Which of the following would be likely to cause depolarization of a neuron?

• A. Closing of calcium channels
• B. Opening of chloride channels
• C. Opening of potassium channels
• D. Opening of sodium channels

Answer: (D)

Verified step by step guidance

1. Understand the concept of depolarization: Depolarization is a change in a cell's membrane potential, making it more positive. In neurons, this is typically the initial phase of an action potential.
2. Identify the role of sodium channels: Sodium ions (Na+) are positively charged. When sodium channels open, Na+ flows into the neuron due to the concentration gradient and electrical gradient, making the inside of the neuron more positive.
3. Consider the effect of opening sodium channels: Opening sodium channels allows Na+ to enter the neuron, which increases the positive charge inside the cell, leading to depolarization.
4. Evaluate the other options: Closing calcium channels would not directly cause depolarization. Opening chloride channels would typically cause hyperpolarization, as Cl- ions are negatively charged. Opening potassium channels usually leads to hyperpolarization, as K+ ions exit the cell.
5. Conclude that opening sodium channels is the most likely cause of depolarization, as it directly increases the positive charge inside the neuron, moving the membrane potential towards the threshold for an action potential.