A. It is a common fact that people yawn when they are either a. suffering from fatigue, b. bored or c. when they see other people doing it, but it has never been proven that a yawn is caused by any of those three factors. A yawn is an involuntary respiratory reflex. The action of yawning is controlled by the spine and nerve cells and its use is to regulate the carbon dioxide and oxygen in your blood stream. Scientists belief that fatigue or boredom could trigger yawning because during these moments the amount of oxygen being taken is low and little is actually making its way into your lungs. A yawn is used to allow large amounts of oxygen to enter your body causing an increase of alertness, heart rate and amount of oxygen to the brain.
This is where things get confusing. If yawns are the bodies way of allowing more oxygen to enter than why do fetus's as young as 14 weeks yawn ? Scientist then suggest that yawning could be another way for a person to stretch. Like stretching, yawning causes an increase in heart rate, it flex's muscles and joints and increases your blood pressure.
So we can yawn for two different reasons all together because a. we need oxygen, or b. we're just stretching trying to wake ourselves up. Both theories make complete sense, we just need to figure out which one is the right one.
Dayna, interesting topic. It would have been nice to cite some sources.
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