醫(yī)學(xué)英語原文翻譯1至5單元

1.

生理學(xué)是研究生物體正常功能的一門科學(xué)。它研究生物體如何進(jìn)行各種活動，如何飲食，如何運(yùn)動，如何適應(yīng)不斷改變的環(huán)境，如何繁殖后代。這門學(xué)科包羅萬象，涵蓋了生物體整個生命過程。生理學(xué)成功地解釋了生物體如何進(jìn)行日常活動，基于的觀點(diǎn)是生物體好比是結(jié)構(gòu)復(fù)雜而靈巧的機(jī)器，其操作受物理和化學(xué)規(guī)律控制。盡管從生物學(xué)整個范疇看，生物體某些活動過程是相似的，如基因編碼的復(fù)制，但許多過程還是某些生物體群組特有的。鑒于此，將這門學(xué)科分成不同部分研究如細(xì)菌生理學(xué)，植物生理學(xué)和動物生理學(xué)是有必要的。Physiology

is

the

study

of

thefunctions

of

living

matter.

It

is

concerned

with

how

an

organism

performs

its

varied

activities:

how

it

feeds,

how

it

moves,

how

it

adapts

to

changing

circumstances,

how

it

spawns

new

generations.

The

subject

is

vast

and

embraces

the

whole

of

life.

The

success

of

physiology

in

explaining

how

organisms

perform

their

daily

tasks

is

based

on

the

notion

that

they

are

intricate

and

exquisite

machines

whose

operation

is

governed

by

the

laws

of

physics

and

chemistry.

Although

some

processes

are

similar

across

the

whole

spectrum

of

biology—the

replication

of

the

genetic

code

for

example—many

are

specific

to

particular

groups

of

organisms.

For

this

reason

it

is

necessary

to

divide

the

subject

into

various

parts

such

as

bacterial

physiology,

plant

physiology,

and

animal

physiology.

2.正如要了解一個動物如何活動，首先需要了解它的構(gòu)成，要充分了解一個生物體的生理學(xué)活動就必須掌握全面的解剖學(xué)知識。一個生物體的各部分起著什么作用可通過實(shí)驗(yàn)觀察得知。盡管我們對志愿者進(jìn)行了許多重要的生理調(diào)查，但是實(shí)驗(yàn)條件需要精確控制，所以我們當(dāng)前大多生理知識還是源于對其它動物如青蛙，兔子，貓和狗等的研究。當(dāng)我們明確大多數(shù)動物物種的特定生理過程存在共同之處時，相同的生理原理適用于人類也是合理的。通過這種方法，我們獲得了大量的知識，從而讓我們對人類生理學(xué)有了更深入的了解，為我們有效治療許多疾病提供了一個堅實(shí)的基礎(chǔ)。To

study

how

an

animal

works

it

isfirst

necessary

to

know

how

it

is

built.

A

full

appreciation

of

the

physiology

of

an

organism

must

therefore

be

based

on

a

sound

knowledge

of

its

anatomy.

Experiments

can

then

be

carried

out

to

establish

how

particular

parts

perform

their

functions.Although

there

have

been

many

important

physiological

investigations

on

human

volunteers,

the

need

for

precise

control

over

the

experimental

conditions

has

meant

that

much

of

our

present

physiological

knowledge

has

been

derived

from

studies

on

other

animals

such

as

frogs,

rabbits,

cats,

and

dogs.When

it

is

clear

that

a

specific

physiological

process

has

a

common

basis

in

a

wide

variety

of

animal

species,

it

is

reasonable

to

assume

that

the

same

principles

will

apply

to

humans.

The

knowledge

gained

from

this

approach

has

given

us

a

great

insight

into

human

physiology

and

endowed

us

with

a

solid

foundation

for

the

effective

treatment

of

many

diseases.The

organization

of

the

body3.機(jī)體的基本組成物質(zhì)是細(xì)胞，細(xì)胞結(jié)合在一起形成組織。組織的基本類型有上皮組織，結(jié)締組織，神經(jīng)組織，肌組織，每類組織都有各自的特征。許多結(jié)締組織中細(xì)胞量相對較少，但是有大量的細(xì)胞外基質(zhì)。相比而言，光滑的肌組織由大量密密麻麻的肌細(xì)胞通過特定的細(xì)胞連接組成。各種器官如腦，心臟，肺，小腸和肝等由不同種類的組織聚集而成。這些器官是不同生理系統(tǒng)的組成部分。心臟和血管組成心血管系統(tǒng)；肺，器官，支氣管，胸壁和膈肌組成呼吸系統(tǒng)；骨骼和骨骼肌組成骨骼肌系統(tǒng)；大腦，脊髓，自主神經(jīng)和神經(jīng)中樞以及周圍軀體神經(jīng)組成神經(jīng)系統(tǒng)等等。3.

The

building

blocks

of

the

body

are

the

cells,which

are

grouped

together

to

form

tissues.

The

principal

types

of

tissue

are

epithelial,

connective,

nervous,

and

muscular,

each

with

its

own

characteristics.

Many

connective

tissues

have

relatively

few

cells

but

have

an

extensive

extracellular

matrix.

In

contrast,

smooth

muscle

consists

of

densely

packed

layers

of

muscle

cells

linked

together

via

specific

cell

junctions.Organs

such

as

the

brain,

the

heart,

the

lungs,

the

intestines,

and

the

liver

are

formed

by

the

aggregation

of

different

kinds

of

tissues.

The

organs

are

themselves

parts

of

distinct

physiological

systems.

The

heart

and

blood

vessels

form

the

cardiovascular

system;

the

lungs,

trachea,

and

bronchi

together

with

the

chest

wall

and

diaphragm

form

the

respiratory

system;

the

skeleton

and

skeletal

muscles

form

the

musculoskeletal

system;

the

brain,

spinal

cord,

autonomic

nerves

and

ganglia,

and

peripheral

somatic

nerves

form

the

nervous

system,

and

so

on.

