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YT2095

Tears of Tiredness

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this is a question posed by my wife the other night, one I could not give an informed answer to.

 

Why is it, that when you`re really tired and you Yawn, you get tears in your eyes?

 

 

I made a thread a while ago: http://www.scienceforums.net/forums/showthread.php?t=5530

 

about the contagious factor of Yawning, and was hoping for a better input with regards to it`s possible social implications on an evolutionary scale.

 

but tears??? I`m guessing it`s an "Auto-Clean" routine that happens while we sleep, aided by REM sleep?

that`s the best answer I could give / Guess at.

 

I/We would be gratefull for any True / Informed answer :)

 

Cheerz :)

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Presumably, the mucus membranes around our eyes gradually evaporate off their moisture content on exposure to air. Tiredness could affect your ability to replenish them at the same rate, leading to periods of dryness followed by periods of squishiness.

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but why should it occur during a yawn? and a yawn when ONLY when very tired?

(it doesn`t happen during day yawns, and when you`re dead tired and Don`t yawn).

 

<we`ve kept logs / notes>

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Perhaps because the mucous membrane is contorted by the muscles that close the lids of your eyes, and that squeezes out every last drop.

 

Exactly why that doesn't happen during a 'day yawn' is more of a poser :confused:

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well I went into a diatribe of catabolic and anabolic states, reasonably certain that my lessons about these applied also.

 

Catabolc (during sleep) are when our "Healing procs" are most active (hence you wake up with Zits as an adolescent).

and so it would seem logical that the tears would be there to clean your eyes as you aproach this state.

 

it was only a semi-educated guess :)

 

 

I`m sure Glider will know 100% for sure though, either way.

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LOL, he`s not gunna get here `till he`s had his cataBolics :)

 

oh dear, 37 years of age, and I STILL have to smile when I type that or say it!

 

Sooooo Saaaaaaddddd......

 

anyway, on a serios note, does that sound TOO far off the mark as a logical guess (post #5) ?

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Not sure. I don't really know that much detail about the mucous membranes.

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I hadnt noticed until i read your message, made myself a drink and started to yawn. My best projection is that as the face contorts certain hormones (i think im not really a biologist) are released through ther eyes. When you think about it it must be a pretty traumatic thing to do a yawn, try and make the facial expressions and you'll understand

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but why should it occur during a yawn? and a yawn when ONLY when very tired?

(it doesn`t happen during day yawns' date=' and when you`re dead tired and Don`t yawn).

[/quote']

 

not just when very tired, but when in the range of tired to very tired and resting as though you are going to sleep, but refusing to actually go to sleep. well, for me anyway.

 

i've teared a lot because of that during school, and a few times it's been during a movie that some might consider "sad"... you can guess the reactions when someone noticed my tears >_>

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Basically, yawning squeezes the ol' lacrimal glands. During the day, the tears evaporate and also drain away into the lacrimal canals and into the nasal cavities. However, there are two differences when you are tired and approaching rest:

1, you yawn a lot more frequently, so more tears are produced

2, your eyes are less open (less evaporation), you're also often a bit more congested in the face due to sitting or laying down or being a bit puffy faced through fatigue etc.. This constricts the lacrimal canals so the tears can't drain away effectively.

 

Also, when you're in a resting state, the parasympathetic system inhibits tear production so pre and post rest, you produce a bit more (the yawning helps here); pre rest, to prepare for the night, sort of build up a protective film under your eyelids. Post rest, to clear away 'sleep' from your eyes and relube them.

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