Why do we sleep?

[Brian T. Greuel]

In article <1994Feb17.150343.25105 at Virginia.EDU>, mgk2r at Virginia.EDU (Michael 
G. Kurilla) responded to the following question by 
hcorbett at garnet.berkeley.edu:

> > Why can people usually only sleep withtheir eyes closed? 
> 
Michael's response was, "Light stimulation."

I would like to ask a related question that I have often wondered about:

Why do we sleep?  Is there something that builds up in our bodies that gives 
us a feeling of fatigue and that during sleep gets metabolized somehow so 
that we feel refreshed upon waking?

Just curious.

Brian Greuel
University of Scranton
greuelb1 at jaguar.uofs.edu