Increase internal diameter of axon which decreases the internal resistance to ion flow
Increase the resistance of the plasma membrane to charge flow by insulating it with myelin.
Sodium: Decreasing the external Na + concentration reduces the size of the action potential but has little effect on the resting membrane potential. The lack of much effect on the resting membrane potential would be predicted, since the permeability of the membrane to Na + at rest is relatively low.
Potassium: Conversely, increasing the external K + concentration decreases the resting membrane potential.
It is possible to determine the minimal intensity of stimulating current (threshold intensity) that, acting for a given duration, will just produce an action potential.
Action potential fails to occur if the stimulus is subthreshold in magnitude,produces graded potentials.
Suprathreshold stimuli produce action potential during relative refractory period.