The task of the neuroendocrine system is to regulate and combine nerve signals with hormonal ones, and then transform them into physiological acts that affect the synthesis of various hormones and their secretion.
These processes, like any other processes occurring in the body, are complex, important and interesting. They can be studied in detail for quite some time, so now it’s worthwhile to pay attention only to the main aspects of this topic.
Interconnection systems
They should be mentioned before discussing the features of the endocrine and neuroendocrine system endocrine glands.
All connections are made using 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 pituitary cells. As a result of this, pathways are formed - hormones of the anterior pituitary gland. They are needed to regulate certain endocrine glands. This is the notorious relationship.
But that is not all. Studying the principles of 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 occur 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 concern? 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 are excreted into the lymphatic or circulatory system.
Neurotransmitters are produced in the neural body or in nerve endings. They accumulate in synaptic vesicles. In simple terms, these are such capacities in the cytoplasm, the diameter of which is only 50 nm. Interestingly, in each such bubble contains about 3000 mediator molecules.
How does secretion occur?
Since this is a neuroendocrine system, this question should be answered. When the body is at rest, spontaneous secretion of hormones and neurotransmitters occurs. They are produced in certain portions and with a certain frequency.
When the notorious synaptic vesicle bursts, all its contents - the fractional number of quanta of neurotransmitters - are released into the synapse.
It is worth mentioning that protein-peptide hormones and catecholamines are also produced in the blood in batches. After all, they, like neurotransmitters, are secreted by emptying the 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, which 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.
Steroid hormone secretion
In continuation of the study of the specifics of the neuroendocrine system, it is necessary to pay a little 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? To accelerate and slow down their synthesis.
What about the factors that inhibit and stimulate secretory activity? They, respectively, accelerate or slow down, including the biological synthesis of hormones. The neuroendocrine system plays this role by the feedback mechanism.
Hormonal effect
The time when it happens is determined by the arrival of a signal on a particular gland of internal secretion. How strong is the hormone effect? It depends on the strength of the signal.
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 more easily transported to tissues. What is the outcome? 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 without self-regulation it cannot exist. An open system must maintain the constancy of its internal state. And for this, coordinated reactions are carried out, aimed at maintaining dynamic equilibrium.
This is homeostasis - maintaining the constancy of the internal environment. And the previously described regulation, which occurs according to the so-called feedback mechanism, is very effective for maintaining such “stability”.
Of course, the tasks of adapting the body in this way cannot be solved. For example, glucocorticoids are produced by the adrenal cortex as a response to emotional arousal, illness, 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 connection 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 brain cells? That's right, electrical signals that pass through nerve fibers through synaptic transmission. As a result, synthesis and further secretion of catecholamines occurs.
Studying the concept of a neuroendocrine system, it should be noted that the described method of closing bonds is considered not a rule, but rather an exception. However, the cells of the brain layer can be considered as a degenerated nervous tissue. And such regulation should be perceived as a connection between nerve cells.
Diffuse neuroendocrine system
It is also necessary to tell about it. It has many names - chromophin, gastroenteropancreatic, endocrine and nephroendocrine system, or simply DES. This is the name of a special department in the body. It is represented by endocrine cells scattered in different organs.
What function do they perform? Glandular hormones (peptides) are produced. DES is the largest link in the entire endocrine system. Its cells receive information not only from the external, but also from the internal environment. In response, they produce peptide hormones and biogenic amines.
It should be noted that its cells are similar to peptidergic neurons. That is why in the future they began to be considered neuroendocrine. In fact, this is indicated by the fact that they are contained both in neurons and in mast cells.
The composition of the DES
It also needs to be discussed, since we are talking about the glands of the neuroendocrine system and its importance for the body. DES form APUD cells - apudocytes that absorb the preceding amino acids and produce from them either low molecular weight peptides or active amines.
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 specific receptor proteins.
- Closed. They do not reach the cavity of the organs. These cells only receive information about the internal state of the body.
DES includes atria, thymus (thymus gland), kidneys, liver, nervous and immune systems, tissue hormones, fat cells and lung epithelium.
Body protection
This is one of the main functions of the neuroendocrine system. All of the above processes carried out by her are the basis for the formation of the protective complex necessary to remove toxins from the body, heal wounds and suppress infection.
After all, there is no special system that “turns on” only when a person becomes ill. Higher vegetative centers control, first of all, the duration of protective 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 the sympathetic nerves positively affects literally everything - muscle functions, parts of the brain, cardiovascular system, internal organs, vascular tone, body temperature, sweating, pressure, blood coagulation, etc. And as a result by them the action of the protective reaction is also improved.
This fact, as well as many studies on this topic, have proved that the immune system, which protects the body from various harmful influences, follows the same rule. There is simply a certain complex of neurohumoral mechanisms, and they regulate its activity. In the same way as in the case of the neuroendocrine system.