the resting potential

• When a neurone is not conducting a nerve impulse or action potential it is said to be resting.
• When the electrical activity in the axon of a resting neurone is measured, the inside of the axon is negatively charged compared to the outside. This difference is termed the potential difference and measures -70 millivolts (mV). This difference is termed the resting potential and indicates that the inside of the axon membrane is 70 times more negative compared to the outside. the membrane is said to be polarised
• the resting potential is maintained by the sodium / potassium pumps and sodium-potassium leakage channels
• The sodium/potassium pump

  • a carrier protein which actively transports Na+ out of the cell and K+ into the cell.
  • For every 3 Na+ which move out of the cell 2 K+ move into the cell.
  • The Na+ and K+ are moving against a concentration gradient and therefore ATP is needed.
• Sodium-potassium leakage channels

  • believed to be always open in a resting membrane.
  • Both Na+ and K+ ions diffuse through these channels, however, about 100 times more K+ diffuse out than Na+ diffuse in.
  • This means that the membrane is more permeable to K+ than Na+. this is called partial permeability