雅思阅读第088套P3:SLEEPREADING PASSAGE 3
You should spend about 20minutes on Questions 27 - 40, which are based on Reading Passage 3below.
SLEEP
WHY WE SLEEP
As the field of sleep researchis still relatively new, scientists have yet to determine exactly why peoplesleep. However, they do know that humans must sleep and, in fact, people cansurvive longer without food than without sleep. And people are not alone inthis need. All mammals, reptiles and birds sleep.
Scientists have proposed thefollowing theories on why humans require sleep:
· Sleep may be a way ofrecharging the brain. The brain has a chance to shut down and repair neuronsand to exercise important neuronal connections that might otherwise deterioratedue to lack of activity.
· Sleep gives the brain anopportunity to reorganise data to help find a solution to problems, processnewly-learned information and organise and archive memories.
· Sleep lowers a person'smetabolic rate and energy consumption.
· The cardiovascular systemalso gets a break during sleep. Researchers have found that people with normalor high blood pressure experience a 20 to 30% reduction in blood pressure and10 to 20% reduction in heart rate.
· During sleep, the body has achance to replace chemicals and repair muscles, other tissues and aging or deadcells.
· In children and teenagers,growth hormones are released during deep sleep.
When a person falls asleep andwakes up is largely determined by his or her circadian rhythm, a day-nightcycle of about 24 hours. Circadian rhythms greatly influence the timing, amountand quality of sleep.
For many small mammals such asrodents, sleep has other particular benefits, as it provides the only realopportunity for physical rest, and confines the animal to the thermalinsulation of a nest. In these respects, sleep conserves much energy in suchmammals, particularly as sleep can also develop into a torpor, whereby themetabolic rate drops significantly for a few hours during the sleep period. Onthe other hand, humans can usually rest and relax quite adequately duringwakefulness, and there is only a modest further energy saving to be gained bysleeping. We do not enter torpor, and the fall in metabolic rate for a humanadult sleeping compared to lying resting but awake is only about 5-10%.
A sizeable portion of theworkforce are shift workers who work and sleep against their bodies' naturalsleep-wake cycle. While a person's circadian rhythm cannot be ignored orreprogrammed, the cycle can be altered by the timing of things such as naps,exercise, bedtime, travel to a different time zone and exposure to light. Themore stable and consistent the cycle is, the better the person sleeps.Disruption of circadian rhythms has even been found to cause mania in peoplewith bipolar disorder.
The 'seven deadly sins'formulated by the medieval monks included Sloth. The Bible in Proverbs 6:9includes the line: 'How long will you sleep, O sluggard? When will you ariseout of your sleep?' But a more nuanced understanding of sloth sees it as adisinclination to labour or work. This isn't the same as the desire for healthysleep. On the contrary, a person can't do work without rest periods and no onecan operate at top performance without adequate sleep. The puritan work ethiccan be adhered to and respect still paid to the sleep needs of healthy humans.It is wrong to see sleep as a shameful activity.
Usually sleepers pass throughfive stages: 1, 2, 3, 4 and REM (rapid eye movement) sleep. These stagesprogress cyclically from 1 through REM then begin again. A complete sleep cycletakes an average of 90 to 110 minutes. The first sleep cycles each night haverelatively short REM sleeps and long periods of deep sleep but later in thenight, REM periods lengthen and deep sleep time decreases. Stage 1 is lightsleep where you drift in and out of sleep and can be awakened easily. In thisstage, the eyes move slowly and muscle activity slows. During this stage, manypeople experience sudden muscle contractions preceded by a sensation offalling. In stage 2, eye movement stops and brain waves become slower with onlyan occasional burst of rapid brain waves. When a person enters stage 3,extremely slow brain waves called delta waves are interspersed with smaller,faster waves. In stage 4, the brain produces delta waves almost exclusively.Stages 3 and 4 are referred to as deep sleep, and it is very difficult to wakesomeone from them. In deep sleep, there is no eye movement or muscle activity.This is when some children experience bedwetting, sleepwalking or nightterrors.
In the REM period, breathingbecomes more rapid, irregular and shallow, eyes jerk rapidly and limb musclesare temporarily paralysed. Brain waves during this stage increase to levelsexperienced when a person is awake. Also, heart rate increases, blood pressurerises and the body loses some of the ability to regulate its temperature. Thisis the time when most dreams occur, and, if awoken during REM sleep, a personcan remember their dreams. Most people experience three to five intervals ofREM sleep each night. Infants spend almost 50% of their time in REM sleep.Adults spend nearly half of sleep time in stage 2, about 20% in REM and theother 30% is divided between the other three stages. Older adults spendprogressively less time in REM sleep.
As sleep research is still arelatively young field, scientists did not discover REM sleep until 1953, whennew machines were developed to monitor brain activity. Before this discovery itwas believed that most brain activity ceased during sleep. Since then,scientists have also disproved the idea that deprivation of REM sleep can leadto insanity and have found that lack of REM sleep can alleviate clinicaldepression although they do not know why. Recent theories link REM sleep tolearning and memory.
SECTION 3: QUESTIONS 27-40
Questions 27-30
Choose the correct letter, A,B, C or D.
27Among other functions, sleep serves to
Ahelp the adult body develop physically.
Bpush daily problems from our minds.
Caccelerate the learning processsignificantly.
Dre-energise parts of the brain.
28'Torpor’ can be described as
Aa very deep sleep.
Ba long state of hibernation.
Cthe sleep all non-human mammalsexperience.
Da light sleep.
29Unlike small mammals, humans
Adon’t sleep to conserve energy.
Bdon’t sleep properly.
Csave only a small amount of energy bysleeping.
Dshow no decrease in their metabolic ratewhen they sleep.
30In stage 3 deep sleep
Athe eyes move slowly and there’s littlemuscle activity.
Bthere is an alternation of delta waves andsmall fast waves.
Cthere is an occasional burst of rapidbrain waves.
Dthere are no small fast waves.
Questions 31-35
Complete the flow-chart below.
Write NO MORE THAN THREEWORDS for each answer.
The Stages of Sleep
The individual drifts in and out of consciousness and can be woken up easily as they are only in a 31 _________________. Eye movement is slow and there is reduced muscle activity.
the speed of 32 _________________ activity slows and all movement of the eyes tends to stop.
Brain activity is dominated by delta waves, with a scattering of 33 _________________ also in evidence.
In a state of 34 _________________ , the brain emits delta waves almost exclusively. It is hard to wake the individual.
A period of rapid eye movement follows, during winch 35 _________________ patterns are not consistent and limb muscles enter a temporary state of paralysis.
Questions 36-40
Complete the summary.
Choose NO MORE THAN TWOWORDS from the passage for each answer.
Sleep is so essential to a person that he can actually go longer without food than with out sleep. During sleep, the brain has the chance to close down and do some repair work on neuronal connections which could otherwise 36 _________________ in a state of inactivity. Sleep also gives the brain the opportunity to organise data, especially newly-learned information.
During this rest period, the 37 _________________ drops and energy consumption goes down. At the same time, the cardiovascular system has a much-needed rest. While they go into a deep sleep, humans don't fall into 38 _________________, unlike some small animals such as rodents. A 39 _________________ of 24 hours is described as a person's 40 _________________, and this greatly influences a person's amout of sleep, and the type of sleep he gets.
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雅思阅读第088套P3-SLEEPhttp://www.tuonindefu.com/?p=2662雅思阅读第088套P3:SLEEP
