What Causes Yawning?

Answer

The major causes of yawning include an increase in the carbon dioxide levels in the blood, therefore the need for an influx of oxygen, the desire to stretch muscles, and controlling of the brain temperature. The act is usually reflex and is accompanied by an inhalation and exhalation of breath.
Q&A Related to "What Causes Yawning"
Humans and animals alike yawn. Everyone does it, but scientists can't agree on what causes yawning, or why we yawn. There are several theories, but no proof that any of the theories
http://www.ehow.com/how-does_4923296_what-causes-y...
Reasons: 1) Where, there is a discussion/lecture/conversation going on which you don't like and you don't have any interest in that. 2) An intimation to you where sleep is on head
http://wiki.answers.com/Q/What_causes_us_to_yawn
Yawning is an involuntary action that causes us to open our mouths wide and breathe in
http://www.chacha.com/question/what-causes-yawns
I hadn't heard of that side effect, so this question piqued my interest. The only relevant paper I found on PubMed was this case report: McLean JD, Forsythe RG, Kapkin IA: Unusual
http://www.quora.com/Why-does-Clomipramine-(Anafra...
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Popping in the ear is caused by the pressure changes inside and outside of the eardrum. It is stopped by swallowing and yawning which relieves the pressure in ...
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