14.2 肌肉系统介绍
Section outline
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Marvelous Muscles
::惊人的肌肉Does the word muscle make you think of the well-developed of a weightlifter, like the woman in this photo? Her name is Natalia Zabolotnaya, and she’s a Russian Olympian. The muscles that are used to lift weights are easy to feel and see, but they aren’t the only muscles in the . Many muscles are deep within the body, where they form the walls of internal organs and other structures. You can flex your biceps at will, but you can’t control internal muscles like these. It’s a good thing that these internal muscles work without any conscious effort on your part, because movement of these muscles is essential for survival.
::肌肉这个词是否让你想到像这张照片中的女人那样重量提升器的发育良好?她的名字叫Natalia Zabolotnaya,她是俄罗斯奥林匹亚人。用来提升重量的肌肉很容易感知和看到,但并不是体内唯一的肌肉。许多肌肉在身体深处,形成内部器官和其他结构的墙壁。你可以随意伸展你的二头肌,但你无法控制这样的内肌肉。这些内肌肉在工作上没有你的任何意识努力是一件好事,因为这些肌肉的移动是生存的关键。What Is the Muscular System?
::什么是肌肉系统?The muscular system consists of all the muscles of the body. The largest percentage of muscles in the muscular system consists of , which are attached to and enable voluntary body movements. There are almost 650 skeletal muscles in the human body, many of them shown in the figure . Besides skeletal muscles, the muscular system also includes cardiac muscle — which makes up the walls of the heart — and smooth muscles , which control movement in other internal organs and structures.
::肌肉系统由身体的所有肌肉组成,肌肉系统中肌肉的最大比例是附于身体自愿运动并促成自愿运动的肌肉,人体中约有650个骨骼肌肉,其中许多在图中显示,除了骨骼肌肉外,肌肉系统还包括心脏肌肉——它构成心脏的墙壁——以及控制其他内部器官和结构运动的光滑肌肉。Many of the skeletal muscles in the human muscular system are shown in this drawing of the human body.
::人体肌肉系统中的许多骨骼肌肉 都可见于人体的图画中Muscle Structure and Function
::肌肉结构和职能Muscles composed mainly of muscle , which are also called muscle fibers (mainly in skeletal and cardiac muscle) or myocytes (mainly in smooth muscle). Muscle cells are long, thin cells that are specialized for the function of contracting. They contain filaments that slide over one another using energy in ATP . The sliding filaments increase the tension in — or shorten the length of — muscle cells, causing a contraction. Muscle contractions are responsible for virtually all the movements of the body, both inside and out.
::肌肉主要由肌肉组成,肌肉也称为肌肉纤维(主要是骨骼和心脏肌肉)或小眼(主要是光滑肌肉),肌肉细胞是长的、细的细胞,专门用于包扎功能,内有丝状,用ATP的能量滑过对方,滑动的丝状增加肌肉细胞的紧张,或缩短其长度,造成收缩,肌肉收缩几乎是身体内外所有运动的原因。Skeletal muscles are attached to bones of the skeleton. When these muscles contract, they move the body. They allow us to use our limbs in a variety of ways, from walking to turning cartwheels. Skeletal muscles also maintain posture and help keep balance .
::骨骼肌肉附着在骨骼骨骼上,当肌肉收缩时,它们会移动身体,允许我们以各种方式使用肢体,从行走到转轮,骨骼肌肉也保持姿势,有助于保持平衡。Smooth muscles in the walls of contract to cause vasoconstriction, which may help conserve body heat. Relaxation of these muscles causes vasodilation, which may help the body lose heat. In the organs of the , smooth muscles squeeze food through the gastrointestinal tract by contracting in sequence to form a wave of muscle contractions called peristalsis . Think of squirting toothpaste through a tube by applying pressure in sequence from the bottom of the tube to the top, and you have a good idea of how food is moved by muscles through the digestive system. Peristalsis of smooth muscles also moves urine through the urinary tract.
