Muscle System B

1. Muscle System B Ch 9

4. Sarcolemma • Cell membrane of the muscle fiber • Responds to motor neurons • Conducts contraction signals

5. Sarcoplasm • Muscle cytoplasm • Contains organelles • Mitochondria • High concentration • Nuclei • Multiple • Peripheral • Transverse tubules • Sarcoplasmic reticulum • Myofibrils

6. Peripheral Nuclei

7. Transverse Tubule • Invagination of sarcolemma into the cell • Communicate with all myofibrils • Conducts action potential to cell interior • Distributes contraction signals throughout cell • Communication efficiency • Coordination of muscle contraction • Fluid filled • Specialized interaction with endoplasmic reticulum • Sarcoplasmic reticulum

8. Invagination of Sarcolemma

9. Communicates with Sarcoplasmic Reticulum

10. Sarcoplasmic Reticulum • Specialized Endoplasmic Reticulum • Stores & releases calcium • Terminal Cisternae • Enlarged region of SR • Stores & releases the majority of Ca+ • Connects with T-tubule to form Triad • Arrangement of SR & T-tubule

11. Sarcoplasmic Reticulum

12. Terminal Cisternae

13. Triad

14. Myofibril Structure • Protein filaments & motor proteins used in muscle contraction • Myofilament • bundles of protein filaments • Highly organized microfilaments • Work in conjunction with motor proteins • 100-1000+ of myofilaments per myofibril • Change orientation to produce muscle contraction • Active unit • Use ATP

15. Myofilament • 2 types fibers • Actin- thin filaments • Primarily actin protein • Contain active site • Myosin- thick filaments • Primarily myosin protein • Contain myosin heads • Motor proteins- active site • Tropomyosin • Troponin

16. Actin Strands with Motor Proteins

17. Myosin Strands

18. Mysosin Heads

20. Myofilament Organization • Parallel overlapping arrangement • Organization produces striation pattern • Arranged in sarcomeres

21. Parallel

22. Overlapping

23. 3 Dimensional

24. Sarcomere • Unit of myofilaments • Comprised of thick & thin fibers • Functional contractile unit • Sarcomere changes length • Protein fibers that make up sarcomere do not change length • 1000s+ make up myofibril • Each contract in coordination with other sarcomeres to create muscle contraction • Distinct organization patterns

25. Sarcomere

26. Sarcomere Structure • Overlapping fibers with thick filaments in the center & thin filaments on either side • Z line • Protein ends mark boundary of sacromere • Thin filaments attach here • M line • Connect thick filaments • A band • Thick & thin filaments • I band • Thin filaments only • H band • Gap between thin filaments

27. I band • Isotropic • Thick light outer band • Comprised of only thin filaments • Gets smaller during contraction

28. A Band • Anisotropic • An= not • Thick dark central band • Comprised of both thick & thin filaments • Remains the same during contraction

29. Z Line • Aka Z Disc, Zwischen Scheibe • Zwischen= disc Scheibe= inside • Dark, outer boundary of sarcomere • Region of interlocking thin filaments • Move closer together during contraction

30. H Band • Aka H Zone • Thin, light, middle band • “middle of sarcomere” • Comprised of thick filaments only • Gets smaller during contraction

31. M Line • Thin, dark, middle line • Region of interlocking thick filaments • Does not change during contraction

32. Zone of Overlap • Area where thick and thin filaments overlap • Increases during muscle contraction

34. Striation

35. http://www.youtube.com/watch?v=EdHzKYDxrKc&feature=player_embeddedhttp://www.youtube.com/watch?v=EdHzKYDxrKc&feature=player_embedded

36. Muscle Contractions • Cumulative shortening of each sarcomere • Actions of myofilaments & motor proteins cause filaments to move against each other in a sliding fashion • Sliding Filament Theory • Coordinated movements • Occur in unique sequence of events triggered by electrical signal

37. Response Conduction Contraction

38. Response • Responds to motor neurons • Neuromuscular junction • Site of communication with motor nerves • motor end plates • Motor end plates • High density of receptors • Respond to nerve signal • Neurotransmitters • Ex Ach: Acetylcholine

39. http://www.youtube.com/watch?v=ZscXOvDgCmQ&feature=related

40. Conducts • Conducts contraction signals to myofibrils in sarcoplasm • Signal is an electrical current • Action potential • Region of specialization to maximize communication efficiency • Transverse tubule (T Tubule) • Communicates signal to myofibrils

41. Contraction • Sliding Filament Theory • Contraction a result of coordinated sarcomere shortening • Sarcomere, not filaments change in length • Thin filaments slide inward across thick filaments • Slide over thick filaments • Increase zone of overlap • Produce shortening of sarcomere

42. Contraction of Sarcomere http://www.youtube.com/watch?v=Ds6f5qeLA8c&feature=related

43. “Sliding” • Interaction between thin & thick filaments • Active site • Found on thin fibers • Tropomyosin & Troponin • Will interact with myosin heads to create contraction • Connection with myosin forms cross bridge

44. Active Site

46. Cross Bridge Formation

47. Muscle Contraction Produces Force

48. Myotonia Congenita • Lack of muscle relaxation after contraction • http://www.youtube.com/watch?v=f_3Utmj4RPU&feature=fvw

50. Muscle Contraction • Uses both chemical & electrical signal • Signal received at sarcolemma and travels to the interior of the cell via T tubules • T Tubules interact with sarcoplasmic reticulum at the cisternae • Trigger release of stored calcium from triad region • Calcium binds with troponin & causes exposure of active site • Myosin cross bridge formed when myosin heads attach to exposed active site • Movement (contraction) • ATP molecule attaches to release cross bridge