What is the significance of the human nervous system. The importance of the nervous system for the body

42. Remember the material from the “Zoology” course. Identify 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 made up of 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 are long processes of neurons (nerve cells)
Gray matter is a collection of neuron cell bodies in the brain and spinal cord.
White matter is a collection of neuron processes in the spinal cord and brain.
Receptors are the nerve endings of the 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 diagram “Structure of the nervous system.”

46. ​​Write down the definitions.
Nerves are bundles of long processes of nerve cells that extend beyond the brain and spinal cord.
Nerve ganglia are collections of neuron cell bodies outside the central nervous system.

47. Study the textbook material and complete the diagram “Structure of the nervous system.”

48. Explain why the autonomic nervous system is called the autonomic system.
She manages the work internal organs, ensuring their constant operation when the external environment changes or the type of activity of the organism changes. This system is not controlled by our consciousness.

49. Write down the definitions.
Reflex - the body's response to the influence of the external environment or to changes in it internal state performed with the participation of the nervous system.
Reflex arc- the path along which a nerve impulse passes from the place of its origin to the working organ.

The importance of the nervous system in the human body is enormous. After all, it is responsible for the relationship between each organ, organ systems and functioning human body. The activity of the nervous system is determined by the following:

1. Establishing and establishing relationships between the outside world (social and ecological environment) and the body.
2. Anatomical penetration into every organ and tissue.
3. Coordinating every metabolic process occurring inside the body.
4. Managing the activities of apparatuses and organ systems, combining them into one whole.

The importance of the human nervous system

In order to perceive internal and external stimuli, the nervous system has sensory structures located in the analyzers. These structures will include certain devices capable of receiving information:

1. Proprioceptors. They collect all information regarding the condition of muscles, bones, fascia, joints, and the presence of fiber.
2. Exteroceptors. They are located in human skin, sensory organs, and mucous membranes. Capable of perceiving irritating factors, obtained from the surrounding external environment.
3. Interoreceptors. Located in tissues and internal organs. Responsible for the perception of biochemical changes received from the external environment.

Basic meaning and functions of the nervous system

It is important to note that with the help of the nervous system perception and analysis of information about stimuli from outside world and internal organs. She is also responsible for responses to these irritations.

The human body, the subtlety of its adaptation to changes in the surrounding world, is accomplished primarily through the interaction of humoral and nervous mechanisms.

The main functions include:

1. Determination of a person’s mental health and activities, which are the basis of his social life.
2. Regulation of the normal functioning of organs, their systems, tissues.
3. Integration of the body, its unification into a single whole.
4. Maintaining the relationship between the whole body and environment. If environmental conditions change, the nervous system adapts to these conditions.

In order to accurately understand the importance of the nervous system, it is necessary to delve into the meaning and main functions of the central and peripheral nervous systems.

The importance of the central nervous system

It is the main part of the nervous system of both humans and animals. Its main function is the implementation of various levels of complexity of reactions called reflexes.

Thanks to the activity of the central nervous system, the brain is able to consciously reflect changes in the external conscious world. Its meaning is that it regulates various kinds reflexes, capable of perceiving stimuli received both from internal organs and from the external world.

The importance of the peripheral nervous system

The PNS connects the central nervous system to the limbs and organs. Its neurons are located far beyond the central nervous system - the spinal cord and brain.

It is not protected by bones, which can lead to mechanical damage or harmful actions toxins.

Thanks to the proper functioning of the PNS, the body's movements are coordinated. This system is responsible for conscious control of the actions of the entire organism. Responsible for responding to stressful situations and danger. Increases heart rate. In case of excitement, it increases the level of adrenaline.

It is important to remember that you should always take care of your health. After all, when a person leads healthy image life, adheres to the correct daily routine, he does not burden his body in any way and thereby remains healthy.

Nervous system

Nervous system- an integral morphological and functional set of various interconnected nervous structures, which, together with the endocrine system, ensures the interconnected regulation of the activity of all body systems and the response to changing conditions of the internal and external environment. The nervous system acts as an integrative system, linking sensitivity, motor activity and the work of others into one whole. regulatory systems(endocrine and immune).

General characteristics of the nervous system

All the variety of meanings of the nervous system follows from its properties.

1. Excitability, irritability and conductivity are characterized as functions of time, that is, it is a process that occurs from irritation to the manifestation of the response activity of the organ. According to electrical theory propagation of a nerve impulse in a nerve fiber, it spreads due to the transition of local foci of excitation to neighboring inactive areas of the nerve fiber or the process of spreading depolarization of the action potential, which is similar to an electric current. Another flows through the synapses - chemical process, in which the development of an excitation-polarization wave belongs to the mediator acetylcholine, that is, a chemical reaction.
2. The nervous system has the property of transforming and generating energies of external and internal environment and transforming them into a nervous process.
3. To especially important property The nervous system refers to the property of the brain to store information in the process of not only onto-, but also phylogenesis.

Neurons

The nervous system consists of neurons, or nerve cells, and neuroglia, or neuroglial (or glial) cells. Neurons- these are the main structural and functional elements in both the central and peripheral nervous systems. Neurons are excitable cells, meaning they are capable of generating and transmitting electrical impulses (action potentials). Neurons have different shape and sizes, they form processes of two types: axons And dendrites. There may be many dendrites, several, one, or none at all. Typically, a neuron has several short branched dendrites, along which impulses travel to the neuron body, and always one long axon, along which impulses travel from the neuron body to other cells (neurons, muscle or glandular cells). Neurons, according to the shape and nature of the processes from them, are: unipolar (single-process), biopolar (two-process), pseudounipolar (false-process) and multipolar (multi-process). The sizes of neurons are: small (up to 5 microns), medium (up to 30 microns) and large (up to 100 microns). The length of the processes of neurons is different: for example, in some the length of the processes is microscopic, and in others up to 1.5 m. For example, a neuron is located in the spinal cord, and its processes end in the fingers or toes. The transmission of a nerve impulse (excitation), as well as the regulation of its intensity, from one neuron to other cells occurs through specialized contacts - synapses.

Neuroglia

Glial cells are more numerous than neurons and make up at least half the volume of the central nervous system, but unlike neurons they cannot generate action potentials. Neuroglial cells are different in structure and origin; they perform auxiliary functions in the nervous system, providing support, trophic, secretory, delimitation and protective functions.

Comparative neuroanatomy

Types of nervous systems

There are several types of organization of the nervous system, represented in various systematic groups of animals.

• Diffuse nervous system - presented in coelenterates. Nerve cells form a diffuse nerve plexus in the ectoderm throughout the animal's body, and when one part of the plexus is strongly stimulated, a generalized response occurs - the whole body reacts.
• Stem nervous system (orthogon) - some nerve cells are collected into nerve trunks, along with which the diffuse subcutaneous plexus is preserved. This type of nervous system is represented in flatworms and nematodes (in the latter the diffuse plexus is greatly reduced), as well as many other groups of protostomes - for example, gastrotrichs and cephalopods.
• The nodal nervous system, or complex ganglion system, is represented in annelids, arthropods, mollusks and other groups of invertebrates. Most of the cells of the central nervous system are collected in nerve nodes - ganglia. In many animals, the cells in them are specialized and serve individual organs. In some molluscs (for example, cephalopods) and arthropods, a complex association of specialized ganglia with developed connections between them arises - a single brain or cephalothoracic nerve mass (in spiders). In insects, some sections of the protocerebrum (“mushroom bodies”) have a particularly complex structure.
• A tubular nervous system (neural tube) is characteristic of chordates.

Nervous system of various animals

Nervous system of cnidarians and ctenophores

Cnidarians are considered the most primitive animals that have a nervous system. In polyps it represents a primitive subepithelial nervous network ( nervous plexus), entwining the entire body of the animal and consisting of neurons of different types (sensitive and ganglion cells), connected to each other by processes ( diffuse nervous system), their especially dense plexuses are formed on the oral and aboral poles of the body. Irritation causes rapid conduction of excitation through the body of the hydra and leads to contraction of the entire body, due to the contraction of epithelial-muscular cells of the ectoderm and at the same time their relaxation in the endoderm. Jellyfish are more complex than polyps; a central section begins to separate in their nervous system. In addition to the subcutaneous nerve plexus, they have ganglia along the edge of the umbrella, connected by processes of nerve cells in nerve ring, from which the muscle fibers of the velum are innervated and Rhopalia- structures containing various sensory organs ( diffuse nodular nervous system). Greater centralization is observed in scyphojellyfish and especially box jellyfish. Their 8 ganglia, corresponding to 8 rhopalia, reach quite large sizes.

The nervous system of ctenophores includes a subepithelial nerve plexus with condensations along rows of paddle plates that converge to the base of a complex aboral sensory organ. In some ctenophores, nearby nerve ganglia have been described.

