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☰ Search Explore Log in Create new account Upload × Chapter 10 Muscle Tissue 10-1 An Introduction to Muscle Tissue • Learning Outcomes • • • • 10-1 Specify the functions of skeletal muscle tissue. 10-2 Describe the organization of muscle at the tissue level. 10-3 Explain the characteristics of skeletal muscle fibers, and identify the structural components of a sarcomere. 10-4 Identify the components of the neuromuscular junction, and summarize the events involved in the neural control of skeletal muscle contraction and relaxation. 10-1 An Introduction to Muscle Tissue • Learning Outcomes • • • 10-5 Describe the mechanism responsible for tension production in a muscle fiber, and compare the different types of muscle contraction. 10-6 Describe the mechanisms by which muscle fibers obtain the energy to power contractions. 10-7 Relate the types of muscle fibers to muscle performance, and distinguish between aerobic and anaerobic endurance. 10-1 An Introduction to Muscle Tissue • Learning Outcomes © 2012 Pearson Education, Inc. • • 10-8 Identify the structural and functional differences between skeletal muscle fibers and cardiac muscle cells. 10-9 Identify the structural and functional differences between skeletal muscle fibers and smooth muscle cells, and discuss the roles of smooth muscle tissue in systems throughout the body. An Introduction to Muscle Tissue • Muscle Tissue • A primary tissue type, divided into: • • • Skeletal muscle tissue Cardiac muscle tissue Smooth muscle tissue 10-1 Functions of Skeletal Muscle Tissue • Skeletal Muscles • • • Are attached to the skeletal system Allow us to move The muscular system • Includes only skeletal muscles 10-1 Functions of Skeletal Muscle Tissue • Six Functions of Skeletal Muscle Tissue © 2012 Pearson Education, Inc. • • • • • • Produce skeletal movement Maintain posture and body position Support soft tissues Guard entrances and exits Maintain body temperature Store nutrient reserves 10-2 Organization of Muscle • Skeletal Muscle • • • • Muscle tissue (muscle cells or fibers) Connective tissues Nerves Blood vessels 10-2 Organization of Muscle • Organization of Connective Tissues • Muscles have three layers of connective tissues • • • Epimysium Perimysium Endomysium 10-2 Organization of Muscle © 2012 Pearson Education, Inc. • Epimysium • • • Exterior collagen layer Connected to deep fascia Separates muscle from surrounding tissues 10-2 Organization of Muscle • Perimysium • • Surrounds muscle fiber bundles (fascicles) Contains blood vessel and nerve supply to fascicles 10-2 Organization of Muscle • Endomysium • • • Surrounds individual muscle cells (muscle fibers) Contains capillaries and nerve fibers contacting muscle cells Contains myosatellite cells (stem cells) that repair damage 10-2 Organization of Muscle • Organization of Connective Tissues • Muscle Attachments • Endomysium, perimysium, and epimysium come together: • • At ends of muscles To form connective tissue attachment to bone matrix © 2012 Pearson Education, Inc. • I.e., tendon (bundle) or aponeurosis (sheet) 10-2 Organization of Muscle • Blood Vessels and Nerves • • Muscles have extensive vascular systems that: • • • Supply large amounts of oxygen Supply nutrients Carry away wastes Skeletal muscles are voluntary muscles, controlled by nerves of the central nervous system (brain and spinal cord) 10-3 Characteristics of Skeletal Muscle Fibers • Skeletal Muscle Cells • • • • Are very long Develop through fusion of mesodermal cells (myoblasts) Become very large Contain hundreds of nuclei 10-3 Characteristics of Skeletal Muscle Fibers • The Sarcolemma and Transverse Tubules • The sarcolemma • • The cell membrane of a muscle fiber (cell) Surrounds the sarcoplasm (cytoplasm of muscle fiber) © 2012 Pearson Education, Inc. • A change in transmembrane potential begins contractions 10-3 Characteristics of Skeletal Muscle Fibers • The Sarcolemma and Transverse Tubules • Transverse tubules (T tubules) • • • Transmit action potential