What cause yawning contained by humans?

What cause yawning contained by humans?
is a reflex of deep inhalation and exhalation associated near being tired, next to a need to sleep, or from deficiency of stimulation. Pandiculation is the term for the achievement of stretching and yawning. Yawning is a powerful non-verbal message with several possible meaning, depending on the circumstances. It is also claimed to help increase the state of alertness of a human being. It could possibly be from lack of oxygen. Another speculated judgment for yawning is nervousness - paratroopers be once noted yawning right before their first get, and had newly come from a coffee break. The exact causes of yawning are still unascertained.
when the brain tell u it needs more oxygen
This is cause by your body's desire for fresh oxygen. They say self sleepy has nil to do with it.
Yawning occur in almost adjectives mammals - cats, dogs, lions and even seals yawn. It is triggered by the lowering of the height of oxygen in the blood which within turn stimulates the diaphragm - a thin flat muscle within the lower chest to contract and make the animal suck surrounded by a large amount of nouns inwards to the lungs thereby replenishing the oxygen in the system.
paucity of oxygen in your body
I meditate it must be mainly due to sloth, relaxation and sleepiness
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