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Neurons: Who are they and what do they do? 

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Neurons: Who are they and what do they do? 

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- National Institute of Neurological Disorders and Stroke (Apr. 2022)

Brain Basics: The Life and Death of a Neuron Retrieved from: https://www.ninds.nih.gov/health-information/patient-caregiver-education/brain-basics-life-and-death-neuron#:~:text=Neurons%20are%20information%20messengers.,rest%20of%20the%20nervous%20system.

- Neuro Transmissions (Sept. 20, 2015) What is a Neuron? [Video] https://www.youtube.com/watch?v=UDpydfpEads

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Request free mailed brochure
Until recently, most neuroscientists thought we were born with all the neurons we were ever going to have. As children we might produce some new neurons to help build the pathways - called neural circuits - that act as information highways between different areas of the brain. But scientists believed that once a neural circuit was in place, adding any new neurons would disrupt the flow of information and disable the brain's communication system.

In 1962, scientist Joseph Altman challenged this belief when he saw evidence of neurogenesis (the birth of neurons) in a region of the adult rat brain called the hippocampus. He later reported that newborn neurons migrated from their birthplace in the hippocampus to other parts of the brain. In 1979, another scientist, Michael Kaplan, confirmed Altman's findings in the rat brain, and in 1983 he found neural precursor cells in the forebrain of an adult monkey.

These discoveries about neurogenesis in the adult brain were surprising to other researchers who didn't think they could be true in humans. But in the early 1980s, a scientist trying to understand how birds learn to sing suggested that neuroscientists look again at neurogenesis in the adult brain and begin to see how it might make sense. In a series of experiments, Fernando Nottebohm and his research team showed that the numbers of neurons in the forebrains of male canaries dramatically increased during the mating season. This was the same time in which the birds had to learn new songs to attract females.

Why did these bird brains add neurons at such a critical time in learning? Nottebohm believed it was because fresh neurons helped store new song patterns within the neural circuits of the forebrain, the area of the brain that controls complex behaviors. These new neurons made learning possible. If birds made new neurons to help them remember and learn, Nottebohm thought the brains of mammals might too.

Other scientists believed these findings could not apply to mammals, but Elizabeth Gould later found evidence of newborn neurons in a distinct area of the brain in monkeys, and Fred Gage and Peter Eriksson showed that the adult human brain produced new neurons in a similar area.

For some neuroscientists, neurogenesis in the adult brain is still an unproven theory. But others think the evidence offers intriguing possibilities about the role of adult-generated neurons in learning and memory.

The central nervous system (which includes the brain and spinal cord) is made up of two basic types of cells: neurons (1) and glia (4) & (6). Glia outnumber neurons in some parts of the brain, but neurons are the key players in the brain.

Neurons are information messengers. They use electrical impulses and chemical signals to transmit information between different areas of the brain, and between the brain and the rest of the nervous system. Everything we think and feel and do would be impossible without the work of neurons and their support cells, the glial cells called astrocytes (4) and oligodendrocytes (6).

Neurons have three basic parts: a cell body and two extensions called an axon (5) and a dendrite (3). Within the cell body is a nucleus (2), which controls the cell's activities and contains the cell's genetic material. The axon looks like a long tail and transmits messages from the cell. Dendrites look like the branches of a tree and receive messages for the cell. Neurons communicate with each other by sending chemicals, called neurotransmitters, across a tiny space, called a synapse, between the axons and dendrites of adjacent neurons.

There are three classes of neurons:

1. Sensory neurons carry information from the sense organs (such as the eyes and ears) to the brain.

2. Motor neurons control voluntary muscle activity such as speaking and carry messages from nerve cells in the brain to the muscles.

3. All the other neurons are called interneurons.

Scientists think that neurons are the most diverse kind of cell in the body. Within these three classes of neurons are hundreds of different types, each with specific message-carrying abilities.

How these neurons communicate with each other by making connections is what makes each of us unique in how we think, and feel, and act.