4.

細(xì)胞在形體和功能上差異很大，但是它們有某些共同的特征。第一，細(xì)胞由一層薄膜也稱細(xì)胞膜包被；第二，細(xì)胞能把大分子分解為小分子釋放能量供活動所需；第三，在生命過程中某個階段，細(xì)胞體內(nèi)存在一個以脫氧核糖核酸(DNA)形式出現(xiàn)，包含基因信息的細(xì)胞核。4.Cells

differ

widely

in

form

and

function

but

they

all

have

certain

common

characteristics.

First,

they

are

bounded

by

a

limiting

membrane,

the

plasma

membrane.

Secondly,

they

have

the

ability

to

break

down

large

molecules

to

smaller

ones

to

liberate

energy

for

their

activities.

Thirdly,

at

some

point

in

their

life

history,

they

possess

a

nucleus

which

contains

genetic

information

in

the

form

of

deoxyribonucleic

acid

(DNA).

5.

活體細(xì)胞不斷轉(zhuǎn)化物質(zhì)。細(xì)胞分解葡萄糖和脂肪，為自身生長和修復(fù)所需的蛋白質(zhì)合成和運(yùn)動等其它活動提供能量。這些化學(xué)變化統(tǒng)稱為新陳代謝。把大分子分解為小分子的過程稱為分解代謝，小分子合成大分子的過程稱為合成代謝。5.

Living

cells

continually

transform

materials.

They

break

down

glucose

and

fats

to

provide

energy

for

other

activities

such

as

motility

and

the

synthesis

of

proteins

for

growth

and

repair.

These

chemical

changes

are

collectively

called

metabolism.

The

breakdown

of

large

molecules

to

smaller

ones

is

called

catabolism

and

the

synthesis

of

large

molecules

from

smaller

ones

anabolism.

6.

細(xì)胞在進(jìn)化過程中不斷分化進(jìn)行不同的功能活動。有些細(xì)胞具有收縮能力（如肌細(xì)胞），有些可以傳導(dǎo)電信號（如神經(jīng)細(xì)胞）。進(jìn)一步進(jìn)化的細(xì)胞能夠分泌不同物質(zhì)如荷爾蒙（如內(nèi)分泌細(xì)胞）或酶。胚胎發(fā)育過程中，分化的過程由于很多不同細(xì)胞來源于受精卵而再次發(fā)生。6.

In

the

course

of

evolution,

cells

began

to

differentiate

to

serve

different

functions.

Some

developed

the

ability

to

contract

(muscle

cells),

others

to

conduct

electrical

signals

(nerve

cells).

A

further

group

developed

the

ability

to

secrete

different

substances

such

as

hormones

or

enzymes.

During

embryological

development,

this

process

of

differentiation

is

re-enacted

as

many

different

types

of

cell

are

formed

from

the

fertilized

egg.

7.

大多數(shù)組織包含有不同的細(xì)胞類型。比如，血液中含紅細(xì)胞，白細(xì)胞和血小板。紅細(xì)胞運(yùn)輸全身的氧氣。白細(xì)胞在抵御感染時起重要作用，血小板是血液凝集過程中重要的成分。結(jié)締組織有多種不同類型，但有一個共同特征，即細(xì)胞分布在豐富的細(xì)胞外基質(zhì)中。神經(jīng)組織含神經(jīng)細(xì)胞和神經(jīng)膠質(zhì)細(xì)胞。7.

Most

tissues

contain

a

mixture

of

cell

types.

For

example,

blood

consists

of

red

cells,

white

cells,

and

platelets.

Red

cells

transport

oxygen

around

the

body.

The

white

cells

play

an

important

role

in

defense

against

infection

and

the

platelets

are

vital

components

in

the

process

of

blood

clotting.

There

are

a

number

of

different

types

of

connective

tissue

but

all

are

characterized

by

having

cells

distributed

tissue

is

broken

down

to

provide

glucose

for

the

generation

of

energy.

Here,

the

intake

of

protein

is

less

than

the

rate

of

breakdown

and

the

individual

is

said

to

have

a

negative

nitrogen

balance.

Equally,

if

the

body

tissues

are

being

built

up,

as

is

the

case

for

growing

children,

pregnant

women

and

athletes

in

the

early

stages

of

training,

the

daily

intake

of

protein

is

greater

than

the

normal

body

turnover

and

the

individual

is

in

positive

nitrogen

balance.21.

平衡的概念可以應(yīng)用到機(jī)體的任何構(gòu)成成分上，包括水和鹽，而且平衡在機(jī)體調(diào)節(jié)其自身成分上是非常重要的。攝入必須等于所需，為維持機(jī)體平衡，任何多余的能量都必須排出。此外，因?yàn)闄C(jī)體的每種化學(xué)成分都有一個可取的濃度范圍，控制機(jī)制維持這個范圍。例如，兩餐間血糖濃度大約為4-5mmol.l–1

.

進(jìn)食后不久，血糖含量超過這一范圍，刺激胰腺分泌胰島素，降低濃度。隨著葡萄糖濃度的下降，胰島素分泌減少。在此情況下，循環(huán)胰島素水平的改變都是為了使血漿中的葡萄糖維持在一個合適的范圍內(nèi)。這種調(diào)節(jié)稱為負(fù)反饋機(jī)制。在胰島素分泌期間，葡萄糖像肝糖原或脂肪一樣被儲存。21.

This

concept

of

balance

can

be

applied

to

any

of

the

body

constituents

including

water

and

salt

and

is

important

in

considering

how

the

body

regulates

its

own

composition.