through cell Allow entire muscle fiber to contract simultaneously Have same properties as sarcolemma 10-3 Characteristics of Skeletal Muscle Fibers • Myofibrils • • • • Lengthwise subdivisions within muscle fiber Made up of bundles of protein filaments (myofilaments) Myofilaments are responsible for muscle contraction Types of myofilaments: • • Thin filaments • Made of the protein actin Thick filaments • Made of the protein myosin 10-3 Characteristics of Skeletal Muscle Fibers • The Sarcoplasmic Reticulum (SR) • A membranous structure surrounding each myofibril © 2012 Pearson Education, Inc. • • • Helps transmit action potential to myofibril Similar in structure to smooth endoplasmic reticulum Forms chambers (terminal cisternae) attached to T tubules 10-3 Characteristics of Skeletal Muscle Fibers • The Sarcoplasmic Reticulum (SR) • Triad • • Is formed by one T tubule and two terminal cisternae Cisternae • • Concentrate Ca2+ (via ion pumps) Release Ca2+ into sarcomeres to begin muscle contraction 10-3 Structural Components of a Sarcomere • Sarcomeres • • • • The contractile units of muscle Structural units of myofibrils Form visible patterns within myofibrils A striped or striated pattern within myofibrils • Alternating dark, thick filaments (A bands) and light, thin filaments (I bands) 10-3 Structural Components of a Sarcomere • Sarcomeres © 2012 Pearson Education, Inc. • The A Band • • M line • • • • • The center of the A band At midline of sarcomere The H Band The area around the M line Has thick filaments but no thin filaments Zone of overlap • • The densest, darkest area on a light micrograph Where thick and thin filaments overlap 10-3 Structural Components of a Sarcomere • Sarcomeres • The I Band • • Z lines • • The centers of the I bands At two ends of sarcomere Titin • • • Are strands of protein Reach from tips of thick filaments to the Z line Stabilize the filaments 10-3 Structural Components of a Sarcomere • Thin Filaments • F-actin (filamentous actin) • Is two twisted rows of globular G-actin © 2012 Pearson Education, Inc. • • The active sites on G-actin strands bind to myosin Nebulin • Holds F-actin strands together 10-3 Structural Components of a Sarcomere • Thin Filaments • • Tropomyosin • • Is a double strand Prevents actin–myosin interaction Troponin • • • A globular protein Binds tropomyosin to G-actin Controlled by Ca2+ 10-3 Structural Components of a Sarcomere • Initiating Contraction • • • Ca2+ binds to receptor on troponin molecule Troponin–tropomyosin complex changes Exposes active site of F-actin 10-3 Structural Components of a Sarcomere • Thick Filaments • Contain about 300 twisted myosin subunits © 2012 Pearson Education, Inc. • • Contain titin strands that recoil after stretching The mysosin molecule • • Tail • Binds to other myosin molecules Head • • Made of two globular protein subunits Reaches the nearest thin filament 10-3 Structural Components of a Sarcomere • Myosin Action • During contraction, myosin heads: • • Interact with actin filaments, forming cross-bridges Pivot, producing motion 10-3 Structural Components of a Sarcomere • Sliding Filaments and Muscle Contraction • Sliding filament theory • • • Thin filaments of sarcomere slide toward M line, alongside thick filaments The width of A zone stays the same Z lines move closer together 10-3 Structural Components of a Sarcomere © 2012 Pearson Education, Inc. • Skeletal Muscle Contraction • The process of contraction • • • Neural stimulation of sarcolemma • Causes excitation–contraction coupling Muscle fiber contraction • Interaction of thick and thin filaments Tension production 10-4 Components of the Neuromuscular Junction • The Control of Skeletal Muscle Activity • The neuromuscular junction (NMJ) • • Special intercellular connection between the nervous system and skeletal muscle fiber Controls calcium ion release into the sarcoplasm 10-4 Components of the Neuromuscular Junction • Excitation–Contraction Coupling • • Action potential reaches a triad • • Releasing Ca2+ Triggering contraction