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Muscles

Muscles. Skeletal Cardiac Smooth. Muscles. Specialized tissue Convert chemical energy into mechanical energy The energy obtained from nutrients Enable the muscles to contract Move different skeletal bones around joints Cardiac muscle to pump blood Smooth muscle to contract eg- GIT.

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Muscles

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  1. Muscles Skeletal Cardiac Smooth Muscles

  2. Muscles • Specialized tissue • Convert chemical energy into mechanical energy • The energy obtained from nutrients • Enable the muscles to contract • Move different skeletal bones around joints • Cardiac muscle to pump blood • Smooth muscle to contract eg- GIT Muscles

  3. Types of Muscles • There are three types of muscles • Smooth • Skeletal (striated) • Cardiac (which is also striated) Muscles

  4. Types of Muscles Cardiac Muscle Skeletal Muscle Syncytial smooth Muscle Multiunit smooth Muscle Muscles

  5. Skeletal Muscles • Structure • Muscle cell (muscle fiber) • Long cylindrical multinucleated cell • Lie parallel to each other • Force of action is directed along the fiber’s long axis • Length varies from few mm to 30 cm or more • Width is about 0.15 mm Muscles

  6. Skeletal Muscles • Level of organization • Fine layer of connective tissue (endomysium) • Wraps each muscle fiber • It separates it from neighboring fiber Endomysium Muscle fiber Perimysium Muscle fibers Muscles

  7. Skeletal Muscles • Another layer: perimysium • Surround a bundle of up to 150 muscle fibers • Fascicules • A fascia • Fibrous connective tissue surround the entire muscle Endomysium Muscle fiber Perimysium Muscle fibers Muscles

  8. Skeletal Muscles • Beneath the endomysium lie • The sarcolema • Thin elastic membrane • Enclose the fiber’s cellular contents • Contain the plasma membrane Muscles

  9. Skeletal Muscles • Plasma membrane • Conduct electrochemical wave of depolarization • Over the surface of fiber • Insulates one fibre from another during depolarization Muscles

  10. Epimysium (Connective tissue sheath) Fascicules within sheath of perimyesium Bundles of fibers. Muscles fibers are enclosed by own sheath of endomyesium Sarcoplasmic reticulum From H.Taher Sherief; Physiology Book(CD) Muscles

  11. Skeletal Muscles • Within the muscle fiber • Aqueous protoplasm (sarcoplasm) which contains • Enzymes, fat, glycogen particles • Nuclei (about 250 per mm length) • Genes, mitochondria, organelles Muscles

  12. Sarcoplasmic Reticulum Nucleus • Longitudinal network of tubular channels and vesicles • Allows the wave of depolarization • To spread from outer surface to inner environment Sarcoplasmic reticulum Myofibrils Sarcolemma Terminal cisterna (lateral sacs) Z disc sarcoplasmic reticulum (SR) Z-disc Triad Muscles

  13. Sarcoplasmic Reticulum Nucleus • Through the T tubules • To initiate muscle contraction • Contain Ca++ pump in their membrane • Pump Ca++ from sarcoplasm into vesicles Sarcoplasmic reticulum Myofibrils Sarcolemma Terminal cisterna (lateral sacs) Z disc sarcoplasmic reticulum (SR) Z-disc Triad Muscles

  14. Skeletal Muscles • Chemical composition • 75% water • 20% proteins • 5% minerals & nutrients • Salts, high energy phosphates, urea, lactate • Na+, Ca++, Mg++, Cl- phosphorous, • Fat, carbohydrate, AA Muscles

  15. Skeletal Muscles • Ultra-structure • A single multinucleated muscle fibre contain • Smaller functional units • Lie parallel to long axis • Myofibrils • Myofibrils contain even smaller units • Myofilaments • Actin • Troponin • Tropomyosin • myosin Muscles

  16. Ultra-structure MYOFIBRILS ARE MADE OF REPEATING ASSEMBLIES OF THICK AND THIN FILAMENTS Muscles

  17. Epimysium (Connective tissue sheath) Fascicules within sheath of perimyesium Bundles of fibers. Muscles fibers are enclosed by own sheath of endomyesium Sarcoplasmic reticulum Actin From H.Taher ; Physiology Book(CD) Muscles

  18. Myosin Filament • Made up of 4 protein chains • 2 myosin molecules • Double helix • Tail segment • Heavy meromysin (HMM) Light meromysin Light chains Myosin globular head Light Meromysin Tail, Heavy Meromysin (HMM) Myosin globular head LMM HMM Muscles

  19. Myosin Filament • Globular head • Cross-bridge formation • ATPase • 4 light chains • 2 associated with each myosin molecule globular heads Light chains Myosin globular head Light Meromysin Tail, Heavy Meromysin (HMM) Myosin globular head LMM HMM Muscles

