Understanding Resting Membrane Potential: Key Concepts and Clinical Significance
…Till I Breathe My Last
It is the potential difference recorded across the cell membrane at rest.
Ionic distribution across the cell membrane:
- Inside: High K+, low Na+ & Cl-
- Outside: High Na+ & Cl-, low K+
Factors contributing to resting membrane potential:
- Selective permeability of ions across the plasma membrane: High permeability to K+, low permeability to Na+
- Ion gradients established and maintained by ion pumps: Sodium/Potassium pump (Na+/K+ATPase)
Key Points:
- Excitable cell membranes are polarized at rest with positive charges lined up along the outside of the membrane and negative charges along the inside.
- At rest, Na+ and Cl- are more outside the cell membranes, while K+ and negatively charged proteins are more inside the membrane.
- The difference in concentration of ions causes polarity in the cell membrane.
- The difference in concentrations of ions around the membranes is controlled by ion pumps.
- During the action potential, this polarity is abolished and for a brief period, is actually reversed.
Clinical Significance:
- Hyperkalemia: Increase in K+ concentration in the extracellular fluid. Resting potential moves closer to the threshold for eliciting an action potential.
- Hypokalemia: Decrease in K+ concentration in the ECF. Membrane potential is reduced, and the neuron is hyperpolarized.
