Why do we sleep?

Antonio Guia guia at CC.UManitoba.CA
Thu Apr 7 20:39:39 EST 1994


On 8 Apr 1994, Eric Mintz wrote:
> >I am told that I too radiate a great deal of heat while sleeping.  My
> Since almost all of us cool down while we are sleeping (relative to waking),
> it is normal for a person to radiate heat during the first part of the night.

Radiating body heat is not something the body decides to do.   Radiated
heat is instead something that happens by itself.  I don't know if there's
any preferential circulation to the skin while sleeping but I would guess
that there is not since sleeping is an evolutionary adaptation to conserve
energy (supposedly) and loosing body heat is counterproductive to the end
goal.  

The heat which dissipates from the body during sleep is no different from
that which escapes during waking hours.   Since we are wrapped up under
blankets and for some of us also huddled up with another person then there
is decreased heat loss since our immediate surroundings act as insulation,
keeping the heat in.  We can feel this heat which is kept in but just
outside our bodies much easier when we are not moving and are wrapped up. 
When we are moving about the heat is dissipated away from the body much
faster therefore we do not feel the heat.

The perfect example would be to ask you to wrap yourself up in a blanket
and then stand in a room where there is no air currents to draw the heat
away from your body (as if you were in bed but standing instead).  The
extra work required to keep you standing or even awake will heat up your
immediate area much faster.  

While asleep our body temperature actually decreases since our metabolic
rate (work performed) is actually lower.   Work is directly proportional
to heat (except in brown fat if i remember correctly).

-tg






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