Action potential (ms mV)

Action potential (ms mV)

1. Resting potential/ polarised

   • ATP pump, 2K+in, 3Na+out
   • -60mV potential difference inside membrane compared to outside membrane means it is polarised
   • More permeable to K+ than Na+
   • Kinetic E. opens Na+ channels
     • Na+ floods in down electrochemical gradient, converting it to electrical E.
       • If it reaches -50mV (threshold potential) then will go to depolarisation
     • (Na+ and K+ gated channels were both closed before)
   • (net - inside, net + outside)
   • K+channels open, K+ going out

2. Depolarisation

   • ATP pump, 2K+in, 3Na+out
   • K+channels open, K+ going out
   • +40mV potential difference inside membrane compared to outside membrane means it is depolarised
   • (net + inside, net - outside)

3. Repolarisation

   • ATP pump, 2K+in, 3Na+out
   • K+channels open, K+ going out
   • K+ gated channels open, K+ flows out down electrochemical gradient
     • More flows out than needed meaning it becomes hyperpolarised

4. Hyperpolarisation

   • ATP pump, 2K+in, 3Na+out, and permeability starts to restore balance
     • (Not able to register any more pain until back to resting potential)
   • K+channels open, K+ going out
   • K+ gated channels close