Messengers of the Body: A Breakdown of Major Neurotransmitters

Written by Emir Taha Macit

Neurotransmitters are chemical messengers that enable neurons, or nerve cells, to communicate with each other throughout the body. These messages, or signals, trigger responses in mere milliseconds, keeping the body functioning continuously across countless neurons. From reacting to a sharp pain like a paper cut to enjoying calm activities such as gardening, this process—known as synaptic transmission—is constantly occurring within you.

There are more than 100 known neurotransmitters, categorized by their chemical structure or function. The main classes include amino acid neurotransmitters, monoamine neurotransmitters, peptide neurotransmitters, and acetylcholine. Let’s explore each category and the key neurotransmitters they include.

Amino Acid Neurotransmitters

Amino acid neurotransmitters, derived from amino acids, operate in most parts of the nervous system. The main ones are glutamate, gamma-aminobutyric acid (GABA), and glycine.

Glutamate is the most common excitatory neurotransmitter in the central nervous system, responsible for passing messages between neurons. It is released from sensory neurons and the cerebral cortex, playing a key role in learning and memory. However, excessive glutamate activity can lead to epilepsy and other neurological disorders.

GABA, or gamma-aminobutyric acid, is the most common inhibitory neurotransmitter, meaning it prevents overstimulation by reducing neuronal activity. Derived from glutamate, GABA is released from neurons in various parts of the cerebral cortex, as well as in the spinal cord, cerebellum, and basal ganglia. It helps calm the brain, reducing anxiety and stress.

Glycine, another inhibitory neurotransmitter, is mainly active in the spinal cord. It regulates metabolism, manages pain transmission, and assists in

auditory processing.

Monoamine Neurotransmitters

Monoamine neurotransmitters are derived from single amino acids such as tyrosine or histidine. This group includes dopamine, serotonin, epinephrine, norepinephrine, and histamine.

Dopamine functions as both an excitatory and inhibitory neurotransmitter and influences focus, sleep, motivation, motor control, and pleasure. It is strongly linked to the brain’s reward system—its release encourages behaviors that produce pleasure, which can lead to addiction. Conversely, dopamine deficiency can cause Parkinson’s disease, ADHD, or schizophrenia. It is released from the substantia nigra in the brain.

Serotonin is primarily inhibitory but can also be excitatory. It regulates mood, sleep, and appetite, and its imbalance can cause anxiety or depression. It is mainly released from neurons in the brainstem.

Epinephrine and norepinephrine are excitatory neurotransmitters that trigger the body’s fight-or-flight response. They raise heart rate, sharpen decision-making, and prepare the body for emergencies. Overproduction can contribute to stress-related heart conditions. Epinephrine is released from the adrenal gland, while norepinephrine is secreted from the brainstem, hypothalamus, and adrenal gland.

Histamine, another excitatory neurotransmitter, regulates wakefulness and stomach acidity. It is mainly released from the hypothalamus, and irregular levels can contribute to asthma and sleep disorders.

Peptide Neurotransmitters

Peptide neurotransmitters are composed of amino acid chains. The primary ones are endorphins.

Endorphins are modulatory neurotransmitters, meaning they regulate the activity of other neurotransmitters rather than directly transmitting messages. They produce sensations of pleasure and relief, earning them the nickname “feel-good hormones,” alongside dopamine and serotonin. They are released throughout the brain, and a lack of endorphins may result in headaches or reduced stress tolerance.

Acetylcholine

Acetylcholine stands apart from other neurotransmitters. It consists of choline and an acetyl group and acts primarily as an excitatory neurotransmitter. It facilitates muscle contraction, sleep, and learning. It is found throughout the autonomic nervous system, and imbalances can lead to Alzheimer’s disease, seizures, or muscle spasms.

Neurotransmitters are essential to how we function, think, and feel. While their imbalance can lead to disorders, when maintained at healthy levels, they support every aspect of daily life—making them one of the most fascinating elements of the human body.

References:

1. “Neurotransmitters: What They Are, Functions”, Cleveland Clinic, 2022 https://my.clevelandclinic.org/health/articles/22513-neurotransmitters

2. Jana Vasković, “Neurotransmitters”, Ken Hub, 2023, https://www.kenhub.com/en/library/physiology/neurotransmitters

3. “Neurotransmitters”, Paris Brain Institute, 2025, 

4. https://parisbraininstitute.org/glossary/neurotransmitters