Muscle Contraction

12 Key excerpts on "Muscle Contraction"

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  Muscle Injuries in Sports

  • Hans-W. Müller-Wohlfahrt, Peter Ueblacker, Lutz Haensel, William E. Garrett Jr., Hans-W. Müller-Wohlfahrt, Peter Ueblacker, Lutz Haensel, William E. Garrett Jr.(Authors)
  • 2013(Publication Date)
  • Thieme

    (Publisher)

  2 Basic Physiology and Aspects of Exercise B. Brenner, N. Maassen Translated by Terry Telger Basic Physiology 60 Sarcomere, Muscle Force, and Muscle Shortening 60 Basic Principles of Muscular Contraction and Its Regulation 61 Gradation of Muscle Force during Voluntary Movements 66 Types of Muscular Contraction 67 Neuromuscular Control Mechanisms 71 Aspects of Exercise Physiology 77 Types of Muscle Fiber 77 Overview of Muscular Metabolism 78 Warm-Up 81 Fatigue 82 Recovery 86 Training Adaptations 86 Basic Physiology B. Brenner Sarcomere, Muscle Force, and Muscle Shortening Active forces and the shortening of muscle are the result of repetitive, cyclic interactions of myosin molecules with actin filaments. To generate the highest possible forces per cross-sectional area, filaments of actin and myosin form a close-packed arrangement within the basic con-tractile unit of muscle, the sarcomere ( Fig. 2.1a ; see also Figs. 1.16 and 1.18 ). The sarcomere is the segment of a myofibril of muscle fiber located between two adjacent Z disks. Macroscopic forces are generated by the parallel ar-rangement of myofibrils in the muscle fibers and by the parallel arrangement of myriad muscle fibers in a muscle. Numerous sarcomeres are arranged in series (approxi-mately 500 per millimeter of fiber length), so that the mi-croscopic shortening of individual sarcomeres adds up to macroscopic changes in muscle length. Each myosin molecule ( Fig. 2.1b ) is composed of two intertwined heavy chains. Each heavy chain consists of a globular head domain and a threadlike tail. The tails of the two heavy chains are coiled around each other to form the rod of the myosin molecule. Each head domain is associated with two light chains. Several hundred myo-sin molecules associate at their rod parts to form the bipo-lar myosin filaments ( Fig. 2.1c ). Titin molecules are springlike structures associated with the myosin filaments and keep the myosin filaments centered in the sarcomere.

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  Cells and Tissues

  An Introduction to Histology and Cell Biology

  • Rogers(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  The irregular, branching cells, central nuclei and intercalated discs contrast with the large, regular cylinders and peripheral nuclei of striated muscle. The biological importance of Muscle Contraction These three proteins, actin, myosin and alpha-actinin, are present through a very wide range of cells, muscle and non-muscle alike. The shortening produced by their interaction in the presence of ATP and Ca 2+ pulls nearer together the sites where actin is anchored to alpha-actinin, and this reaction is the basis of almost all cell movement. The only exception is movement based on microtubules, which is responsible for transport within the cell, the beating of cilia and the swimming of sperm. Just about all our interactions with the surrounding world are due to the contraction of muscle. Talking, chewing, walking, writing, fighting, using tools are all possible only through the interactions of these three molecules. Everything that human beings have created, from flint arrowheads to ballistic missiles, from symphonies to gardens, from loaves of bread to machine tools have come into being through the shortening of muscle cells. 132 Cells and Tissues Further reading Goldspink, G. (1980). Locomotion and the slid-ing filament mechanism. In Aspects of Animal Movement, Elder, H.Y. and True-man, E.R. (Eds) pp. 1-25. Cambridge University Press. Clear recent summary. Huxley, H.E. (1965). The mechanism of muscu-lar contraction. Scient. Am. 213:6, 18-27. Review of the work that sorted out the struc-ture of striated muscle. Lazarides, E. and Revel, J.-P. (1979). The molecular basis of cell movement. Scient. Am. 240:3, 98-107. Excellent review on contrac-tion in non-muscle cells. Murray, J.M. and Weber, A (1974). The co-operative action of muscle proteins. Scient. Am. 230:2, 58-71. Reviews the mechanism of Muscle Contraction. Schoenberg, C.F. and Needham, D.M. (1976). A study of the mechanism of contraction in vertebrate smooth muscle.

