Types Of Neurons: Structure And Functions

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 this article you will find more information about the neuron.

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.

Specifically, the parts of the neuron are the following:

• soma: It 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: They are small, branched extensions that come out of 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. On the one hand, in the central nervous system (CNS) the majority of 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.

On the other hand, neurons in the peripheral nervous system (PNS) have extensive axons to travel to muscles or sensory organs.

Neurons are the fundamental units of the nervous system and play a crucial role in information transmission in the form of electrical and chemical impulses between the brain and the body. The way neurons communicate with each other is called synapse

The synapse process occurs between the axon of one neuron and the dendrite of another, sending information through the release of molecules called neurotransmitters, or by 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.

Next, we present the main functions of neurons:

• Signal reception: The dendrites of neurons receive signals from other neurons or sensory cells in response to environmental or internal stimuli.
• Information integration: Neurons integrate information received from multiple sources. In the cell body, an integration process takes place to determine if the received signal is strong enough to generate a nerve impulse.
• Generation of nerve impulses: If the integrated information reaches a critical threshold, the neuron generates a nerve impulse (action potential) that travels along its axon.
• Conduction of nerve impulses: Nerve impulses travel along the axon of the neuron. This process is carried out through changes in the electrical potential across the cell membrane, which allows rapid and efficient transmission of the signal.
• Synaptic transmission: When the nerve impulse reaches the end of the axon (axon terminal), it triggers the release of neurotransmitters at the neuronal synapse. These neurotransmitters cross the synaptic gap and activate receptors on the next target neuron or cell.
• Interneuronal communication: Neurons communicate with each other through synapses, forming complex neural networks. This communication is essential for processing information, making decisions, and executing motor responses.
• Regulation of homeostasis: Neurons participate in the regulation of body functions, such as temperature, heart rate, blood pressure and other physiological activities, thus helping to maintain homeostasis of the body.
• Participation in memory and learning: Synaptic connections between neurons can strengthen or weaken over time, contributing to the formation of memories and the learning process.
• Control of motor functions: Motor neurons transmit signals from the central nervous system to the muscles and glands, thus allowing the control of movements and motor responses.

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. Although they can be classified in many ways, the most common would be by their function and shape:

• Because of its function: It 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: motoneurons, sensory neurons and interneurons.
• Because of its shape: we find unipolar neurons, bipolar neurons, pseudopolar neurons and multipolar neurons.

Next, we present the characteristics of the different types of neurons.

Motoneurons

Motoneurons are a specific type of neurons that play a fundamental role in the peripheral nervous system, particularly in the transmission of motor signals from the central nervous system to the skeletal muscles. These neurons are involved in the generation and control of voluntary muscle movements. There are two main categories of motoneurons:

• Upper motor neurons: These neurons are found in the primary motor cortex of the brain and are involved in the planning and control of voluntary motor movements. They transmit descending signals to the lower motor neurons to execute precise and coordinated movements.
• lower motor neurons: These neurons are located in the spinal cord and are responsible for transmitting motor signals from the spinal cord to the peripheral muscles. They control muscle contraction and are essential for the execution of conscious movements, such as walking, running or lifting objects.

Sensory neurons (afferents)

These neurons transmit information from sensory receptors, such as tactile receptors in the skin or visual receptors in the eyes, to the central nervous system 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

Also known as association neurons, interneurons facilitate communication between other neurons, creating extensive neurological networks for complex mental processes such as thinking. They participate in the integration of signals and the modulation of neuronal responses.

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, since they require a rapid response.

unipolar neurons

Unipolar neurons, also known as pseudounipolar neurons, are a specialized type of neurons that They have a single extension or axon which divides into two branches, one that goes towards the periphery and another that extends towards the central nervous system. They do not have dendrites in the soma.

Although structurally they are considered unipolar, functionally they act as bipolar neurons due to the connection of their branches with different regions of the nervous system.

bipolar neurons

Bipolar neurons are a type of neurons that have two extensions or cellular processes: an axon and a dendrite Unlike multipolar neurons, which have multiple dendrites, bipolar neurons have only one dendrite and one axon.

This type of neurons is commonly found in certain sensory systems and specializes in transmitting information between sensory cells and the central nervous system.

Pseudounipolar neurons

Pseudounipolar neurons are a specialized type of neurons that have a single main process that divides into two branches, functioning as a combination of a unipolar and a bipolar neuron. Despite their name, they are considered a type of bipolar neurons in functional terms. These neurons are common in the peripheral nervous system and They are located in the dorsal root ganglia of the spinal cord They are very involved in the sense of touch and pain.

multipolar neurons

Multipolar neurons are a type of neurons that have multiple processes or cellular processes that extend from the cell body. These neurons are the most common in the nervous system and perform diverse functions, including signal integration and transmission of nerve impulses in the central nervous system. They are the most abundant and 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, which have a conical shape and are 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. Secondly, 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: They are neurons with a short axon, to connect with nearby neurons or cells.

Multipolar neurons are essential for higher brain function, including cognition, memory, learning and voluntary motor control.

This article is merely informative, at PsychologyFor we do not have the power to make a diagnosis or recommend a treatment. We invite you to go to a psychologist to treat your particular case.

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