Adam Dickson age 10  of Birmingham Ala for his question

WHAT CAUSES YAWNING?

Yawning is the act of opening the mouth wide or gaping The usual yawn is caused by drowsiness or fatigue It is most of the time a sign that the body needs sleep

Yawning is an involuntary reflex After the act has started it is almost impossible to stop it The person can hold his mouth closed but the yawning muscles still contract

You yawn when oxygen is slowly cut off and when the muscles are thoroughly relaxed If you yawn often it is probably a sign that you are not getting enough oxygen You may need better ventilation or exercise You will generally stop yawning if you drink a beverage or if you bathe your face with cool water

Scientists aren t sure what part of the nervous system controls yawning but it may be the mesencephalon or midbrain in the brain

One purpose of yawning may be to awaken a person by stretching the muscles and helping the blood circulate