托福红DeltaTest1听力Heartbeat

2023-06-21 10:19:14 来源：中国教育在线

托福红DeltaTest1听力Heartbeat，接下来就跟着中国教育在线的小编详细了解一下吧。

Heartbeat托福听力原文翻译及问题答案

一、Heartbeat托福听力原文：

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托福听力中文翻译：

每天的每一分钟，血液都流经你身体的每一个角落。血液的流动给你的组织带来氧气和其他营养物质。然后它装载你新陈代谢的废物并将它们带走。这种营养交换系统使你的器官和组织保持活力。它之所以成为可能，是因为心脏的稳定跳动是循环系统的驱动力。

你的心脏怎么能不停地跳动、不停地跳，而且很少失去同步？这是可能的，因为构成心脏组织的特殊类型的肌肉-心肌，也因为穿过心脏壁的特殊电通路的作用。

在我进入心肌之前，让我们后退一点。你可能还记得上次肌肉的动作总是收缩的。肌肉只能被动伸展。它们在收缩之间放松时伸展。你还会记得，人体有不同类型的肌肉。例如，骨骼肌控制身体运动，而心肌控制身体的血流。骨骼肌遍布全身，但心肌只存在于心脏的一个部位。

骨骼肌之所以得名，是因为它们的运动是基于肌肉对骨骼的收缩。骨骼肌肉附着在骨骼上，它们通过收缩来移动骨骼。

骨骼肌由一束沿着肌肉长度延伸的长纤维组成。纤维束以规则的图案排列，这是一种由亮带和暗带组成的重复图案。这种模式称为横纹肌，骨骼肌也被称为横纹肌。当肌肉收缩时，每束肌肉的长度都会缩短。骨骼肌只有在运动神经元的刺激下才会收缩。

另一方面，心脏肌肉完全自行有节奏地收缩。心肌细胞可以自行产生脉冲，而无需来自神经系统的任何输入。它们之所以能做到这一点，是因为钠、钙和钾的复杂化学和电变化，每一种都带有电荷。

和骨骼肌一样，心肌也有条纹。然而，心肌细胞之间的膜包含提供细胞间直接电接触的特殊区域。这意味着，心脏一部分产生的电脉冲将传播到所有心肌细胞。因此，整个心脏都会收缩。心肌细胞可以在没有神经系统输入的情况下产生脉冲。与此相反，骨骼肌不收缩，除非神经系统告诉他们收缩。

即使将单个心肌细胞从心脏中分离出来并置于实验室的细胞培养中，它也会“跳动”。如果你从心脏中取出一小块肌肉，放在盘子里，你会看到它继续收缩。这是因为心肌细胞有一种叫做动作电位的东西。在电气上，它们是这样设置的，所以钠和钙的正离子与钾（一种穿过细胞膜的负离子）交换位置。这是自动发生的，一次又一次。当钠、钙和钾离子移入或移出心脏细胞时，会导致肌肉收缩。

我们所认为的心跳实际上是心肌的一系列收缩。当心脏壁收缩时，它们迫使血液流出心室，进入下一个心室或通向身体其他部分的大血管。每天，你的心脏收缩10万次或更多，泵出超过2000加仑的血液。

但是，与你身体中的骨骼肌不同，你的心脏肌肉永远不会停止和休息。如果你的心脏停止跳动，那么在你的其他身体系统永久受损或完全停止运转之前，你只有很少的时间重新启动，只有几分钟的时间。

三、Heartbeat托福听力问题：

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托福听力答案：

A1:正确答案：D