Nervous system. How does the human nervous system work?

The human nervous system is similar in structure to the nervous system of higher mammals, but differs in the significant development of the brain. The main function of the nervous system is to control the vital functions of the entire organism.

Neuron

All organs of the nervous system are built from nerve cells called neurons. A neuron is capable of receiving and transmitting information in the form of a nerve impulse.

Rice. 1. Structure of a neuron.

The body of a neuron has processes with which it communicates with other cells. The short processes are called dendrites, the long ones are called axons.

The structure of the human nervous system

The main organ of the nervous system is the brain. Connected to it is the spinal cord, which looks like a cord about 45 cm long. Together, the spinal cord and brain make up the central nervous system (CNS).

Rice. 2. Scheme of the structure of the nervous system.

The nerves leaving the central nervous system make up the peripheral part of the nervous system. It consists of nerves and ganglia.

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Nerves are formed from axons, the length of which can exceed 1 m.

Nerve endings contact each organ and transmit information about their condition to the central nervous system.

There is also a functional division of the nervous system into somatic and autonomic (autonomic).

The part of the nervous system that innervates the striated muscles is called somatic. Her work is associated with the conscious efforts of a person.

The autonomic nervous system (ANS) regulates:

• circulation;
• digestion;
• selection;
• breath;
• metabolism;
• smooth muscle function.

Thanks to the work of the autonomic nervous system, many processes of normal life occur that we do not consciously regulate and usually do not notice.

The importance of the functional division of the nervous system in ensuring the normal functioning of the finely tuned mechanisms of the internal organs, independent of our consciousness.

The highest organ of the ANS is the hypothalamus, located in the intermediate part of the brain.

The VNS is divided into 2 subsystems:

• sympathetic;
• parasympathetic.

Sympathetic nerves activate organs and control them in situations that require action and increased attention.

Parasympathetic slows down the functioning of organs and turns on during rest and relaxation.

For example, sympathetic nerves dilate the pupil and stimulate the secretion of saliva. Parasympathetic, on the contrary, constrict the pupil and slow down salivation.

Reflex

This is the body's response to irritation from the external or internal environment.

The main form of activity of the nervous system is a reflex (from the English reflection - reflection).

An example of a reflex is withdrawing a hand from a hot object. The nerve ending senses high temperature and transmits a signal about it to the central nervous system. A response impulse arises in the central nervous system, going to the muscles of the arm.

Rice. 3. Reflex arc diagram.

The sequence: sensory nerve - CNS - motor nerve is called a reflex arc.

Brain

The brain is distinguished by the strong development of the cerebral cortex, in which the centers of higher nervous activity are located.

The characteristics of the human brain sharply distinguished him from the animal world and allowed him to create a rich material and spiritual culture.

What have we learned?

The structure and functions of the human nervous system are similar to those of mammals, but differ in the development of the cerebral cortex with the centers of consciousness, thinking, memory, and speech. The autonomic nervous system controls the body without the participation of consciousness. The somatic nervous system controls body movement. The principle of activity of the nervous system is reflex.

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The nervous system has 2 main parts: the brain and spinal cord make up the central nervous system (CNS), and the nerves make up the peripheral nervous system (PNS). Sensitive (sensory) neurons of the PNS transmit impulses from the sensory organs to the brain. Motor neurons that transmit brain commands are of 2 types. Neurons of the somatic nervous system (SNS) cause contractions of skeletal muscles, i.e. voluntary movements controlled by consciousness. Neurons of the autonomic nervous system (ANS) regulate breathing, digestion and other automatic processes that occur without the participation of consciousness. The ANS is divided into the sympathetic and parasympathetic systems, which have the opposite effect (for example, causing dilation and constriction of the pupil), thereby ensuring a stable state of the body.

All neurons are built basically the same. The cell body contains the nucleus. Short processes - dendrites - receive nerve impulses coming through synapses from other neurons. A long process - an axon - transmits impulses emanating from the body of the neuron. The body of the motor neuron pictured here is located in the central nervous system (CNS). It sends impulses to a certain structure of the body, forcing it to perform a specific job. An impulse can, for example, cause a muscle to contract or a gland to secrete secretions.

