肌肉压合
章节大纲
-
Arm Wrestling
::装甲摔跤It’s obvious that a sport like arm wrestling depends on muscle contractions. Arm wrestlers must contract in their hands and arms, and keep them contracted in order to resist the opposing force exerted by their opponent. The wrestler whose muscles can contract with greater force wins the match.
::很明显,像手臂摔跤这样的运动取决于肌肉收缩。 手臂摔跤手必须在手和手臂上收缩,并保持合同,以抵抗对手施加的对立力量。 摔跤手的肌肉可以以更大的力量收缩的摔跤手赢得比赛。What Is a Muscle Contraction?
::什么是肌肉收缩?A muscle contraction is an increase in the tension or a decrease in the length of a muscle. Muscle tension is the force exerted by the muscle on a or other object. A muscle contraction is isometric if muscle tension changes, but muscle length remains the same. An example of isometric muscle contraction is holding a book in the same position. A muscle contraction is isotonic if muscle length changes, but muscle tension remains the same. An example of isotonic muscle contraction is raising a book by bending the arm at the elbow. The termination of a muscle contraction of either type occurs when the muscle relaxes and returns to its non-contracted tension or length.
::肌肉收缩是肌肉张力的增强或肌肉减长的减少。肌肉张力是肌肉对一个物体或其他物体施加的力量。肌肉收缩是肌肉张力变化时的偏振,但肌肉的长度保持不变。一个实测肌肉收缩的例子显示一本书处于同一位置。肌肉收缩是肌肉长变时的异音,但肌肉张力却保持不变。一个同位素肌肉收缩的例子显示,手臂在肘部弯曲,使书本升起。当肌肉放松并恢复到非包状的紧张或长度时,两种肌肉收缩都会终止。How a Skeletal Muscle Contraction Begins
::骨骼肌肉收缩如何开始Excluding reflexes , all contractions occur as a result of conscious effort originating in the brain . The brain sends electrochemical signals through the somatic nervous system to motor neurons that innervate muscle fibers (to review how the brain and function, see the chapter Nervous System) . A single motor neuron with multiple axon terminals is able to innervate multiple muscle fibers, thereby causing all of them to contract at the same time. The connection between a motor neuron axon terminal and a muscle fiber occurs at a site called a neuromuscular junction. This is a chemical where a motor neuron transmits a signal to a muscle fiber to initiate a muscle contraction. The process by which a signal is transmitted at a neuromuscular junction is illustrated in the diagram .
::除反射外,所有收缩都是由大脑自觉努力的结果。大脑通过体神经系统发送电化学信号,以驱动内空肌肉纤维的神经神经元(以审查大脑和功能如何,见神经系统),一个带有多个轴终端的单一运动神经元能够内插多个肌肉纤维,从而同时导致所有肌肉纤维的收缩。一个运动神经轴终端和肌肉纤维之间的联系发生在一个称为神经肌肉交叉点的地方。这是一种化学物质,其中运动神经元将信号传送到肌肉纤维,以引发肌肉收缩。图中说明了在神经肌肉交叉点传输信号的过程。This diagram represents the sequence of events that occurs when a motor neuron stimulates a muscle fiber to contract.
::本图代表当运动神经元刺激肌肉纤维收缩时发生事件的顺序。The sequence of events begins when an action potential is initiated in the cell body of a motor neuron, and the action potential is propagated along the neuron’s axon to the neuromuscular junction. Once the action potential reaches the end of the axon terminal, it causes the release of the neurotransmitter acetylcholine (A C h) from synaptic vesicles in the axon terminal. The A C h molecules diffuse across the synaptic cleft and bind to receptors on the muscle fiber, thereby initiating a muscle contraction.
