The name of the organs of the nervous system. What is the human nervous system made of? Segmental structure of the spinal cord

Nervous system is the basis for all types of interaction of 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 dendrites and a long axon.

The human nervous system can be conditionally divided into CENTRAL and PERIPHERAL, and also separately distinguished autonomic nervous system, which has its representation both in the departments of the central and in the departments of the 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,
cerebral brainstem,
cerebellum.

Cerebral hemispheres divided into frontal lobes, parietal, temporal and occipital lobes. The cerebral hemispheres are connected through the corpus callosum.
- The frontal lobes are responsible for the intellectual and emotional sphere, thinking and complex behavior, conscious movement, motor speaking 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 the formation of memory, influence on the emotional background, for influencing the autonomic nervous system through communication with the limbic system.
- The parietal lobes are responsible for various types of sensitivity (tactile, painful 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 varoli and medulla oblongata. Brain stem functions are responsible for unconditioned reflexes, influence on the extrapyramidal system, gustatory, visual, auditory and vestibular reflexes, the 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 worm that connects the cerebellar hemispheres. Both the cerebral hemispheres and the cerebellar hemispheres are lined 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 worm is responsible for maintaining balance and posture, muscle tone. The cerebellum also affects the autonomic nervous system. In the brain there are four ventricles, in the system of which the cerebrospinal fluid circulates and which are connected with the subarachnoid space of the cranial cavity and the spinal canal.

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

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 the axons run, the long processes of neurons covered with myelin. In the brain, the gray matter is located mainly in the cortex of the cerebral hemispheres, in the basal nuclei of the hemispheres and nuclei of the brain stem (midbrain, pons and medulla oblongata), and in the spinal cord, the 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, which are controlled by parts of the central nervous system.

Autonomic nervous system divided 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 sympathetic, parasympathetic and metasympathetic nervous systems. The sympathetic and parasympathetic nervous systems are also divided into central and peripheral. The central sections of the parasympathetic nervous system are located in the midbrain and medulla oblongata, while the central sections 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.).

The human nervous system is an important part of the body, which is responsible for many of the processes that take place. Her diseases have a bad effect on the human condition. It regulates the activity and interaction of all systems and organs. With the current environmental background and constant stress, it is necessary to pay serious attention to the daily regimen and proper nutrition in order to avoid potential health problems.

general information

The nervous system influences the functional interaction of all human systems and organs, as well as the connection of the body with the outside world. Its structural unit - a neuron - is a cell with specific processes. Neural circuits are built from these elements. The nervous system is subdivided into central and peripheral. The first includes the brain and spinal cord, and the second includes all the nerves and nerve nodes extending from them.

Somatic nervous system

In addition, the nervous system is divided into somatic and autonomic. The somatic system is responsible for the interaction of the body with the outside world, for the ability to move independently and for sensitivity, which is provided with the help of the senses and some nerve endings. A person's ability to move is ensured by the control of skeletal and muscle mass, which is carried out with the help of the nervous system. Scientists also call this system animal, since only animals can move and have sensitivity.

Autonomic nervous system

This system is responsible for the internal state of the body, that is, for:

The human autonomic nervous system, in turn, is divided into sympathetic and parasympathetic. The first is responsible for the pulse, blood pressure, bronchi, and so on. Its work is controlled by the spinal centers, from which there are sympathetic fibers located in the lateral horns. The parasympathetic is responsible for the work of the bladder, rectum, genitals and for a number of nerve endings. This multifunctionality of the system is explained by the fact that its work is carried out both with the help of the sacral part of the brain and through its trunk. The control of these systems is carried out by specific autonomic devices that are located in the brain.

Diseases

The human nervous system is extremely susceptible to outside influence, there are a variety of reasons that can cause its diseases. Most often, the vegetative system suffers from the weather, while a person can feel bad both in too hot time and in cold winter. There are a number of characteristic symptoms for these diseases. For example, a person blushes or turns pale, their pulse quickens, or excessive sweating begins. In addition, such diseases can be acquired.

How do these diseases appear

They can develop due to head trauma or arsenic, as well as from a complex and dangerous infectious disease. Such diseases can also develop due to overwork, due to a lack of vitamins, with mental disorders or constant stress.