The extent to which new neurons are generated in the brain is a controversial subject among neuroscientists. Although the majority of neurons are already present in our brains by the time we are born, there is evidence to support that neurogenesis (the scientific word for the birth of neurons) is a lifelong process.

Neurons are born in areas of the brain that are rich in concentrations of neural precursor cells (also called neural stem cells). These cells have the potential to generate most, if not all, of the different types of neurons and glia found in the brain.

Neuroscientists have observed how neural precursor cells behave in the laboratory. Although this may not be exactly how these cells behave when they are in the brain, it gives us information about how they could be behaving when they are in the brain's environment.

The science of stem cells is still very new, and could change with additional discoveries, but researchers have learned enough to be able to describe how neural stem cells generate the other cells of the brain. They call it a stem cell's lineage and it is similar in principle to a family tree.

Neural stem cells increase by dividing in two and producing either two new stem cells, or two early progenitor cells, or one of each.

When a stem cell divides to produce another stem cell, it is said to self-renew. This new cell has the potential to make more stem cells.

When a stem cell divides to produce an early progenitor cell, it is said to differentiate. Differentiation means that the new cell is more specialized in form and function. An early progenitor cell does not have the potential of a stem cell to make many different types of cells. It can only make cells in its particular lineage.

Early progenitor cells can self-renew or go in either of two ways. One type will give rise to astrocytes. The other type will ultimately produce neurons or oligodendrocytes.

Once a neuron is born it has to travel to the place in the brain where it will do its work.

How does a neuron know where to go? What helps it get there?

Scientists have seen that neurons use at least two different methods to travel:

1. Some neurons migrate by following the long fibers of cells called radial glia. These fibers extend from the inner layers to the outer layers of the brain. Neurons glide along the fibers until they reach their destination.

2. Neurons also travel by using chemical signals. Scientists have found special molecules on the surface of neurons -- adhesion molecules -- that bind with similar molecules on nearby glial cells or nerve axons. These chemical signals guide the neuron to its final location.

Not all neurons are successful in their journey. Scientists think that only a third reach their destination. Some cells die during the process of neuronal development.

Some neurons survive the trip, but end up where they shouldn't be. Mutations in the genes that control migration create areas of misplaced or oddly formed neurons that can cause disorders such as childhood epilepsy. Some researchers suspect that schizophrenia and the learning disorder dyslexia are partly the result of misguided neurons.

Once a neuron reaches its destination, it has to settle in to work. This final step of differentiation is the least well-understood part of neurogenesis.

Neurons are responsible for the transport and uptake of neurotransmitters - chemicals that relay information between brain cells.

Depending on its location, a neuron can perform the job of a sensory neuron, a motor neuron, or an interneuron, sending and receiving specific neurotransmitters.

In the developing brain, a neuron depends on molecular signals from other cells, such as astrocytes, to determine its shape and location, the kind of transmitter it produces, and to which other neurons it will connect. These freshly born cells establish neural circuits - or information pathways connecting neuron to neuron - that will be in place throughout adulthood.

But in the adult brain, neural circuits are already developed and neurons must find a way to fit in. As a new neuron settles in, it starts to look like surrounding cells. It develops an axon and dendrites and begins to communicate with its neighbors.

Although neurons are the longest living cells in the body, large numbers of them die during migration and differentiation.

The lives of some neurons can take abnormal turns. Some diseases of the brain are the result of the unnatural deaths of neurons.

- In Parkinson's disease, neurons that produce the neurotransmitter dopamine die off in the basal ganglia, an area of the brain that controls body movements. This causes difficulty initiating movement.

- In Huntington's disease, a genetic mutation causes over-production of a neurotransmitter called glutamate, which kills neurons in the basal ganglia. As a result, people twist and writhe uncontrollably.

- In Alzheimer's disease, unusual proteins build up in and around neurons in the neocortex and hippocampus, parts of the brain that control memory. When these neurons die, people lose their capacity to remember and their ability to do everyday tasks. Physical damage to the brain and other parts of the central nervous system can also kill or disable neurons.

