Question

I wants to know why we yawn when we are sleepy or drowsy

Answer 1

During Yawning which is also called oscilation, we take a deep breathe of air. Hence, a theory suggested that it helps our body to bring more oxygen and give out carbon dioxide. However it is incorrect.

Our brain works best at certain temperature.But When we perform various activities throughout the day, our brain gets exhausted and sleep deprived. Both exhaustion and sleep deprivation increase our brain's temperature. Hence, to cool it down, we yawn.