Pseudounipolar neuron

Structure

A pseudounipolar neuron has one axon that projects from the cell body for relatively a very short distance, before splitting into two branches. Pseudounipolar neurons are sensory neurons that have no dendrites, the branched axon serving both functions. The peripheral branch extends from the cell body to organs in the periphery including skin, joints and muscles, and the central branch extends from the cell body to the spinal cord.

In the dorsal root ganglia

The cell body of a pseudounipolar neuron is located within a dorsal root ganglion. The axon leaves the cell body (and out of the dorsal root ganglion) into the dorsal root, where it splits into two branches. The central branch goes to the dorsal columns of the spinal cord, where it forms synapses with other neurons. The peripheral branch travels through the distal dorsal root into the spinal nerve all the way until skin, joint, and muscle.

In most sensory ganglia of cranial nerves

Pseudounipolar neurons are found in the sensory ganglia of most cranial nerves.

Specifically the:

• trigeminal ganglion
• geniculate ganglion
• superior ganglion of the glossopharyngeal nerve
• inferior ganglion of the glossopharyngeal nerve
• superior ganglion of the vagus nerve
• inferior ganglion of the vagus nerve

Pseudounipolar neurons in cranial nerve sensory ganglia synapse in the main sensory trigeminal nucleus, spinal trigeminal nucleus or solitary nucleus.

While the vestibulocochlear nerve has two ganglia associated with it (spiral ganglion and vestibular ganglion), both contain bipolar neurons, not pseudounipolar.

In the mesencephalic nucleus

The mesencephalic nucleus is made up of pseudounipolar neurons which migrated into the brainstem during embryological development. It is the only location in the central nervous system where the cell bodies of pseudounipolar neurons are found.