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Nervous system is the basis for any type of interaction between living beings in the surrounding world, as well as a system for maintaining homeostasis in multicellular organisms. The higher the organization of a living organism, the more complex the nervous system is. The basic unit of the nervous system is neuron- a cell that has short dendritic processes and a long axonal process.

The human nervous system can be divided into CENTRAL and PERIPHERAL, and also separately distinguished autonomic nervous system, which has its representation in both the central and peripheral nervous systems. The central nervous system consists of the brain and spinal cord, and the peripheral nervous system consists of the nerve roots of the spinal cord, cranial, spinal and peripheral nerves, as well as nerve plexuses.

BRAIN comprises:
two hemispheres,
cerebrum brainstem,
cerebellum.

Cerebral hemispheres divided into frontal lobes, parietal, temporal and occipital lobes. The hemispheres of the brain are connected through the corpus callosum.
— The frontal lobes are responsible for the intellectual and emotional sphere, thinking and complex behavior, conscious movements, motor speech and writing skills.
— The temporal lobes are responsible for hearing, sound perception, vestibular information, partial analysis of visual information (for example, recognition of faces), the sensory part of speech, participation in memory formation, influence on the emotional background, and influence on the autonomic nervous system through communication with the limbic system.
— The parietal lobes are responsible for various types of sensitivity (tactile, pain temperature, deep and complex spatial types of sensitivity), spatial orientation and spatial skills, reading, counting.
- Occipital lobes - perception and analysis of visual information.

Brain stem represented by the diencephalon (thalamus, epithalamus, hypothalamus and pituitary gland), midbrain, pons and medulla oblongata. Brain stem functions responsible for unconditioned reflexes, influence on the extrapyramidal system, taste, visual, auditory and vestibular reflexes, suprasegmental level of the autonomic system, control of the endocrine system, regulation of homeostasis, hunger and satiety, thirst, regulation of the sleep-wake cycle, regulation of respiration and the cardiovascular system , thermoregulation.

Cerebellum consists of two hemispheres and a vermis that connects the cerebellar hemispheres. Both the cerebral hemispheres and the cerebellar hemispheres are striated with grooves and convolutions. The cerebellar hemispheres also have nuclei with gray matter. The cerebellar hemispheres are responsible for coordination of movements and vestibular function, and the cerebellar vermis is responsible for maintaining balance, posture, and muscle tone. The cerebellum also influences the autonomic nervous system. The brain has four ventricles, in the system of which cerebrospinal fluid circulates and which are connected to the subarachnoid space of the cranial cavity and spinal canal.

Spinal cord consists of the cervical, thoracic, lumbar and sacral sections, has two thickenings: cervical and lumbar, and the central spinal canal (in which the cerebrospinal fluid circulates and which in the upper sections connects with the fourth ventricle of the brain).

Histologically, brain tissue can be divided into Gray matter, which contains neurons, dendrites (short processes of neurons) and glial cells, and white matter, in which axons lie, long processes of neurons covered with myelin. In the brain, gray matter is located mainly in the cerebral cortex, in the basal ganglia of the hemispheres and nuclei of the brainstem (midbrain, pons and medulla oblongata), and in the spinal cord, gray matter is located in depth (in its central parts), and the outer parts of the spinal cord are represented by white matter.

Peripheral nerves can be divided into motor and sensory, forming reflex arcs that are controlled by parts of the central nervous system.

Autonomic nervous system has a division into suprasegmental And segmental.
— The suprasegmental nervous system is located in the limbic-reticular complex (structures of the brain stem, hypothalamus and limbic system).
— The segmental part of the nervous system is divided into the sympathetic, parasympathetic and metasympathetic nervous systems. The sympathetic and parasympathetic nervous systems are also divided into central and peripheral. The central divisions of the parasympathetic nervous system are located in the midbrain and medulla oblongata, and the central divisions of the sympathetic nervous system are located in the spinal cord. The metasympathetic nervous system is organized by nerve plexuses and ganglia in the walls of the internal organs of the chest (heart) and abdominal cavity (intestines, bladder, etc.).

