Resting membrane potential is maintained due to

**Core Concept**
Resting membrane potential is the difference in electrical charge between the inside and outside of a neuron when it is at rest, typically around -70 millivolts. This potential is crucial for the initiation of action potentials, and its maintenance is essential for proper neuronal function.

**Why the Correct Answer is Right**
The resting membrane potential is primarily maintained by the movement of ions, particularly potassium (K+), across the cell membrane. The cell membrane is more permeable to K+ ions than to sodium (Na+) ions due to the presence of specialized potassium channels. As a result, K+ ions tend to leave the cell, creating a negative charge inside the cell relative to the outside. This movement of K+ ions is facilitated by the sodium-potassium pump, which actively transports three Na+ ions out of the cell for every two K+ ions it brings in. This process contributes to the maintenance of the resting membrane potential.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the maintenance of resting membrane potential. The "action potential" is a different phenomenon that involves a rapid depolarization and repolarization of the cell membrane.

**Option B:** This option is incorrect because the "sodium-calcium exchanger" is involved in the regulation of calcium levels in the cell, not the maintenance of the resting membrane potential.

**Option C:** This option is incorrect because the "sodium-potassium ATPase" is indeed involved in the maintenance of the resting membrane potential, but it is not the primary reason for the resting membrane potential. The sodium-potassium pump helps to maintain the ion gradients that contribute to the resting membrane potential.

**Clinical Pearl / High-Yield Fact**
The resting membrane potential is essential for proper neuronal function, and its disruption can lead to various neurological disorders, including epilepsy and neuropathic pain.

**Correct Answer: C. The sodium-potassium pump helps to maintain the ion gradients that contribute to the resting membrane potential.**