Neurons generate and conduct electrical signals by pumping positively charged ions (Na+ and K+) across their membrane

• The unequal distribution of ions on different sides of the membrane creates a charge difference called a membrane potential
  

A resting potential is the difference in charge across the membrane when a neuron is not firing

• In a typical resting potential, the inside of the neuron is more negative relative to the outside (approximately –70 mV)
  

The maintenance of a resting potential is an active process and is controlled by sodium-potassium pumps

• The sodium-potassium pump is a transmembrane protein that actively exchanges sodium and potassium ions (antiport)
  

• It expels three Na+ ions for every two K+ ions admitted (additionally, some K+ ions will then leak back out of the cell)
  

• This creates an electrochemical gradient whereby the cell interior is relatively negative compared to the extracellular environment (as there are more positively charged ions outside of the cell)
  

• The exchange of sodium and potassium ions requires the hydrolysis of ATP (it is an energy-dependent process)
  

Sodium-Potassium Pump