Which of the following will occur when a neuron depolarizes?

• A. The neuron returns to its resting membrane potential.
• B. The membrane potential becomes less negative as sodium ions (Na^+) enter the cell.
• C. Potassium ions (K^+) rapidly enter the neuron, making the inside more negative.
• D. Calcium ions (Ca^{2+}) are pumped out of the neuron, causing hyperpolarization.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the concept of depolarization in neurons. Depolarization occurs when the membrane potential of a neuron becomes less negative compared to its resting state. This is a key part of the action potential process in nerve signaling.
2. Step 2: Recall the role of sodium ions (Na⁺) during depolarization. Sodium channels in the neuron's membrane open, allowing Na⁺ ions to flow into the cell. This influx of positively charged ions reduces the negativity of the membrane potential.
3. Step 3: Eliminate incorrect options. For example, potassium ions (K⁺) do not rapidly enter the neuron during depolarization; instead, they exit the neuron during repolarization. Similarly, calcium ions (Ca²⁺) are not involved in depolarization but play a role in neurotransmitter release.
4. Step 4: Focus on the correct option. The correct answer is that the membrane potential becomes less negative as sodium ions (Na⁺) enter the cell. This is the defining characteristic of depolarization.
5. Step 5: Relate this process to the overall function of neurons. Depolarization is the first phase of an action potential, which allows neurons to transmit electrical signals along their axons and communicate with other cells.