Action Potential

Neuronal conduction

The process of neurons communicating to other neurons.

Action potential

The impulse/information that is transported by the axon

Depolarization

The process where the resting potential is being made less negative

Hyperpolarization

The process where the resting potential is being made more negative.

Repolarization

The process where we are trying to go back to resting potential (-70mV)

Where does action potential get created?

In the axon hillock

Threshold of excitation

Required level of voltage in order for sodium voltage gated ion channels to open and let sodium into the cell.

The process to create an action potential:

Action potential starts with depolarization where the neuron cell reaches the threshold of excitation and sodium channels open up as a result, letting lots of sodium out of the cell to make the resting potential less negative.

Depolarization peaks/overshoots and it begins repolarization where potassium channels open and let out lots of potassium.

Too much potassium causes hyperpolarization where the resting potential is really negative and now the sodium/potassium pump has to activate to bring the neuron cell back to resting potential.

Absolute refractory period

A period where action potentials cannot be created again.

Relative refractory period

A period where an action potential can be created again if there is a stronger stimulus.

Propagation

Describes the movement of the action potential traveling from the soma to the axon terminals.

Why is myelin important?

Myelin is important because it helps speed up propagation and maintains action potential strength since it has ranvier nodes that have sodium ion channels there to essentially create small action potentials as it travels.

Ranvier

Gaps between the myelin sheaths that have sodium channels there.

Saltatory conduction

Process where the action potential leaps from one node of ranvier to another.

What happens if an axon loses myelin sheaths?

The strength of the action potential would not be able to be maintained and it can’t propagate.