What is Happening When a Neuron is at Rest Before

Question

What is happening when a neuron is at rest before an action potential?
A) The membrane is depolarized.
B) Membrane ion channels are open.
C) Potassium is diffusing out of the cell.
D) The inside of the neuron is negative relative to just outside the neuron.

Accepted Answer

At rest, the neuron is polarized, meaning the inside of the neuron is negative relative to just outside the neuron. This is maintained by the sodium-potassium pump, which pumps three sodium ions out of the cell for every two potassium ions pumped in. At rest, membrane ion channels are closed, preventing the free flow of ions across the membrane. While potassium does eventually diffuse out of the cell, this is not the primary cause of the polarization at rest.