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Sleep is part of a persons daily activity cycle. There are several different stages of sleep, and they too occur in cycles._________(46). 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 will slow and become quite regular. Your brain waves slow down a bit too, with the alpha rhythm of rather fast waves predominating for first few minutes._________(47). For the next half hour or so, as you relax more and more, you will drift down through stage 2 and stage 3 sleep._________(48 ). 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._________(49). The delta rhythm will disappear, to be replaced by the activity pattern of brain waves. Your eyes will begin