Why do we sleep?

Eric Mintz mintz at orchid.UCSC.EDU
Tue Mar 1 10:52:30 EST 1994

In article <2kvjn2$21v at nermal.cs.uoguelph.ca> pboily at uoguelph.ca (Patrice Boily) writes:
>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??

You increase the gradient between your skin and the environment by redirecting
blood flow to the skin.

>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...

Sleep is a period of inactivity, characterized by reduced metabolic rate and
an increased threshold for arousal.  It is also defined by its electro-
physiological characteristics - reduced level of muscle tension, increased
slow wave activity in the EEG (for non-REM sleep).

Also, we need to distinguish between whether the question is "Why do *we*
sleep?" and "Why did sleep evolve?"  The theory you mention above tries
to address the latter question, not the former.

mintz at biology.ucsc.edu

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