"::darkshadows::" <blood@thirsty.net> wrote in
news:btb434h2b7cfi6n7t65daiumfd03hocr0i@4ax.com:
>
>
> Why do we yawn?
>
>
> animals for that matter, yawn.
>
> evidence to support these beliefs.
>
> Scientists do not purport to know all of the biological mechanisms of
> the yawn, but tend to agree that a yawn is an involuntary respiratory
> reflex, which regulates the carbon dioxide and oxygen levels in the
> blood.
>
> Technically, a yawn is the reflex opening of the mouth followed by the
> deep inhalation and slow exhalation of oxygen.
>
> The very act of yawning is but one of a number of involuntary reflexes
> controlled by the spinal and nerve centers.
>
> Scientists speculate that the onset of a yawn is triggered either by
> fatigue, or by sheer boredom as, at those times, breathing is shallow,
> and little oxygen is carried to the lungs by the oxygen-toting
> cardiovascular system.
>
> When one yawns, his or her alertness is heightened, as the sudden
> intake of oxygen increases the heart rate, rids the lungs and the
> bloodstream of the carbon dioxide buildup, and forces oxygen through
> blood vessels in the brain, while restoring normal breathing and
> ventilating the lungs.
>
> This quite plausible theory of yawning falls short of explaining many
> aspects of yawning. Scientists explain away the "contagious" nature of
> yawning, that is when one person's yawn triggers another nearby to
> yawn, as due to the power of suggestion, but are at a loss when
> attempting to explain why yawning occurs excessively in patients with
> lower brainstem damage or with multiple sclerosis.
>
> Other unlocked mysteries include why fetuses in the womb yawn, when it
> is a well-known fact that they do not intake oxygen into their lungs
> until after live birth, or why individuals with high concentrations of
> oxygen in their blood streams yawn.
>
> Until these questions are answered, do not assume that a person who
> yawns in your presence is bored with what you are saying, or suffers
> from exhaustion. Simply be pleased that he or she is not bored to
> death.
>
>
Let him yawn in peace, is nothing sacred LOL.
Mercury.
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