Ionic Permeability and Membrane Potential

In Chapter 5, we learned that membrane potential is governed by the relative permeability ofthe cell membrane to sodium and potassium, as specified by the Goldman equation. If sodium permeability is greater than potassium permeability, the membrane potential will be closer to ENa than to EK. Conversely, if potassium permeability is greater than sodium permeability, Em will be closer to Ek. Until now, we have treated ionic permeability as a fixed characteristic of the cell membrane. However, the ionic permeability of the plasma membrane of excitable cells can vary. Specifically, a transient, dramatic increase in sodium permeability underlies the generation of the basic signal of the nervous system, the action potential.

0 0

Post a comment