Soma Neurons

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Practical Psychology

It is in a neuron's soma, or cell body, where most of the neuron's metabolism occurs. A neuron's axon is its biggest and most cytoplasm-rich component. The soma is the hub from which dendrites and axons radiate. But what exactly is a soma neuron, and what does it do?

The soma neuron, also known as the cell body, is the most important part of a neuron. The soma’s function is to keep the neuron alive and firing properly. A membrane shields the soma from harm while allowing it to communicate with its immediate environment.

If you want to find out what a soma neuron is and does, this article explains everything you need to know. This includes the soma neuron's function and structure, major parts, characteristics, features, cell body definition, and more.

What Are Soma Neurons?

The nucleus of a neuron is housed in the bulbous soma, also known as the perikaryon. As the Greek term for "body," soma is commonly used to refer to the cell body of a neuron. Many distinct specialized neuron types exist, with soma sizes ranging from a few micrometers to well over a millimeter in the biggest invertebrate neurons.

The soma contains the cell nucleus. Most RNA in neurons is produced in the nucleus, and most body proteins are made from messenger RNAs that stay close to the nucleus. This makes it difficult to transport newly synthesized proteins to the axon terminal, which might be located many centimeters from the cell body.

The transmission of protein-containing particles from the soma to the axon terminals is facilitated by microtubule-associated motor proteins found in axons. The nucleus can support essential neuronal processes throughout the cell by facilitating the movement of molecules out from the soma.

Each sensory neuron's survival depends on its axon terminals establishing touch with apoptosis-blocking survival factors. These chemicals, like nerve growth factors, are essential for survival (NGF).

When nerve growth factor (NGF) binds to its receptor at the axon's tip, it triggers the production of a signal which must travel to the nucleus. One leading hypothesis proposes that NGF sensors are endocytosed from the axon terminal surface and that these endocytosis vesicles are carried up the axon to provide survival signals to the soma.

Functions & Structure

Several of the tiniest neurons in invertebrates are approximately 5 micrometers (μm), while the biggest neurons may be over 10 mm in length.

Nissl granules, also known as chromatophilic material, a material that stains darkly with basic dyes, and is made mostly of ER (rough endoplasmic reticulum ) and free polyribosomes, are found in the soma, which is the main portion of the neuron where the dendrites branch out.

Free ribosomes and the endoplasmic reticulum (ER) are two of the most active machines in the body since they are responsible for protein synthesis and membrane synthesis, respectively. In addition to a well-developed nuclear envelope, the Golgi apparatus is present.

Microtubules and neurofibrils network throughout the soma, and mitochondria are found throughout the cell in various locations. One of the most important parts of the soma is the cell nucleus. The majority of neurons' RNA comes from the nucleus. Most proteins are made from messenger RNAs (mRNAs) that stay close to the cell nucleus.

This complicates the delivery of fresh proteins to axon terminals that might be located a meter or more from the cell's core. Protein-filled vesicles are shuttled from the axon's soma to its synapses by microtubule-associated motor proteins. Molecules moving to and from the soma help keep the cell functioning normally.

The neuronal cell body has a specific region called the axon hillock from which the axon extends. Nissl granules (ribosomes wrapped with RER) and polyribosomes abound in this area, indicating a high rate of protein synthesis. The axon hillock is where materials are prepared for transport to the axon or returned to the soma.

These materials include the axon's cytoskeleton components, mitochondria, and other organelles. Since the axon hillock is often the location of action potential initiation, it also features a specific plasma membrane containing several voltage-gated ion channels.

Some sensory neurons only make it through their day because their axon terminals make touch with survival factor providers that keep them from being apoptotic. Neurotrophic factors, such as substances like nerve growth factor, play a crucial role in cell survival.

When nerve growth factor (NGF) binds to receptors in axon terminals, a signal is generated and must send that to the nucleus. One accepted hypothesis proposes that NGF receptors are retractable from the surface of axon terminals, and such endocytosis vesicles are carried up the axon to provide survival signals to the soma.

Most neuron cell bodies in vertebrates are encased in the body's central nervous system, which is shielded by the skull and spinal column. Nuclei refer to somatic cell clusters in the central nervous system (CNS), whereas ganglia describe similar structures along the nerves of the peripheral nervous system (PNS).

The Major Parts Of A Soma Neuron

A neuron's nucleus, cytoplasm, and cytosolic organelles are all found in its central section, known variously as the soma, perikaryon, or cell body. The four major parts of a neuron are the soma, dendrites, axon, and presynaptic terminals. The axon and dendrites are extensions of the neuronal body.

Different-sized and shaped cell bodies, or soma, exist. Comparatively, a neuron in the dorsal root ganglion has a spherical body. In contrast, those in the central nervous system have polygonal ones with concave surfaces that divide the many cell processes.


The neuron's dendrites and axon extend out from the soma, also known as the perikaryon. The cell nucleus is the most prominent component of the soma, which also houses several other organelles and granules known as Nissl granules.

Dendrites and axons have many of the same organelles as the soma, but axons lack the nucleus, Nissl bodies, and Golgi apparatus present in the soma and the dendrites.


The axon is one of two forms of protoplasmic projections from neuron cell bodies. The axon is a long, thin projection that extends from the neuron's cell body and is responsible for conducting electric impulses away from the soma.

Its length can be tens, hundreds, or even thousands of times that of the soma's diameter. Axons carry messages from neurons to muscles and glands. In some sensory neurons (pseudounipolar neurons), the electrical impulse goes along the axon from the periphery to the cell body.

