DOCSLIB.ORG

Skeletal Muscle Physiology

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Skeletal Muscle Physiology Physiology Unit 2 Muscle Physiology In Physiology Today Skeletal Muscle • Characteristics – Striated – Multinucleated – Voluntary • Organization – Myofiber • Myofibril –Myofilament Sarcomere • Functional unit of skeletal muscle • Composed of 3 filaments – Thick filament • Myosin – Thin filament • Actin • Troponin • Tropomyosin – Elastic filament • Titin Thick and Thin Filaments Sliding Filament Theory of Contraction • Cross bridges form between the thick and thin filaments • Thin filaments slide across the thick filaments – Thin filaments will move closer together – Distance between Z lines decreases – I band and H bands shorten during contraction – A band stays the same Muscle Physiology • 2 distinct events happen which lead to muscle contraction 1.Electrical events – Action Potential – Receptor activation – EPP – AP – Electrical events trigger the mechanical events 2.Mechanical events – Developing tension in the muscle – Increase Ca2+ levels – contractile proteins moving – muscle fiber shortens Stimulus to Contraction • Stimulus – Receptor activation – Skeletal muscle: ACh binding to N-Achr – Results in an EPP • Latent period – Excitation-Contraction coupling • Contraction period – Cross-Bridge Cycling – Generates tension in the muscle • Relaxation period – Stimulus ends or cell fatigues – Muscle returns to its resting state Muscle Twitch Stimulus • Somatic motor neurons innervate skeletal muscle • Largest diameter neurons • Myelinated • High velocity AP • Upon reaching muscle, axon divides into many branches • Each branch forming a single junction with a muscle fiber = motor unit EPP to AP Action Potential to Contraction • AP lasts 1-2 ms • Completed before any mechanical activity begins • Mechanical activity (contraction) may last >100 ms • Electrical activity (action potential) does not act on contractile proteins • Produces a state of increased cytolsolic [Ca2+] – Resting [Ca2+] = 0.1 mMol/L – After AP [Ca2+] = 1 mMol/L Latent Period • Excitation-Contraction Coupling • Sequence of events from the generation of an AP across the sarcolemma to Ca2+ release inside of the myofiber • Sarcolemma is an excitable membrane – Generating an AP (from EPP) – Propagating an AP – Similar mechanisms as neurons Contraction Period • Increase in intracellular Ca2+ levels trigger the mechanical events • Ca2+ activates Cross- Bridge Cycling Sarcoplasmic Reticulum • Lateral sacs store Ca2+ • T-tubule has DHP receptors – DHP receptors are normally voltage gated Ca2+ channels – In skeletal muscle t-tubules, acts as a voltage sensor • SR has ryanodine receptors – Intracellular Ca2+ channels – When Ca2+ channels open, Ca2+ moves into cytoplasm Calcium Release • DHP receptors trigger calcium release • Ryanodine calcium channels open • Influx of calcium from SR into cytoplasm • Calcium influx triggers cross bridge cycling Activation by Ca2+ • Tropomyosin covers the myosin binding sites on actin • Troponin holds tropomyosin in place - has 3 sub-units 1. Troponin I • inhibitory 2. Troponin T • Tropomyosin binding 3. Troponin C • Calcium binding • Increase in intracellular Ca2+ levels cause Troponin C to bind to Ca2+ which exposes binding sites on actin Troponin Cross Bridge Cycling 1. Attachment of the myosin cross-bridge to actin of a thin filament 2. Movement of the cross-bridge, pulling on the thin filament – Each cross-bridge moves independently of all other cross- bridges – Asynchronous pulling action 3. Detachment of cross-bridge from the thin filament 4. Energizing the cross-bridge so it can again attach to a thin filament and repeat the cycle Cross-Bridge Cycling ATP in Muscle Metabolism Uses of ATP in Muscle Muscle Contraction Requires Contraction A Lot of ATP! • Activation of myosin • No ATP “storage” – High-energy myosin • 3 pathways for • Release of myosin head regeneration from actin molecule – Phosphagen system • Active transport of Ca2+ – Glycolysis into SR from the – Aerobic respiration sarcoplasm + ATP + H20 à ADP + pi + H + Energy Sources of ATP 1. Phosphagen System 2. Glycolysis 3. Oxidative phosphorylation Phosphagen System • Creatine – Natural produced ny the body – Made from amino acids • Creatine Phosphate – A store of high energy phosphate • Creatine Kinase – Transfers phosphate group from CP to ADP – Present at 3x higher concentration in skeletal muscle CrP + ADP + H+ ----> Cr + ATP Phosphagen System • Adenylate Kinase – A way to quickly make ATP – ADP + ADP ---- > ATP + AMP Aerobic Respiration • Primary source of ATP production for muscle during rest or light exercise • Fuel utilization by skeletal muscle – fatty acids – muscle glycogen – blood borne glucose Anaerobic Mechanisms • Oxygen consumption – Exercising muscle can consume more ATP than can be produced by aerobic respiration – Muscle cells will utilize available glucose and glycogen reserves – Glycolysis will then produce ATP to keep up with the demand of the active muscle • Lactic acid accumulates – Oxygen Debt • The amount of oxygen consumed to get the muscle cells and plasma back to normal conditions – Glucose levels – Glycogen reserves – Converting lactic acid back to pyruvic acid Smooth Muscle • single cells, no striations • circular layer arrangement • no sarcomeres or troponin • actin:myosin ratio = 13:1 • utilizes Ca2+/calmodulin mechanism • graded depolarizations • single unit vs multi-unit • autonomic innervation Smooth Muscle.
