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Muscles - Coggle Diagram

- - - - made up of hundreds of MUSCLE FIBRES
      - fibres grouped together
        in bundles
      - bundles bound by vascular
        connective tissue
    - - surrounded by membrane
        = sarcolemma
        
        at intervals - folded inwards
        
        forms transverse (T) tubules
      - each fibre = multinucleate
        
        nuclei arranged just inside sarcolemma
      - fibres contain cell organelles
        
        rich in mitochondria
      - bulk of fibres filled with
        MYOFIBRILS
      - large structures
        
        many cm long
      - filled with sarcoplasm
        (like cytoplasm)
    - - consist 2 types protein
        
        ACTIN
        
        forms thin filaments
        (7nm diameter)
        
        slot between outer
        edges of myosin
        
        linked together by thin disc
        (Z line)
        section of myofibril between 2 Z lines
        = sarcomere
        
        MYOSIN
        
        forms thick filaments
        (15nm diameter)
        
        lie in central region of each
        contractile unit
        
        linked together by thin disc
        (M line)
        
        runs perpendicular to orientation of myosin filaments
      - contractile elements
      - structure
        
        I (isotrophic) band
        
        light band of filaments only
        (no overlap)
        
        Z line
        
        runs through middle of I band
        
        A (anisotropic) band
        
        dark band of filaments
        
        H zone
        
        thick filaments only
        (no overlap)
      - alternating pattern of myosin + action
        
        forms STRIATED pattern
- - - - Ca2+ initiate events
        of contraction
  - - - 1 motor neurone may control contraction in entire muscle
        
        BUT = not all fibres contract @ 1 time