a neuron with a cell body that emits a single axonal process resulting from the fusion of two polar processes during development; at a variable distance from the cell body, the process divides into a peripheral axon branch extending outward as a peripheral afferent (sensory) nerve fiber and a central axon branch that enters into synaptic contact with neurons in the spinal cord or brainstem. With the single known exception of the neurons composing the mesencephalic nucleus of the trigeminus, unipolar neurons are the exclusive neural elements of the sensory ganglia. The lack of dendritic processes of these primary sensory neurons is only apparent: the dendritic pole of the unipolar neuron is represented by the unmyelinated terminal ramifications of the peripheral axon branch. SYN: pseudounipolar cell, pseudounipolar neuron, unipolar cell.