resting potential

• intro

  • neurones transmit electrical impulses, they travel along the neurone cell surface membrane
  • impulse=momentary reversal in electrical potential difference across the neurone membrane
  • electrical potential difference=voltage/difference in charge
• resting potential overview

  • -70mV
  • inside of axon has a negative electrical potential compared to outside
  • difference in charge is due to different number of ions on each side of neurone cell surface membrane
  • difference in charge across membrane=polarised
  • inside of axon has electrical potential 70mV lower than outside
• maintaining resting potential


  1)active transport of sodium and potassium ions

  • carrier proteins(sodium-potassium pumps)are present in cell surface membrane of neurones
  • they use ATP to actively transport NA+ out of the axon and K+ into axon
  • pumped at an unequal rate: for every 3 NA+ pumped out, 2K+ are pumped in
  • this creates a concentration gradient across the membrane
• maintaining resting potential


  2)difference in membrane permeability to sodium and potassium ions

  • concentration gradient created by pump-both NA+ and K+ will diffuse back across membrane
  • the cell membrane of axons have sodium and potassium channels that allow movement via facillitated diffusion
  • the neurone membrane is less permeable to NA+, so K+ can diffuse out at a faster rate than NA+ can diffuse back in

  =more positive ions on outside of neurone than inside

  =resting membrane potential is -70mV