- Blows to the brain, or the damage caused by a stroke, can kill neurons outright or slowly starve them of the oxygen and nutrients they need to survive.

- Spinal cord injury can disrupt communication between the brain and muscles when neurons lose their connection to axons located below the site of injury. These neurons may still live, but they lose their ability to communicate.

Scientists hope that by understanding more about the life and death of neurons they can develop new treatments, and possibly even cures, for brain diseases and disorders that affect the lives of millions of Americans.

The most current research suggests that neural stem cells can generate many, if not all, of the different types of neurons found in the brain and the nervous system. Learning how to manipulate these stem cells in the laboratory into specific types of neurons could produce a fresh supply of brain cells to replace those that have died or been damaged.

Therapies could also be created to take advantage of growth factors and other signaling mechanisms inside the brain that tell precursor cells to make new neurons. This would make it possible to repair, reshape, and renew the brain from within.

For information on other neurological disorders or research programs funded by the National Institute of Neurological Disorders and Stroke, contact the Institute's Brain Resources and Information Network () at:

Prepared by:
Office of Communications and Public Liaison
National Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, MD 20892

health-related material is provided for information purposes only and does not necessarily represent endorsement by or an official position of the National Institute of Neurological Disorders and Stroke or any other Federal agency. Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient's medical history.

All NINDS-prepared information is in the public domain and may be freely copied. Credit to the or the is appreciated.

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Brain Basics: The Life and Death of a Neuron

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Request free mailed brochure Until recently, most neuroscientists thought we were born with all the neurons we were ever going to have. As children we might produce some new neurons to help build the pathways - called neural circuits - that act as information highways between different areas of the brain.

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Neurons are information messengers. They use electrical impulses and chemical signals to transmit information between different areas of the brain, and between the brain and the rest of the nervous system.

In a nutshell, the body and mind communicate through neurons.

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The neuron. It is perhaps the most important cell in the human body. We have billions in our body and together they form a superhighway that sends information throughout our mind and body. But can you name the different parts? Alie Astrocyte explains a little more about the neuron and gives a concise overview of its anatomy.

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The basic functions of neurons are:

Receive signals (or information).

Integrate the received signals (to determine if the information should or should not be transmitted).

Remember:
A group of neurons forms a nerve.

Communicate signals to target cells (muscles, glands or other neurons).

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While they have the common features of a typical cell, they are structurally and functionally unique from other cells in many ways. All neurons have three main parts: 1) dendrites, 2) cell body or soma, and 3) axons. Besides the three major parts, there is the presence of axon terminal and synapse at the end of the neuron.

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Sciencefacts.Net (2020) Parts of a Neuron and Their Function Retrieved from: https://www.sciencefacts.net/parts-of-a-neuron.html

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Parts of a Neuron and Their Functions with Labelled Diagram

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Find out what are the 3 different parts of a neuron and which part does what. Also learn about other important structures instrumental to neuron’s function

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Bipolar neurons are relatively rare. They are sensory neurons found in olfactory epithelium, the retina of the eye, and ganglia of the vestibulocochlear nerve.

Unipolar neurons are sensory neurons with cell bodies located in spinal and cranial nerve ganglia.

Multipolar neurons are the most common type of neuron. They are located in the central nervous system (brain and spinal cord) and in autonomic ganglia. Multipolar neurons have more than two processes emanating from the neuron cell body.

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Sensory Neurons
Sensory neurons (sometimes referred to as afferent neurons) are nerve cells which carry nerve impulses from sensory receptors towards the central nervous system and brain. When these nerve impulses reach the brain, they are translated into ‘sensations’, such as vision, hearing, taste and touch.

Motor Neurons
Motor neurons (also referred to as efferent neurons) are the nerve cells responsible for carrying signals away from the central nervous system towards muscles to cause movement. They release neurotransmitters to trigger responses leading to muscle movement.

Relay Neurons
A relay neuron (also known as an interneuron) allows sensory and motor neurons to communicate with each other. Relay neurons connect various neurons within the brain and spinal cord, and are easy to recognize, due to their short axons.