Requires myosin heads to be in “cocked” position • Loaded by ATP energy © 2012 Pearson Education, Inc. 10-4 Skeletal Muscle Contraction • The Contraction Cycle • • • • • • Contraction Cycle Begins Active-Site Exposure Cross-Bridge Formation Myosin Head Pivoting Cross-Bridge Detachment Myosin Reactivation 10-4 Skeletal Muscle Contraction • Fiber Shortening • • As sarcomeres shorten, muscle pulls together, producing tension Muscle shortening can occur at both ends of the muscle, or at only one end of the muscle • This depends on the way the muscle is attached at the ends 10-4 Skeletal Muscle Relaxation • Relaxation • Contraction Duration • Depends on: • Duration of neural stimulus © 2012 Pearson Education, Inc. • • Number of free calcium ions in sarcoplasm Availability of ATP 10-4 Skeletal Muscle Relaxation • • Relaxation • • • Ca2+ concentrations fall Ca2+ detaches from troponin Active sites are re-covered by tropomyosin Rigor Mortis • • A fixed muscular contraction after death Caused when: • • Ion pumps cease to function; ran out of ATP Calcium builds up in the sarcoplasm 10-4 Skeletal Muscle Contraction and Relaxation • Summary • • • • Skeletal muscle fibers shorten as thin filaments slide between thick filaments Free Ca2+ in the sarcoplasm triggers contraction SR releases Ca2+ when a motor neuron stimulates the muscle fiber Contraction is an active process © 2012 Pearson Education, Inc. • Relaxation and return to resting length are passive 10-5 Tension Production and Contraction Types • Tension Production by Muscles Fibers • • As a whole, a muscle fiber is either contracted or relaxed Depends on: • • • The number of pivoting cross-bridges The fiber’s resting length at the time of stimulation The frequency of stimulation 10-5 Tension Production and Contraction Types • Tension Production by Muscles Fibers • Length–Tension Relationships • • • Number of pivoting cross-bridges depends on: • Amount of overlap between thick and thin fibers Optimum overlap produces greatest amount of tension • Too much or too little reduces efficiency Normal resting sarcomere length • Is 75% to 130% of optimal length 10-5 Tension Production and Contraction Types • Tension Production by Muscles Fibers © 2012 Pearson Education, Inc. • The Frequency of Stimulation • • A single neural stimulation produces: • • A single contraction or twitch Which lasts about 7–100 msec. Sustained muscular contractions • Require many repeated stimuli 10-5 Tension Production and Contraction Types • Tension Production by Muscles Fibers • Twitches • • • Latent period • • The action potential moves through sarcolemma Causing Ca2+ release Contraction phase • • Calcium ions bind Tension builds to peak Relaxation phase • • Ca2+ levels fall Active sites are covered and tension falls to resting levels 10-5 Tension Production and Contraction Types • Tension Production by Muscles Fibers • Treppe • • A stair-step increase in twitch tension Repeated stimulations immediately after relaxation phase © 2012 Pearson Education, Inc. • • Stimulus frequency <50/second Causes a series of contractions with increasing tension 10-5 Tension Production and Contraction Types • Tension Production by Muscles Fibers • Wave summation • • • Increasing tension or summation of twitches Repeated stimulations before the end of relaxation phase • Stimulus frequency >50/second Causes increasing tension or summation of twitches 10-5 Tension Production and Contraction Types • Tension Production by Muscles Fibers • • Incomplete tetanus • • Twitches reach maximum tension If rapid stimulation continues and muscle is not allowed to relax, twitches reach maximum level of tension Complete tetanus • If stimulation frequency is high enough, muscle never begins to relax, and is in continuous contraction 10-5 Tension Production and Contraction Types • Tension Production by Skeletal Muscles © 2012 Pearson Education, Inc. • Depends on: • • • Internal tension produced by muscle fibers External tension exerted by muscle fibers on elastic extracellular fibers Total number of