You also need to be careful under hazardous working conditions, which can also affect the development of diseases of the autonomic nervous system. In addition, such diseases can be disguised as others, some of them resemble heart disease.

central nervous system

It is formed from two elements: the spinal cord and the brain. The first of them looks like a cord, slightly flattened in the middle. In an adult, its size varies from 41 to 45 cm, and its weight reaches only 30 grams. The spinal cord is completely surrounded by membranes that are located in a specific channel. The thickness of the spinal cord does not change along its entire length, except for two places called the cervical and lumbar thickenings. It is here that the nerves of the upper as well as the lower extremities are formed. It is subdivided into sections such as cervical, lumbar, thoracic, and sacral.

Brain

It is located in the human skull and is divided into two parts: the left and right hemispheres. In addition to these parts, the trunk and cerebellum are also isolated. Biologists have determined that the brain of an adult man is 100 mg heavier than a woman's. This is due solely to the fact that all parts of the body of the stronger sex are more female in physical parameters due to evolution.

The fetal brain begins to actively grow even before birth, in the womb. It stops its development only when a person reaches 20 years old. In addition, in old age, towards the end of life, it becomes a little lighter.

Departments of the brain

There are five main divisions of the brain:

In the event of a traumatic brain injury, the central nervous system of a person can be seriously damaged, and this has a bad effect on the person's mental state. With such violations, patients may have voices in the head, which are not so easy to get rid of.

Meninges of the brain

Three types of membranes cover the brain and spinal cord:

• The hard membrane covers the outside of the spinal cord. It is very similar in shape to a bag. It also functions as the periosteum of the skull.
• The arachnoid membrane is a substance that practically adheres to a solid. Neither the hard nor the arachnoid membrane contains blood vessels.
• The pia mater is a collection of nerves and blood vessels that feed both brains.

Brain functions

This is a very complex part of the body, on which the entire human nervous system depends. Even considering that a huge number of scientists are studying the problems of the brain, all of its functions have not yet been fully studied. The most difficult riddle for science is the study of the features of the visual system. It is still unclear how and with what parts of the brain we have the ability to see. People who are far from science mistakenly believe that this happens exclusively with the help of the eyes, but this is absolutely not the case.

Scientists studying this issue believe that the eyes only perceive signals that are sent by the surrounding world, and in turn transmit them to the brain. Receiving a signal, it creates a visual picture, that is, in fact, we see what our brain shows. The same happens with hearing, in fact, the ear only perceives sound signals received through the brain.

Output

Currently, diseases of the vegetative system are very common in the younger generation. This is due to many factors, such as poor environmental conditions, improper daily routine, or irregular and inappropriate nutrition. To avoid such problems, it is recommended to carefully monitor your routine, avoid various stresses and overwork. After all, the health of the central nervous system is responsible for the state of the whole organism, otherwise such problems can provoke serious disruptions in the work of other important organs.

NERVOUS SYSTEM
a complex network of structures that permeates the entire body and provides self-regulation of its vital activity due to the ability to respond to external and internal influences (stimuli). The main functions of the nervous system are receiving, storing and processing information from the external and internal environment, regulation and coordination of the activities of all organs and organ systems. In humans, as in all mammals, the nervous system includes three main components: 1) nerve cells (neurons); 2) glial cells associated with them, in particular neuroglia cells, as well as cells that form neurilemma; 3) connective tissue. Neurons provide the conduction of nerve impulses; neuroglia performs supporting, protective and trophic functions both in the brain and in the spinal cord, and neurilemma, consisting mainly of specialized, so-called. Schwann cells, participates in the formation of the sheaths of the fibers of the peripheral nerves; connective tissue supports and binds together the various parts of the nervous system. The human nervous system is subdivided in different ways. Anatomically, it consists of the central nervous system (CNS) and the peripheral nervous system (PNS). The central nervous system includes the brain and spinal cord, and the PNS, which provides communication between the central nervous system and various parts of the body, includes the cranial and spinal nerves, as well as the nerve nodes (ganglia) and nerve plexuses lying outside the spinal cord and brain.

Neuron. The structural and functional unit of the nervous system is a nerve cell - a neuron. It is estimated that there are over 100 billion neurons in the human nervous system. A typical neuron consists of a body (i.e., the nuclear part) and processes, one usually unbranching process, an axon, and several branching ones - dendrites. The impulses travel along the axon from the cell body to the muscles, glands or other neurons, while along the dendrites they enter the cell body. In a neuron, as in other cells, there is a nucleus and a number of the smallest structures - organelles (see also CELL). These include the endoplasmic reticulum, ribosomes, Nissl corpuscles (tigroid), mitochondria, Golgi complex, lysosomes, filaments (neurofilaments and microtubules).

