Passage of an action potential

• How do action potentials pass across an unmyelinated axon?


  At resting potential, the concentration of sodium ions outside the axon membrane is high compared the inside, and vice versa for potassium ions, the axon is polarised

  A stimulus causes a sudden influx of Na+. The membrane becomes polarised

  The electrical currents made by the influx of Na+ causes the opening of sodium voltage-gated channels. Depolarisation is established behind

  This repeats
• How does an action potential cross a myelinated axon?

  Saltatory conduction -

  • Current jumps between nodes of ranvier
  • This is faster as depolarisation won’t have to occur all along the axon
• At resting potential, are there more Na+ ions outside the membrane or inside?

  Outside
• At resting potential are there more K+ ions inside the membrane or outside the membrane?

  Outside
• The influx of what ion into the axon causes depolarisation?

  Sodium
• What happens behind the region of depolarisation?

  Sodium ion channels close and potassium channels open