In evolution, the nervous system has undergone several stages of development, which became turning points in the qualitative organization of its activities. These stages differ in the number and types of neuronal formations, synapses, signs of their functional specialization, and in the formation of groups of neurons interconnected by common functions. There are three main stages of the structural organization of the nervous system: diffuse, nodular, tubular.

Diffuse The nervous system is the most ancient, found in coelenterates (hydra). Such a nervous system is characterized by a multiplicity of connections between neighboring elements, which allows excitation to freely spread throughout the nervous network in all directions.

This type of nervous system provides wide interchangeability and thereby greater reliability of functioning, but these reactions are imprecise and vague.

Nodal the type of nervous system is typical for worms, mollusks, and crustaceans.

It is characterized by the fact that the connections of nerve cells are organized in a certain way, excitation passes along strictly defined paths. This organization of the nervous system turns out to be more vulnerable. Damage to one node causes dysfunction of the entire organism as a whole, but its qualities are faster and more accurate.

Tubular The nervous system is characteristic of chordates; it includes features of diffuse and nodular types. The nervous system of higher animals took all the best: high reliability of the diffuse type, accuracy, locality, speed of organization of nodal type reactions.

The leading role of the nervous system

At the first stage of the development of the world of living beings, interaction between the simplest organisms was carried out through the aquatic environment of the primitive ocean, into which the chemical substances released by them entered. The first oldest form of interaction between the cells of a multicellular organism is chemical interaction through metabolic products entering the body fluids. Such metabolic products, or metabolites, are the breakdown products of proteins, carbon dioxide, etc. This is the humoral transmission of influences, the humoral mechanism of correlation, or connections between organs.

The humoral connection is characterized by the following features:

• lack of an exact address to which a chemical substance entering the blood or other body fluids is sent;
• the chemical spreads slowly;
• the chemical acts in minute quantities and is usually quickly broken down or eliminated from the body.

Humoral connections are common to both the animal and plant worlds. At a certain stage of development of the animal world, in connection with the appearance of the nervous system, a new, nervous form of connections and regulation is formed, which qualitatively distinguishes the animal world from the plant world. The higher the development of an animal’s organism, the greater the role played by the interaction of organs through the nervous system, which is designated as reflex. In higher living organisms, the nervous system regulates humoral connections. Unlike the humoral connection, the nervous connection has a precise direction to a specific organ and even a group of cells; communication is carried out hundreds of times faster than the speed of distribution of chemicals. The transition from a humoral connection to a nervous connection was not accompanied by the destruction of the humoral connection between the cells of the body, but by the subordination of nervous connections and the emergence of neurohumoral connections.

At the next stage of development of living beings, special organs appear - glands, in which hormones are produced, formed from food substances entering the body. The main function of the nervous system is both to regulate the activity of individual organs among themselves, and in the interaction of the body as a whole with its external environment. Any impact of the external environment on the body appears, first of all, on receptors (sensory organs) and is carried out through changes caused by the external environment and the nervous system. As the nervous system develops, its highest department—the cerebral hemispheres—becomes “the manager and distributor of all the activities of the body.”

Structure of the nervous system

The nervous system is formed by nervous tissue, which consists of a huge amount neurons- a nerve cell with processes.

The nervous system is conventionally divided into central and peripheral.

central nervous system includes the brain and spinal cord, and peripheral nervous system- nerves extending from them.

The brain and spinal cord are a collection of neurons. In a cross section of the brain, white and gray matter are distinguished. Gray matter consists of nerve cells, and white matter consists of nerve fibers, which are processes of nerve cells. In different parts of the central nervous system, the location of white and gray matter is different. In the spinal cord, gray matter is located inside, and white matter is outside, but in the brain (cerebral hemispheres, cerebellum), on the contrary, gray matter is outside, white matter is inside. In various parts of the brain there are separate clusters of nerve cells (gray matter) located inside the white matter - kernels. Clusters of nerve cells are also located outside the central nervous system. They're called nodes and belong to the peripheral nervous system.

