sample essays of IELTS

49 Sleep

Sleet is part of a persons 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 fist drift off
into slumber, your eyes will roll about a bit, you temperature will drop
slightly, your muscles will relax, and your breathing well slow and
become quite regular. Your brain waves slow and become quite regular.
Your brain waves slow down a bit too, with the alpha rhythm of rather
fast waves 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. slower your brain waves will be. Then about 40to 69
minutes after you lose consciousness you will have reached the deepest
sleep of all. Your brain 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 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.