The endocrine system

Think of the brightest moments of your life. Isn’t it true, the moments when we experienced strong feelings emerge in my memory - love, joy from victory, all-consuming tenderness, and, perhaps, fear, which made it petrify? All these feelings are a gift from our endocrine system, because they arise from the effects of hormones on nerves, muscles, lacrimal glands and butterflies in the stomach.  How does the endocrine system work, why can we experience such a wide range of feelings, why hormones sometimes enslave us and how can we manage them?

"Heart stopped, and then started to beat fast, muscles are stiff, the back of his head tingled, his mouth was dry, his back crawling on his forehead is cold sweat".

«His breath caught, his heart pounded, his arms and legs quivered, his cheeks reddened, the fever poured over his chest and stomach, his eyes glittered» . 

Even if you don’t call the feelings for which these manifestations are characteristic, we still guess that we’re talking about fear and attraction, because the majority of healthy, mentally normal people have physical expressions of feelings, especially strong ones, are very similar. The effects of “recognizing yourself” in the heroes of books and films are based on this.

What’s the basis of such reactions? Most of us will say about the nerves. But in fact, the nerve impulse is only a trigger that activates a storm, which is ruled by hormones. The activities of the hormonal (endocrine) and nervous systems are closely intertwined.  Therefore, the effects that these systems together have on the body are called neuro-endocrine regulation.

The hormonal (endocrine) system has a clear hierarchy: there are “governing” organs, and there are executing glands. The hypothalamus has the highest place in this hierarchy. 

Hypothalamus - the emperor of the hormonal system

The hypothalamus is often referred as an emperor or conductor of the hormonal system. This unique structure, located in the brain, which is called the intermediate, combines the properties of the nervous tissue and gland. Its cells are called so-neurosecretory, in response to the incoming nerve impulse, they’re excited (like the cells of the nervous system) and begin to synthesize hormones (like glandular cells).

A hypothalamus is a huge computer connected to all structures of the brain and spinal cord. Here comes information about the state of the internal environment of the body (body temperature, energy balance, water and salt metabolism, blood pressure, etc.). And the "wires" coming from the senses, notify the hypothalamus about events occurring "from the outside."  It’s here that nerve impulses are "translated" into the language of hormones.

Having received the information on the basis of which an adjustment of the internal environment or behavior is required, the hypothalamus “addresses” to its assistant, the pituitary gland.

Pituitary gland - executive is in action

The pituitary gland, unlike the hypothalamus, doesn’t claim to be the brain, but is content with the name of the gland. It’s not simple but the most important. In fact, the pituitary gland is a conductor conveying the “decisions of the emperor” to the executors of iron. In the hypothalamus, two types of hormones are produced - liberins and statins.  The former stimulate the formation of hormonal substances in the pituitary gland, and the latter inhibit. For small vessels, which are called the portal system of the pituitary gland, they enter it and activate the production of hormones that affect the body.

In total, about 15 hormones are synthesized in the pituitary gland. Some of them act sighting on a specific gland. 

Others have a systemic effect on the entire body. For example, the growth hormone pituitary hormone activates bone growth in children and adolescents, affecting growth areas in the tubular (long) bones, its deficiency is the cause of dwarfism. Also, somatotropic hormone is one of the main creators of the body, it stimulates the synthesis of proteins in the connective tissue, muscles, helping to recover from physical exertion, helps to burn fat faster, etc.

The pituitary and hypothalamus together form the hypothalamic-pituitary system. The total mass of these organs barely reaches six grams. Nevertheless, it’s a control center not only for the work of our body, but also for emotions, instinctive reactions, the potential of long life, etc.

Hormones on the periphery

Hormones that are synthesized by the pituitary gland under the guidance of the hypothalamus, with blood flow are brought to the endocrine glands: the thyroid, thymus, pancreas, as well as the ovaries, testes, adrenal glands. In response to these “hormonal messages,” the glands activate (or, on the contrary, block) the production of their own hormones, which causes the corresponding physiological effects.

The sequence of transmission of hormonal signals from the hypothalamus to the pituitary gland and the end gland is called the regulatory axis. Thus, the hypothalamic-pituitary-adrenal axis is responsible for regulating the formation of adrenal hormones (for example, adrenaline or noradrenaline). For the production of thyroid hormones - the hypothalamic-pituitary-thyroid axis, for the synthesis of sex hormones - the hypothalamic-pituitary-gonadal axis.