Reflex activity of the nervous system

The main form of activity of the nervous system is the reflex. Reflex- the body’s reaction to changes in the internal or external environment, carried out with the participation of the central nervous system in response to irritation of receptors.

With any irritation, excitation from the receptors is transmitted along centripetal nerve fibers to the central nervous system, from where, through the interneuron along centrifugal fibers, it goes to the periphery to one or another organ, the activity of which changes. This entire path through the central nervous system to the working organ is called reflex arc usually formed by three neurons: sensory, intercalary and motor. A reflex is a complex act in which a significantly larger number of neurons take part. Excitation, entering the central nervous system, spreads to many parts of the spinal cord and reaches the brain. As a result of the interaction of many neurons, the body responds to irritation.

Spinal cord

Spinal cord- a cord about 45 cm long, 1 cm in diameter, located in the spinal canal, covered with three meninges: dura, arachnoid and soft (vascular).

Spinal cord is located in the spinal canal and is a cord that at the top passes into the medulla oblongata and at the bottom ends at the level of the second lumbar vertebra. The spinal cord consists of gray matter containing nerve cells and white matter consisting of nerve fibers. Gray matter is located inside the spinal cord and is surrounded on all sides by white matter.

In a cross section, the gray matter resembles the letter H. It distinguishes the anterior and posterior horns, as well as the connecting crossbar, in the center of which there is a narrow canal of the spinal cord containing cerebrospinal fluid. In the thoracic region there are lateral horns. They contain the bodies of neurons that innervate internal organs. The white matter of the spinal cord is formed by nerve processes. Short processes connect sections of the spinal cord, and long ones make up the conductive apparatus of bilateral connections with the brain.

The spinal cord has two thickenings - cervical and lumbar, from which nerves extend to the upper and lower extremities. 31 pairs of spinal nerves arise from the spinal cord. Each nerve begins from the spinal cord with two roots - anterior and posterior. Posterior roots - sensitive consist of processes of centripetal neurons. Their bodies are located in the spinal ganglia. Anterior roots - motor- are processes of centrifugal neurons located in the gray matter of the spinal cord. As a result of the fusion of the anterior and posterior roots, a mixed spinal nerve is formed. The spinal cord contains centers that regulate the simplest reflex acts. The main functions of the spinal cord are reflex activity and conduction of excitation.

The human spinal cord contains reflex centers for the muscles of the upper and lower extremities, sweating and urination. The function of excitation is that impulses from the brain to all areas of the body and back pass through the spinal cord. Centrifugal impulses from organs (skin, muscles) are transmitted through ascending pathways to the brain. Along descending pathways, centrifugal impulses are transmitted from the brain to the spinal cord, then to the periphery, to the organs. When the pathways are damaged, there is a loss of sensitivity in various parts of the body, a violation of voluntary muscle contractions and the ability to move.

Evolution of the vertebrate brain

The formation of the central nervous system in the form of a neural tube first appears in chordates. U lower chordates the neural tube persists throughout life, higher- vertebrates - in the embryonic stage, a neural plate is laid down on the dorsal side, which sinks under the skin and curls up into a tube. In the embryonic stage of development, the neural tube forms three swellings in the anterior part - three brain vesicles, from which parts of the brain develop: the anterior vesicle gives the forebrain and diencephalon, the middle vesicle turns into the midbrain, the posterior vesicle forms the cerebellum and medulla oblongata. These five brain regions are characteristic of all vertebrates.