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  Compendium of Biophysics

  • Andrey B. Rubin(Author)
  • 2017(Publication Date)
  • Wiley-Scrivener

    (Publisher)

  Chapter 22 Physics of Muscle Contraction, Actin-Myosin Molecular Motor

  22.1 General Description of Energy Transformation in Systems of Biological Motility

  The moving ability is a characteristic property of living organisms from protozoa to most complex ones. Contraction of skeletal, cardiac and smooth muscles and plant leaf movement, ciliary beating and flagella rotation, cell division and protoplasm movement are diverse types of motility having a common feature — transformation of chemical energy, released upon ATP hydrolysis, into mechanical work. Among linear molecular motors is myosin, moving along actin filaments, as well as kinesin and dinein, moving along microtubules formed by tubulin.

  Upon Muscle Contraction, the mechanical work is performed by the heads of myosin molecules, arranged in supramolecular structures, when they interact with polymerized actin. The main regulator of the motility in all muscles is calcium. Elucidation of molecular mechanisms for generation of force, transformation of chemical energy of ATP hydrolysis into mechanical work and mechanisms controlling these processes is the chief task of biophysics of biological motility.

  22.2 Basic Information on Properties of Cross-striated Muscles

  Skeletal and cardiac muscles as well as flight muscles in insects are ascribed to cross-striated muscles. A skeletal muscle consists of longitudinal fascicles of muscle fibers. A fiber is a long multinuclear cell with the cross-section from 10 to 100 µm. The fiber length corresponds frequently to the muscle length reaching 12 cm.

  Mechanics and Energetics of Muscle Contraction. A skeletal muscle starts to offer noticeable resistance to extension only of the length much exceeding its natural value in the organism. In response to electric excitation, this muscle develops an active force and becomes much more rigid. The muscle mechanical response to electric excitation depends on both the stimulating signal and the mechanical restrictions imposed on the muscle. Given the ends of the muscle or fiber fixed, the muscle generates an active force or mechanical tension. Tension is the force per cross-sectional area, i.e. a value having the dimension of pressure. The mode of Muscle Contraction at a constant length is called isometric. Figure 22.1

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  Pharmacology of Neuromuscular Function

  • William C. Bowman(Author)
  • 2013(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  Chapter 7

  Muscle Contraction

  Publisher Summary

  This chapter discusses the theory of Muscle Contraction. According the theory of contraction— the sliding filament theory—contraction is the result of the myofilaments sliding over one another, that is, it is a consequence of increased interdigitation of the myofilaments. In a muscle at its relaxed resting length, about two-thirds of the length of each thick filament and about half of that of each thin filament are overlapped. The process of contraction is a consequence of the formation of cross-bridges between the globular heads of the thick myosin filaments and the G actin units of the thin filaments. The cross-bridges are rapidly formed and broken, each detaching itself from one site on the thin filament and reattaching itself to another site further along and so on, with the result that the thin filament slides along the thick filament, like a line of men pulling in a rope hand over hand. Relaxation to the resting muscle length occurs because cross-bridges cease to be formed, allowing the filaments to readjust to the resting degree of interdigitation. Drugs may increase or decrease the contractions of striated muscle by affecting one or more of the processes in the excitation–contraction coupling sequence. The ultimate cause of the altered contractility is usually a change in the rate of Ca release from, in the amount of Ca2+ released from or in the rate of Ca2+ reuptake by, the sarcoplasmic reticulum.

  Fibre structure

  The cytoplasm of a muscle cell or fibre (the sarcoplasm) contains all the usual subcellular organelles, including many nuclei and mitochondria. In addition it contains the longitudinally orientated water-insoluble protein filaments, the myofilaments, that constitute the contractile apparatus and of which there may be as many as 107

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  Cellular Physiology and Neurophysiology E-Book

  Cellular Physiology and Neurophysiology E-Book

  • Mordecai P. Blaustein, Joseph P. Y. Kao, Donald R. Matteson(Authors)
  • 2019(Publication Date)
  • Elsevier

    (Publisher)

  SECTION FIVE Physiology of Muscle Contraction Outline

  • 14.  Molecular motors and the mechanism of Muscle Contraction
  • 15.  Excitation-contraction coupling in muscle
  • 16.  Mechanics of Muscle Contraction

  Passage contains an image

  Chapter 14

  Molecular motors and the mechanism of Muscle Contraction

  Objectives

  1. 1. List the common principles that apply to all molecular motors: myosin, kinesin, and dynein.
  2. 2. Describe the structure of a skeletal muscle cell and the organization of its contractile elements, and compare and contrast this with the structure of cardiac and smooth muscle.
  3. 3. Describe the sliding filament mechanism of Muscle Contraction.
  4. 4. Describe the coupling between the mechanical motions of the myosin motor and the steps involved in ATP hydrolysis during cross-bridge cycling.
  5. 5. Describe how Ca2+ interacts with the regulatory proteins troponin and tropomyosin to activate contraction in skeletal and cardiac muscle.
  6. 6. Describe how Ca2+ activates contraction in smooth muscle by promoting the phosphorylation of myosin regulatory light chain.