At the same time, some pituitary hormones (for example, somatotropic hormone) don’t use other glands as levers to achieve the desired effects, but induce the necessary physiological reactions directly affecting the tissues.

Intestines and the heart as glands

In addition to the endocrine cells that make up the "official" glands, there are cells with the same function - the formation of hormones - but scattered throughout the body.  Scientists have counted more than 60 types of apudocytes, as they call endocrine-like cells located in a variety of organs. The cells that have hormonal activity, but aren’t part of the “official” endocrine system, were called by the scientists a diffuse (that is, penetrating everywhere) neuroendocrine system.

The largest accumulation of hormone-producing cells is in the gastrointestinal tract: in the stomach, pancreas, large and small intestines.

Some hormones, such as gastrin, produced by the glandular cells of the intestine, are mainly concerned with the regulation of digestion. But cholecystokinin, which is synthesized in the duodenum, affects both food digestion and human behavior, preventing the development of depressive states.

The lion's share of serotonin - a hormone of good mood - is produced by intestinal secretory cells (from 60 to 80% of the total serotonin in the body). And in the pancreas an exact analogue of the somatotropic hormone of the pituitary gland is formed, which has the same effect on metabolic processes.

Hormonal "hobby" of the kidneys is to produce renin, which increases blood pressure, and erythropoietin, which stimulates the formation of blood cells. The heart also don’t remain aloof from hormonal activity: the atrial natriuretic hormone is synthesized here, forcing the kidneys to remove sodium and the water faster.

And even such an inert substance as fatty tissue, also shows hormonal initiative, producing leptin. This hormone increases the sensitivity of cells to insulin (pancreatic hormone, which facilitates the penetration of glucose into cells). And in large doses (with severe obesity) leptin inhibits the formation of insulin, which leads to the development of type II diabetes.

Epiphysis: gland-puzzle

The epiphysis (or pineal gland) stands alone among the organs of the endocrine system. It’s called a mystery gland as precisely with this tiny organ located in the center of the brain and weighing less than one gram has been associated with the ability of a clairvoyant since antiquity. And modern scientists jokingly call the epiphysis "gray cardinal."  As far as researchers know, this crumb-gland doesn’t obey the orders of the "hormonal government" - the hypothalamic-pituitary system - but, on the contrary, affects its activity.

Substances that are produced by the pineal gland, block the formation in the pituitary gland and epiphysis hormonal signals that activate the work of the genitals. When violations of its work comes early puberty, premature and excessive appearance of secondary sexual characteristics.

It’s also known that the epiphysis, which is considered an analogue of the unpaired parietal eye in some animals, reacts to light and regulates daily biorhythms. Studies show that sleep and wakefulness depends on the hormone melatonin, which is synthesized in the pineal gland at night.

Due to the isolation of the pineal gland, its independence from the effects of the hypothalamic-pituitary system, scientists attribute the pineal gland to the organs of the diffuse neuroendocrine system - as well as hormone cells of the intestine, kidney, heart, etc.

Why hormones are released: external and internal effects

A cascade of hormonal reactions can trigger external stimulation, irritation of nerve endings. For example, we walk in the forest and see a bear (impulse from the visual analyzer) or not see, but we hear the crack of the bushes (impulse from the auditory analyzer). We can sense the smell that the brain connects with a potential hazard (olfactory analyzer) or feel the touch of a paw (tactile receptor irritation).

The impulse from nerve endings rushes to the cerebral cortex, and from there to the hypothalamus, activating the areas responsible for communication with the adrenal glands (hypothalamic-pituitary-adrenal axis).

The hypothalamus secretes the hormone corticoliberin, which enters the pituitary gland, which synthesizes the hormone adrenocorticotropin. The latter with blood flow is delivered to the adrenal glands and activates the production of stress hormones - adrenaline and cortisol.

Adrenaline is carried in the body through the blood, stimulating the sensitive nerve endings, called adrenoreceptors. Their stimulation leads to the appearance of familiar signs of great fear. The whole process takes place very quickly: from the moment of excitation of the receptors (visual, auditory, etc.) and pass until a sign of fright appears, they pass in a split second. This time is enough for the body to instantly put us on alert in a meeting with danger.

