What Really Happens Inside a Neuron?

Introduction:

Neuron or also known as a nerve cell is a fundamental unit of our brain and nervous system. Neurons are cells that are responsible for receiving sensory input from the external environment. The neurons send motor commands to our muscles, they transform and relay electrical signals at each step of the reflex arc. It is estimated that about 100 billion neurons interact closely with other cell types which are classified as glia. Neurons come in various shapes and sizes depending on their specific purpose and location. Understanding neurons is really crucial as they are specialized in transmitting information throughout our body so we can communicate with each other, walk and process the information. Overall, their interactions do define who we are as people. In this article, you will understand the function of neurons, structure of neurons, how neurons communicate and the life of a neuron. 

Function of Neurons: Why are neurons the fundamental blocks of our Brain and Nervous system?

Our nervous system consists of sensory neurons, motor neurons and relay neurons. Each neuron has a specific function. They all work together to perform complex functions in the human body. For example, they allow us to sense, move and react to certain stimuli. The neurons are a crucial part of how we act and communicate.

Sensory neurons (afferent neurons)

Sensory neurons also known as afferent neurons carry information from the receptor cells to the brain for processing the information. Receptor cells are biological transducers that convert the energy from both external and internal environment into electrical impulses, they are located in the eyes, skin and ears. Sensory neurons help us to see, taste, hear and smell. Through them we can also feel pressure, temperature and touch. 

Motor neurons (efferent neurons)

Motor neurons also known as efferent neurons transmit information from the brain to the glands and muscles of the body to react. There are two types of motor neurons: upper motor neurons and lower motor neurons.  Upper motor neurons are in the primary motor cortex of the brain. They travel down the spinal cord. The lower motor neurons then carry the signal by extending from the spinal cord to the target glands and muscles. By activating motor neurons of the muscle fibers, you can perform various physical movements for example kicking a ball or chewing food.

Relay neurons (Interneurons) 

Relay neurons also known as interneurons are responsible for carrying information between sensory and motor neurons through the spinal cord and brain. Complex movements including walking and talking require coordination of lots of muscles. This mainly involves a sensory-motor feedback loop that allows fine-tuning of gestures. Relay neurons also play a crucial part in assisting with reflex actions that allow us for example to pull our hand off if we touch something hot. 

Inside the Neuron: Structure

A simple way to imagine the structure of neurons is by imagining a tree. A neuron has three major parts: dendrites, axon and a cell body also called soma. Soma can be represented as the branches, roots or a trunk of a tree. A dendrite is where a neuron receives input from other cells. Dendrites branch as they move towards their tips in a similar way tree branches do. They also have leaf-like structures on dendrites called spines.

The axon is the output structure of a neuron. For a neuron to transfer information to another neuron it sends an electrical message called an action potential. The electrical message is sent throughout the entire axon. The soma is where the nucleus is located, specifically where the neuron’s DNA is housed and where proteins are created to later be transferred through the axon and dendrites. 

Definitions:

Axon - The long and thin structure in which the action potentials are generated. The axon is the transmitting part of the neuron. After the initiation, action potentials go through axons to cause a release of neurotransmitters. 

Dendrite - The receiving information part of the neurone. Dendrite receives the synaptic inputs from axons. They receive them with the sum of the total of dendritic inputs and determining whether a neuron will fire an action potential.

Spine - The small neurone protrusions found on the dendrites that, for synapses, the postsynaptic contact site.

Action potential - The electrical event generated in the axon that signals the neurons as ‘active’. Action potential travels through the axon and causes the release of neurotransmitters into the synapse. The neuron communicates with other neurons because of the action potential and consequent transmitter release. 

Cell body (soma) - Where the signals from the dendrites are joined and passed on. The soma and the nucleus do not play a significant role in the transmission of the neural signal but instead they serve to maintain the cell and keep the function of the neuron. 

How do neurons communicate with each other?

For neurons to communicate with each other they transmit information both within the neuron and from one neuron to another. This process includes both electrical signals and chemical messengers.

Electrical Signals

Electrical communications occur when dendrites of a neuron receive a stimulus from an axon of a different neuron. This makes a change in the electrical charge of the cell membrane. This is called depolarization, which continues to the cell body. Once the signal has reached the beginning of the axon, known as axon hillock, if the impulse is strong enough, it will travel down the axon in the form of an electrical signal also called action potential. 

Chemical Messengers

When an electrical impulse has reached the end of an axon also known as axon terminal or nerve ending, the information will be transmitted across the synaptic gap which is the space between the axon terminal of one neuron and the dendrite of another neuron also called as adjoining neuron. The neuron which sends the signal is called the presynaptic neuron and the neuron receiving the signal is called the postsynaptic neuron.

Sometimes, synapses allow electrical communication by a simple flow of ions between two neurons. However, most of the time the synapses require chemical messengers also known as neurotransmitters to be released into the synaptic gap, to later be picked up by the receptors of another neuron. 

