文档介绍：Section IV Contraction function of muscular cell
冯鉴强教授
The mechanical movements in the living body depend on contraction function of muscular cell
Respiratory muscles contract →completing respiratory movement
Cardiac muscles contract → pushing blood to flow and maintaining blood pressure
Gastrointestinal smooth muscles contract → helping digestion of foods.
Skeletal muscle, cardiac muscle and smooth muscle have the similar mechanism of contraction
Structure of Skeletal Muscle
About 40 per cent of body is skeletal muscle, any other 10 percent smooth and cardiac muscle
Physiologic anatomy of skeletal muscle
The skeletal muscle fiber
All skeletal muscles posed of numerous fiber ( 10 to 80 micrometers in diameter)
Each fiber is made up of small subunits( myofibril 肌原纤维)
Each fiber is innervated by only one nerve ending (the basic structure and functional unit for movement)
Sarcolemma(肌膜):the cell membrane of the muscle fiber
The surface layer of a fuses with a tendon fiber → to form muscle tendon → insert into the bones
Myofibrils : composed of myosin filament( thick myofilament, about 1500) and action filament ( thin myofilament, about 3000)
Myosin filaments and actin filaments partially interdigitate (交替穿插) and cause the myofibrils to have light and dark bands(Fig 2-23).
The light bands (I bands, isotropic 各向同性) and the dark bands (A bands, anisotropic 各向异性) give skeletal and cardiac muscle their striated appearance
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.
ere : the portion of myofibril that lies between two essive Z discs including 2 * 1/2 light band and one dark band
ponents of myofilament
Thick posed of 200 or more myosin molecules(肌凝蛋白分子)
MW of 480,000
Myosin molecule consisting of six polypeptide chains: two heavy chains and four light chains
Heavy chains : wrap around each other to form a double helix: one en