Why Do We Yawn
THE TRUTH IS that we don't completely understand why people, or
animals for that matter, yawn.

It's widely assumed that yawning occurs because we are tired or
bored or because we see someone else doing it, but there isn't any
hard 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.

Now... try to make yourself yawn!