2011muscular tissue

nullnullMuscular tissuenullMyocyte-----muscle fiberCytomembrane of myocyte-sarcolemma Cytoplasm---- sarcoplasmaSmooth ER ----sarcoplasmic reticulum(肌浆网）Chapter Ⅵ Muscular tissuenullType:Skeletal muscleCardiac muscleSmooth muscle- Unstriated muscleStriated muscleAccording to their structure:According to whether muscle constraction is Controlled by the will or not:Skeletal muscle-Voluntary muscleCardiac muscleSmooth muscleInvoluntary musclenullThe structure ideograph of musclular tissuenullThe structure ideograph of three types of muscular tissuenull一.Skeletal muscle（一）Light microscopyCell body: cylindricalNuclei: multinucleate cell under sarcolemma; ovoid or fairly elongated Myoplasm:myofibril, mit and glycogenCross striations: composed of alternating dark and light bandsnullSkeletal muscle fibers（longitudinal section）—Muscle stellate cell————Myofibril—Cross striationsnullSkeletal muscle fiber（transverse section） ————Muscle fiber ——————Myofibrils ——————NucleusnullMuscle satellite cell-stem cell： lies in the surface of skeletal muscle fiber, flat with processes. Repair of muscle fibersUltrastructure of the muscle stellate cellnullMuscle fiber and myofibril———Muscle fiber—MyofibrilnullMyofibrilPolarized light microscopeLight band │Dark band │Light / I-bandDark / A-bandZ-lineZ-lineH-bandsarcomereM-linenullLight band (I-band):Z-line in the middle of itDark band(A-band):H-band in the middle of A-band,and M-line in the middle of H-band Sarcomere: the smallest repetitive subunit of the contractile apparatus, extends from Z-line to Z-line. Part of myofibrils½ I-band+ A-band + ½ I-bandLight band and dark bandConstitute:null线Sarcomere (TEM)SarcomereA-bandH-bandM-lineI-bandZ-lineZ-linenull（二）Ultrastructure 1. MyofibrilComposed of thick and thin filaments, arranged parallel to the long axis of the myofibrils in a symmetrical patternThick filament: presents in the A-band , fixed in the M-line ( the centre of a sarcomere )Thin filament: presents in the I-band and extend for some distance into the A-band. One of end fixed in the Z-line, the other is free and interdigitates with thick filamentnullone myofibrilZ-lineZ-lineThick filamentThin filamentnullZ-lineZ-lineM-line——H-band— Light/ I-band (thin filament)Dark / A-bandThick filamentThick/thinCross bridgenull I-band：thin filamentsA-band: thick filaments-H (middle)+thick/thin(others)nullComposed of myosin(肌球蛋白) “Head”: globular, ATP enzyme(bind to ATP) toward the Z-line and formed “cross bridge” “Rod”: toward the M-lineThick filament:nullMyosin—Head（ATPenzyme）—RodnullThin filamentnullTroponin 肌钙蛋白Actin 肌动蛋白Tropomyosin 原肌球蛋白Composed of three types of proteinnull—site binding to myosinTwo-stranded helical formationActinMonomernullTropomyosinTwo polypeptide chainsCoiled one on the other in an alpha helical pattern（swallow）nullTroponinA complex of three sub-units （TnT、TnI、TnC）—TnT: attatches to tropomyosin—TnI:inhibits the actin-myosin interactionTnC— Binds calcium ionsnullTroponin 肌钙蛋白Actin 肌动蛋白Tropomyosin 原肌球蛋白Composed of three types of proteinnull2. Transverse tubule (T tubule)The fingerlike invaginations of the sarcolemma（肌膜） form a complexes anastomosing network of tubules that encircles the boundaries of the A-I bands of each sarcomere in every myofibril Function： conduct the depolarization of sarcolemma to the sarcoplasmic reticulun cisternae(storing calcium ions) and affect the release of calcium ionsnullTransverse tubule——MyofibrilSarcolemma——Transverse tubule——A-band/ dark bandI-band / light band—Myofilamentsnull3. Sarcoplasmic reticulumSarcoplasmic reticulum (SER)-calcium