Which mechanism is responsible for maintaining the resting potential of a nerve fiber?

The mechanism responsible for maintaining the resting potential of a nerve fiber is the Na+/K+ pump. This integral membrane protein works by actively transporting sodium ions out of the cell and potassium ions into the cell, typically in a ratio of three sodium ions expelled for every two potassium ions brought in. This active transport process is essential because it helps establish and maintain the differences in ion concentrations across the neuron's membrane, contributing to the negative resting membrane potential.

At rest, the inside of the nerve fiber is more negative compared to the outside due to the higher concentration of potassium ions inside the cell and the higher concentration of sodium ions outside. The Na+/K+ pump helps to counteract the natural tendency of sodium ions to diffuse into the cell and potassium ions to leak out, thereby preserving the resting potential necessary for proper excitability and conductivity of the nerve fiber. This continuous operation of the pump is crucial for the nerve cell's ability to respond to stimuli and propagate action potentials effectively.