考研优美英语作文背诵049
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Sleep
Sleep is part of a person's daily activity cycle. There are severaldifferent stages of sleep, and they too occur in cycles. If you are anaverage sleeper, your sleep cycle is as follows. When you first drift off intoslumber, your eyes will roll about a bit, your temperature will dropslightly, your muscles will relax, and your breathing well slow andbecome quite regular. Your brain waves slow down a bit too, with thealpha 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 relaxmore and more, you will drift down through stage 2 and stage 3 sleep. The loweryour stage of sleep, the slower your brain waves will be. 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 deltarhythm. This is stage 4 sleep.You do not remain at this deep fourth stageall night long, but instead about 80 minutes after you fall into slumber,your brain activity level will increase again slightly. The delta rhythm willdisappear, to be replaced by the activity pattern of brainwaves. Your eyes will begin to dart around under your closed eyelids asif you were looking at something occurring in front of you. This period ofrapid 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 breathingwill grow slow and regular once more, and you will slip gently back fromstage 1 to stage 4 sleep - only to rise once again to the surface of nearconsciousness some 80 minutes later.
全文翻译：睡眠
睡眠是人每天日常活动循环的一部分。人的睡眠分几个阶段，而这些阶段也是循环发生的。 如果你是一个正常的睡眠者，你的睡眠循环会这样进行。在你开始昏昏入睡时，你 的眼睛会滚动几下，体温略有下降，肌肉放松，呼吸变得缓慢而有节奏。除了开始几分钟比较快的α节奏外，脑电波也稍有减缓。这被称为第一阶段睡眠。在随后约半小时内，你 进一步放松，进入第二和第三阶段睡眠。 睡眠越深入，脑电波就越缓慢。大约在开始睡眠 后的 40 到 60 分钟，你将进入沉睡状态。 这时的脑电波表现为巨大的缓波，被称为δ节奏。 这就是第四阶段睡眠。但你并不是整夜都保持这种沉睡状态。入睡后约 80 分钟左右，你 的大脑运动水平会再度略有提高。节奏消失，并被脑电波的运动图形取代。 你的眼睛会在闭着的眼睑下迅速转动，就好象你在看着眼前发生的什么事情。这种迅速的眼球运动持 续约 8～15 分钟，这一阶段睡眠被称之为快速眼动(REM)睡眠。在 REM 睡眠阶段，你的肢 体会很快再度放松，呼吸也再次放慢并变得有节奏，你会轻松地从第一阶段滑入第四阶段睡 眠-直到大约 80 分钟后重新接近清醒状态。
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