PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 1510-1Anatomy of a skeletal muscleepimysium: dense, irregular CT outer wrappingfascicles: bundles of muscle fibers( commonly known as the grain or fibers)perimysium: fibrous CT surrounds each fascicleSuperficial fascia between hypodermis and muscleDeep fascia-between individual organs10-2Attachementdirect: epimysium fused to periosteumindirect: linked to bone by CT attachmentsIndirectDirect10-3tendon: ropelike dense CTaponeurosis: sheet like dense CTindirect connections are strong and small10-4Terminology associated with muscle fiberssarco- or myo-protein filaments = myofilamentscytoplasm = sarcoplasmcell membrane = sarcolemmaer = sarcoplasmic reticulum10-5Muscle fibers contains stacks of parallel myofibrilsprotein filaments in parallel myofibrils are in register A bands alternate with I bandsA-band0.5 I-band 0.5 I-bandH - zone10-6Z-zone bisected by M-lineZ ZM10-7single overlapping protein unit:sarcomereone unit between Z discsfunctional unit of muscle10-8Sarcomere structure: 3 protein filament typesThick filaments in A bandOverlap with thin filamentsElastic filaments: titin, suspend thick filaments10-9Z disc: connects each sarcomere togetherM line: thick filaments bound togetherNo thick: I bandNo thin: H zone10-10Myofilament structureThick filament: bundles of myosintail: 2 interwoven chainsheads: 2 connected globular regionsaround 300 myosins collected into thick filamentTwo “interwoven golf clubs”10-11Thin filament: helical polymersbackbone or scaffolding: double helix of actin moleculesactin core wrapped by tropomyosin filamentsevery 40 nanometers, troponin complex3 troponin protein subunits: I, T, C Note how tropomyosin covers dark circle10-12Sarcoplasmic reticulum (sr)extensive smooth sr wrapped around myofibrils, ends in terminal cisternae (cisterns)Shown in bluish-purple10-13. T-tubules (transverse tubules)tubular extensions of sarcolemma penetrate fiberTerminal cisternae, t-tubule triad at A-I junction10-14 Skeletal muscle fiber contractionband width changes with contractionif banding due to filament overlapcontraction must be due to change in overlap10-15Sliding Filament Hypothesiscontraction due to filaments sliding past each other;specifically, thick filaments stay stationary, thin filaments move toward center, pull z-disks closertogetherFilament sliding predicated on Electrical