Do you know what makes us yawn?

We know everyone yawns including animals also. But have you ever thought that why we yawn. Even sometimes thinking of yawning can cause you to do it. This is the most uncontrollable action that the body does isn’t. Yawning is not same for everyone. Most of us yawn when we go to bed or when we wake up. When we get bored then also we yawn or by seeing someone else yawning we yawn at times. Do you know in humans, yawning starts as early as 20 weeks after conception.
In our body, yawning is a coordinated movement of thoracic muscles in the chest, larynx in the throat and palate in the mouth. Yawning is a semi-voluntary action and partly reflex which is controlled by neurotransmitters of the brain. It is basically associated with neuropeptide proteins, neurotransmitters and some hormones.
Let us find out why do we yawn?
There are several theories about yawning, but first theory was given by Hippocrates, the father of medicine, told that it is a way to remove bad air from the lungs. It seems that yawning serves as a function of the respiratory system. But according to some other theories yawning causes an increase in blood pressure, heart rate, oxygen in the blood, which improves motor function and alertness. Also, tests have proved that the heart rate, sweating or brain electrical activity does not increase after yawning. That is why many athletes yawn before playing their respective sports.
Some researchers say that yawning might be connected to brain temperature. When the brain becomes warmer than the stable temperature, to make brain cooler we might yawn. Further, cooler blood from the body rushes or fills the brain and the warm blood comes out through the jugular vein.

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Source: www. jneuro.com
According to Dr. Andrew Gallup and Omar Tonsi Eldakar (2011) discovered that temperature might affect the yawning as well. If the outside temperature is warmer than normal, then the organism yawns less frequently.  
Yawning can be contagious also that is there are some sociological and evolutionary based biological explanation. Yawning is linked with the biological activity related to our 24 hour cycle, which gives a signal to go to bed or to wake up. Contagious yawning comes from witnessing someone or thinking about another person yawning. Around 42 to 55% human adults yawn during or after watching another person or video of repeatedly yawning.
We can also say that when we are bored or tired, we don’t breathe as deeply as we usually do. That is our body is taking less oxygen because of the slow rate of breathing. Therefore, yawning helps in bringing oxygen more into the blood and to move carbon dioxide out of the blood.
What happens to our body when we yawn?
When we yawn many body parts comes into action. First, mouth opens and jaws drops, allows taking in air as much as possible. When we inhale, the air fills in the lungs. Abdominal muscles flex and diaphragm is pushed down. Due to expansion of lungs, capacity of it increases and some of the air is blown back out.

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