What are pseudounipolar neurons?

• A. A motor neuron with two dendrites
• B. An interneuron in the CNS
• C. A specific type of sensory neuron found in the PNS, with a single process extending from the cell body that splits into an axon to the CNS and a dendrite to the PNS
• D. A neuron that only exists in the brain

Answer: (C)

Pseudounipolar neurons are a type of sensory neuron in the peripheral nervous system characterized by a single process that emerges from the cell body and then splits into two branches: a peripheral branch that goes to sensory receptors in the skin, muscles, or organs, and a central branch that projects into the CNS (often the dorsal horn of the spinal cord or brainstem). The cell body sits in a dorsal root ganglion, and while it looks like there’s one process, that single process actually bifurcates into the peripheral and central pathways. This arrangement lets a single neuron directly relay sensory information from the periphery into the central nervous system.

This fits because these cells function as primary sensory neurons of the PNS. The other descriptions don’t match: motor neurons are usually multipolar and connect CNS to muscles; interneurons reside within the CNS and are not the peripheral sensory cells described here; and a neuron that exists only in the brain would not be the peripheral sensory neuron that transmits information from the body to the CNS.