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A pseudounipolar neuron (pseudo - false, uni - one) is a sensory neuron in the peripheral nervous system. This neuron contains a long dendrite and a short axon that connects to the spinal cord. The dendrite and axon are sometimes called distal process and proximal process, respectively.
The dendrite of a pseudounipolar neuron
By definition a pseudounipolar neuron has one dendrite and one axon. Just as for every neuron, the dendrite conducts nerve impulses toward the cell body, and the axon conducts them away from the cell body. However, the dendrite of a pseudounipolar neuron is structurally and functionally an axon, except at its terminal part where it contacts a specialized sensory organ. When the sensory organ transduces information, it initiates an action potential that is propagated toward the cell body. Because the dendrite functions as an axon, this potential does not degrade, but reaches the axon unabated and continues toward the central nervous system.
Because of the similarity between this dendrite and an axon, some authors describe the pseudounipolar neuron as having one process that leaves the cell body, an axon. The dendrites are placed "on top of" the axon, connected with the receptors.
In pictures, the dendrite can be both called dendrite and axon. Both pictures show that this dendrite/axon is myelinated.
The dendrite of these neurons is located in the nerves coming from the body. The cell bodies are located in the dorsal root ganglion just next to the spinal cord. The axons protrude through the dorsal root and into the posterior horn of the spinal cord.
The signal is conducted through the nerve (dendrite) to the dorsal root ganglion (cell body), then through the dorsal root (axon) ending at the sensory nuclei in the posterior horn of the spinal cord.
- Diagram at ccccd.edu
- n_07/12569975 at Dorland's Medical Dictionary
- unipolar+neuron at eMedicine Dictionary