Transmission of an action potential along a non myelinated axon.

https://www.youtube.com/watch?v=FjcH6UovKfE

What happens after region A has undergone an action potential.

Sodium ions now move sideways from Region A towards region B, attracted to the negative charge. this is called the localised electrical circuit.

This causes voltage gated sodium ion channels to open in region B, sodium ions diffuse into axon in region B, causes region B to depolarise.

What happens once region B depolarises

In region A , the voltage gated sodium ion channels close , and voltage gated potassium ion channels open. Potassium ions now diffuse out of the axon in region A , so region A begins to repolarise.

What happens along the axon,

A wave of depolarisation makes its way along the axon, once a region has depolarised, it then has to be repolarised back to the resting potential.

Key idea

Once a region of the membrane has transmitted an action potential , there is a short period of time during which it cannot transmit another action potential.

This is called the refractory period.

Why does the refractory period occur

Once an action potential has passed a region of membrane, the membrane then has to repolarise, this takes a certain amount of time .

Secondly, once voltage gated sodium ion channels have closed , they cannot open again for a short period of time.

So there is a time delay before the membrane can transmit a second action potential.

Why is the refractory period important

Because the axon membrane enters the refractory period once it transmits an action potential, this ensures that the action potential can only travel in one direction.

Secondly, the refractory period means that action potentials are clearly separated from each other and cannot overlap.

Lastly, because there is a time delay between each action potential, this limits the number of action potentials that can be transmitted during a time period.