What is primarily responsible for the resting potential of a neuron?

• A. Ion transport proteins
• B. Distribution of ions across the cell membrane
• C. Presence of neurotransmitters
• D. Osmotic pressure within the neuron

Answer: (B)

The resting potential of a neuron is primarily determined by the distribution of ions across the cell membrane. At rest, neurons maintain a specific concentration gradient of ions, particularly sodium (Na+) and potassium (K+), which are crucial for establishing the resting membrane potential. The inside of the neuron is typically more negatively charged than the outside, primarily due to the high concentration of potassium ions inside the cell and the more significant movement of sodium ions into the cell when channels are opened.

This differential distribution of ions is maintained by various mechanisms, including the sodium-potassium pump, which actively transports sodium out of the cell and potassium into the cell, thus contributing to the charge separation that defines the resting potential. Resting potentials are typically around -70 mV, and the specific ion gradients are essential in this regard.

While ion transport proteins and osmotic pressure do play roles in maintaining the potential, the crux of the resting membrane potential lies in how ions are distributed across the neuronal membrane and the selective permeability of that membrane to different ions. The presence of neurotransmitters is more related to synaptic transmission rather than the maintenance of resting potential itself.