托福紅DeltaTest1聽力Heartbeat

托福紅DeltaTest1聽力Heartbeat，接下來就跟著中國(guó)教育在線的小編詳細(xì)了解一下吧。

Heartbeat托福聽力原文翻譯及問題答案

一、Heartbeat托福聽力原文：

Every minute of every day，blood flows through every corner of your body.The flow of blood brings oxygen and other nutrients to your tissues.Then it loads up the waste products of your metabolism and carries them away.This system of nutrient exchange is what keeps your organs and tissues alive.It’s made possible only because of the steady beating of your heart—the driving force of your circulatory system.

How can your heart keep beating and beating，never stopping，and rarely getting out of sync?It’s possible because of the specialized type of muscle—cardiac muscle—that makes up the heart tissue，and also because of the action of specialized electrical pathways that run through the heart’s walls.

Before I go into cardiac muscle，let’s back up a bit.You may recall from last time that the action of a muscle is always to contract.Muscles can extend only passively.They extend as they relax between contractions.You’ll also recall that the human body has different types of muscles.For example，skeletal muscle controls body movements，and cardiac muscle controls the body’s blood flow.Skeletal muscle is found throughout the body，but cardiac muscle is found only in one place—the heart.

Skeletal muscles get their name from the fact that their movement is based on the contraction of muscles working against the skeleton.Skeletal muscles are attached to the bones，and they move the bones by contracting.

A skeletal muscle consists of a bundle of long fibers running the length of the muscle.The bundles of fibers are arranged in a regular pattern—a repeating pattern of light and dark bands.This pattern is called striation，and skeletal muscle is also known as striated muscle.When a muscle contracts，the length of each bundle is reduced.A skeletal muscle contracts only when it’s stimulated by a motor neuron.

Cardiac muscle，on the other hand，contracts rhythmically all on its own.Cardiac muscle cells can generate impulses on their own，without any input from the nervous system.They can do this because of complex chemical and electrical changes involving sodium，calcium，and potassium，each of which carries an electrical charge.

Like skeletal muscle，cardiac muscle is striated.However，the membranes between cardiac muscle cells contain specialized regions that provide direct electrical contact among cells.What this means is，an electrical impulse generated in one part of the heart will spread to all the cardiac muscle cells.Thus，the whole heart will contract.Cardiac muscle cells can generate impulses without any input from the nervous system.In contrast to this，skeletal muscles don’t contract unless the nervous system tells them to.

A single cardiac muscle cell will“beat”even when it’s isolated from the heart and placed in cell culture in the laboratory.If you removed a little piece of muscle from your heart and put it in a dish，you would see it continue to contract.That’s because cardiac muscle cells have something called an action potential.Electrically，they’re set up so，so that sodium and calcium—positive ions—change places with potassium—a negative ion—across the cell membrane.This happens automatically，over and over again.When sodium，calcium，and potassium ions move into or out of a cardiac cell，it causes the muscle to contract.

What we think of as a heartbeat is really a series of contractions in the cardiac muscle.When the heart’s walls contract，they force blood out of the chambers and into the next chamber or the large blood vessels that lead to the rest of your body.Every day，your heart contracts 100，000 times or more，pumping more than 2，000 gallons of blood.

But，unlike the skeletal muscles in your body，your cardiac muscle can never stop and take a rest.If your heart stops beating，you have very little time—only a matter of minutes—for it to start up again before your other body systems are permanently damaged or stop functioning altogether.

二、Heartbeat托福聽力中文翻譯：

每天的每一分鐘，血液都流經(jīng)你身體的每一個(gè)角落。血液的流動(dòng)給你的組織帶來氧氣和其他營(yíng)養(yǎng)物質(zhì)。然后它裝載你新陳代謝的廢物并將它們帶走。這種營(yíng)養(yǎng)交換系統(tǒng)使你的器官和組織保持活力。它之所以成為可能，是因?yàn)樾呐K的穩(wěn)定跳動(dòng)是循環(huán)系統(tǒng)的驅(qū)動(dòng)力。

你的心臟怎么能不停地跳動(dòng)、不停地跳，而且很少失去同步？這是可能的，因?yàn)闃?gòu)成心臟組織的特殊類型的肌肉-心肌，也因?yàn)榇┻^心臟壁的特殊電通路的作用。

在我進(jìn)入心肌之前，讓我們后退一點(diǎn)。你可能還記得上次肌肉的動(dòng)作總是收縮的。肌肉只能被動(dòng)伸展。它們?cè)谑湛s之間放松時(shí)伸展。你還會(huì)記得，人體有不同類型的肌肉。例如，骨骼肌控制身體運(yùn)動(dòng)，而心肌控制身體的血流。骨骼肌遍布全身，但心肌只存在于心臟的一個(gè)部位。

