In order for a neuron to generate an action potential, which of the following must occur?

• A. The membrane potential must reach the threshold value due to depolarization.
• B. Voltage-gated potassium channels must open before sodium channels.
• C. The neuron must be hyperpolarized beyond its resting potential.
• D. The synaptic vesicles must fuse with the postsynaptic membrane.

Answer: (A)

Verified step by step guidance

1. Understand the concept of an action potential: An action potential is a rapid electrical signal that travels along the axon of a neuron. It is initiated when the membrane potential of the neuron reaches a specific threshold value due to depolarization.
2. Review the role of depolarization: Depolarization occurs when the inside of the neuron becomes less negative (more positive) compared to its resting potential. This is typically caused by the influx of sodium ions (Na⁺) through voltage-gated sodium channels.
3. Clarify the threshold value: The threshold is the critical level of membrane potential that must be reached for an action potential to be triggered. If the membrane potential does not reach this threshold, the neuron will not fire an action potential.
4. Analyze the incorrect options: Voltage-gated potassium channels open after sodium channels, not before, to help repolarize the membrane. Hyperpolarization beyond the resting potential occurs after the action potential, not before. Synaptic vesicles fusing with the postsynaptic membrane is part of synaptic transmission, not action potential generation.
5. Conclude the correct condition: For a neuron to generate an action potential, the membrane potential must reach the threshold value due to depolarization, which is caused by the opening of voltage-gated sodium channels.