托福阅读真题+题目+答案：Sleep

托福阅读真题+题目+答案：Sleep

Why do we sleep? It can be dangerous to lose awareness of the external world. If nothing else, sleep might seem to take away from time that could be spent on productive, or even necessary, activities. But people cannot override indefinitely the desire to sleep; the body shuts down whether we like it or not. There are three general explanations that describe the adaptiveness of sleep: restoration, circadian cycles, and facilitation of learning.

1.The word “indefinitely” in the passage is closest in meaning to

A.easily

B.without effects

C.on purpose

D.endlessly

The restoration theory of sleep emphasizes that the brain and body need to rest and that sleep allows the body to repair itself. Indeed, growth hormone is released during deep sleep, and one of its functions if to facilitate repair of damaged tissue. Additional evidence that sleep is a time of restoration is that people who have engaged in vigorous physical activity, such as running marathons, seem to sleep longer. But people sleep even if they spend the day being physically inactive. In addition, it appears that sleep allows the brain to strengthen the body’s ability to fight disease.

2.According to paragraph 2, all of the following are considered to be evidence that sleep is needed for the body to repair itself EXCEPT:

A.The body’s resistance to disease is strengthened through sleep.

B.Body tissues are restored by the release of hormones during sleep.

C.The longer people sleep, the more activity occurs.

D.Sleep occurs whether or not physical activity has taken place.

Numerous laboratory studies have examined the effects of sleep deprivation on physical and cognitive performance. Surprisingly, most studies find that two or three days of deprivation have little effect on strength, athletic ability, or cognitive performance on complex tasks. Performing boring or ordinary tasks when sleep deprived, however, is nearly impossible. A brain-imaging study of sleep-deprived people found increased activation of the prefrontal cortex, suggesting that some brain regions may compensate for the effects of deprivation. Over long periods, however, sleep deprivation eventually causes problems with mood and cognitive performance. Indeed, studies using rats have found that extended sleep deprivation compromises the immune system and leads to death. Interestingly, sleep deprivation might serve one very useful purpose, which is helping people overcome depression. Consistent evidence has emerged over the past decade demonstrating that depriving depressed people of sleep sometimes alleviates their depression. This effect appears to occur because sleep deprivation leads to increased activation of serotonin receptors, which combat depression.

。。。。。余下托福阅读真题原文及题目答案省略！

托福阅读真题+题目+答案：Sleep完整版下载，10元有偿！