What causes it...

We do it when we are tired, we do it when we wake fully rested, we do it all times during the day... in fact all vertebrae animals yawn... the act is called Oscitation.

Humans start yawning even before child birth around the second trimester. Now how is that possible if yawning is just because we have a lack of oxygen and our bodies gulp for air... that a fetus also yawns.

The Science

It is now widely believed that yawning cools the brain... as it can actually overheat (per say). Yawning also increases heart rate,blood flow and works muscles in your face which all act to cool the brain. It also cools the blood going to the brain for extra temperature lowering capacity.

But why do our brains overheat? The two main reasons are exhaustion and sleep deprivation.

Well the brain use 40% of your metabolic energy and because of this heating of the brain occurs. Brain temperatures also rise (as does body temperature) with it's Circadian Rhythm.

The brain cools to allow more and greater processing as well. But how does this actually happen, how does a yawn cool the brain?

Cooling Aparatus

The brain is cooled during the yawn in stages. First the act of opening the jaw allows greater blood flow into the brain.

The air gulp is also transferred into your upper nasal and oral cavities that cool the mucous and blood vessels in these regions, that project into our fore-brain.

The fore-brain is the region responsible for sensory input, processing, language and motor function.

The cooling makes you more alert and functioning at higher levels.

Contagion

When we see someone yawning, we have the tendency to yawn in response.

The belief is that when we see another person yawning, our brains interpret this as a lack of available oxygen and we yawn for more. Maybe it is our empathy for others that creates this desire and reflex.

Children start contagious yawning at about age 4-5 just when their empathetic tendencies begin to develop. It has also been documented that Autistic children have less tendency toward contagious yawning.

We also have a greater tendency to yawn when seeing someone from closer social ties or genetics than strangers.

Another factor in contagious yawning is in "Mirror Neurons". These Neurons fire when we have an action, see someone enact an action or even think about that action. They are typically used for learning, relating and even self-awareness... so when we see a person or even animal yawn, we have the tendency to copy the action.

Did you just Yawn?

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Good Health – Evan Pantazi #Kyusho

Image Credit: natgeo, gettyimages, thetimes.co.uk, pinimg