Load more

Recommended publications
  • Microanatomy of Muscles
    Microanatomy of Muscles Anatomy & Physiology Class Three Main Muscle Types Objectives: By the end of this presentation you will have the information to: 1. Describe the 3 main types of muscles. 2. Detail the functions of the muscle system. 3. Correctly label the parts of a myocyte (muscle cell) 4. Identify the levels of organization in a skeletal muscle from organ to myosin. 5. Explain how a muscle contracts utilizing the correct terminology of the sliding filament theory. 6. Contrast and compare cardiac and smooth muscle with skeletal muscle. Major Functions: Muscle System 1. Moving the skeletal system and posture. 2. Passing food through the digestive system & constriction of other internal organs. 3. Production of body heat. 4. Pumping the blood throughout the body. 5. Communication - writing and verbal Specialized Cells (Myocytes) ~ Contractile Cells Can shorten along one or more planes because of specialized cell membrane (sarcolemma) and specialized cytoskeleton. Specialized Structures found in Myocytes Sarcolemma: The cell membrane of a muscle cell Transverse tubule: a tubular invagination of the sarcolemma of skeletal or cardiac muscle fibers that surrounds myofibrils; involved in transmitting the action potential from the sarcolemma to the interior of the myofibril. Sarcoplasmic Reticulum: The special type of smooth endoplasmic Myofibrils: reticulum found in smooth and a contractile fibril of skeletal muscle, composed striated muscle fibers whose function mainly of actin and myosin is to store and release calcium ions. Multiple Nuclei (skeletal) & many mitochondria Skeletal Muscle - Microscopic Anatomy A whole skeletal muscle (such as the biceps brachii) is considered an organ of the muscular system. Each organ consists of skeletal muscle tissue, connective tissue, nerve tissue, and blood or vascular tissue.
    [Show full text]
  • Skeletal Muscle Physiology
    This document was created by Alex Yartsev ([email protected]); if I have used your data or images and forgot to reference you, please email me. Skeletal Muscle Physiology First of all, which muscle is which - Skeletal muscle: o Well-developed cross-striations o Does not contract in absence of a nerve stimulus o The individual muscle fibers DO NOT connect functionally or anatomically (i.e. they don’t form a single sheet of cells, and one fiber’s action potential wont get transmitted to the next) o Generally, skeletal muscle is under voluntary control - Cardiac muscle: o Also has cross-striations o Is functionally syncytial: cells are connected well enough to conduct action potentials to one another o Can contract on its own, without stimulus (but this is under some control via the autonomic nervous system, which modulates its activity) - Smooth muscle: o Has no cross-striations o Two broad types: . VISCERAL or “unitary” smooth muscle: Functionally syncytial, action potentials propagate from cell to cell Contains pacemakers which discharge irregularly, but remains under control of the autonomic nervous system Found in most hollow viscera . MULTI-UNIT SMOOTH MUSCLE Found in the eye and some other locations Does NOT activate spontaneously SKELETAL MUSCLE ORGANIZATION - Each muscle is a bundle of fibers - Each fiber is a long, multinucleated single cell - Each fiber is surrounded by a SARCOLEMMA- the cell membrane - There are NO SYNCYTIAL BRIDGES between the cells. When one cell goes off, the others don’t follow. TRANSVERSE TUBULES: T-tubules, invaginations of SARCOLEMMA: the muscle cell membrane the sarcolemma, they form part of the T-system; the space inside is an extension of the extracellular space.
