Passage of an action potential Aim: To understand how nerve impulses are propagated along a neurone

Recap of action potential

“Movement” of an action potential Once an action potential has been created it passes down the axon The initial action potential and depolarisation of the membrane stimulates an action potential in the next region of the axon Reversal of charge across the membrane is reproduced along the axon

Passage of an action potential along an unmyelinated axon Resting potential: High Na+ concentration outside High K+ concentration inside Inside negative relative to outside Axon membrane polarised

Passage of an action potential along an unmyelinated axon Stimulus received Influx of sodium ions Membrane depolarised – action potential started

Passage of an action potential along an unmyelinated axon Localised electrical circuits form Influx of sodium causes opening of sodium voltage-gated channels further along

Passage of an action potential along an unmyelinated axon Action potential propagated along the neurone. Areas that have become depolarised become repolarised due to movement of K+ outside of the membrane Sodium-potassium pump starts back up returning membrane to resting potential

Passage of an action potential along a myelinated axon Fatty sheath of myelin around axons act as insulator preventing action potentials forming. Breaks in sheath (called nodes of Ranvier) at intervals of 1-3mm Action potentials occur at these points and jump from node to node. This process is called saltatory conduction. This speeds up the passage of the action potential.