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Skeletal Muscle Tissue

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Presentation on theme: "Skeletal Muscle Tissue"— Presentation transcript:

1 Skeletal Muscle Tissue
Chapter 10

2 Introduction Muscles are responsible for movement
Contraction & relaxation Muscles make up 40 – 50 % of a human’s total body weight

3 Characteristics of Muscle Tissue
Excitability Can receive & respond to stimuli Contractility Can shorten & thicken Extensibility Can be stretched Elasticity Can return to its original shape

4 Functions of Muscle Tissue
Motion Maintenance of posture Heat production

5 Kinds of Muscle Tissue Skeletal Muscle Cardiac Muscle Smooth Muscle

6 The Muscular System Muscle tissue = all contractile tissue
Skeletal muscle tissue Connective tissue

7 Fascia of Skeletal Muscle
Epimysium Wraps muscle Perimysium Divides muscle into bundles (fasciculi) Endomysium Separates each muscle cell Human Anatomy, 3rd edition Prentice Hall, © 2001

8 Fascia of Skeletal Muscle
FG09_01C.JPG Title: Structural Organization of Skeletal Muscle Notes: A skeletal muscle consists of bundles of muscle fibers (fascicles) enclosed within the epimysium. The fascicles are ensheathed by the perimysium, and within each fascicle the individual muscle fibers are surrounded by the endomysium. Keywords: skeletal muscles, fascicles, muscle fibers, epimysium, connective tissue, perimysium, endomysium, nuclei, mitochondria, myofibril, sarcoplasm, sarcolemma, tendon Human Anatomy, 3rd edition Prentice Hall, © 2001

9 Human Anatomy, 3rd edition
Tendons & Aponeuroses Epimysium Perimysium Endomysium Human Anatomy, 3rd edition Prentice Hall, © 2001

10 Human Anatomy, 3rd edition
Tendon Sheaths FG11_09D.JPG Title: Intrinsic Muscles, Tendons, and Ligaments of the Hand Notes: Anatomy of the right wrist and hand. (a)Posterior view. (b) Origins and insertions, posterior.(c)Origins, insertions;anterior. (d)Anterior view. (e)Plastic reconstruction, posterior. (f)Anterior view;muscle dissection. Keywords: wrist, hand, muscles, tendons, extensor indicis tendon, extensor pollicis longus, radial artery, extensor carpi radialis longus, extensor carpi radialis brevis, collateral ligament, extensor digiti minimi, extensor digitorum, dorsal interossei Human Anatomy, 3rd edition Prentice Hall, © 2001

11 Human Anatomy, 3rd edition
Nerve & Blood Supply Related to contraction Artery and 1 or 2 veins accompany each nerve Each muscle cell is in contact with capillaries Each muscle cell is in contact with a portion of a nerve cell Neuromuscular junction Human Anatomy, 3rd edition Prentice Hall, © 2001

12 Histology of Skeletal Muscle Tissue
Muscle fibers = elongated cells Sarcolemma Sarcoplasm Sarcoplasmic reticulum T tubules Triad Muscle fibers consist of myofibrils Extend length of fiber Myofibrils consist of myofilaments Thin filaments Thick filaments Human Anatomy, 3rd edition Prentice Hall, © 2001

13 Human Anatomy, 3rd edition
Myofilaments Myofilaments do not extend entire length of fiber. Stacked in compartments = sarcomeres Partitioned by Z lines A band (dark) – contains thick filaments Includes H zone, zone of overlap I band (light) – thin filaments only H zone – thick filaments only Human Anatomy, 3rd edition Prentice Hall, © 2001

14 Human Anatomy, 3rd edition
Myofilaments Thin filaments Composed mostly of actin Contain tropomyosin and troponin Double-stranded coil Thick filaments Composed mostly of myosin Rod-shaped (tail) with head Human Anatomy, 3rd edition Prentice Hall, © 2001

15 Contraction – Sliding Filament Theory
Thin filaments slide inward toward the H zone Z lines are drawn toward the A band Sarcomere shortens Lengths of myofilaments do not change Cross bridges of thick filaments connect with actin Width of the H zone gets smaller Human Anatomy, 3rd edition Prentice Hall, © 2001

16 Neuromuscular Junction
Contraction requires a stimulus An axon comes into close contact with a muscle membrane Motor end plate Acetylcholine transmits nerve impulse to the motor end plate Initiates contraction Axon terminal + motor end plate = neuromuscular junction Human Anatomy, 3rd edition Prentice Hall, © 2001

