Neurotransmitters are chemical molecules in the central nervous system that relay the nerve impulse when nerve cells, or neurons, are stimulated. When that happens, they undergo chemical changes that produce tiny waves of electricity, i.e. nerve impulses.
Via these impulses, the brain communicates the messages received from the sensory stimuli to the other information processing areas of the brain.
What Are the Types of Neurotransmitters?
Neurotransmitters can be classified into 2 main groups: small molecule neurotransmitters and neuropeptides.
Small molecule neurotransmitters
The major molecule neurotransmitters of this group are the following:
- Aminoacids
- Gasotransmitters
- Monoamines
- Trace amines
- Peptides
Aminoacids
The amino acids are building molecules of proteins and have the most vital function in the human body. They are organic compounds composed of nitrogen, carbon, hydrogen, and oxygen.
The amino acids also contribute to the synthesis of hormones and neurotransmitters and are classified as essential, conditionally essential or nonessential.
Only 9 of these neurotransmitters belong to the group of essential amino acids, acids that the body can’t synthesize on its own and must obtain through diet:
- Histidine – Since this neurotransmitter stimulates the production of histamine, it has a vital function for digestion, and the sleep/wake cycles. It also supports the immune system.
- Isoleucine – It’s found in the tissues of the muscles, and plays a vital role in the production of energy, supports the immune system, and the production of hemoglobin.
- Leucine – A neurotransmitter that aids muscle repair and regulates blood sugar levels.
- Lysine – This neurotransmitter stimulates the production of collagen and elastin in the body. It also supports the synthesis of protein.
- Methionine – It’s important for the metabolism and detoxification of the body. This neurotransmitter also stimulates tissue growth and supports the absorption of two important minerals – zinc and selenium.
- Phenylalanine – It builds the structure and function of proteins and enzymes and is responsible for the production of other amino acids.
- Threonine – It supports the immune system of the body and comprises the structural proteins collagen and elastin. This makes it essential for the skin and connective tissue.
- Tryptophan – It’s a precursor of serotonin, thus aiding the regulation of appetite, mood, and sleep.
- Valine – It aids the growth of muscles and supports regeneration. Also, this neurotransmitter is involved in the production of energy.
Conditionally essential amino acids are needed when the body fights some stress or illness. The list of this type of neurotransmitters consist of:
- Arginine
- Cysteine
- Glutamine
- Tyrosine
- Glycine
- Ornithine
- Proline
- Serine
Nonessential amino acids are fatty acids that the body can synthesize. There are 11 neurotransmitters on this list:
- Alanine
- Arginine
- Asparagine
- Aspartic acid
- Cysteine
- Glutamic acid
- Glutamine
- Glycine
- Proline
- Serine
- Tyrosine
Each one of the nonessential amino acids can be used in the synthesis of the other NEAA’s.
Gasotransmitters
These neurotransmitters consist of nitric oxide, carbon monoxide, and hydrogen sulfide molecules. They support the regulation and control of the immune, cardiovascular, and central nervous system.
The list of gasotransmitters includes:
- Oxygen
- Carbon Dioxide
- Nitric Oxide
- Carbon Monoxide
- Hydrogen Sulfide
- Sulfur Dioxide
- Nitrous Oxide
- Hydrogen Cyanide
- Ammonia
- Methane
- Hydrogen
- Ethylene
These neurotransmitters are mainly found in the gastrointestinal tract and control many of the physiological functions of the body, such as excretion, digestion, blood flow, heart rate, etc.
Monoamines
The group of monoamines consists of the neurotransmitter hormones Dopamine, Noradrenaline, and Serotonin. Monoamines contribute to the control and regulation of emotions, the formation and storage of memory, and support secretion.
Very often, these neurotransmitters are included in the therapy of neurological disorders, such as depression, Parkinson’s disease, anxiety, etc.
Trace amines
These neurotransmitters regulate the concentration of the monoamines around the synaptic cleft of the cell, so they belong to the group of agonists.
The list of trace amines includes the following neurotransmitters:
- Phenethylamine
- N-Methylphenethylamine Phenylethanolamine.
- m-Tyramine
- p-Tyramine
- 3-Methoxytyramine
- N-Methyltyramine
- m-Octopamine
- p-Octopamine
- Synephrine
- Thyronamine compounds
- 3-Iodothyronamine.
- Tryptamine
Peptides
Peptides are short amino acid molecules that support some of the biological functions by acting as hormones. They aid wound healing, slow down the aging process, and contribute to the building of muscles.
Also, these amino acids have anti-inflammatory properties supported by their potential to destroy microbes.
The list of peptides includes the following neurotransmitters:
- Insulin
- Adrenocorticotropic hormone (ACTH)
- Calcitonin
- Oxytocin
- Vasopressin
- Octreotide
- Leuprorelin
How Do Neurotransmitters Trigger the Action Potential of Neuronal Cells?
The neuro-transmitting chemical neurons are created by the presynaptic neuron – a cell that is in charge of sending the impulse. Each axon of a neuron cell ends in a bulb-like structure called synaptic knob, which possesses synaptic vesicles. This is where the neurotransmitters are stored.
The postsynaptic neuron has chemically reactive ion channels in its membrane, or neuroreceptors, with dedicated connecting sites for the neurotransmitters. The electric impulses of a neuron cell are not able to cross the synaptic cleft between neurons, i.e. the synapse.
Due to this, the cell triggers a release of neurotransmitters, in order to be able to relay the information to the neuroreceptors.
This release includes several complex phases:
- Depolarization of the terminal membrane of the neuron cell
- Activation of the calcium channels
- The entry of Calcium molecules into the neuron cell
- Formational change of specific proteins of the docked synaptic vesicle
- A fusion of the vesicles that causes the release of the neurotransmitter into the synaptic cleft
- The branching of neurotransmitters toward the receptors on the postsynaptic cell
At the end of the aforementioned process, the neurotransmitter molecules pass through the synapse and stimulate the receiving neuron to fire an impulse of its own. This creates wavelike movements of the electrically charged particles, i.e. an action potential of the neuron.
What Happens When a Neurotransmitter Is Blocked?
Neurotransmitters constantly transmit a large number of signals between the neurons, which are received through a receptor. A receptor is a protein in the membrane of neural cells that a neurotransmitter, a drug, or a hormone can bind itself to and create a biochemical reaction in the brain.
In order for the receptor to produce a biological response in the human brain, it needs to be activated by a chemical that binds to it, thus triggering its activation. An agonist drug is responsible for triggering the action potential of the neuron cell that releases the neurotransmitters into the synapses. In other words, agonists support and intensify the effect of the neurotransmitters.
Furthermore, there is a special type of chemical substances that become a part of the biomolecule in order to block the biological response of the receptor. These types of chemical substances are called antagonist drugs or blockers.
These types of drugs inhibit, block, or reverse the action potential of the neuron receptor and the neurotransmitter molecules. Due to this, the neurotransmitters which relay the stimuli received through the sensory organs can become deterred or blocked.
Which Neurotransmitters Are The Most Important for the Brain?
Among the numerous neurotransmitter chemicals, there are 4 which stand out as most important for both the brain and the functions of the body. Those are:
- Serotonin
- Dopamine
- Glutamate
- Norepinephrine
Serotonin
Serotonin is a neurotransmitter hormone that is responsible for the transmission of information among the neurons of the brain. It supports the cognitive processes, as well as the formation of memory.
The levels of serotonin also influence the following functions of the body:
- hormonal activity
- concentration
- body temperature
- appetite
- the sleep-wake cycle
- mood and emotions
- metabolism and appetite
Dopamine
The neurotransmitter dopamine is a chemical that supports the brain processes which control and regulate motivation, desire, and cravings. It’s also in charge of our mood, the regulation of the control and reward systems in the brain, as well as muscle contraction and movement.
The levels of dopamine influence the following functions of the body:
- mood
- sleep cycles
- cognitive processes
- muscle movement
- alertness and concentration
- blood flow
High levels of dopamine in the blood can result in euphoric feelings, increased concentration, and motivation.
Glutamate
The neurotransmitter glutamate is found in both the brain and the spinal cord. This powerful neurotransmitter supports the transmission of signals between the two neuron cells.
It also plays a vital function in the early development of the brain, in the cognitive processes (especially learning), perception, as well as memory.
When the concentration of glutamate is too small, it can lead to coma, psychosis, or even death. On the other hand, an extremely high concentration of this neurotransmitter can cause seizures and brain cell death.
Norepinephrine (also: Noradrenaline)
This neurotransmitter supports the heart rate and the contractions of the skeletal muscles, which are vital for the fight or flight response of the body. It functions both as a hormone and as a neurotransmitter.
In addition, norepinephrine helps the regulation of blood sugar levels in order to increase the energy levels of the body
To Sum Up
There are various types of information that passes from the senses through the neuronal network of the human body in order to be processed in dedicated areas of the brain.
From there, the processed information is relayed to the brain in the form of a decision, reaction, or command as a response to the encoded stimuli.
The result of the processed information comes in the form of electrical impulses that flow along the nerves to the corresponding parts of the body with the help of neurotransmitters, in order to stimulate and coordinate movement.
Without the neurotransmitters, our brain would lose the ability to make use of the chemical molecules which are of vital function for the body.
Fun Facts
Did you know?
- There are more than 200 distinctive neurotransmitters identified in the human brain.
- Neurotransmitters may also actively inhibit a receiving neuron from firing (passing the sensory information between two neurons via the axons).
- The synapse will not be able to renew its supply of neurotransmitters fast enough to continue passing the impulse across the cleft if a neuron is constantly stimulated.
- Serotonin is a neurotransmitter that helps us with memory and learning.
- A nerve impulse is based chiefly on the movement of positively charged sodium and potassium ions through the neuron’s cell membrane.
- Impulses travel at speeds of between 3–400 ft/s (1–120 m/s), depending on the type of nerve. Movement is faster in myelin-coated axons.
- “Neurotransmitters are transported within the neurons by small “sacs” called vesicles.”
- In order to grow and function properly, our body needs at least 20 different amino acids.
- The essential amino acids cannot be supplemented. Thus, they must be ingested through a proper diet consisting of meat, eggs, and poultry.
- The amino acid leucine supports the healing of wounds.