Intake

must

match

requirements

and

any

excess

must

be

excreted

for

balance

to

be

maintained.

Additionally,

for

each

chemical

constituent

of

the

body

there

is

a

desirable

concentration

range,

which

the

control

mechanisms

are

adapted

to

maintain.For

example,

the

concentration

of

glucose

in

the

plasma

is

about

4–5mmol.l–1

between

meals.

Shortly

after

a

meal,

plasma

glucose

rises

above

this

level

and

this

stimulates

the

secretion

of

the

hormone

insulin

by

the

pancreas,

which

acts

to

bring

the

concentration

down.

As

the

concentration

of

glucose

falls,

so

does

the

secretion

of

insulin.

In

each

case,

the

changes

in

the

circulating

level

of

insulin

act

to

maintain

the

plasma

glucose

at

an

appropriate

level.

This

type

of

regulation

is

known

as

negative

feedback.

During

the

period

of

insulin

secretion,

the

glucose

is

being

stored

as

either

glycogen

or

fat.

22.

負(fù)反饋環(huán)是在機(jī)體出現(xiàn)紊亂時，將一些變量控制在限定范圍內(nèi)的一個控制系統(tǒng)。雖然上面的例子講到血糖，但這一基本原則可以應(yīng)用到其它生理變量中如體溫、血壓和血漿的滲透濃度。負(fù)反饋環(huán)需要一種能對不確定的變量做出反應(yīng)而對其它生理變量不應(yīng)答的傳感器。因此，滲透壓感受器應(yīng)該能對機(jī)體體液滲透的變化而不是體溫和血壓的變化產(chǎn)生應(yīng)答。感受器傳遞的信息必須和理想水平（系統(tǒng)的調(diào)定點(diǎn)）以比較者的身份，以某種方式進(jìn)行比較。如果兩者不相符，一個錯誤信號就會傳遞給效應(yīng)器，效應(yīng)器是一種能使變量保持在理想水平的系統(tǒng)。負(fù)反饋的這些特點(diǎn)可以通過檢測一種簡單的加熱系統(tǒng)來理解。被控制的變量是室溫，它可以由一個溫度計檢測到，效應(yīng)器是一種加熱器。當(dāng)室溫降低到調(diào)定點(diǎn)以下時，溫度計就可以監(jiān)測到溫度的變化而開啟加熱器，對室內(nèi)進(jìn)行加溫，直到室溫升高到先前調(diào)好的調(diào)定點(diǎn)，加熱器關(guān)閉。23.

a

negative

feedback

loop

is

a

control

system

that

acts

to

maintain

the

level

of

some

variable

within

a

given

range

following

a

disturbance.

Although

the

example

given

above

refers

to

plasma

glucose,

the

basic

principle

can

be

applied

to

other

physiological

variables

such

as

body

temperature,

blood

pressure,

and

the

osmolality

of

the

plasma.

a

negative

feedback

loop

requires

a

sensor

of

some

kind

that

responds

to

the

variable

in

question

but

not

to

other

physiological

bariables,

thus

an

osmoreceptor

should

respind

to

changes

in

osmolality

of

the

body

fluids

but

not

to

changes

in

body

temperature

or

blood

pressure.

the

information

from

the

sensor

must

be

compared

in

some

way

with

the

desired

level

by

some

form

of

comparator.

if

the

two

do

not

match

,an

error

signal

is

transmitted

to

an

effector,

a

system

that

can

act

to

restore

the

variable

to

its

desired

level

.these

features

of

negative

feedback

can

be

appreciated

by

examining

a

simple

heating

system

.the

controlled

variable

is

room

temperature,

which

is

sensed

by

a

thermostat.

the

effector

is

a

heater

of

some

kind

.when

the

room

temperature

falls

below

the

set

point,the

temperature

difference

is

detected

by

the

thermostat

which

switches

on

the

heater

.this

heats

the

room

until

the

temperature

reaches

the

per

set

level

whereupon

the

heater

is

switched

off.23.

總而言之，機(jī)體實(shí)際上是由100萬億細(xì)胞有序組成了不同的功能結(jié)構(gòu)，其中一些被稱為器官。每個功能結(jié)構(gòu)都在維持細(xì)胞外液穩(wěn)態(tài)方面發(fā)揮其作用，這稱之為內(nèi)環(huán)境。只要內(nèi)部環(huán)境處于正常狀態(tài)，機(jī)體細(xì)胞繼續(xù)生存并正常運(yùn)行。每個細(xì)胞都從穩(wěn)態(tài)中獲益，反過來，每個細(xì)胞都為穩(wěn)態(tài)做出貢獻(xiàn)。這種相互作用促使機(jī)體持續(xù)自主運(yùn)行，直至一個或多個功能系統(tǒng)不能正常運(yùn)轉(zhuǎn)。此時，機(jī)體所有細(xì)胞都會受損。功能極度異常會導(dǎo)致死亡，輕微的功能異常導(dǎo)致疾病的發(fā)生。23.To

sumarize,

the

body

is

actually

a

social

order

of

about

100

trillion

cells

organized

into

different

functional

structures,some

of

which

are

called

organs.each

functional

structures

its

share

to

the

maintenance

of

homeostatic

conditions

in

the

extracellular

fluid,which

is

called

the

internal

environment.as

long

as

normal

conditions

are

maintained

in

this

internal

environment

,the

cells

of

the

body

continue

to

live

and

function

properly.Each

cell

benefits

from

homeostasis,and

in

turn,each

cell

contributes

its

share

toward

the

maintenance

of

homeostasis.This

reciprocal

interplay

provides

continuous

automaticity

of

the

body

until

one

or

more

functional

systems

lose

their

ability

to

contribute

their

share

of

function.When

this

happens,all

the

cells

of

the

body

suffer.Extreme

dysfunction

leads

to

death;moderate

dysfunction

leads

to

sickness.1.心動周期是一次心跳中的一系列活動。心動周期最簡單的形式就是,是兩個心房的同時收縮,

緊隨其后，兩個心室同時進(jìn)行收縮。但是,

血液從心房進(jìn)入心室和從心室進(jìn)入動脈這兩個過程之間有很大的差別。The

cardiac

cycle

is

the

sequence

of

events

in

one

heartbeat.

