Although yawning is usually associated with sleepiness and relaxation, it can actually indicate sexual arousal or hunger. Another theory of yawning is that it's the body's way to take in more oxygen to dispense with excess carbon dioxide. Yawning is also strangely contagious and can be shared amongst groups of people.Continue Reading
The body goes fully into action when people yawn. The mouth opens and the jaw drops, allowing the lungs to fill with air. The heart rate goes up by as much as 30 percent during a yawn. Abdominal muscles clench and the diaphragm is forced down. Lungs expand to capacity before blowing some of the air back out of the body.
Yawning is something usually shared between social groups of humans, but it is also contagious to chimps and dogs. Humans begin yawning as early as infancy. Some studies report that groups that have difficulty with social interaction, such as autistic individuals, do not find yawning contagious.
Yawning is also associated with a change of state. In many cases it is an instinctual, anxious action. It is often caused by a release of dopamine into the brain, thus triggering a chain effect of a release of many other brain chemicals.Learn more about Human Anatomy