C h a p t e r 10 Muscle Tissue PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

An Introduction to Muscle Tissue A primary tissue type, divided into Skeletal muscle Cardiac muscle Smooth muscle Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

An Introduction to Muscle Tissue Skeletal Muscles Are attached to the skeletal system Allow us to move Each skeletal muscle cell is a single muscle fiber The muscular system Includes only skeletal muscle Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Functions of Skeletal Muscles Produce skeletal movement Maintain body position Support soft tissues Guard openings Maintain body temperature Store nutrient reserves Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Structures Organization of Connective Tissues Muscles have three layers of connective tissues Epimysium: exterior collagen layer connected to deep fascia separates muscle from surrounding tissues Perimysium: surrounds muscle fiber bundles (fascicles) contains blood vessel and nerve supply to fascicles Endomysium: surrounds individual muscle cells (muscle fibers) contains capillaries and nerve fibers contacting muscle cells contains myosatellite cells (stem cells) that repair damage Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Structures Figure 10–1 The Organization of Skeletal Muscles. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Structures Organization of Connective Tissues Muscle attachments Endomysium, perimysium, and epimysium come together: at ends of muscles to form connective tissue attachment to bone matrix i.e., tendon (bundle) or aponeurosis (sheet) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Structures Blood Vessels Muscles have extensive vascular systems that Supply large amounts of oxygen Supply nutrients Carry away wastes Nerves Skeletal muscles are voluntary muscles, controlled by nerves of the central nervous system (brain and spinal cord) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Are very long Develop through fusion of mesodermal cells (myoblasts) Become very large Contain hundreds of nuclei Possess myosatellite cells that help with repair Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Figure 10–2 The Formation of a Multinucleate Skeletal Muscle Fiber. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Figure 10–2a The Formation of a Multinucleate Skeletal Muscle Fiber. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Figure 10–2b The Formation of a Multinucleate Skeletal Muscle Fiber. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Internal Organization of Muscle Fibers The sarcolemma The cell membrane of a muscle fiber (cell) Surrounds the sarcoplasm (cytoplasm of muscle fiber) A change in transmembrane potential begins contractions Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Internal Organization of Muscle Fibers Transverse tubules (T tubules) Narrow tubes filled with extracellular fluid that are continuous with the sarcolemma and extend into the sarcoplasm at right angles. Transmit action potential through cell Allow entire muscle fiber to contract simultaneously Have same properties as sarcolemma Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Internal Organization of Muscle Fibers Myofibrils Lengthwise subdivisions within muscle fiber and encircled by transverse tubules Each skeletal muscle fiber contains hundreds to thousands of myofibrils Made up of bundles of protein filaments (myofilaments) Myofilaments responsible for muscle contraction Types of myofilaments: thin filaments: made of the protein actin thick filaments: made of the protein myosin Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Internal Organization of Muscle Fibers Sarcoplasmic reticulum (SR) A membrane complex similar to the smooth endoplasmic reticulum Forms a tubular network around each individual myofibril On either side of a T tubule, the tubules of the SR enlarge, fuse, and form expanded chambers called terminal cisternae. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Internal Organization of Muscle Fibers Sarcoplasmic reticulum (SR) The combination of a pair of terminal cisternae plus a transverse tubule is called a triad. Calcium ions are stored in the terminal cisternae of the sarcoplasmic reticulum. A muscle contraction begins when stored calcium ions are released into the sarcoplasm. These ions then diffuse into individual contractile units called sarcomeres. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Figure 10–3 The Structure of a Skeletal Muscle Fiber. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Internal Organization of Muscle Fibers Sarcomeres The contractile units of muscle Structural units of myofibrils Form visible patterns within myofibrils Muscle striations A striped or striated pattern within myofibrils: alternating dark, thick filaments (A bands) and light, thin filaments (I bands) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Internal Organization of Muscle Fibers Sarcomeres A Bands Contains the thick filaments and portions of the thin filaments Contain three subdivisions: M line Central portion of each thick filament, is connected to its neighbor by proteins of the M line. They help stabilize the positions of the thick filaments H zone Found in a resting sarcomere (not contracting) Lighter region on either side of the M line Contains thick filaments but no thin filaments Zone of Overlap Thin filaments are situated between the thick filaments Where triads are found Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Internal Organization of Muscle Fibers Sarcomeres I Bands Contains thin filaments but no thick filaments Extends from the A band of one sarcomere to the A band of the next sarcomere Contains the Z line which interconnect thin filaments of adjacent sarcomeres. Z line to Z line = sarcomere Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Internal Organization of Muscle Fibers Sarcomeres Titin: are strands of protein reach from tips of thick filaments to the Z line stabilize the filaments Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Figure 10–4a Sarcomere Structure. