Imagine you can render a single neuron completely impermeable to Na (e. g. by using a drug that is a non-specific blocker of all Na channels). The other conditions of the cell (e. g. concentrations of ions in the intracellular and extracellular fluid, functioning of other ion channels) remain the same. What will happen to the cell's resting membrane potential

the resting membrane potential will decrease to become slightly more negative

Explanation:

The resting membrane potential refers to the electrical charge difference across the plasma membrane when a cell is at rest (i.e., the cell is in a non-excited state). The resting membrane potential is caused by the electrochemical gradient of ions across the cell membrane and the membrane's permeability to each type of ion. The neuron cell membrane is more permeable to potassium ion (K+) movement than sodium ion (Na+) movement, thereby the resting potential is much close to the equilibrium potential of K+. A neuron at rest is negatively charged. In consequence, if the neuron would become impermeable to Na+ (e.g., by removal of Na channels), the extra efflux of Ka+ would lead to a membrane potential to slightly more negative than the resting value, but this value would remain higher than the equilibrium potential of K+.

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