Why do we yawn? | Diseases and conditions.

Yawning is an involuntary act we do almost every day, even our pets yawn, but... What do the yawns are? Why are they so annoyingly contagious? Discover it.
Yawning is a habitual and daily Act. We we yawn or see yawning someone first thing in the morning, at the meeting of the afternoon, etc.
So do our pets (dogs, cats and reptiles inlcluding!). However, despite the routine of this phenomenon, we yawn or which functions have in our body is unknown.

What is yawning?

It is an involuntary act that we cannot control by which widely open mouth, making a deep inspiration, followed by a light blow, that caba almost with a sigh. Yawning appears when we are deeply bored or tired, and is accompanied by movements of the upper part of the body to have more chest expansion.

Why is it contagious?

The reason is unknown, but it does not occur only in the human species, but also in a wide variety of animals. It is curious that only in humans and apes is contagious yawning, something that seems to be due to both share a social complexity more developed than the rest of the animals.

Why we we yawn?

There are a variety of theories, although none by itself contributes to give a complete answer.
The more defended today are:

Lack of oxygenation

In situations of tiredness, boredom, etc., we breathe less intensely than normal, causing one lower oxygen exchange or an excess of carbon dioxide in the body, thus, yawning to take a deep breath and compensate for the lack of oxygen.
This hypothesis has a failure: studies showed that approximately a 12-week fetus yawned, but these do not breathe by lungs until they are born. The way to get oxygen and expel carbon dioxide occurs through the umbilical cord.

Sign of anxiety

Some experts think that yawning acts as a kind of mechanism that modulates the sense of anxiety. As an example which has been observed an increase in the number of yawns in politicians or professionals of oratory that waited his turn to speak, athletes before important competitions, or in patients while waiting for their turn in the waiting room.

Evolution

In this case, yawning have evolutionary origins, used to synchronize the body in different situations such as: upon waking, sleeping, able danger, etc. After a yawn, increases blood pressure and heart rate more than 25%, keeping the body in a State of alert.

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