These nerve cells can be classified according to different criteria.
Because although we normally refer to these nerve cells as if they were a single class of easily recognizable biological unit, the truth is that neurons can take many forms and adapt to very different functions.
In this article we will see what the main types of neurons are, what characterizes them, for what functions they have been adapted and what characteristics allow us to distinguish them from the rest.
- Recommended article: “The 10 most important types of neurotransmitters (and their functions)”
How are neurons classified?
The brain, in all its complexity, is composed primarily of two classes of nerve cells: glial cells and neurons. And, although glial cells are by far the most numerous cells in the human nervous system, it is the neurons that have received the most attention.
This is so due to a very simple fact: their activity varies in real time, corresponding to changes in thoughts, emotions and decision-making that define the psychological state of people, transmitting information between them at great speed. In other words: mental processes seem to develop, mainly, in the way in which neurons interact with each other, both in perception and in the emission of actions.
However, as there are so many tasks to perform in the nervous system, these nerve cells specialize in different functions, adopting a wide range of morphological and functional characteristics that allow them to be classified and distinguished from one another. In other words, there are many types of neurons, since they must adapt to very different tasks and environments.
In addition, something that complicates things is that there is not a single classification of the types of neurons, but several, because there are different criteria when it comes to finding differences between them. These criteria that help us get an idea of its variety are:
- The types of neurons according to the most abundant neurotransmitter with which they work.
- The types of neurons according to their morphological characteristics.
- The types of neurons according to the type of synapses they establish.
- The types of neurons according to their function.
In any case, beyond the differences that we can find between one class of neuron and the rest, there are characteristics common to all these nerve cells. Virtually all of them have these components of cellular anatomy, or are capable of developing them:
- The soma or cell body, the part that contains the nucleus with the DNA .
- Dendrites, small branches that capture neurotransmitters.
- The axon, an “arm” that extends until making contact with another target cell.
The 16 major neuron types
In the human brain alone there are already some 80 billion neurons (in the case of an adult) , so it would be rare for all these nerve cells to have exactly the same characteristics.
The truth is that they are very diversified to be able to occupy different functions, and although this complicates any attempt to investigate them, it gives us an idea of how complex the human nervous system is.
Let’s see a summary of the most important types of neurons, and the way in which their characteristics allow them to function well in coordination with the rest of the microscopic elements of the organism.
1. Types of neurons according to their neurotransmitter
As we have seen, neurons can be classified depending on the type of neurotransmitter they work with , capturing it and/or emitting it so that other neurons capture it.
The most relevant types of neurons according to this criterion are the following.
1.1. dopaminergic neurons
As it is easy to deduce from their name, these neurons work mainly from dopamine , one of the most important excitatory neurotransmitters in the nervous system.
1.2. noradrenergic neurons
Norepinephrine is the most important neurotransmitter to explain the functioning of this type of neurons.
It is a catecholamine that, in addition to being transmitted through the synaptic spaces between a sending and receiving neuron, also acts as a hormone that flows through the blood.
1.3. oxytocinergic neurons
Oxytocin is linked to prosocial behavior, the establishment of attachment bonds and sexuality. These neurons capture it and emit it.
1.4. GABAergic neurons
GABA is the most important inhibitory neurotransmitter, and these neurons circulate it.
1.5. serotonergic neurons
Another neurotransmitter that generates a depressant effect on the nervous system is serotonin , on which the functioning of these neurons is based.
1.6. cholinergic neurons
This type of neuron carries out its work from acetylcholine, a neurotransmitter involved in the storage of memories in the brain and in the activation of muscles, as well as in the automatic processes carried out by the autonomic nervous system.
1.7. vasopressin neurons
Vasopressin, a very important substance for the functioning of these nerve cells, has many functions related to body homeostasis, and is, in addition to a neurotransmitter, a hormone.
2. Types of neurons according to their morphology
If we look at the structure of neurons, these are the most important types of neurons:
2.1. unipolar neurons
These neurons only have a single “sleeve” that acts both by carrying information to the soma and by sending nerve signals to other neurons.
2.2. bipolar neurons
These are neurons that have a clear differentiation between dendrite and axon, since they capture signals on one side and send nerve impulses on the other.
23. multipolar neurons
This type of neuron is very similar to the previous one, but it has many dendrites (and only one axon).
3. Types of neurons according to their function
All neurons can be classified depending on the role they play in the perception-action cycle, that is, the circular dynamics that is established between the perception of a stimulus, the processing of that stimulus, the emission of an action influenced by the stimulus, and the perception of the novelties that have taken place around us after we interacted with it.
Based on this criterion, the types of neurons are as follows.
3.1. sensory neurons
These are the neurons that transmit information from the senses to the sensory integration areas of the brain.
3.2. motor neurons
As their name suggests, these nerve cells are responsible for transmitting movement orders to organs of the human body with motor capacity, mainly muscles.
3.3. Interneuronas
This type of neurons acts as a bridge between the previous two.
4. Types of neurons according to the type of synapse
If we look at the type of synapses that neurons establish , we will see these types.
4.1. excitatory neurons
They are the ones that act by generating a reaction on the part of the nerve cell that receives their signals.
4.2. inhibitory neurons
These types of neurons reduce the probability that the cell to which they send signals will react by activating.
4.3. modulatory neurons
The function of this type of neuron is to regulate the type of reaction that another neuron must have when it receives a certain neurotransmitter.
Bibliographic references
- D’Amicis, F., Hofer, P., & Rockenhaus, F. (2011) The Automatic Brain.
- Guillery RW (June 2005). Observations of synaptic structures: origins of the neuron doctrine and its current status. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 360 (1458): pp. 1281 – 307.
- Gurney, K. (1997). An Introduction to Neural Networks. London: Routledge.
- Kole, Maarten HP; Stuart, Greg J (2012). Signal processing in the axon initial segment. Neuron. 73(2): pp. 235 – 247.
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.