Yawwwwwn

[Biochemist]

Actually, I think all of the hypotheses are incorrect. The hoypxic driver is posssible, but unlikely. It is very difficult to establish a base for homeostatic status before a yawn, because one would have to take a measure at precisely the correct time, when there is no indication (yet) that a yawn is going to occur. Further, if we induce hypoxia, we rarely induce yawns.

It is certainly true that yawning equalizes the pressure with the middle ear via the eustachian tube, but for most folks, this is an intentional response, not an automatism. That why, for example, few folks yawn on descent in an airplane unless they are told to do so. Babies usually need assistance (like a bottle) to equalize ear pressure on a flight because they do not yawn.

Am I am certainly glad the combination of low external pressure and social contagion doesn't drive the fart reaction. Imagine final approach to the runway if THAT were true.

[orbsycli]

same joke, different context, same thread. biochemist i have to give you reputation for this attempt.

[TeleMad]

Originally Posted by Biochemist

Actually, I think all of the hypotheses are incorrect.

No you don't. You even admitted that what I said was correct. I said:

One reason we yawm is to equalize pressure. … The pressure in the tympanic cavity is not necessarily the same as the atmospheric pressure in the external auditory meatus. … The tympanic cavity has a tube, called the Eustachian tube, that runs down to the [nasopharynx] … When we yawn, air 'inflates' the tube and allows air to pass up into the tympanic cavity, equalizing its pressure with atmospheric pressure.

And you said:

Biochemist: It is certainly true that yawning equalizes the pressure with the middle ear via the eustachian tube...

I neither said nor implied that equalizing pressure between the tympanic cavity and external auditory meatus is the reason that yawning is contagious. I merely said that equalizing pressure is one reason we yawn, which is correct, as even you confirmed.