::当运动神经元细胞体中开始出现行动潜力时,活动潜力将沿着神经轴向神经肌肉交叉路口扩散。 一旦行动潜力达到轴终端的尾端,就会导致轴终端中神经传感性乙酰胆碱(ACh)的释放。ACH分子会扩散到神经元裂口,并会与肌肉纤维的受体捆绑在一起,从而引发肌肉收缩。Sliding Filament Theory of Muscle Contraction
::肌肉收缩理论Once the muscle fiber is stimulated by the motor neuron, actin and myosin filaments within the skeletal muscle fiber slide past each other to produce a contraction. The sliding filament theory is the most widely accepted explanation for how this occurs. According to this theory , muscle contraction is a cycle of molecular events in which thick myosin filaments repeatedly attach to and pull on thin actin filaments, so the filaments slide over one another. The actin filaments are attached to Z discs, each of which marks the end of a sarcomere . The sliding of the filaments pulls the Z discs of a sarcomere closer together, thus shortening the sarcomere. As this occurs, the muscle contracts.
::一旦肌肉纤维被运动神经神经、动作和骨骼肌肉纤维的细丝所刺激,骨骼肌肉纤维会相互滑过,产生收缩。滑动丝理论是这种情况发生最普遍接受的解释。根据这一理论,肌肉收缩是一个分子事件的循环,在这种循环中,薄的肌丝会反复粘附并拉在薄的纤维上,因此细的丝片会相互拉扯。动动丝会附在Z盘上,每张都标志着一个正正方形的结束。滑动丝会拉近一个正方形的圆盘,从而缩短正方形。随着这种情况的发生,肌肉合力就会拉近。Both top and bottom diagrams show the thin and thick protein filaments in a sarcomere. The green and orange structures are thin actin filaments. The purple structures are thick myosin filaments. In the top diagram, the muscle fiber is relaxed. In the bottom diagram, the muscle fiber is contracted and shortened. In the latter diagram, you can see crossbridges that form when myosin heads attach to the thin actin filaments. The sarcomere is shorter in this diagram because the thick filaments have pulled the actin filaments inward toward the center of the sarcomere.
::上图和下图都显示了沙红色中的薄和厚蛋白丝。 绿色和橙色结构是薄的活性丝。 紫色结构是厚的肌质丝。 在上图中, 肌肉纤维是松动的。 在下图中, 肌肉纤维是缩缩缩和缩短的。 在后图中, 您可以看到当我的骨灰头附在薄的活性丝丝上时形成的十字桥。 此图中, 沙红是短的, 因为厚的丝状将活性丝拉进沙红色的中心。Crossbridge Cycling
::交叉交桥自行车Crossbridge cycling is a sequence of molecular events that underlies the sliding filament theory. There are many projections from the thick myosin filaments, each of which consists of two myosin heads (you can see the project ions and heads in the figures and ). Each myosin head has binding sites for ATP (or the products of ATP hydrolysis : ADP and P i ) and for actin. The thin actin filaments also have binding sites for the myosin heads. A crossbridge forms when a myosin head binds with an actin filament.
::跨桥环绕是一系列分子事件,这是滑动丝丝理论的基础。从厚厚的近氧丝丝中可以发现许多预测,每根厚的近氧丝丝由两颗近氧头组成(你可以在数字和图表中看到预测和头部)。每个近氧头都有固定的ATP(或ATP水解产品:ADP和Pi)和动作地点。薄的活性丝也有固定的近氧头地点。当近氧头与活性丝结合时,一个十字架形。The process of c rossbridge cycling is shown in the figure . A crossbridge cycle begins when the myosin head binds to an actin filament. ADP and P i are also bound to the myosin head at this stage. Next, a power stroke moves the actin filament inward toward the center of sarcomere, thereby shortening the sarcomere. At the end of the power stroke, ADP and P i are released from the myosin head, leaving the myosin head attached just to the thin filament until another ATP binds to the myosin head. When ATP binds to the myosin head, it caus es the myosin head to detach from the actin . ATP is once again split into ADP and P i and the energy released is used to move the myosin head into a "cocked" position. Once in this position, the myosin head can bind to the actin filament again, and another crossbridge cycle begins .
