One of the sections of the central nervous system, called the autonomic, consists of several parts. One of them is the sympathetic nervous system. Functional and morphological characters allow you to conditionally divide it into several departments. Another section of the autonomic NS is the parasympathetic nervous system. In this article, we 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 and the 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. Trophic function of the nervous system will be presented below.
Sympathetic NS
If we dwell on specific values, it will become clear that the rather interesting functions are characteristic of the sympathetic nervous system - it is responsible for the process of expenditure of the body’s resources, and also mobilizes its internal forces in case of emergency. If necessary, the sympathetic system significantly increases the expenditure of energy resources so that the body continues its normal functioning and performs certain tasks. In the case when there is a conversation that the human body has hidden possibilities, this process is implied. The human condition directly depends on how the sympathetic system copes with its tasks.
Parasympathetic NS
However, such conditions cause great stress to the body, and in this state it cannot function for a long time in normal mode. Here the parasympathetic system is of great importance, which comes into play and allows you to restore and accumulate the body's resources, which, in turn, allows you to not limit its capabilities. The sympathetic and parasympathetic nervous systems allow the human body to conduct normal life activity in various conditions. They are closely interconnected and complement each other. But what does the trophic function of NS mean? About it further.
Anatomical device
The sympathetic NS has a rather complex and branched structure. Its central part is located in the spinal cord, while the peripheral part connects a variety of nerve nodes and nerve endings of the body. All endings of the nerves 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.
Sympathetic system functions
As noted, the activation of the sympathetic system occurs when the body enters a stressful situation. Some sources call it reactive sympathetic nervous system. This name is due to the fact that it involves the emergence of a specific reaction of the body to external influences. This is its trophic function.
When a stressful situation occurs, the adrenal glands immediately begin to secrete adrenaline. It is the main substance that allows a person to respond better and faster, responding to stress. A similar situation can occur during exercise. Adrenaline rush allows you to better deal with it. Adrenaline enhances the action of the sympathetic system, and it, 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 senses.
Main function
The main function of the sympathetic NS is the adaptive-trophic function.
Let's consider it in more detail.
For a long time, biologists were convinced that the exclusively somatic nervous system provides regulation of the activity of skeletal muscle type. This conviction was shaken only at the beginning of the 20th century.
Known fact: with prolonged work, muscle fatigue occurs. The force of contractions is gradually dying away, and they can stop altogether. Muscle performance tends to recover after a short rest. For a long time, the causes of this phenomenon were unknown.
In 1927, Orbeli L.A. experimentally established the following: if you bring the frog's paw to the complete cessation of movements, that is, to fatigue, by prolonged exposure to the motor nerve, and then, without stopping motor stimulation, begin to simultaneously irritate the nerve of the sympathetic system, limb function will be quickly restored. It turns out that connecting the influence on the sympathetic system changes the functionality of the muscle, which is tired. The elimination of fatigue and the restoration of its performance. This is the trophic function of nerve cells.
Effect on muscle fibers
Scientists have found that the nerves of the sympathetic system have a strong effect on muscle fibers, in particular, on their ability to conduct electric currents, as well as on the level of excitability of the motor nerve. Under the influence of sympathetic innervation, 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 occurs. Such compounds include lactic acid, glycogen, creatine, phosphates. In accordance with these data, it has become 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 muscles to emerging motor impulses that come through the fibers of the somatic system. It is the sympathetic system that adapts muscle tissue to fulfill the loads that can occur under various circumstances. It was believed that the work of a tired muscle is enhanced by exposure to the sympathetic nerve due to increased blood flow. However, the experiments did not confirm this opinion. This is how the trophic function of the neuron works .
Through special studies, it was found that direct sympathetic excitability in vertebrate organisms is absent. Thus, the influence of a sympathetic nature on skeletal muscle type is carried out only through diffusion of the mediator or other substances that are secreted by the vasomotor terminals of the sympathetic system. This conclusion can be easily confirmed with a simple experiment. If a muscle is placed in a solution or its vessels are perfused, and then the effect on the sympathetic nerve is started, then the unknown nature of the substance is observed in the solution or in the perfusate. If these substances are introduced into other muscles, then they cause an effect of a sympathetic nature.
Such a mechanism is also confirmed by a large latent period and its considerable duration until the occurrence of the effect. For the appearance of adaptive-trophic function, it does not take a long time in those organs that are endowed with direct sympathetic irritability, for example, the heart and other internal organs.
Supporting facts
The facts proving the neurotrophic regulation of the sympathetic system were obtained during various studies on skeletal muscle tissue. The studies 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 support the normal muscle structure and provide its needs during the performance of specific loads. These 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 an action of a trophic nature, transportation of the necessary substances from the cell body to the executive organ is necessary.
The fact that the value of neurotransmitters is not limited only to participation in the transmission of an impulse can also be considered universally recognized. They also affect the vital activity of the excited organs, participating in the energy supply of tissues.
For example, catecholamines take part in such a process as the implementation of trophic function. In the blood, the level of energy substrates increases, which leads to a quick and intense effect on metabolic processes.
Conclusion
Sensitive nerve fibers are also known to exhibit an adaptive trophic effect. Scientists have found that the endings of sensitive fibers contain various kinds of substances of a neuroactive nature, such as neuropeptides. Most often, P-neuropeptides are found, as well as peptides that are associated with the calcitonin gene. Such peptides, after isolation from nerve endings, are capable of exerting trophic influence on the tissues surrounding them.