"We now have evidence that brain ACE2 plays a critical role in baroreceptor reflex function and, consequently, in the prevention of hypertension," says Dr. Xia.

It was long believed you yawned when there was too much carbon dioxide and not enough oxygen in your blood. A part of your brain called the brain stem detected this and triggered the yawn reflex.

This is because the brain monitors the amount of carbon dioxide in the blood to decide when to trigger the gasp reflex.