Resting membrane potential, the action potential and nerve conduction

At a glance

• The resting membrane potential (about −70 mV in neurons, −90 mV in skeletal and ventricular muscle) exists because the Na⁺/K⁺-ATPase keeps potassium high inside, and the resting membrane lets potassium leak out far more easily than sodium leaks in.
• An action potential is an all-or-none event: voltage-gated sodium channels open at threshold (about −55 mV), then inactivate within about 1 ms while potassium channels repolarise the cell.
• Conduction velocity rises with axon diameter and myelination. Myelinated axons conduct by saltatory conduction between nodes of Ranvier.