardio system was working harder than compared to sitting idle?
853561
lack of oxygen in the brain. it's a signal that you're mind and body are tired and you need to sleep to recharge.
792582
A yawn is in response to too much CO2 in the blood stream.  When you yawn there is a negative feed back loop in operation which tells the diaphram to contract (take a breath) because there is too much CO2......the yawn actually increases CO2.\nThe sneeze is due to irritation in the beginning of the respiratory tract, it expells such things as dust, bacteria and other irritants from your nose and sinuses.\nA hiccup is a sligh malfunction or mistiming if you will of the glottis which is a membrane that closes in your throat to prevent food from going into your lungs when you swallow.  Whenyou ge tthe hiccups it starts to close while you are taking a breath or expelling a breath.  It just takes a bit of time for your body to reset when it closes
305821
You yawn because there's not enough oxygen in the air and your body just does that to get more oxygen in one breath. So tecnicly everybody's not getting enough oxygen.
567755
Yes!  I've heard that's either because I'm deprived of vitamins and water, or that I have sleep apnea.  Who knows you could have the same problems, why don't you go to a sleep clinic?
1095614
Yawning then taking another 5 min. sleep
1051186
When a person yawns it is usually due to the lack of oxygen to the brain. When we see a person yawning our brain interprets  it as low level of oxygen in the air.As a result we yawn.
1071961
yawing does not mean one is tired in reality it means the brain is receiving a huge amount of oxygen which is good and when one yawns it emits a type of pheromone that gets emitted thus in a car one person yawns the others will follow