Initiation of nerve impulse occurs at the axon hillock because:

Initiation of nerve impulse occurs at the axon hillock because:

A. 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

Answer is A. It has a lower threshold than the rest of the axon.

Axon hillock is the initial segment of the axon. Nerve impulses begin in this initial segment of the axon, and not on the somal membrane adjacent to the excitatory synapses.

The primary reason for this being that the membrane at the axon hillock has several times greater concentration of voltage gated sodium channels and therefore the threshold for excitation at this site is lower than at the rest of the neuron.