It then travels along another branch of that identical axon from the cell body to the spinal column; these neurons are responsible for transmitting touch and temperature. One axon is all that every neuron can ever have. The axon has evolved to conduct only action potentials, a specific electric impulse.


Dendrites are the thin, branching extensions of neurons that receive information from other neurons, dendrites, and sensory cells. The cell body receives this data in electrical impulses and processes it accordingly.

Characteristics Of A Soma Neuron

Gray matter in the central nervous system or ganglia contains vertebrate creatures' soma or nerve cell body. Nerve fibers, which are extensions of neurons, compose the nervous system's white matter. The neuronal bodies, or "bodies," can vary in size and form depending on the kind of neuron. In this way, physical forms are characterized:

  • crashed
  • round
  • pyramidal
  • spindle-shaped

Neurons form synapses with one another and other cells, tissues, and organs. The term "synapse" refers to the break in anatomical continuity created by these connections.

Connections between neurons are established when one neuron's axon makes contact with the body, dendrites, and, in certain situations, another neuron's axon; for this reason, we refer to these bonds as axosomatic, axoaxonic, or axodendritic.

The soma processes the incoming impulses and sends a response via the axon, which might be directed at a neighboring neuron, a gland, or a muscle, depending on the kind of neuron.

Soma Neuron Features

A soma neutron’s features include;

Cytoplasmic Inclusions

Dihydroxyphenylalanine, often known as methyldopa, is the precursor to melatonin. Certain neurons take on a dark hue due to these cytoplasmic inclusions; this is notably true of neurons in the substantia nigra, and the nucleus coeruleus.

It's also present, albeit at lower levels, in the peripheral nervous system's sympathetic ganglia, the limbic system, dorsal motor nuclei of the vagus and the spinal cord. While their precise role remains unclear, these cytoplasmic inclusions are thought to be a byproduct of the manufacture of the neurotransmitter’s norepinephrine and dopamine, which share a common precursor.

A yellow pigment called lipofuscin accumulates in the cytoplasm of neurons in the brains of aged people. It accumulates with age and has been shown to disrupt cellular processes. Rarely seen lipid droplets in the cytoplasm of neurons may result from a metabolic malfunction or act as a source of stored energy.


Calcium regulation is a function of the smooth endoplasmic reticulum. RER, Golgi complex and polyribosomes all have roles in producing cytoplasmic and structural proteins, respectively.

Protein folding, glycosylation, the insertion of functional groups, etc., are all examples of posttranscriptional alterations that take place in the cisternae. The membrane's integral lipids are also produced. Lysosomes are very diverse organelles, housing in the neighborhood of forty distinct acid hydrolases.

Macromolecules, phagocytosed bacteria, cellular residues, and senescent organelles can all be broken down with the aid of these enzymes.

Adenosine triphosphate (ATP), a high-energy molecule used by the cell, is produced in the mitochondria through oxidative phosphorylation. It's where oxygen from the atmosphere is burned off during cellular respiration.


The neurofibril proteins serve both structural and transport roles, facilitating the movement of chemicals from the soma neuron to the axonal terminal, and back again. That's right; it's the neuron's internal syringe system.

From what has been said so far, it is clear that the soma or cell body, like any cell, is a complex interconnected structure of organelles, membranes, proteins, and several other types of molecules, the primary purpose of which is to transmit and receive nerve impulses in vertebrates.


Chromatin, the cell's hereditary material, is housed in the nucleus, DNA, and deoxyribonucleic acid. The nucleolus houses RNA production and is surrounded by the nucleoplasm, which contains macromolecules and nuclear particles essential for neuron survival.

The nucleus contains all the instructions required to produce all the chemicals that the neuron must produce to operate and maintain itself, including the instructions for producing all the structural and functional proteins that the neuron requires.

Cell Body Definition

Neurons, the principal cells of the nervous system, function electrochemically and are characterized by their specialized cellular structure. Neurons are crucial in allowing animals to share information across their whole bodies.

Neurons allow for alterations in behavior and physiology to keep an organism's internal and external environments in equilibrium. Without these cells, complex multicellular animals couldn't exist. Neurons contain various specialized parts that work together to perform their specific function. Included among the many important components of neurons are:

  • The somatic (or eukaryotic) cell body is where organelles are housed and where incoming signals are processed.
  • Dendrites pick up information.
  • Action potentials are sent through the axon and transformed at the terminal into a chemical signal for transmission to neighboring cells.

We may distinguish three major classes of neurons in the human body.

  • Intuitive neurons pick up on subtle shifts in their surroundings.
  • Our activities are governed by specialized nerve cells called motor neurons.
  • Interneurons are the cells that process information between sensory and motor neurons.

In concert, these three classes of neurons regulate human behavior. For example, while touching a flame, or ice cube, sensory neurons register the heat and the cold, interneurons inside the brain interpret the info, and motor neurons urge us to move our hand away. Amazing!

This applies to a wide variety of behaviors, including mental processes. When our blood pressure drops too low, our bodies sensory neurons pick up on the shift.

Smooth muscle in the vasculature is told to contract when interneurons process this data in the brain, which leads to a rise in blood pressure. We can respond appropriately to both internal and exterior changes because of the coordinated efforts of these three types of neurons.


Now we know that the cell body regulates the expression of genes, ensures the proper development of neurons, and manages the capacity to carry out certain tasks.

The soma of a neuron is quite large since it contains the cell's nucleus and other organelles. We also know that in the brain, soma neurons act as both transmitters and receivers of information; we would be zombies without them!

Reference this article:

Practical Psychology. (2022, September). Soma Neurons. Retrieved from

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