第二十章一骨骼肌神經(jīng)-接頭傳遞

六、肌細(xì)ContractionofMuscle(肌束(肌纖維/肌細(xì)胞(肌原纖維(肌節(jié)/肌小節(jié)(肌絲

Productionofbody運(yùn)動(dòng)單位(motor（一）骨骼肌神經(jīng)-肌接頭的傳神經(jīng)-肌接頭（NMJ）微細(xì)接頭前接頭后膜或終板接頭間神經(jīng)肌接頭（NMJ）興奮傳*ActivationofACh-gatedionchannel(nAChR)resultsinEnd-PlatePotential(EPP)神經(jīng)肌接頭傳遞（電-化學(xué)-電過(guò)程神經(jīng)沖神經(jīng)沖動(dòng)到達(dá)末梢，接頭前膜去電壓門控Ca2＋通道開(kāi)放、Ca2＋內(nèi)囊泡向接頭前膜囊泡向接頭前膜移動(dòng)、融合、破ACh釋放至接頭乙NaNa＋內(nèi)流使終板膜去極化NMJ興奮傳遞的特征是電-化學(xué)-電的N末梢AP→ACh＋受體→EPP→肌膜具1對(duì)1的關(guān)奮和收縮一次（因每次ACh釋放的量，產(chǎn)生的影響NMJ興奮傳遞的因素： 阻斷ACh受體：箭毒(curare)α（Flexadil，三碘季胺酚） 新斯的明，Sarin,VX,etc。3自身免疫性疾?。篗yasthenia（抗體破壞ACh受體),Lambert-Eatonsyndrome（抗體破壞N末梢Ca2+4接頭前膜ACh釋放↓：肉毒桿菌毒（二）橫紋肌細(xì)胞的興奮-收縮耦興奮-收縮耦聯(lián)的結(jié)構(gòu)基道）Longitudinaltubularsystem：LTriad：T管+興奮-收縮耦聯(lián)的關(guān)鍵離子——L型鈣通道和鈣釋放通骨骼肌細(xì)胞和心肌細(xì)胞的鈣釋骨骼肌細(xì)胞和心肌細(xì)胞的鈣回鈣瞬變（calciumtransient）引起肌肉的收縮和舒興奮-①肌膜電興奮的傳導(dǎo)②肌膜和T管上L型Ca2+通道激活③肌漿網(wǎng)上Ryanodine受體激活，肌漿網(wǎng)Ca2+釋放(calcium④觸發(fā)肌絲滑行，肌細(xì)胞收縮（三）肌絲的分子組粗肌絲（thick肌球蛋白橫橋（cross-