The central nervous system consists of the brain and spinal cord and their protective membranes. The outermost is the dura mater, underneath is the arachnoid (arachnoid), and then the pia mater, fused to the surface of the brain. Between the pia mater and the arachnoid is the subarachnoid (subarachnoid) space containing the cerebrospinal fluid, in which both the brain and spinal cord literally float. The action of the buoyant force of the liquid leads to the fact that, for example, the brain of an adult, weighing on average 1500 g, inside the skull actually weighs 50-100 g. The cerebral membranes and cerebrospinal fluid also play the role of shock absorbers that soften all kinds of shocks and shocks that experiences the body and which could damage the nervous system. The central nervous system is formed from gray and white matter. Gray matter is made up of cell bodies, dendrites and unmyelinated axons, organized into complexes that include countless synapses and serve as information processing centers, providing many functions of the nervous system. White matter consists of myelinated and unmyelinated axons, which act as conductors that transmit impulses from one center to another. Glia cells are also part of the gray and white matter. The neurons of the central nervous system form many circuits that perform two main functions: they provide reflex activity, as well as complex information processing in the higher brain centers. These higher centers, such as the visual cortex (visual cortex), receive incoming information, process it and transmit a response signal along the axons. The result of the activity of the nervous system is this or that activity, which is based on the contraction or relaxation of muscles or the secretion or cessation of the secretion of glands. It is with the work of muscles and glands that any way of our self-expression is associated. The incoming sensory information is processed, passing through a sequence of centers connected by long axons, which form specific pathways, for example, painful, visual, auditory. Sensory (ascending) pathways go in an ascending direction to the centers of the brain. Motor (descending) pathways connect the brain to the motor neurons of the cranial and spinal nerves. Pathways are usually organized in such a way that information (for example, painful or tactile) from the right side of the body enters the left side of the brain and vice versa. This rule also applies to the descending motor paths: the right half of the brain controls the movements of the left half of the body, and the left half controls the movement of the right. There are, however, a few exceptions to this general rule. The brain consists of three main structures: the cerebral hemispheres, the cerebellum, and the trunk. The large hemispheres - the largest part of the brain - contain the higher nerve centers that form the basis of consciousness, intelligence, personality, speech, understanding. In each of the large hemispheres, the following formations are distinguished: lying in the depth, isolated clusters (nuclei) of gray matter, which contain many important centers; located above them a large mass of white matter; covering the hemispheres from the outside is a thick layer of gray matter with numerous convolutions, which makes up the cerebral cortex. The cerebellum also consists of a deep gray matter, an intermediate array of white matter and an outer thick layer of gray matter that forms many convolutions. The cerebellum provides mainly coordination of movements. The brain stem is formed by a mass of gray and white matter, not divided into layers. The trunk is closely connected with the cerebral hemispheres, cerebellum and spinal cord and contains numerous centers of sensory and motor pathways. The first two pairs of cranial nerves depart from the cerebral hemispheres, while the remaining ten pairs - from the trunk. The trunk regulates vital functions such as breathing and circulation.
see also HUMAN BRAIN.
Spinal cord. The spinal cord located inside the spinal column and protected by its bone tissue has a cylindrical shape and is covered with three membranes. In cross section, the gray matter has the shape of the letter H or a butterfly. The gray matter is surrounded by white matter. The sensory fibers of the spinal nerves end in the dorsal (posterior) sections of the gray matter - the posterior horns (at the ends of the H facing the back). The bodies of the motor neurons of the spinal nerves are located in the ventral (anterior) sections of the gray matter - the anterior horns (at the ends of the H, remote from the back). In the white matter, there are ascending sensory pathways ending in the gray matter of the spinal cord, and the descending motor paths coming from the gray matter. In addition, many fibers in the white matter bind different parts of the gray matter of the spinal cord.
PERIPHERAL NERVOUS SYSTEM
PNS provides two-way communication of the central parts of the nervous system with organs and systems of the body. Anatomically, the PNS is represented by cranial (cranial) and spinal nerves, as well as a relatively autonomous enteric nervous system localized in the intestinal wall. All cranial nerves (12 pairs) are divided into motor, sensory, or mixed. The motor nerves begin in the motor nuclei of the trunk, formed by the bodies of the motor neurons themselves, and the sensory nerves are formed from the fibers of those neurons whose bodies lie in the ganglia outside the brain. 31 pairs of spinal nerves depart from the spinal cord: 8 pairs of cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal. They are designated in accordance with the position of the vertebrae adjacent to the intervertebral foramen, from which these nerves exit. Each spinal nerve has anterior and posterior roots, which merge to form the nerve itself. The dorsal spine contains sensitive fibers; it is closely associated with the spinal ganglion (dorsal root ganglion), which consists of the bodies of neurons, the axons of which form these fibers. The anterior root consists of motor fibers formed by neurons, whose cell bodies lie in the spinal cord.
VEGETATIVE NERVOUS SYSTEM
