The three main parts of a neuron are the cell body, dendrites, and axon. The cell body contains the nucleus and organelles, serving as the metabolic center of the neuron. Dendrites are branched extensions that receive signals from other neurons and transmit them to the cell body. The axon is a long, thin projection that carries electrical impulses away from the cell body to other neurons, muscles, or glands. Neurons are the fundamental units of the nervous system, playing a critical role in transmitting information throughout the body, allowing for communication between different systems and processes.