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Action potential

• Equilibrium potential (of an ion): PD at which ion ceases to flow down electrochemical gradient (Nernst equation)
• Resting membrane potential: PD across cell membrane (calculated by Goldman equation) - takes into account equilibrium potentials of all ions

  Normal cell RMP = -70mV (interior of cell is negatively charged with respect to exterior)
  N/K pump 3/2 helps maintain ionic balance

• Action Potential

  

  Rapid change in membrane potential (depolarisation) following a stimulus with rapid return to resting membrane potential
  All-or-none phenomenon

  Depolarisation = Na influx (opening of Voltage-gated Na channels)
  Repolarisation = K efflux (opening of Voltage-gated K channels)
  Ionic balance maintained by 3Na/2K-ATPase

  Refractory Period: Period of time after AP that AP cannot be propagated

• Myelination

  - Increased condution velocity
  Saltatory conduction at nodes of Ranvier

Types of Nerve Fibres

1. Group A - largest myelinated
2. Group B - Myelinated autonomic preganglionic
3. Group C - Unmyelinated postganglionic fibres

Drugs affecting neurotransmission

1. Na-channel blockers - LAs
2. K-channel blockers - Tetraethylammonium