| Unipolar neuron | |
|---|---|
 1: Unipolar 2: Bipolar3: Multipolar 4: Pseudounipolar | |
 Example of several unipolar neurons from a nerveganglion of avelvet worm (a primitive arthropod). The neurons were stained for serotonin immunoreactivity, and photographed using a confocal microscope, with multiple images overlaid and color-coded according to depth. Arrows mark the peripherally located cell bodies of several neurons, whose neurites extend into the centralneuropil (np), where their complex ramifications are indiscernible. Scale bar: 50 micrometres.[1] | |
| Details | |
| Identifiers | |
| Latin | neuron unipolare |
| TH | H2.00.06.1.00046 |
| FMA | 67278 |
| Anatomical terms of neuroanatomy | |
Aunipolar neuron is a neuron in which only one process, called aneurite, extends from thecell body. The neurite then branches to form dendritic and axonal processes. Most neurons in the central nervous systems ofinvertebrates, including insects, are unipolar.[2] The cell bodies of invertebrate unipolar neurons are often located around the edges of theneuropil, in the so-called cell-body rind.[3]
Most neurons in the central nervous systems ofvertebrates, including mammals, aremultipolar.[4] In multipolar neurons, multiple processes extend from the cell body including dendrites and axons. Some neurons in the vertebrate brain have a unipolar morphology: a notable example is theunipolar brush cell, found in thecerebellum and granule region of thedorsal cochlear nucleus.
A third morphological class,bipolar neurons, extend just one axon and dendritic process from the cell body. Examples of bipolar neurons include most invertebratesensory neurons andbipolar cells of the vertebrate retina.
Some vertebratesensory neurons are classified aspseudounipolar. Pseudounipolar neurons initially develop as bipolar cells, but at some point the two processes that extend from the cell body fuse to form a single neurite.[4] The pseudounipolar neuron's axon then splits into two branches. Sensory neurons with cell bodies in thedorsal root ganglia of thevertebrate spinal cord are pseudo-unipolar: one branch projects to the periphery (to sensory receptors in the skin, joints, and muscle), the other to the spinal cord.