In

its

simplest

form,

the

cardiac

cycle

is

the

simultaneous

contraction

of

the

two

atria,

followed

a

fraction

of

a

second

later

by

the

simultaneous

contraction

of

the

two

ventricles.

There

is,

however,

a

significant

difference

between

the

movement

of

blood

from

the

atria

to

the

ventricles,

and

the

movement

of

blood

from

the

ventricles

to

the

arteries.2.血液不間斷地從靜脈流入兩個心房。

隨著大量的血液積聚,

血液的壓力會打開左右房室瓣。兩個心房里三分之二的血液被動地流入到心室中;

然后，心房收縮將剩余血液泵入心室。Blood

is

constantly

flowing

from

the

veins

into

both

atria.

As

more

blood

accumulates,

its

pressure

forces

open

the

right

and

left

AV

valves.

Two

thirds

of

the

atrial

blood

flows

passively

into

the

ventricles;

the

atria

then

contract

to

pump

the

remaining

blood

into

the

ventricles.3.心房收縮后舒張，心室開始收縮。心室的收縮使血液施壓于左右房室瓣的皮瓣并使其閉合;

同時，血液之力也打開了動脈和肺的半月瓣。隨著心室的繼續(xù)收縮,

它們把血液射入動脈。注意，進(jìn)入動脈的血液必須被全部泵出。然后心室舒張,

同時血液繼續(xù)流入心房，循環(huán)重新開始。Following

their

contraction,

the

atria

relax

and

the

ventricles

begin

to

contract.

Ventricular

contraction

forces

blood

against

the

flaps

of

the

right

and

left

AV

valves

and

closes

them;

the

force

of

blood

also

opens

the

aortic

and

pulmonary

semilunar

valves.

As

the

ventricles

continue

to

contract,

they

pump

blood

into

the

arteries.

The

blood

that

enters

the

arteries

must

all

be

pumped.

The

ventricles

then

relax,

and

at

the

same

time

blood

continues

to

flow

into

the

atria,

and

the

cycle

will

begin

again.4.

這里一個重要的不同點(diǎn)就是大部分血液是被動地從心房流入心室,但是所有注入動脈的血液均由心室主動射出。

因此,

對生存來說，心室的正常工作遠(yuǎn)比心房的工作重要的多。The

important

distinction

here

is

that

most

blood

flows

passively

from

atria

to

ventricles,

but

all

blood

to

the

arteries

is

actively

pumped

by

the

ventricles.

For

this

reason,

the

proper

functioning

of

the

ventricles

is

much

more

crucial

to

survival

than

is

atrial

functioning.5.收縮的另一個術(shù)語是心臟收縮。松弛的術(shù)語是心臟舒張。您可能比較熟悉這些術(shù)語，因?yàn)樗鼈兣c血壓讀數(shù)相關(guān)。如果我們把這些術(shù)語應(yīng)用到心臟血液循環(huán)中，我們就可以這樣說,

心室收縮緊隨心房收縮之后。換句話說，就是當(dāng)心房收縮時,

心室舒張,

當(dāng)心室收縮時,

心房舒張。There

is

another

term

for

contraction,

and

that

is

systole.

The

term

for

relaxation

is

diastole.

You

are

probably

familiar

with

these

terms

as

they

relate

to

blood

pressure

readings.

If

we

apply

them

to

the

cardiac

cycle,

we

can

say

that

atrial

systole

is

followed

by

ventricular

systole.

Another

way

to

put

it

is

that

when

the

atria

are

in

systole,

the

ventricles

are

in

diastole,

and

when

the

ventricles

are

in

systole,

the

atria

are

in

diastole.6.您也許會問:

所有這些都發(fā)生在一次心跳中嗎?

答案是肯定的。心臟血液循環(huán)就是由這一系列精確的活動組成，這些活動使血液從靜脈流過心臟最后再注入動脈。You

may

be

asking:

all

this

in

one

heartbeat?

The

answer

is

yes.

The

cardiac

cycle

is

this

precise

sequence

of

events

that

keeps

blood

moving

from

the

veins,

through

the

heart

and

into

the

arteries.7.心臟血液循環(huán)同時產(chǎn)生心音:

每一次心跳會有兩個聲音，用聽診器可以聽見。第一聲,

最大也最長,

是由心室收縮閉合房室瓣而引起的。第二聲是由動脈和肺的半月瓣的閉合造成的。如果任一瓣膜閉合不全,

就會聽見另外一個聲音，稱為―心臟雜音‖。The

cardiac

cycle

also

creates

the

heart

sounds:

each

heartbeat

produces

two

sounds,

which

can

be

heard

with

a

stethoscope.

The

first

sound,

the

loudest

and

longest,

is

caused

by

ventricular

systole

closing

the

AV

valves.

The

second

sound

is

caused

by

the

closure

of

the

aortic

and

pulmonary

semi-lunar

valves.

If

any

of

the

valves

do

not

close

properly,

an

extra

sound

called

a

heart

murmur

may

be

heard.

心臟的傳導(dǎo)途徑8.心臟血液循環(huán)的一系列機(jī)械活動是由心肌的電活動調(diào)控。心肌細(xì)胞會自發(fā)收縮，即收縮并非由神經(jīng)脈沖引起。心臟自行跳動，腦電脈沖沿一確定路徑穿過心肌層。The

cardiac

cycle

is

a

sequence

of

mechanical

events

that

is

regulated

by

the

electrical

activity

of

the

myocardium.

