Sleep
is part of a person's daily activity cycle. There are several different
stages of sleep, and they too occur in cycles. If you are an average
sleeper, your sleep cycle is as follows. When you first drift off into
slumber, your eyes will roll about a bit, your temperature will drop
slightly, your muscles will relax, and your breathing well slow and
become quite regular. Your brain waves slow down a bit too, with the
alpha rhythm of rather fast
waves predominating for the first few
minutes. This is called stage 1 sleep. For the next half hour or so, as
you relax more and more, you will drift down through stage 2 and stage 3
sleep. The lower your stage of sleep, the slower your brain waves will
be. Then about 40 to 60 minutes after you lose consciousness you will
have reached the deepest sleep of all. Your brain waves will show the
large slow waves that are known as the delta rhythm. This is stage 4
sleep.
You do not remain at this deep fourth stage all night long, but instead
about 80 minutes after you fall into slumber, your brain activity level
will increase again slightly. The delta rhythm will disappear, to be
replaced by the activity pattern of brain waves. Your eyes will begin to
dart around under your closed eyelids as if you were looking at
something occurring in front of you. This period of rapid eye movement
lasts for some 8 to 15 minutes and is called REM sleep. It is during REM
sleep period, your body will soon relax again, your breathing will grow
slow and regular once more, and you will slip gently back from stage 1
to stage 4 sleep - only to rise once again to the surface of near
consciousness some 80 minutes later.
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