    [Show full text]
  • Back-To-Basics: the Intricacies of Muscle Contraction
    Back-to- MIOTA Basics: The CONFERENCE OCTOBER 11, Intricacies 2019 CHERI RAMIREZ, MS, of Muscle OTRL Contraction OBJECTIVES: 1.Review the anatomical structure of a skeletal muscle. 2.Review and understand the process and relationship between skeletal muscle contraction with the vital components of the nervous system, endocrine system, and skeletal system. 3.Review the basic similarities and differences between skeletal muscle tissue, smooth muscle tissue, and cardiac muscle tissue. 4.Review the names, locations, origins, and insertions of the skeletal muscles found in the human body. 5.Apply the information learned to enhance clinical practice and understanding of the intricacies and complexity of the skeletal muscle system. 6.Apply the information learned to further educate clients on the importance of skeletal muscle movement, posture, and coordination in the process of rehabilitation, healing, and functional return. 1. Epithelial Four Basic Tissue Categories 2. Muscle 3. Nervous 4. Connective A. Loose Connective B. Bone C. Cartilage D. Blood Introduction There are 3 types of muscle tissue in the muscular system: . Skeletal muscle: Attached to bones of skeleton. Voluntary. Striated. Tubular shape. Cardiac muscle: Makes up most of the wall of the heart. Involuntary. Striated with intercalated discs. Branched shape. Smooth muscle: Found in walls of internal organs and walls of vascular system. Involuntary. Non-striated. Spindle shape. 4 Structure of a Skeletal Muscle Skeletal Muscles: Skeletal muscles are composed of: • Skeletal muscle tissue • Nervous tissue • Blood • Connective tissues 5 Connective Tissue Coverings Connective tissue coverings over skeletal muscles: .Fascia .Tendons .Aponeuroses 6 Fascia: Definition: Layers of dense connective tissue that separates muscle from adjacent muscles, by surrounding each muscle belly.
    [Show full text]
  • Structure of a Skeletal Muscle
    STRUCTURE OF A SKELETAL MUSCLE Skeletal muscles are not made of muscle cells alone • Skeletal muscle contains blood vessels that supply muscle cells with oxygen and glucose, and remove wastes, and nerves that coordinate muscle contraction • 1 § Each individual muscle cell (fiber) is surrounded by the _____________ § Several muscle cells are bundled together into a _________ by the _____________ § All fascicles that make up a muscle are, in turn, enclosed by the _____________ § Interconnected connective tissues taper down and connect to tendons or other connective tissues; attach muscle to bone or other structure to be moved Figure 9.1 Position and structure of a skeletal muscle. 2 FUNCTIONS OF SKELETAL MUSCLES • Muscle contractions are involved in more than just movement of bones at a joint: § § Contraction of diaphragm muscle is a vital function associated with respiratory system § _________________ – sitting, standing, holding head upright § Skeletal muscles attached to facial skin allow for facial expression; muscles in throat assist with swallowing § Sphincters composed of skeletal muscle allow conscious control over opening and closing of body openings § Support of soft tissue – abdominal walls, pelvic floor 3 • Functional groups of muscles: generally takes cooperation of several individual muscles working as a group to perform a movement or action § __________________ provide most force for a given muscle action § _____________have opposite action of agonist; allows for modulation and control of agonist movement § _____________aid agonists by supplying supplemental force, minimizing unwanted movement, and by helping to stabilize joints § _____________also provide stabilizing force that anchors a bone; protection from injury due to unnecessary movements Figure 9.3 Functional groups of muscles.