muscle fibers stimulated 10-5 Tension Production and Contraction Types • Motor Units and Tension Production • Motor units in a skeletal muscle: • • • Contain hundreds of muscle fibers That contract at the same time Controlled by a single motor neuron 10-5 Tension Production and Contraction Types • Motor Units and Tension Production • • Recruitment (multiple motor unit summation) • In a whole muscle or group of muscles, smooth motion and increasing tension are produced by slowly increasing the size or number of motor units stimulated Maximum tension • • Achieved when all motor units reach tetanus Can be sustained only a very short time © 2012 Pearson Education, Inc. 10-5 Tension Production and Contraction Types • Motor Units and Tension Production • • Sustained tension • • Less than maximum tension Allows motor units rest in rotation Muscle tone • • • The normal tension and firmness of a muscle at rest Muscle units actively maintain body position, without motion Increasing muscle tone increases metabolic energy used, even at rest 10-5 Tension Production and Contraction Types • Motor Units and Tension Production • Contraction are classified based on pattern of tension production • • Isotonic contraction Isometric contraction 10-5 Tension Production and Contraction Types • Isotonic Contraction • • Skeletal muscle changes length • Resulting in motion If muscle tension > load (resistance): © 2012 Pearson Education, Inc. • • Muscle shortens (concentric contraction) If muscle tension < load (resistance): • Muscle lengthens (eccentric contraction) 10-5 Tension Production and Contraction Types • Isometric Contraction • • Skeletal muscle develops tension, but is prevented from changing length iso- = same, metric = measure 10-5 Tension Production and Contraction Types • Load and Speed of Contraction • • Are inversely related The heavier the load (resistance) on a muscle • • The longer it takes for shortening to begin And the less the muscle will shorten 10-5 Tension Production and Contraction Types • Muscle Relaxation and the Return to Resting Length • • Elastic Forces • • The pull of elastic elements (tendons and ligaments) Expands the sarcomeres to resting length Opposing Muscle Contractions © 2012 Pearson Education, Inc. • • Reverse the direction of the original motion Are the work of opposing skeletal muscle pairs 10-5 Tension Production and Contraction Types • Muscle Relaxation and the Return to Resting Length • Gravity • Can take the place of opposing muscle contraction to return a muscle to its resting state 10-6 Energy to Power Contractions • ATP Provides Energy For Muscle Contraction • • • Sustained muscle contraction uses a lot of ATP energy Muscles store enough energy to start contraction Muscle fibers must manufacture more ATP as needed 10-6 Energy to Power Contractions • ATP and CP Reserves • • • Adenosine triphosphate (ATP) • The active energy molecule Creatine phosphate (CP) • The storage molecule for excess ATP energy in resting muscle Energy recharges ADP to ATP © 2012 Pearson Education, Inc. • • Using the enzyme creatine kinase (CK) When CP is used up, other mechanisms generate ATP 10-6 Energy to Power Contractions • ATP Generation • Cells produce ATP in two ways • • Aerobic metabolism of fatty acids in the mitochondria Anaerobic glycolysis in the cytoplasm 10-6 Energy to Power Contractions • • Aerobic Metabolism • • • Is the primary energy source of resting muscles Breaks down fatty acids Produces 34 ATP molecules per glucose molecule Glycolysis • • • Is the primary energy source for peak muscular activity Produces two ATP molecules per molecule of glucose Breaks down glucose from glycogen stored in skeletal muscles 10-6 Energy to Power Contractions • Energy Use and the Level of Muscular Activity © 2012 Pearson Education, Inc. • • • Skeletal muscles at rest metabolize fatty acids and store glycogen During light activity, muscles generate ATP through anaerobic breakdown of carbohydrates, lipids, or amino acids At peak activity, energy is provided by anaerobic reactions