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【王鑫托福阅读】托福TPO全集之TPO24-2

TPO24

TPO24-2 Breathing During Sleep

1. According to paragraph 1, which of the following can be inferred about the diaphragm during sleep?

A During sleep the diaphragm requires increased movement of the rib cage. B The diaphragm helps with breathing as movements of the rib cage decrease during sleep.

C The diaphragm requires a great amount of pressure to function properly. D The diaphragm contributes to the effective functioning of the rib cage. 2. According to paragraph 2, all of the following are true of the voluntary breathing system EXCEPT:

A It has its control center in the brain stem.

B It controls breathing for a number of activiti during wakefulness. ▲ C It is able to bypass the automatic system. D It produces an irregular breathing pattern. ^ mm

Of all the physiological differences in human sleep compared with wakefulness that have been discovered in the last decade, changes in respiratory control are most dramatic. Not only are there differences in the level of the functioning of respiratory systems, there are even changes in how they function.

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Movements of the rib cage for breathing are reduced during sleep, making the contractions of the diaphragm more important. Yet because of the physics of lying down, the stomach applies weight against the diaphragm and makes it more difficult for the diaphragm to do its job. However, there are many other changes that affect respiration 通 1 1\ when asleep.

During wakefulness, breathing is controlled by two interacting systems. The first is an automatic, ,毳.

metabolic system whose control is centered in the brain stem. It subconsciously adjusts breathing rate w

and depth in order to regulate the levels of carbon dioxide (CO2) and oxygen (O2), and the acid-base ratio in the blood. The second system is the voluntary, behavioral system. Its control center is based in the forebrain, and it regulates breathing for use in speech, singing, sighing, and so on. It is capable of ignoring or overriding the automatic, metabolic system and produces an irregular pattern of breathing.

3. The word exclusive in the passage is closest in meaning to A consistent B perfect C partial D sole

4. According to paragraph 3, which of the following may occur just before NREM sleep begins?

A The automatic, metabolic system may increase its dependence on air exchanges.

B Breathing can stop for a short time as a person falls asleep.

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C An increase in the oxygen level in the blood can occur as sleep becomes fully obtained.

D The level of carbon dioxide in the blood may drop suddenly.

5. What is the author's purpose in stating that inhaling is like sucking air out of a balloon?

A To refute the argument that additional effo necessary for breathing during sleep B To argue that REM sleep is more important than NREM sleep

C To illustrate the difficulty of breathing during sleep D To illustrate how blockage of narrow passages can be prevented during sleep

6. All of the following are mentioned in paragraph 4 as being characteristic of breathing during sleep EXCEPT A relaxation of the muscles involved in the respiratory system

B changes in resistance between the two sides of the nose

C easier airflow in the passages of the upper airway D absence of certain complex muscle interactions

During NREM (the phase of sleep in which there is no rapid eye movement) breathing becomes deeper and more regular, but there is also a decrease in the breathing rate, resulting in less air being exchanged overall. This occurs because during NREM sleep the

automatic, metabolic system has exclusive control over breathing and the body uses less oxygen and produces less carbon dioxide. Also, during sleep the automatic metabolic system is less responsive to carbon dioxide levels and oxygen levels in the blood. Two things result from these changes in breathing control that occur during sleep. First, there may be a brief cessation or reduction of breathing when falling asleep as the sleeper waxes and wanes between sleep and wakefulness and their differing control mechanisms. Second, once sleep is fully obtained, there is an increase of carbon dioxide and a decrease of oxygen in the blood that persists during NREM. V /