The membrane of an axon consists of three main protein channels: the sodium/potassium pumps, voltage-gated sodium channels and voltage-gated potassium channels. These play a role in establishing the membrane potential. The sodium potassium pump, actively pumps 3 sodium ions (Na+) outside of the neurone and 2 K+ inside the cell. This causes a net difference across the axon, with the inside being slightly negative compared to the outside of the axon. The axon is also more permeable to K+ in comparision to Na+. Therefore, potassium will also leak out of the axon (contributing to the further negative state of the axon). The axon is more permeable to K+ as more K+ channels are open whilst most of the sodium channels are closed. Typical resting potential in a human: -70 mV.