英语听力文摘 你为何要睡觉？
You Snooze or You Lose
几乎每个人在忙碌了一天之后，都要香香地睡上一觉。当然也有活了一辈子不 睡觉的人，但那是极个别的。人要睡觉是一种生理反应，是大脑神经活动的一部分， 是大脑皮质内神经细胞继续兴奋之后产生了抑制的结果。当抑制作用在大脑皮质内 占优势的时候，人就会睡觉。 人们在生活中，有工作，有休息，在神经活动中，有兴奋，有抑制。抑制是为了保护神经细胞，以便让它重新兴奋，让人们继续工作。
It’s such a commonplace event that you probably never asked yourself why you sleep. But from a scientific point of view, this is far from a mundane matter — in fact, for sleep researchers, it’s one of the biggest unanswered questions in the field.
Stop and think about it for a second. Why should we sleep? Is it because we get tired? But we sleep every night, even when we have had plenty of rest.Furthermore, if you were designing an animal, would you have it (1)lapse into prolonged periods of unconsciousness every twenty-four hours? Shouldn’t that put it at a terrible disadvantage?
There are no doubt several different answers to this question, but let’s just consider one overall purpose sleep may fulfill: sleep as a survival strategy.
Human beings are “diurnal” creatures. That means we are normally active during daylight hours, when our senses function most effectively. At night, humans do rather poorly: we can’t see objects well, our color vision is entirely lost, and we don’t have the smelling or hearing acuity of other animals. So it actually does makes sense to have us (2)stay put during the dangerous period when “nocturnal,” or night-waking, animals are (3)on the prowl. And one sure way to make sure we don’t stumble around and get lost or eaten is to have us immobilized for seven or eight hours, rising again only when the light is back and our survival chances are better.
It’s not the only reason we sleep; but in terms of evolution, it may have been one of the first reasons — perhaps even the most important one.
Notes:
(1)lapse into 陷入
The pupils lapsed into silence when the schoolteacher came into the classroom.
当老师走进教室时，学生们安静下来。
(2)stay put 留在原处不动
The policeman ordered him to stand up and stay put.
警察命令他站起来别动。
(3)on the prowl 徘徊
Today there is still local demand for banking staff: Tesco, a retailer expanding into the sector, is on the prowl.
现在还有本地仍有对银行工作人员需求：一家扩张到银行业部门的零售商特易购在寻求机会。
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