The task of the neuroendocrine system is to regulate and combine nerve signals with hormonal signals, and then transform them into physiological acts that affect the synthesis of various hormones and their secretion.
These processes, like any other occurring in the body, are complex, important and interesting. They can be studied in detail for quite a long time, so now it is worth mentioning only the main aspects of this topic.
System interconnection
They should be mentioned before discussing the features of the endocrine glands of the endocrine and neuroendocrine system.
All connections are made through the pituitary and hypothalamus. These are the main parts of the brain. Nerve signals that enter the hypothalamus activate the secretion of releasing factors. Each of them is in contact with certain cells of the pituitary gland. As a result, tropins are formed - hormones of the anterior pituitary gland. They are needed toregulate certain endocrine glands. This is the notorious relationship.
But that's not all. Studying the principles of the functioning of the neuroendocrine system, it should be noted that hormones directly affect memory, behavior and the development of instincts. And these are processes that take place in the higher parts of the brain. Accordingly, the endocrine factor directly affects the state of the central nervous system. There simply cannot be a connection between them.
About regulatory processes
Their basis is precisely the symbiosis of the endocrine glands and the nervous system. What is their main task? Interacting with each other, they form a neuroendocrine system, the function of which is the secretion of hormones and neurotransmitters.
Where, in fact, are they produced? Hormones - in the endocrine glands. In tissues, in other words. Their ducts lead to the lymphatic or circulatory system.
Neurotransmitters are produced in the neural body or in the nerve endings. They accumulate in synaptic vesicles. These are, in simple terms, such containers in the cytoplasm, the diameter of which is only 50 nm. Interestingly, each such vesicle contains about 3000 mediator molecules.
How does secretion occur?
Since we are talking about the neuroendocrine system, this question should also be answered. When the body is at rest, spontaneous secretion of hormones occurs andneurotransmitters. They are produced in certain portions and with a certain frequency.
When the notorious synaptic vesicle bursts, all its contents are released into the synapse - a fractional number of neurotransmitter quanta.
It is worth mentioning that protein-peptide hormones and catecholamines are also produced in the blood in portions. After all, they, like neurotransmitters, are secreted through the emptying of vesicles. If the body is at rest, then this happens with a low frequency and spontaneously.
But the speed can increase due to the regulatory signal that has a stimulating effect on the endocrine gland. As a result, more hormones and neurotransmitters are produced. The inhibitory effect, in turn, is due to a decrease in the frequency of their release.
Secretion of steroid hormones
In continuation of the study of the specifics of the neuroendocrine system, it is necessary to pay some attention to this topic. Steroid hormones, unlike protein-peptide and catecholamines, do not accumulate in cellular structures. They pass through the plasma membrane freely, and all thanks to their inherent lipophilicity.
What, then, is the regulation of the functional activity of the glands, where hormones are produced, reduced to? To speed up and slow down their synthesis.
What about factors that inhibit and stimulate secretory activity? They, respectively, accelerate or slow down, including the biological synthesis of hormones. This rolethe neuroendocrine system plays by the feedback mechanism.
Hormonal effect
The time when it happens is determined by the arrival of a signal to a specific endocrine gland. How strong will the effect of the hormone be? It depends on signal strength.
In certain cases, the functional activity of the gland is regulated by the substrate, on which the action of the hormone is directed.
There is a completely understandable example: glucose actively affects the secretion of insulin, and it, in turn, reduces its concentration, as a result of which it is much easier to transport into tissues. What is the upshot? The stimulating effect of sugar on the pancreas is eliminated.
In the same way, by the way, calcitonin and parathyrin are secreted.
Maintaining homeostasis
This is one of the functions of the neuroendocrine system. The physiology of the human body is such that it cannot exist without self-regulation. An open system must maintain the constancy of its internal state. And for this, coordinated reactions are carried out, aimed at maintaining dynamic balance.
This is homeostasis - maintaining the constancy of the internal environment. And the previously described regulation, which occurs through the mechanism of the so-called feedback, is very effective in maintaining such “stability”.
Of course, the tasks of adaptation of the organism cannot be solved in this way. For example, glucocorticoids are produced by the cortexadrenal glands as a response to emotional arousal, disease and hunger. It is logical that the body can respond to these changes (as well as to smells, sounds and light), provided there is a connection between the nervous system and the endocrine glands.
An example should be given. This relationship is clearly seen in the process of regulation of the cells of the adrenal medulla, carried out by nerve fibers. It is in this area that adrenaline and norepinephrine are produced. What activates medulla cells? That's right, the electrical signals that pass through the synaptic transmission along the nerve fibers. The result is the synthesis and further secretion of catecholamines.
Studying the concept of the neuroendocrine system, it should be noted that the described method of closing connections is not considered the rule, but rather the exception. However, the cells of the medulla may well be considered as degenerated nervous tissue. And such regulation should be perceived as a connection preserved between nerve cells.
Diffuse neuroendocrine system
It also needs to be told. It has many names - chromaffin, gastroenteropancreatic, endocrine and nephroendocrine system, or simply DES. This is the name of a special section in the body. It is represented by endocrine cells scattered in different organs.
What function do they perform? They produce glandular hormones (peptides). DES is the largest link in the entire endocrine system. Her cells receive information not onlyfrom the outside, but also from the inside. In response, they produce peptide hormones and biogenic amines.
It should be noted that her cells are similar to peptidergic neurons. That is why in the future they began to be considered neuroendocrine. This, in fact, is indicated by the fact that they are contained both in neurons and in mast cells.
DES Composition
It also needs to be discussed, since we are talking about the glands of the neuroendocrine system and its significance for the body. DES form APUD cells - apudocytes that absorb the preceding amino acids and produce either low molecular weight peptides or active amines from them.
Structurally and functionally, they are divided into two types:
- Open. The apical ends of cells of this type reach the bronchial, intestinal and gastric cavities. They have microvilli that contain special receptor proteins.
- Closed. They do not reach organ cavities. These cells only receive information about the internal state of the body.
DES includes the atria, thymus (thymus gland), kidneys, liver, nervous and immune systems, tissue hormones, fat cells and lung epithelium.
Protection of the body
This is one of the main functions of the neuroendocrine system. All the above processes carried out by her are the basis for the formation of a protective complex necessary for removing toxins from the body, healing wounds.and suppress infection.
After all, there is no special system that "turns on" only when a person falls ill. Higher vegetative centers control, first of all, the duration of defense reactions and the strength of the whole organism.
What does the neuroendocrine system have to do with it? Despite the fact that the excitation of sympathetic nerves positively affects literally everything - muscle functions, parts of the brain, the cardiovascular system, internal organs, vascular tone, body temperature, sweating, pressure, blood clotting, etc. And as a result of the exerted their defensive reaction actions are also improved.
This fact, as well as many studies on this topic, made it possible to prove that the immune system, which protects the body from various harmful effects, obeys the same rule. There is simply a certain set of neurohumoral mechanisms, and they regulate its activity. Exactly the same as in the case of the neuroendocrine system.