  20. Myosin Filament Muscles

  21. Actin Filaments • Made up of • 2 strands of actin molecules twisted together • Double helix • Can exists as • Globular proteins • Fibrilar proteins Actin filament Tropomyosin Troponin Muscles

  22. Actin Filaments • Troponin complex • Attaches tropomyosin to actin • Tropomyosin • Covers active sites on actin Actin filament Tropomyosin Troponin Muscles

  23. Other Muscle Proteins • Others include •  -actinin distributed along Z band • -actinin found in actin filament • M protein • C protein Muscles

  24. Muscle Contraction • Pure myosin and actin • Combine to form • Actomyosin • Sliding filament theory of muscle contraction Muscles

  25. Cross bridge Z - line Z - line Sarcomere showing the region of overlap between thick and thin filaments Sarcomere shortening in response to crossbridge formation Increase in the degree of overlap RELAXED CONTRATING FULLY CONTRACTED From: Physiology textbook CD by Hassen T. Sherief Muscles

  26. Mechanism of Muscle Contraction • At rest • Interaction between actin and myosin • Prevented by troponin tropomyosin complex Active sites Inhibitor Actin filament Muscles

  27. Mechanism of Muscle Contraction • In the presence of Ca++ • Ca++ bind to troponin C • Leads to conformational change of tropomyosin • Uncovering of active sites Active sites Inhibitor Actin filament Ca++ Muscles

  28. Mechanism of Muscle Contraction • Myosin bind to actin • Bending of globular head • While still attached to actin • Moves the actin molecule Active sites Inhibitor Actin filament Muscles

  29. Mechanism of Muscle Contraction • The bending of globular head • Exposes ATP binding site • ATP bind on myosin head • Detachment from actin Active sites Inhibitor Actin filament Muscles

  30. Mechanism of Muscle Contraction • ATP is hydrolyzed to ADP and energy • ADP, energy • Incorporated into myosin head • Straightening of bent head to 900 • Ready to attach to next active sight Active sites Inhibitor Actin filament Muscles

  31. Mechanism of Muscle Contraction Muscles

  32. Muscles

  33. Excitation Contraction Coupling Muscles

  34. Muscles

  35. Excitation Contraction Coupling • Arrival of AP on motor end plate • NMJ transmission • AP along sarcolema • Spread through • T-tubules AP T-tubule AP Sarcoplasmic ret Ca++ Ca++ Mg++ Ca++/Mg++ ATPase Voltage gated channels Ca++ Ca++ Ca++ Ca++ Muscles

  36. Excitation Contraction Coupling • Opening of voltage gated • Ca++ channels • Ca++ move from • Sarcoplasmic reticulum • Into sarcoplasm •  Ca++ concentration AP T-tubule AP Sarcoplasmic ret Ca++ Ca++ Mg++ Ca++/Mg++ ATPase Voltage gated channels Ca++ Ca++ Ca++ Ca++ Muscles

  37. Actin Filaments • Ca++ bind to troponin C • Conformational change of tropomyosin • Uncovering of active sites • Actin and myosin • Crossbridge formation • Muscle contraction Actin filament Tropomyosin Troponin Active site Muscles

  38. Excitation Contraction Coupling • Relaxation occur • Active pumping of Ca++ into sarcoplasmic reticulum • Ca++/Mg++ ATPases AP T-tubule AP Sarcoplasmic ret Ca++ Ca++ Mg++ Ca++/Mg++ ATPase Voltage gated channels Ca++ Ca++ Ca++ Ca++ Muscles

  39. Actin Filaments • There is a • ↓ in the Concentration of Ca++ in the cytoplasm • Closure of active sites • relaxation Actin filament Tropomyosin Troponin Active site Muscles

  40. Excitation Contraction coupling Muscles

  41. Muscles

  42. Length – Tension Relationship Muscles

  43. Length – Tension relationship • During muscle contraction the isometric force exerted by the muscle • Depend on the • Actual length of the muscle fibers • The force developed • Related to degree of overlap between • Actin and myosin Muscles

  44. Muscles

  45. Cross-bridges • Mechanical link • Between thick and thin filament • The interaction between • Myosin head and • Actin filament • Cause the head to • Tilt towards the arm Muscles

  46. Cross-bridges • This drags the actin filament • Towards centre of the sarcomere • This is the power stroke • The number of cross bridges determine • Force produced by muscle fibre Muscles

  47. Cross-bridges • Each of the cross-bridge • Operate independently of the others • The greater the number of cross-bridges • Attaching to actin • The greater the force of contraction Muscles

  48. Cross bridge Z - line Z - line Sarcomere showing the region of overlap between thick and thin filaments Sarcomere shortening in response to crossbridge formation Increase in the degree of overlap RELAXED CONTRATING FULLY CONTRACTED From: Physiology textbook CD by Hassen T. Sherief Muscles

  49. Muscles

  50. Smooth Muscles Muscles

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