Chapter8 Contraction of Muscle 1.Physiologic anatomy ofskeletal muscle (1)The skeletal muscle fiber All skeletal muscles are composed of numerous fiber 10 to 80 micrometers in diameter)Each fiber is made up of small subunits(myofibril).Each fiber is innervated by only one nerve ending (the basic structure and functional unit for movement) (2)Myofibril:composed of myosin filament(thick myofilament,about 1500)and action filament thin myofilament,about 3000);Myosin filaments and actin filaments partially interdigitate and cause the myofibrils to have light and dark bands;H bands and M disc(at the middle of H bands)Z disc at the middle of light bands);from z disc,the actin filaments extend in both direction to interdigitate with myosin filaments (3)Sarcomere:the portion of myofibril that lies between two successive Z discs including 2 1/2 light band and one dark band.Sarcomere is the basic unit of contraction ofmuscle. (4)Cross-bridges:the protrudingarms and heads together functions of cross-bridges:A.myosin head functions as an ATPase enzyme which can cleave ATP B.combing with thin myofilament and using the energy to energize the contraction process (5)Thin filament:a complex,composed of three protein components actin, tropomyosin and troponinChapter8 Contraction of Muscle 1. Physiologic anatomy of skeletal muscle (1)The skeletal muscle fiber :All skeletal muscles are composed of numerous fiber ( 10 to 80 micrometers in diameter) .Each fiber is made up of small subunits( myofibril) .Each fiber is innervated by only one nerve ending (the basic structure and functional unit for movement) (2)Myofibril: composed of myosin filament( thick myofilament, about 1500) and action filament ( thin myofilament, about 3000); Myosin filaments and actin filaments partially interdigitate and cause the myofibrils to have light and dark bands; H bands and M disc( at the middle of H bands) Z disc ( at the middle of light bands); from z disc,the actin filaments extend in both direction to interdigitate with myosin filaments (3)Sarcomere: the portion of myofibril that lies between two successive Z discs including 2 * 1/2 light band and one dark band.Sarcomere is the basic unit of contraction of muscle. (4)Cross-bridges: the protruding arms and heads together functions of cross – bridges: A. myosin head functions as an ATPase enzyme which can cleave ATP B. combing with thin myofilament and using the energy to energize the contraction process (5) Thin filament: a complex, composed of three protein components actin ， tropomyosin and troponin