pump and channel Longitudinal tubule(纵小管）: the part of sarcoplasmic reticulum lies between T tubules Terminal cisternae（终池）：the part of sarcoplasmic reticulum adjacent to opposite sides of each T tubule and are expanded Triad(三联体）：T tubule + terminal cisternae (two） nullTriad——MyofibrilSarcolemma——T tubule——A-bandI -band—MyofilamentsTerminal cisternae— Terminal cisternae—Triadnull(三) Contracted mechanism- sliding filament hypothesis calcium pumpSarcoplasm Ca2+ + Troponin(TnC)Alternation of troponin conformationWith the moving of tropomyosin, myosin attaches to actin Activation of enzyme of ATP→ Energy liberationImpulse→Sarcolemma→T tubule→Terminal cisternae→Sarcoplasmic reticulumnull Turning of “head”+ “rod” of myosinActin is pulled for M-lineResultI-band is narrow A-band is unchanged H-band diasppearsSarcomere is shortenedMuscle fiber contracts—nullZ-line │Contract： ————Sarcomere———Z-line │Z-line │Z-line │H-bandMRelaxed：nullM线—— ———肌球蛋白头——肌动蛋白——肌原蛋白TC—原肌球蛋白松弛时——Z线M线——收缩—Z线null二、Cardiac muscle—Intercalated discnull（一）Light microscopy(no muscle stellate cellCell body: short column in shape, and has two or more branches at its ends, associated with each other in a close meshwork Sarcoplasm: abundant with myofibrils,mit.,cross band and intercalated disc (闰盘）Nucleus: one or two centrally-located nuclei,ovoid in shapenullCardiac muscle(longitudinal section) —————IDnullCardiac muscle(transverse section)null(二）Ultrastructure(1)The actin and myosin are not divided into discrete myofibrilar bundles, and abundant mit.(2)T tubules are larger and at the level of the Z-line rather than at the A-I junction(3)The sarcoplasmic reticulum is not well-develped ,only a diad(one T tubule contact with one lateral expansion terminal cisternae） (4)Intercalated discs:located at Z-line Transverse -desmosome and intermediate junction Longitudinal-gap junctionnull——Myofilament——T tubule——Mit.————SR————DiadZ-line——Ultra-cardiac muscleA-band——I-band——nullIntercalated disc(ideograph)I.J.————D—————Gap———————Z-line—————nullIntercalated disc(TEM)null三、Smooth muscle1. Light microscopyCell body:elongated,tapering,spindle-shapedSarcoplsam:unstriated,Nucleus: a single elongated nucleus centrally placed in the broadest portion of each cellnullSmooth muscle (longitudinal section)nullSmooth muscle (transverse section)nullSmooth muscle(ideograph of TEM) No myofibrils—Dense patch——Dense body—Myofilament —————Foveanull2. Ultrastructure(1) Dense patch-under the sarcolemma,attached by thin myofilament（actin） Dense body-sarcoplasm,attached by thin myofilament and intermediate filament, and similar to Z-line(2) Intermediate filament-desmin,contact to dense patch and dense body-constitutes the cytoskeletonnull(3) Thick myofilament: myosin(cross bridge without M-line) Thick:thin=1:12-----Unit of myofilament Thin myofilament: One end attached to dense patch/dense body , Another is free(4) Gap between smooth muscle cellsnullSmooth muscle cell (Ideograph)Thin————Thick——Thin——ThicknullEmphasis in Chapter ⅥEmphasis in Chapter ⅥCompare the microstructural features of the three types of muscle tissue Describe the ultrastructural features and contraction mechanism of skeletal musclenullnullSkeletal muscle(Longitudinal sectionnullCardiac muscle(longitudinal section)nullSmooth muscle(longitudinal section)nullSkeletal muscle(transverse section)nullSmooth muscle(transverse section)nullCardiac muscle(transverse section)nullSarcoplasmic reticulum——MyofibrilSarcolemma——T tubule——A-bandI -band——FilamentTerminal cisternae— Terminal cisternae—TriadnullThick myofilament of smooth muscle—cross bridge