The human autonomic nervous system includes three areas: sympathetic, parasympathetic and metasympathetic divisions of the ANS. Each of the areas has its own role. In general, these areas have a role to perform response reactions: increase or decrease thermoregulation, sweating, etc.
The main task of the metasympathetic network is homeostasis, that is, the preservation of the constancy and balance of the internal environment of the body.
Metasympathetic nervous system - what is it?
This part of the nervous system was described for the first time by A. D. Nozdrachev. The term is relatively new - there is no mention of it in many old textbooks. It was noticed that any organ has its own motor skills and rate of activity.
The ganglia of the metasympathetic network are located inside the muscular walls of the organs, as a result of which this system is intraorganic.
The MNS differs in that it innervates only those organs that have autonomous motor activity. It contains personal sensory formations that transmit impulses with information about the state of a particular structure in the body into their neural networks. Such signals come from the MNS and to
CNS, although the former works independently of brain impulses.The location of this structure has its own reflex arcs. But the metasympathetic division of the autonomic nervous system does not come into direct contact with the nerve arches. somatic NS - synaptic outputs are carried out only through the sympathetic and parasympathetic network.
The work of this NS is performed using reflex arcs located in the partitions of hollow organs. The intramural part of all visceral organs is equipped with independent motor activity, which is provided by the MNS.
The areas of this system are named according to the place of their localization: cardiometsympathetic - in the cardiovascular system, entero-sympathetic - in the gastrointestinal tract, and so on.
The enterometasympathetic system can be called the second human brain. It is here that about 45% stand out dopamine and 80% serotonin - more than in the brain. This system of the alimentary tract, even with pathologies of the vagus nerve, continues its activity of digesting food eaten and processing nutrients. This whole process is also regulated by the metasympathetic network.
Functions of the metasympathetic division of the ANS
MNS is a relatively independent department of interconnected neurons that regulates the work of internal organs:
- maintains the absorption capacity of the intestines and intestines;
- regulates the contraction of the heart;
- affects the contractions of the ureter, cervix, etc.;
- innervates, controls the activity of all organs in standard states and with pathologies of the spinal cord;
- provides the constancy of regulation of the functions of organs.
MS affects the activity of the muscle tissue of the heart, smooth muscle structures, and glandular epithelium. Areas or strips of the uterus, urinary, gallbladder contract with the range and amplitude that are characteristic of each organ.
Microganglia of this system are found in the stomach, kidneys, intestines, bronchi and other areas. The structure plays a significant role in organ lesions and disorders. In the event of damage to the spinal nerve canal, many internal organs fail and recover six months later due to the presence of the metasympathetic network.
All reflexes of the system are controlled by vegetative centers. endbrain — stripedas well as the hypothalamus, structure midbrain.
The gastrointestinal tract, brighter than other systems, reflects the main characteristics of the MNS - it is in it that it has been studied to a greater extent. Here she regulates the complex motility of the intestine - peristalsis.
The structure of the gastrointestinal tract includes a variety of formations - muscle tissue, the surface of mucous membranes, endocrine and lymph nodes.
The local MNS regulates all these structures with the participation of other parts of the vegetative system. Thanks to this, the functionality of the gastrointestinal tract is not greatly impaired in the event of malfunctions of the parasympathetic and sympathetic nervous tissues.
Structure and organization
Reflex arc - connected to each other neurons, which carry out the transmission of impulses and receive a response to the excitation of receptors.
The reflex arc of the metasympathetic nervous system closes at the level of the microganglion, which is located in the walls of the hollow organs.
Otherwise, the axon enters the paravertebral or prevertebral ganglia, passing in this area to other neurons, or the axons enter the spinal ganglia and move to other neurons.
Intramural ganglia, located in the thickness of the hollow organs, are the area of localization of the entire MNS. The physiology of the intramural ganglia divides them into sensitive neurons, intercalary and effector. Neurons connect to form reflex arcs through synapses. The impulses travel through synapses with the help of mediators.
The autonomous functional MHC module includes the following types of intramural nerve plexuses:
- Efferent neurons (motor) are located in direct contact with the muscle cell of the organ. The efferent neuron has a huge number of small dendrites, the axons of which end in muscle fibers. This plexus is the endpoint to the effector and is able to excite or inhibit its actions.
- Axons of afferent (sensory) neurons are able to switch to neurons of the previous type or get to the spinal cord, that is, a sensory reaction coming from the microganglia, is able to lock onto various levels. Afferent cells have a nucleus, several large dendrites and axons of various sizes emanate from them.
- Interneurons of the metasympathetic nervous system are located in the ganglia - they perform the function reflex closure from inside the organ, and their axons come to an end on the processes of nerve cells of two previous types. These cells are also called intercalated and have an oval or curved appearance with a long axon and many dendrites. They are not yet fully understood and are rare in the National Assembly.
In addition to these three links, the MHC has its own mediators - these are formations that facilitate the transmission of impulses from one neuron to the next. In this part of the ANS, all mediators that exist in the central nervous system are found.
The central ones are the pituitary peptide and ATP, which are aimed at transmitting the relaxation and tension response. The MHC includes such neurotransmitters: histamine, serotonin, ACh, norepinephrine, dopamine, oligopeptides and gamma-aminobutyric acid.
Each type has its own receptors with neurons. For example, ATP interacts at synapses with purine receptors, which helps to relax the muscles of various organs and systems: the gastrointestinal tract, urinary system, etc. The translation of excitation in neurons is realized by norepinephrine and ACh.
MNS value
The main role of the entire ANS is the preservation and maintenance of homeostasis, that is, the constancy of the functioning of the human body. In medicine, studies of metasympathetic NS are important for the study of various pathologies associated with impaired organ activity.
In the cardiovascular and gastrointestinal systems, an independent MNS is of great physiological importance in stabilizing the dynamics of activity and the coordinated innervation of all organs. The metasympathetic system is an intermediary between other parts of the ANS and the tissues of organs, since it participates in the transmission of impulses emanating from the extraorganic NS.
The presence of "independent" functions of nervous regulation facilitates the central nervous system to process numerous signals coming from internal systems and organs. This doubles the correctness of the regulation of functions.
Due to the reflex arcs of this autonomous structure, the internal organs are able to work without the direct involvement of the central nervous system. Most organs continue to function even after severing the sympathetic and parasympathetic nerve connections or after removing them from the body.
This independence is the result of the presence of the metasympathetic department, which has all the necessary independent links.
An important unit of the entire network is the oscillator cell, which sends its impulses to the motor neuron. This is how it interacts with muscle cells and regulates muscle activity.
Criticism of the conditional allocation of the MNS
Professor Pavel Alexandrovich Motavkin argues in his scientific work (Motavkin P. A. Course of lectures on histology. - "Medicine of the Far East", 2007 - S. 168) critical views in the research world in relation to the theory of the MNS by the fact that in the metasympathetic department the autonomic nervous system includes the intramural ganglia of the digestive and respiratory organs, heart, ureter and others.
This nervous system, according to physiologists, is quite peripheral, independent and not dependent on the functionality of the central nervous system. Its functioning is possible due to autonomous reflexes, which are based on personal neurons of the ANS, which do not interact with central cells.
The pronounced independence of the MNS is real if the presence of motor neurons in the intramural region is supported by evidence, which are not controlled by preganglionic tissues.
To date, 6 types of cells have been found in this area, differing in mediator orientation and morphology. One cannot ignore the potential fact that among these six species there are autonomous effector cells that are independent of the central nervous system.
However, so far the dominant belief in science attaches intramural neurons to the parasympathetic division.