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All for One and One for All: Types of Neurons by Structure

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All for One and One for All: Types of Neurons by Structure

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Fletcher, Baitz (2004) Nervous Tissue Histology Retreived from: http://vanat.cvm.umn.edu/neurLab1/index.html

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Neurohistology Lab Objectives:
A. Identify neurons, astrocytes, oligodendrocytes, and ependymal cells in the CNS.
B. In the PNS, identify axons, myelin, and lemmocytes associated with nerves and ganglia.
C. In the CNS, distinquish white matter (concentrations of myelinated axons) from
gray matter (concentrations of neuronal cell bodies).
D. Be able to identify dura mater, arachnoid, and pia mater; also, subarachnoid space.
E. Be able to define the following terms:

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Neurohistology Lab Objectives: A. Identify neurons, astrocytes, oligodendrocytes, and ependymal cells in the CNS. B. In the PNS, identify axons, myelin, and lemmocytes associated with nerves and ganglia. C. In the CNS, distinquish white matter (concentrations of myelinated axons) from gray matter (concentrations of neuronal cell bodies). D.

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All for One and One for All: Types of Neurons by Function 

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All for One and One for All: Types of Neurons by Function 

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Guy-Evans, O. (2021, Feb 15). What is a neuron? Function, parts, structure, and types. Simply Psychology. www.simplypsychology.org/neuron.html

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(Retrieved from: https://www.youtube.com/watch?)v=fdhzNYJH7eA)

In a nutshell...

A synapse is the small gap between two neurons, where nerve impulses are relayed by a neurotransmitter from the axon of a presynaptic (sending) neuron to the dendrite of a postsynaptic (receiving) neuron. It is referred to as the synaptic cleft or synaptic gap.

During synaptic transmission, the action potential (an electrical impulse) triggers the synaptic vesicles of the pre-synaptic neuron to release neurotransmitters (a chemical message).

These neurotransmitters diffuse across the synaptic cleft (the gap between the pre and post-synaptic neurons) and bind to specialized receptor sites on the post-synaptic neuron.

If the neurotransmitter is excitatory (eg. noradrenaline) then the post-synaptic neuron is more likely to fire an impulse. If the neurotransmitter is inhibitory (eg. serotonin) then the post-synaptic neuron is less likely to fire an impulse.

The excitatory and inhibitory influences are summed to determine whether/how frequently the neuron will fire (summation). At the dendrites, the chemical message is converted back into an electrical impulse and the process of transmission occurs again.

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Oh synapse! Time to connect the dots...I mean neurons. Each neuron is separated from its neighbors, so how exactly does a message get passed from one neuron to the next? Through the synapse, of course! Take a closer look at the basic structure of the synapse, the two synapse types (electrical vs.

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A neurotransmitter is a chemical messenger that carries, boosts, and balances signals between neurons (also known as nerve cells) and target cells throughout the body. These target cells may be in glands, muscles, or other neurons.

How do they work?
In most cases, a neurotransmitter is released from what's known as the axon terminal after an action potential has reached the synapse, a place where neurons can transmit signals to each other.

When an electrical signal reaches the end of a neuron, it triggers the release of small sacs called vesicles that contain the neurotransmitters. These sacs spill their contents into the synapse, where the neurotransmitters then move across the gap toward the neighboring cells. These cells contain receptors where the neurotransmitters can bind and trigger changes in the cells.

After release, the neurotransmitter crosses the synaptic gap and attaches to the receptor site on the other neuron, either exciting or inhibiting the receiving neuron depending on what the neurotransmitter is.

