The Membrane Action Potential depends upon a number of
factors:
Ion composition : Both the organic and inorganic charged
particles and their distribution across the Membrane dictates the
membrane action potential.
Permeability of the membrane : The inherent permeability of the
membrane which is different for different ions also decides the
membrane potential.
Ion gradient across the membrane: The difference between the
concentration of an ion inside and outside the membrane is directly
related to the potential.