The Muscular System

1. The Muscular System

2. <iframe width="640" height="480" src=“ http://www.youtube.com/embed/RsWNyqnHQ2I " frameborder="0" allowfullscreen></iframe> • http://www.youtube.com/watch?v=RsWNyqnHQ2I&feature=related&ytsession=Dc8XvXEVIa6JxlmzjYUJtFy9gfLDO8yui95foSrq_Qv1XLfy7x0owzXo5DhttSgy4jEyzwCtSEo9IHkV77NAH0FBoEC9cMeO3zMKDIVHWr_NzhuQ4qNJaETTnQbElW-UuPJ__TCfw09RzZTKRga9IO-5sRb7Vp6XXIsT72WhPz1R1ESTbiEPgY8iPpVlhp8SiX4OejD6dk_Ng3vcw8P9JxMXiDPDeYKSqR-1HZq3cdO9b7nY3ic3_MjmI0KlLT7HVq-XCI3ybUh24UhhouAcfAtxyqA53sC4lQPkVUaTxk0

3. http://highered.mheducation.com/sites/0072507470/student_view0/chapter9/index.htmlhttp://highered.mheducation.com/sites/0072507470/student_view0/chapter9/index.html • Animations of neuromuscular junction; action potential; myofilament; sarcomere contraction; breakdown of ATP at contraction.

4. Function of Muscles • 1. movement • a. chemical energy converted to mechanical energy. • b. pull on attached parts • c. resist motion to maintain a posture • d. body fluids

5. Function of Muscles • 2. maintain body temperature - heat production

6. Muscle Types • B. Three basic muscle types are found in the body • Skeletal muscle • Cardiac muscle • Smooth muscle

7. Skeletal Muscle • II. Structure of Skeletal Muscle • Muscle is an organ made of many tissues: • skeletal muscle, • nervous, • blood, • epithelial, • connective

8. ConnectiveTissue • A. Connective Tissue • 1. Fascia - fibrous c.t. which surrounds a muscle andholds it in position • 2. Tendon - fascia that intertwines with periosteum,thus connecting muscle to bone. • 3. Aponeuroses - sheets of c.t. that attach to coveringsof adjacent muscles

9. Connective Tissue • 4. Epimysium - surrounds a skeletal muscle • 5. Perimysium - extends inward from epimysium and separates muscle tissue into bundles of fibers (cells) called fascicles. • 6. Endomysium - surrounds each muscle fiber (cell)

10. Quiz • 1. Aponeuroses • 2. Fascia • 3. Endomysium • 4. Sarcolema • 5. Epimysium • 6. Sarcoplasm • 7. Perimysium • 8. Muscle Fiber • 9. Tendon • 10. Periostium • A. Cytoplasm • B. Around a fascicle • C. Surrounds a skeletal muscle • D. Surrounds each muscle fiber • E. On the outside of the epimysium • F. Cell Membrane • G. Surrounds a bone • H. Connects muscle to a bone • I. Attach to coverings of adjacent muscles • J. Muscle cell

11. Quiz Answers • 1. Aponeuroses • 2. Fascia • 3. Endomysium • 4. Sarcolemma • 5. Epimysium • 6. Sarcoplasm • 7. Perimysium • 8. Muscle Fiber • 9. Tendon • 10. Periosteum • I. Attach to coverings of adjacent muscles • E. On the outside of the epimysium • D. Surrounds each muscle fiber • F. Cell Membrane • C. Surrounds a skeletal muscle • A. Cytoplasm • B. Around a fascicle • J. Muscle cell • H. Connects muscle to a bone • G. Surrounds a bone

12. Connective Tissue Wrappings of Skeletal Muscle Endomysium – around single muscle fiber Perimysium – around a fascicle (bundle) of fibers Epimysium – covers the entire skeletal muscle Fascia – on the outside of the epimysium Figure 6.1

13. Characteristics of Muscles • All muscles share some terminology…… • Prefix myo refers to muscle • Prefix mys refers to muscle • Prefix sarco refers to flesh

14. MuscleFibers • B. Skeletal Muscle Fibers - each muscle fiber is a single cell • 1. cells or fibers are thin, elongated cylinders withrounded ends. • 2. sarcolemma - cell membrane • 3. sarcoplasm – cytoplasm • 4. many nuclei and mitochondria under sarcolemma

15. Microscopic Anatomy of Skeletal Muscle Observe in this picture……… • Cells are multinucleate • Nuclei are just beneath the sarcolemma Figure 6.3a

16. Microscopic Anatomy of Skeletal Muscle • Sarcolemma – specialized plasma membrane • Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum Figure 6.3a

17. Muscle Fibers • 5. Sarcoplasmic reticulum - network of channelssurrounding myofibrils • 6. Transverse tubules - channels that extend from sarcolemma through the cell and lie between cisternae • 7. Cisternae - enlarged portions of sarcoplasmic reticulum

18. Muscle Fibers • 8. Myofibrils - parallel, threadlike protein filaments • a. myosin protein - the thicker filaments • b. actin protein - the thinner filaments • c. striations - the arrangement of alternating light and dark filaments

19. Microscopic Anatomy of Skeletal Muscle Let’s Observe Myofibrils………… • Bundles of myofilaments • Myofibrils are aligned to give distinct bands • I band = light band • A band = dark band Figure 6.3b