Cardiac

muscle

cells

have

the

ability

to

contract

spontaneously,

that

is,

nerve

impulses

are

not

required

to

cause

contraction.

The

heart

generates

its

own

beat,

and

the

electrical

impulses

follow

a

very

specific

route

throughout

the

myocardium.9.心臟的自然起搏器是竇房結(jié)，它是位于右心房壁上的特化心肌細(xì)胞群。竇房結(jié)被認(rèn)為是特化的是因?yàn)樗凶羁斓氖湛s速度。The

natural

pacemaker

of

the

heart

is

the

sinoatrial

(SA)

node,

a

specialized

group

of

cardiac

muscle

cells

located

in

the

wall

of

the

right

atrium.

The

SA

node

is

considered

specialized

because

it

has

the

most

rapid

rate

of

contraction,

that

is,

it

depolarizes

more

rapidly

than

any

other

part

of

the

myocardium.10.收縮脈沖從竇房結(jié)運(yùn)行到房室結(jié)，房室結(jié)位于心房間隔膜區(qū)下部。從竇房結(jié)和房室結(jié)到心房心肌層的其余部分的脈沖傳導(dǎo)可引起心房收縮。From

the

SA

node,

impulses

for

contraction

travel

to

the

atrioventricular

(AV)

node,

located

in

the

lower

interatrial

septum.

The

transmission

of

impulses

from

the

SA

node

and

AV

node

to

the

rest

of

the

atrial

myocardium

brings

about

atrial

systole.11.心室間的上層隔膜內(nèi)是希斯束,

它接收來自房室結(jié)的脈沖，并傳給左右神經(jīng)束支。脈沖從神經(jīng)束支開始，沿著普肯野纖維到達(dá)心室心肌層的其他部分,

并引起心室收縮。心電圖可以顯示心房和心室的電子活動。

Within

the

upper

interventricular

septum

is

the

Bundle

of

His

(AV

bundle),

which

receives

impulses

from

the

AV

node

and

transmits

them

to

the

right

and

left

bundle

branches.

From

the

bundle

branches,

impulses

travel

along

Purkinje

fibers

to

the

rest

of

the

ventricular

myocardium,

and

bring

about

ventricular

systole.

The

electrical

activity

of

the

atria

and

ventricles

is

depicted

by

an

electrocardiogram

(ECG)12.如果竇房結(jié)活動不正常,

房室結(jié)將啟始心跳,

但速度較慢(每分鐘50到60下)。希斯束也能引起心室跳動,

但是速度會慢地多(每分鐘15到40下)。這種情形會出現(xiàn)在某些心臟病中，是由心房到心室的脈沖傳導(dǎo)被阻礙而引發(fā)的。

If

the

SA

node

does

not

function

properly,

the

AV

node

will

initiate

the

heartbeat,

but

at

a

slower

rate

(50

to

60

beats

per

minute).

The

Bundle

of

His

is

also

capable

of

generating

the

beat

of

the

ventricles,

but

at

a

much

slower

rate

(15

to

40

beats

per

minute).

This

may

occur

in

certain13.心率失常是不規(guī)則的心跳;

它們的影響范圍小到對人體無害大到威及生命。幾乎每個人不時都會感受心悸。這些通常都不太嚴(yán)重,

而且可能是因?yàn)檫^多攝入了咖啡因,

尼古丁或酒精造成的。然而嚴(yán)重的是心室纖維顫動,

是一種非常迅速的、不協(xié)調(diào)的、完全無法泵出血液的心室悸實(shí)Arrhythmias

are

irregular

heartbeats;

their

effects

range

from

harmless

to

life-threatening.

Nearly

everyone

experiences

heart

palpitations

from

time

to

time.

These

are

usually

not

serious,

and

may

be

the

result

of

too

much

caffeine,

nicotine,

or

alcohol.

Much

more

serious

is

ventricular

fibrillation,

a

very

rapid

and

uncoordinated

ventricular

beat

that

is

totally

ineffective

for

pumping

blood.心率14.一個健康的成年人安靜時的心跳一般在每分鐘60至80下，是竇房結(jié)去極化的速度。一個小孩正常心跳為每分鐘100下，一個剛出生的嬰兒的心跳多達(dá)每分鐘120下；一個快要出生的胎兒的心跳則在每分鐘140下左右。這些較快的心率與年齡無關(guān)，與體型則關(guān)系密切：體型越小，新陳代謝的速率就會越快，同樣心率也會越高。這樣的例子可以從不同體形的動物得到啟示：老鼠的心率在每分鐘200次左右，而大象的心率在每分鐘30次左右。

A

healthy

adult

has

a

resting

heart

rate

(pulse)

of

60

to

80beats

per

minute,

which

is

the

rate

of

depolarization

of

the

SA

node.

A

child’s

normal

heart

rate

may

be

as

high

as

100

beats

per

minute,

that

of

an

infant

as

high

as

120,

and

that

of

a

near-term

fetus

as

high

as

140

beats

per

minute.

These

higher

rates

are

not

related

to

age,

but

rather

to

size:

the

smaller

the

individual,

the

higher

the

metabolic

rate

and

the

faster

the

heart

rate.Parallels

may

be

found

among

animals

of

different

sizes;

the

heart

ra

te

of

a

mouse

is

about

200

beats

per

minute,

and

that

of

an

elephant

about

30

beats

per

minute.15.讓我們回到成人心率這個問題上來，設(shè)定一個人擁有良好的健康狀況。正如你所知，一個身體狀態(tài)良好的運(yùn)動員的心率較低。那些籃球運(yùn)動員的脈搏在每分鐘50次左右，馬拉松運(yùn)動員的脈搏在每分鐘35到40次。要搞清楚這一點(diǎn)，首先要記住心臟是一個肌性器官。當(dāng)我們充分鍛煉我們骨骼肌的時候，它們變得更加強(qiáng)壯、高效。這點(diǎn)同樣適用于我們的心臟：持續(xù)的運(yùn)動使得心臟泵血更加有力。心輸出量Let

us

return

to

the

adult

heart

rate,

and

consider

the

person

who

is

in

excellent

physical

condition.

