Hypokalemia causes:

Decreasing the external (hyponatremia) reduces the size of the AP but has little effect on RMP. Decrease in extracellular (hypocalcaemia) increases the excitability of nerve and muscle cells by increasing the permeability of sodium channels. <50% of normal cause spontaneous discharge in some peripheral nerves known as "tetany". An increase in extracellular (hypercalcemia) can stabilize the membrane by decreasing excitability If the extracellular level of K+ is increased (hyperkalemia), the resting potential moves closer to the threshold (depolarisation) for eliciting an action potential and the neuron becomes more excitable. If the extracellular level of K+ is decreased (hypokalemia), the membrane potential is reduced and the neuron is hyperpolarized.