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KIN 4430 - Muscle Function & Metabolism.docx

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Department
Kinesiology
Course
Kinesiology 4430F/G
Professor
Greg Marsh
Semester
Fall

Description
POWER POINT 1Sarcomere has zlines dark area with more myosin light area has more actin filaments All 3 types of muscles are contractile while only cardiac and skeletal has a straight appearance Cardiac muscle contracts together as one due to autonomous control Smooth muscle is less organizedSkeletal muscle has reflex control but primarily consciously controlledSkeletal MuscleA highly organized tissuecollection of similar cells with a unique set of properties 40 of body massConnective tissue surrounding entire muscle at all levelsLimb muscles have functional compartmentsdifferent functions for different parts different conditionsFunctional compartments are determined by innervationInnervated by alpha motor neuron possible to activate half of muscle if desired Nervous system can selectively innervate 1 part of muscle over otherMuscles composed of many fascicles which are surrounded by perimysium Fasciclessmaller view of muscle 1 level of any muscle composed of many muscle fibresA lot of mysium surrounding muscles on all levels to support the filamentsEach celllevel of muscle is separated by connective tissueSarcomeres are the fundamental contractile unit thread of sarcomeres make a myofibril Actin and myosin are the contractile proteinsImportant for movement providing heat energy to warm bodythermogenesis protect organs storage of proteinsmetabolismoMAJOR FUNCTION Transform electrochemical energy to mechanical energy to generate forcetension by contraction and ultimately to produce movement KEY PROPERTIES 1Excitability irritabledeveloping and propagating a transient electrical eventaction potential2Contractibilityability to shorten3Extensibilitystretched without damagecontrolled4Elasticityreturns to original state after b and cTorque Generating Capabilitycross bridge functionmuscle massfibre type compositionpassive stiffnesselasticitymuscle joint geometrybiomechanicsactivation historyhow its been used in pastneural activationantagonistactivation and passive stiffnessgeneral characteristics are genetic muscle properties can be changed via exercise trainingStructurefunctioncontractionwhole muscle coordinated function vs functional compartments functional changes can modify structure of muscle and vice versacontractile componentsmuscles shortencontract do not pushconnective tissue transfers tension to bones to cause movement structural proteins at the subcellular level titin desmin nebulin myomesin alpha actininothere are lots of subcellular proteins that are not contractile but supporting cast that assist in contraction transmit force to tendons resist injures stretch by distributing forces mechanodtransducers promote gene transcription involved in protein metabolism HILL MODELContractile Elementproduces force Includes viscosity which is resistance to stretchFaster the speed of stretchincreases resistancegood thing which prevents damage to muscleCE shortens which pulls on PE and SE results in contraction at the tendon but is modified by nonelastic structural proteins before reaching tendon If elastic elements buffer enough the contraction in the CE would result in no forceSeries Elastic Elementsspring like tissues tugged by contracting of CEParallel Elastic Elementstugged by contracting of CEElastic elements modify the force their properties determine how much force gets to the tendonPassive Elastic elements ConnectiveTissue tendons and titinActive elastic elementsrotation of myosin heads during actin attachment some elasticity at subcellular levelmyosin POWER POINT 2Graphstrong correlation between volume and torque men generate more forceDeterminants of Muscle Force OutputMore size more force muscle force is proportional to crosssectional areaCSA more correctly physiologic crosssectional areaPCSAShapecompartments length of fibres and pinnationAngle arrangementMuscle ShapesUninon pennatebiggest ROM bipennate multipennatemost force produced via multi angleFLfibre length MLmuscle length Muscle fibres rarely go from origin to insertion common in very short muscles therefore these fibres need to attach to one another Ratio of FLML is usually less than 10208Series muscles contract faster parallel muscles generate more force however no muscles are organized to these extremes but rather a variation of both
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