Question

Why do you think we yawn when we are sleepy or drowsy?

Answer 1

It is actually the brain cells which are in a sense of saying..going to fall asleep for lack of oxygen. Also when we feel drowsy, our respiratory rate being controlled by reflex centres in our brain falls. This is a vicious cycle. The yawn breaks this cycle.

Answer 2

Answer : When we are sleepy or drowsy we yawn because our brain lacks sufficient amount of oxygen . Thanks deep breath associated with yawning help us to drawnin more oxygen and supply the much needed oxygen to the tired body organs including the brain