the plasma membrane of a neuron

separates the extracellular space from the intracellular space

sodium ions are found in high concentration

outside of the cell whereas potassium ions are found in high concentration

inside of the cell. Voltage-gated

sodium channels, sodium potassium ATP-ase pumps

and voltage-gated potassium channels

are found embedded in the plasma membrane of the neuron.

To initiate an action potential

a stimulus causes the wave a positive charge to reach

voltage-gated sodium channels on the neuron membrane. The increase in positive

charge

causes the voltage-gated sodium channels to open. Positively charged sodium ions

flood into the neuron following their concentration gradient

this causes the inside a membrane near to the open sodium channel to become

more positively charged

this process is the deep polarization of the cell membrane

The build up a positive charge on the inside of the membrane eventually causes

the voltage-gated

sodium channels to close. At the same time

voltage-gated potassium channels open since open only when the inside

remember is that maximum positive charge. Positively charged

potassium ions flow rapidly out of the neuron following their concentration

gradient this decreases the level of positive charge

on the inside surface of the neuron. This return of the membrane to resting

levels of negative

charge is called repolarization. Once

the region and the membrane has been fully repolarized, potassium

channels close

a sodium/potassium pump

uses ATP energy to restore the concentration gradient

and put potassium and sodium to the resting values

Let's summarize the processes of generating an action potential

resting potential is the membrane

potential of a neuron when it is at rest. The resting potential is well below

zero

to initiate an action potential the stimulus causes a slight depolarization

or increase in positive charge. If the stimulus is strong enough to cause the

membrane potential to reach a certain threshold

action potential will begin. In the rising phase of an action potential

wilted kid sodium channels open and sodium ions flow into the cell

this causes voltage to increase inside the cell

During the following phase of the action potential

voltage-gated sodium channels close, voltage-gate potassium channels open

the opening of the potassium channels causes potassium ions to diffuse out of the cell

rapidly

causing a sharp decrease in voltage. During the recovery phase

sodium potassium ATP-ase pump restores the resting potential

sodium potassium ATP-ase pumps

pump 2 sodium ions in and 3 potassium ions out

of the neuron. Sodium potassium ATP-ase pumps require ATP to function