Each organ or system in the human body plays a role. However, they are all interconnected. The importance of the nervous system can hardly be overestimated. It is responsible for the correlation between all organs and their systems and for the functioning of the body as a whole. At school, early acquaintance with such a multifaceted concept as the nervous system begins. Grade 4 is still small children who cannot deeply understand many complex scientific concepts.
Structural units
The main structural and functional units of the nervous system (NS) are neurons. They are complex excitable secreting cells with processes and perceive nervous excitation, process it and transmit it to other cells. Neurons can also have a modulating or inhibitory effect on target cells. They are an integral part of the bio- and chemoregulation of the body. From a functional point of view, neurons are one of the foundations of the organization of the nervous system. They combine several other levels (molecular, subcellular, synaptic, supracellular).
Neurons consist of a body (soma), a long process (axon) and small branching processes(dendrites). In different parts of the nervous system, they have a different shape and size. In some of them, the length of the axon can reach 1.5 m. Up to 1000 dendrites depart from one neuron. Through them, excitation spreads from receptors to the cell body. Along the axon, impulses are transmitted to effector cells or other neurons.
In science there is the concept of "synapse". Axons of neurons, approaching other cells, begin to branch and form numerous endings on them. Such places are called synapses. Axons form them not only on nerve cells. Synapses are found on muscle fibers. These organs of the nervous system are present even on the cells of the endocrine glands and blood capillaries. Nerve fibers are glial-covered processes of neurons. They perform a conductive function.
Nerve endings
These are specialized formations located at the tips of the processes of nerve fibers. They provide the transmission of information in the form of an impulse. Nerve endings are involved in the formation of transmitting and receiving end devices of different structural organization. According to the functional purpose, they are distinguished:
• synapses that transmit nerve impulses between nerve cells;
• receptors (afferent endings) that direct information from the site of action of a factor of the internal or external environment;
• effectors that transmit impulses from nerve cells to other tissues.
Activity of the nervous system
The nervous system (NS) is an integral set of several interconnected structures. It contributes to the coordinated regulation of the activity of all organs and provides a response to changing conditions. The human nervous system, the photo of which is presented in the article, links together motor activity, sensitivity and the work of other regulatory systems (immune, endocrine). NA activities are related to:
• anatomical penetration into all organs and tissues;
• establishing and optimizing the relationship between the organism and the environment (environmental, social);
• coordinating all metabolic processes;
• control of organ systems.
Structure
The anatomy of the nervous system is very complex. It contains many structures, different in structure and purpose. The nervous system, the photo of which indicates its penetration into all organs and tissues of the body, plays an important role as a receiver of internal and external stimuli. For this, special sensory structures are designed, which are located in the so-called analyzers. They include special nervous devices that are able to perceive incoming information. These include the following:
• proprioceptors that collect information regarding the state of muscles, fascia, joints, bones;
• exteroreceptors, located in the skin, mucous membranes and sensory organs, capable of perceiving irritating factors received from the external environment;
• interoreceptors located in internal organs and tissues andresponsible for making biochemical changes.
The main meaning of the nervous system
The work of the National Assembly is closely connected with both the surrounding world and the functioning of the organism itself. With its help, the perception of information and its analysis. Thanks to it, stimuli of internal organs and signals coming from outside are recognized. The nervous system is responsible for the body's reactions to the information received. It is thanks to its interaction with the humoral mechanisms of regulation that a person's adaptability to the world around him is ensured.
The importance of the nervous system is to ensure the coordination of individual parts of the body and maintain its homeostasis (balance). Thanks to its work, the organism adapts to any changes, which is called adaptive behavior (state).
Basic NS functions
The functions of the nervous system are quite numerous. The main ones include the following:
• regulation of vital activity of tissues, organs and their systems in normal mode;
• association (integration) of the organism;
• maintaining the relationship of man with the environment;
• control over the state of individual organs and the body as a whole;
• ensuring activation and maintenance of tone (working state);
• identifying people's activities and mental he alth, which are the basis of social life.
The human nervous system, the photo of which is presented above, provides the following thought processes:
•perception, assimilation and processing of information;
• analysis and synthesis;
• the formation of motivation;
• comparison with experience;
• goal setting and planning;
• action correction (error correction);
• performance evaluation;
• formation of judgments, conclusions and conclusions, general (abstract) concepts.
The nervous system, in addition to signaling, also performs a trophic function. Thanks to it, the biologically active substances secreted by the body ensure the vital activity of the innervated organs. Organs that are deprived of such nourishment eventually atrophy and die. The functions of the nervous system are very important for a person. When existing environmental conditions change, they help the body adapt to new circumstances.
