Question

Ligand-gated channels on the postsynaptic membrane open and K⁺ and Na⁺ both move through these channels in opposite directions. Why then do we measure depolarization on the postsynaptic membrane?

1) Na⁺ has a much stronger driving force into the cell.
2) K⁺ has a much stronger driving force into the cell.
3) Na⁺ has a much stronger driving force out of the cell.
4) K⁺ has a much stronger driving force out of the cell.
5) K⁺ moves out of the cell, then back into the cell.

Answer 1

Depolarization on the postsynaptic membrane is primarily due to the movement of Na+ ions into the cell through ligand-gated channels.

Step-by-step explanation:

The movement of ions across the postsynaptic membrane during neural transmission has a significant impact on the membrane potential. In the case of ligand-gated channels, such as those found on the postsynaptic membrane, the channels open in response to the binding of neurotransmitters, allowing the flow of ions. In this context, both K+ and Na+ ions can move through these channels, but the depolarization of the postsynaptic membrane is primarily caused by the movement of Na+ ions into the cell.

While both Na+ and K+ ions can move through ligand-gated channels, the driving force for Na+ ions is much stronger into the cell compared to K+ ions. This is due to the concentration gradient of Na+ as well as the electrical potential across the membrane. As a result, the movement of Na+ ions into the cell during neural transmission leads to depolarization of the postsynaptic membrane.