Please enable JavaScript.

Coggle requires JavaScript to display documents.

Mae Stansbury, Period 5, Muscular System - Coggle Diagram

- - - - Striations: stripes formed from repeating series of dark and light bands along length of each myofibril
        
        A bands are the dark regions
        
        H zones is lighter region in middle of dark A band
        
        M zone is line of protein (myomesin) that bisects H zone vertically
        
        I bands are lighter regions
        
        z disc (line) is coin shaped sheet of proteins of midline of light I band
      - Sarcomere: smallest contractile unit of a muscle fiber, has A band with half an I band at each end; individual sarcomeres align end to end along myofibril
      - Myofilaments: orderly arranged of acting and myosin myofilaments within a sarcomere; acting myofilaments are thin filaments; myosin myofilaments are thick filaments; sarcomeres cross section shows hexagonal arrangement of 1 thick filament surrounded by 6 thin filaments
      - Molecular composition of myofilaments
        
        Thick filaments are made of protein myosin that has 2 heavy and 4 light polypeptide chains
        
        Thin filaments are made up of fibrous protein actin
        
        Elastic filament: made of protein titin
        
        Dystrophin: links thin filaments to proteins of sarcolemma
        
        Nebulin, myomesin, C proteins bind filaments or sarcomeres together
- - - - ACh is released from the Motor neuron and binds to ACh receptors on the sarcolemma
      - Causes chemically gated ion channels (aka ligands) on sarcolemma to open
      - Na+ diffuses into muscle fiber
      - Since Na+ diffuses in, interior of sarcolemma becomes less negative and more positive
      - Results in local depolarization called end plate potential
    - - generation and propagation of actin potential
      - If end plate potential causes enough change in membrane voltage to reach critical level known as threshold voltage gated Na+ channels in membrane will open
      - large influx of Na+ through channels into cell triggers AP that is unstoppable and will lead to muscle fiber contraction
      - AP spreads across sarcolemma from one voltage gated Na+ channel to next one in adjacent areas, making areas depolarize
    - - restores vesting conditions
      - Na+ voltage gated channels close, and voltage gated K+ channels open
      - K+ efflux out of cell rapidly brings cell back to initial resting membrane voltage
      - Refractionary period: muscle fiber cannot be stimulated for a specific amount of time until repolarization is complete