Why do we yawn?

Question

There is no scientific consensus on why we yawn. One theory argues that when humans are tired, we stop taking deep breaths, which causes a build-up of carbon dioxide in the body, said Douglas Parham, a speech scientist at Wichita State University. A yawn might be a special kind of respiration, Parham said. It builds up oxygen quickly, while expelling carbon dioxide, even more than a deep breath.
Excess carbon dioxide and other chemical changes, such as a drop in oxygen or increase in a compound called adenosine, could also act as "yawn gates," said lamae Cindann a neinathiniet and natineriantiat atExcess carbon dioxide and other chemical changes, such as a drop in oxygen or increase in a compound called adenosine, could also act as "yawn gates," said James Giordano, a neuroethicist and neuroscientist at Georgetown University. These chemicals send out a signal that triggers a yawn. By yawning, we compress the muscles of the face, driving oxygen-enriched blood to the brain, Giordano said.
Other proposals state the purpose of yawning is to cool the brain, or to stretch internal organs like tissues and lungs, helping the body to liven up.Use the passage from "Why are yawns contagious? We asked a scientist." to answer the question.Cause: to quickly expel carbon dioxide
Cause: to drive oxygen-enriched blood to the brain
Cause: to stretch internal organs
Cause: ?
Cause: ?• to increase adenosine levelsto cool the brainto increase the frequency of deep breaths• to compress facial musclesto increase the frequency of deep breaths to build up oxygen

Answer 1

Based on the passage, additional causes of yawning could include:

1. To increase adenosine levels - There is a suggestion that adenosine may play a role in the signaling of yawning.
2. To cool the brain - Yawning may help regulate brain temperature.
3. To increase the frequency of deep breaths - Yawning may serve to promote deeper breathing.

To summarize, the causes for yawning specified in the passage are:

• To quickly expel carbon dioxide
• To drive oxygen-enriched blood to the brain
• To stretch internal organs
• To increase adenosine levels
• To cool the brain
• To increase the frequency of deep breaths

Overall, yawning may serve multiple physiological and neurological purposes.