  Molecular motors produce movement by converting chemical energy into kinetic energy

  Movement is one of the defining characteristics of all living creatures. Motility is an essential feature of many biological activities, such as the beating of cilia and flagella, cell movement, cell division, development and maintenance of cell architecture, and Muscle Contraction, the main topic of this and the next two chapters. Indeed, the normal function of all cells requires the directional transport, within the cell, of numerous substances and organelles, such as vesicles, mitochondria, chromosomes, and macromolecules (e.g., mRNA and protein).

  The three types of molecular motors are myosin, kinesin, and dynein

  All types of cellular motility are driven by molecular motors that produce unidirectional movement along structural elements in the cell. The structural elements are either filaments composed of actin monomers or microtubules, which are polymers of the protein tubulin. Three distinct types of molecular motors that move along these structures have been described: myosin, kinesin, and dynein

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  Mathematical Mechanics: From Particle To Muscle

  From Particle to Muscle

  • Ellis D Cooper(Author)
  • 2011(Publication Date)
  • World Scientific

    (Publisher)

  Aside 12.1.10. Perhaps among the earliest published details on a Muscle Contraction simulation algorithm, this work is also notable for its stochastic framework, its direct mention of the classical work of Fenn and Hill, and its recognition of a feedback loop that yields cooperative behavior of molecules. To me what seems to be missing (see Aside 1.10.1) is thermodynamics. Muscle Contraction 311 12.1.9 2000 2010 Clarence E. Schutt and Uno Lindberg 2000 The paradigm for chemomechanical process in biology is the “sliding filament model of Muscle Contraction,” in which cross-bridges projecting out of the myosin thick filaments bind to actin thin filaments and pull them towards the center of the sarcom-eres, the basic units of contraction in muscle fibers. Actin is generally thought to be an inert rodlike element in this process. The myosin cross-bridges bind ATP as they detach from actin and hydrolyze it in the unattached state. Upon rebinding actin, the myosin head ‘rotates’ through several binding sites on actin of successively lower energy while stretching a molecular “spring” that then pulls on the actin filament. In this manner, convert-ing bond energy into elastic energy, it is believed that the free energy of ATP hydrolysis is transduced into work. myosin is often called a “motor molecule,” because the macroscopic forces generated by muscle fibers could be explained as the summed ef-fect of hundreds of myosin heads independently pulling on each actin filament. That situation has changed very recently. New measurements on the extensibility of actin filaments, and recon-sideration of the thermodynamics of muscle have cast doubts on the validity of the conventional cross-bridge theory of contraction. Attention is being increasingly focused on models that take into account the overall spatial and temporal organization in muscle lattices, and the possibility of cooperativity amongst the myosin motors [Schutt and Lindberg (2000)].

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  Principles of Anatomy and Physiology, 3rd Asia-Pacific Edition

  • Gerard J. Tortora, Bryan H. Derrickson, Brendan Burkett, Gregory Peoples, Danielle Dye, Julie Cooke, Tara Diversi, Mark McKean, Simon Summers, Flavia Di Pietro, Alex Engel, Michael Macartney, Hayley Green(Authors)
  • 2021(Publication Date)
  • Wiley

    (Publisher)

  The coverings and tendons stretch and then become taut, and the tension passed through the tendons pulls on the bones to which they are attached. The result is movement of a part of the body. You will soon learn, however, that the contraction cycle does not always result in shortening of the muscle fibres and the whole muscle. In some contractions, the cross-bridges rotate and generate tension, but the thin filaments cannot slide inward because the tension they generate is not large enough to move the load on the muscle (such as trying to lift a whole box of books with one hand). Excitation–contraction coupling An increase in Ca 2+ concentration in the sarcoplasm starts Muscle Contraction, and a decrease stops it. When a muscle fibre is relaxed, the concentration of Ca 2+ in its sarcoplasm is very low, only about 0.1 micromole per litre (0.1 mol∕L). However, a huge amount of Ca 2+ is stored inside the sarcoplasmic reticulum (figure 10.7a). As a muscle action potential propagates along the sarcolemma and into the T tubules, it causes Ca 2+ release channels in the SR membrane to open (figure 10.7b). When these channels open, Ca 2+ flows out of the SR into the sarcoplasm around the thick and thin filaments. As a result, the Ca 2+ concentration in the sarcoplasm rises tenfold or more. The released calcium ions combine with troponin, causing it to change shape. This conformational change moves tropomyosin away from the myosin-binding sites on actin. Once these binding sites are free, myosin heads bind to them to form cross-bridges, and the contraction cycle begins. The events just described are referred to collectively as excitation–contraction coupling, as they are the steps that connect excitation (a muscle action potential propagating along the sarcolemma and into the T tubules) to contraction (sliding of the filaments). FIGURE 10.7 The role of Ca 2+ in the regulation of contraction by troponin and tropomyosin.

