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Membrane Potentials and Action Potentials - Coggle Diagram

- - - - this make potassium to move outside cell according to diffuision low (from high to low cons.)
        
        as the potassum is positive charge , it creates a electropositvity outside membrane , and electronegativity inside
        
        Within about 1 millisecond, the potential difference between the inside and outside, called the diffusion potential,
    - - it move from outside to inside
        
        as sodium is positive, creates a membrane potential of opposite polarity to that
- - - - we usuallt assumed that potential in extracellular fluid is ZERO , and the inside potential is nernst potential
        
        the sign of the potential is positive (+) if the ion diffusing from inside to outside is a negative ion, and it is negative (−) if the ion is positive.
        
        when the concentration of positive potassium ions on the inside is 10 times that on the outside, the log of 10 is 1, so the Nernst potential calculates to be −61 millivolts inside the membran
- - - - (1) the polarity
        of the electrical charge of each ion
      - (2) the permeability
        of the membrane (P) to each ion
      - (3) the concentration (C) of the respective ions on the inside (i) and outside (o) of the membrane
- - - - the permeability of the membrane to potassium is about 100 times as great as its permeability to sodium.
        
        Using this value in the Goldman equation, and considering only sodium and potassium, gives a potential inside the membrane of −86 millivolts
  - - - the net membrane potential when all these factors are operative at the same time is about −90 millivolts.
        
        additional ions, such as chloride, must also be considered in calculating the membrane potential
- - - - then , resting potential (-70 milivolt) will neutralized by inflowing of these positive ion
        
        in large nerve fibre , great amount of sodium will enter ,it cause action potential to beyond zero level
        
        in smaller one and cns nerons , the potential approch the zero level but does not overshoot to the positive state
  - - - and then a rapid diffusion of potassium ion to exterior to reestablishe the normale resting potential