For lower vertebrates- fish and amphibians - characterized by a predominance of the midbrain over other parts. U amphibians The forebrain enlarges somewhat and a thin layer of nerve cells forms in the roof of the hemispheres - the primary medullary vault, the ancient cortex. U reptiles The forebrain increases significantly due to accumulations of nerve cells. Most of the roof of the hemispheres is occupied by the ancient cortex. For the first time in reptiles, the rudiment of a new cortex appears. The hemispheres of the forebrain creep onto other parts, as a result of which a bend is formed in the region of the diencephalon. Beginning with ancient reptiles, the cerebral hemispheres became the largest part of the brain.

In the structure of the brain birds and reptiles much in common. On the roof of the brain is the primary cortex, the midbrain is well developed. However, in birds, compared to reptiles, the total brain mass and the relative size of the forebrain increase. The cerebellum is large and has a folded structure. U mammals the forebrain reaches its greatest size and complexity. Most of the brain matter is made up of the neocortex, which serves as the center of higher nervous activity. The intermediate and middle parts of the brain in mammals are small. The expanding hemispheres of the forebrain cover them and crush them under themselves. Some mammals have a smooth brain without grooves or convolutions, but most mammals have grooves and convolutions in the cerebral cortex. The appearance of grooves and convolutions occurs due to the growth of the brain with limited dimensions of the skull. Further growth of the cortex leads to the appearance of folding in the form of grooves and convolutions.

Brain

If the spinal cord in all vertebrates is developed more or less equally, then the brain differs significantly in size and complexity of structure in different animals. The forebrain undergoes particularly dramatic changes during evolution. In lower vertebrates, the forebrain is poorly developed. In fish, it is represented by the olfactory lobes and nuclei of gray matter in the thickness of the brain. The intensive development of the forebrain is associated with the emergence of animals onto land. It differentiates into the diencephalon and two symmetrical hemispheres, which are called telencephalon. Gray matter on the surface of the forebrain (cortex) first appears in reptiles, developing further in birds and especially in mammals. Truly large forebrain hemispheres become only in birds and mammals. In the latter, they cover almost all other parts of the brain.

The brain is located in the cranial cavity. It includes the brainstem and telencephalon (cerebral cortex).

Brain stem consists of the medulla oblongata, pons, midbrain and diencephalon.

Medulla is a direct continuation of the spinal cord and, expanding, passes into the hindbrain. It basically retains the shape and structure of the spinal cord. In the thickness of the medulla oblongata there are accumulations of gray matter - the nuclei of the cranial nerves. The rear axle includes cerebellum and pons. The cerebellum is located above the medulla oblongata and has a complex structure. On the surface of the cerebellar hemispheres, gray matter forms the cortex, and inside the cerebellum - its nuclei. Like the spinal medulla oblongata, it performs two functions: reflex and conductive. However, the reflexes of the medulla oblongata are more complex. This is reflected in its importance in the regulation of cardiac activity, the condition of blood vessels, respiration, and sweating. The centers of all these functions are located in the medulla oblongata. Here are the centers for chewing, sucking, swallowing, saliva and gastric juice. Despite its small size (2.5–3 cm), the medulla oblongata is a vital part of the central nervous system. Damage to it can cause death due to cessation of breathing and heart activity. The conductor function of the medulla oblongata and the pons is to transmit impulses from the spinal cord to the brain and back.

IN midbrain the primary (subcortical) centers of vision and hearing are located, which carry out reflexive orienting reactions to light and sound stimulation. These reactions are expressed in various movements of the torso, head and eyes towards the stimuli. The midbrain consists of the cerebral peduncles and quadrigeminalis. The midbrain regulates and distributes the tone (tension) of skeletal muscles.

Diencephalon consists of two departments - thalamus and hypothalamus, each of which consists of a large number of nuclei of the visual thalamus and subthalamic region. Through the visual thalamus, centripetal impulses are transmitted to the cerebral cortex from all receptors of the body. Not a single centripetal impulse, no matter where it comes from, can pass to the cortex, bypassing the visual hillocks. Thus, through the diencephalon, all receptors communicate with the cerebral cortex. In the subtubercular region there are centers that influence metabolism, thermoregulation and endocrine glands.

