One of the most common classifications of neurons is that which is carried out according to their morphology; more particularly, they are generally divided according to the number of dendrites and axons present in their cell body.
In this article we will describe the characteristics of the main types of multipolar neurons, much more common than bipolar and pseudounipolar in the human central nervous system.
Characteristics of multipolar neurons
Multipolar neurons are mainly characterized by the presentation a single axon with several dendrites, Extensions the main function is the reception of synaptic impulses. This class of neurons specializes in integrating information from other nerve cells.
This type of neuron is the most numerous in the central nervous system; its amount is very high in the cerebral cortex, spinal cord and lymph nodes (Sets of cell bodies) of the autonomic nervous system. Technically, any neuron with an axon and at least two dendrites is considered a multipolar neuron.
Typically, multipolar neurons have an approximately ovoid shaped soma. From this cell body arise multiple dendrites which extend in all directions, forming tangled-looking branches. These dendritic trees give the neuron a larger area where it receives nerve stimuli.
The axons of this type of neuron are usually very long, which facilitates the transmission of impulses along the central nervous system. They are often covered with Schwann cells, a type of neuroglia that forms myelin sheaths in this part of the nervous system; this substance allows efficient and rapid neuronal transmission.
Multipolar neurons they can be divided into two subtypes: those of class A and those of class B. Those of type A have very branched dendritic trees and have many dendritic spines. In contrast, the two characteristics are much less marked in class B multipolar neurons, which also have a larger soma.
Multipolar neuron type
Below, we describe three of the most relevant and numerous types of multipolar neurons in the human body: Purkinje cells, pyramidal cells, and Dogiel cells. Each of them has its own peculiarities, locations and functions.
1. Purkinje cells
Purkinje cells are located in the cerebellum, at the back of the brain, which is responsible for coordinating and tracking movement. The appearance of these neurons is very characteristic due to the density of its dendritic treesThis explains the important role of the reception of the neural impulses they perform.
2. Pyramidal cells
The pyramidal cells or higher motor neurons originate from the motor cortex. This type of multipolar neuron transmits action potentials through the corticospinal tract to lower motor neurons in the spinal cord, which they allow movement by synchronizing with muscle cells.
In addition, pyramidal cells are fundamentally involved in cognition. This function is associated with connections between pyramidal neurons and the prefrontal cortex of the brain. He also speculated on its possible role in visual recognition of objects.
3. Dogiel cells
Dogiel cells are a type of multipolar neuron located in the prevertebral sympathetic ganglia. They are part of the enteric nervous system, which regulates the functioning of the gastrointestinal tract.
Other classes of neurons
Neurons can be classified according to different criteria. For example, if we divide them according to their function, we find sensory neurons, motors and interneurons or association neurons. There are also excitatory, inhibitory and modulatory neurons if we look at the type of synapses they make.
The term “multipolar” is boxed in the classification of neuron types according to their external morphology. More specifically, by dividing neurons by the number of extensions (i.e. dendrites and axons), we can distinguish multipolar, bipolar, pseudounipolar, unipolar, and anaxonic neurons.
The cytoplasm of bipolar neurons has two extensions; among them it acts as a dendrite, receiving impulses from other neurons, and the second acts as an axon, sending them out. They mainly act as sensory neurons and are located in the spinal ganglia, vestibulocochlear nerve, retina or olfactory epithelium.
In these neurons, the axon and dendrites originate from a single extension of the cell body. They do not exist in the human organism, although yes in that of other living beings.
Pseudounipolar neurons are a type of bipolar neuron whose axon splits into two during the formation of dendrites and axon, so that they seem unipolar, although they are not. Unlike true unipolar neurons, these are found in the human body.
A neuron is said to be anaxonic when it lacks an axon or when it cannot be distinguished from dendrites. Cells of this type mainly act as interneurons.
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