1 / 65

Lecture 7: Chapter 10 Muscle Tissue Pages: 283-325

Lecture 7: Chapter 10 Muscle Tissue Pages: 283-325. Lecturer: Dr. Barjis Room: P313 /P307 Phone: (718)2605285 E-Mail: ibarjis@citytech.cuny.edu. Learning Objectives. Describe the organization of muscle and the unique characteristics of skeletal muscle cells.

cameron-morrison
Télécharger la présentation

Lecture 7: Chapter 10 Muscle Tissue Pages: 283-325

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture 7: Chapter 10 Muscle TissuePages: 283-325 Lecturer: Dr. Barjis Room: P313 /P307 Phone: (718)2605285 E-Mail: ibarjis@citytech.cuny.edu

  2. Learning Objectives • Describe the organization of muscle and the unique characteristics of skeletal muscle cells. • Identify the structural components of the sarcomere. • Summarize the events at the neuromuscular junction. • Explain the key concepts involved in skeletal muscle contraction and tension production.

  3. Learning Objectives • Describe how muscle fibers obtain energy for contraction. • Distinguish between aerobic and anaerobic contraction, muscle fiber types, and muscle performance. • Identify the differences between skeletal, cardiac and smooth muscle.

  4. Skeletal muscle tissue and the Muscular System Three types of muscle • Skeletal – attached to bone • Cardiac – found in the heart • Smooth – lines hollow organs

  5. Skeletal muscle functions • Produce skeletal movement • Maintain posture and body position • Support soft tissues • Guard entrances and exits • Maintain body temperature

  6. Anatomy of Skeletal Muscle Organization of connective tissues • Epimysium surrounds muscle • Perimysium sheathes bundles of muscle fibers • Epimysium and perimysium contain blood vessels and nerves • Endomysium covers individual muscle fibers • Tendons or aponeuroses attach muscle to bone or muscle Animation: See tutorial

  7. The Organization of Skeletal Muscles

  8. Skeletal muscle fibers • Sarcolemma (cell membrane) • Sarcoplasm (muscle cell cytoplasm) • Sarcoplasmic reticulum (modified ER) • T-tubules and myofibrils aid in contraction • Sarcomeres – regular arrangement of myofibrils

  9. The Structure of a Skeletal Muscle Fiber

  10. Sarcomere Structure, Part I

  11. Myofibrils • Thick and thin filaments • Organized regularly

  12. Sarcomere Structure, Part II

  13. Levels of Functional Organization in Skeletal Muscle Fiber

  14. Thin filaments • F-actin • Nebulin • Tropomyosin • Covers active sites on G-actin • Troponin • Binds to G-actin and holds tropomyosin in place

  15. Thick filaments • Bundles of myosin fibers around titan core • Myosin molecules have elongate tail, globular head • Heads form cross-bridges during contraction • Interactions between G-actin and myosin prevented by tropomyosin during rest

  16. Thick and Thin Filaments

  17. Sliding filament theory • Explains the relationship between thick and thin filaments as contraction proceeds • Cyclic process beginning with calcium release from SR • Calcium binds to troponin • Trponin moves, moving tropomyosin and exposing actin active site • Myosin head forms cross bridge and bends toward H zone • ATP allows release of cross bridge

  18. Changes in the appearance of a Sarcomere during the Contraction of a Skeletal Muscle Fiber

  19. The Contraction of Skeletal Muscle Tension • Created when muscles contract • Series of steps that begin with excitation at the neuromuscular junction • Calcium release • Thick/thin filament interaction • Muscle fiber contraction • Tension

  20. An Overview of the Process of Skeletal Muscle

  21. Control of skeletal muscle activity occurs at the neuromuscular junction • Action potential arrives at synaptic terminal • ACh released into synaptic cleft • ACh binds to receptors on post-synaptic neuron • Action potential in sarcolemma

  22. Skeletal Muscle Innervation

  23. Skeletal Muscle Innervation Animation: See tutorial

  24. Excitation/contraction coupling • Action potential along T-tubule causes release of calcium from cisternae of SR • Initiates contraction cycle • Attachment • Pivot • Detachment • Return

  25. The Contraction Cycle

  26. The Contraction Cycle

  27. The Contraction Cycle

  28. The Contraction Cycle

  29. Relaxation • Acetylcholinesterase breaks down ACh • Limits the duration of contraction Animation: See tutorial

  30. Tension Production Tension production by muscle fibers • All or none principle • Amount of tension depends on number of cross bridges formed • Skeletal muscle contracts most forcefully over a narrow ranges of resting lengths

  31. The Effect of Sarcomere Length on Tension

  32. Twitch • Cycle of contraction, relaxation produced by a single stimulus • Treppe • Repeated stimulation after relaxation phase has been completed

  33. Summation • Repeated stimulation before relaxation phase has been completed • Wave summation = one twitch is added to another • Incomplete tetanus = muscle never relaxes completely • Complete tetanus = relaxation phase is eleminated

  34. The Twitch and the Development of Tension

  35. Effects of Repeated Stimulations

  36. Tension production by skeletal muscles • Internal tension generated inside contracting muscle fibers • External tension generated in extracellular fibers

  37. Internal and External Tension

  38. Motor units • All the muscle fibers innervated by one neuron • Precise control of movement determined by number and size of motor unit • Muscle tone • Stabilizes bones and joints

  39. The Arrangement of Motor Units in a Skeletal Muscle

  40. Tension production by skeletal muscles • Internal tension generated inside contracting muscle fibers • External tension generated in extracellular fibers

  41. Internal and External Tension

  42. Motor units • All the muscle fibers innervated by one neuron • Precise control of movement determined by number and size of motor unit • Muscle tone • Stabilizes bones and joints

  43. The Arrangement of Motor Units in a Skeletal Muscle

  44. Contractions • Isometric • Tension rises, length of muscle remains constant • Isotonic • Tension rises, length of muscle changes • Resistance and speed of contraction inversely related • Return to resting lengths due to elastic components, contraction of opposing muscle groups, gravity Animation: See tutorial

  45. Isotonic and Isometric Contractions Figure 10.18

  46. Resistance and Speed of Contraction Animation: See tutorial

  47. Energy Use and Muscle Contraction Muscle Contraction requires large amounts of energy • Creatine phosphate releases stored energy to convert ADP to ATP • Aerobic metabolism provides most ATP needed for contraction • At peak activity, anaerobic glycolysis needed to generate ATP

  48. Muscle Metabolism

  49. Muscle Metabolism

  50. Energy use and level of muscular activity • Energy production and use patterns mirror muscle activity • Fatigued muscle no longer contracts • Build up of lactic acid • Exhaustion of energy resources

More Related