What term describes the baseline electrical potential across the cell membrane when the neuron is not firing?

• A. Resting Potential
• B. Depolarization
• C. Hyperpolarization
• D. Action Potential

Answer: (A)

The baseline electrical potential across the cell membrane when the neuron is not firing is the resting membrane potential. This is a stable, negative voltage inside the cell relative to the outside (about -70 mV in many neurons) and is established by ion gradients and the membrane’s selective permeability. Potassium ions leak out more readily than sodium ions enter, pulling the inside negative, while the Na+/K+ pump maintains the gradient by moving Na+ out and K+ in. When the neuron does fire, the potential shifts toward a positive value during depolarization as voltage-gated Na+ channels open; after firing, hyperpolarization can occur when the potential becomes more negative than the resting level; the rapid event of firing itself is the action potential. So the baseline, nonfiring state is the resting membrane potential.