The vegetative, or autonomic, nervous system regulates the activity of the involuntary muscles, heart muscle, and various glands. Its structures are located both in the central nervous system and in the peripheral. The activity of the autonomic nervous system is aimed at maintaining homeostasis, i.e. a relatively stable state of the internal environment of the body, for example, a constant body temperature or blood pressure corresponding to the needs of the body. Signals from the central nervous system go to the working (effector) organs through pairs of neurons connected in series. The bodies of the first level neurons are located in the central nervous system, and their axons end in the autonomic ganglia lying outside the central nervous system, and here they form synapses with the bodies of the second level neurons, the axons of which are in direct contact with the effector organs. The first neurons are called preganglionic, the second - postganglionic. In that part of the autonomic nervous system, which is called the sympathetic, the bodies of preganglionic neurons are located in the gray matter of the thoracic (thoracic) and lumbar (lumbar) spinal cord. Therefore, the sympathetic system is also called thoraco-lumbar. The axons of her preganglionic neurons terminate and form synapses with postganglionic neurons in the ganglia located in a chain along the spine. Axons of postganglionic neurons are in contact with effector organs. The endings of postganglionic fibers secrete norepinephrine (a substance close to adrenaline) as a neurotransmitter, and therefore the sympathetic system is also defined as adrenergic. The sympathetic system is complemented by the parasympathetic nervous system. The bodies of her preganglinar neurons are located in the brain stem (intracranially, i.e. inside the skull) and the sacral (sacral) part of the spinal cord. Therefore, the parasympathetic system is also called cranio-sacral. The axons of the preganglionic parasympathetic neurons terminate and form synapses with postganglionic neurons in the ganglia located near the working organs. The endings of the postganglionic parasympathetic fibers secrete the neurotransmitter acetylcholine, on the basis of which the parasympathetic system is also called cholinergic. As a rule, the sympathetic system stimulates those processes that are aimed at mobilizing the body's forces in extreme situations or under stress. The parasympathetic system contributes to the accumulation or restoration of the body's energy resources. The reactions of the sympathetic system are accompanied by a waste of energy resources, an increase in the frequency and strength of heart contractions, an increase in blood pressure and blood sugar, as well as an increase in blood flow to skeletal muscles by reducing its flow to internal organs and skin. All of these changes are characteristic of the "fear, flight, or fight" response. The parasympathetic system, on the other hand, reduces the heart rate and strength of the heart, lowers blood pressure, and stimulates the digestive system. The sympathetic and parasympathetic systems act in a coordinated manner and should not be considered antagonistic. Together they support the functioning of internal organs and tissues at a level corresponding to the intensity of stress and the emotional state of a person. Both systems operate continuously, but their levels of activity fluctuate depending on the situation.
REFLEXES
When an adequate stimulus acts on the receptor of a sensory neuron, a burst of impulses arises in it, triggering a response called a reflex act (reflex). Reflexes underlie most of the manifestations of the vital activity of our body. The reflex act is carried out by the so-called. reflex arc; this term denotes the path of transmission of nerve impulses from the point of initial stimulation on the body to the organ that performs a response action. The arc of the reflex that causes the contraction of the skeletal muscle consists of at least two neurons: the sensory, whose body is located in the ganglion, and the axon forms a synapse with the neurons of the spinal cord or brain stem, and the motor (lower, or peripheral, motor neuron), the body of which is located in the gray matter, and the axon ends with a motor end plate on skeletal muscle fibers. A third, intermediate, neuron located in the gray matter can also be included in the reflex arc between the sensory and motor neurons. The arcs of many reflexes contain two or more intermediate neurons. Reflex actions are carried out involuntarily, many of them are not realized. The knee reflex, for example, is triggered by tapping the tendon of the quadriceps muscle in the knee area. This is a two-neural reflex, its reflex arc consists of muscle spindles (muscle receptors), a sensory neuron, a peripheral motor neuron, and muscle. Another example is reflexive withdrawal of the hand from a hot object: the arc of this reflex includes a sensitive neuron, one or more intermediate neurons in the gray matter of the spinal cord, a peripheral motor neuron, and a muscle. Many reflex acts have a much more complex mechanism. The so-called intersegmental reflexes consist of combinations of simpler reflexes, in the implementation of which many segments of the spinal cord take part. Thanks to such reflexes, for example, coordination of movements of the arms and legs when walking is ensured. Complex reflexes that are closed in the brain include movements associated with maintaining balance. Visceral reflexes, i.e. reflex reactions of internal organs, mediated by the autonomic nervous system; they allow the emptying of the bladder and many processes in the digestive system.
see also REFLEX.
DISEASES OF THE NERVOUS SYSTEM
Damage to the nervous system occurs in organic diseases or injuries of the brain and spinal cord, meninges, peripheral nerves. Diagnostics and treatment of diseases and injuries of the nervous system are the subject of a special branch of medicine - neurology. Psychiatry and clinical psychology deal mainly with mental disorders. The areas of these medical disciplines often overlap. See individual diseases of the nervous system: ALZHEIMER'S DISEASE;
STROKE ;
Meningitis;
NOT BELIEVE;
PARALYCH;
PARKINSON'S DISEASE;
POLIOMYELITIS;
MULTIPLE SCLEROSIS ;
TETANUS;
CEREBRAL PALSY ;
Chorea;
ENCEPHALIT;
EPILEPSY.
see also
ANATOMY COMPARATIVE;
HUMAN ANATOMY .
LITERATURE
Bloom F., Leiserson A., Hofstedter L. Brain, Mind and Behavior. M., 1988 Human Physiology, ed. R. Schmidt, G. Tevs, t. 1. M., 1996