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Connecting the Dots: Neurotransmitters and Synapses

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Connecting the Dots: Neurotransmitters and Synapses

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Guy Evans (Feb. 2021) What happens at The Synapse? How Neurons Communicate With Each Other. Retrieved from: https://www.simplypsychology.org/synapse.html

Cherry (Jul. 2021) The Role of Neurotransmitters. Retreived from: https://www.verywellmind.com/what-is-a-neurotransmitter-2795394

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How Neurons Communicate With Each Other

By Olivia Guy-Evans, published Feb 21, 2021

Fact checked by Saul Mcleod, PhD

Key Points

A synapse is the small gap between two neurons, where nerve impulses are relayed by a neurotransmitter from the axon of a presynaptic (sending) neuron to the dendrite of a postsynaptic (receiving) neuron. It is referred to as the synaptic cleft or synaptic gap.

During synaptic transmission, the action potential (an electrical impulse) triggers the synaptic vesicles of the pre-synaptic neuron to release neurotransmitters (a chemical message).

These neurotransmitters diffuse across the synaptic cleft (the gap between the pre and post-synaptic neurons) and bind to specialized receptor sites on the post-synaptic neuron.

If the neurotransmitter is excitatory (eg. noradrenaline) then the post-synaptic neuron is more likely to fire an impulse. If the neurotransmitter is inhibitory (eg. serotonin) then the post-synaptic neuron is less likely to fire an impulse.

The excitatory and inhibitory influences are summed to determine whether/how frequently the neuron will fire (summation). At the dendrites, the chemical message is converted back into an electrical impulse and the process of transmission occurs again.

What is a Synapse?

Neurons do not touch each other, but where the neuron does come close to another neuron, a synapse is formed between the two.

Neurons essentially communicate with each other through synapses. When signals have traveled through neurons to the endpoint, they cannot simply continue onto the next neuron.

It must trigger the release of neurotransmitters which then carry the signals across the synapse in order to reach the next neuron. Terminal buttons belong to the presynaptic endings of the neuron and have vessels containing neurotransmitters. These are responsible for transmitting signals to other neurons.

When a nerve impulse has triggered the release of these neurotransmitters from the terminal buttons, these chemicals are then released into the synaptic cleft and are then taken up by receptors on the next cell.

The neuron that then receives the neurotransmitters is the postsynaptic neuron. Neurons receive messages from many terminal buttons and in turn, terminal buttons form synapses with many other neurons.

A synapse is a combination of:

Presynaptic endings - which contain the neurotransmitters (chemical messengers).

Synaptic clefts - which is the gap between the two neurons.

Postsynaptic endings - which contains the sites for receptors (molecules which receives signals for a cell).

Synapses also have the ability to communicate a change in the message being passed on. Postsynaptic neurons can also send communications back to the presynaptic neurons telling them to change how often or much a neurotransmitter is released. Due to this, we can say that the synapses are able to communicate bi-directionally.

Electrical or Chemical Synaptic Transmission?

Synapses can be either chemical or electrical and are essential to the functioning of neural activity. Neuroscientists understand that synapses play a vital role in a variety of cognitive functions, including learning and memory formation.

Chemical Synapses

Electrical Synapses

Gap between cells is about 20 nanometres

Gap between cells is about 3.5 nanometres

Speed of transmission is several milliseconds

Speed of transmission is nearly instantaneous

Can be excitatory or inhibitory

Excitatory only

No loss of signal strength

Signal strength diminishes over time

Chemical Synapses Transmission

The most commonly found synapses in humans are chemical synapses. This occurs due to electrical activity in the presynaptic neurons triggering the release of neurotransmitters.

The neurotransmitters disperse across the synaptic cleft to then bind themselves to specialized receptors of postsynaptic neurons. Once this occurs, the neurotransmitters then either excites or inhibits the postsynaptic neuron. Exciting the postsynaptic neuron leads to a firing of action potential (electrical impulses), whereas inhibiting the postsynaptic neuron prevents the transmission of a signal.

Inside the presynaptic neuron are synaptic vesicles, which are covered in membrane and contain neurotransmitters. When an action potential arrives at the presynaptic terminal, it activates voltage-gated calcium channels (Ca² +) in the neuron's membrane. Ca² + are highly concentrated on the outside of the neuron and will rush into the neuron when activated.

The Ca² + permits the synaptic vesicles to fuse with the presynaptic terminal's membrane, enabling it to release neurotransmitters into the synaptic cleft.

