The resting potential of a nerve is what:

The resting potential of a nerve is what:

• A. +30mV
• B. -70mV
• C. -120mV
• D. +50mV

Answer: (B)

Resting membrane potential is the stable, negative voltage across a neuron's membrane when it’s not signaling. Neurons sit around -70 millivolts inside relative to the outside. This negativity comes from the ion gradients and how permeable the membrane is to those ions. The Na+/K+ pump keeps the gradients by moving three Na+ ions out for every two K+ ions in, using energy. At rest, the membrane is more permeable to potassium due to leak channels, so K+ tends to leave the cell. As positive charges exit, the inside becomes more negative. Potassium’s equilibrium potential is about -90 mV and sodium’s is about +60 mV, so the resting potential settles somewhere around -70 mV because potassium leakage dominates but sodium leakage and the pump prevent it from reaching -90 mV. That’s why a resting neuron is negative inside. The other values reflect different states: a positive value like +30 mV or +50 mV indicates depolarization or the peak of an action potential, not rest, while a much more negative value (around -120 mV) would be unusually hyperpolarized for normal neuronal function.

Resting membrane potential is the stable, negative voltage across a neuron's membrane when it’s not signaling. Neurons sit around -70 millivolts inside relative to the outside. This negativity comes from the ion gradients and how permeable the membrane is to those ions.

The Na+/K+ pump keeps the gradients by moving three Na+ ions out for every two K+ ions in, using energy. At rest, the membrane is more permeable to potassium due to leak channels, so K+ tends to leave the cell. As positive charges exit, the inside becomes more negative. Potassium’s equilibrium potential is about -90 mV and sodium’s is about +60 mV, so the resting potential settles somewhere around -70 mV because potassium leakage dominates but sodium leakage and the pump prevent it from reaching -90 mV.

That’s why a resting neuron is negative inside. The other values reflect different states: a positive value like +30 mV or +50 mV indicates depolarization or the peak of an action potential, not rest, while a much more negative value (around -120 mV) would be unusually hyperpolarized for normal neuronal function.