Collier's Encyclopedia. - Open Society. 2000 .

There are several systems in the human body, including the digestive, cardiovascular, and muscular. The nervous one deserves special attention - it makes the human body move, react to irritating factors, see and think.

The human nervous system is a set of structures that performs the function of regulation of absolutely all parts of the body, is responsible for movement and sensitivity.

In contact with

Types of the human nervous system

Before answering the question of interest to people: "how does the nervous system work", it is necessary to figure out what it actually consists of and what its components are usually divided into in medicine.

With the types of NS, not everything is so unambiguous - it is classified according to several parameters:

• localization area;
• type of management;
• method of transferring information;
• functional affiliation.

Localization area

The human nervous system in the area of ​​localization is central and peripheral... The first is represented by the brain and bone marrow, and the second consists of nerves and the autonomic network.

The central nervous system performs the functions of regulation by all internal and external organs. She makes them interact with each other. Peripheral is called the one that, due to anatomical features, is located outside the spinal cord and brain.

How does the nervous system work? The PNS reacts to irritating factors by sending signals to the spinal cord and then to the brain. After that, the organs of the central nervous system process them and again send signals to the PNS, which sets, for example, the muscles of the leg in motion.

Information transfer method

According to this principle, there are reflex and neurohumoral systems... The first is the spinal cord, which, without the participation of the brain, is capable of responding to stimuli.

Interesting! The person does not control the reflex function, since the spinal cord makes decisions on its own. For example, when you touch in a hot surface, your hand immediately withdraws, and at the same time you did not even think to make this movement - your reflexes worked.

Neurohumoral, to which the brain belongs, must initially process information, you can control this process. The signals are then sent to the PNS, which carries out the commands of your brain center.

Functional affiliation

Speaking about parts of the nervous system, one cannot fail to mention the autonomic, which in turn is divided into sympathetic, somatic and parasympathetic.

The vegetative system (ANS) is the department that is responsible for regulation of the work of lymph nodes, blood vessels, organs and glands(external and internal secretion).

The somatic system is a collection of nerves that are found in bones, muscles, and skin. It is they who react to all environmental factors and send data to the brain center, and then follow its orders. Every muscle movement is controlled by somatic nerves.

Interesting! The right side of the nerves and muscles is controlled by the left hemisphere, and the left is controlled by the right.

The sympathetic system is responsible for the release of adrenaline into the blood, controls the work of the heart, lungs and the supply of nutrients to all parts of the body. In addition, it regulates body saturation.

