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Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 6 The Muscular System Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  T...

Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 6 The Muscular System Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The Muscular System  Muscles are responsible for all types of body movement – they contract or shorten and are the machine of the body  Three basic muscle types are found in the body  Skeletal muscle  Cardiac muscle  Smooth muscle Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.1 Characteristics of Muscles  Muscle cells are elongated (muscle cell = muscle fiber)  Contraction of muscles is due to the movement of microfilaments  All muscles share some terminology  Prefix myo refers to muscle  Prefix mys refers to muscle  Prefix sarco refers to flesh Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.2 Skeletal Muscle Characteristics  Most are attached by tendons to bones  Cells are multinucleate  Striated – have visible banding  Voluntary – subject to conscious control  Cells are surrounded and bundled by connective tissue = great force, but tires easily Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.3 Connective Tissue Wrappings of Skeletal Muscle  Endomysium – around single muscle fiber  Perimysium – around a fascicle (bundle) of fibers Figure 6.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.4a Connective Tissue Wrappings of Skeletal Muscle  Epimysium – covers the entire skeletal muscle  Fascia – on the outside of the epimysium Figure 6.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.4b Skeletal Muscle Attachments  Epimysium blends into a connective tissue attachment  Tendon – cord-like structure  Aponeuroses – sheet-like structure  Sites of muscle attachment  Bones  Cartilages  Connective tissue coverings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.5 Smooth Muscle Characteristics  Has no striations  Spindle-shaped cells  Single nucleus  Involuntary – no conscious control  Found mainly in the walls of hollow organs  Slow, sustained and tireless Figure 6.2a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.6 Cardiac Muscle Characteristics  Has striations  Usually has a single nucleus  Joined to another muscle cell at an intercalated disc  Involuntary  Found only in the heart Figure 6.2b  Steady pace! Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.7  Function of Muscles  Produce movement  Maintain posture  Stabilize joints  Generate heat Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.8 Microscopic Anatomy of Skeletal Muscle  Cells are multinucleate  Nuclei are just beneath the sarcolemma Figure 6.3a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.9a Microscopic Anatomy of Skeletal Muscle  Sarcolemma – specialized plasma membrane  Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum Figure 6.3a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.9b Microscopic Anatomy of Skeletal Muscle  Myofibril  Bundles of myofilaments  Myofibrils are aligned to give distrinct bands  I band = light band  A band = dark band Figure 6.3b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.10a Microscopic Anatomy of Skeletal Muscle  Sarcomere  Contractile unit of a muscle fiber Figure 6.3b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.10b Microscopic Anatomy of Skeletal Muscle  Organization of the sarcomere  Thick filaments = myosin filaments  Composed of the protein myosin  Has ATPase enzymes Figure 6.3c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.11a Microscopic Anatomy of Skeletal Muscle  Organization of the sarcomere  Thin filaments = actin filaments  Composed of the protein actin Figure 6.3c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.11b Microscopic Anatomy of Skeletal Muscle  Myosin filaments have heads (extensions, or cross bridges)  Myosin and actin overlap somewhat Figure 6.3d Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.12a  Properties of Skeletal Muscle Activity (single cells or fibers)  Irritability – ability to receive and respond to a stimulus  Contractility – ability to shorten when an adequate stimulus is received Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.13 Nerve Stimulus to Muscles  Skeletal muscles must be stimulated by a nerve to contract (motor neruron)  Motor unit  One neuron  Muscle cells stimulated by that neuron Figure 6.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.14 Nerve Stimulus to Muscles  Neuromuscular junctions – association site of nerve and muscle Figure 6.5b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.15a Nerve Stimulus to Muscles  Synaptic cleft – gap between nerve and muscle  Nerve and muscle do not make contact  Area between nerve and muscle is filled with interstitial fluid Figure 6.5b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.15b Transmission of Nerve Impulse to Muscle  Neurotransmitter – chemical released by nerve upon arrival of nerve impulse  The neurotransmitter for skeletal muscle is acetylcholine  Neurotransmitter attaches to receptors on the sarcolemma  Sarcolemma becomes permeable to sodium (Na+) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.16a Transmission of Nerve Impulse to Muscle  Sodium rushing into the cell generates an action potential  Once started, muscle contraction cannot be stopped Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.16b  The Sliding Filament Theory of Muscle Contraction  Activation by nerve causes myosin heads (crossbridges) to attach to binding sites on the thin filament  Myosin heads then bind to the next site of the thin filament Figure 6.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.17a The Sliding Filament Theory of Muscle Contraction  This continued action causes a sliding of the myosin along the actin  The result is that the muscle is shortened (contracted) Figure 6.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.17b  The Sliding Filament Theory Figure 6.