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  Biomechanical Principles on Force Generation and Control of Skeletal Muscle and their Applications in Robotic Exoskeleton

  • Yuehong Yin(Author)
  • 2019(Publication Date)
  • CRC Press

    (Publisher)

  1 Force Generation Mechanism of Skeletal Muscle Contraction In a narrow sense, the aim of studies on the mechanism of force generation of skeletal muscle is to give theoretical explanations to the dynamic characteristics and phenomena of muscular contraction and to promote the relevant experimental researches in an iterative way of verification and correction. In a broad sense, it aims to provide theoretical guidance to practical applications in the fields such as biomechanics and biomedicine, including diagnosis and evaluation of muscle diseases, human–machine integrated coordinated control of exoskeleton robots, dynamic modeling of human motion, bionic design of artificial muscle and humanoid robot, etc. Thus, there are both great theoretical significance and wide application foreground concerning the study of force generation mechanism of skeletal muscle. In this field, the earliest breakthroughs were made by Hill [ 1 ] and Huxley [ 2 ], both of them Nobelists. Their work laid the foundation for the study on mechanism of muscular contraction. Recently, with the development of micro/nano technology and single-molecule manipulation technique, deeper understandings were achieved about the microscopic mechanism of skeletal Muscle Contraction. Physiology, physical chemistry, molecular biology, statistical thermodynamics, cybernetics, nonlinear mathematics, etc., are all involved in the study of force generation mechanism of skeletal muscle, which is typical interdisciplinary research. In consequence, both the degrees of complexity and difficulty are very high, resulting in theoretical and technical challenges. In this chapter, the morphological structure of skeletal muscle under various scales is introduced first. On that basis, the biomechanical principle of muscular contraction, i.e., the excitation–contraction coupling (ECC) process, is systematically illustrated

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  The Dynamics of Living Protoplasm

  • L. V. Heilbrunn(Author)
  • 2013(Publication Date)
  • Academic Press

    (Publisher)

  7. For many, many years muscle has been a favorite object of study in physiological laboratories and the amount of work done on it has been enormous. As a result of all this work a vast amount of information has been gathered. We know the time sequence of events when a muscle contracts, we know how much force it exerts and how much work it can do, the electrical changes that occur, the heat that is given off, and we also know many details concerning the complicated oxidative reactions that go on in a contracting muscle. Moreover, many workers have studied the effect of this, that, or the other physical or chemical agent on muscular contraction. And yet, in spite of our vast store of detailed information, there is still no certainty as to why it is that a muscle shortens. In other words, we do not really understand the mechanics of muscular contraction. There have been no lack of theories, no lack of attempts at interpretation. For a time a favorite idea was that the proteins of the muscle underwent a change in molecular shape. Direct evidence for this point of view was hard to obtain. Astbury in his X-ray diffraction studies thought that in living muscle he could on contraction detect a molecular superfolding of protein molecules (see, for example, Astbury, 1939). But this evidence unfortunately failed to materialize, for in living muscle it is not possible with present methods to detect such superfolding even if it does occur. This was shown by Spiegel-Adolf, Henny, and Ashkenaz (1944), and it has also been recognized by Astbury himself (1947). Because of the fact that a muscle is an internal combustion engine, or at any rate oxidizes organic materials just as an internal combustion engine does, biochemists have been greatly con-96 MUSCULAR CONTRACTION 7. MUSCULAR CONTRACTION 97 cerned with the various reactions involved in such oxidative processes, and most physiologists have been deeply impressed with the work and the ideas of their chemically-minded col-leagues.

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  Principles of Anatomy and Physiology

  • Gerard J. Tortora, Bryan H. Derrickson(Authors)
  • 2016(Publication Date)
  • Wiley

    (Publisher)

