Each organ or system in the human body plays a role. However, they are all interconnected. The value is difficult to overestimate. 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
Main structural and functional units nervous system(NS) - 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 integral part 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 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. are glial-covered processes of neurons. They perform a conductive function.
Nerve endings
These are specialized formations located at the tips of the processes nerve fibers. They provide in the form of momentum. Nerve endings are involved in the formation of transmitting and receiving end devices of different structural organization. By functional purpose allocate:
Synapses, which transmit nerve impulses between nerve cells;
Receptors (afferent endings) that direct information from the site of action of the factor of the internal or external environment;
Effectors that transmit impulses from nerve cells to other tissues.
The 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). The activities of the National Assembly are related to:
Anatomical penetration into all organs and tissues;
Establishment and optimization of the relationship between the organism and the environment (environmental, social);
Coordination of all metabolic processes;
Management 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:
Proprioreceptors that collect information regarding the state of muscles, fascia, joints, bones;
Exteroreceptors located in skin, mucous membranes and sensory organs capable of perceiving irritating factors received from the external environment;
Interoreceptors located in internal organs and tissues and responsible for accepting 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 surrounding world is ensured.
The value 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 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 vital activity of tissues, organs and their systems in normal mode;
Association (integration) of the organism;
Preservation of 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);
Determination of people's activities and their mental health, which are the basis of social life.
The human nervous system, the photo of which is presented above, provides such thought processes:
Perception, assimilation and processing of information;
Analysis and synthesis;
Formation of motivation;
Comparison with existing experience;
Goal setting and planning;
Action correction (error correction);
Evaluation of performance results;
Formation of judgments, conclusions and conclusions, general (abstract) concepts.
The nervous system, in addition to signaling, also performs 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. With changes in existing environmental conditions, with their help, the organism adapts 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 other properties;
Distribution of excitation in different directions;
Modeling, which is the construction of an image of irritation that replaces its source itself;
Modulation that changes the nervous system or its activity.
The value of the human nervous system also lies in the interaction of the organism with the external environment. In this case, various responses to any kind of stimuli arise. The main types of modulation:
Excitation (activation), which consists in increasing the activity of the nervous structure (this state is dominant);
Inhibition, oppression (inhibition), consisting in a decrease in the activity of the nervous structure;
Temporary neural connection, which is the creation of new ways of transmitting excitation;
Plastic restructuring, which is represented by sensitization (improvement in the transfer of excitation) and habituation (deterioration of the transfer);
Activation of an organ that provides a reflex reaction of the human body.
Tasks of the National Assembly
The main tasks of the nervous system:
Reception - capturing changes in the internal or external environment. It is carried out 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 along 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 with the help of feedback and afferentation (transmission of sensory information).
NS structure
The human nervous system, the scheme of which is presented above, is subdivided in structural and functional terms. 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 divided 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 is a person 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 affect the work of the central nervous system.
The PNS is made up of bundles of nerve fibers. They go far beyond the spinal cord and brain and go to different bodies. They are called nerves. The PNS is a collection of nerve cells.
Diseases of the peripheral nervous system are divided according to the following principles: topographic-anatomical, etiological, pathogenesis, pathomorphology. These include:
Radiculitis;
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.
Reflex activity is largely determined by which are a set of structures of the central nervous system. Their coordinated activity ensures the regulation various functions organism 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 propagates 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 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 functionality 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 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 regulatory function in them.
42. Recall the material of the course "Zoology". Determine the types of nervous systems shown in the figure. Write their names. On the image of the human nervous system, label its parts.
43. Study the textbook material and complete the sentences.
The basis of the nervous system is nerve cells- neurons. They perform the functions of receiving, processing, transmitting and storing information. Nerve cells consist of a body, processes and nerve endings - receptors.
44. Write down the definitions.
Dendrites are short processes of neurons (nerve cells).
Axons - long processes of neurons, (nerve cells)
Gray matter is a collection of neuron bodies in the brain and spinal cord.
White matter is an accumulation of processes of neurons in the spinal cord and in the brain.
Receptors are nerve endings of branched processes of neurons.
Synapses are special contacts that are formed by connecting nerve cells to each other.
45. Study the textbook material and complete the "Structure of the nervous system" diagram.
46. Write down the definitions.
Nerves are bundles of long processes of nerve cells that extend beyond the brain and spinal cord.
Nerve nodes are a collection of neuron bodies outside the central nervous system.
47. Study the textbook material and complete the "Structure of the nervous system" diagram.
48. Explain why the autonomic nervous system is called the autonomous system.
It controls the work of internal organs, ensuring their constant work when the external environment changes or the type of activity of the body changes. This system is not controlled by our consciousness.
49. Write down the definitions.
Reflex - responses of the body to the influence of the external environment or to a change in its internal state, performed with the participation of the nervous system.
reflex arc- the path along which the nerve impulse passes from the place of its origin to the working organ.
