## **Core Concept**
The initiation of an impulse in a neuron typically starts at the **axon hillock**, also known as the initial segment. This region has a high concentration of voltage-gated sodium channels, making it the site where the action potential is most easily generated.

## **Why the Correct Answer is Right**
The axon hillock has a high density of **voltage-gated sodium channels**, which are crucial for the initiation of the action potential. When the neuron receives sufficient excitatory input, the membrane potential at the axon hillock reaches threshold, leading to the opening of these sodium channels and the rapid depolarization characteristic of an action potential. This region acts as the **integration site** for all incoming signals, determining whether an action potential will be generated.

## **Why Each Wrong Option is Incorrect**
* **Option A:** Dendrites are primarily involved in receiving synaptic inputs from other neurons. They do not typically initiate action potentials due to a lack of voltage-gated sodium channels.
* **Option B:** The cell body (soma) contains the nucleus and the machinery for protein synthesis but is not specialized for the initiation of action potentials.
* **Option D:** The terminal buttons (or axon terminals) are involved in neurotransmitter release and are located at the end of the axon, far from where an action potential is initiated.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the **axon hillock** is the site of action potential initiation due to its high concentration of voltage-gated sodium channels. This is a critical concept in understanding neuronal physiology and is often tested in various medical exams.

## **Correct Answer:** C. Axon hillock.