As

you

may

know,

well-conditioned

athletes

have

low

resting

pulse

rates.Those

of

basketball

players

are

often

around

50

beats

per

minute,

and

the

pulse

of

a

marathon

runner

often

ranges

from

35

to

40

beats

per

minute.

To

understand

why

this

is

so,

remember

that

the

heart

is

a

muscle.When

our

skeletal

muscles

are

exercised,

they

become

stronger

and

more

efficient.

The

same

is

true

for

the

heart;

consistent

exercise

makes

it

a

more

efficient

pump,

as

you

will

see

in

the

next

discussion.16.

心輸出量是指每分鐘心室泵出的血液量。我們的身體時刻需要一定量的心臟供血，將氧氣輸送到身體的各個組織，同時清除身體產(chǎn)生的廢物。在鍛煉過程中，心臟供血量增加，以滿足身體對氧氣的需求。討論過靜息狀態(tài)下的心輸出量以后，我們再回到運(yùn)動時心輸出量這個話題上來。Cardiac

output

is

the

amount

of

blood

pumped

by

a

ventricle

in

one

minute.

A

certain

level

of

cardiac

output

is

needed

at

all

times

to

transport

oxygen

to

tissues

and

to

remove

waste

products.

During

exercise,

cardiac

output

must

increase

to

meet

the

body’s

need

for

more

oxygen.

We

will

return

to

exercise

after

first

considering

resting

cardiac

output.17.為了計算心輸出量，我們必須知道心率和每次心跳所泵出的血液量。心臟供血量這一術(shù)語是指心室每次跳動所泵出的血液量。人在靜息狀態(tài)下，每次心跳的供血量均在60到80毫升。下面這個簡單的公式能使我們很容易計算出心輸出量：

In

order

to

calculate

cardiac

output,

we

must

know

the

pulse

rate

and

how

much

blood

is

pumped

per

beat.

Stroke

volume

is

the

term

for

the

amount

of

blood

pumped

by

a

ventricle

per

beat;

an

average

resting

stroke

volume

is

60

to

80

ml

per

beat.

A

simple

formula

then

enables

us

to

determine

cardiac

output:Cardiac

output

＝Stroke

volume

×

pulse

(heart

rate)18.我們假定人安靜時的心室跳動一次的供血量為70毫升，其心率為每分鐘70次：

心輸出量＝

70ml

×

70

bpm（每分鐘脈搏次數(shù)）

心輸出量＝4900

ml/m

(大約5

L)Let

us

put

into

this

formula

an

average

resting

stroke

volume,

70

ml,

and

an

average

resting

pulse,

70

beats

per

minute

(bpm):

Cardiac

output

＝

70

ml

×

70

bpm

Cardiac

output

＝

4,900

ml

per

minute

(approximately

5

liters)19.當(dāng)然心輸出量的多少會隨著人體型的大小而變，但人在靜息狀態(tài)下的心輸出量是每分56升。

Naturally,

cardiac

output

varies

with

the

size

of

the

person,

but

the

average

resting

cardiac

output

is

5

to

6

liters

per

minute.20.現(xiàn)在我們再看一下運(yùn)動員,

我們就可以清楚地知道為什么運(yùn)動員在靜息狀態(tài)下，心率較常人低。我們假定人在靜息狀態(tài)下的心臟供血量為每分鐘5

L，運(yùn)動員心率為每分鐘50次：

心輸出量＝每博量×心率

5,000/50＝每搏量

100

ml＝每搏量If

we

now

reconsider

the

athlete,

you

will

be

able

to

see

precisely

why

the

athlete

has

a

low

resting

pulse.

In

our

formula,

we

will

use

an

average

resting

cardiac

output

(5

liters)

and

an

athlete’s

pulse

rate

(50):Cardiac

Output

＝Stroke

volume

×

pulse

5,000/50＝Stroke

volume

100

ml＝Stroke

volume21.我們注意到靜息狀態(tài)下運(yùn)動員的心臟供血量明顯高于常人。運(yùn)動員的強(qiáng)有力的心臟每次跳動能為身體提供更多血液。因此，靜息狀態(tài)下他們保持一個較低的心率。

Notice

that

the

athlete’s

resting

stroke

volume

is

significantly

higher

than

the

average.

The

athlete’s

more

efficient

heart

pumps

more

blood

with

each

beat,

and

so

can

maintain

a

normal

resting

cardiac

output

with

fewer

beats.22.現(xiàn)在我們再考慮一下心臟對運(yùn)動作何反映。人在運(yùn)動的過程中心率會加快，心輸出量也會相應(yīng)增加。心輸出量的增加是斯塔林心臟定律的結(jié)果，定律指出心肌纖維越伸展，它們的收縮越強(qiáng)。運(yùn)動過程中，更多的血液通過靜脈回流的方式回到心臟。靜脈回流量的增加就會促使心肌層的伸展，這樣心室收縮有力，泵出更多的血液，增加心臟供血量。因此，運(yùn)動時，心臟供血量的計算公式如下：kinds

of

heart

disease

in

which

transmission

of

impulses

from

the

atria

to

the

ventricles

is

blocked.

心輸出量＝每搏量×心率

心輸出量＝

100

ml

×100

bpm

心輸出量＝10,000

ml

(10

liters)

Now

let

us

see

how

the

heart

responds

to

exercise.

