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10. Skeletal Muscle Tissue. I. Muscle. A. Muscle = a Latin word for “ little mouse ” 1. skeletal muscle 2. cardiac muscle tissue 3. smooth muscle tissue. Properties of Muscle Tissue. Contractility ► Myofilaments are responsible for shortening of muscles cells

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Skeletal Muscle Tissue

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    1. 10 Skeletal Muscle Tissue

    2. I. Muscle A. Muscle = a Latin word for “little mouse” 1. skeletal muscle 2. cardiac muscle tissue 3. smooth muscle tissue

    3. Properties of Muscle Tissue Contractility ► Myofilaments are responsible for shortening of muscles cells ► Actin and myosin are two type of myofilaments Excitability ► Nerve signals excite muscle cells Extensibility ► Contraction of a skeletal muscle stretches the opposing muscle ► Smooth muscle is stretched by substances within that hollow organ ► Food in stomach; urine in urinary bladder Elasticity ► Recoils after being stretched

    4. II. Terminology Specific to Muscle Tissue A. Myo- and mys- - prefixes meaning “muscle” B. Sarco—prefix meaning “flesh” 1. Sarcolemma - plasma membrane of muscle cells 2. sarcoplasm—cytoplasm of muscle cells

    5. III. Functions of Muscle Tissue A. Produce movement 1. skeletal muscle - attached to skeleton (movement) e.g. biceps, triceps 2. smooth muscle - squeezes fluids through hollow organs e.g. walls of intestines and arteries B. Maintain posture and stabilize joints 1. enables the body to remain sitting or standing 2. muscle tone helps stabilize many synovial joints

    6. C. Heat generation 1. muscle contractions produce heat 2. helps maintain normal body temperature

    7. IV. Types of Muscle Tissue A. Skeletal muscle tissue 1. packaged into skeletal muscles 2. makes up 40% of body weight 3. cells are striated 4. innervated by voluntary division of the nervous system

    8. C. Cardiac muscle tissue 1. occurs only in the walls of the heart 2. cells are striated 3. contraction is involuntary D. Smooth muscle tissue 1. occupies the walls of hollow organs 2. cells lack striations 3. innervated by involuntary division of the nervous system

    9. V. Gross Anatomy of a Skeletal Muscle A. Sheaths of connective tissue 1. epimysium - surrounding entire muscle 2. perimysium - surrounds each fascicle (bundle of fibers) 3. endomysium - wrapping each muscle cell

    10. Epimysium Epimysium Bone Perimysium Endomysium Tendon Muscle fiberin middle ofa fascicle Blood vessel Fascicle(wrapped by perimysium) Endomysium(between individualmuscle fibers) Epimysium Perimysium Fascicle Endomysium Muscle fiber

    11. B. Each skeletal muscle supplied by branches of ► one nerve ► one artery ► one or more veins C. Nerves and vessels branch repeatedly D. Smallest branches serve individual muscle fibers E. Muscle attachments ► origin - less movable attachment ► insertion - more movable attachment

    12. Muscle contracting Origin Stable Insertion moving

    13. F. Muscles attach by connective tissue (CT) 1. fleshy attachments - CT fibers are short 2. indirect attachments - CT forms a tendon or aponeurosis G. Bone markings present where tendons meet bones ► tubercles ► trochanters ► crests

    14. H. skeletal muscle cell (fiber) 1. fibers are long and cylindrical ► Are huge cells—diameter is 10–100 µm ► Length—several centimeters to dozens of centimeters 2. cells are multinucleate 3. nuclei are peripherally located

    15. Muscle >>> Fascicle >>> Muscle Cell >>> Myofibril Myofibrils ► Are long rods within cytoplasm ► Make up 80% of the cytoplasm ► Are a specialized contractile organelle found in muscle tissue ►Are a long row of repeating segments called sarcomeres

    16. Muscle Cell >>> Myofibril Sarcolemma Muscle cell  Mitochondrion Myofibril Light I band Dark A band Nucleus

    17. Myofibril >>> Sarcomeres Thin (actin)filament Z disc H zone Z disc Thick (myosin)filament I band A band I band M line Sarcomere

    18. VI. Sarcomeres A. Basic unit of contraction of skeletal muscle Z line - boundaries of each sarcomere ► Thin (actin) filaments—from Z disc to center of the sarcomere ► Thick (myosin) filaments—located in the center of the sarcomere A bands - full length of the thick filament H zone - center part of A band where no thin filaments occur M line - in center of H zone I band - region with only thin filaments

    19. muscle cell Sarcolemma Mitochondrion Myofibril Light I band Dark A band Nucleus

