【题目】 Most of us spend a third of our lives sleeping. Scientists have been studying the brain to learn what happens while we sleep. Scientists tell us that there are four stages(阶段)of sleep. During each stage our brain behaves differently, and so does our body. Each stage is marked by changes in the pattern of brain waves, which can be recorded by machines.

In the first stage, we drift off to sleep. Our muscles(肌肉)begin to relax. Our heartbeat and breathing slow down. Body temperature and blood pressure(压力)begin to drop. Stage—two sleep is a time of small, fast brain waves. Our eyes move quickly from side to side as if watching a movie. This is known as rapid eye movement, or REM sleep. During REM sleep, dreaming takes place. In stage three the brain wave becomes slower again.

Within about 45 minutes after falling sleep, we progress into the fourth stage – deep sleep. As this happens, our brain sends out slower but larger brain waves. This is the most restful kind of sleep, but it is also the time when sleepers are most likely to change positions or sleepwalk. After deep sleep we return to stage two. As the hours pass, we repeat the sleep cycle four or five times. Then we wake up.

1How many stages of sleep do we repeat several times during a night?

A.Two.B.Three.C.Four.D.Five.

2When does a person most likely change his positions?

A.When first falling asleep.B.During stage three.

C.During REM sleep.D.During deep sleep.

3Which of the following statements is TRUE?

A.We can dream in all the stages of sleep, especially during REM sleep.

B.It is impossible to record the pattern of our brain waves with machines.

C.Our body, like our brain, behaves differently during each stage of sleep.

D.It takes about 45 minutes to complete the sleep cycle after we fall asleep.

 0  142225  142233  142239  142243  142249  142251  142255  142261  142263  142269  142275  142279  142281  142285  142291  142293  142299  142303  142305  142309  142311  142315  142317  142319  142320  142321  142323  142324  142325  142327  142329  142333  142335  142339  142341  142345  142351  142353  142359  142363  142365  142369  142375  142381  142383  142389  142393  142395  142401  142405  142411  142419  159627 

违法和不良信息举报电话:027-86699610 举报邮箱:58377363@163.com

精英家教网