Heart

rate(pulse)

increases

during

exercise,

and

so

does

stroke

volume.

The

increase

in

stroke

volume

is

the

result

of

Starling’s

Law

of

the

Heart,

which

states

that

the

more

the

cardiac

muscle

fibers

are

stretched,

the

more

forcefully

they

contract.

During

exercise,

more

blood

returns

to

the

heart;

this

is

called

venous

return.

Increased

venous

return

stretches

the

myocardium

of

the

ventricles,

which

contract

more

forcefully

and

pump

more

blood,

thereby

increasing

stroke

volume.

Therefore,

during

exercise,

our

formula

might

be

the

following:

Cardiac

output

＝Stroke

volume×

pulse

Cardiac

output

＝100

ml

×

100

bpm

Cardiac

output

＝

10,000ml(10

liters)23.運(yùn)動時心輸出量幾乎是前面我們計算的靜息狀態(tài)下的兩倍，而這并非異常。劇烈運(yùn)動時，一個健康年輕人每分鐘的心輸出量可以增加到他安靜時的４倍；一個馬拉松運(yùn)動員的心輸出量可以達(dá)到他安靜時的６倍甚至更多；這是因?yàn)轳R拉松運(yùn)動員擁有強(qiáng)有力的心臟。This

exercise

cardiac

output

is

twice

the

resting

cardiac

output

we

first

calculated,

which

should

not

be

considered

unusual.

The

cardiac

output

of

a

healthy

young

person

may

increase

up

to

four

times

the

resting

level

during

strenuous

exercise.

This

exercise

cardiac

output

is

twice

the

resting

cardiac

output

we

first

calculated,

which

should

not

be

considered

unusual.

The

cardiac

output

of

a

healthy

young

person

may

increase

up

to

four

times

the

resting

level

during

strenuous

exercise.心率的調(diào)節(jié)24.雖然心臟自行跳動并保持其跳動，但心臟收縮的頻率可根據(jù)情況的不同而發(fā)生變化。神經(jīng)系統(tǒng)可以調(diào)節(jié)心臟收縮的力度并控制心率的必要變化。

Although

the

heart

generates

and

maintains

its

own

beat,

the

rate

of

contraction

can

be

changed

to

adapt

to

different

situations.

The

nervous

system

can

and

does

bring

about

necessary

changes

in

heart

rate

as

well

as

in

force

of

contraction.25.腦髓質(zhì)有兩個心血管控制中心：加速中樞和抑制中樞。兩中樞通過自主神經(jīng)向心臟傳送神經(jīng)脈沖。自主神經(jīng)系統(tǒng)可以分為交感神經(jīng)和副交感神經(jīng)兩大股。加速中樞產(chǎn)生的交感脈沖通過交感神經(jīng)傳輸?shù)叫呐K，加快心臟的跳動速率和收縮力度。抑制中樞產(chǎn)生的副交感脈沖通過迷走神經(jīng)傳輸?shù)叫呐K，降低心臟跳動的速率。The

medulla

of

the

brain

contains

the

two

cardiac

centers,

the

accelerator

center

and

the

inhibitory

center.

These

centers

send

impulses

to

the

heart

along

autonomic

nerves.

The

autonomic

nervous

system

has

two

divisions:

sympathetic

and

parasympathetic.

Sympathetic

impulses

from

the

accelerator

center

along

sympathetic

nerves

increase

heart

rate

and

force

of

contraction.

Parasympathetic

impulses

from

the

inhibitory

center

along

the

vagus

nerves

decrease

the

heart

rate.26.我們下一個問題是腦髓質(zhì)接受了什么信息才引起這些變化呢？既然心臟泵出血液，維持血壓正常就很重要了。血液含氧氣，身體各組織必須不停地獲得這種含氧血。因此，血壓和血液中含氧量的變化就會刺激心率產(chǎn)生相應(yīng)的變化。Our

next

question

might

be:

what

information

is

received

by

the

medulla

to

initiate

changes?

Since

the

heart

pumps

blood,

it

is

essential

to

maintain

normal

blood

pressure.

Blood

contains

oxygen,

which

all

tissues

must

receive

continuously.

Therefore,

changes

in

blood

pressure

and

oxygen

level

of

the

blood

are

stimuli

for

changes

in

heart

rate.心輸出量＝每搏量×心率

心輸出量＝

100

ml

×100

bpm

心輸出量＝10,000

ml

(10

liters)

Now

let

us

see

how

the

heart

responds

to

exercise.

Heart

rate(pulse)

increases

during

exercise,

and

so

does

stroke

volume.

The

increase

in

stroke

volume

is

the

result

of

Starling’s

Law

of

the

Heart,

which

states

that

the

more

the

cardiac

muscle

fibers

are

stretched,

the

more

forcefully

they

contract.

During

exercise,

more

blood

returns

to

the

heart;

this

is

called

venous

return.

Increased

venous

return

stretches

the

myocardium

of

the

ventricles,

which

contract

more

forcefully

and

pump

more

blood,

thereby

increasing

stroke

volume.

Therefore,

during

exercise,

our

formula

might

be

the

following:

Cardiac

output

＝Stroke

volume×

pulse

Cardiac

output

＝100

ml

×

100

bpm

Cardiac

output

＝

10,000ml(10

liters)23.運(yùn)動時心輸出量幾乎是前面我們計算的靜息狀態(tài)下的兩倍，而這并非異常。劇烈運(yùn)動時，一個健康年輕人每分鐘的心輸出量可以增加到他安靜時的４倍；一個馬拉松運(yùn)動員的心輸出量可以達(dá)到他安靜時的６倍甚至更多；這是因?yàn)轳R拉松運(yùn)動員擁有強(qiáng)有力的心臟。This

exercise

cardiac

output

is

twice

the

resting

cardiac

output

we

first

calculated,

which

should

not

be

considered

unusual.

