Depolarization

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- Discussion: Stimulus for Contraction:
    - stimulus for muscle contraction is an electrical impulse from motor
          nerve at the motor end-plate or neuromuscular junction;
    - when sarcolemma is stimulated by an incoming impulse, sodium, potassium,
          and chloride ions move about w/in transverse tubules to spread impulse and
        depolarize membranes;
        - this depolarization in turn causes a release calcium ions into sarcoplasm;
        - this in turn, causes all filaments in a muscle fiber contract together;