A unipolar neuron is a type of neuron

Neuron

A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...

 in which only one protoplasmic process (neurite

Neurite

A neurite refers to any projection from the cell body of a neuron. This projection can be either an axon or a dendrite. The term is frequently used when speaking of immature or developing neurons, especially of cells in culture, because it can be difficult to tell axons from dendrites before...

) extends from the cell body. Most neurons are multipolar

Multipolar neuron

A multipolar neuron is a type of nig that possesses a single axon and many dendrites, allowing for the integration of a great deal of information from other neurons. These dendritic branches can also emerge from the nerve cell body...

, generating several dendrite

Dendrite

Dendrites are the branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project...

s and an axon

Axon

An axon is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma....

. Unipolar neurons that begin as bipolar neurons

Bipolar cell

As a part of the retina, the bipolar cell exists between photoreceptors and ganglion cells. They act, directly or indirectly, to transmit signals from the photoreceptors to the ganglion cells.-Overview:...

 during development are known as pseudounipolar neurons.

Unipolar neurons are common in insects, where the cell body is often located at the periphery of the brain and is electrically inactive. These cell bodies often send a single neurite into the brain; however, this neurite may ramify into a large number of branches making a very complex set of connections with other neurites, in regions of neuropil

Neuropil

In neuroanatomy, a neuropil, which is sometimes referred to as a neuropile, is a region between neuronal cell bodies in the gray matter of the brain and blood-brain barrier . It consists of a dense tangle of axon terminals, dendrites and glial cell processes...

.

In all species, including vertebrates and invertebrates, many types of primary sensory neurons are unipolar. Typically these have special structures for transducing some type of physical stimulus (light, sound, temperature, etc) into electrical activity, no dendrites, and a single axon that conveys the resulting signals into the spinal cord or brain.

See also

• Pseudounipolar neuron
• Bipolar neuron