Three processes can take place to stop the communication between neurons. The first process is reuptake which is when the neurotransmitters are reabsorbed by the presynaptic neuron to be reused. The second process is degradation. It is when the neurotransmitters are broken down in the gap by enzymes.  

The third process is diffusion. Occurs when other neurotransmitters will simply diffuse away from the synaptic gap. 

Life of a neuron

The birth of a Neuron: Neurogenesis

Neurogenesis is the process by which new neurons are formed in the brain. Neurogenesis is particularly crucial when an embryo is developing. It also continues in certain brain regions after birth and throughout our lifespan.

Our brain has many specialized areas of functions, and neurons that are different in structure and connections. For example the hippocampus is a brain region that has a crucial role in memory and spatial navigation. It alone has at least 27 different types of neurons. This uniqueness and diversity of neurons in the brain is resulted from regulated neurogenesis during embryonic development. During this process, neural stem cells differentiate-when they become any one of a number of specialized cell types-at specific times and regions in the brain.

Death of a Neuron

Even though neurons are the longest living cells in the human body, large numbers of them die during migration and differentiation. The lives of neurons can take strange turns. There are diseases of the brain that result in unnatural deaths of neurons. For example:

• Huntington’s disease is a genetic mutation which causes neurons to create too many neurotransmitters called glutamate. Glutamate kills neurons in the basal ganglia. Consequently, people twist and move uncontrollably and over a time they lose the ability to do everyday tasks such as eating or walking.

• Alzheimer’s disease is when unusual proteins build up in and around neurons in the hippocampus and neocortex which are the regions of the brain that control memory. When these neurons die, the person loses their ability to remember and do everyday tasks.

• Parkinson’s disease is when neurons that produce the neurotransmitter dopamine die in the basal ganglia which is an area of the brain that controls body movement. This causes a person with this disease to experience tremor causing them to move more slowly and have problems with balance.

Conclusion

Neurons are considered one of the most crucial and interesting types of cells in the human body. From their complex structure to the way they transmit signals through electrical impulses and chemical messengers neurons are significant for every action that our body and brain carry out. Their life cycle from their early development and death shows how essential these cells are. By acknowledging and understanding neurons we gain an appreciation and recognition of the power and vulnerability of our human brain.

Bibliography

Britannica Editors. "neuron". Encyclopedia Britannica, 29 Mar. 2025, https://www.britannica.com/science/neuron. Accessed 20 November 2025. 

Kendra Cherry, MSEd. “Different Parts of a Neuron.” Verywell Mind, 5 Apr. 2023, www.verywellmind.com/structure-of-a-neuron-2794896. Accessed 20 Nov. 2025. 

Kendra Cherry, MSEd. “How Neurons Transmit Information Throughout the Body.” Verywell Mind, 27 Aug. 2025, www.verywellmind.com/what-is-a-neuron-2794890. Accessed 20 Nov. 2025. 

Lentz, Thomas L., Erulkar, Solomon D.. "nervous system". Encyclopedia Britannica, 9 Oct. 2025, https://www.britannica.com/science/nervous-system. Accessed 20 November 2025.

National Institutes of Health (NIH). “Brain Basics: The Life and Death of a Neuron.” National Institute of Neurological Disorders and Stroke, U.S. Department of Health and Human Services, www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-life-and-death-neuron. Accessed 20 Nov. 2025. 

Newman, Tim. “Neurons: What Are They and How Do They Work?” Medical News Today, MediLexicon International, 18 July 2023, www.medicalnewstoday.com/articles/320289#In-a-nutshell. Accessed 20 Nov. 2025. 

Woodruff, Dr Alan. “What Is a Neuron?” Queensland Brain Institute - University of Queensland, 3 Oct. 2023, qbi.uq.edu.au/brain/brain-anatomy/what-neuron. Accessed 20 Nov. 2025. 

Digital Images:

“Motor, Sensory and Interneuron.” Earth’s Lab, 30 Aug. 2018, www.earthslab.com/physiology/sensory-motor-functions-and-neurons/#content-sensory-system. Accessed 20 Nov. 2025. 

Reuters , Will Dunham. “Scientists Pinpointed Individual Neurones That Encoded Memories (iStockphoto: Wildpixel).” ABC (Australian Broadcasting Corporation), 2 July 2015, www.abc.net.au/science/articles/2015/07/02/4266219.htm?site=science/tricks. Accessed 20 Nov. 2025. 

Woodruff, Alan, and De Roo et al. “The Tree-like Structure of a Neuron.  A Segment of Dendrite from Which Spines Branch off, like Leaves off a Tree Branch. .” Queensland Brain Institute - University of Queensland, 3 Oct. 2023, qbi.uq.edu.au/brain/brain-anatomy/what-neuron. Accessed 20 Nov. 2025.