Why do people yawn when they feel sleepy?

Question

If we feel sleepy, we could just go to bed, but why do we yawn? I noticed that when somebody besides me yawn, i will yawn after a few second. Isn't that weird? I also found out that animals yawn too.

Answer 1

Yawning is your body's attempt to get more oxygen. When you are tired, your breathing tends to get more shallow, and your body tries to compensate by making you yawn - bringing in more oxygen.

Here's some more information on yawning, and why it's "contagious".

Answer 2

Most vertebrate animals exhibit yawning. A yawn consists of widely opening the mouth with a slow inspiration at the beginning and a quick expiration at the end. Yawning is a reflex behavior that can be only partially controlled by our own volition. The behavior occurs most often when we feel sleepy, bored, and, perhaps, physically fatigued. Yawning can also be triggered by drugs and has been used as a medical index because there are changes in the frequency of yawning in certain disease states. Scientists have not identified a function of yawning, but, at least in humans, it does seem to be contagious since observers are more likely to yawn when they watch someone else yawn. In this sense, yawning is a type of social behavior that is largely involuntary and controlled by the brain.

Answer 3

Actually, poeple don't yawn only when they're sleepy. Yawning is produced by the respiratory centres in our bulb. When the concentration of oxygen in our blood becomes too low, or the concentration of carbon dioxide becomes too high, our respiratory centres take notice of that and deliver an impulse to our respiratory muscles so that we intake oxygen therefore yawn.

Answer 4

Yawning is a response to the bodies need for Oxygen, and when you are tired, you tend to breath more shallowly, and you yawn to compensate. Yawning does seem to be contagious, and you are right, I used to get a kick out of pretending to yawn to make my dog yawn.

Answer 5

I started yawning reading your question ... even a suggestion of yawning can make people yawn. I don't know why ... but I do know the reason we yawn is because we have a lack of oxygen in our avioli (?sp) sacks in our lungs. These are the sacks that exchange the gasses our resp. system needs. When we are tired we tend to breathe shallow, therefore our lower sacks don't fill ... hence YAWN

Answer 6

1. An indication of tiredness, stress, over-work, or boredom.
2. An action indicating psychological decompression after a state of high alert.
3. A means of expressing powerful emotions like anger, rejection, apathy, or tedium.A 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.
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. 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). [1]. 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. Another theory is that yawning is similar to stretching. Yawning, like stretching, increases blood pressure and heart rate while also flexing many muscles and joints. It is also theorized that yawning helps redistribute an oil-like substance which coats the lungs and aids breathing. 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.
The 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. This phenomenon has been observed among various primates. The threat gesture is a way of maintaining order in the primates' social structure. 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".

Adelie 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. This trait has also been seen among Emperor Penguins. Researchers have been attempting to discover why these two different species share this trait, despite not sharing a habitat.

Answer 7

You don't always yawn when you are sleepy, usually it is when you are tired but sometimes you yawn when you aren't tired. You yawn to get more air into your lungs, usually to get more energy. When you are tired, your muscles start to relax so you don't get in as much air so you yawn to breathe in more air. As for yawns being contagious, yes they are but I'm not really sure why.

Answer 8

when we yawn our body needs more oxygen. That is whay we open our mouth wide and take in a lot of oxygen. When someone beside u yawns, he/ she takes in a lot of oxygen from near you so in order to compensate for your loss u also yawn

Answer 9

I saw on myth busters that we don't really know why we yawn... Otherwise, monkey see monkey do. =P

Personally, I think it's some times just our bodies running low on oxygen and it's one of those unconscious acts we do. Also I yawn when I'm nervous, so for me it's usually just a nervous reaction because.. well, it's like when you sometimes don't know what to do with your hands, so you do what you can.. cross em, shove em in your pockets, etc.

Answer 10

yawning is brain's simple way of saying that ur exhausted and need more oxygen. so u go to sleep either to revive urself or keep on taking in more oxygen by yawning.