that generate lactic acid as a byproduct 10-6 Energy to Power Contractions • • Muscle Fatigue • When muscles can no longer perform a required activity, they are fatigued Results of Muscle Fatigue • • • • Depletion of metabolic reserves Damage to sarcolemma and sarcoplasmic reticulum Low pH (lactic acid) Muscle exhaustion and pain 10-6 Energy to Power Contractions • The Recovery Period • • • The time required after exertion for muscles to return to normal Oxygen becomes available Mitochondrial activity resumes © 2012 Pearson Education, Inc. 10-6 Energy to Power Contractions • Lactic Acid Removal and Recycling • The Cori Cycle • • • The removal and recycling of lactic acid by the liver Liver converts lactate to pyruvate Glucose is released to recharge muscle glycogen reserves 10-6 Energy to Power Contractions • The Oxygen Debt • After exercise or other exertion: • • • The body needs more oxygen than usual to normalize metabolic activities Resulting in heavy breathing Also called excess postexercise oxygen consumption (EPOC) 10-6 Energy to Power Contractions • Heat Production and Loss • • Active muscles produce heat Up to 70% of muscle energy can be lost as heat, raising body temperature © 2012 Pearson Education, Inc. 10-6 Energy to Power Contractions • Hormones and Muscle Metabolism • • • • Growth hormone Testosterone Thyroid hormones Epinephrine 10-7 Types of Muscles Fibers and Endurance • Muscle Performance • • • Force • The maximum amount of tension produced Endurance • The amount of time an activity can be sustained Force and endurance depend on • • : The types of muscle fibers Physical conditioning 10-7 Types of Muscles Fibers and Endurance • Three Major Types of Skeletal Muscle Fibers • • • Fast fibers Slow fibers Intermediate fibers © 2012 Pearson Education, Inc. 10-7 Types of Muscles Fibers and Endurance • Fast Fibers • • • Contract very quickly Have large diameter, large glycogen reserves, few mitochondria Have strong contractions, fatigue quickly 10-7 Types of Muscles Fibers and Endurance • Slow Fibers • • • • Are slow to contract, slow to fatigue Have small diameter, more mitochondria Have high oxygen supply Contain myoglobin (red pigment, binds oxygen) 10-7 Types of Muscles Fibers and Endurance • Intermediate Fibers • • • Are mid-sized Have low myoglobin Have more capillaries than fast fibers, slower to fatigue 10-7 Types of Muscles Fibers and Endurance • Muscle Performance and the Distribution of Muscle Fibers © 2012 Pearson Education, Inc. • • • White muscles • • Mostly fast fibers Pale (e.g., chicken breast) Red muscles • • Mostly slow fibers Dark (e.g., chicken legs) Most human muscles • • Mixed fibers Pink 10-7 Types of Muscles Fibers and Endurance • • Muscle Hypertrophy • Muscle growth from heavy training • • • Increases diameter of muscle fibers Increases number of myofibrils Increases mitochondria, glycogen reserves Muscle Atrophy • Lack of muscle activity • Reduces muscle size, tone, and power 10-7 Types of Muscles Fibers and Endurance • Physical Conditioning • Improves both power and endurance • Anaerobic activities (e.g., 50-meter dash, weightlifting) © 2012 Pearson Education, Inc. • • • • Use fast fibers Fatigue quickly with strenuous activity Improved by: • Frequent, brief, intensive workouts Causes hypertrophy 10-7 Types of Muscles Fibers and Endurance • Physical Conditioning • Improves both power and endurance • • Aerobic activities (prolonged activity) • • Supported by mitochondria Require oxygen and nutrients Improves: • • Endurance by training fast fibers to be more like intermediate fibers Cardiovascular performance 10-7 Types of Muscles Fibers and Endurance • Importance of Exercise • • • • What you don’t use, you lose Muscle tone indicates base activity in motor units of skeletal muscles Muscles become flaccid when inactive for days or weeks Muscle fibers break down proteins, become smaller and weaker © 2012 Pearson Education, Inc. • With prolonged inactivity, fibrous tissue may replace muscle fibers 10-8 Cardiac Muscle Tissue • Cardiac Muscle Tissue • • Cardiac muscle cells are striated and found only in the heart Striations are similar to that of skeletal muscle because the internal arrangement of myofilaments is similar 10-8 Cardiac Muscle Tissue • Structural Characteristics of Cardiac Muscle Tissue • Unlike skeletal muscle, cardiac muscle cells (cardiocytes): • • • • • • Are small Have a single nucleus Have short, wide T tubules • Have no triads Have SR with no terminal cisternae Are aerobic (high in myoglobin, mitochondria) Have intercalated discs 10-8 Cardiac Muscle Tissue • Intercalated Discs • Are specialized contact points between cardiocytes © 2012 Pearson Education, Inc. • • Join cell membranes of adjacent cardiocytes (gap junctions, desmosomes) Functions of intercalated discs: • • • Maintain structure Enhance molecular and electrical connections Conduct action potentials 10-8 Cardiac Muscle Tissue • Intercalated Discs • Coordination of cardiocytes • Because intercalated discs link heart cells mechanically, chemically, and electrically, the heart functions like a single, fused mass of cells 10-8 Cardiac Muscle Tissue • Functional Characteristics of Cardiac Muscle Tissue • • • • Automaticity • • Contraction without neural stimulation Controlled by pacemaker cells Variable contraction tension • Controlled by nervous system Extended contraction time • Ten times as long as skeletal muscle Prevention of wave summation and tetanic contractions by cell membranes © 2012 Pearson Education, Inc. • Long refractory period 10-9 Smooth Muscle Tissue • Smooth Muscle in Body Systems • Forms around other tissues • • • • In integumentary system • Arrector pili muscles cause “goose bumps” In blood vessels and airways • Regulates blood pressure and airflow In reproductive and glandular systems • Produces movements In digestive and urinary systems • • Forms sphincters Produces contractions 10-9 Smooth Muscle Tissue • Structural Characteristics of Smooth Muscle Tissue • • • Nonstriated tissue Different internal organization of actin and myosin Different functional characteristics 10-9 Smooth Muscle Tissue • Characteristics of Smooth Muscle Cells • Long, slender, and spindle shaped © 2012 Pearson Education, Inc. • • • • • • • Have a single, central nucleus Have no T tubules, myofibrils, or sarcomeres Have no tendons or aponeuroses Have scattered myosin fibers Myosin fibers have more heads per thick filament Have thin filaments attached to dense bodies Dense bodies transmit contractions from cell to cell 10-9 Smooth Muscle Tissue • Functional Characteristics of Smooth Muscle Tissue • • • • Excitation–contraction coupling Length–tension relationships Control of contractions Smooth muscle tone 10-9 Smooth Muscle Tissue • Excitation–Contraction Coupling • • • Free Ca2+ in cytoplasm triggers contraction Ca2+ binds with calmodulin • • In the sarcoplasm Activates myosin light–chain kinase Enzyme breaks down ATP, initiates contraction © 2012 Pearson Education, Inc. 10-9 Smooth Muscle Tissue • Length–Tension Relationships • • • Thick and thin filaments are scattered Resting length not related to tension development Functions over a wide range of lengths (plasticity) 10-9 Smooth Muscle Tissue • Control of Contractions • • Multiunit smooth muscle cells • Connected to motor neurons Visceral smooth muscle cells • • Not connected to motor neurons Rhythmic cycles of activity controlled by pacesetter cells 10-9 Smooth Muscle Tissue • Smooth Muscle Tone • • Maintains normal levels of activity Modified by neural, hormonal, or chemical factors © 2012 Pearson Education, Inc. Download 1. Science 2. Biology 3. Physiology ch_10_lecture_presentation.doc 10-9 Smooth Muscle Tissue Ch10 notes Martini 9e.doc An Introduction to Muscle Tissue Muscle Tissue Muscles 10 Muscle Tissue C h a p t e r PowerPoint® Lecture Slides Chapter 8 Muscular System 8 - 1 MuscleTissue Chapter 10: Muscle Tissue Muscle Fiber 4-5 Supporting Connective Tissues Ch4 lec notes Martini 9e.doc Muscle Tissue 12-2 Neurons 4 The Tissue Level of Test 3 Study Guide.doc studylib © 2017 DMCA Report