Which term best describes the axon hillock?

• A. Trigger Zone Where Action Potentials Start
• B. Site Where Dendrites Receive Signals
• C. Region That Creates Myelin
• D. Part That Stores Neurotransmitters

Answer: (A)

The axon hillock is the trigger zone where action potentials start. It sits at the junction of the cell body and the axon and integrates inputs from dendrites and the soma. Because this region has a high density of voltage-gated sodium channels, when the combined input depolarizes the membrane to threshold, these channels open and an action potential is generated, then propagates along the axon. Dendrites are the structures that primarily receive signals from other neurons, not the axon hillock. Myelin is formed by glial cells around the axon to speed conduction, not produced by the axon hillock. Neurotransmitters are stored in synaptic terminals and released across the synapse, not stored at the axon hillock.