    [Show full text]
  • Muscle Physiology Dr
    Muscle Physiology Dr. Ebneshahidi Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle Figure 9.2 (a) Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Functions of the muscular system . 1. Locomotion . 2. Vasoconstriction and vasodilatation- constriction and dilation of blood vessel Walls are the results of smooth muscle contraction. 3. Peristalsis – wavelike motion along the digestive tract is produced by the Smooth muscle. 4. Cardiac motion . 5. Posture maintenance- contraction of skeletal muscles maintains body posture and muscle tone. 6. Heat generation – about 75% of ATP energy used in muscle contraction is released as heat. Copyright. © 2004 Pearson Education, Inc., publishing as Benjamin Cummings . Striation: only present in skeletal and cardiac muscles. Absent in smooth muscle. Nucleus: smooth and cardiac muscles are uninculcated (one nucleus per cell), skeletal muscle is multinucleated (several nuclei per cell ). Transverse tubule ( T tubule ): well developed in skeletal and cardiac muscles to transport calcium. Absent in smooth muscle. Intercalated disk: specialized intercellular junction that only occurs in cardiac muscle. Control: skeletal muscle is always under voluntary control‚ with some exceptions ( the tongue and pili arrector muscles in the dermis). smooth and cardiac muscles are under involuntary control. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Innervation: motor unit . a) a motor nerve and a myofibril from a neuromuscular junction where gap (called synapse) occurs between the two structures. at the end of motor nerve‚ neurotransmitter (i.e. acetylcholine) is stored in synaptic vesicles which will release the neurotransmitter using exocytosis upon the stimulation of a nerve impulse. Across the synapse the surface the of myofibril contains receptors that can bind with the neurotransmitter.
    [Show full text]
  • The Ubiquitin Proteasome System in Neuromuscular Disorders: Moving Beyond Movement
    International Journal of Molecular Sciences Review The Ubiquitin Proteasome System in Neuromuscular Disorders: Moving Beyond Movement 1, , 2, 3,4 Sara Bachiller * y , Isabel M. Alonso-Bellido y , Luis Miguel Real , Eva María Pérez-Villegas 5 , José Luis Venero 2 , Tomas Deierborg 1 , José Ángel Armengol 5 and Rocío Ruiz 2 1 Experimental Neuroinflammation Laboratory, Department of Experimental Medical Science, Lund University, Sölvegatan 19, 221 84 Lund, Sweden; [email protected] 2 Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Sevilla/Instituto de Biomedicina de Sevilla-Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41012 Sevilla, Spain; [email protected] (I.M.A.-B.); [email protected] (J.L.V.); [email protected] (R.R.) 3 Unidad Clínica de Enfermedades Infecciosas, Hospital Universitario de Valme, 41014 Sevilla, Spain; [email protected] 4 Departamento de Especialidades Quirúrgicas, Bioquímica e Inmunología, Facultad de Medicina, 29071 Universidad de Málaga, Spain 5 Departamento de Fisiología, Anatomía y Biología Celular, Universidad Pablo de Olavide, 41013 Sevilla, Spain; [email protected] (E.M.P.-V.); [email protected] (J.Á.A.) * Correspondence: [email protected] These authors contributed equally to the work. y Received: 14 July 2020; Accepted: 31 August 2020; Published: 3 September 2020 Abstract: Neuromuscular disorders (NMDs) affect 1 in 3000 people worldwide. There are more than 150 different types of NMDs, where the common feature is the loss of muscle strength. These disorders are classified according to their neuroanatomical location, as motor neuron diseases, peripheral nerve diseases, neuromuscular junction diseases, and muscle diseases. Over the years, numerous studies have pointed to protein homeostasis as a crucial factor in the development of these fatal diseases.
    [Show full text]
  • Regional Heterogeneity in Muscle Fiber Strain: the Role of Fiber Architecture
    UC Irvine UC Irvine Previously Published Works Title Regional heterogeneity in muscle fiber strain: the role of fiber architecture. Permalink https://escholarship.org/uc/item/125212ss Authors Azizi, E Deslauriers, Amber R Publication Date 2014 DOI 10.3389/fphys.2014.00303 Peer reviewed eScholarship.org Powered by the California Digital Library University of California PERSPECTIVE ARTICLE published: 12 August 2014 doi: 10.3389/fphys.2014.00303 Regional heterogeneity in muscle fiber strain: the role of fiber architecture E. Azizi* and Amber R. Deslauriers Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA, USA Edited by: The force, mechanical work and power produced by muscle fibers are profoundly affected Emma F.Hodson-Tole, Manchester by the length changes they undergo during a contraction. These length changes are in turn Metropolitan University, UK affected by the spatial orientation of muscle fibers within a muscle (fiber architecture). Reviewed by: Therefore any heterogeneity in fiber architecture within a single muscle has the potential Boris Prilutsky, Georgia Institute of Technology, USA to cause spatial variation in fiber strain. Here we examine how the architectural variation Glen Lichtwark, The University of within a pennate muscle and within a fusiform muscle can result in regional fiber strain Queensland, Australia heterogeneity. We combine simple geometric models with empirical measures of fiber *Correspondence: strain to better understand the effect of architecture on fiber strain heterogeneity. We E. Azizi, Department of Ecology and show that variation in pennation angle throughout a muscle can result in differences in Evolutionary Biology, 321 Steinhaus Hall, University of California Irvine, fiber strain with higher strains being observed at lower angles of pennation.
