The term "metasimpathetic nervous system" was introduced by AD Nozdrachev. This is a separate system of interconnected neurons that regulates all the work of internal organs. This is an extremely developed nervous network, which is also subject to the principle of hierarchy of the autonomic ganglia.
The metasympathetic division of the nervous system is an important and integral part of the entire network. The nerve plexuses of the metasympathetic network lie inside the hollow organs, more precisely in their muscular walls. Therefore, the system is sometimes called intraorgan.
The metasympathetic autonomic nervous system has its own structural features and can work separately from brain signals. This became clear in the course of experiments, when the heart continued to contract after perfusion; the excised part of the ureter retained dynamic activity. But how is each module innervated and how is it interconnected with the central nervous system?
Methesympathetic nervous system. What is this?
Until recently, only 2 parts of the nervous system were distinguished - sympathetic and parasympathetic. The first, as you know, is responsible for the mobilization of the body, and the second for relaxation and rest. But when scientists noticed that each organ has its own rhythm of movement and its own separately functioning microganglia, they decided to single out another system - the metasympathetic one.
This is a completely independent formation, which has reflex arcs at its disposal. Each hollow organ has its own ganglionic network: in the kidneys, stomach, uterus, intestines, and in the prostate gland, men also have their own nerve plexuses. Moreover, some networks are still poorly understood, so one can only speculate about how complex they are organized.
The entire autonomic nervous system (sympathetic, parasympathetic, metasympathetic divisions) is designed to control homeostasis, that is, the constancy of the internal environment. If there are no failures in the autonomic nervous system, then the metabolism is perfectly adjusted, the lymphatic system and the circulatory system work properly.
After damage to the spinal central nerve canal, all internal organs, such as the bladder, intestines, are gradually restored after the shock. The organs are rebuilt and again begin to fully work after 5-6 months. This is due to another nervous system, the metasympathetic, embedded in their muscle walls.
Localization
Main lead rhythmcells of the intraorgan system are located in the submucosal membranes and intermuscular structures. The higher autonomic centers, which control all MNS reflexes, are localized in the diencephalon. Namely, in the striatum and hypothalamus.
MNC value
In medicine, the study of ganglion nodes of internal organs is important for the study of diseases associated with impaired development of the organ. One of these abnormalities is Hirschsprung's disease. The MHC is responsible for nourishing the cells of the organ and blood circulation in the internal muscle layers of the organs.
Another important detail. Due to the fact that reflex arcs are present in the intraorgan system, it has the ability to work without the constant "guidance" of the central nervous system. What is a reflex arc? This is a circuit of neurons that allows you to quickly transmit a pain signal and get an immediate response to irritation of the receptors.
Features of the metasympathetic system
What makes WHC stand out in particular? What properties distinguish it from the sympathetic and parasympathetic systems? Scientific evidence has confirmed the assumption that the system:
- It has its own sensory link and afferent pathway.
- Innervates exclusively the muscles of the internal organs.
- Receives signals from the sympathetic and parasympathetic systems via incoming synapses.
- Has no direct connection with the efferent link of the somatic reflex.
- Those internal organs in which the metasympathetic nervous system (MNS) is disturbed losetheir coordinated motor function.
- The network has its own neurotransmitters.
As you can see, the entire nervous system is subject to a hierarchy. "Senior" departments regulate the work of subordinate communications. The organ network is "inferior", but not the simplest.
Vegetative ganglia
Ganglia are nerve nodes. Autonomic ganglia help distribute electrical signals efficiently. One or more preganglionic nerve fibers approach one ganglion, which transmit signals from the "superior" system. And postganglionic neurons depart from the ganglion, transmitting excitation or inhibition further along the network. This universal system allows you to fully control all processes in the body.
In the ganglia of the excitatory nerve network, the presynaptic fiber regulates up to 30 nerve cells connected to the ganglion. And in the parasympathetic - only 3 or 4 neurons.
Vegetative nodes are found in all tissues and organs, as well as in the glands of internal and external secretion. The neurons of the MHC network are extremely diverse, but each consists of an axon, a nucleus, and a dendrite.
Dendrite - from Latin - tree-like. From the name it is clear that this part of the neuron transmits signals along a highly branched network of small fibers. In the enteric system, for example, each neuron has a lot of dendrites.
Some fibers have a myelin sheath, which improves conductivity and speeds up the signal.
Types of MTC
There are several systems. They are divided according to the location of the microganglia:
- cardiometasympathetic system;
- vesiculometasympathetic;
- enterometasympathetic;
- urethrometasimpathetic;
- ganglionic system of the uterus.
