Final answer:
The myelin sheath serves as the protective coating of a neuron, speeding up the transmission of nerve impulses along the axon. The dendrites receive signals while the axon transmits them away from the cell body.
Step-by-step explanation:
The part of the neuron that serves as the protective coating is the myelin sheath. This insulating layer is made up of a fatty substance called myelin, which is produced by a type of glial cell known as Schwann cells or oligodendrocytes, depending on whether the neuron is in the peripheral nervous system (PNS) or the central nervous system (CNS). The myelin sheath wraps the axon, functioning like the plastic insulation on an electrical wire, allowing nerve impulses to travel rapidly along the axon. Neurons without this layer conduct signals much more slowly. The presence of regularly spaced gaps in the myelin sheath, known as the nodes of Ranvier, further facilitate the fast transmission of nerve signals.
By contrast, dendrites are extensions of the neuron that receive signals from other neurons and transmit them towards the cell body, or soma. The axon is the part of a neuron that transmits an electrical signal from the cell body to a target cell. The operational role of a neuron is to receive stimuli through its dendrites, process it in the cell body, and transmit the signal along the axon to another neuron, muscle, or glandular cell at the synapse, where communication occurs via neurotransmitters.