    [Show full text]
  • Summation of Motor Unit Force in Passive and Active Muscle Thomas G
    ARTICLE Summation of Motor Unit Force in Passive and Active Muscle Thomas G. Sandercock Department of Physiology, Northwestern University Medical School, Chicago, IL SANDERCOCK, T.G. Summation of motor unit force in passive and active muscle. Exerc. Sport Sci. Rev., Vol. 33, No. 2, pp. 76–83, 2005. Nonlinear summation of force has been observed between motor units. The complex structure of muscle suggests many reasons why this could happen. When large portions of the muscle are active, however, the nonlinearities are small, and generally explained by stretch of the common elasticity. This suggests that the type of nonlinearity observed between motor units may not be physiologically significant. Key Words: motor unit, summation, model, architecture, nonlinear INTRODUCTION the width of the length–tension curve will remain the same. This simple example suggests that the force from separate Because of the complex structure of muscle, the transmission motor units might sum linearly in a muscle with parallel of force from a single fiber to the action of the whole muscle fibers. is poorly understood. The force produced by the activation of two motor units, for example, can be more (superadditive) or less (subadditive) than the force exerted by the sum of the Force Transmission Within a Muscle two motor units when they are activated alone. There are many reasons why the force of motor units may not sum The actual structure of even the simplest muscle is more linearly. This review examines the theoretical expectations complex than the serial or parallel arrangements described and the experimental literature on the summation of motor above.
    [Show full text]
  • Motor Unit Number Estimation: a Technology and Literature Review Clifton L
    AANEM TECHNOLOGY REVIEW MOTOR UNIT NUMBER ESTIMATION: A TECHNOLOGY AND LITERATURE REVIEW CLIFTON L. GOOCH, MD,1 TIMOTHY J. DOHERTY, MD, PhD,2,3,4 K. MING CHAN, MD,5 MARK B. BROMBERG, MD, PhD,6 RICHARD A. LEWIS, MD,7 DAN W. STASHUK, PhD,8 MICHAEL J. BERGER, MD, PhD,9,10 MICHAEL T. ANDARY, MD,11 and JASPER R. DAUBE, MD12 1 Department of Neurology, University of South Florida, Tampa, Florida, USA 2 Department of Physical Medicine and Rehabilitation, University of Western Ontario, London, Ontario, Canada 3 Department of Clinical Neurological Sciences, University of Western Ontario, London, Ontario, Canada 4 Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada 5 Division of Physical Medicine and Rehabilitation/Centre for Neuroscience, University of Alberta, Edmonton, Alberta, Canada 6 Department of Neurology, University of Utah, Salt Lake City, Utah, USA 7 Department of Neurology, Cedars-Sinai, Los Angeles, California USA 8 Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada 9 School of Kinesiology, University of Western Ontario, London, Ontario, Canada 10 Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada 11 College of Osteopathic Medicine, Michigan State University, East Lansing, Michigan, USA 12 Department of Neurology, Mayo Clinic, Rochester Minnesota, USA Accepted 27 August 2014 ABSTRACT: Introduction: Numerous methods for motor unit inception of modern neuromuscular physiology. number estimation (MUNE) have been developed. The objective of this article is to summarize and compare the major methods The first motor unit number estimation (MUNE) and the available data regarding their reproducibility, validity, appli- method evolved from routine motor nerve conduc- cation, refinement, and utility.