17 Human Anatomy, 3rd edition
Motor Unit Def. – motor neuron and all muscle cells it stimulates 1 motor neuron may innervate few or many muscle cells The number of muscle fibers/motor unit determines how precise a movement is. Human Anatomy, 3rd edition Prentice Hall, © 2001

18 Physiology of Contraction – Relaxed Muscle
Sarcoplasm is low in calcium ATP is bound to myosin cross bridges Tropomyosin-troponin complex is attached to actin Human Anatomy, 3rd edition Prentice Hall, © 2001

19 Physiology of Contraction – Stimulation of Muscle
Nerve impulse reaches motor end plate Neuron releases ACh Electrical charge travels along sarcolemma Electrical charge travels down T tubules Electrical charge travels to S.R. S.R. releases calcium into sarcoplasm

20 Physiology of Contraction – Activation of Myosin
Calcium binds to troponin Cross bridges form Calcium acts as an enzyme Breaks down ATP to ADP + P Myosin cross bridges move Sarcomere shortens Muscle shortens

21 Physiology of Contraction – Relaxation of Muscle
Nerve impulse ends ACh is broken down by acetylcholinesterase Calcium is actively transported back into S.R. ADP + P = ATP Binds to cross bridges Myosin cross bridges separate from actin Binding sites on actin are covered Thin myofilaments slip back to resting position Sarcomeres return to resting length Muscle fiber returns to resting length

22 Physiology of Contraction
FG09_12.JPG Title: The Events in Muscle Contraction Notes: Stepwise summary of the sequence of events in a muscle contraction from neural activation through contraction to rest. Keywords: muscle contraction, summary, motor end plate, synaptic terminal, T-tubule, action potential, receptor, sarcoplasmic reticulum, calcium, active site, cross-bridge, actin, myosin, acetylcholinesterase, relaxation Human Anatomy, 3rd edition Prentice Hall, © 2001

23 Fast, Slow, and Intermediate Muscles
Duration of contraction varies with function Fast muscles (white) More extensive SR Lack myoglobin Fewer capillaries Slow muscles (red) Smaller fibers More capillaries Lots of myoglobin

24 Disorders Fibrosis Fibrositis Fibromyalgia Muscular dystrophy
Myasthenia gravis

25 Classifications in the Muscular System

26 How Skeletal Muscles Produce Movement
Exert force on tendons Attached to articulating bones forming a joint When muscle contracts, one bone moves toward the other Attachments Origin = attachment to stationary bone Insertion = attachment to moveable bone Belly = fleshy portion of muscle between tendons

27 Arrangement of Fasciculi
Parallel Convergent Pennate Unipennate Bipennate Multipennate Circular Arrangement is correlated with the power and range of movement of a muscle.

28 Arrangement of Fasciculi
FG09_15.JPG Title: Skeletal Muscle Fiber Organization Notes: Four different arrangements of muscle fiber patterns are observed: (a) parallel, (b) convergent, (c) unipennate, (d) bipennate, (e) multipennate and (f) circular. Keywords: muscle fiber organization, fascicle, muscle, tendon, parallel muscle, convergent muscle, unipennate muscle, bipennate muscle, multipennate muscle, circular muscle Human Anatomy, 3rd edition Prentice Hall, © 2001

29 Group Actions Agonist or prime mover Antagonist Causes desired action
Effect is opposite to agonist Synergist or fixator Assists agonist

30 Lever Systems Bones = levers, joints = fulcrums
Levers are acted upon by resistance, effort Types 1st class lever - fulcrum is placed between effort and resistance 2nd class lever - fulcrum is at one end, effort is at the opposite end, resistance is in between 3rd class lever - fulcrum is at one end, resistance is at the opposite end, effort is in between Leverage is responsible for a muscle’s strength and range of movement

31 Human Anatomy, 3rd edition
Classes of Levers FG09_16.JPG Title: The Three Classes of Levers Notes: Levers are rigid structures that move on a fixed point called a fulcrum. (a) First-class lever, (b) second-class lever and (c) third-class lever. Keywords: lever, fulcrum, muscles Human Anatomy, 3rd edition Prentice Hall, © 2001

32 Naming of Skeletal Muscles
Direction of muscle fibers Location Size Number of origins Shape Origin & insertion Action

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