1. Mood: serotonin

Serotonin is a neurotransmitter - one of the substances that is a chemical transmitter of impulses between the nerve cells of the human brain. Serotonin-responsive neurons are located almost throughout the brain.

Most of them are in the so-called "raphe nuclei" - areas of the brain stem. This is where the synthesis of serotonin occurs in the brain. In addition to the brain, a large amount of serotonin is produced by the mucous membranes of the gastrointestinal tract.

The directions of propagation of serotonin impulses from these nuclei affect many areas of both the brain and spinal cord.

It is difficult to overestimate the role that serotonin plays in the human body:

• In the front part of the brain under the influence of serotonin, the areas responsible for the process of cognitive activity are stimulated.

• Serotonin entering the spinal cord has a positive effect on motor activity and muscle tone. This state can be characterized by the phrase "I will move mountains."

• And, finally, and most importantly, an increase in serotonergic activity creates a feeling of an uplift in the cerebral cortex. For now, we will limit ourselves to just such a term, although in various combinations of serotonin with other hormones, we get the whole spectrum of emotions of “satisfaction” and “euphoria”.

Lack of serotonin, on the contrary, causes a decrease in mood and depression.

In addition to mood, serotonin is responsible for self-control or emotional stability. Serotonin controls the susceptibility of brain receptors to the stress hormones epinephrine and norepinephrine. In people with low levels of serotonin, the slightest stimulus triggers an exuberant stress response. Some researchers believe that the dominance of an individual in the social hierarchy is due precisely to the high level of serotonin.

In order for serotonin to be produced in our body, two things are necessary:

• dietary intake of the amino acid tryptophan, since it is it that is needed for the direct synthesis of serotonin in synapses;

• intake of glucose with carbohydrate food => stimulation of insulin release into the blood => stimulation of protein catabolism in tissues => increase in the level of tryptophan in the blood.

Such phenomena are directly related to these facts: bulimia and the so-called “sweet tooth syndrome”. The whole point is that serotonin can cause a subjective feeling of satiety. When food enters the body, including those containing tryptophan, the production of serotonin increases, which improves mood. The brain quickly catches the connection between these phenomena, and in case of depression (serotonin starvation) it immediately “requires” additional intake of food with tryptophan or glucose.

Surprisingly, tryptophan-rich foods are those that are made up almost entirely of carbohydrates, such as bread, bananas, chocolate, or net carbohydrates such as table sugar or fructose. This indirectly confirms the assertion that exists in society that people with a sweet tooth / overweight people are kinder than thin people.

Serotonin is metabolized in the body by monoamine oxidase-A (MAO-A) to 5-hydroxyindoleacetic acid, which is then excreted in the urine. The first antidepressants were monoamine oxidase inhibitors.

However, due to the large number of side effects caused by the broad biological action of monoamine oxidase, "serotonin reuptake inhibitors" are currently used as antipepressants. These substances make it difficult to reuptake serotonin in the synapses, thereby increasing its concentration in the blood. For example, fluoxetine (Prozac).

2.Day and night: melatonin

We have already found out that serotonin, firstly, is produced by food enriched with tryptophan and glucose, and secondly, it dulls the feeling of hunger. We found out why serotonin gives a surge of physical strength.

Serotonin has an antipode in the body - it is melatonin. They are synthesized in the epiphysis ("pineal gland") from serotonin. The secretion of melatonin directly depends on the general level of illumination: an excess of light inhibits its formation, and a decrease in illumination, on the contrary, increases the synthesis of melatonin.

It is under the influence of melatonin that gamma-aminobutyric acid is produced, which, in turn, inhibits the synthesis of serotonin. 70% of daily production of melatonin occurs at night.

It is melatonin synthesized in the pineal gland that is responsible for circadian rhythms - the internal biological clock of a person. As correctly noted, the circadian rhythm is not directly determined by external factors such as sunlight and temperature, but depends on them, since melatonin synthesis depends on them.

It is low light and, as a result, high production of melatonin that are the main causes of seasonal depression. Remember the emotional upsurge when a clear, fine day is issued in winter. Now you know why this happens: on this day you have a decrease in melatonin and an increase in serotonin.

I note that melatonin is not produced by itself - but from serotonin. And at the same time, he blunts his production. On these almost dialectical "unity and struggle of opposites" the internal mechanism of self-regulation of circadian rhythms is arranged. That is why, in a state of depression, people suffer from insomnia - in order to fall asleep, you need melatonin, and without serotonin, you can’t get it.