::跨桥环绕过程在图中显示。 跨桥循环从以下两种情况开始: 头与一根丝状物结合。 ADP 和 Pi 也在这个阶段被绑在骨髓头上。 下一步, 电击将丝状物向丝状物向内移, 从而缩短刺状物的长度。 在电击结束的时候, ADP 和 Pi 被从我的骨质物头中释放出来, 将肌质头与细细细的丝状物连接起来, 直到另一个ATP 连接到骨质物头。 当ATP 连接到骨质头时, 将骨质物头从脑部切除。 ATP 再次分裂为ADP 和 Pi , 释放的能量被用来将骨质物头移动到一个“ 发酵” 位置。 一旦处于这一位置, 肌质头可以再次与纤维状物结合, 另一盘桥循环开始。Crossbridge cycling
::跨桥自行车Energy for Muscle Contraction
::肌肉收缩能源According to the sliding filament theory, ATP is needed to provide the energy for a muscle contraction. Where does this ATP come from? Actually, there are multiple potential sources, as illustrated in the diagrams .
::根据滑动丝质理论, ATP 需要为肌肉收缩提供能量。 ATP 来源于何处? 事实上,如图表所示, 有许多潜在来源。-
As you can see from the first diagram, some ATP is already available in a resting muscle. As a muscle contraction starts, this ATP is used up in just a few seconds. More ATP is generated from creatine phosphate, but this ATP is used
up r
apidly as well. It’s gone in another 15 seconds or so.
::从第一个图表中可以看到,一些ATP已经存在于休息肌肉中。随着肌肉收缩的开始,这个ATP在短短几秒钟内就用完了。更多的ATP来自脊髓磷酸盐,但是这个ATP也用得很快。它在另外15秒钟内就消失了。 -
Glucose
from the
and glycogen stored in muscle can then be used to make more ATP. Glycogen breaks down to form glucose, and each glucose molecule produces two molecules of ATP and two molecules of
pyruvate
. Pyruvate (as pyruvic acid) can be used in
aerobic respiration
if oxygen is available (diagram c). Alternatively, pyruvate can be used in
, if oxygen is not available. The latter produces lactic acid, which may contribute to muscle fatigue. Anaerobic respiration typically occurs only during strenuous
when so much ATP is needed that sufficient oxygen cannot be delivered to the muscle to keep up.
::肌肉中储存的甘蔗糖和甘蓝可被用来制造更多的ATP。 甘蓝可分解成葡萄糖,每个葡萄糖分子产生两种ATP分子和两种蒸发剂分子。 在有氧的情况下,可以将Pyruvic酸(作为pyruvic酸)用于有氧呼吸。 或者,如果缺氧,也可以将聚氨酸用于(如果缺氧),后者产生酸脂,这可能会导致肌肉疲劳。 只有在非常需要ATP时,才会发生厌氧呼吸,以至于无法向肌肉输送足够的氧气以保持活力。 -
Resting or moderately active muscles can get most of the ATP they need for contractions by aerobic respiration. This process takes place in the
of muscle
. In the process, glucose and oxygen react to produce carbon dioxide,
, and many molecules of ATP.
::恢复性或中度活性肌肉可以通过有氧呼吸获得大部分需要的ATP。这一过程发生在肌肉中。在这一过程中,葡萄糖和氧反应产生ATP的二氧化碳和许多分子。
Muscles require many ATP molecules to power muscle contractions. The ATP can come from the three sources illustrated in diagrams a-c.
::肌肉需要许多ATP分子来驱动肌肉收缩。 ATP可以来自图表a-c所示的三个来源。Feature: Human Biology in the News
::特著:《新闻》中的人类生物学Interesting and hopeful basic research on muscle contraction is often in the news, because muscle contractions are involved in so many different body processes and disorders, including heart failure and stroke.
::有关肌肉收缩的有趣和充满希望的基本研究往往出现在新闻中,因为肌肉收缩涉及许多不同的身体过程和失调,包括心脏病和中风。-
Heart failure
is a chronic condition in which
cardiac muscle
cells cannot contract forcefully enough to keep
adequately supplied with oxygen. In 2016, researchers at the University of Texas Southwestern Medical Center identified a potential new target for the
of
drugs
to increase the strength of cardiac muscle contractions in patients with heart failure. The UT researchers found a previously unidentified protein involved in muscle contraction. The protein, which is very small, turns off the “brake” on the heart so it pumps blood more vigorously. At the molecular level, the protein affects the calcium-ion pump that controls muscle contraction. The scientists also found the same protein in slow-twitch skeletal muscle fibers. Interestingly, the protein is encoded by a stretch of mRNA that had been dismissed by scientists as non-coding
, commonly referred to as “junk” RNA. According to one of the researchers, “We dipped into the RNA ‘junk’ pile and came up with a hidden treasure.” This result is likely to lead to searches for additional treasures that might be hiding in the RNA junk pile.
