One of the departments of the central nervous system, called the autonomic, consists of several parts. One of them is the sympathetic nervous system. Functional and morphological features allow us to conditionally divide it into several departments. Another division of the autonomic nervous system is the parasympathetic nervous system. In this article, we will consider what a trophic function is.
About the nervous system
In the life of absolutely any living organism, a number of important functions are performed by the nervous system. Therefore, its significance is very great. The nervous system itself is quite complex and includes different departments, has several subspecies. Each of them performs a number of specific functions specific to each of the departments. An interesting fact is that the very concept of the sympathetic nervous system was first used in 1732. At the very beginning, this term was used to refer to the entire autonomic nervous system as a whole. However, with the development of medicine andthe accumulation of scientific knowledge, it became clear that the sympathetic nervous system is fraught with a wider layer of functions. That is why this concept began to be used in relation to only one of the departments of the autonomic nervous system. The trophic function of the nervous system will be presented below.
Sympathetic NS
If we dwell on specific values, it will become clear that the sympathetic nervous system is characterized by quite interesting functions - it is responsible for the process of spending the body's resources, and also mobilizes its internal forces in case of emergency. If the need arises, the sympathetic system significantly increases the expenditure of energy resources in order for the body to continue normal functioning and perform certain tasks. In the case when a conversation arises that the human body has hidden possibilities, this process is implied. The state of a person directly depends on how well the sympathetic system copes with its tasks.
Parasympathetic NS
However, such conditions cause great stress for the body, and in this state it cannot function normally for a long time. Here the parasympathetic system is of great importance, which comes into play and allows you to restore and accumulate the resources of the body, which, in turn, allows you not to limit its capabilities. The sympathetic and parasympathetic nervous systems allow the human body to conduct normallife under various conditions. They are closely related and complement each other. But what does the trophic function of NS mean? More on that later.
Anatomic device
Sympathetic NS has a fairly complex and branched structure. Its central part is located in the spinal cord, and the peripheral part connects various nerve nodes and nerve endings of the body. All nerve endings of the sympathetic system are connected into plexuses and concentrated in innervated tissues.
The peripheral part of the system is formed by a variety of sensitive efferent neurons with specific processes. These processes are distant from the spinal cord and are located mainly in the prevertebral and paravertebral nodes.
Functions of the sympathetic system
As noted, the activation of the sympathetic system occurs when the body enters a stressful situation. Some sources call it the reactive sympathetic nervous system. This name is due to the fact that it implies the occurrence of a certain reaction of the body to external influences. This is its trophic function.
When a stressful situation arises, the adrenal glands immediately begin to secrete adrenaline. It is the main substance that allows a person to respond better and faster in response to stress. A similar situation can occur during physical activity. The release of adrenaline allows you to better cope with it. Adrenaline enhances the actionsympathetic system, which in turn provides resources for increased energy consumption. The secretion of adrenaline itself is not an energy resource, but only contributes to the stimulation of human organs and feelings.
Main function
The main function of the sympathetic NS is the adaptive-trophic function.
Let's consider it in more detail.
Scientists-biologists for quite a long time were convinced that only the somatic nervous system regulates the activity of skeletal-type muscles. This conviction was only shaken at the beginning of the 20th century.
Known fact: long-term work causes muscle fatigue. The strength of the contractions gradually fades, and they may stop altogether. Muscle performance tends to recover after a short rest. For a long time, the reasons for this phenomenon were unknown.
In 1927, Orbeli L. A. experimentally established the following: if you bring the frog's foot to a complete cessation of movement, that is, to fatigue, by prolonged exposure to the motor nerve, and then, without stopping motor stimulation, begin to simultaneously irritate and the nerve of the sympathetic system, the work of the limb will be quickly restored. It turns out that the connection of influence on the sympathetic system changes the functionality of the muscle, which is tired. There is an elimination of fatigue and restoration of its working capacity. This is the trophic function of nerve cells.
Effect on musclefibers
Scientists have found that the nerves of the sympathetic system have a strong influence on muscle fibers, in particular, their ability to conduct electrical currents, as well as the level of excitability of the motor nerve. Under the influence of sympathetic innervation, there is a change in the composition and amount of chemical compounds contained in the muscle and playing an important role in the implementation of its activity. These compounds include lactic acid, glycogen, creatine, phosphates. In accordance with these data, it became possible to conclude that the sympathetic system stimulates the occurrence of certain physicochemical changes in skeletal muscles, has a regulatory effect on the sensitivity of the muscle to emerging motor impulses that come along the fibers of the somatic system. It is the sympathetic system that adapts muscle tissue to perform loads that may arise under various circumstances. There was an opinion that the work of a tired muscle is enhanced by the action of a sympathetic nerve due to increased blood flow. However, the experiments performed did not confirm this opinion. This is how the trophic function of a neuron works.
Through special studies, it was found that there is no direct sympathetic excitability in vertebrate organisms. Thus, the influence of a sympathetic nature on the muscles of the skeletal type is carried out only through the diffusion of the mediator or other substances that are released by the vasomotor terminals of the sympathetic system. Thisthe conclusion can be easily confirmed by a simple experiment. If the muscle is placed in a solution or its vessels are perfused, and then the impact on the sympathetic nerve is started, then an unknown nature of the substance is observed in the solution or in the perfusate. If these substances are injected into other muscles, they cause an effect of a sympathetic nature.
Such a mechanism is also confirmed by a large latent period and its significant duration before the onset of the effect. The appearance of an adaptive-trophic function does not require a long time in those organs that are endowed with direct sympathetic irritability, for example, the heart and other internal organs.
Proofing facts
Facts proving neurotrophic regulation by the sympathetic system have been obtained from various studies on skeletal muscle tissue. Research has included functional overload, denervation, regeneration, and cross-connection of nerves that are connected to different types of muscle fibers. As a result of the research, it was concluded that the trophic function is performed by metabolic processes that maintain the normal muscle structure and provide for its needs during the performance of specific loads. The same metabolic processes contribute to the restoration of the necessary resources after the work of the muscle is stopped. The work of such processes is due to a number of biological regulatory substances. There is evidence that for the occurrence of the action of trophiccharacter, it is necessary to transport the necessary substances from the cell body to the executive organ.
It is also generally accepted that the value of neurotransmitters is not limited to participation in the process of impulse transmission. They also affect the vital activity of excitable organs, participating in the energy supply of tissues.
For example, catecholamines are involved in such a process as the implementation of the trophic function. In the blood, the level of energy substrates increases, which leads to a rapid and intense effect on metabolic processes.
Conclusion
It is known that sensory nerve fibers also exhibit an adaptive-trophic effect. Scientists have found that the endings of sensory fibers contain various kinds of neuroactive substances, such as neuropeptides. The most common are P-neuropeptides, as well as peptides that are associated with the calcitonin gene. Such peptides, after being isolated from nerve endings, are capable of exerting a trophic effect on the tissues surrounding them.
