Sleep

Sleep is part of aperson's daily activity cycle .There are several different stages of sleep,andthey too occur in cycles.______(46)

When you first driftoff into slumber,your eyes will roll about a bit,your temperature will dropslightly,your muscles will relax,and your breathing will slow and become quite

regular. Your brainwaves slow down a bit too,with the alpha rhythm of rather fast wavespredominating for the first few minutes.______(47)

For the next halfhour or so,as you relax more and more,you will drift down through stage 2 andstage 3 sleep.______(48)

Then about 40 to 60minutes after you lose consciousness you will have reached the deepest sleep ofall.Your brain waves will show the large slow waves that are known as

the delta rhythm.

This is stage 4sleep.You do not remain at this deep fourth stage all night long,but insteadabout 80 minutes after you fall into slumber,your brain activity level willincrease

again slightly.______(49)

Your eyes will beginto dart around under your closed eyelids as if you were loo-king at somethingoccurring in front of you.______(50)

It is during REMsleep period,your body will soon relax again,your breathing will grow slow andregular once more,and you will slip gently back from stage 1 to stage 4

sleep-only to riseonce again to the surface of near consciousness some 80 minutes later.______(50)

A.The delta rhythmwill disappear,to be replaced by the activity pattern of brain waves.

B. If you are anaverage sleeper,your sleep cycle is as follows.

C. In stage 4 sleeppeople tend to dream.

D. The lower yourstage of sleep,the slower your brain waves will be.

E.This period ofrapid eye movement lasts for some 8 to 15 minutes and is called REM sleep.