Yawning wakes up our brain. In order for the brain to remain vigilant, it needs oxygen which we get in plenty when we breathe in air. Oxygen travels to our entire body with the help of blood. After a busy and hard day, the heart pumps blood more slowly than usual. However, tired brains need more oxygen. With yawning, you pull in the air and with it, oxygen, which in turn refreshes the brain.
Why do we yawn when we are tired?