: ensuring the coordinated work of cells of tissues, organs and systems of the body into a single whole; regulation of the activity of all organs and systems; communication of the organism with the external environment, adaptation to rapidly changing conditions of life; the material basis of human conscious activity: speech, thinking, behavior.
2. nervous tissue consists of neurons and auxiliary cells (glial cells, neuroglia; Schwann cells).
3. Neuron- a nerve cell with processes (one that transmits excitation only from the cell - an axon, and several that transmit excitation to the cell - dendrites).
4. Neurons, connecting with each other with the help of an axon (the longest of all processes), form a neural network.
5. The main departments are the brain and spinal cord; There is also a peripheral nervous system.
6. Gray matter the spinal cord is formed by a cluster of neuron bodies and has the shape of a butterfly; white matter the spinal cord is formed by conducting pathways. Gray matter the brain is formed in exactly the same way and covers the cerebral hemispheres; white matter formed by nerve fibers that connect the cortex of one gyrus with the cortex of other gyrus.
7. somatic nervous system innervates the striated skeletal muscles and sensory organs, providing voluntary motor and sensory functions, connects the body with the environment and quickly reacts to its changes.
8.Autonomic (autonomic) nervous system innervates the smooth muscles of internal organs, blood vessels, skin, heart muscle and glands; controls the activity of internal organs involved in the implementation of the functions of nutrition, respiration, excretion, and adapts their work to the needs of the body and environmental conditions.
9. Under the influence of norepinephrine (this is a neurotransmitter sympathetic nervous system) increases the rhythm and strength of heart contractions; vasoconstriction; dilation of the bronchi and pupil; decreased secretion of the glands of the stomach and intestines, relaxation of the smooth muscles of the intestine; increased salivation. Under the influence acetylcholine(this is the mediator parasympathetic nervous system) the rhythm and force of cardiac contractions decrease; the lumen of the bronchi and pupil narrows; increased pulmonary ventilation and gastrointestinal peristalsis; the secretion of the glands of the stomach, intestines and pancreas increases.
10. Sympathetic and parasympathetic nerves tend to have opposite effects on organ functions. So, for example, sympathetic nerves speed up the rhythm and increase the strength of heart contractions, and parasympathetic (vagus nerve) slow down the rhythm and reduce their strength; etc.
The human nervous system is a collection of interacting structures that are united common functions human body. Interacting structures are represented by neurons and glial cells.
Significance of the nervous system
The main function of the nervous system is to maintain homeostasis. It is she who coordinates and streamlines the functioning of organs by influencing the level of their activity. The activity of the nervous system provides purposeful behavior.
Its main task is to most successfully adapt a person to environment to form a social being out of it. One of the main features of the nervous system is that it links together motor activity, sensitivity and the work of the immune and endocrine systems.
It is the nervous system that provides us with the work of memory, thinking, speech reproduction, the process of thinking and complex behavior.
The structure of the nervous system
It is customary to distinguish between the central nervous system and the peripheral nervous system. But this division is conditional, since its departments function as a single whole.
central nervous system(CNS) is the brain and spinal cord, in which nerve cells and synapses are located, providing contact between them. Networks, circuits and nerve centers are formed in the CNS.
peripheral nervous system(PNS) are nerves extending from the brain and spinal cord, and nerve plexuses and nodes. Nerves are called bundles of nerve fibers covered with connective tissue and extending beyond the spinal cord and brain.
12 pairs of nerves go beyond the brain, 31 pairs - from the spinal cord. Nerves consist of motor and sensory fibers, mixing, they transmit signals from receptors to the brain and give commands to the executive organs.
Clusters of neurons outside the CNS are ganglions. They can receive information, transmit it to the central nervous system, can process signals from the central nervous system and send them to internal organs.
The nervous system is divided into vegetative and somatic - according to functionality.
somatic nervous system
The somatic nervous system is also called the bodily nervous system. It provides the organization of the functions of the skin and skeletal muscles, the control of conscious and volitional movements.
Also, the somatic nervous system provides the perception of stimuli from the outside.
autonomic nervous system
The autonomic nervous system does not depend on the will and consciousness of a person, its functions are autonomous. Its tasks are the regulation of the functions of internal organs, glands, lymphatic and blood vessels and the implementation of metabolism.
STRUCTURE OF THE NERVOUS SYSTEM
Central and peripheral nervous system. The human nervous system consists of central and peripheral parts. The central part includes the brain and spinal cord, the peripheral part includes the nerves and ganglions.
The nervous system is made up of neurons and other cells. nervous tissue. There are sensory, executive and mixed nerves.
Sensory nerves send signals to the central nervous system. They inform the brain about the state internal environment and events taking place in the environment. The executive nerves carry signals from the brain to the organs, controlling their activity. Mixed nerves include both sensory and executive nerve fibers.
