What does a change in potassium (K) influence in terms of membrane functionality?

A change in potassium (K) concentration significantly influences the resting membrane potential of cells. Resting membrane potential is primarily determined by the distribution of ions across the cell membrane, particularly potassium. The Nernst equation shows that the resting membrane potential is mainly influenced by the equilibrium potential of potassium ions, as these ions can readily move across the membrane due to the permeability of typical cell membranes to K+.

When the concentration of potassium outside the cell decreases (hypokalemia), the resting membrane potential becomes more negative, pushing it further away from the threshold required for depolarization. Conversely, when potassium levels outside the cell increase (hyperkalemia), the resting membrane potential becomes less negative, which can bring it closer to depolarization threshold and may contribute to an increased risk of spontaneous action potentials.

Thus, alterations in potassium levels directly impact the resting membrane potential, shaping the excitability of the membrane and influencing how readily a cell can respond to stimuli. This is crucial in various physiological processes, including muscle contraction and neuronal activity, where precise control of membrane potential is essential for normal function.