The key difference between unipolar and pseudounipolar neuron is that unipolar neuron has only one protoplasmic process while pseudounipolar neuron has an axon that splits into two branches.
A neuron or a nerve cell is the basic structural unit of our nervous system. It is an electrically excitable cell. Neurons receive signals from the external world via sensory organs and send them to the central nervous system in order to process. They also transmit signals from the brain and spinal cord to other parts of the body, especially to muscles and gland cells. In this way, neurons facilitate communication within our body. A neuron has three major components: an axon, dendrites and a cell body. A neuron receives signals from dendrites and they go via cell body to the axon. From the axon, signal goes to the next neuron through the synapse. Neurons can be unipolar, pseudounipolar, bipolar or multipolar. Most neurons are multipolar or bipolar. However, there are unipolar and pseudounipolar neurons as well.
CONTENTS
1. Overview and Key Difference
2. What is a Unipolar Neuron
3. What is a Pseudounipolar Neuron
4. Similarities Between Unipolar and Pseudounipolar Neuron
5. Side by Side Comparison – Unipolar vs Pseudounipolar Neuron in Tabular Form
6. Summary
What is a Unipolar Neuron?
A unipolar neuron is a neuron that possesses only one protoplasmic process. In other words, it has only one neurite. Therefore, these unipolar neurons have only one structure extending from the cell body or soma.
Generally, unipolar neurons are present only in invertebrates, especially in insects in order to stimulate muscles or glands. Vertebrates including humans do not possess unipolar neurons.
What is a Pseudounipolar Neuron?
A pseudounipolar neuron is one of the four types of neurons. In fact, it is a true unipolar neuron which has only one protoplasmic process extending from the cell body. But, this process or axon splits into two branches or distinct structures. One branch runs into the periphery while the other runs into the spinal cord.
Figure 01: Four Types of Neurons
Pseudounipolar neurons are present in both vertebrates and invertebrates. Most sensory neurons are pseudounipolar neurons. Thus, this type of neuron is exclusive to sensory neurons.
What are the Similarities Between Unipolar and Pseudounipolar Neuron?
- Unipolar and pseudounipolar neurons are two of the four types of neurons.
- Both are true unipolar neurons which have only one process coming out from the soma.
- Invertebrates have both unipolar and pseudounipolar neurons.
What is the Difference Between Unipolar and Pseudounipolar Neuron?
A unipolar neuron has one protoplasmic process while a pseudounipolar neuron has one protoplasmic process or an axon that branches into two distinct structures. Therefore, this is the key difference between unipolar and pseudounipolar neuron. Furthermore, only invertebrates have unipolar neurons while both invertebrates and vertebrates have pseudounipolar neurons.
Summary – Unipolar vs Pseudounipolar Neuron
Neurons are four types as unipolar, pseudounipolar, bipolar and multipolar. Both unipolar and psedounipolar neurons have only one process coming out from the cell body. But, in a pseudounipolar neuron, the axon splits into two branches unlike in unipolar neuron. Thus, this is the key difference between unipolar and pseudounipolar neuron.
Reference:
1. “Boundless Biology.” Lumen, Available here.
2. “Types of Neurons.” Queensland Brain Institute, 26 Mar. 2018, Available here.
Image Courtesy:
1. “Figure 35 01 04” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia