北京大学2011年考博英语真题

　　Part Four Reading Comprehension (20%)

　　Passage Four

　　Many adults may think they are getting enough shut-eye, but in a major sleep study almost 80 percent of respondents admitted to not getting their prescribed amount of nightly rest. So, what exactly is the right amount of sleep? Research shows that adults need an average of seven to nine hours of sleep a night for optimal functionality. Read on to see just how much of an impact moderate sleep deprivation can have on your mind and body.

　　By getting less than six hours of sleep a night, you could be putting yourself at risk of high blood pressure. When you sleep, your heart gets a break and is able to slow down for a significant period of time. But cutting back on sleep means your heart has to work overtime without its allotted break. In constantly doing so, your body must accommodate to its new conditions and elevate your overall daily blood pressure. And the heart isn’t the only organ that is overtaxed by a lack of sleeps. The less sleep you get, the less time the brain has to regulate stress hormones, and over time, sleep deprivation could permanently hinder the brain’s ability to regulate these hormones, leading to elevated blood pressure.

　　We all hang around in bed during our bouts of illness. But did you know that skipping out on the bed rest can increase your risk of getting sick? Prolonged sleep deprivation has long been associated with diminished immune functions, but researchers have also found a direct correlation between “modest” sleep deprivation — less than six hours — and reduced immune response. So try to toughen up your immune system by getting at least seven hours of sleep a night, and maintaining a healthy diet. You’ll be glad you got that extra hour of sleep the next time that bug comes around and leaves everyone else bedridden with a fever for three days.

　　During deep REM sleep, your muscles (except those in the eyes) are essentially immobilized in order to keep you from acting out on your dreams. Unfortunately, this effort your body makes to keep you safe while dreaming can sometimes backfire, resulting in sleep paralysis. Sleep paralysis occurs when the brain is aroused from its REM cycle, but the body remains in its immobilizing state. This can be quite a frightening sensation because, while your mind is slowly regaining consciousness, it has no control over your body, leaving some with a feeling of powerlessness, fear and panic. Most people experience this eerie phenomena at least once in their lives, but those who are sleep deprived are more likely to have panicked episodes of sleep paralysis that are usually accompanied by hallucinations, as well.

　　For a second, imagine all of your memories are erased ; every birthday, summer vacation, even what you did yesterday afternoon is completely lost, because you have no recollection of them. It’s a chilling thought, but that is what a life without sleep would be like. Sleep is essential to the cognitive functions of the brain, and without it, our ability to consolidate memories, learn daily tasks, and make decisions is impaired by a large degree. Research has revealed that REM sleep, or dream-sleep, helps solidify the “fragile” memories the brain creates throughout the day to that they can be easily organized and stored in the mind’s long-term cache.

　　56. According to the passage, what is the meaning of “sleep deprivation”?

　　A. To sleep for an average period of time. B. To sleep deeply without dreaming.

　　C. To sleep less than needed. D. To sleep modestly.

　　57. Which of the following statements is TRUE according to Paragraph 3?

　　A. When everyone else gets a fever, those with sleep deprivation will be abele to sleep longer.

　　B. When everyone else gets a fever, those who usually have adequate sleep will be alright.

　　C. Only modest sleep deprivation could weaken the immune system,

　　D. Prolonged sleep deprivation will not have impact on the immune system.

　　58. Why is there the so-called “sleep paralysis”?

　　A. It occurs when you are unable to wake up from dreams while you are sleeping.

　　B. It occurs when you brain immobilizes your body in order to keep you from dreaming.

　　C. Because you are usually too frightened to move your body when waking up from deep REM sleep.

　　D. Because your body, immobilized when dreaming, may still be unable to move even when your brain is waking up.

　　59. Which of the following statements is TRUE according to the last paragraph?

　　A. Memories are part of the cognitive function of the brain.

　　B. Memories created during the daytime are usually fragile and impaired.

　　C. You are likely to lose your memories of yesterday after a night’s sleep.

　　D. Long-term memory cannot be formed without dream-sleep.

　　60. What effects of sleep deprivation on human mind and body are discussed in this passage?

　　A. High blood pressure, a toughened immune system, sleep paralysis, and memory loss.

　　B. Blood pressure, immune system, sleep paralysis, and long-term memory.

　　C. Blood pressure, immune system, the brain and the body, and memory.

　　D. High blood pressure, a weakened immune system, sleep paralysis, and memory loss.

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