This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Excitation and Action Potiential, Subject name: Physiology
[{'content': 'Initiation of nerve impulse occurs at the axon hillock because: \nSelect and explain. \nA. It has a lower threshold than the rest of the axon, B. It is unmyelinated, C. Neurotransmitter release occurs here, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The membrane of the axon hillock/initial segment contains a high density of voltage-gated Na+ and K+ channels. These channels are fewer along the dendrites and cell body. The axon hillock has a lower threshold for firing an action potential. This region is also known as the trigger zone for the action potential. It requires a relatively low degree of depolarization for initiation of spike at the axon hillock/initial segment.', 'role': 'assistant'}]