Nervous system of protostomes

Flatworms have already been divided into central and peripheral section s the nervous system. In general, the nervous system resembles a regular lattice - this type of structure was called orthogonal. It consists of a medullary ganglion, which in many groups surrounds the statocysts (endon medulla), which is connected to nerve trunks orthogon running along the body and connected by ring transverse bridges ( commissures). Nerve trunks consist of nerve fibers extending from nerve cells scattered along their course. In some groups, the nervous system is quite primitive and close to diffuse. Among flatworms, the following trends are observed: the ordering of the subcutaneous plexus with the separation of trunks and commissures, an increase in the size of the cerebral ganglion, which turns into central office control, immersion of the nervous system into the thickness of the body; and, finally, a decrease in the number of nerve trunks (in some groups only two remain abdominal (lateral) trunk).

In nemerteans central part nervous system is represented by a pair of connected double ganglia located above and below the proboscis vagina, connected by commissures and reaching significant size. Nerve trunks go back from the ganglia, usually in pairs, and they are located on the sides of the body. They are also connected by commissures; they are located in the skin-muscle sac or in the parenchyma. Numerous nerves depart from the head node, the most strongly developed are the spinal nerve (often double), abdominal and pharyngeal.

Gastrociliary worms have a suprapharyngeal ganglion, a peripharyngeal nerve ring, and two superficial lateral longitudinal trunks connected by commissures.

Nematodes have a peripharyngeal nerve ring, from which 6 nerve trunks extend forward and backward, the largest - the ventral and dorsal trunks - stretch along the corresponding hypodermal ridges. The nerve trunks are connected to each other by semicircular jumpers; they innervate the muscles of the abdominal and dorsal lateral bands, respectively. Nematode nervous system Caenorhabditis elegans has been mapped at the cellular level. Each neuron has been recorded, its origin has been traced, and most, if not all, neural connections are known. In this species, the nervous system is sexually dimorphic: the male and hermaphroditic nervous systems have different numbers of neurons and groups of neurons to perform sex-specific functions.

In Kinorhynchus, the nervous system consists of a peripharyngeal nerve ring and a ventral (abdominal) trunk, on which, in accordance with their inherent body segmentation, ganglion cells are located in groups.

The nervous system of hairworms and priapulids has a similar structure, but their ventral nerve trunk is devoid of thickenings.

Rotifers have a large suprapharyngeal ganglion, from which nerves arise, especially large ones - two nerves running through the entire body on the sides of the intestine. Smaller ganglia lie in the leg (pedal ganglion) and next to the masticatory stomach (mastax ganglion).

In acanthocephalans, the nervous system is very simple: inside the proboscis vagina there is an unpaired ganglion, from which thin branches extend forward to the proboscis and two thicker lateral trunks back; they emerge from the proboscis vagina, cross the body cavity, and then go back along its walls.

Annelids have a paired suprapharyngeal ganglion, peripharyngeal connectives(connectives, unlike commissures, connect opposite ganglia) connected to the ventral part of the nervous system. In primitive polychaetes, it consists of two longitudinal nerve cords in which nerve cells are located. In more highly organized forms they form paired ganglia in each body segment ( neural staircase), and the nerve trunks come closer together. In most polychaetes, paired ganglia merge ( ventral nerve cord), in some cases their connectives also merge. Numerous nerves depart from the ganglia to the organs of their segment. In the series of polychaetes, the nervous system is immersed from under the epithelium into the thickness of the muscles or even under the skin-muscular sac. Ganglia of different segments can be concentrated if their segments merge. Similar trends are observed in oligochaetes. In leeches, the nerve chain lying in the abdominal lacunar canal consists of 20 or more ganglia, and the first 4 ganglia are combined into one ( subpharyngeal ganglion) and the last 7.

In echiurids, the nervous system is poorly developed - the peripharyngeal nerve ring is connected to the abdominal trunk, but the nerve cells are scattered evenly throughout them and do not form nodes anywhere.

Sipunculids have a suprapharyngeal nerve ganglion, a peripharyngeal nerve ring and an abdominal trunk devoid of nerve ganglia, lying on the inside of the body cavity.

Tardigrades have a suprapharyngeal ganglion, peripharyngeal connectives, and a ventral chain with 5 paired ganglia.

Onychophorans have a primitive nervous system. The brain consists of three sections: the protocerebrum innervates the eyes, the deutocerebrum innervates the antennae, and the tritocerebrum innervates the foregut. Nerves extend from the peripharyngeal connectives to the jaws and oral papillae, and the connectives themselves pass into distant abdominal trunks, evenly covered with nerve cells and connected by thin commissures.

Nervous system of arthropods

In arthropods, the nervous system is composed of a paired suprapharyngeal ganglion, consisting of several connected nerve ganglia (brain), peripharyngeal connectives and a ventral nerve cord, consisting of two parallel trunks. In most groups, the brain is divided into three sections - proto-, dayto- And tritocerebrum. Each body segment has a pair of nerve ganglia, but the fusion of ganglia to form large nerve centers is often observed; for example, the subpharyngeal ganglion consists of several pairs of fused ganglia - it controls the salivary glands and some muscles of the esophagus.

In a number of crustaceans, in general, the same trends are observed as in annelids: the convergence of a pair of abdominal nerve trunks, the fusion of paired nodes of one body segment (that is, the formation of the abdominal nerve chain), the fusion of its nodes in the longitudinal direction as the body segments unite. Thus, crabs have only two nerve masses - the brain and a nerve mass in the chest, and in copepods and barnacles a single compact formation is formed, penetrated by a canal digestive system. The brain of crayfish consists of paired lobes - the protocerebrum, from which the optic nerves, which have ganglion clusters of nerve cells, depart, and the deutocerebrum, which innervates antennae I. Usually, a tritocerebrum is also added, formed by the fused nodes of the antennal segment II, the nerves to which usually arise from the peripharyngeal connectives. Crustaceans have a developed sympathetic nervous system, consisting of the medulla and unpaired sympathetic nerve, which has several ganglia and innervates the intestine. Play an important role in the physiology of crayfish neurosecretory cells, located in various parts of the nervous system and secreting neurohormones.

The brain of centipedes has a complex structure, most likely formed by many ganglia. The subpharyngeal ganglion innervates all oral limbs; from it begins a long paired longitudinal nerve trunk, on which there is one paired ganglion in each segment (in bipedal centipedes, in each segment, starting from the fifth, there are two pairs of ganglia located one after the other).

The insect nervous system, also consisting of the brain and the ventral nerve cord, can achieve significant development and specialization individual elements. The brain consists of three typical sections, each of which consists of several ganglia separated by layers of nerve fibers. An important associative center is "mushroom bodies" protocerebrum. Social insects (ants, bees, termites) have especially developed brains. The ventral nerve cord consists of the subpharyngeal ganglion, which innervates the oral limbs, three large thoracic nodes and abdominal nodes (no more than 11). In most species, more than 8 ganglia are not found in adulthood; in many, these also merge, giving rise to large ganglion masses. It can go so far as to form only one ganglion mass in the thorax, innervating both the thorax and the abdomen of the insect (for example, in some flies). During ontogenesis, ganglia often unite. Sympathetic nerves arise from the brain. Almost all parts of the nervous system contain neurosecretory cells.

In horseshoe crabs, the brain is not externally divided, but has a complex histological structure. Thickened peripharyngeal connectives innervate the chelicerae, all limbs of the cephalothorax and gill covers. The abdominal nerve cord consists of 6 ganglia, the posterior one is formed by the fusion of several. The nerves of the abdominal limbs are connected by longitudinal lateral trunks.

The nervous system of arachnids has a clear tendency to concentrate. The brain consists only of the protocerebrum and tritocerebrum due to the lack of structures that the deutocerebrum innervates. The metamerism of the abdominal nerve chain is most clearly preserved in scorpions - they have a large ganglion mass in the chest and 7 ganglia in the abdomen, in salpugs there is only 1, and in spiders all the ganglia have merged into the cephalothoracic nerve mass; in harvestmen and ticks there is no distinction between it and the brain.

Sea spiders, like all chelicerates, do not have a deuterocerebrum. Abdominal nerve cord different types contains from 4-5 ganglia to one continuous ganglionic mass.

Nervous system of mollusks

In primitive chiton mollusks, the nervous system consists of a peripharyngeal ring (innervates the head) and 4 longitudinal trunks - two pedal(innervate the leg, which are connected in no particular order by numerous commissures, and two pleurovisceral, which are located outward and above the pedal ones (innervate the visceral sac and connect above the powder). The pedal and pleurovisceral trunks on one side are also connected by many jumpers.

The nervous system of monoplacophorans is structured similarly, but their pedal trunks are connected by only one bridge.

In more developed forms, as a result of the concentration of nerve cells, several pairs of ganglia are formed, which are shifted to the anterior end of the body, with the suprapharyngeal node (brain) receiving the greatest development.

Nervous system of deuterostomes

Vertebrate nervous system

The nervous system of vertebrates is often divided into the central nervous system (CNS) and the peripheral nervous system (PNS). The central nervous system consists of the brain and spinal cord. The PNS is made up of other nerves and neurons that do not lie within the CNS. The vast majority of nerves (which are actually the axons of neurons) belong to the PNS. The peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system.

