A Look Into the Major Neurotransmitters of the Nervous System

Major Neurotransmitters

Acetylcholine.

During the early stages of neuroanatomy exploration, scientists were not sure how neurons transmitted their information. Was it all electrical conduction or did chemicals play a role?

Acetylcholine was the first neurotransmitter to be discovered, and proved the validity of the chemical nature of synapses.

Acetylcholine works both in the Central Nervous System (CNS) and in the Peripheral Nervous System (PNS).

In the PNS, it is famous for being the neurotransmitter used at the neuron muscular junctions, and for being an excitatory (in most cases) neurotransmitter.

Acetylcholine is the name of a neurotransmitter, but the neurons that release acetylcholine are called cholinergic neurons.

There are two types of receptors that are sensitive to acetylcholine: Nicotinic (ionotropic) receptors, and Muscarinic (metabotropic) receptors.

Glutamate

neurotransmission
Neurotransmission. Image Credit: Nrets

Glutamate is an amino acid that also serves as a neurotransmitter. It is the major excitatory neurotransmiter in the CNS.
There are two major receptors sensitive to glutamate: NMDA receptors (ionotropic) and AMPA (metabotropic) receptors.

The amount of both NMDA and AMPA receptors affect the sensitivity of the cell, and are thought to be directly related to synaptic plasticity and therefore to learning and memory.

NMDA receptors are quite unusual in that they let calcium ions enter the cell. This becomes dangerous when they become overly excited and too much calcium enters the neuron and ends up killing the cell.

ATP

ATP (like glutamate) can also serve as an excitatory neurotransmitter. There are both inotropic (P2X) receptors and metabotropic (P2Y) receptors to ATP.

Serotonin

Serotonin is also called 5-hydroxytryptamine (5-HT) and is derived from the amino acid tryptophan.

Serotonin neurons are almost exclusively found in the raphe nucleus, but those neurons have an extremely large range of branches, and are thus involved in many cognitive functions (mood, appetite, sleep, learning and memory).

Except for one ionotropic receptor, most serotonin receptors are metabotropic receptors.

Norepinephrine

Norepinephrine and Noradrenaline refer to the exact same neurotransmitter. I find the term noradrenaline to be more descriptive, and is used in most countries.

Neurons that produce noradrenaline are called noradrenergic (but not “norepinephric”… another reason why I prefer noradrenaline).

Receptors to noradrenaline are also called noradrenergic receptors.

Norepinephrine is derived from the amino acid tyrosine.

In the brain, noradrenergic neurons are mostly found in the locus ceruleus and in the reticular formation. These neurons also have a very large range of branches and influence many cognitive functions (arousal, decision making, reward, depression, schizophrenia,….).

Dopamine

Just like Norepinephrine, dopamine is also derived from tyrosine.

Dopamine is produced by dopaminergic neurons. Most dopaminergic neurons are found in the substantia nigra pars compacta, in the ventral tegmental area, in the hypothalamus, and even in the retina.

The reach of dopamine neurons is very extended as well and play a role in reward-learning, schizophrenia, memory, attention, problem-solving, and personality traits.

GABA

GABA, (or γ-Aminobutyric acid ) is a derivative of glutamate, but is a major inhibitory neurotransmiter.

There are both ionotropic and metabotropic  receptors to GABA. (GABA receptors and GABA producing neurons are called “GABAergic”).

 

If you want more articles and videos about the Nervous System, you can find them here. More resources are available to help make Biology fun. I invite you to absorb all the content you can find here at Interactive-Biology.com.



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  • What are ionotropic and metabotropic receptors?

    Out of topic:
    I visited your website about premeds and liked it.I’m going to take my MCAT tests in september.
    I subscribed and found out your 3x3x3 technique and from then on I’m starting to apply this technique.I just have a question do I have to revise after 3rd day of revision too.And do you have anymore tips od how to get things in long term memory?
    Thankyou

  • Sorry for again disturbing you,I just noticed that some neurotransmitters are derived from amino acids(the building blocks of proteins)so what is the chemical nature of these neurotransmitters?Are they protein in nature?

  • Hi Pluto,

    The first step for both ionotropic and metabotropic receptors is that the ligand (in this case the neurotransmitter) binds to the receptor.

    The difference starts here:
    1. Ionotropic receptors: As soon as the neurotransmitter binds the receptor, the receptor “opens up” to let ions flow into the postsynaptic neuron. This ion flow ends up creating the new “electrical message.”

    2. Metabotropic receptors: These are more complicated and involve more steps and additional components. Basically, as soon as the neurotransmitter binds to the receptor, the receptor “tells” another molecule what’s happening, and that molecule will go and “tell” other molecules to act in a different way.

    If you want more details, I’ll write an article about inotropic and metabotropic receptors in my next article! (next monday)

    Thank you for your question! 🙂

    Study technique:
    Yes, you will still have to review the material before the exam. But all the preparation that you’ve done should help you cut down your “cramming” time before the exam.

  • Hi again Pluto,

    Proteins are long chains of amino acids linked up to each other.

    However, some amino acids are “non-standard” amino acids and they are not found in proteins. The neurotransmitter GABA (gamma-aminobutyric acid) is one of them.

    This website is for teaching, so ask as many questions as you want!

  • Oh Thank you for your answers ^_^.
    You are so kind.
    This website is really the best.
    I really want details on how sympathetic and parasympathetic system works.
    The only thing I know is their basic functions.

    Can you do a detailed article on the nerve impulse,the action potential etc.
    This site has videos but I want the good explanation of graph of the depolariztion and repolarization.
    I have a textbook that explains well but still there are a few points blurry to me especially the role of Calcium.

    Thank you in advance.

  • Sorry, but I think, that NMDA and AMPA are both ionotropic. At least that is what they say in all the Neuroscience books.

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