::心脏衰竭是一种慢性病,心脏肌肉细胞无法以足够强力收缩来保持氧气。 2016年,得克萨斯大学西南医学中心的研究人员确定了药物的潜在新目标,以增加心脏衰竭患者心脏肌肉萎缩的强度。 UT研究人员发现一个先前未知的蛋白质与肌肉收缩有关。蛋白质非常小,关闭心脏上的“刹车”以便更有力地抽取血液。在分子一级,蛋白影响控制肌肉收缩的钙离子泵。科学家还在缓慢抽动的骨骼肌肉纤维中发现了同样的蛋白质。有趣的是,蛋白质被科学家认为是非编码的MRNA,通常被称为“junk”RNA。据一位研究人员称 , “ 我们钻进了RNA`junk'堆,发现了隐藏的宝藏 ” 。 这一结果可能导致搜索可能藏在RNA垃圾堆中的更多宝藏。 -
A
stroke
occurs when a blood clot lodges in an
artery
in the brain and cuts off blood flow to part of the brain. Damage from the clot would be reduced if the
smooth muscles
lining brain arteries relaxed following a stroke, because the arteries would dilate and allow greater blood flow to the brain. In a recent study undertaken at the Yale University School of Medicine, researchers determined that the muscles lining
in the brain actually contract
after
a stroke. This constricts the vessels, reduces blood flow to the brain, and appears to contribute to permanent brain damage. The hopeful takeaway of this finding is that it suggests a new target for stroke therapy.
::当血液凝块进入大脑动脉并切断部分脑部的血液流动时,就会发生中风。如果中风后光滑的肌肉内衬脑动脉松动,因为动脉会膨胀并允许更多的血液流入大脑,血块的损伤就会减少。在耶鲁大学医学院最近进行的一项研究中,研究人员确定脑部的肌肉内衬在中风后实际上会收缩。这使得血管收缩,减少对大脑的血液流,并似乎会助长永久性的脑损伤。这一发现令人满怀希望的结果是,它暗示了中风治疗的新目标。
Summary
::摘要-
A muscle contraction is an increase in the tension or a decrease in the length of a muscle. A muscle contraction is isometric if muscle tension changes, but muscle length remains the same. It is isotonic if muscle length changes, but muscle tension remains the same.
::肌肉收缩是肌肉张力的加剧或肌肉长度的缩短。肌肉收缩是肌肉张力变换时的等分法,但肌肉的长度保持不变。肌肉变换时是同位素,但肌肉张力却保持不变。 -
A skeletal muscle contraction begins with electrochemical stimulation of a muscle fiber by a motor neuron. This occurs at a chemical synapse called a neuromuscular junction. The neurotransmitter acetylcholine diffuses across the synaptic cleft and binds to receptors on the muscle fiber. This initiates a muscle contraction.
::骨骼肌肉收缩始于运动神经元对肌肉纤维的电化学刺激,发生在称为神经肌肉交叉口的化学突触中。神经分质乙酰胆碱在突触左裂处扩散,与肌肉纤维的受体捆绑在一起。这引发肌肉收缩。 -
Once
stimulated
, the protein filaments within the skeletal muscle fiber slide past each other to produce a contraction. The sliding filament theory is the most widely accepted explanation for how this occurs. According to this theory, thick myosin filaments repeatedly attach to and pull on thin
actin
filaments, thus shortening sarcomeres.
::一旦被刺激,骨骼肌肉纤维内的蛋白丝就会相互滑过,以产生收缩。 滑动丝理论是最广为人接受的如何发生这种情况的解释。 根据这一理论,厚厚的肌丝反复附着和拉扯薄的纤维,从而缩短了丝状。 -
Crossbridge cycling is a cycle of molecular events that underlies the sliding filament theory. Using energy in ATP, myosin heads repeatedly bind with and pull on actin filaments. This moves the actin filaments toward the center of a sarcomere, shortening the sarcomere and causing a muscle contraction.
