The nervous system is a complex set of cells in charge of controlling, supervising, and directing all the activities and functions of our organs and organism in general. It captures stimuli from the environment (external stimuli) or signals from the same organism (internal stimuli), processes the information, and generates different responses depending on the situation. It is mainly made up of neurons. These function to coordinate the actions of living beings in the animal kingdom through chemical and electrical signals that are sent from one place to another in the body through neural connections (synapse). Through the aforementioned neuronal connections (synapse), substances are exchanged. This allows the transmission of information from one neuron to another neuron, muscle cell, or gland. Those substances are neurotransmitters and neuromodulators.
Neurotransmitters are chemical molecules released by the presynaptic neuron, which transmit signals to the postsynaptic neuron or to a non-neuronal cell. The neurotransmitter is released through the vesicles, and then it crosses the presynaptic space to, finally, interact with the postsynaptic neuron modifying its action potential, to produce a specific physiological response depending on the biological needs of the individual. The primary function of neurotransmitters is to inhibit or excite the activity of the postsynaptic cell; that is, depending on the type of receptor, neurotransmitters can enhance or decrease its functioning.
On the other hand, there are neuromodulators. They are chemical molecules capable of changing the effect of impulse transmission in neurons without altering the speed of transmission. It happens through the control of the synthesis and release of neurotransmitters. They are available in a wide area of the nervous system. The action of a neuromodulator is not limited to a particular neuron or the site of release. It can be effective in several neurons or “target” cells. The key difference between the neurotransmitter and the neuromodulator is that the neurotransmitter is a chemical released by the neuron to send signals to the next neuron. In contrast, the neuromodulator is a chemical released by the neuron to alter the effectiveness of the transmission of the neuron signal. Neuromodulators can modulate the signal transmission by controlling the synthesis and quantity of neurotransmitters released in response to stimuli.
The Most Common Neuromodulators
Some of the most common neuromodulators in the central nervous system are:
Dopamine – Dopamine is often considered to be the cause of pleasant sensations and the sensation of relaxation. This substance is distributed in different regions of our brain, and in each area it plays a different role. We all need an adequate level of this neurotransmitter, not only this, but we also need it to be properly distributed in our brain in order to carry out a myriad of functions. For example, thanks to it, we encourage ourselves to be competitive, to create that sense of defense in the face of some danger, and to motivate us to fulfill some personal goals. It influences our mood, our behavior and is essential to regulate our metabolism. Among these things, it is also considered to be responsible for pleasure. It is key to promoting the processes of seduction, sexuality, and desire.
Serotonin – Serotonin is closely related to the control of emotions and mood, although it also fulfills other types of functions:
- Regulates the appetite causing the sensation of satiety.
- Control of body temperature.
- Regulates sexual appetite.
- Controls motor activity, perception, and cognitive function.
- Together with dopamine and norepinephrine, it participates in the mechanisms that govern anxiety, fear, anguish, and aggressiveness.
- Regulates secretion of some hormones, such as melatonin, a protein among whose many functions is to regulate circadian rhythms and sleep.
- Plays a vital role in the development and maintenance of the bone structure.
- It is involved in the functioning of the vascular system.
- Induce cell division.
Acetylcholine – It was the first neuromodulator to be discovered in 1914. The different elements that are responsible for its synthesis and elimination make up the so-called cholinergic system. Acetylcholine is mainly seen as an excitatory neuromodulator, but it can also exert an inhibitory action depending on the type of synapse in which it acts. Its functions include motor control, hormone production, learning, pain perception, and memory formation.
Histamine – Histamine is a molecule derived from an essential amino acid, histidine, and is produced by decarboxylation thanks to the enzyme L-histidine decarboxylase. Histamine has many physiological and pathophysiological functions:
- Participates in the regulation of local circulation
- It controls capillary hyperpermeability
- Induces the contraction and relaxation of smooth muscles and blood vessels
- Promotes the secretion of hydrochloric acid in the stomach
- It participates in allergic processes, inflammatory processes as part of an immune response to external pathogens
- Its action as a neurotransmitter of the central nervous system has also been identified.
Noradrenaline – Norepinephrine regulates the activity of neuronal and non-neuronal cells. It promotes the correct function of cortical circuits and metabolism. It plays an important role within the brain, including participation in suppressing the neuroinflammatory response, stimulating neuronal plasticity through lipid transporter protein (LTP), regulating glutamate uptake, and consolidating memory.
Conclusion – As we have seen, neurotransmitters and neuromodulators are very important elements for our mental health and also for the correct functioning of the nervous system. These elements regulate the way in which we perceive the world since they indicate to the body how it should behave in the face of external and internal stimuli. The imbalance in the production and functioning of neurotransmitters can lead to multiple problems that directly influence our emotional well-being. Maintaining a good diet, practicing sports, maintaining healthy lifestyles, enjoying others, enhancing the sense of humor, and having contact with nature, are the keys for these elements to work optimally.