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Contractile mechanism of skeletal muscle 1
- 1. 11 Muscle Physiology Prof. Dr. Rashid Mahmood Contractile Mechanism of Skeletal Muscle I Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood Video of muscle contraction
- 2. ObjectivesObjectives Goal/Aim (Main Objective): To explain the mechanism of muscle contraction At the end of this lecture students will be able toAt the end of this lecture students will be able to Classify muscles Describe organization of skeletal muscle Describe general mechanism of skeletal muscle contraction. Describe molecular mechanism of skeletal muscle contraction. Outline different steps of Cross-bridge Cycle Explain walk along theory...
- 3. Lesson contents ClassesClasses of Muscleof Muscle Physiological AnatomyPhysiological Anatomy of Skeletal Muscleof Skeletal Muscle SarcomereSarcomere Actin & Myosin FilamentsActin & Myosin Filaments The T Tubules and Sarcoplasmic ReticulumThe T Tubules and Sarcoplasmic Reticulum Sequence of events inSequence of events in neuromuscularneuromuscular transmissiontransmission Synthesis & Release ofSynthesis & Release of AcetylcholineAcetylcholine Steps ofSteps of General mechanism of muscleGeneral mechanism of muscle contractioncontraction 33Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 4. Three Classes of MuscleThree Classes of Muscle Based on histological appearance and functionBased on histological appearance and function SkeletalSkeletal striated, voluntarystriated, voluntary CardiacCardiac striated, involuntarystriated, involuntary SmoothSmooth nonstriated, involuntarynonstriated, involuntary 44
- 5. 55 Muscle Tendon Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood Skeletal Muscle
- 6. PhysiologicalPhysiological Anatomy ofAnatomy of MuscleMuscle 77Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 7. 88 SubunitsSubunits Muscle Muscle Fiber Myofibrils Myosin Filaments Actin Filaments Muscle fasciculus Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 8. 99 Light and Dark bandsLight and Dark bands Striated Muscle Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 9. Assessment Q. 1Assessment Q. 1 Name the THREE types of MuscleName the THREE types of Muscle 1010Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 10. SarcomereSarcomere 1111Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 11. 1212 Actin + Myosin FilamentsActin + Myosin Filaments Cross- Bridges Sarcomere Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 12. 1313 SarcomereSarcomere Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 13. Proteins that help inProteins that help in alignment of Myofibrilsalignment of Myofibrils 1414Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 14. 1515 Myosin MoleculeMyosin Molecule Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 15. 1616 Myosin filamentMyosin filament Arm Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 16. 1717 Myosin Molecule & filamentMyosin Molecule & filament Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 17. Assessment Q. 2Assessment Q. 2 Name any THREE parts of MyosinName any THREE parts of Myosin FilamentFilament 1818Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 18. 1919 Actin filamentActin filament Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 19. 2020 Actin HelixActin Helix + tropomyosin+ tropomyosin +troponin+troponin == Actin FilamentActin Filament Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 20. 2121 Troponin complexTroponin complex Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 21. 2222 Binding ofBinding of myosinmyosin head withhead with active siteactive site in thein the presencepresence of Ca++of Ca++ Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 22. 2323 Mammalian Skeletal Muscle: Two Transverse Tubules per Sarcomere Z line Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 23. 2424 The T Tubules and Sarcoplasmic ReticulumThe T Tubules and Sarcoplasmic Reticulum Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 24. 2525 Relation between T Tubules andRelation between T Tubules and Sarcoplasmic ReticulumSarcoplasmic Reticulum Sarcoplasmic Reticulum=Sarcoplasmic Reticulum= Terminal Cisternae+Terminal Cisternae+ Long Longitudinal TubulesLong Longitudinal Tubules Terminal CisternaeTerminal Cisternae Long Longitudinal TubulesLong Longitudinal Tubules •T TubuleT Tubule Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 25. Assessment Q. 3Assessment Q. 3 Name the THREE parts of ActinName the THREE parts of Actin FilamentFilament 2626Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 26. 2727 StepsSteps ofof GeneralGeneral mechanismmechanism ofof muscle contractionmuscle contraction Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 27. 2828 Sequence of events inSequence of events in neuromuscular transmissionneuromuscular transmission Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 28. 2929 Synthesis & Release of AcetylcholineSynthesis & Release of Acetylcholine Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 29. 3030 StepsSteps of Generalof General mechanismmechanism of muscleof muscle contractioncontraction Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood AP= Action Potential MF= muscle fiber NMJ= Neuromuscular Junction Ach= acetylcholine SR= sarcoplasmic reticulum