It is known that the parasympathetic and sympathetic systems interact with the organ ganglia system and correct their work when necessary. And also many organs have intersecting reflexes. For example, the Goltz reflex.
Metasympathetic nervous system. Physiology
What neurons does this nervous system consist of? What is the structure of the metasympathetic nervous system? Let's take a closer look at the system of neurons. In the structure of the nerve fibers of each hollow organ, there is a rhythm leader that controls motor activity (vibration), there are intercalary, tonic and effector neurons. And of course, there are sensory pads.
The key unit of the entire module is the cell-oscillator, or pacemaker. This cell transmits its signals (action potentials) to the motor neuron. The axon of each motor neuron is in contact with muscle cells.
The function of the cell-oscillator is very significant. Cells are protected from third-party influences, for example, from the influence of ganglionic blockers or neurotransmitters.
Thanks to the work of the network of neurons, the work of the muscles, the absorption of useful substances of the apparatus and the mechanism of blood filling of the organ are controlled.
MHC mediators
Neurotransmitters are substances that help transmit impulses from oneneuron to another. The mediators of the metasympathetic nervous system are:
- histamine;
- serotonin;
- adenosine triphosphoric acid;
- acetylcholine;
- somatostanin;
- catecholamines.
In total, about 20 mediators and modulators in the neural network were found in the laboratory. A mediator such as acetylcholine, which belongs to the group of catecholamines, is a mediator of the sympathetic system, that is, it helps to transmit an excitation signal. An excess of catecholamines in the body leads to overexcitation of the central nervous system. Heart failure often begins due to constant stress and release of norepinephrine. Therefore, the restoring parasympathetic system is urgently needed in the body.
Such mediators as pituitary peptide and ATP are designed to transmit an impulse of relaxation and recovery. Parasympathetic centers are located in the autonomic nuclei of the cranial nerves.
Cardiometasympathetic system
The metasympathetic autonomic nervous system, as mentioned, consists of several divisions. The ganglionic system of the heart is already fairly well understood, so we can look at how it works.
Protection of the heart is due to reflex cycles having a "base" in the intramural ganglia.
Thanks to the work of G. I. Kositsky, we know about one very interesting reflex. Stretching the right atrium is always reflected in the workright stomach. He works harder. The same happens in the left side of the heart.
When the aorta is stretched, the contractility of both ventricles reflexively decreases. These effects are due to the metasympathetic nervous system. The Goltz reflex manifests itself when, upon impact to the abdomen, the heart can stop contracting for a while. The reaction is associated with the activation of the abdominal nerve, with its afferent part.
The heart rate is also reduced by other influences. The Ashner-Dagnini reflex is the reaction of the heart when pressure is applied to the eyes. Cardiac arrest also happens when the vagus nerve is irritated. But with subsequent stimulation of the nerve, this effect disappears.
Cardiac reflexes are designed to maintain blood supply to the arteries at a single constant level. The autonomy of the nervous intracardiac system proves the ability of the heart to take root after transplantation. Although all major cardiac nerves have been severed, the organ continues to contract.
Enterometasympathetic system
The enteric nervous system is a unique mechanism where thousands of neurons are fully coordinated with each other. This mechanism, created by nature, is rightfully considered the second human brain. Since even with damage to the vagus nerve, which is associated with the brain, the system continues to perform all its functions, namely: digestion of food and absorption of nutrients.
But it turns out that the alimentary tract is not only responsible for the digestion of food, but, according to recentdata, and for the emotional background of a person. It has been established that 50% of dopamine, the hormone of joy, and about 80% of serotonin are produced in the intestines. And this is even more than is produced in the brain. Therefore, the intestines can safely be called the emotional brain.
In the enteral autonomic metasympathetic system, several types of neurons are distinguished:
- primary afferent sensory;
- ascending and descending interneurons;
- motor neurons.
Motoneurons, in turn, are divided into moving muscles, excitatory and inhibitory.
Intestinal perist altic reflex and MHC
The small and large intestines also have an autonomous metasympathetic division of the autonomic nervous system. It is known that each villus of the large intestine contains 65 sensory neurons; there are 2,500 different nerve cells per millimeter of tissue.
Sensory neurons are connected to motor neurons through various interneurons in the enteric system. It is enough to activate one neuron, so that the alternating tension and relaxation of the intestinal muscles starts further along the chain. This is called the perist altic reflex, which moves food through the intestines. The vegetative intestinal system is also completely independent of the central nervous system, which is vital if, in the event of a stroke, for example, part of the brain ceases to function.
