1. Resting potential

• What is resting potential?

  -the axon membrane when no impulse is being transmitted

  • measured as a value of -70mV
• How is resting potential reached?

  • Sodium potassium pump actively transports 3 Na+ out of the axon and 2 K+ into the axon, across the axon membrane
  • Voltage gated Na+ channel is closed
  • Axon membrane is impermeable to Na+, so they remain outside the axon
  • Voltage gated K+ channel is open
  • Axon membrane is permeable to K+, so they move by facilitated diffusion down a concentration gradient out of the axon
  • Large negative ions (anions) are not able to move across the axon membrane
• What is resting potential a measure of?

  A measure of the difference in potential between the outside and the inside of the axon

  • -70mV means that the inside of the axon is less positive than the outside
• Why is the inside of the axon less positive than the outside of the axon?

  -active transport of 3 Na+ out and 2 K+ in

  -facilitated diffusion moves K+ out but not Na+ in

  -there are negative ions inside the axon
• At resting potential, the axon membrane is polarised (charged)