The brain is located in the skull. The bodies of neurons in the brain are located in gray matter cortex and nuclei scattered among the white matter of the brain. White matter consists of nerve fibers that connect various centers of the brain and spinal cord.
All parts of the brain perform conduction and reflex functions. In the frontal lobes of the cerebral cortex, the goals of activity are formed and an action program is developed, through the lower parts of the brain its “orders” go to the organs, and through feedback from the organs there are signals about the implementation of these "orders" and their effectiveness.
The spinal cord is located in the spinal canal. At the top, the spinal cord passes into the brain, at the bottom it ends at the level of the second lumbar vertebra, with a bundle of nerves extending from it, resembling a ponytail.
The spinal cord is located in the cerebrospinal fluid. It acts as a tissue fluid, ensuring the constancy of the internal environment, and protects the spinal cord from shocks and concussions.
The neuron bodies of the spinal cord are concentrated in gray columns that occupy the central part of the spinal cord and stretch along the entire spine.
There are ascending nerve pathways, along which nerve impulses go to the brain, and descending nerve pathways, along which excitation goes from the brain to the centers of the spinal cord.
The spinal cord performs reflex and conductive functions.
The connection between the spinal cord and the brain. The centers of the spinal cord work under the control of the brain. The impulses coming from it stimulate the activity of the centers of the spinal cord, maintain their tone. If the connection between the spinal cord and the brain is broken, which happens when the spine is damaged, shock occurs. In shock, all reflexes, the centers of which lie below the damage to the spinal cord, disappear, and voluntary movements become impossible.
Somatic and autonomous (vegetative) departments. Functionally, the nervous system forms two divisions: somatic and autonomous.
Somatic the department regulates human behavior in the external environment, it is associated with the work of skeletal muscles, which are controlled by the desires and will of the person.
Autonomous the department regulates the work of smooth muscles, internal organs, blood vessels. He weakly obeys volitional control and acts according to a program formed as a result of natural selection and fixed by the heredity of the organism.
The autonomous department consists of two sub-departments − sympathetic and parasympathetic, which operate on the principle of complementarity. Thanks to their joint work, the optimal mode of operation of internal organs is established for each specific situation.
FUNCTIONS AND SIGNIFICANCE OF THE NERVOUS SYSTEM
The nervous system ensures the relative constancy of the internal environment of the body.
The metabolism in every organism is carried out continuously. Some substances are consumed and excreted from the body, others come from outside.
The brain, and with it the endocrine glands, automatically maintain a balance between the intake and use of substances, ensuring the fluctuation of vital signs within acceptable limits.
Thanks to the nervous system, homeostasis is maintained in the body, the relative constancy of the internal environment: acid-base balance, the amount of mineral salts, oxygen and carbon dioxide, decay products and nutrients, in the blood - the value of blood pressure and body temperature.
The nervous system coordinates the work of all organs.
The nervous system is responsible for the coordinated activity of various organs and systems, as well as for the regulation of body functions. It determines the order of contraction of muscle groups, the intensity of respiration and cardiac activity, monitors and corrects the results of action. The nervous system is responsible for sensitivity, motor activity and the functioning of the endocrine and immune systems.
Higher nervous activity provides the most perfect adaptation of the organism to the external environment. In humans, it provides the highest mental functions: cognitive, emotional and volitional processes, speech, thinking, consciousness, ability to work and creativity.
Through direct connections there are "orders" of the brain addressed to the organs, and through feedback - signals to the brain from the organs, informing how successfully these "orders" are carried out. The subsequent action will not pass until the previous one has been completed and a positive effect has been achieved.
Parasympathetic innervation (supply of nerves) of all organs and tissues is carried out by branches
The nervous system ensures the survival of the organism as a whole.
To survive, the body needs to receive information about the objects of the external world. Entering into life, a person constantly encounters certain objects, phenomena, situations. Some of them are necessary for him, some are dangerous, others are indifferent.
With the help of the sense organs, the nervous system recognizes objects of the external world, evaluates them, memorizes and processes the information received, aimed at meeting emerging needs.
OUR NERVOUS SYSTEM LIKE:
1. Fresh air.
2. Movement (long walks).
3. Positive emotions(feeling of joy, change of impressions).
4. Long sleep (9-10 hours).
5. Alternation of physical and mental labor.
6. Water procedures.
7. Simple food: Wholemeal bread, cereals (buckwheat, oatmeal), legumes, fish, meat and offal (liver, heart, kidneys), dried porcini mushrooms.
8. Vitamins of group "B" and Nicotinic acid.
OUR NERVOUS SYSTEM DOES NOT LIKE:
1. Stress(arising as a result of prolonged negative emotions, starvation, prolonged exposure to the hot sun).
2. Noise- any annoying.
3. Infections and mechanical damage(diseases of the ears, teeth, squeezing acne, insect bites - ticks, bruised head).