13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle...

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Muscle Physiology Physiology Unit 2

Transcript of 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle...

Page 1: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

MusclePhysiology

PhysiologyUnit2

Page 2: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

InPhysiologyToday

Page 3: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

SkeletalMuscle

• Characteristics– Striated–Multinucleated–Voluntary

• Organization–Myofiber• Myofibril–Myofilament

Page 4: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

Sarcomere

• Functionalunitofskeletalmuscle

• Composedof3filaments– Thickfilament

• Myosin

– Thinfilament• Actin• Troponin• Tropomyosin

– Elasticfilament• Titin

Page 5: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

ThickandThinFilaments

Page 6: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

SlidingFilamentTheoryofContraction

• Crossbridgesformbetweenthethickandthinfilaments

• Thinfilamentsslideacrossthethickfilaments– Thinfilamentswillmove

closertogether– DistancebetweenZlines

decreases– IbandandHbandsshorten

duringcontraction– Abandstaysthesame

Page 7: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

MusclePhysiology

• 2distincteventshappenwhichleadtomusclecontraction

1.Electricalevents– ActionPotential– Receptoractivation– EPP– AP– Electricaleventstriggerthemechanicalevents

2.Mechanicalevents– Developingtensioninthemuscle– IncreaseCa2+ levels– contractileproteinsmoving– musclefibershortens

Page 8: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

StimulustoContraction• Stimulus

– Receptoractivation– Skeletalmuscle:AChbindingtoN-Achr– ResultsinanEPP

• Latentperiod– Excitation-Contractioncoupling

• Contractionperiod– Cross-BridgeCycling– Generatestensioninthemuscle

• Relaxationperiod– Stimulusendsorcellfatigues– Musclereturnstoitsrestingstate

Page 9: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

MuscleTwitch

Page 10: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

Stimulus

• Somaticmotorneuronsinnervateskeletalmuscle• Largestdiameterneurons• Myelinated• HighvelocityAP

• Uponreachingmuscle,axondividesintomanybranches

• Eachbranchformingasinglejunctionwithamusclefiber=motorunit

Page 11: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

EPPtoAP

Page 12: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

ActionPotentialtoContraction• APlasts1-2ms• Completedbeforeany

mechanicalactivitybegins• Mechanicalactivity

(contraction)maylast>100ms

• Electricalactivity(actionpotential)doesnotactoncontractileproteins

• Producesastateofincreasedcytolsolic[Ca2+]– Resting[Ca2+]=0.1mMol/L– AfterAP[Ca2+]=1mMol/L

Page 13: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

LatentPeriod

• Excitation-ContractionCoupling• SequenceofeventsfromthegenerationofanAPacrossthesarcolemmatoCa2+ releaseinsideofthemyofiber

• Sarcolemmaisanexcitablemembrane– GeneratinganAP(fromEPP)– PropagatinganAP– Similarmechanismsasneurons

Page 14: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

ContractionPeriod

• IncreaseinintracellularCa2+ levelstriggerthemechanicalevents

• Ca2+ activatesCross-BridgeCycling

Page 15: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

SarcoplasmicReticulum• LateralsacsstoreCa2+

• T-tubulehasDHPreceptors– DHPreceptorsarenormally

voltagegatedCa2+channels– Inskeletalmusclet-tubules,

actsasavoltagesensor

• SRhasryanodinereceptors– IntracellularCa2+channels

– WhenCa2+channelsopen,Ca2+ movesintocytoplasm

Page 16: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP
Page 17: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

CalciumRelease

• DHPreceptorstriggercalciumrelease

• Ryanodinecalciumchannelsopen

• InfluxofcalciumfromSRintocytoplasm

• Calciuminfluxtriggerscrossbridgecycling

Page 18: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

ActivationbyCa2+• Tropomyosincoversthe

myosinbindingsitesonactin• Troponinholdstropomyosin

inplace- has3sub-units1. TroponinI

• inhibitory2. TroponinT

• Tropomyosinbinding3. TroponinC

• Calciumbinding

• IncreaseinintracellularCa2+levelscauseTroponinCtobindtoCa2+ whichexposesbindingsitesonactin

Page 19: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

Troponin

Page 20: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

CrossBridgeCycling

1. Attachmentofthemyosincross-bridgetoactinofathinfilament

2. Movementofthecross-bridge,pullingonthethinfilament– Eachcross-bridgemovesindependentlyofallothercross-

bridges– Asynchronouspullingaction

3. Detachmentofcross-bridgefromthethinfilament4. Energizingthecross-bridgesoitcanagainattachto

athinfilamentandrepeatthecycle

Page 21: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

Cross-BridgeCycling

Page 22: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

ATPinMuscleMetabolismUsesofATPinMuscle

Contraction

• Activationofmyosin– High-energymyosin

• Releaseofmyosinheadfromactinmolecule

• ActivetransportofCa2+intoSRfromthesarcoplasm

MuscleContractionRequiresALotofATP!

• NoATP“storage”• 3pathwaysforregeneration– Phosphagensystem– Glycolysis– Aerobicrespiration

EnergyATP+H20 à ADP+pi +H+ +

Page 23: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

SourcesofATP

1.Phosphagen System2.Glycolysis3.Oxidativephosphorylation

Page 24: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

PhosphagenSystem• Creatine

– Naturalproducednythebody– Madefromaminoacids

• CreatinePhosphate– Astoreofhighenergy

phosphate

• CreatineKinase– Transfersphosphategroup

fromCPtoADP– Presentat3xhigher

concentrationinskeletalmuscle CrP+ADP+H+---->Cr+ATP

Page 25: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

PhosphagenSystem

• AdenylateKinase– AwaytoquicklymakeATP– ADP+ADP---- >ATP+AMP

Page 26: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

AerobicRespiration

• PrimarysourceofATPproductionformuscleduringrestorlightexercise

• Fuelutilizationbyskeletalmuscle– fattyacids– muscleglycogen– bloodborneglucose

Page 27: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

AnaerobicMechanisms• Oxygenconsumption– ExercisingmusclecanconsumemoreATPthancanbeproducedbyaerobicrespiration

– Musclecellswillutilizeavailableglucoseandglycogenreserves

– Glycolysis willthenproduceATPtokeepupwiththedemandoftheactivemuscle• Lacticacidaccumulates

– OxygenDebt• Theamountofoxygenconsumedtogetthemusclecellsandplasmabacktonormalconditions– Glucoselevels– Glycogenreserves– Convertinglacticacidbacktopyruvic acid

Page 28: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

SmoothMuscle• singlecells,nostriations• circularlayer

arrangement• nosarcomeresor

troponin• actin:myosinratio=13:1• utilizesCa2+/calmodulin

mechanism• gradeddepolarizations• singleunitvsmulti-unit• autonomicinnervation

Page 29: 13 Phys Muscle Physiology...Muscle Physiology •2 distinct events happen which lead to muscle contraction 1.Electrical events –Action Potential –Receptor activation –EPP –AP

SmoothMuscle


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