In a resting mammalian neuron, these channels allow K+
to pass in either direction across the membrane.
- Because the concentration of K+ is much higher inside the cell, the chemical concentration gradient favors a net outflow of K+.
- However, since the potassium channels allow only K+ to pass, Cl- and other anions inside the cell cannot accompany the K+ across the membrane.
As a result, the outflow of K+ leads to an excess of negative charge inside the cell.
This buildup of negative charge within the neuron is the source of the membrane potential.