The

cardiac

output

of

a

healthy

young

person

may

increase

up

to

four

times

the

resting

level

during

strenuous

exercise.

This

exercise

cardiac

output

is

twice

the

resting

cardiac

output

we

first

calculated,

which

should

not

be

considered

unusual.

The

cardiac

output

of

a

healthy

young

person

may

increase

up

to

four

times

the

resting

level

during

strenuous

exercise.心率的調(diào)節(jié)24.雖然心臟自行跳動并保持其跳動，但心臟收縮的頻率可根據(jù)情況的不同而發(fā)生變化。神經(jīng)系統(tǒng)可以調(diào)節(jié)心臟收縮的力度并控制心率的必要變化。

Although

the

heart

generates

and

maintains

its

own

beat,

the

rate

of

contraction

can

be

changed

to

adapt

to

different

situations.

The

nervous

system

can

and

does

bring

about

necessary

changes

in

heart

rate

as

well

as

in

force

of

contraction.25.腦髓質(zhì)有兩個心血管控制中心：加速中樞和抑制中樞。兩中樞通過自主神經(jīng)向心臟傳送神經(jīng)脈沖。自主神經(jīng)系統(tǒng)可以分為交感神經(jīng)和副交感神經(jīng)兩大股。加速中樞產(chǎn)生的交感脈沖通過交感神經(jīng)傳輸?shù)叫呐K，加快心臟的跳動速率和收縮力度。抑制中樞產(chǎn)生的副交感脈沖通過迷走神經(jīng)傳輸?shù)叫呐K，降低心臟跳動的速率。The

medulla

of

the

brain

contains

the

two

cardiac

centers,

the

accelerator

center

and

the

inhibitory

center.

These

centers

send

impulses

to

the

heart

along

autonomic

nerves.

The

autonomic

nervous

system

has

two

divisions:

sympathetic

and

parasympathetic.

Sympathetic

impulses

from

the

accelerator

center

along

sympathetic

nerves

increase

heart

rate

and

force

of

contraction.

Parasympathetic

impulses

from

the

inhibitory

center

along

the

vagus

nerves

decrease

the

heart

rate.26.我們下一個問題是腦髓質(zhì)接受了什么信息才引起這些變化呢？既然心臟泵出血液，維持血壓正常就很重要了。血液含氧氣，身體各組織必須不停地獲得這種含氧血。因此，血壓和血液中含氧量的變化就會刺激心率產(chǎn)生相應(yīng)化。Our

next

question

might

be:

what

information

is

received

by

the

medulla

to

initiate

changes?

Since

the

heart

pumps

blood,

it

is

essential

to

maintain

normal

blood

pressure.

Blood

contains

oxygen,

which

all

tissues

must

receive

continuously.

Therefore,

changes

in

blood

pressure

and

oxygen

level

of

the

blood

are

stimuli

for

changes

in

heart

rate.27.壓力感受器和化學(xué)受體位于頸動脈和主動脈弓。位于頸動脈竇和主動脈竇的壓力感受器可檢測血壓的變化。位于頸動脈體和主動脈體內(nèi)的化學(xué)受體可檢測血液中含氧量的變化。頸動脈受體的感覺神經(jīng)是舌咽神經(jīng)；主動脈弓受體的感覺神經(jīng)是迷走神經(jīng)。如果我們把上面這些事實(shí)集中在一個特例中，我們就可以看出心臟調(diào)節(jié)是一種反射。Pressoreceptors

and

chemoreceptors

are

located

in

the

carotid

arteries

and

aortic

arch.

ors

in

the

carotid

sinuses

and

aortic

sinus

detect

changes

in

blood

pressure.

Chemoreceptors

in

the

carotid

bodies

and

aortic

body

detect

changes

in

the

oxygen

content

of

the

blood.

The

sensory

nerves

for

the

carotid

receptors

are

the

glossopharyngeal

nerves;

the

sensory

nerves

for

aortic

arch

receptors

are

the

vagus

nerves.

If

we

now

put

all

these

facts

together

in

a

specific

example,

you

will

see

that

the

regulation

of

heart

rate

is

a

reflex.28.一個處于臥位的人突然變?yōu)檎疚?，或許會感到一陣稍微的頭暈，這是因?yàn)槟X部血壓突降的緣故。位于頸動脈竇的壓力感受器可測得這種血壓的降低——注意這些感受器處于到達(dá)大腦的―途中‖，一個關(guān)鍵部位。壓力感受器發(fā)出的脈沖沿舌咽神經(jīng)到達(dá)腦髓質(zhì)，刺激加速中樞。加速中樞生成的脈沖通過交感神經(jīng)到達(dá)竇房結(jié)、房室結(jié)和心室的心肌層。隨著心率和心臟跳動的力度增強(qiáng)，到達(dá)大腦的血壓升高到正常水平，頭暈癥狀消失。當(dāng)?shù)竭_(dá)大腦的血壓恢復(fù)正常后，心臟接收來自抑制中樞的副交感神經(jīng)脈沖，它們沿迷走神經(jīng)到達(dá)竇房結(jié)和房室結(jié)。這些副交感神經(jīng)脈沖減緩心率至正常休息頻率。A

person

who

stands

up

suddenly

from

a

lying

position

may

feel

light-headed

or

dizzy

for

a

few

moments,

because

blood

pressure

to

the

brain

has

decreased

abruptly.

The

drop

in

blood

pressure

is

detected

by

pressoreceptors

in

the

carotid

sinuses—

notice

that

they

are

“on

the

way”

to

the

brain,

a

very

strategic

location.

Impulses

generated

by