Co-ordination

sodium potassium pump 

3 sodium out - 2 potassium in 

more potassium leakage channels - membrane more permeable to 

results in more sodium on outside + more postassium inside

overall more ions outside of the axon

inside of the membrane is negative in relation to the outside

Stimulus causes Na voltage gated channels to open

influx of Na 

Depolarisation - reversal of change - now positive in inside relation to the outside +40mV = Action Potential

K voltage gated channels out

influx of K 

repolarises the axon 

hyperpolarisation - K channels stay open longer than needed

all channels shut

resting potential restored

The reversal of charge causes a localised current which causes the Na channels in the adjactent area to open, so the next section gets repolarised

the section behind - the K channels open so that bit gets repolarised then hyperpolarisared 

this delays the next action potential from being passed to close to the first 

the K channels then shut so that the resting potential is restored ready for next action potential

this way the action potential only moves in one direction - towards the axon terminals, otherwise it could span out in both directions

factors

Myelinated/unmyelinated - if there is not myelin then the action potential/localised current can jump from one node of ranvier to the other as myelin is an insulator = saltatory conduction

Diametre of an axon - only for unmyelinated because the charge meets less resitence as less is in contact with the membrane in relation to the amount of charge running through

Temperature - increases the rate of diffusion of ions through the cell membrane as ions have more KE so will move faster when channels open