The somatic nervous system is responsible for coordinating body movement and receiving and transmitting external stimuli. This system regulates actions that are under conscious control.

The autonomic nervous system is divided into parasympathetic and sympathetic. The sympathetic nervous system responds to danger or stress, and, among many physiological changes, can cause an increase in heart rate and blood pressure and arousal of the senses due to an increase in adrenaline in the blood. The parasympathetic nervous system, on the other hand, is responsible for the state of rest, and ensures that the pupil contracts, slows the heart, dilates blood vessels and stimulates the digestive and genitourinary systems.

Mammalian nervous system

The nervous system functions as an integral unit with sensory organs, such as the eyes, and is controlled in mammals by the brain. The largest part of the latter is called the cerebral hemispheres (in the occipital region of the skull there are two smaller hemispheres of the cerebellum). The brain connects to the spinal cord. In all mammals, with the exception of monotremes and marsupials, unlike other vertebrates, the right and left cerebral hemispheres are connected to each other by a compact bundle of nerve fibers called the corpus callosum. In the brains of monotremes and marsupials there is no corpus callosum, but the corresponding areas of the hemispheres are also connected by nerve bundles; for example, the anterior commissure connects the right and left olfactory areas with each other. The spinal cord, the main nerve trunk of the body, passes through a canal formed by the foramina of the vertebrae and extends from the brain to the lumbar or sacral spine, depending on the species of animal. On each side of the spinal cord, nerves extend symmetrically to various parts bodies. The sense of touch is, in general terms, provided by certain nerve fibers, countless endings of which are located in the skin. This system is usually supplemented by hairs that act as levers to press on areas riddled with nerves.

Morphological division

The nervous system of mammals and humans is divided according to morphological characteristics into central (brain and spinal cord) and peripheral (composed of nerves extending from the brain and spinal cord).

The composition of the central nervous system can be represented as follows:

The peripheral nervous system includes cranial nerves, spinal nerves and nerve plexuses

Functional division

• Somatic (animal) nervous system
• Autonomic (autonomic) nervous system
  • Sympathetic division of the autonomic nervous system
  • Parasympathetic division of the autonomic nervous system
  • Metasympathetic division of the autonomic nervous system (enteric nervous system)

Ontogenesis

Models

IN present moment No uniform provision on the development of the nervous system in ontogenesis. The main problem is to assess the level of determinism (predetermination) in the development of tissues from germ cells. The most promising models are mosaic model And regulatory model. Neither one nor the other can fully explain the development of the nervous system.

• The mosaic model assumes complete determination of the fate of an individual cell throughout ontogeny.
• The regulatory model assumes the random and variable development of individual cells, with only the neural direction being deterministic (that is, any cell of a certain group of cells can become anything within the scope of development for this group of cells).

For invertebrates, the mosaic model is almost flawless - the degree of determination of their blastomeres is very high. But for vertebrates everything is much more complicated. A certain role of determination here is undoubted. Already at the sixteen-cell stage of development of the vertebrate blastula, it is possible to say with a fair degree of certainty which blastomere is not the predecessor of a certain organ.

Marcus Jacobson introduced a clonal model of brain development (close to regulatory) in 1985. He suggested that the fate of individual groups of cells representing the progeny of an individual blastomere, that is, “clones” of this blastomere, is determined. Moody and Takasaki (independently) developed this model in 1987. A map of the 32-cell blastula stage was constructed. For example, it has been established that descendants of the D2 blastomere (vegetative pole) are always found in the medulla oblongata. On the other hand, the descendants of almost all blastomeres of the animal pole do not have pronounced determination. In different organisms of the same species, they may or may not occur in certain parts of the brain.

Regulatory Mechanisms

It was found that the development of each blastomere depends on the presence and concentration of specific substances - paracrine factors, which are secreted by other blastomeres. For example, in experience in vitro with the apical part of the blastula, it turned out that in the absence of activin (paracrine factor of the vegetative pole), the cells develop into ordinary epidermis, and in its presence, depending on the concentration, in increasing order: mesenchymal cells, smooth muscle cells, notochord cells or cardiac muscle cells.

All substances that determine the behavior and fate of the cells that perceive them, depending on the dose (concentration) of the substance in a given area of ​​the multicellular embryo, are called morphogens.

Some cells secrete soluble active molecules (morphogens) into the extracellular space, decreasing from their source along a concentration gradient.

That group of cells whose location and purpose is specified within the same boundaries (with the help of morphogens) is called morphogenetic field. The fate of the morphogenetic field itself is strictly determined. Each specific morphogenetic field is responsible for the formation of a specific organ, even if this group of cells is transplanted into different parts of the embryo. The fates of individual cells within the field are not so rigidly fixed, so they can within known limits change the purpose, replenishing the functions of cells lost by the field. The concept of the morphogenetic field is more general concept, in relation to the nervous system it corresponds to the regulatory model.

The concept of embryonic induction is closely related to the concepts of morphogen and morphogenetic field. This phenomenon, also common to all body systems, was first shown in the development of the neural tube.

Development of the vertebrate nervous system

The nervous system is formed from the ectoderm, the outermost of the three germ layers. A paracrine interaction begins between the cells of the mesoderm and ectoderm, that is, a special substance is produced in the mesoderm - neuronal growth factor, which is transferred to the ectoderm. Under the influence of neuronal growth factor, part of the ectodermal cells turns into neuroepithelial cells, and the formation of neuroepithelial cells occurs very quickly - at a rate of 250,000 pieces per minute. This process is called neuronal induction ( special case embryonic induction).

As a result, a neural plate is formed, which consists of identical cells. From it the neural folds are formed, and from them - the neural tube, which is separated from the ectoderm (it is the change in the types of cadherins, cell adhesion molecules, that is responsible for the formation of the neural tube and neural crest), going under it. The mechanism of neurulation differs somewhat between lower and higher vertebrates. The neural tube does not close along its entire length simultaneously. First of all, the closure occurs in the middle part, then this process spreads to its rear and front ends. At the ends of the tube, two open sections remain - the anterior and posterior neuropores.

Then the process of differentiation of neuroepithelial cells into neuroblasts and glioblasts occurs. Glioblasts give rise to astrocytes, oligodendrocytes and epindymal cells. Neuroblasts become neurons. Next, the migration process occurs - neurons move to where they will perform their function. Due to the growth cone, the neuron crawls like an amoeba, and the processes of glial cells indicate its path. The next stage is aggregation (sticking together of neurons of the same type, for example, those involved in the formation of the cerebellum, thalamus, etc.). Neurons recognize each other thanks to surface ligands - special molecules found on their membranes. Having united, the neurons are arranged in the order necessary for a given structure.

After this, the nervous system matures. An axon grows from the growth cone of the neuron, and dendrites grow from the body.

Then fasciculation occurs - the union of similar axons (formation of nerves).

The last stage is the programmed death of those nerve cells in which a malfunction occurred during the formation of the nervous system (about 8% of cells send their axon to the wrong place).

Neuroscience

Modern science of the nervous system combines many scientific disciplines: along with classical neuroanatomy, neurology and neurophysiology, molecular biology and genetics, chemistry, cybernetics and a number of other sciences make an important contribution to the study of the nervous system. This interdisciplinary approach to the study of the nervous system is reflected in the term neuroscience. In Russian-language scientific literature The term "neurobiology" is often used synonymously. One of the main goals of neuroscience is to understand the processes occurring both at the level of individual neurons and neural networks, the result of which are various mental processes: thinking, emotions, consciousness. In accordance with this task, the study of the nervous system is carried out on different levels organizations, from the molecular to the study of consciousness, creativity and social behavior.

Professional societies and magazines

Society for Neuroscience (SfN, the Society for Neuroscience) is the largest non-profit international organization, uniting more than 38 thousand scientists and doctors studying the brain and nervous system. The society was founded in 1969 and is headquartered in Washington. Its main goal is the exchange of scientific information between scientists. To this end, an international conference is held annually in various cities in the United States and the Journal of Neuroscience is published. The society carries out educational and educational work.

The Federation of European Neuroscience Societies (FENS, the Federation of European Neuroscience Societies) brings together a large number of professional societies from European countries, including Russia. The Federation was founded in 1998 and is a partner of the American Society for Neuroscience (SfN). The Federation is holding an international conference in different European cities every 2 years and publishes the European Journal of Neuroscience.

• American Harriet Cole (1853-1888) died at the age of 35 from tuberculosis and bequeathed her body to science. Then pathologist Rufus B. Weaver of medical college Hanemann in Philadelphia spent 5 months carefully removing, distributing and securing Harriet's nerves. He even managed to preserve his eyeballs, which remained attached to the optic nerves.

• Visceral nervous system
• Nervous tissue
• Endocrine system
• Immune system
• Peripharyngeal nerve ring
• Ventral nerve cord

Rozdil II . Topic 1. Nervous system.