Cerebellum located behind the medulla oblongata. It consists of gray and white matter. However, unlike the spinal cord and brainstem, the gray matter - the cortex - is located on the surface of the cerebellum, and the white matter is located inside, under the cortex. The cerebellum coordinates movements, makes them clear and smooth, plays an important role in maintaining the balance of the body in space, and also influences muscle tone. When the cerebellum is damaged, a person experiences a decrease in muscle tone, movement disorders and changes in gait, speech slows down, etc. However, after some time, movement and muscle tone are restored due to the fact that the intact parts of the central nervous system take over the functions of the cerebellum.

Large hemispheres- the largest and most developed part of the brain. In humans, they form the bulk of the brain and are covered with cortex over their entire surface. Gray matter covers the outside of the hemispheres and forms the cerebral cortex. The human cerebral cortex has a thickness of 2 to 4 mm and is composed of 6–8 layers formed by 14–16 billion cells, different in shape, size and functions. Under the cortex is a white substance. It consists of nerve fibers connecting the cortex with the lower parts of the central nervous system and the individual lobes of the hemispheres with each other.

The cerebral cortex has convolutions separated by grooves, which significantly increase its surface. The three deepest grooves divide the hemispheres into lobes. Each hemisphere has four lobes: frontal, parietal, temporal, occipital. Excitation of different receptors enters the corresponding perceptive areas of the cortex, called zones, and from here they are transmitted to a specific organ, prompting it to action. The following zones are distinguished in the cortex. Auditory zone located in the temporal lobe, receives impulses from auditory receptors.

Visual area lies in the occipital region. Impulses from the eye receptors arrive here.

Olfactory zone located on the inner surface of the temporal lobe and is associated with receptors in the nasal cavity.

Sensory-motor the zone is located in the frontal and parietal lobes. This zone contains the main centers of movement of the legs, torso, arms, neck, tongue and lips. This is also where the center of speech lies.

The cerebral hemispheres are the highest division of the central nervous system, controlling the functioning of all organs in mammals. The importance of the cerebral hemispheres in humans also lies in the fact that they represent the material basis of mental activity. I.P. Pavlov showed that mental activity is based on physiological processes occurring in the cerebral cortex. Thinking is associated with the activity of the entire cerebral cortex, and not just with the function of its individual areas.

Cerebral cortex

Surface cerebral cortex in humans it is about 1500 cm 2, which is many times greater than the inner surface of the skull. This large surface of the cortex was formed due to the development of a large number of grooves and convolutions, as a result of which most of the cortex (about 70%) is concentrated in the grooves. The largest grooves of the cerebral hemispheres are central, which runs across both hemispheres, and temporal, separating the temporal lobe from the rest. The cerebral cortex, despite its small thickness (1.5–3 mm), has a very complex structure. It has six main layers, which differ in the structure, shape and size of neurons and connections. The cortex contains the centers of all sensory (receptor) systems, representatives of all organs and parts of the body. In this regard, centripetal nerve impulses from all internal organs or parts of the body approach the cortex, and it can control their work. Through the cerebral cortex, conditioned reflexes are closed, through which the body constantly, throughout life, very accurately adapts to the changing conditions of existence, to the environment.

A person learns about this even in his school years. Biology lessons provide general information about the body in general and individual organs in particular. As part of the school curriculum, children learn that the normal functioning of the body depends on the state of the nervous system. When malfunctions occur in it, the work of other organs is also disrupted. There are various factors that, to one degree or another, influence this influence. Nervous system characterized as one of the most important parts of the body. It determines the functional unity of a person’s internal structures and the connection of the body with the external environment. Let's take a closer look at what it is

Structure

To understand what the nervous system is, it is necessary to study all its elements separately. The structural unit is a neuron. It is a cell with processes. Neurons form circuits. Speaking about what the nervous system is, it should also be said that it consists of two sections: central and peripheral. The first includes the spinal cord and brain, the second includes the nerves and nodes extending from them. Conventionally, the nervous system is divided into autonomic and somatic.

