Yawning is the act of producing a yawn, which is an
involuntary opening of the mouth, usually accompanied
by a movement to take a deep breath. The average
yawn lasts about 6 seconds. Yawning sometimes
occurs when people become bored, tired depressed, or
sleepy. Yawning does not always mean that one is
tired, but people who are tired do tend to yawn.
Yawning can also occur when vital signs decline, such
as after a large amount of blood is lost. Vital signs are
measurements of blood flow, body temperature, and
breathing, all functions that are essential (vital) for life
to continue.

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Yawning is thought by some to be a partly automatic response produced by the brainstem
in reaction to lower levels of oxygen in the brain. The brainstem is an area in the lower
part of the brain that connects it with the spinal cord. This area of the brain controls many
functions crucial for life to continue. Yawning can also be caused when the lungs do not
get enough oxygen. Seeing other people yawn tends to increase the chance that one will
yawn. In fact 55% of people will yawn within five minutes of seeing someone else yawn.
Even reading about yawning can make you yawn! Some people yawn very frequently, a
condition known as excessive yawning.Yawning comes from the Middle English word
"yanen" meaning "to gape" (open the mouth wide).

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