Final answer:
The neuroglia is not a part of a neuron's structure; neurons consist of a cell body (soma), dendrites, an axon, and the synaptic cleft, with neuroglia serving as supportive cells.
Step-by-step explanation:
The part of a neuron that is not a part of its structure is the neuroglia. Neurons are composed of a cell body, or soma, which contains the nucleus and other organelles necessary for the cell's survival. Dendrites are tree-like structures branching off from the soma and serve to receive signals from other neurons at specialized junctions known as synapses. The axon is a long tail-like structure that carries electrical signals away from the neuron to another neuron or to a target cell like a muscle or gland. The process of signal transmission between neurons or from a neuron to its target occurs across a gap known as the synaptic cleft. Neuroglia, or glial cells, do not transmit signals but rather support and protect neurons, providing a supportive scaffolding, insulation with the myelin sheath, and regulation of the chemical environment.