Significance of the nervous system

Classification of the nervous system

The main stages of development of the nervous system

Nerve tissue and basic structures

4.1 Budova neuron. 4.2 Neuroglia

5. Reflex and reflex arc

Classification of reflexes

Awakening and power of nerve fibers

7.1 Budova nerve fiber. 7.2 Power of nerve fibers

Budova synapse. Mechanism of transmission of excitation at synapses

8.1 Budova synapse 8.2 Budova terminal plates

8.3 Mechanism for transmission of alarm at the terminal board

Galmuvannya at the central nervous system

9.1 Understanding about galmuvaniya 9.2 Types and mechanisms of galmuvaniya

10. Autonomic nervous system

10.1 Budova’s autonomic nervous system

10.2 Functional significance of the autonomic nervous system

11. Head bark

11.1 Budova pivkul. Sira ta bila speech and meaning

12. Damage to the nervous system and its prevention (Self-preparation)

Literature:

Babsky E.B., Zubkov A.A., Kositsky G.I., Khodorov B.I. Human physiology. M.: Medicine, 1966, - 656 p. ( 403-415)

Gayda S. P. Anatomy and physiology of humans. K.: Vishcha School, 1972, - 218 p. (173-192)

Galperin S.I. Human anatomy and physiology. M.: graduate School, 1969, - 470 pp. ( 420-438 ).

Leontyeva N.N., Marinova K.V. Anatomy and physiology child's body(Fundamentals of the study of the cell and the development of the body, nervous system, musculoskeletal system): Textbook. for pedagogical students Inst. - 2nd ed., revised - M.: Education, 1986. - 287 p.: ill. ( 75-86; 92-94; 103-104; 131-140 ).

Khripkova A. G. Age physiology. M.: Education, 1978, - 288 p. ( 44-77 );

Khripkova A.V., Antropova M.V., Farber D.A. Age physiology and school hygiene. M.: Education, 1990, - 362 p. ( 14-38 ).

Key words: AXON, UNCONDITIONED REFLEX, AUTONOMIC NERVOUS SYSTEM, REFLEX TIME, GANGLIA, DENDRITE, CORTEX OF THE LARGE HEMISPHERES, LABILITY, BRAINSTEM, NEUROGLIA, NEURON, NEUROFIBRILS, NEUROFILAMENT, SCHWANN K LETKA, PERIPHERAL NERVOUS SYSTEM, REFLECTOR ARC, PARASYMPATHETIC NERVOUS SYSTEM, REFLEX, SYMPATHETIC NERVOUS SYSTEM, SYNAPSE, CORTAL STRUCTURE, CONDITIONED REFLEX, INHIBITION, CENTRAL NERVOUS SYSTEM, CENTRAL REFLEX TIME.

IMPORTANCE AND DEVELOPMENT OF THE NERVOUS SYSTEM

The main importance of the nervous system is to ensure the best adaptation of the body to the influence of the external environment and the implementation of its reactions as a whole. The stimulation received by the receptor causes a nerve impulse that is transmitted to the central nervous system (CNS), where analysis and synthesis of information, resulting in a response.

The nervous system provides interconnection between individual organs and organ systems (1). She regulates physiological processes, occurring in all cells, tissues and organs of the human and animal body (2). For some organs, the nervous system has a triggering effect (3). In this case, the function is completely dependent on the influences of the nervous system (for example, the muscle contracts due to the fact that it receives impulses from the central nervous system). For others, it only changes existing level their functioning (4). (For example, an impulse coming to the heart changes its work, slows down or speeds up, strengthens or weakens).

The influences of the nervous system occur very quickly (the nerve impulse travels at a speed of 27-100 m/s or more). The impact address is very precise (directed to specific organs) and strictly dosed. Many processes are due to the presence of feedback from the central nervous system with the organs it regulates, which, by sending afferent impulses to the central nervous system, inform it about the nature of the impact received.

The more complexly organized and more highly developed the nervous system is, the more complex and diverse the body’s reactions are, the more perfect its adaptation to environmental influences.

2. Classification and structure of the nervous system

The nervous system is traditionally divided by structure into two main sections: the central nervous system and the peripheral nervous system.

TO central nervous system include the brain and spinal cord peripheral- nerves extending from the brain and spinal cord and nerve ganglia - ganglia(a collection of nerve cells located in different parts of the body).

By functional properties nervous system divide into somatic, or cerebrospinal, and autonomic.

TO somatic nervous system refer to that part of the nervous system that innervates the musculoskeletal system and provides sensitivity to our body.

TO autonomic nervous system include all other departments that regulate the activity of internal organs (heart, lungs, excretory organs, etc.), smooth muscles of blood vessels and skin, various glands and metabolism (has a trophic effect on all organs, including skeletal muscles).

3. Main stages of development of the nervous system

The nervous system begins to form in the third week of embryonic development from the dorsal part of the outer germ layer(ectoderm). First, a neural plate is formed, which gradually turns into a groove with raised edges. The edges of the groove approach each other and form a closed neural tube . From the bottom(tail) part of the neural tube forms the spinal cord, from the rest (anterior) - all parts of the brain: medulla oblongata, pons and cerebellum, midbrain, intermediate and cerebral hemispheres.

The brain is divided into three sections based on their origin, structural features and functional significance: trunk, subcortical region and cerebral cortex. Brain stem- This is a formation located between the spinal cord and the cerebral hemispheres. It includes the medulla oblongata, midbrain and diencephalon. To the subcortical department include the basal ganglia. Cerebral cortex is the highest part of the brain.

During development, three extensions are formed from the anterior part of the neural tube - the primary brain vesicles (anterior, middle and posterior, or rhomboid). This stage of brain development is called the trivesicular development(endpaper I, A).

In a 3-week embryo, the division of the anterior and rhomboid vesicles into two more parts by the transverse groove is well expressed, as a result of which five brain vesicles are formed - pentavesicular stage of development(endpaper I, B).

These five brain vesicles give rise to all parts of the brain. Brain vesicles grow unevenly. The anterior bladder develops most intensively, which already at an early stage of development is divided by a longitudinal groove into right and left. In the third month of embryonic development, the corpus callosum is formed, which connects the right and left hemispheres, and the posterior sections of the anterior bladder completely cover the diencephalon. In the fifth month of intrauterine development of the fetus, the hemispheres extend to the midbrain, and in the sixth month they completely cover it (color table II). By this time, all parts of the brain are well expressed.

The autonomic nervous system regulates the functioning of all human organs. Functions, meaning and role of the autonomic nervous system

The human autonomic nervous system has a direct impact on the functioning of many internal organs and systems. Thanks to it, breathing, blood circulation, movement and other functions of the human body are carried out. Interestingly, despite its significant influence, the autonomic nervous system is very “secretive”, that is, no one can clearly sense changes in it. But this does not mean that we do not need to pay due attention to the role of the ANS in the human body.

Human nervous system: its divisions

The main task of the human nervous system is to create a device that would connect all the organs and systems of the human body together. Thanks to this, he could exist and function. The basis for the functioning of the human nervous system is a peculiar structure called a neuron (they create contact with each other using nerve impulses). It is important to know that the anatomy of the human nervous system is a combination of two sections: the animal (somatic) and autonomic (autonomic) nervous systems. The first was created mainly so that the human body could contact the external environment. Therefore, this system has a second name - animal (i.e. animal), due to the performance of those functions that are inherent in them. The importance of the autonomic nervous system for humans is no less important, but the essence of its work is completely different - control over those functions that are responsible for breathing, digestion and other roles inherent primarily in plants (hence the second name of the system - autonomous).

What is the human autonomic nervous system?

The ANS carries out its activities with the help of neurons (a set of nerve cells and their processes). They, in turn, work by sending certain signals to various organs, systems and glands from the spinal cord and brain. It is interesting that the neurons of the autonomic part of the human nervous system are responsible for the functioning of the heart (its contractions), the functioning of the gastrointestinal tract (intestinal motility), and the activity of salivary glands. Actually, this is why they say that the autonomic nervous system organizes the work of organs and systems unconsciously, since initially these functions were inherent in plants, and then in animals and humans. The neurons that form the basis of the ANS are capable of creating certain clusters located in the brain and spinal cord. They were given the name "vegetative nuclei". Also, near the organs and spine, the autonomic part of the NS is capable of forming nerve nodes. So, the vegetative nuclei are the central part of the animal system, and the nerve ganglia are the peripheral part. In essence, the ANS is divided into two parts: parasympathetic and sympathetic.

What role does the ANS play in the human body?

Often people cannot answer a simple question: “The autonomic nervous system regulates the functioning of what: muscles, organs or systems?”

In fact, it is, in essence, a kind of peculiar “response” of the human body to irritations from the outside and from the inside. It is important to understand that the autonomic nervous system works in your body every second, but its activity is invisible. For example, regulating the normal internal state of a person (blood circulation, breathing, excretion, hormone levels, etc.) is the main role of the autonomic nervous system. In addition, it can have a direct impact on other components of the human body, for example, muscles (heart, skeletal), various sensory organs (for example, dilation or constriction of the pupil), glands of the endocrine system and much more. The autonomic nervous system regulates the functioning of the human body through various effects on its organs, which can be roughly represented by three types:

Control of metabolism in the cells of various organs, so-called trophic control;

An indispensable effect on organ functions, for example, on the functioning of the heart muscle - functional control;

Influence on organs by increasing or decreasing their blood flow - vasomotor control.

