Sleep
[size=3][color=#29384e][font=Times New Roman]Sleet is part of a person[/font][font=宋体]‘[/font][font=Times New Roman]s daily activity cycle. There are several different stages of sleep[/font][font=宋体]，[/font][font=Times New Roman] and they too occur in cycles. If you are an average sleeper[/font][font=宋体]，[/font][font=Times New Roman] your sleep cycle is as follows. When you fist drift off into slumber[/font][font=宋体]，[/font][font=Times New Roman] your eyes will roll about a bit[/font][font=宋体]，[/font][font=Times New Roman] you temperature will drop slightly[/font][font=宋体]，[/font][font=Times New Roman] your muscles will relax[/font][font=宋体]，[/font][font=Times New Roman] 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[/font][font=宋体]，[/font][font=Times New Roman] with the alpha rhythm of rather fast waves 1 sleep. For the next half hour or so[/font][font=宋体]，[/font][font=Times New Roman] as you relax more and more[/font][font=宋体]，[/font][font=Times New Roman] 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.[/font][/color][/size][size=3][color=#29384e][font=Times New Roman] [/font][/color][/size]
[size=3][color=#29384e][font=宋体] [/font][font=Times New Roman]You do not remain at this deep fourth stage all night long[/font][font=宋体]，[/font][font=Times New Roman] but instead about 80 minutes after you fall into slumber[/font][font=宋体]，[/font][font=Times New Roman] your brain activity level will increase again slightly. The delta rhythm will disappear[/font][font=宋体]，[/font][font=Times New Roman] 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[/font][font=宋体]，[/font][font=Times New Roman] your body will soon relax again[/font][font=宋体]，[/font][font=Times New Roman] your breathing will slip gently back from stage 1 to stage 4 sleep[/font][font=宋体]——[/font][font=Times New Roman]only to rise once again to the surface of near consciousness some 80 minutes later.[/font][/color][/size]
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