首页
登录
职称英语
Biology Cardiac Muscle[img]2012q1/ct_etoefm_etoeflistz_0107_20121[/img] [br] Lis
Biology Cardiac Muscle[img]2012q1/ct_etoefm_etoeflistz_0107_20121[/img] [br] Lis
游客
2025-02-09
37
管理
问题
Biology Cardiac Muscle
[br] Listen again to part of the lecture. Then answer the question. What can be inferred about the contraction of cardiac muscle?
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,he 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 all your other body systems are permanently damaged or stop functioning altogether.
选项
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.
答案
B
解析
Listen again to part of the lecture. Then answer the question.
"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 can be inferred about the contraction of cardiac muscle?
The professor says Electrically, they’re set up so, so that sodium and calcium-positive ions-change places with potassium-a negative ion-across the cell membrane; When sodium, calcium, and potassium ions move into or out of a cardiac cell, it causes the muscle to contract. You can infer that the contraction of cardiac muscle depends on the action of sodium, calcium, and potassium. (2.4)
转载请注明原文地址:https://tihaiku.com/zcyy/3948753.html
相关试题推荐
BiologyCardiacMuscle[img]2012q1/ct_etoefm_etoeflistz_0107_20121[/img][br]Wha
BiologyCardiacMuscle[img]2012q1/ct_etoefm_etoeflistz_0107_20121[/img][br]Why
BiologyCardiacMuscle[img]2012q1/ct_etoefm_etoeflistz_0107_20121[/img][br]Why
Economics[img]2012q1/ct_etoefm_etoeflistz_0100_20121[/img][br]Accordingtothe
Economics[img]2012q1/ct_etoefm_etoeflistz_0100_20121[/img][br]Whatisthedisc
ConversationOralReport[img]2012q1/ct_etoefm_etoeflistz_0094_20121[/img][br]W
ConversationOralReport[img]2012q1/ct_etoefm_etoeflistz_0094_20121[/img][br]W
ConversationOralReport[img]2012q1/ct_etoefm_etoeflistz_0094_20121[/img][br]W
ConversationOralReport[img]2012q1/ct_etoefm_etoeflistz_0094_20121[/img][br]W
Anthropology[img]2012q1/ct_etoefm_etoeflistz_0087_20121[/img][br]Accordingto
随机试题
Whatisthemaintopicofthetalk?[br][originaltext]ThisisJimJohnson
【说明】假定你是大四学生ZhangWei,给HW公司写一封求职信,应聘该公司销售经理岗位。【内容】1.自我介绍,表明写信目的。2.简要陈述你的学历、工作
[originaltext]M:Judy’stakingsixteencreditsandworkinginacomputercenter
随参信道对信号传输的影响可以采用均衡技术来改善。()
在UML提供的图中,()用于按时间顺序描述对象间的相互。A.网络图 B.状态
低成本策略强调降低银行成本,同时意味着成为一个低价格的竞争者。( )
下列关于优先股的说法中,错误的是()。A.在股东大会上无表决权 B.在认购股
下列关于毒蛇咬伤的临床表现正确的是()A.血液毒局部症状轻,全身症状出现晚
A.24 B.16 C.6 D.3
隧道照明控制子系统一般由分中心监控工作站、本地控制器、()等构成。A.光强
最新回复
(
0
)