Cells

They are divided into 2 large groups: afferent and efferent. Activity of the nervous system starts with receptors. They perceive light, sound, smells. Efferent - motor - cells generate and direct impulses to certain organs. They consist of a body and a nucleus, numerous processes called dendrites. A fiber is isolated - an axon. Its length can be 1-1.5 mm. Axons ensure the transmission of impulses. The membranes of cells responsible for the perception of smell and taste contain special compounds. They react to certain substances by changing their state.

Vegetative department

Activity of the nervous system ensures the functioning of internal organs, glands, lymphatic and blood vessels. To a certain extent, it also determines the functioning of muscles. The autonomic system is divided into parasympathetic and sympathetic divisions. The latter ensures dilation of the pupil and small bronchi, increased blood pressure, increased heart rate, etc. The parasympathetic department is responsible for the functioning of the genital organs, bladder, and rectum. Impulses emanate from it, activating other glossopharyngeal, for example). The centers are located in the brain stem and sacral part of the spinal cord.

Pathologies

Diseases of the autonomic system can be caused by various factors. Quite often, disorders are a consequence of other pathologies, such as head injury, poisoning, and infections. Failures in the autonomic system can be caused by a lack of vitamins and frequent stress. Often diseases are “masked” by other pathologies. For example, if the functioning of the thoracic or cervical nodes of the trunk is impaired, pain in the sternum is noted, radiating to the shoulder. Such symptoms are typical for heart disease, so patients often confuse the pathologies.

Spinal cord

Outwardly, it resembles a heavy metal. The length of this section in an adult is about 41-45 cm. There are two thickenings in the spinal cord: lumbar and cervical. The so-called innervation structures of the lower and upper extremities are formed in them. The following sections are distinguished: sacral, lumbar, thoracic, cervical. Throughout its entire length it is covered with soft, hard and arachnoid membranes.

Brain

It is located in the skull. The brain consists of the right and left hemispheres, brainstem and cerebellum. It has been established that its weight is greater in men than in women. The brain begins its development in the embryonic period. The organ reaches its actual size by about 20 years of age. Towards the end of life, the weight of the brain decreases. It contains departments:

1. Finite.
2. Intermediate.
3. Average.
4. Rear.
5. Oblong.

Hemispheres

They also contain an olfactory center. The outer shell of the hemispheres has a rather complex pattern. This is due to the presence of ridges and grooves. They form something like "convolutions". Each person's drawing is individual. However, there are several grooves that are the same for everyone. They allow us to distinguish five lobes: frontal, parietal, occipital, temporal and hidden.

Unconditioned reflexes

Nervous system processes- response to stimuli. Unconditioned reflexes were studied by such a prominent Russian scientist as I.P. Pavlov. These reactions are focused mainly on the self-preservation of the body. The main ones are food, orientation, and defensive. Unconditioned reflexes are innate.

Classification

Unconditioned reflexes were studied by Simonov. The scientist identified 3 classes of innate reactions corresponding to the development of a specific area of ​​the environment:

Orienting reflex

It is expressed in involuntary sensory attention, accompanied by an increase in muscle tone. The reflex is triggered by a new or unexpected stimulus. Scientists call this reaction “wariness,” anxiety, or surprise. There are three phases of its development:

1. Stopping the current activity, fixing the posture. Simonov calls this general (preventive) inhibition. It occurs upon the appearance of any stimulus with an unknown signal.
2. Transition to the “activation” reaction. At this stage, the body is put into reflexive readiness for a likely encounter with an emergency situation. This manifests itself in a general increase in muscle tone. At this phase, a multicomponent reaction takes place. It involves turning the head and eyes towards the stimulus.
3. Fixing the stimulus field to begin differentiated analysis of signals and select a response.

Meaning

The orienting reflex is part of the structure of exploratory behavior. This is especially evident in a new environment. Research activities can be focused both on mastering novelty and on searching for an object that can satisfy curiosity. In addition, it can also provide analysis of the significance of the stimulus. In such a situation, there is an increase in the sensitivity of the analyzers.