::光滑的肌肉通过胃肠道的器官挤压食物,按顺序排列形成肌肉收缩的波,称为持久性。想一想用从管底到顶部的排气压将牙膏压穿管管,并很好地了解肌肉如何通过消化系统移动食物。光滑的肌肉的持久性也会通过尿道移动尿液。Cardiac muscle tissue is found only in the walls of the heart. When cardiac muscle contracts, it makes the heart beat. The pumping action of the beating heart keeps flowing through the .
::心肌组织只能在心脏的墙壁中找到。当心脏肌肉收缩时,心脏会跳动。跳动的心脏的抽动动作会不断流动。Muscle Hypertrophy and Atrophy
::肌肉大富营养和营养不良Muscles can grow larger, or hypertrophy. This generally occurs through increased use, although hormonal or other influences can also play a role. T he increase in testosterone that occurs in males during , for example, causes a significant increase in muscle size. Physical that involves weight bearing or resistance training can increase the size of skeletal muscles in virtually everyone. Exercises (such as running) that increase the heart rate may also increase the size and strength of cardiac muscle. The size of muscle, in turn, is the main determinant of muscle strength, which may be measured by the amount of force a muscle can exert.
::肌肉会变大或变肥,这通常通过增加使用来发生,尽管荷尔蒙或其他影响也可以发挥作用。例如,雄性在肌肉体积方面出现的睾丸激素增加,导致肌肉体积的大幅上升。体力的承受力或抗力训练可以增加几乎所有人骨骼肌肉的体积。提高心率的锻炼(如跑动)也可以增加心肌的体积和强度。肌肉的体积反过来也是肌肉力的主要决定因素,可以用肌肉能施加的力量来衡量。Muscles can also grow smaller, or atrophy , which can occur through lack of physical activity or from starvation. People who are immobilized for any length of time — for example, because of a broken bone or surgery — lose muscle mass relatively quickly. People in concentration or famine camps may be so malnourished that they lose much of their muscle mass, becoming almost literally just “skin and bones.” Astronauts on the International Space Station may also lose significant muscle mass because of weightlessness in space (see photo ).
::肌肉也可能变小,也可能变萎缩,这可以通过缺乏身体活动或饥饿而发生,在任何一段时间内(例如骨折或外科手术)无法活动的人,会相对迅速地失去肌肉质量,在集中或饥荒营的人可能营养不良,以致失去大部分肌肉质量,几乎完全成为“皮肤和骨头 ” 。 国际空间站的宇航员也可能由于空间失重而失去巨大的肌肉质量(见照片 ) 。It is important for astronauts to exercise on board the International Space Station to help counter the loss of muscle mass that occurs because they are weightless without Earth’s gravity.
::宇航员必须在国际空间站上进行锻炼,以帮助对付肌肉质量的丧失,因为肌肉质量的丧失没有地球的重力,没有重量。Many diseases, including and AIDS, are often associated with muscle atrophy. Atrophy of muscles also happens with age. As people grow older, there is a gradual decrease in the ability to maintain skeletal muscle mass, known as sarcopenia. The exact cause of sarcopenia is not known, but one possible cause is a decrease in sensitivity to growth factors that are needed to maintain muscle mass. Because muscle size determines strength, muscle atrophy causes a corresponding decline in muscle strength.
::许多疾病,包括艾滋病和艾滋病,往往与肌肉萎缩有关,肌肉萎缩也随着年龄的增长而发生,随着年龄的增长,保持骨骼肌肉质量的能力逐渐下降,也就是所谓的石球。 鼻孔硬化的确切原因尚不得而知,但一个可能的原因是对维持肌肉质量所需的生长因素的敏感度下降。 因为肌肉大小决定了体力,肌肉萎缩导致肌肉强度相应下降。In both hypertrophy and atrophy, the number of muscle fibers does not change. What changes is the size of the muscle fibers. When muscles hypertrophy, the individual fibers become wider. When muscles atrophy, the fibers become narrower.
