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Why and How We Sneeze and Yawn

Sneezing: Here are some of the reasons we sneeze:

-Foreign object in the nose, including particles of pepper, smoke, irritating chemical fumes, or gases

-Withdrawal from opiate drugs

-Stepping outdoors into bright sunlight, which even has a scientific name: Autosomal Dominant Compelling Helio-Ophthalmic Outburst Syndrome

-Tweezing your eyebrows

-Combing your hair

-Rubbing the inner corner of your eye

-Eating too much


Yawning: A long-standing theory behind yawning is that yawning is caused by an excess of carbon dioxide and lack of oxygen in theblood. 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 thence to the bloodstream. It is almost certain however, that this hypothesis is not correct; a more recent theory is that yawning is used for regulation of body temperature. Another theory 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.

From- webperso.easyconnect.fn/.../polite-yawning.html