The transmitter molecules then will diffuse across the synaptic cleft and will bind to the receptors of the postsynaptic neuron. When these receptors are activated, this leads to either the opening or closing of ion channels, which are membrane proteins that provide a passageway through which charged ions can cross.

Depending on the ions involved, this may either be depolarising- making the inside of the cell more positive, or hyperpolarisation - which makes the inside of the cell more negative (less likely for an action potential to be generated in the postsynaptic neuron).

Electrical Synapses Transmission

Electrical synapses are different from chemical synapses as there is a direct physical connection between the presynaptic and the postsynaptic neuron. This connection takes the form of something called a gap junction, which is essentially a channel which allows ions to flow directly from the presynaptic cell to the postsynaptic cell.

Gap junctions contain paired channels in the membranes of the pre and postsynaptic neurons, forming pores. These pores are larger than those of the voltage-gated ion channels in chemical synapses, meaning that a variety of substances can diffuse between the neurons.

Electrical synapses transmit signals much quicker than chemical synapses, almost instantaneously, compared with chemical synapses taking several milliseconds.

Despite being a lot faster to transmit signals, electrical synapses' signal strength is diminished over time, whereas chemical synapses do not lose their signal strength. Also, whilst chemical synapses can be excitatory or inhibitory, electrical synapses can only be excitatory.

Excitatory and Inhibitory Postsynaptic Potentials

The effect of the presynaptic neuron on the postsynaptic neuron can be either excitatory or inhibitory.

Neurotransmitters are chemical messengers that are released from a synaptic vesicle into the synapse by neurons.

Inhibitory neurotransmitters decrease the likelihood of the neuron firing. They are generally responsible for calming the mind and inducing sleep. This is the case for serotonin.

Excitatory neurotransmitters increase the likelihood that an excitatory signal is sent to the post-synaptic cell. Adrenalin is which is both a neurotransmitter and a hormone has an excitatory effect.

Chemicals released from the presynaptic neuron may either excite or inhibit the postsynaptic neuron, telling it to release neurotransmitters or to slow down or stop signaling.

When the axon fires and the terminal buttons release a neurotransmitter that excites the postsynaptic neuron, this is excitatory postsynaptic potential (EPSP). This effect of excitation makes it more likely that the axons of the postsynaptic neuron will also fire.

The inhibitory postsynaptic potential (IPSP) has the opposite effect. Inhibition is caused by inhibitory neurotransmitters. When the neurotransmitter binds with the post-synaptic receptor, it results in a IPSP and the cell is less likely to fire.

The rate at which the axon fires is determined by the activity of the synapses on the dendrites and soma of the neuron. If the excitatory synapses are more active then the axons fire at a high rate, compared to firing at a low rate, or not at all when inhibitory synapses are active.

An EPSP is depolarising, meaning it makes the inside of the neuron more positive, which causes more action potential. IPSPs however, bring the potential down, meaning it will be less likely to cause action potential and can cancel out the excitatory effect of the EPSPs.

Spatial and Temporal Summation

Summation is the process that determines whether/how frequently the neuron will fire by the combined effects of excitatory and inhibitory signals, both from multiple simultaneous inputs (spatial summation), and from repeated inputs (temporal summation).

EPSPs and IPSPs interact with each other when a postsynaptic neuron combines (or summates) all the excitatory and inhibitory signals it receives and then makes a decision as to whether to fire an action potential. There are two types of summation that can occur at this stage:

Spatial summation - this happens when all the postsynaptic potentials occur in different locations but at about the same time.

Temporal summation - this happens when all the postsynaptic potentials occur in the same place but at slightly different times.

For example, if there are two single excitatory signals (EPSPs) that arrive at the postsynaptic neuron from two different dendrites, they cannot reach the threshold for action potential on their own. However, they can sum up together to reach the threshold and cause an action potential of the postsynaptic neuron.

If an inhibitory signal (IPSP) also enters through another dendrite, this can counteract the two EPSPs and could prevent the neuron from firing action potential. This is an instance of spatial summation.

