Which of the following is NOT a part of a neuron?

The correct answer is glia, as glial cells are not considered part of a neuron itself. Neurons are the primary signaling units of the nervous system and consist of several key structures: dendrites, which receive signals; the soma (or cell body), which contains the nucleus; and the myelin sheath, which insulates some neurons to speed up signal transmission.

Glial cells, while crucial to the overall functioning of the nervous system, support and protect neurons but do not transmit electrical signals like neurons do. This distinction clarifies that while glial cells are an essential component of neural networks, they are not structural or functional parts of an individual neuron.