Updated: Mar 3, 2022
Do you know what controls your brain? Yep, neurons do. But how exactly do neurons work?
What Is a Neuron?
The human brain consists of billions of nerve cells called neurons. The primary duty of a neuron is to connect with one another, establishing paths that control all your body functions like memories, emotions, and movement. In every neuron, there is a cell body, dendrites, and an axon. In this blog post, we will mainly examine the cell body.
The cell body (also known as the soma) is a bulbous structure that contains the nucleus and is considered the metabolic site of the cell. As is shown in the figure, dendrites are linked through the cell body to the neuron and the axon, which transmit information within and towards other cells. More specifically, dendrites will signal the cell body when other neurons receive the information. Based on the strength of that signal, the cell body may pass the information onto the axon.
The cell body contains all the components a regular cell would contain. Special, tiny organelles each carry out particular tasks:
Similar to other kinds of secretory cells, cell bodies in neurons are composed of the same cytoplasmic parts (a gel-like microtrabecular lattice).
Many neurofilaments in the cell body are narrow strands of protein that form a supportive cytoskeleton, maintaining the shape and strength of the cell body.
It is critical to learn about the large nucleus and nucleolus in the structure. The nucleus stores DNA, serving as a blueprint that regulates cellular processes; the nucleolus inside the nucleus produces ribosomes that are necessary for protein production.
The endoplasmic reticulum and the Golgi apparatus collaborate to aid the packaging and sorting of proteins. In particular, the endoplasmic reticulum transports eukaryotic cells and synthesizes protein. The folded membranes are made up of two parts - rough endoplasmic reticulum, and smooth endoplasmic reticulum.
Furthermore, free ribosomes surround the nucleus and are also attached to the surface of rough endoplasmic reticulum (REP). REP are “rough” because of the ribosomes studded on the outside of the structure. Since ribosomes and REP are dyed easily by basic materials, they are also called chromatophilic substances or Nissl bodies, according to Get Body Smart.
The following image illustrates another component: mitochondria. They are known as “powerhouses” of the cell because they generate all the energy needed to transfer messages amongst neurons. Looking at a smaller scale, the pipe-like microtubules at the bottom of the graph are responsible to convey supplies all the way to the axon.
Lysosomes are membrane-bound organelles that contain digestive enzymes, which break down worn-out cell parts
Pathway for Proteins
As building blocks of cells, proteins ensure neurons construct new axons and dendrites, make chemicals, and join other neurons together. So it is intriguing to explore the output of proteins in more detail. In general, they are synthesized by the REP and ribosomes. According to Neuron Cell Body - Structure and Functions, 2020:
In the beginning, proteins created by ribosomes are located in transport vesicles, then enter the cytoplasm and travel to the Golgi apparatus. As is mentioned in the previous section, the proteins are chemically processed, categorized, and packaged for metabolic activity within the Golgi body.
After that, proteins flow into secretory vesicles from the Golgi complex. The long linkages of microtubules send the secretory vesicles down the axon to synaptic knobs that act as or yield neurotransmitters. Similarly, the REP also makes proteins that are further spread for neurotransmission.
The energy for all the functions is provided by adenosine triphosphate (ATP) in mitochondria.
Cell Bodies in Cell Types
For different types of cells, the placement of cell bodies is different.
In bipolar neurons, the cell body is located in the center with one axon and one dendrite attached at each end. Most of them are specialized for transmitting sensory information, including smell, taste, touch, etc. They are usually located within the skin, joints, and muscles
For unipolar neurons, there is a projection linking the axon and the dendrite rather than both coming directly to the cell body. As sensory cells, their role is majorly in the central nervous system (brain and spinal cord).
The cell bodies of multipolar neurons are connected to a long axon and many dendrites, allowing them to transmit a considerable amount of information. They are the most common type of neuron and can be found in the central nervous system as well. The Purkinje cell in the cerebellum is an excellent example.
A pseudounipolar neuron has a single structure that extends from the soma, but then branches into two different connections. This is similar to a cross between bipolar and unipolar neurons. Most sensory neurons are pseudounipolar.
Apart from the nucleus and the production of proteins, another vital part in the cell body, the axon, extends to many smaller branches before reaching nerve terminals. Similarly, dendrites also stretch outward to interact with other neurons at contact points called synapses. Therefore, the dendrites are covered with synapses formed by the ends of axons from other cells. Interested in these topics? More information can be found in the rest of our curriculum!
As the control center of neurons, the cell body or soma is made up of cytoplasm that contains common organs, such as the nucleus, nucleolus, rough endoplasmic reticulum, Golgi apparatus, mitochondria, ribosomes, microtubules, cytoskeleton, etc. ATP, in the mitochondria specifically, supplies all the energy used in metabolism and the maintenance of the structures and fundamental functions. Additionally, the cell body signifies and exchanges information among numerous neurons by the axon, while undertaking a variety of complex biochemical processes. Most importantly, the cell body can express unique genetic characteristics through DNA in the nucleus, as well as synthesize crucial proteins.
Boundless. (2020). Neurons. Biology LibreTexts. https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)/35%3A_The_Nervous_System/35.1%3A_Neurons_and_Glial_Cells/35.1B%3A_Neurons
Get Body Smart. (2022). Neuron Cell Body – Structure and Functions. Get Body Smart. https://www.getbodysmart.com/nerve-cells/neuron-cell-body
Robb, A., & Airth, M. (2022). What Is a Cell Body? - Definition, Function & Types. Study.com. https://study.com/academy/lesson/what-is-a-cell-body-definition-function-types.html
Waymire, J. C. (2022). Chapter 8: Organization of Cell Types. Neuroscience Online. https://nba.uth.tmc.edu/neuroscience/m/s1/chapter08.html