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 (安睡), your eyes will roll about a bit, your temperature will drop slightly, your muscles will relax, and your breathing were 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 (眼皮) 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.
26.The stages of sleep take on ____.
A) an irregular aspect. B) a regular aspect C) a punctual aspect D) a similar aspect
27.Stage 4 sleep lasts ____.
A) about 80 minutes
B) about 40 60 minutes
C) about 30 munutes
D) about 20 40 minutes
28.The brain waves are the slowest during ____.
A) stage 1 C) stage 4 B) stage 2 and stage 3 D) REM sleep
29.In the second paragraph the word “dart” means ____.
A) glare B) move rapidly or suddenly C) stop moving D) gaze
30.One of the features of REM sleep is that ____.
A) there are large slow waves, though rapid for the first few minutes
B) you have the deepest sleep
C) there are no brain waves
D) the brain waves are a little fast and the brain becomes a little active
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