Major Neurotransmitters Of The Nervous System

I love this topic and I have spoken about it a lot lately, check out my last posts if you have missed any. Today I'm putting a little summary to get things clear.

As you might know, the nervous system is composed of a huge network of cells called neurons and each one of them connects with different others through either dendrite or axon.The junction between these cells is called synapse and there all the magic happen.To send a signal to other neurons a cell must release chemicals called neurotransmitters in the synapse, they bind to a receptor in the opposing neuron and it can be either an inhibitory or an excitatory signal.Each neurotransmitter has its own receptors and the same receptors can be occupied by more than one neurotransmitter.Neurotransmitters are important, they dictate how we feel, act and react.So everything we do relies on neurons communicating with one another.. and they are the main target of many drugs.There are many neurotransmitters, the most important are.

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GABA

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Gamma-Aminobutyric acid or short known as GABA is the main inhibitory neurotransmitter in the mammalian central nervous system including humans.it's synthesized in the brain from glutamate and active form of vitamin B6 as a cofactor.

GABA acts by binding to GABA(a) or GABA(b) receptors to cause an opening of ion channels and allowing a flow of either negatively charged chloride ions into the cell or positively charged potassium ions out of the cell which causes a hyperpolarization of the cell.

Because of its inhibitory effect, GABA prevents neurons from over-reacting.In fact, patients who suffer from epilepsy, a disease caused by neurons over-firing have decreased GABA levels.Also, GABA plays a role in motor control and muscle tone, it's used to treat the trembling found in patients with Huntington’s disease.

Low levels of GABA may lead to insomnia due to the over-excitation, depression, mood swing and excessive stress.It can go as far as anger management issues, gambling or even worse such as bipolar disorders.GABA is the neurotransmitter that keeps you in check.

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Glutamate

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Glutamate is the anion form of glutamic acid and the most abundant neurotransmitter in the mammal brain.It has excitatory effect responsible for its functions.Glutamate is a non-essential amino acid, it can be got either from a normal diet or is locally synthesized from glucose.

Glutamate plays a role, especially in memory and learning.In addition, it's responsible for facilitating muscle movements in a complex process that include basal ganglia, Substantia Nigra, Thalamus, striatum...

Excess glutamate is toxic to the neurons, ALS disease (Stephan Hawking is suffering from it ), results from excessive glutamate production.Parkinson's disease is due to a lack of dopamine necessary for movements so the body tries to compensate for the lack of dopamine by releasing more glutamate causing a toxicity.Other diseases caused by glutamate toxicity include Autism and Alzheimer's disease.Although the genesis of these diseases is not fully understood, glutamate effect is fairly proven.

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Acetylcholine 

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Acetylcholine(ACh) is a neurotransmitter frequently referred by the term 'cholinergic'.ACh is produced from choline, which can be found in various foods such as eggs, meat, seafood, and nuts.

It has two types of receptors Nicotinic acetylcholine receptors responsible for the addictive effect of nicotine and Muscarinic acetylcholine receptors

ACh is responsible for the learning process, memory formation and the enhancement of alertness.In fact, cholinergic system defect is correlated with Alzheimer's disease.

Outside the nervous system, Ach is the final product of the cholinergic system which has different functions including muscle movement, respiration, digestion, controlling heart rate etc...

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Serotonin

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Serotonin (5-hydroxytryptamine '5-HT') is a neurotransmitter made from the essential amino-acid tryptophan which can be found in animal products and in plant proteins. 5-HT is synthesized and stored by specific neurons in the brain. Serotonin that is used inside the brain must be produced within it because it cannot cross the blood-brain barrier.

5-HT seems to involve in several regulation processes in the brain including mood, emotions, aggression, sleep, appetite, memory and sleep. Serotonin is involved in a resource based reward system -how good you are fulfilling your needs even 'power', In fact in 1997, Robert Huber and his team did a study on crustaceans, where they injected beta males with serotonin, most of these males became the new alphas in their communities. they became powerful, dominant and 'ready to fight'. Of course in humans, its much more complicated, but just like crustaceans serotonin can affect humans social behavior positively (alongside other effects). Thus, if you don't have enough of serotonin you are likely to be depressed. Sadly, if you have too much serotonin, there is a condition called serotonin syndrome (Leo Sternbach's study in 1991) in which you get very sick and it can even be fatal, therefore we have to maintain a healthy amount of serotonin.

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Dopamine

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Dopamine (3,4-dihydroxyphenethylamine 'DA') is a neurotransmitter, thus one of the chemicals responsible for transmitting signals to other nerve cells. Dopamine is manufactured in nerve cell bodies located within the ventral tegmental area (VTA).

Most of the dopamine pathways are part of the brain's reward system (especially ventral striatum) therefore when something good happens dopamine neurons become activated. Dopamine is normally released with rewarding activities like eating and sexual intercourse thus it's responsible for the pleasure.

References :   

https://blog.cognifit.com/types-of-neurotransmitters/

http://vibrantmethod.com/hrf_faq/different-types-of-neurotransmitters/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3860557/

https://www.ncbi.nlm.nih.gov/pubmed/9159179

https://www.ncbi.nlm.nih.gov/pubmed/2035713

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