If the same two EPSPs arrive from the presynaptic neuron to the postsynaptic neuron, but at slightly different times, they can still cause an action potential to fire. This is because postsynaptic potentials are not instantaneous, and they can survive in a neuron for a while before dissipating.

Therefore, if one EPSP arrives first and has not dissipated yet, when the second EPSP arrives, they can then reach the threshold for action potential. This is an instance of temporal summation.

Reuptake of Neurotransmitters

For a synapse to function effectively, they must be shut off once the signal is sent. This signal termination allows the postsynaptic neuron to return to its resting potential state, ready for new signals. When neurotransmitters get released into the synaptic cleft, not all of them are able to attach to the receptors of the next neuron.

The synaptic cleft must be cleared of all neurotransmitters at signal termination, which can be done by either being broken down by enzymes, diffused away, or re-uptake occurs.

Re-uptake is when neurotransmitters get reabsorbed back into the presynaptic neuron from which they came from. Transporter proteins from the presynaptic membrane remove the neurotransmitters from the synaptic cleft, carrying the neurotransmitter back into the presynaptic neuron. The neurotransmitter then either gets re-packaged into the synaptic vesicles and stored until it is next needed again, or they are broken down by enzymes.

Serotonin is a type of neurotransmitter which is associated with a variety of psychological and bodily functions such as mood, sexual desire, appetite, sleep and memory. If there are imbalances in the way serotonin is transmitted between neurons, through too much reuptake of this neurotransmitter, then this has implications for contributing to mood disorders, specifically depression.

Selective serotonin reuptake inhibitors (SSRIs) are a type of medication, also known as antidepressants, which work in a way to increase the amount of serotonin being transmitted between cells. SSRIs essentially aid in blocking the reuptake of serotonin into the presynaptic cell, meaning there is more serotonin in the synaptic cleft.

If there is more serotonin in the synaptic cleft, it is more likely that serotonin will reach the receptors of the postsynaptic cell. As SSRIs allow more serotonin to pass along between neurons, they have been shown to alleviate mood disorders, making them a common therapy for depression.

Synaptic Plasticity

Plasticity refers to how much something can be changed or adapted through growth and reorganization. It was once believed that once synapses were formed, they remain the same forever, never changing.

However, it is now understood that activity, or lack of activity, can affect the strength of synapses, or even change the number and structure of synapses in the brain. Therefore, the more the synapses are used, the stronger they can become and the more influence they can have over postsynaptic neurons.

Likewise, not fully using synapses can weaken them and can have a detrimental impact over the long-term.

About the Author

Olivia Guy-Evans obtained her undergraduate degree in Educational Psychology at Edge Hill University in 2015. She then received her master's degree in Psychology of Education from the University of Bristol in 2019. Olivia has been working as a support worker for adults with learning disabilities in Bristol for the last four years.

How to reference this article:

Guy-Evans, O. (2021, Feb 21). Synapse definition and function. Simply Psychology. www.simplypsychology.org/synapse.html

Snapse (Kahn Academy) What is a Neuron Nicholls, J. G., Martin, A. R., Wallace, B. G., & Fuchs, P. A. (2001). From neuron to brain (Vol. 271). Sunderland, MA: Sinauer Associates. Pereda, A. E. (2014). Electrical synapses and their functional interactions with chemical synapses. Nature Reviews Neuroscience, 15(4), 250-263.

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Synapse Definition and Function - Simply Psychology

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By Olivia Guy-Evans, published Feb 21, 2021 Fact checked by Saul Mcleod, PhD Key Points A synapse is the small gap between two neurons, where nerve impulses are relayed by a neurotransmitter from the axon of a presynaptic (sending) neuron to the dendrite of a postsynaptic (receiving) neuron.

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When it comes down to neurons and their role in the Nervous System, the most relevant aspect to consider is the transmission of information that occurs in the synapses, as this is the site where information on the mind-body connection is communicated. This aspect of neuron activity is vital for our existence and survival.