1. Essentials of Human Anatomy & Physiology Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slides 6.1 – 6.17 Seventh Edition Elaine N. Marieb Chapter 6 The Muscular System Lecture Slides in PowerPoint by Jerry L. Cook

2. The Muscular System Slide 6.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Muscles are responsible for all types of body movement  Three basic muscle types are found in the body  Skeletal muscle  Cardiac muscle  Smooth muscle

3. Characteristics of Muscles Slide 6.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Muscle cells are elongated (muscle cell = muscle fiber)  Contraction of muscles is due to the movement of microfilaments  All muscles share same terminology  Prefix myo refers to muscle  Prefix mys refers to muscle  Prefix sarco refers to flesh

4. Skeletal Muscle Characteristics Slide 6.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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

5. Connective Tissue Wrappings of Skeletal Muscle Slide 6.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Endomysium – around single muscle fiber  Perimysium – the covering around a bundle of fibers Figure 6.1

6. Connective Tissue Wrappings of Skeletal Muscle Slide 6.4b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Epimysium – covers the entire skeletal muscle = “overcoat”  Fasicle –each individual bundle, is surrounded by perimysium Figure 6.1

8. Skeletal Muscle Attachments Slide 6.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Epimysium blends into a connective tissue attachment sometimes called “Facia”:  Tendon – cord-like structure  Aponeuroses – sheet-like structure  Sites of muscle attachment:  Bones  Cartilages  Connective tissue coverings

10. Smooth Muscle Characteristics Slide 6.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Has no striations  Spindle-shaped cells  Single nucleus  Involuntary – no conscious control  Found mainly in the walls of hollow organs Figure 6.2a

11. Cardiac Muscle Characteristics Slide 6.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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

12. Function of Muscles Slide 6.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Produce movement  Maintain posture  Stabilize joints  Generate heat

13. Microscopic Anatomy of Skeletal Muscle Slide 6.9a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Cells are multinucleate  Nuclei are just beneath the sarcolemma Figure 6.3a

14. Microscopic Anatomy of Skeletal Muscle Slide 6.9b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sarcolemma – specialized plasma membrane  Sarcoplasmic reticulum (SR)– specialized smooth endoplasmic reticulum, major role is to store and release calcium Figure 6.3a

15. Microscopic Anatomy of Skeletal Muscle Slide 6.10a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Myofibril – the basic unit of a muscle... individual muscle fibers  Made of bundles of myofilaments  Myofibrils are aligned to give distinct bands that make muscles look striped  I band = light band  A band = dark band Figure 6.3b

16. Microscopic Anatomy of Skeletal Muscle Slide 6.10b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sarcomere  Contractile unit of a muscle fiber: are separated by Z lines  Sarcoplasm – inner material surrounding fibers (like cytoplasm) Figure 6.3b

18. Microscopic Anatomy of Skeletal Muscle Slide 6.11a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Organization of the sarcomere:  Thick filaments = myosin filaments  Composed of the protein myosin  Has ATPase enzymes Figure 6.3c

19. Microscopic Anatomy of Skeletal Muscle Slide 6.11b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Organization of the sarcomere  Thin filaments = actin filaments  Composed of the protein actin  Anchored at Z Disc (type of membrane)  Also contains regulatory proteins that play a role in allowing or preventing myosin heads binding to actin Figure 6.3c

20. Microscopic Anatomy of Skeletal Muscle Slide 6.12a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Myosin filaments have heads (extensions, or cross bridges)  Myosin and actin overlap somewhat Figure 6.3d

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22. Microscopic Anatomy of Skeletal Muscle Slide 6.12b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  At rest, there is a bare zone that lacks actin filaments  The interconnecting tubes and sacs of Sarcoplasmic reticulum (SR) surround every fibril – for storage of calcium Figure 6.3d

23. Properties of Skeletal Muscle Activity Slide 6.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Irritability – ability to receive and respond to a stimulus  Contractility – ability to shorten when an adequate stimulus is received

24. Nerve Stimulus to Muscles Slide 6.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Skeletal muscles must be stimulated by a nerve to contract  Motor unit =  - One neuron  - and ALL Muscle cells stimulated by that neuron Figure 6.4a

25. Nerve Stimulus to Muscles Slide 6.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Neuromuscular junctions – association site of nerve and muscle Figure 6.5b

26. Nerve Stimulus to Muscles Slide 6.15b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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

27. Transmission of Nerve Impulse to Muscle Slide 6.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Neurotransmitter – chemical released by nerve upon arrival of nerve impulse  The neurotransmitter for skeletal muscle is acetylcholine

28. Steps to Muscle Contraction 1. Nerve impulse reaches nerve and neurotransmitter, Ach, is released 2. Neurotransmitter attaches to receptors on the sarcolemma 3. Sarcolemma becomes permeable to sodium (Na+) when it has enough Ach present on receptors

29. Transmission of Nerve Impulse to Muscle Slide 6.16b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  4.Sodium rushing into the cell generates an action potential (increase in + charge disrupts the chemical gradient)  5. Once started, muscle contraction cannot be stopped. This action potential travels down the sarcolemma and into the Sarcoplasm Reticulum (SR) surrounding the microfilaments.  6. When it reaches the SR, the stored calcium is released into the sarcoplasm

30. The Sliding Filament Theory of Muscle Contraction Slide 6.17a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  7. Activation by nerve causes myosin heads (crossbridges) to attach to binding sites on the thin filament (when calcium is released)  8. Myosin heads then bind to the next site of the thin filament Figure 6.7

31. The Sliding Filament Theory of Muscle Contraction Slide 6.17b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  9. This continued action causes a sliding of the myosin along the actin  10. The result is that the muscle is shortened (contracted)  11. When action potential ends, calcium ions are reabsorbed to SR, and muscles relax Figure 6.7

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