  As ATP binds to the ATP- binding site on the myosin head, the myosin head detaches from actin. The contraction cycle repeats as the myosin ATPase hydrolyzes the newly bound molecule of ATP, and continues as long as ATP is available and the Ca 2+ level near the thin filament is sufficiently high. The cross-bridges keep rotating back and forth with each power stroke, pulling the thin filaments toward the M line. Each of the 600 cross-bridges in one thick filament attaches and detaches about five times per second. At any one instant, some of the myosin heads are attached to actin, forming cross-bridges and generating force, and other myosin heads are detached from actin, getting ready to bind again. As the contraction cycle continues, movement of cross-bridges applies the force that draws the Z discs toward each other, and the sarcomere shortens. During a maximal Muscle Contraction, the distance between two Z discs can decrease to half the resting length. The Z discs in turn pull on neighboring sarcomeres, and the whole muscle fiber shortens. Some of the components of a muscle are elastic: They stretch slightly before they transfer the tension generated by the sliding filaments. The elastic components include titin molecules, connective tissue around the muscle fibers (endomy- sium, perimysium, and epimysium), and tendons that attach muscle to bone. As the cells of a skeletal muscle start to shorten, they first pull on their connective tissue coverings and tendons. The coverings and tendons stretch and then become taut, and the tension passed through the tendons pulls on the bones to which they are attached. The result is movement of a part of the body. You will soon learn, however, that the contraction cycle does not always result in shortening of the muscle fibers and the whole muscle. In some

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  Muscle and Nonmuscle Motility

  • Alfred Stracher(Author)
  • 2013(Publication Date)
  • Academic Press

    (Publisher)

  Indeed, a small increase, by about 1%, was observed in the peri- odicity of the myosin filaments. E. CONCLUSIONS From the evidence just described, it is quite clear that changes in the length of a striated muscle, whether they be passive or active, are brought about by a process in which the two arrays of filaments slide past each other, the lengths of both the thick myosin-containing filaments and the thin actin-containing filaments in the arrays remaining essen- tially constant. It is of course conceivable that in some animal species, under some conditions, some depolymerization of the myosin or the actin filaments may occur. However, it is quite clear from the results on vertebrate striated muscle that the sliding mechanism is independent of any such process, and reports of apparent changes in band length, unless backed up by continuous light microscope observation under artifact-free con- ditions of the same region of a fibril, should be treated with reserve. F. IMPLICATIONS Because the principal muscle proteins involved in contraction, namely actin and myosin, have been shown to be organized into separate fila- ments that slide past each other during contraction, it is clear that a relative sliding force must be developed between the filaments as a con- sequence of the chemical events associated with contractions. The chemical reaction most closely linked to contraction is the split- ting off of the terminal phosphate of adenosine triphosphate (ATP). This was suspected to be the basic energy-yielding reaction for many years, but it was not until 1962 that it was satisfactorily demonstrated to be the case in live muscle by Davies and his colleagues (Cain et ai, 1962). 1. MOLECULAR BASIS OF CONTRACTION 41 It had been shown earlier by Engelhardt and Ljubimova (1939) that the structural protein myosin was also an enzyme, an ATPase.

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  Neuromuscular Fundamentals

  How Our Musculature is Controlled

  • Nassir H. Sabah(Author)
  • 2020(Publication Date)
  • CRC Press

    (Publisher)

  sliding filament model of contraction.
• 2. The myofibrils are attached to the sarcolemma at Z disks and at the ends of the muscle fiber. Hence, when the myofibrils shorten so does the muscle fiber. The contraction-relaxation sequence of a muscle fiber in response to a single AP is a twitch . The tension developed is transmitted to the muscle ends via the connective tissue and tendons. However, the tension appearing at the ends of a muscle is only a fraction of the maximum tension that the muscle fibers are capable of developing because of the viscoelastic properties of the muscle and the short duration of the active state, as will be explained in Section 10.2.
• 3. Both ATP and Mg2+ are required for muscle relaxation. A deficiency of Mg2+ leaves the myosin heads bound to actin molecules, resulting in muscle cramps and pain. Following death, ATP production ceases. Ca2+ flow down their electrochemical potential gradient from the terminal cisternae and the extracellular fluid into the sarcoplasm, where they accumulate in the absence of extrusion by the Ca2+ -ATPase pump. The myosin heads bind to actin; but without ATP, the bond is not broken, resulting in muscle rigidity referred to as rigor mortis .
• 4. The swiveling of the cross bridge is a fast process that may take less than 1 ms.
• 5. There are at least two important reasons for the elaborate T tubule/triad system. First, it speeds up contraction by reducing the diffusion distance for Ca2+ . In the absence of the Ca2+ stores in the terminal cisternae, it would take Ca2+ a few tens of milliseconds to diffuse from the extracellular fluid to the troponin binding sites of the sarcomeres. The triad system brings the Ca2+ stores to within a fraction of a micrometer from the binding sites, thereby reducing the diffusion time to less than a few milliseconds or so. Second, it aids in the synchronization of contraction of all the sarcomeres in a muscle fiber by bringing the AP to the triads, thereby synchronizing the release of Ca2+