骨骼肌之所以得名，是因?yàn)樗鼈兊倪\(yùn)動(dòng)是基于肌肉對(duì)骨骼的收縮。骨骼肌肉附著在骨骼上，它們通過收縮來移動(dòng)骨骼。

骨骼肌由一束沿著肌肉長(zhǎng)度延伸的長(zhǎng)纖維組成。纖維束以規(guī)則的圖案排列，這是一種由亮帶和暗帶組成的重復(fù)圖案。這種模式稱為橫紋肌，骨骼肌也被稱為橫紋肌。當(dāng)肌肉收縮時(shí)，每束肌肉的長(zhǎng)度都會(huì)縮短。骨骼肌只有在運(yùn)動(dòng)神經(jīng)元的刺激下才會(huì)收縮。

另一方面，心臟肌肉完全自行有節(jié)奏地收縮。心肌細(xì)胞可以自行產(chǎn)生脈沖，而無需來自神經(jīng)系統(tǒng)的任何輸入。它們之所以能做到這一點(diǎn)，是因?yàn)殁c、鈣和鉀的復(fù)雜化學(xué)和電變化，每一種都帶有電荷。

和骨骼肌一樣，心肌也有條紋。然而，心肌細(xì)胞之間的膜包含提供細(xì)胞間直接電接觸的特殊區(qū)域。這意味著，心臟一部分產(chǎn)生的電脈沖將傳播到所有心肌細(xì)胞。因此，整個(gè)心臟都會(huì)收縮。心肌細(xì)胞可以在沒有神經(jīng)系統(tǒng)輸入的情況下產(chǎn)生脈沖。與此相反，骨骼肌不收縮，除非神經(jīng)系統(tǒng)告訴他們收縮。

即使將單個(gè)心肌細(xì)胞從心臟中分離出來并置于實(shí)驗(yàn)室的細(xì)胞培養(yǎng)中，它也會(huì)“跳動(dòng)”。如果你從心臟中取出一小塊肌肉，放在盤子里，你會(huì)看到它繼續(xù)收縮。這是因?yàn)樾募〖?xì)胞有一種叫做動(dòng)作電位的東西。在電氣上，它們是這樣設(shè)置的，所以鈉和鈣的正離子與鉀（一種穿過細(xì)胞膜的負(fù)離子）交換位置。這是自動(dòng)發(fā)生的，一次又一次。當(dāng)鈉、鈣和鉀離子移入或移出心臟細(xì)胞時(shí)，會(huì)導(dǎo)致肌肉收縮。

我們所認(rèn)為的心跳實(shí)際上是心肌的一系列收縮。當(dāng)心臟壁收縮時(shí)，它們迫使血液流出心室，進(jìn)入下一個(gè)心室或通向身體其他部分的大血管。每天，你的心臟收縮10萬次或更多，泵出超過2000加侖的血液。

但是，與你身體中的骨骼肌不同，你的心臟肌肉永遠(yuǎn)不會(huì)停止和休息。如果你的心臟停止跳動(dòng)，那么在你的其他身體系統(tǒng)永久受損或完全停止運(yùn)轉(zhuǎn)之前，你只有很少的時(shí)間重新啟動(dòng)，只有幾分鐘的時(shí)間。

三、Heartbeat托福聽力問題：

Q1:How does the professor develop the topic of cardiac muscle?

A.By describing evolutionary changes in cardiac muscle

B.By classifying the types of muscle in the body

C.By explaining what happens if the heart stops beating

D.By comparing cardiac muscle and skeletal muscle

Q2:Why does the professor say this:

A.To introduce the topic of cardiac muscle

B.To find out how much the students already know

C.To tell the students what will be on the next test

D.To point out a question that has no clear answer

Q3:Why does the professor say this:

A.To correct one of her previous statements

B.To make sure the students are paying attention

C.To review material the class has already studied

D.To give the students time to write down what she says

Q4:Based on the information in the lecture，indicate whether each sentence below describes skeletal muscle or cardiac muscle.For each sentence，click in the correct box.

Q5:What happens when an electrical impulse generated in one part of the heart spreads to all the cardiac muscle cells?

A.The impulse spreads to the bones.

B.The cardiac muscles extend.

C.The heart beats faster.

D.The whole heart contracts.

Q6:What can be inferred about the contraction of cardiac muscle?

A.Cardiac muscle contracts automatically because it contains motor neurons.

B.The contraction depends on the action of sodium，calcium，and potassium.

C.The nervous system tells cardiac muscle cells when to contract.

D.Cardiac muscle cells will live for several weeks in a laboratory dish

四、Heartbeat托福聽力答案：

A1:正確答案：D

A2:正確答案：A

A3:正確答案：C

A4:正確答案：ABABB

A5:正確答案：D

A6:正確答案：D

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