From savoring a delicious chocolate ice cream, to a turbulent tummy ache, to deciding to stop eating ice cream for a while, neurons have played a key role in this entire process. Neurons govern our senses and sensations, they are what allow us to think, decide, get excited and many other things that make up our mind and make us who we are. But what are neurons? What are their functions and what parts are they made of? If you want to know more about these small but important cells, keep reading this Psychology-Online article: Types of neurons: structure and functions. You will find all the information about the types of neurons there are, as well as their structure and multiple functions.
What is a neuron
The neurons are highly specialized cells which are part of our body’s nervous system, found especially in the brain. They are defined as “messenger cells” for their ability to receive and emit electrical and chemical signals, therefore its main function is the transmission of information to other cells in the body. They form neural networks together from synapses that carry out a large multitude of complex functions in the nervous system, from movement to get out of bed, processing the taste of lunch, to higher mental functions such as deciding what shirt we will wear today. In the following article you will find more information about .
Structure of the neuron and its parts
Due to the multiplicity of functions that they can perform, there is a diversity of types of neurons depending on their specialization. At the same time, this specialization is reflected in the structural variety that each of them presents. Nevertheless, all neurons share structural parts that define them as such.
Neuron: parts
The parts of the neuron are the following:
- Soma: is the body of the cell, where the nucleus and the different organelles reside. It can also be called perikaryon. The dendrites and axon arise from it.
- Dendrites: are small, branched extensions that emerge from the soma whose function is to receive information from other cells.
- Axon: is the extension of the neuron responsible for sending nerve impulses to other cells. Its length is variable, and can measure up to one meter. It is covered with myelin, a substance that protects the axon and increases the speed of impulse transmission.
Although all neurons share these structures, their size and morphology are subject to their function and location in the human body. In the (CNS) most neurons have a large number of branches, giving their bodies a star-shaped shape, some with a pyramidal shape depending on the brain area where they are located. While the neurons of the peripheral nervous system (PNS) have extensive axons to travel to muscles or sensory organs.
Neuron function
The human body performs an impressive number of tasks with different levels of complexity every moment and every day. Neurons are responsible for carry all kinds of information between the brain and the body to operate normally. Given the immense plurality of information that is transmitted, it is inevitable that neurons have ended up specializing and that they have emerged different types of neurons. Even so, the function of a fundamental neuron is the task of receiving and giving information.
The way neurons communicate with each other is called synapse. This occurs between the axon of one neuron and the dendrite of another, sending information from the release of molecules called or sodium ions in the space between the two neurons, called the intersynaptic space. These molecules will generate a response in the second neuron, either activating it to send more information or inhibiting its activity.
Types of neurons
Neurons are the cells of the nervous system that send and receive information. Due to the number of functions they perform, they have become specialized and we can find different types of neurons depending on the function they perform and their shape. Main types of neurons are the following:
- Motoneurons
- sensory neurons
- Interneurons
- unipolar neurons
- bipolar neurons
- Pseudounipolar neurons
- multipolar neurons
Neurons can be classified in many ways, the most common being by their function and shape. If we look the function of a neuron, is reduced to the communication of nervous impulses, but the origin, destination and purpose of these signals allows them to be classified into different groups: motor neurons, sensory neurons and interneurons. While if we want to classify them depending on its shape, we find unipolar neurons, bipolar neurons, pseudopolar neurons and multipolar neurons. The characteristics of each type of neurons are explained below.
Motoneurons
The motor neurons send nerve impulses to muscles from the CNS. Allowing voluntary muscle movement and coordination as well as being responsible for the smooth or visceral muscles, that is, those responsible for the heartbeat or intestinal movement.
sensory neurons
sensory neurons send information from all sensory organs to the CNS for processing. The five traditional perceptual senses (sight, hearing, touch, smell and taste) and the somatic senses (thermoreception, nocioception, proprioception and balanceception) are sent.
Interneurons
These types of neurons connect exclusively with other neurons, creating extensive neurological networks for complex mental processes such as thinking. Most of these neurons are found in the CNS, but they also exist beyond the brain. In the peripheral nervous system, the neurons responsible for reflex movements are interneurons, as they require a rapid response.
unipolar neurons
They are found mainly in invertebrates. They have a single extension that uses both axon and dendrite in their branches. They do not have dendrites in the soma.
bipolar neurons
They are mainly sensory neurons. They appear to have two opposing axons, but one of the extensions is the dendrite, prepared to receive a lot of sensory information.
Pseudounipolar neurons
At first glance they appear unipolar because they have only one axon. If you look closely you can see that the extension actually has two ends, one receiving information and the other sending it, as if it were a tube. They are very involved in the sense of touch and pain.
multipolar neurons
They are the most abundant. They have dendrites in the soma and an axon. They can be separated into two groups depending on the length of the axon:
- Golgi type I: These neurons have long axons, in order to establish connections with distant cells. Two types of multipolar neurons would also come into play here. First of all, the pyramidal neurons: As the name indicates, it has a conical shape and is found in different parts of the cerebral cortex as well as in the hippocampus and amygdala. They are one of the largest neurons in our body. In second the Purkinje neurons: Its name comes from the scientist who discovered them, Jan Evangelista Purkinje. They are found in the cerebellum and their main structural characteristic is the extensive branching of the dendrites of these neurons, making their shape look like a tree.
- Golgi II type: these are neurons with a short axon, to connect with nearby neurons or cells.
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Bibliography
- Haykin, S. (1994). Neural networks: a comprehensive foundation. Prentice Hall PTR.
- Solms, M., Turnbull, O., Sacks, O., & Jaramillo, D. (2004). The brain and the inner world: an introduction to the neuroscience of subjective experience. Fund of Economic Culture