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Figure 10–4b Sarcomere Structure. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Figure 10–6 Levels of Functional Organization in a Skeletal Muscle. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Figure 10–6 Levels of Functional Organization in a Skeletal Muscle. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Four Thin Filament Proteins 1. F actin A twisted strand composed of two rows of 300-400 individual globular molecules of G actin. 2. Nebulin Found in the cleft between the rows of G actin molecules Holds the F actin strand together Each G actin contains an active site that can bind to myosin Under resting conditions, myosin binding is prevented by the troponin-tropomyosin complex Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Four Thin Filament Proteins 3. Tropomyosin Cover the active sites on the G actin and prevent actin-myosin interaction Double stranded protein It is bound to one molecule of troponin midway along its length 4. Troponin Consists of three globular subunits One subunit binds to tropomyosin, locking them together in the troponin-tropomyosin complex A second subunit binds to one G actin, holding the complex in place The third subunit has a receptor that binds a calcium ion. This site is empty in a resting muscle. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Figure 10–7a, b Thick and Thin Filaments. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Initiating Contraction Ca2+ binds to receptor on troponin molecule Troponin–tropomyosin complex changes Exposes active site of F-actin Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Thick Filaments Contain twisted myosin subunits 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Figure 10–7c, d Thick and Thin Filaments. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Myosin Action During contraction, myosin heads Interact with actin filaments, forming cross-bridges Pivot, producing motion Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Skeletal 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Figure 10–8a Changes in the Appearance of a Sarcomere during the Contraction of a Skeletal Muscle Fiber. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers Figure 10–8b Changes in the Appearance of a Sarcomere during the Contraction of a Skeletal Muscle Fiber. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Skeletal Muscle Fibers When a skeletal muscle fiber contracts the following happens: the H zones and I bands get smaller the zones of overlap get larger the Z lines move closer together the width of the A bands remains constant Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Neuromuscular Junction Is the location of neural stimulation Action potential (electrical signal) Travels along nerve axon Ends at synaptic terminal Synaptic terminal: releases neurotransmitter (acetylcholine or ACh) into the synaptic cleft (gap between synaptic terminal and motor end plate) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Neuromuscular Junction Figure 10–10a, b Skeletal Muscle Innervation. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Neuromuscular Junction Figure 10–10c Skeletal Muscle Innervation. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Neuromuscular Junction Figure 10–10c Skeletal Muscle Innervation. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Neuromuscular Junction The Neurotransmitter Acetylcholine or ACh Travels across the synaptic cleft Binds to membrane receptors on sarcolemma (motor end plate) Causes sodium–ion rush into sarcoplasm Is quickly broken down by enzyme (acetylcholinesterase or AChE) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Neuromuscular Junction Figure 10–10c Skeletal Muscle Innervation. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Neuromuscular Junction Action Potential Generated by increase in sodium ions in sarcolemma Travels along the T tubules Leads to excitation–contraction coupling Excitation–contraction coupling: action potential reaches a triad: releasing Ca2+ triggering contraction requires myosin heads to be in “cocked” position: loaded by ATP energy Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Contraction Cycle Five Steps of the Contraction Cycle Exposure of active sites Formation of cross-bridges Pivoting of myosin heads Detachment of cross-bridges Reactivation of myosin Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Contraction Cycle Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Contraction Cycle Step One: Once the action potential reaches the triad Calcium is released from the cisternae of the sarcoplasmic reticulum and binds to the troponin. The troponin molecule changes position, pulling the tropomyosin molecule away from the active sites on actin and allowing interaction with the energized myosin heads. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Contraction Cycle Step Two: When the active sites are exposed, the energized myosin heads bind to them, forming cross-bridges. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Contraction Cycle Step Three: At rest, the myosin head points away from the M line. When the cross-bridge forms the myosin head pivots toward the M line. This is called the power stroke. Once the head pivots, the ADP + P are released. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Contraction Cycle Step Four: When another ATP binds to the myosin head, the link between the active site on the actin molecule and the myosin head is broken. The active site is now exposed and able to form another cross-bridge. Cocking the myosin head requires energy, which is obtained by breaking down ATP into ADP + P. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Contraction Cycle Step Five: Myosin reactivation occurs when the free myosin head splits the ATP into ADP and a phosphate group. The energy released in this process is used to recock the myosin head. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Contraction Cycle Fiber Shortening Contraction Duration As sarcomeres shorten, muscle pulls together, producing tension Contraction Duration Depends on Duration of neural stimulus Number of free calcium ions in sarcoplasm Availability of ATP Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Contraction Cycle Figure 10–13 Shortening during a Contraction. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Contraction Cycle Relaxation – Steps to end a contraction Step One: Action potential generation ceases as ACh is broken down by AChE. Step Two: The sarcoplasmic reticulum reabsorbs calcium ions Step Three: When calcium concentrations approach normal resting levels calcium ions detach from the troponin troponin-tropomyosin complex returns to its normal position. tropomyosin re-covers the active sites and prevents further cross-bridge interaction. Step Four: Without cross-bridge interactions, further sliding cannot take place, and the contraction ends. Step Five: Muscle relaxation occurs, and the muscle returns passively to its resting length. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Contraction Cycle 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production The all–or–none principle As a whole, a muscle fiber is either contracted or relaxed Tension of a Single Muscle Fiber Depends on The number of pivoting cross-bridges The fiber’s resting length at the time of stimulation The frequency of stimulation Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Tension of a Single Muscle Fiber Length–tension relationship 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Figure 10–14 The Effect of Sarcomere Length on Active Tension. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Tension of a Single Muscle Fiber 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Three Phases of Twitch Latent period before contraction Begins at stimulation and lasts about 2msec Action potential sweeps across the sarcolemma, and sarcoplasmic reticulum releases calcium ions No tension produced because the contraction cycle has not begun Contraction phase Tension rises to a peak As tension rises, calcium ions are binding to troponin, active sites are exposed, and cross-bridge interactions are occurring. Relaxation phase Calcium levels fall Active sites are covered by tropomyosin, and the number of active cross-bridges declines Tension levels fall to resting levels Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Figure 10–15 The Development of Tension in a Twitch. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Treppe A stair-step increase in twitch tension Repeated stimulations immediately after relaxation phase Stimulus frequency <50/second Causes a series of contractions with increasing tension Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Tension of a Single Muscle Fiber 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Tension of a Single Muscle Fiber Incomplete tetanus Twitches reach maximum tension If rapid stimulation continues and muscle is not allowed to relax completely, twitches reach maximum level of tension Complete Tetanus If stimulation frequency is high enough, muscle never begins to relax, and is in continuous contraction Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Figure 10–16 Effects of Repeated Stimulations. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Figure 10–16 Effects of Repeated Stimulations. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Tension Produced by Whole Skeletal Muscles Depends on Internal tension produced by muscle fibers External tension exerted by muscle fibers on elastic extracellular fibers Total number of muscle fibers stimulated Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Tension Produced by Whole Skeletal Muscles Motor units in a skeletal muscle Contain hundreds of muscle fibers That contract at the same time Controlled by a single motor neuron Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Motor Unit All the muscle fibers controlled by a single motor neuron The size of the motor unit is an indication of how fine the control of movement can be. The less motor fibers controlled by a neuron the more precise movement is. (ex. Eye) The more motor fibers controlled by a neuron the less precise movement is. (ex. Leg muscles) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Recruitment The smooth, but steady, increase in muscular tension produced by increasing the number of active motor units Movement begins by activating muscle fibers that contract relatively slowly. As the movement continues, larger motor units containing faster and more powerful muscle fibers are activated, and tension rises steeply. This results in smooth motion Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Tension Produced by Whole Skeletal Muscles 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Two Types of Skeletal Muscle Contraction Isotonic Contraction Skeletal muscle changes length: resulting in motion (walking, lifting, etc) If muscle tension > load (resistance): muscle shortens (concentric contraction) If muscle tension < load (resistance): muscle lengthens (eccentric contraction) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Two Types of Skeletal Muscle Tension Isometric contraction Skeletal muscle develops tension, but is prevented from changing length Note: iso- = same, metric = measure Carrying groceries, holding a baby, holding our heads up Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Tension Production Opposing Muscle Contractions Gravity Reverse the direction of the original motion Are the work of opposing skeletal muscle pairs Gravity Can take the place of opposing muscle contraction to return a muscle to its resting state Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