Processes taking place in the National Assembly
The human nervous system, the scheme of which is quite simple and understandable, is responsible for the interaction of the organism and the environment. To ensure it, the following processes are carried out:
• transduction, which is the transformation of irritation into nervous excitation;
• transformation, during which the incoming excitation with some characteristics is transformed into an outgoing stream with different properties;
• distribution of excitation in different directions;
• modeling, which is the construction of an image of irritation that replaces its source;
• modulation that changes the nervous system or its activity.
The importance of the human nervous systemalso consists in the interaction of the organism with the external environment. In this case, various responses to any kind of stimuli arise. Main types of modulation:
• excitation (activation), which consists in increasing the activity of the nervous structure (this state is dominant);
• inhibition, depression (inhibition), which consists in reducing the activity of the nervous structure;
• temporary neural connection, which is the creation of new pathways for the transmission of excitation;
• plastic restructuring, which is represented by sensitization (improvement of excitation transmission) and habituation (deterioration of transmission);
• activation of an organ that provides a reflex reaction of the human body.
NA Tasks
Main tasks of the nervous system:
• Reception - capturing changes in the internal or external environment. It is carried out by sensory systems with the help of receptors and is the perception of mechanical, thermal, chemical, electromagnetic and other types of stimuli.
• Transduction - transformation (coding) of the incoming signal into nervous excitation, which is a stream of impulses with characteristics characteristic of irritation.
• The implementation of the conduction, which consists in the delivery of excitation through the nerve pathways to the necessary parts of the NS and to the effectors (executive organs).
• Perception - the creation of a nervous model of irritation (the construction of its sensory image). This process forms a subjective picture of the world.
•Transformation - the transformation of excitation from sensory to effector. Its purpose is to implement the body's response to the environmental change that has occurred. In this case, there is a transfer of descending excitation from the higher parts of the central nervous system to the lower ones or to the PNS (working organs, tissues).
• Evaluation of the result of the NS activity using feedback and afferentation (transmission of sensory information).
NS structure
The human nervous system, the scheme of which is presented above, is divided structurally and functionally. The work of the National Assembly cannot be fully understood without understanding the functions of its main types. Only by studying their purpose, one can realize the complexity of the whole mechanism. The nervous system is subdivided into:
• Central (CNS), which carries out reactions of various levels of complexity, called reflexes. It perceives stimuli received from the external environment and from organs. It includes the brain and spinal cord.
• Peripheral (PNS), connecting the central nervous system with organs and limbs. Its neurons are far from the brain and spinal cord. It is not protected by bones, therefore it is subject to mechanical damage. Only thanks to the normal functioning of the PNS, coordination of human movements is possible. This system is responsible for the body's response to danger and stressful situations. Thanks to her, in such situations, the pulse quickens and the level of adrenaline rises. Diseases of the peripheral nervous system affect the work of the central nervous system.
PNS consists ofbundles of nerve fibers. They go far beyond the spinal cord and brain and go to different organs. They are called nerves. Ganglia (nodes) belong to the PNS. They are clusters of nerve cells.
Diseases of the peripheral nervous system are divided according to the following principles: topographic-anatomical, etiological, pathogenesis, pathomorphology. These include:
• sciatica;
• plexites;
• funiculitis;
• mono-, poly- and multineuritis.
According to the etiology of diseases, they are divided into infectious (microbial, viral), toxic, allergic, dyscirculatory, dysmetabolic, traumatic, hereditary, idiopathic, compression-ischemic, vertebrogenic. PNS diseases can be primary (leprosy, leptospirosis, syphilis) and secondary (after childhood infections, mononucleosis, with periarteritis nodosa). According to pathomorphology and pathogenesis, they are divided into neuropathies (radiculopathy), neuritis (radiculitis) and neuralgia.
Properties of the nervous system
Reflex activity is largely determined by the properties of the nerve centers, which are a collection of structures of the central nervous system. Their coordinated activity ensures the regulation of various body functions or reflex acts. Nerve centers have several common properties determined by the structure and function of synaptic formations (contact between neurons and other tissues):
• One-sidedness of the excitation process. It spreads along a reflex arc in onedirection.
• Irradiation of excitation, which means that with a significant increase in the strength of the stimulus, the area of neurons involved in this process expands.
• Summation of excitation. This process is facilitated by the presence of a huge number of synaptic contacts.
• High fatigue. With prolonged repeated irritation, a weakening of the reflex reaction occurs.
• Synaptic delay. The time of the reflex reaction depends entirely on the speed of movement and the time of propagation of excitation through the synapse. In humans, one such delay is about 1 ms.
• Tone, which is the presence of background activity.
• Plasticity, which is a functional ability to significantly modify the overall picture of reflex reactions.
• Convergence of nerve signals, which determines the physiological mechanism of the pathway of afferent information (constant flow of nerve impulses).
• Integration of cell functions in nerve centers.
• The property of a dominant nerve focus, characterized by increased excitability, the ability to excite and summation.
• Cephalization of the nervous system, which consists in moving, coordinating the body's activity in the main parts of the central nervous system and concentrating the regulation function in them.