Composition of the human ANS

It is important to note the main thing: the ANS is divided into two components: parasympathetic and sympathetic. The last of them is usually associated with processes such as, for example, fighting, running, i.e., strengthening the functions of various organs.

At the same time, there are following processes: increased contractions of the heart muscle (and, as a result, an increase in blood pressure above normal), increased sweating, enlarged pupils, poor work intestinal peristalsis. The parasympathetic nervous system works in a completely different way, that is, in the opposite way. It is characterized by such actions in the human body during which it rests and assimilates everything. When it begins to activate the mechanism of its work, the following processes are observed: constriction of the pupil, decreased sweat secretion, the heart muscle works more weakly (i.e., the number of its contractions decreases), intestinal motility becomes more active and decreases blood pressure. The functions of the ANS are reduced to the work of its above-studied departments. Their interconnected work helps maintain the human body in balance. More to the point in simple language, then these components of the ANS must exist in a complex, constantly complementing each other. This system works only due to the fact that the parasympathetic and sympathetic nervous systems are able to release neurotransmitters, which connect organs and systems using nerve signals.

Control and testing of the autonomic nervous system - what is it?

The functions of the autonomic nervous system are under the continuous control of several main centers:

1. Spinal cord. The sympathetic nervous system (SNS) creates elements that are in close proximity to the spinal cord trunk, and its external components are represented by the parasympathetic division of the ANS.
2. Brain. It has the most direct effect on the functioning of the parasympathetic and sympathetic nervous systems, regulating balance throughout the human body.
3. Brain stem. This is a kind of connection that exists between the brain and spinal cord. It is able to control the functions of the ANS, namely its parasympathetic department (blood pressure, breathing, heart contractions, etc.).
4. Hypothalamus- Part diencephalon. It affects sweating, digestion, heart rate, etc.
5. Limbic system(essentially, these are human emotions). Located under the cerebral cortex. It affects the work of both departments of the ANS.

If we take into account the above, the role of the autonomic nervous system is immediately noticeable, because its activity is controlled by such important components of the human body.

Functions performed by the ANS

They arose thousands of years ago, when people learned to survive in difficult conditions. The functions of the human autonomic nervous system are directly related to the work of its two main sections. So, the parasympathetic system is capable of normalizing the functioning of the human body after suffering stress (activation of the sympathetic department of the ANS). Thus, emotional state is balanced. Of course, this part of the ANS is also responsible for other important roles, such as sleep and rest, digestion and reproduction. All this is carried out due to acetylcholine (a substance that transmits nerve impulses from one nerve fiber to another).
The work of the sympathetic department of the ANS is aimed at activating all vital processes of the human body: blood flow to many organs and systems increases, heart rate increases, sweating increases, and much more. It is these processes that help a person survive stressful situations. Therefore, we can conclude that the autonomic nervous system regulates the functioning of the human body as a whole, influencing it in one way or another.

Sympathetic Nervous System (SNS)

This part of the human ANS is associated with the body’s fight or response to internal and external stimuli. Its functions are as follows:

Inhibits the functioning of the intestines (its peristalsis), by reducing the blood flow to it;

Increased sweating;

When a person lacks air, his ANS, with the help of appropriate nerve impulses, expands the bronchioles;

Due to the narrowing of blood vessels, an increase in blood pressure;

Normalizes blood glucose levels by reducing it in the liver.

It is also known that the autonomic nervous system regulates the work of skeletal muscles - its sympathetic department is directly involved in this. For example, when your body experiences stress in the form of elevated temperature, the sympathetic division of the ANS immediately works as follows: it transmits appropriate signals to the brain, and it, in turn, with the help of nerve impulses, increases sweating or dilates the skin pores. Thus, the temperature is significantly reduced.

Parasympathetic nervous system (PNS)

This component of the ANS is aimed at creating in the human body a state of rest, calm, and assimilation of all vital processes. His work boils down to the following:

Strengthens the functioning of the entire gastrointestinal tract, increasing blood flow to it;

It directly affects the salivary glands, stimulating the production of saliva, thereby accelerating intestinal motility;

Reduces pupil size;

Exercises the strictest control over the work of the heart and all its departments;

Reduces the size of bronchioles when blood oxygen levels become normal.

It is very important to know that the autonomic nervous system regulates the functioning of the muscles of various organs - this issue is also dealt with by its parasympathetic department. For example, contraction of the uterus during excitement or postpartum period associated specifically with the operation of this system. And a man’s erection is subject only to its influence. After all, with the help of nerve impulses, blood flows to the male genital organs, to which the muscles of the penis react.

How does a stressful situation affect the ANS?

I would like to say right away that it is stress that can cause improper functioning of the ANS.
The functions of the autonomic nervous system can be completely paralyzed when such a situation arises. For example, a threat to a person’s life has arisen (a huge stone falls on him, or a wild animal suddenly appears in front of him). Someone will immediately run away, while others will simply freeze in place without the ability to move from a dead point. This does not depend on the person himself; this is how his ANS reacted at an unconscious level. And all this is due to the nerve endings located in the brain, medulla oblongata, and limbic system (responsible for emotions). After all, it has already become clear that the autonomic nervous system regulates the functioning of many systems and organs: digestion, the cardiovascular system, reproduction, the activity of the lungs and urinary tract. Therefore, there are many centers in the human body that can respond to stress thanks to the work of the ANS. But don't worry too much, because most of We do not experience strong shocks in our lives, so the occurrence of such states is rare for a person.

Deviations in human health caused by improper functioning of the ANS

Of course, from the above it became clear that the autonomic nervous system regulates the functioning of many systems and organs in the human body. Therefore, any functional disturbances in its operation can significantly disrupt this work process. By the way, the causes of such disorders can be either heredity or diseases acquired during life. Often the work of the human ANS is “invisible” in nature, but problems in this activity are noticeable based on the following symptoms:

Nervous system: the body’s inability to lower body temperature without extra help;

Gastrointestinal tract: vomiting, constipation or diarrhea, inability to swallow food, urinary incontinence and much more;

Skin problems (itching, redness, peeling), brittle nails and hair, increased or decreased sweating;

Vision: blurred image, lack of tears, difficulty focusing;

Respiratory system: incorrect response to low or high oxygen levels in the blood;

Heart and vascular system: fainting, increased heart rate, shortness of breath, dizziness, tinnitus;

Urinary system: any problems in this area (incontinence, frequency of urination);

Reproductive system: inability to achieve orgasm, premature erection.

People suffering from an autonomic neuropathy disorder often cannot control its development. It often happens that progressive autonomic dysfunction begins with diabetes. And in this case, it will be enough to clearly control your blood sugar levels. If the reason is different, you can simply take control of those symptoms that, to one degree or another, lead to autonomic neuropathy:

Gastrointestinal system: medications that relieve constipation and diarrhea; various exercises that increase mobility; maintaining a certain diet;

Skin: various ointments and creams that help relieve irritation; antihistamines to reduce itching;

Cardiovascular system: increased fluid intake; wearing special underwear; taking medications that control blood pressure.

We can conclude that the autonomic nervous system regulates the functional activity of almost the entire human body. Therefore, any problems that arise in his work should be noticed and studied by you with the help of highly qualified medical professionals. After all, the importance of the ANS for a person is enormous - it is thanks to it that he learned to “survive” in stressful situations.

1) is the material basis of mental activity
2) provides adaptation to the environment
3)....
4)....

Diman fighter

The nervous system ensures the relationship between individual organs and organ systems and the functioning of the body as a whole. It regulates and coordinates the activities of various organs, adapts the activities of the whole organism as whole system to changing conditions of the external and internal environment. With the help of the nervous system, various stimuli from the environment and internal organs are perceived and analyzed, as well as responses to these stimuli. At the same time, it should be borne in mind that the completeness and subtlety of the body’s adaptation to the environment is carried out through the interaction of nervous and humoral regulatory mechanisms.

Nerve endings are located throughout the human body. They have a vital function and are an integral part of the entire system. The structure of the human nervous system is a complex branched structure that runs through the entire body.

The physiology of the nervous system is a complex composite structure.

The neuron is considered the basic structural and functional unit of the nervous system. Its processes form fibers that are excited when exposed and transmit impulses. The impulses reach the centers where they are analyzed. Having analyzed the received signal, the brain transmits the necessary reaction to the stimulus to the appropriate organs or parts of the body. The human nervous system is briefly described by the following functions:

• providing reflexes;
• regulation of internal organs;
• ensuring the interaction of the body with the external environment, by adapting the body to changing external conditions and irritants;
• interaction of all organs.

The importance of the nervous system lies in ensuring the vital functions of all parts of the body, as well as the interaction of a person with the outside world. The structure and functions of the nervous system are studied by neurology.

Structure of the central nervous system

The anatomy of the central nervous system (CNS) is a collection of neuronal cells and neural processes of the spinal cord and brain. A neuron is a unit of the nervous system.

