Nerve impulses

• What is the voltage of resting potential?

  65mV
• How is the axon charged in a resting potential?

  The inside is negatively charged compared to the outside
• What is the term for the axon in the resting potential?

  Polarised
• How is the resting potential maintained?

  The sodium-potassium pump

  • 3 sodium ions are actively transported out while 2 potassium ions are actively transported into the axon
  • More sodium ions move in than potassium ions
  • An electrochemical gradient is established between the outside and inside of the axon
  • Sodium ions diffuse naturally back into the axon while potassium ions diffuse out of the axon
• What causes an action potential?

  A stimulus causes sodium ion channels to open, so an influx of sodium ions enter the cell

  Eventually the voltage-gated sodium channels close and the voltage-gated potassium channels open

  This causes repolarisation

  But too many usually diffuse out causing hyperpolarisation, as the axon is more negative than usual
• What is the term for the re-establishment of the resting potential?

  Repolarisation