Why do we sleep?

Patrice Boily pboily at uoguelph.ca
Tue Mar 1 09:33:06 EST 1994


K.C. Baker (mbkxb at s-crim1.dl.ac.uk) wrote:
: Eric Mintz (mintz at orchid.UCSC.EDU) wrote:

: : OK, you are talking about two completely different things here.  An increase
: : in the heat radiating from your body is not the same as an increase in 
: : body temperature.  It is well documented that body temperature falls
: : upon entrance into non-REM sleep.  One way for the body to reduce its
: : temperature is by increasing radiative heat loss.

: : So are you talking about an increase in body temperature or an increase in 
: : radiative heat loss?

: So, how do you increase radiative heat loss without increasing temperature?
: Paint your skin matt black or grow radiator fins??

Lets get back to the problem!!.  I guess the confusion here s about core
(deep body) temperature vs surface temperature: if you increase the surface
temperature of your body, by peripheral vasodilatation for example, you
increase the rate of radiative heat loss, which can, but not necessarily
result in a reduction of the core temperature.  It is not uncommon to have
difference in surface temperatures of 10 deg., but core temperature, in
human, is generally stable within 1 or 2 deg. (Celcius).  As far as  know,
and there are numerous papers about this, all mammals have a decrease in
core temperature when they sleep, whether or not this is preceeded by  an
increase in surface temperature to "accelerate" the drop in core
temperature:  don't know.

This is all very nice but we are not really closer to the original question:
why animals sleep????

In fact, I would like to know how you define sleep: the best definition I
could find is that sleep is the state that interrupts periods of being awake!
In fact,  have seen an interesting paper, I don't remember where, that
stated that life is about sleeping, not being awake: the awake state is
just necessary to keep us alive (feeding, hunting, working, reproducing, etc.)
so we can go on sleeping...

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