::跨桥环绕是一个分子事件的循环,它支撑着滑动丝质理论。在 ATP 中,使用能量,肌肤头反复被活性丝状物捆绑并拉动。这把丝质的活性向弧线中心移动,缩短弧线并造成肌肉收缩。 -
The ATP needed for a muscle contraction comes first from ATP already available in the cell, and more is generated from creatine phosphate. These sources are quickly used up. Glucose and glycogen can be broken down to form ATP and pyruvate. Pyruvate can then be used to produce ATP in aerobic respiration if oxygen is available, or it can be used in anaerobic respiration if oxygen is not available.
::肌肉收缩所需的ATP首先来自细胞中已有的ATP,更多来自丙烯磷酸酯。这些来源很快用完。可以将葡萄糖和甘油分解为ATP 和 prevate。然后,若缺氧,可使用Pyruvate在有氧呼吸中生成ATP,或者在缺氧情况下可用于厌氧呼吸。
Review
::回顾1. What is a skeletal muscle contraction?
::1. 什么是骨骼肌肉萎缩?2. Distinguish between isometric and isotonic contractions of skeletal muscle.
::2. 区分骨骼肌肉的等离子和同位素收缩。3. How does a motor neuron stimulate a skeletal muscle contraction?
::3. 运动神经元如何刺激骨骼肌肉收缩?4. What is the sliding filament theory?
::4. 滑动丝丝理论是什么?5. Describe crossbridge cycling.
::5. 描述跨桥自行车。6. Where does the ATP needed for a muscle contraction come from?
::6. 肌肉收缩所需的ATP从何而来?7. Explain why an action potential in a single motor neuron can cause multiple muscle fibers to contract.
::7. 解释为什么单一运动神经元的动作潜力可能导致多个肌肉纤维收缩。8. The name of the synapse between a motor neuron and a muscle fiber is the _______________ _________.
::8. 运动神经元和肌肉纤维之间的突触的名称是。9. If the acetylcholine receptors on muscle fibers were blocked by a drug, what do you think this would do to muscle contraction? Explain your answer.
::9. 如果肌肉纤维的乙酰胆碱受体被一种药物阻塞, 你认为这对肌肉收缩会有什么作用?解释你的答复。10. True or False: According to the sliding filament theory, actin filaments actively attach to and pull on myosin filaments.
::10. 真实或假:根据滑动丝丝理论,活性丝会积极附着和拉动肌质丝。11. True or False: When a motor neuron produces an action potential, the sacromeres in the muscle fiber that it innervates become shorter as a result.
::11. 真实或假:当运动神经元产生行动潜力时,其内嵌的肌肉纤维中的腐蚀物会因此变短。12. Explain how crossbridge cycling and sliding filament theory are related to each other.
::12. 解释跨桥自行车和滑动丝丝理论如何相互关联。13. When does anaerobic respiration typically occur in human muscle cells?
::13. 人体肌肉细胞一般何时会出现厌氧呼吸?14. Which process produces more ATP: aerobic respiration or anaerobic respiration?
::14. 哪种过程产生更多的ATP:有氧呼吸或厌氧呼吸?15. If there were no ATP available in a muscle, how would this affect crossbridge cycling? What would this do to muscle contraction?
::15. 如果肌肉没有ATP,这将如何影响跨桥自行车?这对肌肉收缩有何影响?Explore More
::探索更多Watch this animation to further explore how a muscle contraction occurs:
::观看此动画以进一步探索肌肉收缩是如何发生的:Check out this video to learn about how a paralyzed man can use his brain waves to play a video game:
::以了解瘫痪者如何使用脑波玩游戏: -
As you can see from the first diagram, some ATP is already available in a resting muscle. As a muscle contraction starts, this ATP is used up in just a few seconds. More ATP is generated from creatine phosphate, but this ATP is used
up r
apidly as well. It’s gone in another 15 seconds or so.