    20. myofibril Thin (actin)filament Z disc H zone Z disc Thick (myosin)filament I band A band I band M line Sarcomere

    21. sarcomere Z disc M line Z disc Thin (actin)filament Elastic (titin)filaments Thick (myosin)filament Myosin heads

    22. VII. Sarcoplasmic Reticulum and T Tubules A. Sarcoplasmic reticulum 1. specializedsmooth ER 2. contains calcium ions - released when muscle is stimulated 3. calcium ions diffuse through cytoplasm ► Trigger the sliding filament mechanism B. T tubules - deep invaginations of sarcolemma

    23. Sarcoplasmic Reticulum and T Tubules Part of a skeletalmuscle fiber (cell) I band A band I band Z disc Z disc H zone Mline Sarcolemma Myofibril Sarcolemma T Tubules ofthe sarcoplasmicreticulum Myofibrils

    24. VIII. Mechanism of Contraction A. Two major types of contraction 1. Concentric contraction – force as muscle shortens 2. Eccentric contraction - force as muscle lengthens

    25. Sliding Filament Mechanism of Contraction Thick (myosin)filament Thin (actin)filament Thin (actin)filament Myosinheads Thick (myosin)filament Thin (actin) filament Movement Myosinhead Thick (myosin) filament

    26. 1 2 Sliding Filament Mechanism of Contraction Fully relaxed sarcomere of a muscle fiber Fully contracted sarcomere of a muscle fiber Z Z Z Z H A I I A I I

    27. Muscle >>> muscle fiber

    28. muscle fiber >>> myofibril >>> sarcomere

    29. sarcomere

    30. IX. Innervation of Skeletal Muscle A. Motor neurons innervate skeletal muscle tissue 1. neuromuscular junction - nerve ending meets muscle fiber 2. Terminal boutons (axon terminals) ► Located at ends of axons ► Store neurotransmitters 3. Synaptic cleft - between axon terminal and sarcolemma

    31. neuromuscular junction Terminal bouton of nerve Synapticcleft Terminalcistern of SR Triad Muscle fiber

    32. Motor unit = motor neuron and muscle cells innervated Spinal cord neuromuscularjunctions Branching axonto motor unit Motorunit 1 Motorunit 2 Nere Motor neuroncell body Motorneuronaxon Muscle Musclefibers

    33. X. Types of Skeletal Muscle Fibers A. Skeletal muscle fibers categorized according to two characteristics 1. how they manufacture energy (ATP) 2. how quickly they contract B. Oxidative fibers - produce ATP aerobically C. Glycolytic fibers - produce ATP anaerobically by glycolysis

    34. D. Slow oxidative fibers ► Red slow oxidative fibers E. Fast glycolytic fibers ► White fast glycolytic fibers F. Fast oxidative fibers ► Intermediate fibers

    35. G. Slow oxidative fibers ► Contract slowly and resistant to fatigue ► Red color due to abundant myoglobin ► Obtain energy from aerobic metabolic reactions ► Contain a large number of mitochondria ► Richly supplied with capillaries ► Fibers are small in diameter

    36. H. Fast glycolytic fibers ► Contract rapidly and tire quickly ► Contain little myoglobin and few mitochondria ► About twice the diameter of slow oxidative fibers ► Contain more myofilaments and generate more power ► Depend on anaerobic pathways

    37. I. Fast oxidative fibers ► Contract quickly like fast glycolytic fibers ► Somewhat fatigue resistant ► Have an intermediate diameter ► Are oxygen dependent ► Have high myoglobin content and rich supply of capillaries ► More powerful than slow oxidative fibers

    38. Skeletal vs. Cardiac vs. Smooth Muscle

    39. Skeletal vs. Cardiac vs. Smooth Muscle

    40. Skeletal vs. Cardiac vs. Smooth Muscle

    41. Skeletal vs. Cardiac vs. Smooth Muscle

    42. XI. Disorders of Muscle Tissue A. Muscular dystrophy 1. a group of inherited muscle destroying disease ► Affected muscles enlarge with fat and connective tissue ► Muscles degenerate ► Types of muscular dystrophy a. Duchenne muscular dystrophy b. Myotonic dystrophy

    43. B. Fibromyalgia ► A mysterious chronic-pain syndrome ► Affects mostly women Symptoms fatigue sleep abnormalities severe musculoskeletal pain headache

    44. 3 2 1 XII. Formation of Skeletal Muscle Cell Myotube(immaturemultinucleatemuscle fiber) Embryonicmesoderm cells Myoblasts Satellite cell Matureskeletalmusclefiber