contractile mechanism of skeletal muscle 1
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Muscle Physiology
Prof. Dr. Rashid Mahmood
Contractile Mechanism of Skeletal Muscle I
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
Video of muscle contraction
Objectives Objectives Goal/Aim (Main Objective): To explain the mechanism of muscle contractionAt the end of this lecture students will be able toAt the end of this lecture students will be able to
Classify musclesDescribe organization of skeletal muscleDescribe general mechanism of skeletal muscle contraction.Describe molecular mechanism of skeletal muscle contraction.Outline different steps of Cross-bridge CycleExplain walk along theory...
Lesson contentsClassesClasses of Muscle of MusclePhysiological Anatomy Physiological Anatomy of Skeletal Muscleof Skeletal Muscle
SarcomereSarcomereActin & Myosin FilamentsActin & Myosin FilamentsThe T Tubules and Sarcoplasmic ReticulumThe T Tubules and Sarcoplasmic Reticulum
Sequence of events in Sequence of events in neuromuscular neuromuscular transmissiontransmissionSynthesis & Release of Synthesis & Release of Acetylcholine Acetylcholine Steps of Steps of General mechanism of muscle General mechanism of muscle contraction contraction
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Three Classes of Three Classes of MuscleMuscleBased on histological appearance and functionBased on histological appearance and function
SkeletalSkeletalstriated, voluntarystriated, voluntary
CardiacCardiacstriated, involuntarystriated, involuntary
SmoothSmoothnonstriated, involuntarynonstriated, involuntary
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Muscle
Tendon
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Skeletal Muscle
Physiological Physiological Anatomy of Anatomy of
Muscle Muscle
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Subunits Subunits Muscle
Muscle Fiber
Myofibrils
Myosin Filaments
Actin Filaments
Muscle fasciculus
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Light and Dark bandsLight and Dark bands
Striated Muscle
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Assessment Q. 1Assessment Q. 1Name the THREE types of Muscle Name the THREE types of Muscle
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Sarcomere Sarcomere
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Actin + Myosin Actin + Myosin FilamentsFilaments
Cross- Bridges
Sarcomere
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SarcomeSarcomerere
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Proteins that help in Proteins that help in alignment of Myofibrilsalignment of Myofibrils
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Myosin Molecule Myosin Molecule
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Myosin filamentMyosin filamentArm
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Myosin Molecule & Myosin Molecule & filamentfilament
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Assessment Q. 2Assessment Q. 2Name any THREE parts of Myosin Name any THREE parts of Myosin FilamentFilament
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Actin filament Actin filament
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Actin HelixActin Helix+ +
tropomyositropomyosinn
+troponin+troponin= =
Actin Actin FilamentFilament
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Troponin complex Troponin complex
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Binding Binding of of
myosin myosin head head with with
active active site in site in
the the presencpresence of Ca+e of Ca+
++
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Mammalian Skeletal Muscle: Two Transverse
Tubules per Sarcomere
Z lineProf. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood
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The T Tubules and Sarcoplasmic The T Tubules and Sarcoplasmic ReticulumReticulum
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Relation between T Tubules Relation between T Tubules and Sarcoplasmic Reticulumand Sarcoplasmic Reticulum
Sarcoplasmic Reticulum=Sarcoplasmic Reticulum=Terminal Cisternae+Terminal Cisternae+
Long Longitudinal Tubules Long Longitudinal Tubules
Terminal CisternaeTerminal Cisternae Long Longitudinal TubulesLong Longitudinal Tubules
•T TubuleT Tubule
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Assessment Q. 3Assessment Q. 3Name the THREE parts of Actin Name the THREE parts of Actin Filament Filament
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StepsSteps of of General General
mechanismmechanism of of muscle muscle
contraction contraction
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Sequence of events in Sequence of events in neuromuscular neuromuscular transmissiontransmission
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Synthesis & Release of Synthesis & Release of Acetylcholine Acetylcholine
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StepsSteps of General of General mechanismmechanism of of muscle contractionmuscle contraction
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AP= Action PotentialMF= muscle fiber NMJ= Neuromuscular Junction Ach= acetylcholineSR= sarcoplasmic reticulum
Events occurring at NMJEvents occurring at NMJ
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StepsSteps of of General General
mechanismmechanism of of muscle muscle
contractioncontraction
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Summary of StepsSummary of Steps of General of General mechanismmechanism of muscle of muscle contractioncontraction
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Summary of Events Summary of Events of muscle of muscle contractioncontraction
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Take Home PointsTake Home PointsThree Classes of Muscle Three Classes of Muscle are Skeletal, Cardiac, & Smooth. are Skeletal, Cardiac, & Smooth. Functional unit of Muscles is muscle fibre, composed of many Functional unit of Muscles is muscle fibre, composed of many myofibrilsmyofibrils. Each . Each
myofibril is composed of myofibril is composed of myofilamentsmyofilaments: : actinactin & & myosinmyosin..A A Sequence of eventSequence of events occurs at s occurs at neuromuscular junctioneuromuscular junction that finally results in n that finally results in
muscle contractionmuscle contractionAn An Action potential Action potential reaches reaches nerve fiber endingnerve fiber ending at neuromuscular junction, at neuromuscular junction,
causing causing release of acetylcholinerelease of acetylcholineAcetylcholine binds with its receptors at Acetylcholine binds with its receptors at motor-end platemotor-end plate, resulting in opening of , resulting in opening of
“acetylcholine-gated Sodium channels“acetylcholine-gated Sodium channels””Diffusion of Na+ into muscle fiber Diffusion of Na+ into muscle fiber causes action potential in muscle fibercauses action potential in muscle fiberAction potential spreads in muscle fiber through Action potential spreads in muscle fiber through T-Tubule system, that T-Tubule system, that causes causes
release of stored calcium ions from release of stored calcium ions from sarcoplasmic reticulum sarcoplasmic reticulum Ca++ ions initiate Ca++ ions initiate attractive forces attractive forces between actin and myosin filaments causing between actin and myosin filaments causing
sliding of actin over myosin sliding of actin over myosin (Sliding Filament Mechanism)(Sliding Filament Mechanism)The The cross-bridge cycle cross-bridge cycle is repeated again & again till the completion of contraction is repeated again & again till the completion of contraction Sliding of actin filaments over myosin filaments through cross-bridge cycle is Sliding of actin filaments over myosin filaments through cross-bridge cycle is
explained by explained by Walk-Along Theory (or Ratchet Theory)Walk-Along Theory (or Ratchet Theory)
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Assessment Q. 4Assessment Q. 4Name that current theory that Name that current theory that explains Sliding of actin filaments explains Sliding of actin filaments over myosin filaments through over myosin filaments through cross-bridge cyclecross-bridge cycle
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Learning ResourcesLearning ResourcesGuyton and Hall (Text book of physiology), Guyton and Hall (Text book of physiology), 13th Edition13th EditionGanong (Text book of physiology), 24th Ganong (Text book of physiology), 24th EditionEditionHuman Physiology : from cells to system Human Physiology : from cells to system Lauralee Sherwood,9Lauralee Sherwood,9thth Edition Edition Human Physiology Stuart Ira Fox, 13th Human Physiology Stuart Ira Fox, 13th EditionEditionInternetInternet
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Next topicContractile Mechanism of Skeletal Muscle II14/1/2017, 0930 am: 1030 amPrior knowledge required: Contractile Mechanism of Skeletal Muscle I
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ANY QUESTIONS?Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood3939