+30
Repolarization
0
Depolarization
3
Hyperpolarization
-55
-70
7
Time
© Project Lead The Way, Inc. 2022
CELL EXTERIOR
CELL INTERIOR
With potassium channels open, the relative voltage
inside the cell falls in a process called
repolarization, and the neuron’s membrane
potential drops back toward resting potential.
A stimulus is applied to the cell, causing
the membrane potential to rise.
The open potassium channels cause
neuron to overshoot resting potential
and the cell becomes
hyperpolarized, meaning the
membrane potential has dropped
below its resting potential.
The resting membrane potential
of a neuron is usually around -70mV.
Sodium
Channel
CELL INTERIOR
When threshold is reached, a large number of
sodium channels open, allowing positively charged
sodium ions into the cell. This causes depolarization
of the neuron as the membrane potential rises to 0
and then becomes positive.
The action potential reaches its peak.
Sodium channels close and potassium
channels open, which allows
potassium to flow out of the cell.
CELL INTERIOR
The potassium channels close and the
sodium-potassium pump allows the membrane to
return to resting membrane potential, ready to be
activated again.
CELL EXTERIOR
Potassium
Channel
After stimulation, the neuron reaches
what is known as its threshold
membrane potential. This is
generally around -55 mV.
SodiumPotassium
Pump
CELL EXTERIOR
Na + ion
© Project Lead The Way, Inc. 2022
K+ ion