Mechanism

The implementation of the orientation reflex is a consequence of the dynamic interaction of many formations of nonspecific and specific elements of the central nervous system. The general activation phase, for example, is associated with the launch and onset of generalized excitation of the cortex. When analyzing a stimulus, cortical-limbic-thalamic integration is of primary importance. The hippocampus plays an important role in this.

Conditioned reflexes

At the turn of the 19th-20th centuries. Pavlov, who studied the work of the digestive glands for a long time, revealed the following phenomenon in experimental animals. An increase in the secretion of gastric juice and saliva occurred regularly not only when food entered the gastrointestinal tract directly, but also when waiting for it to be received. At that time, the mechanism of this phenomenon was not known. Scientists explained it by “mental stimulation” of the glands. In subsequent studies, Pavlov classified this reaction as a conditioned (acquired) reflex. They can appear and disappear during a person's life. For a conditioned reaction to occur, two stimuli must coincide. One of them, under any conditions, provokes a natural response - an unconditioned reflex. The second, due to its routineness, does not provoke any reaction. It is defined as indifferent (indifferent). For a conditioned reflex to occur, the second stimulus must begin to act earlier than the unconditioned one, by several seconds. In this case, the biological significance of the first should be less.

Nervous system protection

As you know, the body is affected by a variety of factors. State of the nervous system affects the functioning of other organs. Even seemingly insignificant failures can cause serious illnesses. However, they will not always be associated with the activity of the nervous system. In this regard, great attention should be paid to preventive measures. First of all, it is necessary to reduce irritating factors. It is known that constant stress and anxiety are one of the causes of heart pathologies. Treatment of these diseases includes not only medications, but also physiotherapy, exercise therapy, etc. Diet is of particular importance. The condition of all human systems and organs depends on proper nutrition. Food must contain sufficient amounts of vitamins. Experts recommend including plant foods, herbs, vegetables and fruits in your diet.

Vitamin C

It has a beneficial effect on all body systems, including the nervous system. Vitamin C ensures energy production at the cellular level. This compound is involved in the synthesis of ATP (adenosine triphosphoric acid). Vitamin C is considered one of the strongest antioxidants; it neutralizes the negative effects of free radicals by binding them. In addition, the substance can enhance the activity of other antioxidants. These include vitamin E and selenium.

Lecithin

It ensures the normal course of processes in the nervous system. Lecithin is an essential nutrient for cells. The content in the peripheral region is about 17%, in the brain - 30%. With insufficient lecithin intake, nervous exhaustion occurs. The person becomes irritable, which often leads to nervous breakdowns. Lecithin is necessary for all cells of the body. It is included in the group of B-vitamins and promotes energy production. In addition, lecithin is involved in the production of acetylcholine.

Music that calms the nervous system

As mentioned above, for diseases of the central nervous system, treatment measures may include not only taking medications. The therapeutic course is selected depending on the severity of the disorders. Meanwhile, relaxation of the nervous system This can often be achieved without visiting a doctor. A person can independently find ways to relieve irritation. For example, there are different melodies. As a rule, these are slow compositions, often without words. However, some people may find marching to be calming. When choosing melodies, you should focus on your own preferences. You just need to make sure that the music is not depressing. Today, a special relaxing genre has become quite popular. It combines classics and folk melodies. The main sign of relaxing music is quiet monotony. It “envelops” the listener, creating a soft but durable “cocoon” that protects a person from external irritations. Relaxation music can be classical, but not symphonic. It is usually performed by one instrument: piano, guitar, violin, flute. It can also be a song with a repetitive chant and simple words.

The sounds of nature are very popular - the rustling of leaves, the sound of rain, birdsong. In combination with the melody of several instruments, they take a person away from the everyday hustle and bustle, the rhythm of the metropolis, and relieve nervous and muscle tension. When listening, thoughts are organized, excitement is replaced by calm.