Neurotransmitters and their Functions

The transmission of signals from one neuron to another, across the synapse was earlier thought to be electrical. Synapse is a small gap or junction between two neurons or a neuron and a muscle. In 1921, it was confirmed that neurons actually communicate by releasing certain chemicals. The communication takes place through a change in chemical concentration and these chemicals are called neurotransmitters. The credit for confirming this fact and also for discovering the neurotransmitter, acetylcholine goes to the German pharmacologist, Otto Loewi. So, neurotransmitters are the chemicals that allow the nerve impulses or signals to be transmitted across the synapse. There are several types of neurotransmitters and each one of them is responsible for some specific functions. Given below is some more information about the types of neurotransmitters and their functions.

Types of Neurotransmitters

There are a number of neurotransmitters, which can be classified in many different ways. But, more commonly they are classified into three categories - amino acids, monoamines and peptides. Neurotransmitters like glutamate, aspartate, glycine, serine and gamma aminobutyric acid (GABA) fall into the category of amino acids. On the other hand dopamine neurotransmitter, serotonin, melatonin, epinephrine and norepinephrine are the monoamine neurotransmitters. Calcitonin, glucagon, vasopressin, oxytocin and beta-endorphin are some of the neuroactive peptides. There are about 50 neuroactive peptides till now, with new ones being discovered regularly. Apart from these, acetylcholine, adenosine and nitric oxide are some other noteworthy neurotransmitters. Out of all these neurotransmitters, we are going to discuss the most well-known and important neurotransmitters and their functions.

Neurotransmitters and Their Functions

Acetylcholine, dopamine, GABA, serotonin, epinephrine, norepinephrine and endorphins are the most significant or crucial neurotransmitters found in the human body. The functions of these neurotransmitters are explained below.

Acetylcholine
It is the first neurotransmitter to be discovered in the year 1921. This neurotransmitter is responsible for stimulating muscles. It activates the motor neurons that control the skeletal muscles. It is also concerned with regulating the activities in certain areas of the brain, which are associated with attention, arousal, learning and memory. People with Alzheimer's disease are usually found to have a substantially low level of acetylcholine.

Dopamine
Dopamine is the neurotransmitter that controls voluntary movements of the body and is associated with the reward mechanism of the brain. In other words, dopamine regulates the pleasurable emotions, and drugs like cocaine, heroin, nicotine, opium and even alcohol increase the level of this neurotransmitter, for which the user of such drugs feels good. Decreased level of dopamine is associated with Parkinson's disease, while the patients of schizophrenia are usually found to have excess dopamine in the frontal lobes of the brain.

Serotonin
Serotonin is an important inhibitory neurotransmitter, which has been found to have a significant effect on emotion, mood and anxiety. It is also involved in regulating sleep, wakefulness and eating. A significantly low serotonin level is found to be associated with conditions like depression, suicidal thoughts and obsessive compulsive disorder. Many antidepressant drugs work by affecting the level of this neurotransmitter.

Gamma Aminobutyric Acid (GABA)
GABA is an inhibitory neurotransmitter that slows down neuron activity in order to prevent their over excitation, which could lead to anxiety. GABA is a non-essential amino acid, that is produced by the body from glutamic acid. A low level of GABA can have an association with anxiety disorders. Alcohol and drugs like barbiturates can influence GABA receptors.

Glutamate
Glutamate is an excitatory neurotransmitter. It is the most commonly found neurotransmitter in the central nervous system. Glutamate is mainly related with functions like learning and memory. An excess of glutamate is however toxic for the neurons. An excessive glutamate production may be related with the disease, known as amyotrophic lateral sclerosis (ALS) or Lou Gehrig's disease.

Epinephrine and Norepinephrine
Epinephrine is an excitatory neurotransmitter, that is derived from norepinephrine. Epinephrine controls mental focus and attention. Norepinephrine is also an excitatory neurotransmitter and it regulates mood and both physical and mental arousal. Increased secretion of norepinephrine raises the heart rate and blood pressure.

Endorphins
Endorphins are the neurotransmitters that resemble the opioid compounds like opium, morphine and heroin in structure. In fact, their effect on the body is also similar to the effect produced by the opioid compounds. Like opioids, endorphins can reduce pain, stress and promote calmness and serenity. These are the neurotransmitters that enable some animals to hibernate by slowing down metabolism, respiration and heart rate.

So, these were some of the most common and well-known neurotransmitters and their functions. Hope this article provided some interesting facts about the neurotransmitters that allow the nerves to communicate with each other and thus, regulate the various functions of the body.