3. Pleasure: dopamine.

Consider another neurotransmitter: dopamine (or dopamine) is a substance of the phenylethylamine group. Like serotonin, it acts as a neurotransmitter and a hormone at the same time. Cardiac activity, motor activity, and even the gag reflex indirectly depend on it.

The hormone dopamine is produced by the adrenal medulla, and the neurotransmitter dopamine is produced by an area of ​​the midbrain called the black body.

We are interested in the dopamine neurotransmitter. Four "dopamine pathways" are known - brain pathways in which dopamine plays the role of a carrier of a nerve impulse. One of them, the mesolimbic pathway, is thought to be responsible for producing feelings of pleasure.

Dopamine levels peak during activities such as eating and sex.

Why do we enjoy thinking about the upcoming pleasure? Why can we savor the upcoming pleasure for hours? Recent studies show that the production of dopamine begins even in the process of waiting for pleasure. This effect is similar to the pre-salivation reflex in Pavlov's dog.

Dopamine is also believed to be involved in human decision making. At least among people with impaired dopamine synthesis/transport, many have difficulty making decisions. This is due to the fact that dopamine is responsible for the "sense of reward", which often allows you to make a decision, considering this or that action at a subconscious level.

4. Fear and rage: adrenaline and norepinephrine.

But not all vital processes of managing the human body take place in the brain. Adrenal glands - paired endocrine glands of all vertebrates also play an important role in the regulation of its functions. It is in them that the two most important hormones are produced: adrenaline and norepinephrine.

Adrenaline is the most important hormone that implements fight-or-flight responses. Its secretion increases sharply in stressful conditions, borderline situations, a sense of danger, anxiety, fear, trauma, burns and shock conditions.

Adrenaline is not a neurotransmitter, but a hormone - that is, it is not directly involved in the promotion of nerve impulses. But, having entered the bloodstream, it causes a whole storm of reactions in the body:

• enhances and speeds up the heartbeat;

• causes vasoconstriction of muscles, abdominal cavity, mucous membranes;

• relaxes the muscles of the intestines, and dilates the pupils. Yes, yes, the expression “fear has big eyes” and stories about the meetings of hunters with bears have absolutely scientific grounds.

The main task of adrenaline is to adapt the body to a stressful situation. Adrenaline improves the functional capacity of skeletal muscles. With prolonged exposure to adrenaline, an increase in the size of the myocardium and skeletal muscles is noted. At the same time, long-term exposure to high concentrations of adrenaline leads to increased protein metabolism, a decrease in muscle mass and strength, weight loss and exhaustion. This explains the emaciation and exhaustion in distress (stress that exceeds the adaptive capacity of the organism).

Norepinephrine is a hormone and neurotransmitter. Norepinephrine also increases with stress, shock, trauma, anxiety, fear, nervous tension. Unlike epinephrine, the main action of norepinephrine is solely to narrow blood vessels and increase blood pressure. The vasoconstrictive effect of noradrenaline is higher, although the duration of its action is shorter.

Both epinephrine and norepinephrine can cause tremor, that is, trembling of the limbs, chin. This reaction is especially clear in children aged 2-5 years when a stressful situation occurs.

Immediately after determining the situation as stressful, the hypothalamus secretes corticotropin (adrenocorticotropic hormone) into the blood, which, upon reaching the adrenal glands, induces the synthesis of norepinephrine and adrenaline.

The "invigorating" effect of nicotine is provided by the release into the blood epinephrine and norepinephrine. On average, it takes about 7 seconds after inhaling tobacco smoke for nicotine to reach the brain. In this case, there is a short-term acceleration of the heartbeat, an increase in blood pressure, an increase in breathing and an improvement in the blood supply to the brain. The accompanying release of dopamine contributes to the consolidation of nicotine addiction.

It is interesting that in different animals the ratio of cells synthesizing adrenaline to norepinephrine varies. Noradrenocytes are very numerous in the adrenal glands of predators and are almost never found in their potential prey. For example, in rabbits and guinea pigs, they are almost completely absent. Maybe that's why the lion is the king of animals, and the rabbit is just a rabbit?

It is believed that norepinephrine is the hormone of rage, and adrenaline is the hormone of fear. Norepinephrine causes