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MUSCLE, Consists of cells specialized for contractions (muscle cells),…

- - - - Antagonist: act against the action of paired agonist (prevent over-contraction of agonist)
      - Synergist: Aid the prime movers by adding some force towards the direction of movement and stabilize the joints
      - Agonist: produce movement as prime mover
      - Fixator: Stabilize the joints when movement produced
    - - Group of muscle fibers that get the signal(action potential) from same, single motor neuron
        
        Force produced is massive when a large amount
        of muscle fibers are stimulated to contracts
        
        The force produced by a muscle depends on the frequency and strength of stimulation (graded muscle response)
        
        The higher the frequency of action potential transmission at NMJ, the stronger the force produced by successive contractions.
        
        The calcium ions are not recycled into SE but remain in sarcoplasm and new calcium ions released due to action potential, more active sites on actin will expose
        
        More myosin heads can bind to the active sites, providing stronger and stronger twitches with time if action potential keep transmits in high frequency.
        
        When the twitches of muscle fibers fused, it will cause the muscle to reach maximum tension.
        
        Cannot remain for a long time due to limited ATP molecules
        
        Contraction will also gradually become stronger if motor neuron stimulate more and more motor unit.
        
        The motor neuron will stimulate the smallest motor unit first, and gradually to the biggest motor unit if the stronger contraction is required by us. Contraction of previous motor units combined.
        
        To make sure the force produced will gradually increase but not surged drastically.
      - Big motor unit (more muscle fibers)
      - Small motor unit (fewer muscle fibers)
    - - isotonic contraction
        
        The muscles involved in contractions change in
        their length
        
        Occur when the force produced is able to move the load
      - isometric contraction
        
        The muscle involved in contractions do not undergo changes in their length
        
        Occur when the force produced is unable to move the load.
- - - - high-energy-conformation myosin head binds to the active sites, forming cross-bridge
        
        Power stroke occurs when energy stored in myosin head released.(ADP and inorganic P group released from myosin head). Thin filament being pulled towards M line
        
        Myosin head detaches from active site of actin when a new ATP molecule binds to the myosin head
        
        Reactivation of myosin head occur when the ATP being broken down into ADP dan P group. Myosin head now can bind to active sites of actin again.
- - - - Myofibril made out of many repeating contraction units called sacromere
        
        Each sarcomere made up of thin filament (actin) and thick filament (myosin)
- - - - The action potential spread along sarcolemma, travel down T tubules to sarcoplasmic reticulum. Calcium ions are released into sarcoplasm
        
        Calcium ions bind to troponin, causing the tropomyosin to dislocate from active sites of actin. Thus myosin heads will bind to the active sites and initiate the contraction cycle
        
        The muscle contracts and movement produced