1. Essentials of Anatomy and Physiology Fifth edition Seeley, Stephens and Tate Slide 2.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 7: Muscular System

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

3. Types of Muscle Three types of muscle SkeletalCardiacSmooth

4. Functions of Skeletal Muscles Slide 6.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Make up “flesh” of the body Maintain Posture Voluntary movement Aid in breathing, eating, speech Provide facial expression Generate reflexes Produce body heat

5. Characteristics of Skeletal Muscles Slide 6.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Muscle cells are elongated (muscle cell = muscle fiber)  Muscles are specialized to contract  Terminology:  Prefix myo, mys refer to muscle  Prefix sarco refers to flesh

6. Characteristics of Skeletal Muscles 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  Muscles and their fibers are wrapped by connective tissue

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

8. Connective Tissue Wrappings of Skeletal Muscle Slide 6.4b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Epimysium – covers the entire skeletal muscle  Fascia – on the outside of the epimysium Figure 6.1

9. Skeletal Muscle Attachments Slide 6.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Epimysium blends into a connective tissue attachment  Tendon – cord-like structure  Aponeurosis – sheet-like structure

10. Skeletal Muscle Attachments Slide 6.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sites of muscle attachment  Bones  Cartilages  C. T. coverings  i.e., aponeuroses

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

12. Microscopic Anatomy Slide 6.9b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sarcolemma – specialized plasma membrane  Sarcoplasmic reticulum – specialized smooth E.R.  Stores Ca ++  Required for contraction Figure 6.3a

13. Microscopic Anatomy Slide 6.10a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Myofibril: organelle unique to muscle  Bundles of myofilaments  Myofibrils alignment produces distinct bands  I band = light band  A band = dark band

14. Microscopic Anatomy Slide 6.10a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Banding Pattern depends on arrangement of proteins in myofibrils  Actin: thin  A and I bands  Myosin: thick  A bands Figure 6.3b A-band I-band

15. Microscopic Anatomy Slide 6.10b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sarcomere  Contractile subunit of a muscle fiber  From “Z to Z”  One A band +  Two “half” I bands Figure 6.3b

16. Microscopic Anatomy 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 ATP-ase enzymes Figure 6.3c

17. Microscopic Anatomy Slide 6.11b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Organization of the sarcomere, con’t…  Thin filaments = actin filaments  Composed of the protein actin Figure 6.3c

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

19. Microscopic Anatomy Slide 6.12b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  At rest, there is a bare [“H”] zone that lacks actin filaments Figure 6.3d

20. Properties of Skeletal Muscle 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

21. Nerve Stimulus to Muscles Slide 6.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Skeletal muscles require innervation  Motor unit  One motor neuron +  Muscle cells innervated by that neuron Figure 6.4a

22. Nerve Stimulus to Muscles Slide 6.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Neuromuscular junction:  communication site between a motor neuron and a muscle fiber Figure 6.5b Motor Neuron Neuromuscular Junction

23. 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 direct contact Figure 6.5b

24. Transmission of Nerve Impulse to Muscle Slide 6.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Neurotransmitter – chemical released by motor nerve  initiates contraction  Causes sarcolemma to depolarize  For skeletal muscle: acetylcholine (Ach)

25. Transmission of Nerve Impulse to Muscle Slide 6.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Action of Neurotransmitter  Crosses synaptic cleft  Attaches to receptors on the sarcolemma

26. Muscle Contraction Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  An electrochemical event  Ach is the chemical  Before contraction can occur, sarcolemma must be polarized  A polarized membrane is more “+” outside and more “-” inside  Movement of ions creates “action potential”  The ability to do work

27. Muscle Contraction Slide 6.16b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ach attaches to receptor sites  Sarcolemma becomes permeable to sodium (Na + )  Sodium rushes into the cell  Initiates “sliding filament” process

28. Muscle Contraction Slide 6.16b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Membrane of sarcoplasmic reticulum also depolarizes Ca ++ ions are released Bind to sites on actin Open attachment sites for myosin

29. The Sliding Filament Theory of Muscle Contraction Slide 6.17a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Depolarization allows myosin heads to attach to binding sites on actin  called crossbridges  ATP required Figure 6.7

30. The Sliding Filament Theory of Muscle Contraction Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Actin is pulled past myosin by movement of heads  ATP required  Myosin heads detach  ATP required  Then bind to the next site on actin  ATP required

31. The Sliding Filament Theory of Muscle Contraction Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  This continued action causes a sliding of the actin along the myosin  I band narrows  H zone narrows  A band stays the same

32. The Sliding Filament Theory of Muscle Contraction Slide 6.17b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Actin slides past myosin  Results in shortening of the sarcomere  Muscle fiber has thousands of sarcomeres  All shorten at one time  Muscle contracts Figure 6.7