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Intro to muscle (Muscle Contraction Mechanism (sliding filament theory…

- - - - slow-twitch fibres
      - fast-twitch oxidative glycolytic fibres (intermediate fibre)
      - fast-twitch glycolytic fibres
- - - - structure of muscle fibre:
        
        several nuclei
        
        sarcoplasm: cytoplasm
        
        sarcolemma (-sheath): cell membrane
        
        extension of sarcolemma is t/transverse (-extending)-tublues and allows for rapid action potential diffusion
        
        sarcoplasmic reticulum: endoplasmic reticulum (involved in protein/lipid synthesis)
        
        enlarged areas of the sarcoplasmic reticulum is the terminal cisternae which store Ca2+
      - structure of myofibril
        made up of striations called sarcomere
        
        contractile proteins: they interact through cross bridges whereby both myosin heads must interact with the actin
        
        actin
        
        myosin
        
        myosin:
        2 proteins chains coiled with a stiff head and tail region and a flexible hinge in between
        
        actin:
        G/globular actin form F/filamentous actin
        2 f-actin form thin filament and associates with regulatory proteins
        
        regulatory proteins:
        
        troponin
        
        tropomyosin
        
        accessory proteins:
        
        titin
        
        nebulin
        
        titin:
        
        stretches from Z to M
        
        stabilises contractile proteins
        
        returns to normal length
        
        nebulin:
        
        attaches to z
        
        aligns actin
        
        sarcomere:
        z-line (Zig Zag): attachment site for thin filament
        i band (In between myosin filaments): only thin filament
        a band (All of myosin filament): thicc and thin filament overlap
        h zone (Holds full unit): only thicc filament
        m line (Middle): attachment site for thicc filament