細(xì)肌絲（thin肌動(dòng)蛋白原肌球蛋白肌鈣蛋白（troponin橫紋肌收縮的原理—Z

MlineHband

ZA直

白的相互ICT ICTs原肌球蛋白細(xì)肌絲上的結(jié)合肌肌節(jié)縮短,肌細(xì)胞收Sourcesof肌肉的舒張(Muscle—mechanismsthatrestoresarcoplamicBacktocalciumCa2+pumpinsarcoplasmicreticulum~100%inskeletal~70%incardiacOutofthe①Na+-Ca2+exchangerincell②Ca2+pumpincellDiseasesassociatedwithabnormalregulationtheintracellularCa2+inskeletal Malignanthyperthermia:geneticdefectinryanodinereceptor,1in15,000children,1in50,000adults;Halothane/etherorsuccinylcholinestimulateCa2+releasefromSR,resultingmusclerigidityandhyperthermiaCentralcoredisease:geneticdefectinryanodinereceptor;SRreleases/leakCa2+,whichisthenaccumulatedbymitochondria,resultinginmitochondrialCa2+overloadandhencelossofmitochondriaandmuscleweaknessBrody’sdisease:geneticdefectinSRCa2+pump(SERCA):painlessmusclecram duringexerciseduetoslowedCa2+Summary:SequentialeventsofThesarcolemmaisdepolarizedandtheactionpotential(AP)propagates;TheactionpotentialspreadsinsidealongtheT-tubules;APistransmittedfromT-tubuletoterminalsacsofsarcoplasmicreticulum;Calciumisreleasedfromsarcoplasmicreticulumintosarcoplasm;Calciumbindstotroponinleadingtocooperativeconformationalchangesintroponin-tropomyosinsystem;Theinhibitionofactinandmyosininteractionisreleased;Crossbridgesofmyosinfilamentsareattachedtoactinfilaments;Tensionisexertedand/orthemuscleshortensbytheslidingfilamentCalciumispumpedbackintosarcoplasmicreticulum;Crossbridgesaredetachedfromthethinfilaments;Troponin-tropomyosinregulatedinhibitionofactinandmyosininteractionisActivetensiondisappearsandtherestlengthis（四）影響橫紋肌收縮效能的肌肉收縮的形單收縮、復(fù)合收縮、強(qiáng)直等張收IsotonicForce等長(zhǎng)ForceIsometric單收縮、復(fù)合收縮與強(qiáng)直收 前負(fù)荷 后負(fù)荷(After-determineslengthofcross-bridge cyclesandhencetotalnumberofcross-bridgesinteractingwiththinfilaments;肌肉的收縮性 affectingthoseproperties前負(fù)荷（Preload)：肌肉收縮前所承受的負(fù)荷,決定了肌節(jié)最適初長(zhǎng)（2.0-2.2m）時(shí)，粗細(xì)肌絲 佳，肌 小于最適初長(zhǎng)時(shí)，細(xì)肌絲可縮短距離↓→效能↓大部分骨骼肌的靜態(tài)長(zhǎng)度即是其最適初長(zhǎng)，Optimalinitiallength也稱Resting肌 Optimalinitiallength(resting后負(fù)荷↓→肌縮速度、幅度↑和張力↓后負(fù)荷過(guò)大，雖肌縮張力↑，但肌縮速度↓，不利作功后負(fù)荷過(guò)小，雖肌縮速度、幅度↑，但肌↓，也不利作TypesofskeletalTypeImuscleTypeIImuscleOtherATPaserateofsarcoplasmicGlycolyticOxidativeFine,skilled（五）平滑肌的收縮和舒MorphologicalMorphologicalandfunctionalMechanismsof形態(tài)學(xué)特involuntarymuscle;innervatedbyANS;foundprimarilyinthewallsofhollowSpindle-shapedcellstypicallyarrangedinNot-tubules&littlesarcoplasmic eres(soarenotstriated)butaremadeupofthick&myofilaments.ThinfilamentsinsmoothmuscledonotcontainCalciumbindstocalmodulin.Thecalcium-calmodulincomplex'activates'myosinwhichthenbindstoactin&contraction(swivellingofcross-bridges)Twotypesofsmooth多個(gè)單位平滑visceral,orunitary,smoothfoundinthewallsofholloworgans(e.g.,smallbloodvessels,digestivetract,urinarysystem,&reproductivesystem)multiplefiberscontractasaunit(becauseimpulsestraveleasilyacrossgapjunctionsfromcelltocell)&,insomecases,areself-excitable(generatespontaneousactionpotentials&contractions)multiunitsmoothconsistsofmotorunitsthatareactivatedbynervousfoundinthewallsoflargebloodvessels,intheeye(adustingtheshapeofthelenstopermit modation&thesizeofthepupiltoadjusttheamountoflightenteringtheeye),&atthebaseofhairfollicle(the'goosebump'muscles)Openingofvoltage-gatedcalciumchannelsaccountsfortheactionpotentialofmostsmoothmusclecells.平滑肌收縮與舒IonLittleappreciatedfactofHumanbeings(andotherlivingorganisms)arerunbyelectricity,and"ionchannels"arethecoreofourelectricalIonchannelsareeverywhere&arepresentinalmosteveryTransportofionsandRegulationofelectricalpotentialacrosstheIonYetanothertypeofmembranePoresinthemembranethatopenandcloseinaregulatedmannerandallowpassageofions“Dispose”ofthe Passivetransporters:IonsflowfromhightolowNoenergyisused;IfthereisnogradientionswillnotflowChannelIonchannelsarenotopencontinuouslybutopenandcloseinastochasticorrandomfashion.Ionchannelfunctionmaybedecreasedbydecreasingtheopentime(o),increasingtheclosedtime(c),decreasingthesinglechannelcurrentamplitude(i)ordecreasingthenumberofchannels(n).Whatgatesionchannel