Resting Potentials

• Resting Potentials

  Neurones transmit electrical impulses which travel rapidly along the neurone cell surface membrane from one end of the neurone to the other
• Resting potential

  • Inside of the axon always has a negative electrical potential compared to the outside of the axon
  • Potential difference (when there are no impulses) is usually about -70mV
  • The inside of the axon has an electrical potential about 70mV lower than the outside
• Factors contributing to establishing and maintaining the resting potential

  1. Active transport of sodium ions and potassium ions

  2. Differential membrane permeability
• Active transport of sodium ions and potassium ions

  Carrier proteins called sodium-potassium pumps are present in the membranes of neurones<|>Pumps use ATP to actively transport 3 sodium ions out of the axon for every 2 potassium ions they actively transport in<|>This means that there is a larger concentration of positive ions outside the axon than there are inside the axon<|>The movement of ions via the sodium-potassium pumps establishes an electrochemical gradient
• Differential membrane permeability

  The cell-surface membrane of neurones has selective protein channels that allow sodium and potassium ions to move across the membrane by facilitated diffusion<|>The protein channels are less permeable to sodium ions than potassium ions<|>This means that potassium ions can diffuse back down their concentration gradient, out of the axon, at a faster rate than sodium ions
• The resting potential is maintained by the net movement of positively charged ions out of the axon
• The resting potential is maintained by a sodium-potassium pump which requires ATP energy from respiration in order to actively pump sodium and potassium across the membrane