::在肥沃和萎缩两个方面,肌肉纤维的数量没有变化。改变的是肌肉纤维的大小。当肌肉萎缩时,个别纤维会变得更大。当肌肉萎缩时,纤维会变得更窄。Interactions with Other Body Systems
::与其他机构系统的互动Muscles cannot contract on their own. Skeletal muscles need stimulation from motor neurons in order to contract. The point where a motor attaches to a muscle is called a neuromuscular junction . Let’s say you decide to raise your hand in class. Your brain sends electrical messages through motor neurons to your arm and shoulder. The motor neurons, in turn, stimulate muscle fibers in your arm and shoulder to contract, causing your arm to rise.
::肌肉无法自行缩缩。 骨骼肌肉需要来自运动神经元的刺激才能缩缩。 肌肉的发动机附着于肌肉的点被称为神经肌肉交叉口。 可以说你决定在课堂上举手。 你的大脑通过运动神经元向手臂和肩膀发送电子信息。 反过来,运动神经元刺激手臂和肩膀的肌肉纤维,导致手臂上升。Involuntary contractions of smooth and cardiac muscles are also controlled by electrical impulses, but in the case of these muscles, the impulses come from the autonomic nervous system (smooth muscle) or specialized cells in the heart (cardiac muscle). and some other factors also influence involuntary contractions of cardiac and smooth muscles. For example, the fight-or- flight hormone adrenaline increases the rate at which cardiac muscle contracts, thereby speeding up the heartbeat.
::光滑和心肌的非自愿收缩也受到电脉冲的控制,但对于这些肌肉来说,脉冲来自自主神经系统(肌肉)或心脏中的特殊细胞(心肌),其他一些因素也影响到心肌和光滑肌肉的非自愿收缩。例如,搏击或飞行激素肾上腺素会增加心脏肌肉收缩的速度,从而加速心跳。Muscles cannot move the body on their own. They need the to act upon. The two systems together are often referred to as the musculoskeletal system . Skeletal muscles are attached to the skeleton by tough connective tissues called tendons . Many skeletal muscles are attached to the ends of bones that meet at a joint. The muscles span the joint and connect the bones. When the muscles contract, they pull on the bones, causing them to move. The skeletal system provides a system of levers that allow body movement. The muscular system provides the force that moves the levers.
::肌肉不能自行移动身体, 它们需要采取行动。 两种系统一起通常被称为肌肉骨骼系统。 骨骼肌肉通过称为弯纹的硬结组织连接在骨骼上。 许多骨骼肌肉被连接在结骨端上, 肌肉横跨连接骨骼。 当肌肉收缩时, 它们拉扯骨骼, 导致它们移动。 骨骼系统提供了一种允许身体运动的杠杆系统。 肌肉系统提供了移动杠杆的力量 。Summary
::摘要-
The muscular system consists of all the muscles of the body. There are three types of muscle: skeletal muscle (which is attached to bones and enables voluntary body movements), cardiac muscle (which makes up the walls of the heart and makes it beat), and smooth muscle (which is found in the walls of internal organs and other internal structures and controls their movements).
::肌肉系统由身体的所有肌肉组成,有三种肌肉:骨骼肌肉(附在骨骼上,可以自愿的身体运动)、心脏肌肉(构成心脏的墙壁并使其跳动)和光滑肌肉(在内脏和其他内部结构的墙壁中发现,并控制其运动)。 -
Muscles are composed mainly of muscle cells, which may also be called muscle fibers or myocytes. Muscle cells are specialized for the function of contracting, which occurs when protein filaments inside the cells slide over one another using energy in ATP.