ATP and 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

ATP and Muscle Contraction 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 Using the enzyme creatine phosphokinase (CPK or CK) When CP is used up, other mechanisms generate ATP Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

ATP and Muscle Contraction ATP Generation Cells produce ATP in two ways Aerobic metabolism of fatty acids in the mitochondria Anaerobic glycolysis in the cytoplasm Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

ATP and Muscle Contraction ATP Generation Aerobic metabolism Is the primary energy source of resting muscles Breaks down fatty acids to make ATP Produces 34 ATP molecules per glucose molecule Anaerobic 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

ATP and Muscle Contraction Energy Use and Muscle Activity At peak exertion Muscles lack oxygen to support mitochondria Muscles rely on glycolysis for ATP Pyruvic acid builds up, is converted to lactic acid Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

ATP and Muscle Contraction 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

ATP and Muscle Contraction The Recovery Period The time required after exertion for muscles to return to normal Oxygen becomes available Mitochondrial activity resumes Lactic acid converted back into pyruvic acid Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

ATP and Muscle Contraction The Cori Cycle The removal and recycling of lactic acid by the liver Liver converts lactic acid to pyruvic acid Glucose is released to recharge muscle glycogen reserves Oxygen Debt After exercise or other exertion The body needs more oxygen than usual to normalize metabolic activities Resulting in heavy breathing Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscle Fiber Types Three Types of Skeletal Muscle Fibers Fast fibers Slow fibers Intermediate fibers Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscle Fiber Types Three Types of Skeletal Muscle Fibers Fast fibers Contract very quickly Have large diameter, large glycogen reserves, few mitochondria Have strong contractions, fatigue quickly Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscle Fiber Types Three Types of Skeletal Muscle Fibers Slow fibers Are slow to contract, slow to fatigue Have small diameter, more mitochondria Have high oxygen supply Contain myoglobin (red pigment, binds oxygen) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscle Fiber Types Three Types of Skeletal Muscle Fibers Intermediate fibers Are mid-sized Have low myoglobin Have more capillaries than fast fibers, slower to fatigue Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscle Fiber Types Muscles and Fiber Types White muscle Red muscle Mostly fast fibers Pale (e.g., chicken breast) Red muscle Mostly slow fibers Dark (e.g., chicken legs) Most human muscles Mixed fibers Pink Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscle Fiber Types Muscle Hypertrophy Muscle Atrophy 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscle Fiber Types Physical Conditioning Improves both power and endurance Anaerobic activities (e.g., 50-meter dash, weightlifting): use fast fibers fatigue quickly with strenuous activity Improved by: frequent, brief, intensive workouts hypertrophy Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscle Fiber Types Physical Conditioning Improves both power and endurance Aerobic activities (prolonged activity): supported by mitochondria require oxygen and nutrients Improved by: repetitive training (neural responses) cardiovascular training Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscle Fiber Types 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 With prolonged inactivity, fibrous tissue may replace muscle fibers Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiac Muscle Tissue Structure of Cardiac Tissue Cardiac muscle is striated, found only in the heart Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiac Muscle Tissue Seven Characteristics of Cardiocytes 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiac Muscle Tissue Intercalated Discs Are specialized contact points between cardiocytes Join cell membranes of adjacent cardiocytes (gap junctions, desmosomes) Functions of intercalated discs Maintain structure Enhance molecular and electrical connections Conduct action potentials Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiac Muscle Tissue Figure 10–22 Cardiac Muscle Tissue. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiac Muscle Tissue Figure 10–22a Cardiac Muscle Tissue. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiac Muscle Tissue Figure 10–22c Cardiac Muscle Tissue. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiac Muscle Tissue Four Functions of Cardiac 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 Long refractory period Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Smooth Muscle Tissue Smooth Muscle in Body Systems Forms around other tissues In blood vessels Regulates blood pressure and flow In reproductive and glandular systems Produces movements In digestive and urinary systems Forms sphincters Produces contractions In integumentary system Arrector pili muscles cause “goose bumps” Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Smooth Muscle Tissue Structure of Smooth Muscle Nonstriated tissue Different internal organization of actin and myosin Different functional characteristics Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Smooth Muscle Tissue Figure 10–23a Smooth Muscle Tissue. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Smooth Muscle Tissue Figure 10–23b Smooth Muscle Tissue. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Smooth Muscle Tissue Eight Characteristics of Smooth Muscle Cells Long, slender, and spindle shaped 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Smooth Muscle Tissue Functional Characteristics of Smooth Muscle Excitation–contraction coupling Length–tension relationships Control of contractions Smooth muscle tone Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Smooth Muscle Tissue Functional Characteristics of Smooth Muscle Excitation–contraction coupling Free Ca2+ in cytoplasm triggers contraction Ca2+ binds with calmodulin (a calcium binding protein): in the sarcoplasm activates myosin light–chain kinase enables the attachment of myosin heads to actin Enzyme breaks down ATP, initiates contraction Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Smooth Muscle Tissue Functional Characteristics of Smooth Muscle Length–Tension Relationships Thick and thin filaments are scattered Resting length not related to tension development Functions over a wide range of lengths (plasticity) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Smooth Muscle Tissue Functional Characteristics of Smooth Muscle 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Smooth Muscle Tissue Functional Characteristics of Smooth Muscle Smooth muscle tone Maintains normal levels of activity Modified by neural, hormonal, or chemical factors Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings