Neurotransmitters are chemical compounds secreted by the cells of the nervous system, neurons, responsible for transmitting the necessary information to different parts of the body.
Because they are communicated by synapses, these chemical mediators are usually found in presynaptic vesicles.
Examples of neurotransmitters are adrenaline, glutamate and gamma-aminobutyric “GABA”.
Types of neurotransmitters
Most neurotransmitters can be grouped into three classes:
- Amino Acids
- Amines
- Peptides
Neurotransmitters can be small molecules, such as amino acids and amines, or large molecules, such as peptides.
Amino acids and amines have in common the presence of nitrogen atoms in their structures. These neurotransmitters are stored in the synaptic vesicles and released from them.
Peptides are long chains formed by the union of amino acids. The storage and release of these neurotransmitters occurs in the secretory granules.
Below is a table with the main neurotransmitters.
| Amino Acids | Amines | Peptides |
|---|---|---|
| Γ-Aminobutyric acid (GABA) | Dopamine (DA) | Neuropeptide Y |
| Glutamate (Glu) | Adrenaline | Somatostatin |
| Glycine (Gly) | Serotonin (5-HT) | Substance P |
In addition to the types seen above, there are also acetylcholine type neurotransmitters, purines, gases and lipids.
How they work and the function of neurotransmitters
Its action is basically to combine with a target cell and the action results in transmission, modulation and amplification of information between neurons.
The cells have specific receptors for each type of neurotransmitter. The way a neurotransmitter influences a neuron can be classified into:
- Excitatory: creation of an electrical signal in the receptor neuron;
- Inhibitory: restriction of an action potential in the receptor neuron;
- Modulatory: regulation of the neuron population.
Excitatory and inhibitory neurotransmitters act quickly between the space of two neurons and are differentiated by the receptor they bind, that is, they depend on which receptor was activated. In addition, excitation or inhibition can also occur in a muscle fiber or a glandular cell.
Neuromodulators generate slower responses than excitatory and inhibitory neurotransmitters.
Neurotransmitters: synthesis, storage and release
Neurotransmitters are chemical messengers in chemical synaptic transmission, that is, they act in intercellular communication.
In this process, which occurs in milliseconds, neurotransmitters are synthesized, stored in synaptic vesicles, released from nerve endings in a region called the synaptic cleft.
After that, the neurotransmitters bind to the receptor proteins in the target cells. The tissue that received the information through the neurotransmitter is excited, inhibited or modified.
Main neurotransmitters
Neurotransmitters have several functions for the body, the most important of which are:
Acetylcholine (Ach)
Synthesized by the central nervous system and parasympathetic nerves, acetylcholine was the first neurotransmitter discovered, and is related to muscle movements, learning and memory.
The lack of acetylcholine in the body can trigger several neurological diseases such as Alzheimer’s disease (forgetfulness disease).
Adrenaline
Also called “epinephrine”, adrenaline is derived from norepinephrine (norepinephrine), synthesized in the adrenal medulla ( adrenal glands ) and in some cells of the central nervous system.
This neurotransmitter hormone is related to excitation, being released as a defense mechanism of the body in various situations that involve fear, stress, danger or strong emotions.
Noradrenaline (NA)
Also called norepinephrine, norepinephrine is an excitatory neurotransmitter like adrenaline. It acts in the regulation of mood, learning and memory, thus promoting disposition, since it is related to physical and mental arousal.
If the levels of this substance are altered in the body it can lead to an increase in heart rate and blood pressure. When reduced they can lead to depression and increased stress.
Endorphin
Considered the “pleasure hormone”, this substance is produced in the brain by the pituitary gland and is related to the improvement of mood and memory, the functioning of the immune system, control of pain and blood flow. Thus, the lack of endorphins can lead to stress, depression and anxiety.
Serotonin (5HT)
Synthesized by the central nervous system and when released into the body, it promotes a feeling of well-being and satisfaction. In addition, this natural tranquilizer controls sleep, regulates appetite and energy. Thus, it is known as the “pleasure substance”, and the lack of this neurotransmitter hormone in the body can trigger depression, stress, anxiety, among other problems.
Dopamine (DA)
Hormone released by the hypothalamus, associated with the feeling of well-being and the body’s motor controls. Changes in dopamine levels in the body can trigger several diseases, for example, Parkinson’s disease and schizophrenia. While Parkinson’s disease results from the lack of this neurotransmitter, schizophrenia is the opposite, that is, it can be generated by the excess of dopamine in the body.