Unipolar, multipolar, and bipolar neurons are all types of nerve cells that are responsible for transferring information throughout animal bodies. Neurons use electrical impulses and chemical signals to transmit information between the central nervous system (CNS) and the rest of the body.
There are different types of neurons, and scientists distinguish each type by its number of components and its structure.
Multipolar neurons can transfer the most information between cells, and they are the most common form of neuron in the human nervous system.
This article takes a closer look at unipolar, bipolar, and multipolar neurons.
What is a neuron?
A neuron is a nerve cell that passes information around the body throughTrusted Source electrical impulses and chemical signals. The cell structure enablesTrusted Source neurons to pass on information, as they have long extensions from the cell body for transmitting and receiving information.
The components of the neuron work together to facilitate nerve function. The three mainTrusted Source parts of a neuron are:
Cell body, or soma: The cell body has a nucleus that contains the cell’s genetic material and controls the cell’s activities.
Axon: This part, which looks like a long tail, transmits signals from the cell.
Dendrite: This part, which looks like the branches of a tree, receives signals for the cell.
Neurons send information to each other by transmitting chemical signals called neurotransmitters across special junctions called synapses. These synapses are present at the tips of dendrites.
There are several types of neurons with different structures. Some neurons contain multiple dendrites, while others have none. The types include:
unipolar neurons
pseudounipolar neurons
bipolar neurons
multipolar neurons
anaxonic neurons
What are unipolar neurons?
A unipolar neuron only has one nerve process extending from the cell body: an axon that extends into dendrites.
Unipolar neurons only occurTrusted Source in invertebrates, such as flies, and are not present in humans. In invertebrates, unipolar neurons play a role in the glands and muscles.
Although the human body does not contain unipolar neurons, pseudounipolar neurons are present. A pseudounipolar neuron is a cell that only occurs as a sensory neuron.
In a pseudounipolar neuron, the nerve process extending from the cell body splits into two branches or axons. As a result, the neuron has two separate axons that independently divide into dendrites at the ends. This form is similar to that of a bipolar neuron.
What are bipolar neurons?
A bipolar neuron has two distinct structures extending from the cell body. One is an axon, and the other is a dendrite.
Bipolar neurons are uncommon and only occur in a few specific areas within the body. These include:
the olfactory epithelium, which is nerve tissue that runs along the nasal cavity and plays a role in smell
the retina, a thin layer of tissue at the back of the eye that receives light signals
certain nerves within the ear
What are multipolar neurons?
Multipolar neurons are the most common type of neurons in the human body. They are present throughout a person’s CNS, including the brain and associated nerves in the autonomic nervous system.
A multipolar neuron has the highest number of structures extending from the cell body. There is only one axon, but each cell has many dendrites, making it easier for the neuron to exchange information.
Similarities
Unipolar, bipolar, and multipolar neurons have some similar characteristics. They all featureTrusted Source long structures extending from the cell body. Additionally, they all have the main components of the cell body, axon, and dendrite.
Despite occurring in different areas within the body, the neurons play a similar role, as they are responsible for passing information between the brain and the CNS.
Differences
The number and structure of components differTrusted Source among unipolar, bipolar, and multipolar neurons. For example, the dendrites only occur at the tips of the axon in unipolar neurons, but multiple dendrites stem from the cell body of a multipolar neuron.
The structure of bipolar neurons is similar to that of pseudounipolar neurons in that two distinct structures stem from the cell body. However, instead of starting as one extension that splits into two, the structures grow independently out of the cell body. The structure of a multipolar neuron is different again, as more than two structures extend from the cell body.
The table below summarizes the differences between unipolar, bipolar, and multipolar neurons.
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