🚀 go-pugleaf

In article <579@tekfdi.UUCP>, mikeb@tekfdi.UUCP (Mike Boyce) writes:
> As a side issue: What causes the euphoria induced by aerobic exercise. 

Your friend and mine, endorphins.  These are produced and released in
the brain in response to low level pain, and have an opiate effect.
This is what is responsible for "runner's high" as well as many other 
forms of exercise-induced euphoria.  In some cases the increased flow
of oxygen to the brain can also give you a feeling of exhiliration,
particularly after a hard day in front of the terminal, but his doesn't
last and isn't the same as the endorphin high.

Here's *my* side issue:  I was recently asked why you yawn when you are
tired.  I (somewhat smugly) replied that it was to get rid of excess
CO2 in the bloodstream.  The question then became why does the amount of
CO2 in your blood increase when you are tired?  I started to say something
about accumulating waste products in your blood, but then remembered that
the theory of sleep functioning as a way to get rid of accumulated poisons
had been shot down a few years back.  So, what to say?  Why *does* CO2
accumulate in the blood (plasma)?  You would think that its diffusion 
would remain pretty constant given the concentration of it in the atmosphere,
so it wouldn't stay in the blood.  But if this is true, why *do* we yawn
when we're tired?  I have a hypothesis that it is to more fully expand the
lower lobes of our lungs that might become somewhat "stagnant" in terms of
gas exchange under normal or light breathing conditions, both to increase 
oxygen intake and CO2 outgo, but I don't have much to back this up with.
Anyone else have more reliable information?
-- 
			   Mike Sellers
     UUCP: {...your spinal column here...}!tektronix!tekecs!mikes

    "In a quiet moment, you can just hear them brain cells a-dyin'"