Action Potential

• Using the graph, describe how an AP happens (focus on the types of polarisation) P1

  1. Neurone resting potential is -70mV
  2. Stimulus opens some Na+ channels
  3. Na+ enters the neurone
  4. When the threshold potential is reached (-50mV), all Na+ channels open -> depolarisation (more Na+ enters neurone)
  5. When pd reaches +40mV, all voltage-gated Na+ channels close & all K+ channels open
• Using the graph, describe how an AP happens. P2

  1. Repolarisation happens (K+ leaves neurone - inside of neurone becomes more negative, slowly returning to resting potential)
  2. K+ channels close slowly, so too much K+ leaves-> pd below -70mV = hyperpolarisation
  3. Sodium-potassium pumps return neurone to resting potential (-70mV)
• What is the refractory period?

  Na+ and K+ cant be stimulated
• Whats the purpose of refractory period?

  Prevents backwards stimulation of neurone