肌細(xì)胞的收縮功能

骨骼肌心肌平滑肌當(dāng)前1頁，總共30頁。第一節(jié)肌細(xì)胞收縮的結(jié)構(gòu)和分子基礎(chǔ)一、肌細(xì)胞的結(jié)構(gòu)1.橫紋肌當(dāng)前2頁，總共30頁。當(dāng)前3頁，總共30頁。myofibrilandsarcomere[‘sɑ:k?mi?]Isotropic(等方性的）band(Iband)orlightbandanisotropicband(Aband)ordarkbandmyosinmyofilament（粗肌絲）actinmyofilament（細(xì)肌絲）sarcotubularsystemtransverstubules(Ttubules)Sarcoplasmicreticulum,SR(aspecialtypeofsmoothERfoundinsmoothandstriatedmuscle)JuctionalSRorterminalcisternaTriad(theT-tubuleanditstwoterminalcisternaeformatriad)Thestructureofstriatedmuscle當(dāng)前4頁，總共30頁。當(dāng)前5頁，總共30頁。2.平滑肌細(xì)肌絲明顯多于粗肌絲，還有中間絲，沒有Z盤，沒有凹入的橫管，肌絲主要被肌膜而不是肌質(zhì)網(wǎng)包繞。當(dāng)前6頁，總共30頁。single-unitsmoothmuscle一單位平滑肌(也稱內(nèi)臟平滑肌)，多間隙連接

multi-unitsmoothmuscle多單位平滑肌，很間縫隙連接當(dāng)前7頁，總共30頁。二、參與收縮的蛋白分子三、肌絲滑行學(xué)說四、橫橋活動(dòng)與化學(xué)能轉(zhuǎn)化為能的過程當(dāng)前8頁，總共30頁。當(dāng)前9頁，總共30頁。當(dāng)前10頁，總共30頁。每秒循環(huán)5次當(dāng)前11頁，總共30頁。第二節(jié)興奮－收縮耦聯(lián)Excitation-contraction(EC)couplingT-tubulesconductsignalAPsintothecellDepolarizationofT-tubulecausescalciumreleasefromSRCalciumactivationofcontractionRelaxationoccursasaresultoftheactivetransportofCa2+intotheSRbytheCa2+pumpontheSRmembrane當(dāng)前12頁，總共30頁。當(dāng)前13頁，總共30頁。當(dāng)前14頁，總共30頁。當(dāng)前15頁，總共30頁。內(nèi)質(zhì)網(wǎng)上的鈣釋放通道主要有：Ryanodine（雷諾?。┦荏wInositoltriphosphate（三磷酸肌醇）受體當(dāng)前16頁，總共30頁。骨骼肌：?jiǎn)问湛s時(shí)，胞質(zhì)內(nèi)增加的Ca2+100%來自SRL-型鈣通道構(gòu)象變化觸發(fā)鈣釋放心?。喊|(zhì)內(nèi)增加的Ca2+：SR釋放的占80%~90%，L-型鈣通道內(nèi)流的占10%~20%

高度依賴于細(xì)胞外的Ca2+，鈣致（觸發(fā)）鈣釋放。當(dāng)前17頁，總共30頁。心肌興奮－收縮耦聯(lián)當(dāng)前18頁，總共30頁。當(dāng)前19頁，總共30頁。第三節(jié)肌細(xì)胞收縮的生物力學(xué)當(dāng)前20頁，總共30頁。當(dāng)前21頁，總共30頁。isometriccontraction等長收縮TensioninthemusclesincreasesThemuscleisunabletoshortenisotoniccontraction等張收縮MyofilamentsareabletoslidepasteachotherduringcontractionsThemuscleshortens當(dāng)前22頁，總共30頁。PreloadPreloadInitiallengthSingletwitchtensionisdeterminedbylengthofsarcomere當(dāng)前23頁，總共30頁。Afterload當(dāng)前24頁，總共30頁。當(dāng)前25頁，總共30頁。EnergyforMuscleContractionSlide6.26bCopyright?2003PearsonEducation,Inc.publishingasBenjaminCummingsAnaerobicglycolysis(continued)Thisreactionisnotasefficient,butisfastHugeamountsofglucoseareneededLacticacidproducesmusclefatigueFigure6.10b當(dāng)前26頁，總共30頁。EnergyforMuscleContractionSlide6.25Copyright?2003PearsonEducation,Inc.publishingasBenjaminCummingsAerobicRespirationSeriesofmetabolicpathwaysthatoccurinthemitochondriaGlucoseisbrokendowntocarbondioxideandwater,releasingenergyThisisaslowerreactionthatrequirescontinuousoxygenFigure6.10c當(dāng)前27頁，總共30頁。MuscleFatigueandOxygenDebtSlide6.27Copyright?2003PearsonEducation,Inc.publishingasBenjaminCummingsWhenamuscleisfatigued,itisunabletocontractThecommonreasonformusclefatigueisoxygendebtOxygenmustbe“repaid”totissuetoremoveoxygendebtOxygenisrequiredtogetridofaccumulatedlacticacidIncreasingacidity(fromlacticacid)andlackofATPcausesthemuscletocontractless當(dāng)前28頁，總共30頁。骨骼肌可以根據(jù)收縮速度被分為快肌和慢肌骨骼肌可以根據(jù)其收縮速度被分為兩種基本類型：快肌(fasttwitch)和慢肌(slowtwitch)。雖然有些肌肉幾乎只含有快肌纖維或慢肌纖維，大多數(shù)肌肉是由這兩種肌纖維混合而成的。但是另一方面，一個(gè)運(yùn)動(dòng)單位典型地只含有一種類型的肌纖維。因此，骨骼肌往往同時(shí)含有快肌運(yùn)動(dòng)單位和慢肌運(yùn)動(dòng)單位。當(dāng)前29頁，總共30頁。在人體，快肌纖維直徑較大，具有高的酵解能力和低的氧化能力。與此相反，慢肌纖維典型地具有較小的直徑，具有較高的氧化能力和較低的酵解能力。這個(gè)代謝活動(dòng)的基本差異是與慢肌纖維的抗疲勞特性相吻合的。與此相比，快肌纖維則易于疲勞。由于肌纖維疲勞特性的這種差異，在肌肉收縮的過程中，首先被募