托福TPO24阅读真题及答案(二)

以下，是这次环球托福为正在进行托福备考的考友们整理了托福

TPO2 4

阅读真题及答案

Lake Breathing During Sleep

。我们建议考友们，先做真题，后看 答案进行验证自己的正确

率。之后，环球托福还会进一步推出托福

TPO24

阅读真题的做题思路讲解分析，做完真题

后，更便 于提高托福阅读能力。

托福

TPO24

阅读真题

Breathing During Sleep

Breathing During Sleep

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.

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 when asleep.

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

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

rate 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.

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.

But that is not all that changes. During all phases of sleep, several changes in the air passages have

been observed. It takes twice as much effort to breathe during sleep because of greater resistance

to airflow in the airways and changes in the efficiency of the muscles used for breathing. Some of

the muscles that help keep the upper airway open when breathing tend to become more relaxed

during sleep, especially during REM (the phase of sleep in which there is rapid eye movement).

Without this muscular action, inhaling is like sucking air out of a balloon

—

the narrow passages

tend to collapse. Also there is a regular cycle of change in resistance between the two sides of the

nose.

If

something

blocks

the

side,

such

as

congestion

from

allergies

or

a

cold,

then

resistance

increases

dramatically.

Coupled

with

these

factors

is

the

loss

of

the

complex

interactions among the muscles that can change the route of airflow from nose to mouth.

Other respiratory regulating mechanisms apparently cease functioning during sleep. For example,

during wakefulness there is an immediate, automatic, adaptive increase in breathing effort when

inhaling is made more difficult (such as breathing through a restrictive face mask). This reflexive

adjustment is totally absent during NREM sleep. Only after several inadequate breaths under such

conditions, resulting in the considerable elevation of carbon dioxide and reduction of oxygen in

the blood, is breathing effort adjusted. Finally, the coughing reflex in reaction to irritants in the

airway produces not a cough during sleep but a cessation of breathing. If the irritation is severe

enough, a sleeping person will arouse, clear the airway, then resume breathing and likely return to

sleep.

Additional

breathing

changes

occur

during

REM

sleep

that

is

even

more

dramatic

than

the

changes

that

occur

during

NREM.

The

amount

of

air

exchanged

is

even

lower

in

REM

than

NREM

because,

although

breathing

is

more

rapid

in

REM,

it

is

also

more

irregular,

with

brief

episodes of shallow breathing or absence of breathing. In addition, breathing during REM depends

much more on the action of the diaphragm and much less on rib cage action.

Paragraphy1: 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. 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

when

asleep.

托福

TPO24

阅读真题

Br eathing During Sleep

题目

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 activities during wakefulness.

C. It is able to bypass the automatic system.

D. It produces an irregular breathing pattern.

3.

The word exclusive in the passage is closest in meaning to

A. consistent

B. perfect

C. partial

D. sole