::肌肉主要由肌肉细胞组成,这些细胞也可以称为肌肉纤维或短小细胞。 肌肉细胞是专门用来承压功能的,当细胞内蛋白丝利用ATP的能量滑向对方时,就会发生这种作用。 -
Muscles can grow larger, or hypertrophy. This generally occurs through increased use (physical exercise), although hormonal or other influences can also play a role. Muscles can also grow smaller, or atrophy. This may occur through lack of use, starvation, certain diseases, or aging. In both hypertrophy and atrophy, the size — but not the number — of muscle fibers changes. The size of muscles is the main determinant of muscle strength.
::肌肉可能会变大或变肥,这通常通过增加使用(物理锻炼)而发生,尽管荷尔蒙或其他影响也可以发挥作用,肌肉也可能变小或变衰老,这可能由于缺乏使用、饥饿、某些疾病或衰老而发生,在肥壮和萎缩中,肌肉纤维变化的大小——但数量——是肌肉强度的主要决定因素。 -
Skeletal muscles need the stimulus of motor neurons to contract, and to move the body, they need the skeletal system to act upon. Involuntary contractions of cardiac and smooth muscles are controlled by special cells in the heart, nerves of the autonomic nervous system, hormones, or other factors.
::骨骼肌肉需要电动神经元的刺激以收缩和移动身体,它们需要骨骼系统来采取行动。 心肌和光滑肌肉的非自愿收缩由心脏、神经神经系统神经、荷尔蒙或其他因素的特殊细胞控制。
Review
::回顾1. What is the muscular system?
::1. 什么是肌肉系统?2. Describe muscle cells and their function.
::2. 描述肌肉细胞及其功能。3. Identify three types of muscle tissue and where each type is found.
::3. 查明三类肌肉组织及其发现地点。4. Define muscle hypertrophy and muscle atrophy.
::4. 界定肌肉肥大和肌肉萎缩。5. What are possible causes of muscle hypertrophy?
::5. 肌肉肥大的可能原因是什么?6. Give three reasons that muscle atrophy may occur.
::6. 给出三点理由说明可能发生肌肉萎缩。7. How do muscles change when they increase or decrease in size?
::7. 肌肉在体积增减时如何变化?8. How do changes in muscle size affect strength?
::8. 肌肉大小的变化如何影响体力?9. Explain why astronauts can easily lose muscle mass in space.
::9. 解释为什么宇航员在空间很容易失去肌肉质量。10. Describe how the terms muscle cells , muscle fibers , and myocytes relate to each other.
::10. 说明肌肉细胞、肌肉纤维和小骨髓之间的关联。11. Muscle tissue in the stomach is considered ___________________.
::11. 胃部肌肉组织被视为。a. c ardiac muscle
::a. 心脏肌肉b. s keletal muscle
::b. 骨骼肌肉c. s mooth muscle
::c. 光滑肌肉d. v oluntary muscle
::d. 自愿肌肉12. Muscle contraction is the __________ of muscle fibers.
::12. 肌肉收缩是肌肉纤维的。a. hypertrophy
::a. 肥大b. atrophy
::b. 萎缩c. lengthening
::c. 延长d. shortening
::d. 缩短时间13. True or False: Smooth muscle does not contract.
::13. 真实或假:肌肉平滑不会收缩。14. Name two systems in the body that work together with the muscular system to carry out movements.
::14. 列出机构内与肌肉系统合作进行移动的两个系统。15. Describe one way in which the muscular system is involved in regulating body temperature.
::15. 说明肌肉系统参与调节身体温度的方式。Explore More
::探索更多Learn more about the growing problem of sarcopenia by watching this TED talk:
::通过观看TED的演讲, 更多了解日益严重的嘲讽问题:Check out this video to learn about peristalsis of the large intestine:
::校对:Portnoy 校对:Portnoy -
The muscular system consists of all the muscles of the body. There are three types of muscle: skeletal muscle (which is attached to bones and enables voluntary body movements), cardiac muscle (which makes up the walls of the heart and makes it beat), and smooth muscle (which is found in the walls of internal organs and other internal structures and controls their movements).