The function of the central nervous system is to provide reflex activity and processing of impulses coming from the PNS.

Features of the structure of the PNS

Thanks to the PNS, the activity of the entire human body is regulated. The PNS consists of cranial and spinal neurons and fibers that form ganglia.

Its structure and functions are very complex, so any slightest damage, for example damage to blood vessels in the legs, can cause serious disruption to its functioning. Thanks to the PNS, all parts of the body are controlled and the vital functions of all organs are ensured. The importance of this nervous system for the body cannot be overestimated.

The PNS is divided into two divisions - the somatic and autonomic PNS systems.

Performs double work - collecting information from the senses, and further transmitting this data to the central nervous system, as well as ensuring the motor activity of the body by transmitting impulses from the central nervous system to the muscles. Thus, it is the somatic nervous system that is the instrument of human interaction with the outside world, as it processes signals received from the organs of vision, hearing and taste buds.

Ensures the performance of the functions of all organs. It controls the heartbeat, blood supply, and breathing. It contains only motor nerves that regulate muscle contraction.

To ensure the heartbeat and blood supply, the efforts of the person himself are not required - this is controlled by the autonomic part of the PNS. The principles of the structure and function of the PNS are studied in neurology.

Departments of the PNS

The PNS also consists of the afferent nervous system and the efferent nervous system.

The afferent region is a collection of sensory fibers that process information from receptors and transmit it to the brain. The work of this department begins when the receptor is irritated due to any impact.

The efferent system differs in that it processes impulses transmitted from the brain to effectors, that is, muscles and glands.

One of the important parts of the autonomic division of the PNS is the enteric nervous system. The enteric nervous system is formed from fibers located in the gastrointestinal tract and urinary tract. The enteric nervous system controls the motility of the small and large intestines. This section also regulates the secretions released in the gastrointestinal tract and provides local blood supply.

The importance of the nervous system is to ensure the functioning of internal organs, intellectual function, motor skills, sensitivity and reflex activity. The child’s central nervous system develops not only during the prenatal period, but also during the first year of life. Ontogenesis of the nervous system begins from the first week after conception.

The basis for brain development is formed already in the third week after conception. The main functional nodes are identified by the third month of pregnancy. By this time, the hemispheres, trunk and spinal cord have already been formed. By the sixth month, the higher parts of the brain are already better developed than the spinal part.

By the time a baby is born, the brain is the most developed. The size of the brain in a newborn is approximately an eighth of the child’s weight and ranges from 400 g.

The activity of the central nervous system and PNS is greatly reduced in the first few days after birth. This may consist in an abundance of new irritating factors for the baby. This is how the plasticity of the nervous system manifests itself, that is, the ability of this structure to be rebuilt. As a rule, the increase in excitability occurs gradually, starting from the first seven days of life. The plasticity of the nervous system deteriorates with age.

Types of CNS

In the centers located in the cerebral cortex, two processes simultaneously interact - inhibition and excitation. The rate at which these states change determines the types of nervous systems. While one part of the central nervous system is excited, another is slowed down. This determines the features of intellectual activity, such as attention, memory, concentration.

Types of the nervous system describe the differences between the speed of inhibition and excitation of the central nervous system in different people.

People may differ in character and temperament, depending on the characteristics of the processes in the central nervous system. Its features include the speed of switching neurons from the process of inhibition to the process of excitation, and vice versa.

The types of nervous system are divided into four types.

• The weak type, or melancholic, is considered the most predisposed to the occurrence of neurological and psycho-emotional disorders. It is characterized by slow processes of excitation and inhibition. The strong and unbalanced type is choleric. This type is characterized by the predominance of excitation processes over inhibition processes.
• Strong and agile - this is a type of sanguine person. All processes occurring in the cerebral cortex are strong and active. A strong but inert, or phlegmatic type, is characterized by a low speed of switching nervous processes.

The types of the nervous system are interconnected with temperaments, but these concepts should be distinguished, because temperament characterizes a set of psycho-emotional qualities, and the type of the central nervous system describes physiological characteristics processes occurring in the central nervous system.

CNS protection

The anatomy of the nervous system is very complex. The central nervous system and PNS suffer due to the effects of stress, overexertion and lack of nutrition. For the normal functioning of the central nervous system, vitamins, amino acids and minerals are necessary. Amino acids take part in brain function and are building materials for neurons. Having figured out why vitamins and amino acids are needed and why, it becomes clear how important it is to provide the body with the necessary amount of these substances. Glutamic acid, glycine and tyrosine are especially important for humans. The regimen for taking vitamin-mineral complexes for the prevention of diseases of the central nervous system and PNS is selected individually by the attending physician.

Damage to the bundles, congenital pathologies and abnormalities of brain development, as well as the action of infections and viruses - all this leads to disruption of the central nervous system and PNS and the development of various pathological conditions. Such pathologies can cause a number of very dangerous diseases - immobility, paresis, muscle atrophy, encephalitis and much more.

Malignant neoplasms in the brain or spinal cord lead to a number of neurological disorders. If an oncological disease of the central nervous system is suspected, an analysis is prescribed - histology of the affected parts, that is, an examination of the composition of the tissue. A neuron, as part of a cell, can also mutate. Such mutations can be identified by histology. Histological analysis is carried out according to the doctor’s indications and consists of collecting the affected tissue and its further study. For benign formations, histology is also performed.

The human body contains many nerve endings, damage to which can cause a number of problems. Damage often leads to impaired mobility of a body part. For example, an injury to the hand can lead to pain in the fingers and impaired movement. Osteochondrosis of the spine can cause pain in the foot due to the fact that an irritated or compressed nerve sends pain impulses to receptors. If the foot hurts, people often look for the cause in a long walk or injury, but the pain syndrome can be triggered by damage to the spine.

If you suspect damage to the PNS, as well as any related problems, you should be examined by a specialist.

In order to perceive internal and external stimuli, the nervous system has sensory structures located in the analyzers. These structures will include certain devices capable of receiving information:

1. Proprioceptors. They collect all information regarding the condition of muscles, bones, fascia, joints, and the presence of fiber.

2. Exteroceptors. They are located in human skin, sensory organs, and mucous membranes. Able to perceive irritating factors received from the surrounding environment.

3. Interoreceptors. Located in tissues and internal organs. Responsible for the perception of biochemical changes received from the external environment.

Basic meaning and functions of the nervous system

It is important to note that with the help of the nervous system, perception and analysis of information about stimuli from the external world and internal organs is carried out. She is also responsible for responses to these irritations.

The human body, the subtlety of its adaptation to changes in the surrounding world, is accomplished primarily through the interaction of humoral and nervous mechanisms.

The main functions include:

1. Definition of a person’s mental health and activities, which constitute the basis of his social life.

2. Regulation of the normal functioning of organs, their systems, tissues.

3. Integration of the body, its unification into a single whole.

4. Maintaining the relationship of the whole organism with the environment. If environmental conditions change, the nervous system adapts to these conditions.

In order to accurately understand the importance of the nervous system, it is necessary to delve into the meaning and main functions of the central and peripheral nervous systems.

The importance of the central nervous system

It is the main part of the nervous system of both humans and animals. Its main function is the implementation of various levels of complexity of reactions called reflexes.

Thanks to the activity of the central nervous system, the brain is able to consciously reflect changes in the external conscious world. Its significance is that it regulates various kinds of reflexes and is able to perceive stimuli received both from internal organs and from the external world.

The importance of the peripheral nervous system

The PNS connects the central nervous system to the limbs and organs. Its neurons are located far beyond the central nervous system - the spinal cord and brain.

It is not protected by bones, which can lead to mechanical damage or harmful effects of toxins

Thanks to the proper functioning of the PNS, the body's movements are coordinated. This system is responsible for conscious control of the actions of the entire organism. Responsible for responding to stressful situations and danger. Increases heart rate. In case of excitement, it increases the level of adrenaline.

It is important to remember that you should always take care of your health. After all, when a person leads a healthy lifestyle, adheres to the correct daily routine, he does not burden his body in any way and thereby remains healthy.

Nervous system

Functions of the nervous system. The nervous system performs the following functions:

· Sensory – perceiving, transmitting and processing information, the nervous system communicates with the external and internal environment and ensures adaptation to living conditions;

· Motor – regulates the motor functions of organs and systems of the human body;

· Integrative – ensures fast and coordinated interaction between organs, thanks to which the human body functions as a single whole;

· Mental - the central section of the nervous system is the substrate of higher mental manifestations - consciousness, speech, thinking, memory, learning, with the help of which people communicate with each other and learn about the environment.

General plan of the structure of the nervous system. The nervous system is topographically divided into central And peripheral , and functionally – on somatic And vegetative . The central nervous system (CNS) includes the spinal cord and brain, and the peripheral nervous system includes nerves and ganglia.