20. Muscle Fibers • d. sarcomere - segment of myofibril (Contractile unit of muscle fiber) • (1) A bands – dark band; thick myosin filaments (and actin which overlaps) • (2) I bands – light band; only thin actin filaments • (3) Z lines - where actin filaments are attached

21. Microscopic Anatomy of Skeletal Muscle Let’s observe a Sarcomere more closely…… • Contractile unit of a muscle fiber Figure 6.3b

22. Watch video (3min) on YouTube: • http://www.youtube.com/watch?feature=player_embedded&v=XoP1diaXVCI

23. Quiz! • Actin • Cisternae • Dark Band • Light Band • Myofibrils • Myosin • Sarcolemma • Sarcomere • Sarcoplasmic Reticulum • Transverse Tubules • Z Line • Thick protein filament • Thin protein filament • I Band; only actin is present • A Band; where myosin & actin overlap • Specialized plasma membrane • Network of channels; surround myofibrils • Enlarged portions of S.R.; Ca+ reservoir • Extend from sarcolemma deep into cell • Contractile unit of a muscle fiber • Where actin filaments join • Bundle of parallel protein filaments

24. Quiz Answers  • Actin • Cisternae • Dark Band • Light Band • Myofibrils • Myosin • Sarcolemma • Sarcomere • Sarcoplasmic Reticulum • Transverse Tubules • Z Line B. Thin protein filament G. Enlarged portions of S.R.; Ca+ reservoir D. A Band; where myosin & actin overlap C. I Band; only actin is present K. Bundle of parallel protein filaments A. Thick protein filament E. Specialized plasma membrane I. Contractile unit of a muscle fiber F. Network of channels; surround myofibrils H. Extend from sarcolemma deep into cell J. Where actin filaments join

25. Skeletal Muscle Characteristics Let’s Review ………….. • 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

26. 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

27. Smooth Muscle Characteristics Let’s compare that to Smooth Muscle… (We’ll take notes on it later) • Has no striations • Spindle-shaped cells • Single nucleus • Involuntary – no conscious control • Found mainly in the walls of hollow organs Figure 6.2a

28. Nerve Stimulus to Muscles • Skeletal muscles must be stimulated by a nerve to contract Figure 6.4a

29. Properties of Skeletal Muscle Activity • Irritability – ability to receive and respond to a stimulus • Contractility – ability to shorten when an adequate stimulus is received • Let’s see how this happens in your muscles!

30. Nerve Stimulus to Muscles C. Neuromuscular Junction – connection between nerve and muscle fiber. Figure 6.5b

31. 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

32. Nerve Stimulus to Muscles • Motor Neuron- neuron that stimulates a muscle cell to contract. • Branched • Abundant mitochondria Figure 6.5b

33. Nerve Stimulus to Muscles c. Synaptic vesicles store neurotransmitters which stimulate muscle cells Figure 6.5b

34. Nerve Stimulus to Muscles • Motor End Plate- region of sarcolemma that is recessed to receive a nerve fiber a. Sarcolemma is extensively folded b. Mitochondria are abundant Figure 6.5b

35. Nerve Stimulus to Muscles • Motor unit • One neuron • Muscle cells stimulated by that neuron Figure 6.4a

36. Nerve Stimulus to Muscles • Motor units – a motor neuron and all the muscle cells that it controls 1. A neuron’s impulse stimulates all of its muscle cells simultaneously Figure 6.4a

37. Microscopic Anatomy of Skeletal Muscle Now back to the Sarcomere ……… • Contractile unit of a muscle fiber Figure 6.3b

38. Microscopic Anatomy of Skeletal Muscle • Organization of the sarcomere • Thick filaments = myosin filaments • Composed of the protein myosin • Has ATPase enzymes Figure 6.3c

39. Microscopic Anatomy of Skeletal Muscle • Organization of the sarcomere • Thin filaments = actin filaments • Composed of the protein actin • Has active sites (ADP) Figure 6.3c

40. Microscopic Anatomy of Skeletal Muscle • Myosin filaments have projections called crossbridges • Myosin and actin overlap somewhat • At rest, there is a bare zone that lacks actin filaments Figure 6.3d

41. Properties of Skeletal Muscle Activity • Irritability – ability to receive and respond to a stimulus • Contractility – ability to shorten when an adequate stimulus is received

42. 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+)

43. Transmission of Nerve Impulse to Muscle • Sodium rushing into the cell generates an action potential • Once started, muscle contraction cannot be stopped

44. The Sliding Filament Theory of Muscle Contraction • A stimulus causes Sarcoplasmic Reticulum to release Ca++ • When Ca++ is present, active sites on actin are exposed. Figure 6.7

45. The Sliding Filament Theory of Muscle Contraction • This causes myosin heads (crossbridges) to attach to active sites on actin • Myosin heads bend backward, pulling actin with it • Myosin heads then release and bind to the next active site of actin and pull it further. Figure 6.7

46. The Sliding Filament Theory of Muscle Contraction • This continued action causes a sliding of the myosin along the actin and the sarcomere is shortened • The result is that the muscle is shortened (contracted) Figure 6.7

47. The Sliding Filament Theory Figure 6.8

48. Animation Time! • Now, let’s watch a short animation that demonstrates the sliding filament theory: • https://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__myofilament_contraction.html • https://www.youtube.com/watch?v=0kFmbrRJq4w • 3 minute Video of Sliding Theory on next page.

50. Review NMJ: • Now we are ready to learn more about the stimulus for contraction but 1st …. • We need to go back and review the Neuromuscular Junction beginning with slide 29………..