The synthesis of many hormones is practically independent of external influences.  For example, the intensity of thyroid hormone production (triiodothyronine, thyroxin and calcitonin, affecting metabolism, tissue growth and development) varies depending on the increase or decrease in the concentration of these hormones in the blood.

If the content of thyroid hormones in the bloodstream is reduced, the hypothalamus receives a signal of the need to stimulate the process of their formation (hypothalamic-pituitary-thyroid axis). In the cells of the hypothalamus, thyrotropin-releasing hormone (TRH) is synthesized, which induces the pituitary cells to produce thyroid-stimulating hormone. This hormone enters the bloodstream, reaches the cells of the thyroid gland and activates the formation of hormones.

Conversely, a high content of thyroid hormone levels in the blood “blocks” the formation of thyroid-stimulating hormone in the pituitary gland. And, accordingly, the synthesis of new hormones in the thyroid gland slows down.

Hormonal prints of feelings

Why are the feelings that each of us experiences, so similar? Because the basis of their occurrence are physiological reactions caused by a certain ratio and concentration of the same hormones. Almost all known emotions, scientists were able to "decompose into hormones."

Some feelings are the result of a single hormone. For example, fear is the domain of adrenaline. This hormone, entering the blood from the adrenal glands, is able to bestow on us all the attributes of a strong fright: a heartbeat, cold sweat, an increase in muscle tone, giving the opportunity to fight with a source of fear ... or flee away.

For the emergence of other feelings there’s a need of bunch cocktails of hormones.  For example, love is the real “hormonal smoothie”, the composition of which depends on the phase of the relationship. At the initial stage, dopamine predominates, forcing to achieve the desired object, adrenaline, giving the lover an excess of strength. But the level of serotonin - the hormone of joy - fluctuates, forcing it to soar in the sky, then fall into depression. When meeting with the object of passion (as well as when thinking about it) there is a release of testosterone in both men and women: by acting on the receptors, it leads to the appearance of signs of sexual attraction.

When stability comes to replace passions, the concentration of the oxytocin, which is synthesized in the pituitary gland, rises in the body. Influencing the brain, it contributes to the emergence of affection, tenderness, trust.

How can you affect the release of hormones?

The connection between the nervous and hormonal systems underlies both the beneficial effects that improve life and often becomes the basis for the formation of bad habits.

For example, the decision to do sports for an untrained person in the initial stages may be accompanied by a release of stress hormones.  One imagines an unusual situation, imagines discomfort - such thoughts lead to the formation of the hormone cortisol.

As a result, the heartbeat increases, pressure increases - the person is already experiencing the full range of negative feelings, which he believes he will have to go through in the future. Such a link between thoughts and hormones often becomes an obstacle to any changes in life.

But, if a person still overcomes fear and goes to workout, copes with the first negative feelings that are natural to get out of the usual mode of existence, his body soon begins to receive hormonal bonuses. Endorphins, which are produced during exercise, improve health, give a sense of joy. And now the thought of training leads not to the release of stress hormones, but to the formation of endorphins, which increases the motivation to practice further.

This ability of the body to change the hormonal background, not only when meeting with real situations, but also when thinking about them, is the basis of self-programming.  The problem’s that the body gets used to the state in which it’s located most of the time, even if this condition is negative.

So, in response to some situation that caused a feeling of resentment, the release of hormones cortisol, norepinephrine, melatonin. The entry of these hormones into the blood causes a chain of chemical reactions that leads to irritation of certain nerve endings. As a result, we feel fear, anger, and sadness, which make up the grievance.

If you deal with the stressful situation, the hormones that provoke negative feelings stop being produced. But in the case when a person doesn’t cease to think about insult, hormones continue to be synthesized: the endocrine system doesn’t feel the difference between a real event and thoughts about it.

When such thoughts (and, accordingly, hormonal reactions) persist day after day, the body becomes accustomed to such a state at the chemical level.  And now the feeling of resentment (anger, guilt, etc.) becomes a zone of comfort, and the feeling of joy and the corresponding hormonal background - going beyond the usual framework.

This “negative biochemistry” of the body is the reason why correct actions don’t bring positive results always. Therefore, many practices aimed at improving life, first of all, include work with thoughts.

It’s recommended to be positive at the mind level, accustoming the body to "good hormones" and only then perform actions that support a positive result and allow you to form positive dynamics at both the biochemical and physical levels.

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