必背的英文每日一篇：第四十九天

必背的英文每日一篇：第四十九天 　　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 youfirst drift off into slumber, your eyes will roll about a bit, yourtemperature will drop slightly, your muscles will relax, and yourbreathing well slow and become quite regular. Your brain waves slow down abit too, with the alpha rhythm of rather fast waves predominating for thefirst few minutes. This is called stage 1 sleep. For the next half hour orso, as you relax more and more, you will drift down through stage 2 andstage 3 sleep. The lower your stage of sleep, the slower your brain waveswill be. Then about 40 to 60 minutes after you lose consciousness you willhave reached the deepest sleep of all. Your brain waves will show the largeslow 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 insteadabout 80 minutes after you fall into slumber, your brain activity levelwill increase again slightly. The delta rhythm will disappear, to bereplaced by the activity pattern of brain waves. Your eyes will begin todart around under your closed eyelids as if you were looking at somethingoccurring in front of you. This period of rapid eye movement lasts for some8 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 regularonce 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 80minutes later. 　　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。 δ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。