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.18 Contraction of a Skeletal Muscle  Muscle fiber contraction is “all or none”  Within a skeletal muscle, not all fibers may be stimulated during the same interval  Different combinations of muscle fiber contractions may give differing responses  Graded responses – different degrees of skeletal muscle shortening, rapid stimulus = constant contraction or tetanus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.19 Muscle Response to Strong Stimuli  Muscle force depends upon the number of fibers stimulated  More fibers contracting results in greater muscle tension  Muscles can continue to contract unless they run out of energy Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.22 Energy for Muscle Contraction  Initially, muscles used stored ATP for energy  Bonds of ATP are broken to release energy  Only 4-6 seconds worth of ATP is stored by muscles  After this initial time, other pathways must be utilized to produce ATP Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.23 Energy for Muscle Contraction  Direct phosphorylation  Muscle cells contain creatine phosphate (CP)  CP is a high-energy molecule  After ATP is depleted, ADP is left  CP transfers energy to ADP, to regenerate ATP  CP supplies are exhausted in about 20 seconds Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.10a Slide 6.24 Energy for Muscle Contraction  Anaerobic glycolysis  Reaction that breaks down glucose without oxygen  Glucose is broken down to pyruvic acid to produce some ATP  Pyruvic acid is converted to lactic acid Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.10b Slide 6.26a Energy for Muscle Contraction  Anaerobic glycolysis (continued)  This reaction is not as efficient, but is fast  Huge amounts of glucose are needed  Lactic acid produces muscle fatigue Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.10b Slide 6.26b Energy for Muscle Contraction  Aerobic Respiration  Series of metabolic pathways that occur in the mitochondria  Glucose is broken down to carbon dioxide and water, releasing energy  This is a slower reaction that requires continuous oxygen Figure 6.10c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.25 Muscle Fatigue and Oxygen Debt  When a muscle is fatigued, it is unable to contract  The common reason for muscle fatigue is oxygen debt  Oxygen must be “repaid” to tissue to remove oxygen debt  Oxygen is required to get rid of accumulated lactic acid  Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.27 Types of Muscle Contractions  Isotonic contractions  Myofilaments are able to slide past each other during contractions  The muscle shortens  Isometric contractions  Tension in the muscles increases  The muscle is unable to shorten Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.28 Muscle Tone  Some fibers are contracted even in a relaxed muscle  Different fibers contract at different times to provide muscle tone  The process of stimulating various fibers is under involuntary control Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.29 Muscles and Body Movements  Movement is attained due to a muscle moving an attached bone Figure 6.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.30a Muscles and Body Movements  Muscles are attached to at least two points  Origin – attachment to a moveable bone  Insertion – attachment to an immovable bone Figure 6.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.30b Effects of Exercise on Muscle  Results of increased muscle use  Increase in muscle size  Increase in muscle strength  Increase in muscle efficiency  Muscle becomes more fatigue resistant Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.31 Types of Ordinary Body Movements  Flexion – decreases angle of joint and brings two bones closer together  Extension- opposite of flexion  Rotation- movement of a bone in longitudinal axis, shaking head “no”  Abduction/Adduction (see slides)  Circumduction (see slides) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.32 Body Movements Figure 6.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.33  Left: Abduction – moving the leg away from the midline Right: Above – Circumduction: cone- Adduction- shaped movement, moving proximal end doesn’t toward the move, while distal end midline moves in a circle. Types of Muscles  Prime mover – muscle with the major responsibility for a certain movement  Antagonist – muscle that opposes or reverses a prime mover  Synergist – muscle that aids a prime mover in a movement and helps prevent rotation Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.35 Naming of Skeletal Muscles  Direction of muscle fibers  Example: rectus (straight)  Relative size of the muscle  Example: maximus (largest) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.36a Naming of Skeletal Muscles  Location of the muscle  Example: many muscles are named for bones (e.g., temporalis)  Number of origins  Example: triceps (three heads) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.36b Naming of Skeletal Muscles  Location of the muscles origin and insertion  Example: sterno (on the sternum)  Shape of the muscle  Example: deltoid (triangular)  Action of the muscle  Example: flexor and extensor (flexes or extends a bone) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.37 Head and Neck Muscles Figure 6.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.38 Trunk Muscles Figure 6.15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.39  Deep Trunk and Arm Muscles Figure 6.16 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.40 Muscles of the Pelvis, Hip, and Thigh Figure 6.18c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.41 Muscles of the Lower Leg Figure 6.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.42 Superficial Muscles: Anterior Figure 6.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.43 Superficial Muscles: Posterior Figure 6.21 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6.44  Disorders relating to the Muscular System Muscular Dystrophy: inherited, muscle enlarge due to increased fat and connective tissue, but fibers degenerate and atrophy Duchenne MD: lacking a protein to maintain the sarcolemma Myasthemia Gravis: progressive weakness due to a shortage of acetylcholine receptors