The central nervous system is formed by neurons and neuroglia. In the brain and spinal cord, neurons can be arranged in the form

· Clusters called nuclei (for example, the nuclei of the cranial nerves);

· Clusters called nerve centers. These centers are necessary for the implementation of a certain reflex or regulation of a particular function (for example, the breathing center in the medulla oblongata);

· Networks, that is, diffusely (for example, neurons of the reticular formation);

· Parallel horizontal layers (for example, in the cerebral cortex and cerebellum);

· Vertical columns (for example, in the cerebral cortex).

The processes of central neurons within the brain form its pathways and connections in neural networks. The processes of neurons located outside the brain form peripheral nerves.

The central nervous system analyzes information coming from the external and internal environment of the body, and forms its response to this information.

Ganglia of the peripheral nervous system are also clusters of neurons surrounded by neuroglial cells. There are spinal and cranial ganglia.

Nerves are formed by long processes of neurons. The peripheral nerves include 12 pairs of cranial nerves and 31 pairs of spinal nerves. The cranial nerves innervate mainly the structures of the head and neck, except for the vagus nerve, which innervates the internal organs. Spinal nerves innervate the muscles of the trunk and limbs. Some nerves carry information from receptors to the central nervous system and are called sensory, or afferent . Other nerves transmit signals from the central nervous system to all organs and systems of the body and are called motor, or efferent . Most peripheral nerves are mixed: they contain both afferent and efferent fibers.

Somatic nervous system provides tone, body posture, motor reactions and innervation of the skin.

Vegetative, or autonomic nervous system regulates the functioning of internal organs. It is associated with the maintenance of homeostasis, metabolism, growth and development of the body, neuroendocrine regulation and trophic innervation of skeletal muscles, skin and the nervous system itself. The autonomic nervous system is divided into sympathetic and parasympathetic divisions.

Both the somatic nervous system and the autonomic nervous system have central and peripheral sections. Central department located in the spinal cord and brain and is represented by nuclei, and the peripheral section is located outside the central nervous system and is represented by nerves.

31.Structure and physiological functions neuron.

A neuron is a cell soms(body) from which several short processes extend - dendrites With spines at the ends there is one long process - axon, which branches to form collaterals. Collaterals and spines are necessary to increase the area of ​​contact of one neuron with other neurons

The neuron has a specialized plasma membrane, conducting impulses. The cytoplasm of a neuron, like any eukaryotic cell, contains a nucleus and organelles. The peculiarity of the internal structure of a neuron is that in the neuroplasm of the latter, in addition to the usual organelles, there are special structures - neurofibrils. The cytoplasm of a neuron also contains pigment substances on which the color of the neuron depends. In addition, the neuron contains a large number of mitochondria and an endoplasmic reticulum that changes in volume, depending on the functional activity.

The soma and dendrites of a neuron do not have a myelin sheath (the myelin sheath is formed by a white fat-like substance), therefore, in the mass of the brain they have gray. The substance they form is called gray matter brain. Axons covered with a myelin sheath form white matter The brain is a collection of pathways. The myelin sheath of the axon is not continuous; at certain intervals it is interrupted - these places are called Ranvier interceptions. The portion of the soma from which the axon arises is called axon hillock. The axon hillock does not have a myelin sheath.

Depending on the number of processes, all neurons are divided into

1. bipolar, which have one axon and one dendrite and are located in the retina of the eye and in the sound-receiving apparatus of the inner ear;

2. polypolar – have one axon and many dendrites, located in the brain;

3. false unipolar - one process extends from the soma, which then at some distance is divided into two: an axon and a relatively long dendrite; located in peripheral ganglia;

4. unipolar - have one process, are present in the human body only in the prenatal period.

Depending on the shape of the soma, neurons are divided into

1. pyramidal - the catfish has the shape of a pyramid;

2. star-shaped - the catfish has the appearance of a star;

3. spindle-shaped - the catfish has the appearance of a spindle.

The main function of neurons is the reception, transformation and transmission of information, which is encoded in the form of spreading along the processes of the neuron electrical potentials– action potentials (AP). The neuron has an electrically excitable membrane that is negatively charged relative to the surrounding extracellular fluid. Membrane charge – membrane potential, or resting potential (RP), - is not the same for different neurons and depends on a number of factors. The membrane charge is created due to different concentrations of sodium, potassium, and chlorine ions inside and outside the cell. When excited, a neuron generates an AP, or nerve impulse. In this case, depolarization of the membrane occurs, and currents appear in the dendrites and soma directed towards the axon hillock. In the area of ​​the axon hillock, a nerve impulse is generated, which spreads along the axon. If the axon is covered with a myelin sheath, then the AP causes excitation only at the nodes of Ranvier; if the axon is not covered with a sheath, then the AP causes excitation at each adjacent point of the fiber. The speed of PD propagation depends on

1. axon diameter - the thicker the axon, the higher the speed of propagation;

2. the presence of a myelinated membrane;

3. PP values ​​- the higher the PP, the higher the propagation speed;

4. PD values ​​– the higher the PD, the higher the propagation speed.

A neuron works as a signal transducer: it sums up many incoming stimuli and forms its response on this basis. A neuron does not generate a single impulse, but a series of several impulses that occur at a certain frequency. This frequency conversion is one of the main ways of encoding information in the nervous system.

Functionally, all neurons are divided into

1. afferent (sensitive), carrying information from the external and internal environment to the central nervous system;

2. efferent (motor), carrying an information response from the central nervous system to the organs;

3. associative (intercalary) – neurons that connect afferent and efferent cells with each other.

To transmit and process information, neurons interact with each other and with cells executive bodies through special contacts - synapses . The synapse is divided into a presynaptic membrane, a synaptic cleft, and a postsynaptic membrane. According to the nature of their influence on the cell, synapses are divided into excitatory and inhibitory, and according to the method of signal transmission - electrical and chemical. In humans, only chemical synapses are present. Substances that transmit signals through synaptic contact are called mediators . These include acetylcholine, adrenaline, serotonin, histamine, norepinephrine, and gamma-aminobutyric acid (GABA). Mediators pass through the presynaptic membrane, bind to receptors on the postsynaptic membrane, thereby changing it membrane potential(resting potential - PP ). Thus, at synapses, a chemical signal is converted into an electrical signal.

Synaptic contacts can be: axosomatic, axodendritic, axo-axonal and dendro-dendritic. The synapses between the axon terminal and the muscle are called neuromuscular, or end plates.

The formation of new synapses underlies the property of the nervous system - plasticity. The development of the child’s brain, learning and memory processes depend on this property.

Nerve fibers

Nerve fibers- processes of nerve cells (neurons) that have a membrane and are capable of conducting nerve impulses.

The main component of the nerve fiber is the process of the neuron, which forms, as it were, the axis of the fiber. For the most part this is an axon. The neural spine is surrounded by a sheath complex structure, together with which it forms a fiber. The thickness of the nerve fiber in the human body, as a rule, does not exceed 30 micrometers.

Nerve fibers are divided into pulpy (myelinated) and non-myelinated (non-myelinated). The former have a myelin sheath covering the axon, the latter lack a myelin sheath.

Myelin fibers predominate in both the peripheral and central nervous systems. Nerve fibers lacking myelin are located predominantly in the sympathetic division of the autonomic nervous system. At the point where the nerve fiber departs from the cell and in the area of ​​its transition into the final branches, the nerve fibers can be devoid of any membranes, and then they are called bare axial cylinders.

Depending on the nature of the signal carried through them, nerve fibers are divided into motor autonomic, sensory and motor somatic.

The structure of nerve fibers

Myelinated nerve fiber contains the following elements (structures):
1) an axial cylinder located in the very center of the nerve fiber,
2) the myelin sheath covering the axial cylinder,
3) Schwann shell.

The axial cylinder consists of neurofibrils. The pulpy membrane contains a large amount of lipoid substances known as myelin. Myelin ensures the speed of nerve impulses. The myelin sheath does not cover the entire axial cylinder, forming gaps called nodes of Ranvier. In the area of ​​the nodes of Ranvier, the axial cylinder of the nerve fiber is adjacent to the superior Schwann membrane.

The fiber space located between two nodes of Ranvier is called a fiber segment. In each such segment, the nucleus of the Schwann membrane can be seen on stained preparations. It lies approximately in the middle of the segment and is surrounded by the protoplasm of the Schwann cell, the loops of which contain myelin. Between the nodes of Ranvier, the myelin sheath is also not continuous. In its thickness, so-called Schmidt-Lanterman notches are found, running in an oblique direction.

Schwann membrane cells, as well as neurons with processes, develop from the ectoderm. They cover the axial cylinder of the nerve fiber of the peripheral nervous system, similar to how glial cells cover the nerve fiber in the central nervous system. As a result, they may be called peripheral glial cells.

In the central nervous system, nerve fibers do not have Schwann sheaths. The role of Schwann cells here is performed by elements of oligodendroglia. An unmyelinated (unmyelinated) nerve fiber lacks a myelin sheath and consists only of an axial cylinder and a Schwann sheath.

Function of nerve fibers

Main function nerve fibers – transmission of nerve impulses. Currently, two types of nerve transmission have been studied: pulsed and non-pulse. Impulse transmission is provided by electrolyte and neurotransmitter mechanisms. The speed of nerve impulse transmission in myelinated fibers is much higher than in nonmyelinated fibers. In its implementation vital role belongs to myelin. This substance is capable of isolating a nerve impulse, as a result of which signal transmission along the nerve fiber occurs spasmodically, from one node of Ranvier to another.

Pulseless transmission is carried out by axoplasmic current along special axon microtubules containing trophogens - substances that have a trophic effect on the innervated organ.

The function of the nervous system is to control the activities of various systems and apparatuses that make up the whole organism, to coordinate the processes occurring in it, to establish relationships between the body and the external environment. The great Russian physiologist I.P. Pavlov wrote: “The activity of the nervous system is directed, on the one hand, to unify, integrate the work of all parts of the body, and on the other, to connect the body with the environment, to balance the body system with external conditions.”

Nerves penetrate into all organs and tissues, form numerous branches with receptor (sensory) and effector (motor, secretory) endings, and together with the central sections (brain and spinal cord) ensure the unification of all parts of the body into a single whole. The nervous system regulates the functions of movement, digestion, respiration, excretion, blood circulation, lymphatic drainage, immune (protective) and metabolic processes (metabolism), etc.

The activity of the nervous system, according to I.M. Sechenov, is reflexive in nature. Reflex (lat. reflexus - reflected) is the body's response to a particular irritation (external or internal influence), which occurs with the participation of the central nervous system (CNS). The human body, living in its external environment, interacts with it. The environment influences the body, and the body, in turn, reacts accordingly to these influences. The processes occurring in the body itself also cause a response. Thus, the nervous system ensures the interconnection and unity of the organism and the environment.

The structural and functional unit of the nervous system is the neuron (nerve cell, neurocyte). A neuron consists of a body and processes. The processes that conduct nerve impulses to the body of the nerve cell are called dendrites. From the neuron body, the nerve impulse is sent to another nerve cell or to working tissue along a process called an axon, or neurite. A nerve cell is dynamically polarized, that is, it is capable of transmitting a nerve impulse in only one direction - from the dendrite through the cell body to the axon (neurite).

Neurons in the nervous system, coming into contact with each other, form chains along which nerve impulses are transmitted (moved). The transmission of a nerve impulse from one neuron to another occurs at the places of their contacts and is ensured by a special kind of formations called interneuron synapses. A distinction is made between axsomatic synapses, when the axon terminals of one neuron form contacts with the body of the next, and axodendritic synapses, when the axon comes into contact with the dendrites of another neuron. The contact type of relationships in a synapse under various physiological conditions can, obviously, either be “created” or “destroyed,” providing the possibility of a selective reaction to any stimulation. In addition, the contact construction of chains of neurons creates the opportunity to conduct a nerve impulse in a certain direction. Due to the presence of contacts in some synapses and disconnection in others, the conduction of the impulse may be disrupted.

In a nerve chain, different neurons have different functions. In this regard, three main types of neurons are distinguished according to their morphofunctional characteristics.

1Sensitive, receptor, or afferent neurons. The bodies of these nerve cells always lie outside the brain or spinal cord, in the nodes (ganglia) of the peripheral nervous system. One of the processes extending from the body of the nerve cell follows to the periphery of one or another organ and ends there with one or another sensitive ending - a receptor that is capable of transforming the energy of external influence (irritation) into a nerve impulse. The second process is directed to the central nervous system, spinal cord or brain stem as part of the dorsal roots of the spinal nerves or corresponding cranial nerves.

The following types of receptors are distinguished depending on location:

1 exteroceptors perceive irritation from the external environment. They are located in the outer integument of the body, in the skin and mucous membranes, in the sensory organs;

2interoceptors receive irritation mainly due to changes in the chemical composition of the internal environment of the body and pressure in tissues and organs;

3proprioceptors perceive irritations in muscles, tendons, ligaments, fascia, and joint capsules.

Reception, i.e., the perception of irritation and the beginning of the spread of a nerve impulse along nerve conductors to the centers, I. P. Pavlov attributed to the beginning of the analysis process.

2Closing, intercalary, associative, or conductor neuron. This neuron transmits excitation from the afferent (sensitive) neuron to the efferent ones. The essence of this process is the transmission of the signal received by the afferent neuron to the efferent neuron for execution in the form of a response. I. P. Pavlov defined this action as “the phenomenon of nervous closure.” Closing (intercalary) neurons lie within the central nervous system.

3. Effector, efferent (motor or secretory) neuron. The bodies of these neurons are located in the central nervous system (or on the periphery - in the sympathetic, parasympathetic nodes). The axons (neurites) of these cells continue in the form of nerve fibers to the working organs (voluntary - skeletal and involuntary - smooth muscles, glands).

After these general comments, let's take a closer look reflex arc and the reflex act as the basic principle of the nervous system. Reflex arc is a chain of nerve cells, including afferent (sensitive) and effector (motor or secretory) neurons, along which the nerve impulse moves from the place of its origin (from the receptor) to the working organ (effector). Most reflexes are carried out with the participation of reflex arcs, which are formed by neurons of the lower parts of the central nervous system - neurons of the spinal cord.

The simplest reflex arc (Fig. 108) consists of only two neurons - afferent and effector (efferent). The body of the first neuron (receptor, afferent), as noted, is located outside the CNS. Usually this is a pseudounipolar (unipolar) neuron, the body of which is located in the spinal ganglion (ganglion spindle) or sensory ganglion of cranial nerves (ganglion sensoriale nn. cranialii). The peripheral process of this cell follows as part of the spinal nerves or cranial nerves with sensory fibers and their branches and ends with a receptor that perceives external (from the external environment) or internal (in organs, tissues) irritation. This irritation is transformed by the receptor into a nerve impulse, which reaches the body of the nerve cell, and then along the central process (the set of such processes forms the posterior, or sensitive, roots of the spinal nerves) is sent to the spinal cord or along the corresponding cranial nerves to the brain. IN gray matter spinal cord or in the motor nucleus of the brain, this process of the sensitive cell forms a synapse with the body of the second neuron (efferent, effector). In the interneuron synapse, with the help of mediators, nerve excitation is transferred from a sensitive (afferent) neuron to a motor (efferent) neuron, the process of which leaves the spinal cord as part of the anterior roots of the spinal nerves or motor (secretory) nerve fibers of the cranial nerves and is directed to the working organ, causing muscle contraction, or inhibition or increased secretion of the gland.

As a rule, the reflex arc does not consist of two neurons, but is much more complex. Between two neurons - receptor (afferent) and effector (afferent) - there is one or more closing (intercalary) neurons. In this case, excitation from the receptor neuron along its central process is transmitted not directly to the effector nerve cell, but to one or more interneurons. The role of interneurons in the spinal cord is performed by cells lying in the gray matter of the posterior columns. Some of these cells have an axon (neurite), which is directed to the motor cells of the anterior horns of the spinal cord at the same level and closes the reflex arc at the level of this segment of the spinal cord. The axon of other cells can pre-divide in a T-shape in the spinal cord into descending and ascending branches, which are directed to the motor nerve cells of the anterior horns of neighboring, superior or underlying segments. Along the route, each of the marked ascending or descending branches can send collaterals to the motor cells of these and other neighboring segments. In this regard, it becomes clear that irritation of even the smallest number of receptors can be transmitted not only to the nerve cells of a particular segment of the spinal cord, but also spread to the cells of several neighboring segments. As a result, the response is a contraction of not one muscle or even one group of muscles, but several groups at once. Thus, in response to irritation, a complex reflex movement occurs. This is one of the body’s responses (reflex) in response to external or internal irritation.

TO central nervous system (CNS) include the spinal cord and brain, which consist of gray and white matter. The gray matter of the spinal cord and brain is a collection of nerve cells along with the nearest branches of their processes. White matter is nerve fibers, processes of nerve cells that have a myelin sheath (hence the white color of the fibers). Nerve fibers form the pathways of the spinal cord and brain and connect various parts of the central nervous system and various nuclei (nerve centers) with each other.

Peripheral nervous system consists of roots, spinal and cranial nerves, their branches, plexuses and nodes lying in various parts of the human body.

According to another, anatomical and functional classification, the unified nervous system is also conventionally divided into two parts: somatic and autonomic, or autonomic. Somatic nervous system provides innervation mainly to the telosoma, namely the skin and skeletal (voluntary) muscles. This section of the nervous system performs the functions of connecting the body with the external environment through skin sensitivity and sensory organs.

Autonomic (autonomic) nervous system innervates all the insides, glands, including endocrine ones, involuntary muscles of organs, skin, blood vessels, heart, and also regulates metabolic processes in all organs and tissues.

The autonomic nervous system is in turn divided into the parasympathetic part, pars parasympathica, and the sympathetic part, pars sympathica. In each of these parts, as in the somatic nervous system, there are central and peripheral sections.

This division of the nervous system, despite its conventionality, has developed traditionally and seems quite convenient for studying the nervous system as a whole and its individual parts. In this regard, in the future we will also adhere to this classification in the presentation of the material.