Each organ or system in the human body plays a role. Moreover, they are all interconnected. The importance of the nervous system is difficult to overestimate. She is responsible for the correlation between all organs and their systems and for the functioning of the organism as a whole. Early in school, they begin familiarization with such a multifaceted concept as the nervous system. Grade 4 - these are 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 exert a modulating or inhibitory effect on target cells. They are an integral part of 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, extracellular).
Neurons consist of a body (catfish), 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 axon length can reach 1.5 m. Up to 1000 dendrites depart from one neuron. Through them, excitation spreads from receptors to the body of the cell. 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. There are synapses on muscle fibers. These organs of the nervous system are even present on the cells of the endocrine glands and blood capillaries. Nerve fibers are glial-coated 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 information in the form of an impulse. Nerve endings are involved in the formation of transmitting and receiving terminal devices of different structural organizations. According to the functional purpose, there are:
• synapses that transmit a nerve impulse between nerve cells;
• receptors (afferent endings), directing information from the place of action of the factor of the internal or external environment;
• effectors that transmit momentum from nerve cells to other tissues.
Nervous system activity
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, combines motor activity, sensitivity and the work of other regulatory systems (immune, endocrine). The activities of the National Assembly are related to:
• anatomical penetration into all organs and tissues;
• establishment and optimization of the relationship between the body and the environment (environmental, social);
• coordination of all metabolic processes;
• management of organ systems.
Structure
The anatomy of the nervous system is very complex. There are many structures in it, 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 purpose, special sensory structures that are located in the so-called analyzers are intended. They include special nerve devices that are capable of perceiving incoming information. These include the following:
• proprioreceptors, collecting information regarding the state of muscles, fascia, joints, bones;
• exteroreceptors located in the skin, mucous membranes and sensory organs, able to perceive irritants received from the external environment;
• interoreceptors located in internal organs and tissues and responsible for the adoption of biochemical changes.
The main importance of the nervous system
The work of the National Assembly is closely connected both with the outside world and with the functioning of the organism itself. With its help there is a perception of information and its analysis. Thanks to it, the recognition of stimuli of internal organs and incoming signals from outside occurs. The nervous system is responsible for the body's response to the information received. It is thanks to its interaction with humoral regulatory mechanisms that ensures the adaptability of a person to the world around him.
The importance of the nervous system is to ensure the coordination of individual parts of the body and maintain its homeostasis (equilibrium state). Thanks to her work, the body adapts to any changes, called adaptive behavior (state).
Basic functions of the National Assembly
The functions of the nervous system are quite numerous. The main ones include the following:
• regulation of the vital functions of tissues, organs and their systems in normal mode;
• association (integration) of the body;
• maintaining the relationship of man with the environment;
• control over the state of individual organs and the body as a whole;
• ensuring the activation and maintenance of tone (working condition);
• determination of the activities of people and their mental health, which are the basis of social life.
The human nervous system, the photo of which is presented above, provides the following mental processes:
• perception, assimilation and processing of information;
• analysis and synthesis;
• formation of motivation;
• comparison with existing experience;
• goal setting and planning;
• correction of action (correction of errors);
• assessment of performance;
• formation of judgments, conclusions and conclusions, general (abstract) concepts.
The nervous system, in addition to the signal system, also has a trophic function. Thanks to it, biologically active substances secreted by the body ensure the vital activity of innervated organs. Organs that are deprived of such nourishment will atrophy and die over time. The functions of the nervous system are very important for a person. With changes in existing environmental conditions with their help, the body adapts to new circumstances.
Processes in the National Assembly
The human nervous system, the scheme of which is quite simple and clear, is responsible for the interaction of the body and the environment. To ensure this, the following processes are carried out:
• transduction, which is the transformation of irritation into nervous excitement;
• transformation, during which there is a conversion of the input excitation with some characteristics into the output stream with other 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 value of the human nervous system also consists in the interaction of the body with the environment. In this case, various responses to any types of stimuli arise. The main types of modulation:
• excitation (activation), which consists in increasing the activity of the nervous structure (this condition is dominant);
• inhibition, inhibition (inhibition), consisting in a decrease in the activity of the nervous structure;
• temporary nervous connection, which is the creation of new ways of transmission of excitation;
• plastic reconstruction, which is represented by sensitization (improving transmission of excitation) and habituation (transmission degradation);
• activation of the organ providing the reflex reaction of the human body.
Tasks of the National Assembly
The main tasks of the nervous system:
• Reception - capture changes in the internal or external environment. It is carried out by sensory systems using receptors and represents the perception of mechanical, thermal, chemical, electromagnetic and other types of stimuli.
• Transduction - the conversion (coding) of an incoming signal into a nervous excitation, which is a stream of impulses with characteristics characteristic of irritation.
• Implementation, consisting in the delivery of excitation through the nerve paths to the necessary sections of the National Assembly and to the effectors (executive bodies).
• 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 the implementation of the response of the body to the change in the environment. In this case, the downward excitation is transmitted from the higher parts of the central nervous system to the lower ones or to the PNS (working organs, tissues).
• Assessment of the result of the activities of the National Assembly using feedbacks and afferentations (transmission of sensory information).
NS structure
The human nervous system, the scheme of which is presented above, is subdivided in structural and functional terms. It is impossible to fully understand the work of the National Assembly without understanding the functions of its main types. Only by studying their purpose, you can realize the complexity of the whole mechanism. The nervous system is divided into:
• Central (CNS), which carries out reactions of various levels of complexity, called reflexes. She perceives stimuli obtained from the external environment and from organs. The brain and spinal cord are referred to it.
• 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 due to the normal functioning of the PNS is it possible to coordinate human movements . 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 central nervous system .
PNS consists of bundles of nerve fibers. They go far beyond the spinal cord and brain and go to different organs. They are called nerves. PNS include ganglia (nodes). They are an accumulation of nerve cells.
Diseases of the peripheral nervous system are divided according to the following principles: topographic-anatomical, etiological, pathogenesis, pathomorphology. These include:
• sciatica;
• plexitis;
• funiculars;
• mono-, poly- and multineuritis.
According to the etiology of diseases, they are divided into infectious (microbial, viral), toxic, allergic, discirculatory, 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 neuropathy (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 combination of CNS structures. Their coordinated activity provides 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-way excitation process. It spreads along a reflex arc in one direction.
• Irradiation of excitation, which consists in the fact that with a significant increase in the strength of the stimulus, the area of neurons involved in this process expands.
• Summation of excitement. 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 completely depends on the speed of movement and the propagation time of the 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 path of passage of afferent information (a constant stream 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 summarize.
• Cephalization of the nervous system, which consists in moving, coordinating the activity of the body in the main sections of the central nervous system and concentrating regulation functions in them.