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A typical neuron includes a soma, dendrites, an axon, and axon terminals. These structures support input, signal conduction, and neurotransmitter release. Neurons are excitable and conductive, and they release neurotransmitters at synapses; their capacity to divide after injury is limited. Glial cells provide structural and metabolic support and have specialized functions that vary by location. In the CNS, astrocytes contribute to the blood-brain barrier and potassium regulation, oligodendrocytes myelinate multiple axons, microglia provide immune defense, and ependymal cells line ventricles and help produce or circulate CSF. In the PNS, Schwann cells myelinate single axons and aid regeneration, while satellite cells support neurons in ganglia. The lesson also connects CNS and PNS myelin loss with multiple sclerosis and Guillain–Barré syndrome, respectively.