    [Show full text]
  • Titin Force Is Enhanced in Actively Stretched Skeletal Muscle
    © 2014. Published by The Company of Biologists Ltd | The Journal of Experimental Biology (2014) 217, 3629-3636 doi:10.1242/jeb.105361 RESEARCH ARTICLE Titin force is enhanced in actively stretched skeletal muscle Krysta Powers1, Gudrun Schappacher-Tilp2, Azim Jinha1, Tim Leonard1, Kiisa Nishikawa3 and Walter Herzog1,* ABSTRACT Aubert, 1952; Edman et al., 1978; Edman et al., 1982; Morgan, 1994; The sliding filament theory of muscle contraction is widely accepted Herzog et al., 2006; Leonard and Herzog, 2010). This property, as the means by which muscles generate force during activation. termed residual force enhancement, provides a direct challenge to the Within the constraints of this theory, isometric, steady-state force sliding filament-based cross-bridge theory. produced during muscle activation is proportional to the amount of Residual force enhancement has been observed in vivo and down filament overlap. Previous studies from our laboratory demonstrated to the sarcomere level (Abbott and Aubert, 1952; Edman et al., enhanced titin-based force in myofibrils that were actively stretched 1982; Herzog and Leonard, 2002; Leonard et al., 2010; Rassier, to lengths which exceeded filament overlap. This observation cannot 2012). There are three main filaments at the sarcomere level that be explained by the sliding filament theory. The aim of the present contribute to force production in muscle: the thick (myosin), the thin study was to further investigate the enhanced state of titin during (actin), and the titin filaments. The thick filament is composed active stretch. Specifically, we confirm that this enhanced state of primarily of the protein myosin, and the thin filament is composed force is observed in a mouse model and quantify the contribution of of actin and regulatory proteins.
    [Show full text]
  • Biomechanics of Skeletal Muscle
    BiomechanicsBiomechanics ofof SkeletalSkeletal MuscleMuscle www.fisiokinesiterapia.biz ContentsContents I.I. CompositionComposition && structurestructure ofof skeletalskeletal musclemuscle II.II. MechanicsMechanics ofof MuscleMuscle ContractionContraction III.III. ForceForce productionproduction inin musclemuscle IV.IV. MuscleMuscle remodelingremodeling V.V. SummarySummary 2 MuscleMuscle types:types: –– cardiaccardiac muscle:muscle: composescomposes thethe heartheart –– smoothsmooth muscle:muscle: lineslines hollowhollow internalinternal organsorgans –– skeletalskeletal (striated(striated oror voluntary)voluntary) muscle:muscle: attachedattached toto skeletonskeleton viavia tendontendon && movementmovement SkeletalSkeletal musclemuscle 4040--45%45% ofof bodybody weightweight –– >> 430430 musclesmuscles –– ~~ 8080 pairspairs produceproduce vigorousvigorous movementmovement DynamicDynamic && staticstatic workwork –– Dynamic:Dynamic: locomotionlocomotion && positioningpositioning ofof segmentssegments –– Static:Static: maintainsmaintains bodybody postureposture 3 I.I. CompositionComposition && structurestructure ofof skeletalskeletal musclemuscle Structure & organization • Muscle fiber: long cylindrical multi-nuclei cell 10-100 μm φ fiber →endomysium → fascicles → perimysium → epimysium (fascia) • Collagen fibers in perimysium & epimysium are continuous with those in tendons • {thin filament (actin 5nm φ) + thick filament (myosin 15 nm φ )} → myofibrils (contractile elements, 1μm φ) →muscle fiber 4 5 6 BandsBands ofof myofibrilsmyofibrils
    [Show full text]
  • Skeletal Muscle Tissue and Muscle Organization
    Chapter 9 The Muscular System Skeletal Muscle Tissue and Muscle Organization Lecture Presentation by Steven Bassett Southeast Community College © 2015 Pearson Education, Inc. Introduction • Humans rely on muscles for: • Many of our physiological processes • Virtually all our dynamic interactions with the environment • Skeletal muscles consist of: • Elongated cells called fibers (muscle fibers) • These fibers contract along their longitudinal axis © 2015 Pearson Education, Inc. Introduction • There are three types of muscle tissue • Skeletal muscle • Pulls on skeletal bones • Voluntary contraction • Cardiac muscle • Pushes blood through arteries and veins • Rhythmic contractions • Smooth muscle • Pushes fluids and solids along the digestive tract, for example • Involuntary contraction © 2015 Pearson Education, Inc. Introduction • Muscle tissues share four basic properties • Excitability • The ability to respond to stimuli • Contractility • The ability to shorten and exert a pull or tension • Extensibility • The ability to continue to contract over a range of resting lengths • Elasticity • The ability to rebound toward its original length © 2015 Pearson Education, Inc. Functions of Skeletal Muscles • Skeletal muscles perform the following functions: • Produce skeletal movement • Pull on tendons to move the bones • Maintain posture and body position • Stabilize the joints to aid in posture • Support soft tissue • Support the weight of the visceral organs © 2015 Pearson Education, Inc. Functions of Skeletal Muscles • Skeletal muscles perform
    [Show full text]