- 30. Events occurring at NMJEvents occurring at NMJ 3131Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 31. 3232 StepsSteps of Generalof General mechanismmechanism ofof muscle contractionmuscle contraction Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 32. Summary of StepsSummary of Steps of Generalof General mechanismmechanism of muscle contractionof muscle contraction 3333Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 33. Summary of EventsSummary of Events of muscle contractionof muscle contraction 3434Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1 2 3 4 5 6 7 8
- 34. Take Home PointsTake Home Points Three Classes of MuscleThree Classes of Muscle are Skeletal, Cardiac, & Smooth.are Skeletal, Cardiac, & Smooth. Functional unit of Muscles is muscle fibre, composed of manyFunctional unit of Muscles is muscle fibre, composed of many myofibrilsmyofibrils.. Each myofibril is composed ofEach myofibril is composed of myofilamentsmyofilaments:: actinactin && myosinmyosin.. AA Sequence of eventSequence of events occurs ats occurs at neuromuscular junctioneuromuscular junction that finally resultsn that finally results in muscle contractionin muscle contraction AnAn Action potentialAction potential reachesreaches nerve fiber endingnerve fiber ending at neuromuscular junction,at neuromuscular junction, causingcausing release of acetylcholinerelease of acetylcholine Acetylcholine binds with its receptors atAcetylcholine binds with its receptors at motor-end platemotor-end plate, resulting in, resulting in opening ofopening of “acetylcholine-gated Sodium channels“acetylcholine-gated Sodium channels”” Diffusion of Na+ into muscle fiberDiffusion of Na+ into muscle fiber causes action potential in muscle fibercauses action potential in muscle fiber Action potential spreads in muscle fiber throughAction potential spreads in muscle fiber through T-Tubule system, thatT-Tubule system, that causescauses release of stored calcium ions fromrelease of stored calcium ions from sarcoplasmic reticulumsarcoplasmic reticulum Ca++ ions initiateCa++ ions initiate attractive forcesattractive forces between actin and myosin filamentsbetween actin and myosin filaments causing sliding of actin over myosincausing sliding of actin over myosin (Sliding Filament Mechanism)(Sliding Filament Mechanism) TheThe cross-bridge cyclecross-bridge cycle is repeated again & again till the completion ofis repeated again & again till the completion of contractioncontraction Sliding of actin filaments over myosin filaments through cross-bridge cycleSliding of actin filaments over myosin filaments through cross-bridge cycle is explained byis explained by Walk-Along Theory (or Ratchet Theory)Walk-Along Theory (or Ratchet Theory) 3535
- 35. Assessment Q. 4Assessment Q. 4 Name that current theory that explainsName that current theory that explains Sliding of actin filaments over myosinSliding of actin filaments over myosin filaments through cross-bridge cyclefilaments through cross-bridge cycle 3636Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 36. Learning ResourcesLearning Resources Guyton and Hall (Text book ofGuyton and Hall (Text book of physiology), 13th Editionphysiology), 13th Edition Ganong (Text book of physiology),Ganong (Text book of physiology), 24th Edition24th Edition Human Physiology : from cells toHuman Physiology : from cells to system Lauralee Sherwood,9system Lauralee Sherwood,9thth EditionEdition Human Physiology Stuart Ira Fox, 13thHuman Physiology Stuart Ira Fox, 13th EditionEdition InternetInternet Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood3737
- 37. Next topic Contractile Mechanism of Skeletal Muscle II 14/1/2017, 0930 am: 1030 am Prior knowledge required: Contractile Mechanism of Skeletal Muscle I 3838Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
- 38. ANY QUESTIONS? Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood3939
Editor's Notes
- I now want to talk about the three classes of muscle, and these three classes were generated based on histological appearance and function. Let’s start with a brief overview. Skeletal muscle is striated, in other words, it looks like it has lines running through an individual muscle cell. Skeletal muscle is also voluntary, in other words, you have conscious control over your skeletal muscles, well at least most of them. Skeletal muscle is also multi-nucleated, and when we speak of an individual skeletal cell, we call it a myofiber. Cardiac muscle is also striated, in other words, it looks like there are lines running through the cell. It is involuntary, you do not really have conscious control over how your heart muscle beats. Next, the cardiac muscle appears branched, and I’ll show you an example of that in a little while, and when we speak of cardiac cells we speak of cardiocytes. Smooth muscle is non-striated, and is involuntary, and is fusiform in shape, in other words it looks like a spindle.
- The word muscle means little mouse, and its because when you flex the muscle the ball of muscle underneath your skin was thought to look like a little mouse. Some properties of muscle include being excitable, that’s means they can generate an electrical response, there are conductive, that means the electrical excitation can spread, in other words travel. Next it has contractility, that means it can shorten, and it has extensibility, in other words you can stretch your muscle. Lastly the muscle has elastic properties, and that basically means it can recoil back into its original shape. The prefixes “myo” and “sarco” also means muscle.
- Walk-Along Theory (or Ratchet Theory)