The parasympathetic is responsible for reducing the frequency of movements, also controls the functioning of the lungs, some glands, and the iris. An equally important task is the regulation of digestion.

Control type

Another clue to the question "how does the nervous system work" can be provided by a convenient classification by type of control. It is divided into higher and lower activities.

Higher activity controls behavior in the environment. All intellectual and creative activity also belongs to the highest.

The lowest activity is the regulation of all functions within the human body. This type of activity makes all body systems a single whole.

The structure and functions of the NS

We have already figured out that the entire NS should be divided into peripheral, central, vegetative and all of the above, but there is still much to be said about their structure and functions.

Spinal cord

This body is located in the spinal canal and in fact is a kind of "rope" of nerves. It is divided into gray and white matter, where the former is completely covered by the latter.

Interesting! In the section, it is noticeable that the gray matter is woven from nerves in such a way that it resembles a butterfly. That is why it is often called "butterfly wings".

Total the spinal cord consists of 31 sections, each of which is responsible for a different group of nerves that control specific muscles.

The spinal cord, as already mentioned, can work without the participation of the brain - we are talking about reflexes that do not lend themselves to regulation. In the same turn, it is under the control of the organ of thinking and performs a conductive function.

Brain

This body is the least studied, many of its functions still raise many questions in scientific circles. It is divided into five sections:

• large hemispheres (forebrain);
• intermediate;
• oblong;
• rear;
• average.

The first section makes up 4/5 of the entire mass of the organ. He is responsible for sight, smell, movement, thinking, hearing, sensitivity. The medulla oblongata is an incredibly important center that regulates processes such as heartbeat, breathing, protective reflexes, secretion of gastric juice and others.

The middle department oversees a function such as. The intermediate plays a role in shaping the emotional state. There are also centers responsible for thermoregulation and metabolism in the body.

The structure of the brain

Nerve structure

NS is a collection of billions of specific cells. To understand how the nervous system works, you need to talk about its structure.

A nerve is a structure that is made up of a certain number of fibers. Those, in turn, consist of axons - they are the conductors of all impulses.

The number of fibers in one nerve can differ significantly. Usually it is about one hundred, but there are more than 1.5 million fibers in the human eye.

The axons themselves are covered with a special shell, which significantly increases the signal speed - this allows a person to react to stimuli almost instantly.

The nerves themselves are also different, and therefore they are classified into the following types:

• motor (transmit information from the central nervous system to the muscular system);
• cranial (this includes the optic, olfactory and other types of nerves);
• sensitive (transmit information from the PNS to the central nervous system);
• dorsal (located in and control parts of the body);
• mixed (capable of transmitting information in two directions).

The structure of the nerve trunk

We have already figured out such topics as "Types of the human nervous system" and "How the nervous system works", but there are many interesting facts that are worth mentioning:

1. The number in our body is greater than the number of people on the entire planet Earth.
2. The brain contains about 90-100 billion neurons. If all of them are connected in one line, then it will reach about 1 thousand km.
3. The speed of the impulses reaches almost 300 km / h.
4. After the onset of puberty, the mass of the organ of thinking every year decreases by about one gram.
5. In men, the brain is about 1/12 larger than that of a woman.
6. The largest organ of thinking was recorded in a mentally ill person.
7. The cells of the central nervous system are practically unrecoverable, and severe stress and excitement can seriously reduce their number.
8. Until now, science has not determined by what percentage we use our main thinking organ. There are well-known myths that no more than 1%, and geniuses - no more than 10%.
9. The size of the organ of thinking is not at all does not affect mental performance... Previously, it was believed that men are smarter than the fair sex, but this statement was refuted at the end of the twentieth century.
10. Alcoholic beverages strongly suppress the function of synapses (the place of contacts between neurons), which at times slows down thought and motor processes.

We learned what the human nervous system is - it is a complex collection of billions of cells that interact with each other at a speed equal to the movement of the fastest cars in the world.

Among many types of cells, these are the most difficult to restore, and some of their subspecies are not at all amenable to restoration. That is why they are perfectly protected by the skull and vertebral bones.

It is also interesting that NS diseases are the least treatable. Modern medicine is basically only able to slow down cell death, but it is impossible to stop this process... Many other types of cells with the help of special preparations can be protected from destruction for many years - for example, liver cells. At this time, the cells of the epidermis (skin) are able to regenerate in a matter of days or weeks to their previous state.

Nervous system - spinal cord (grade 8) - biology, preparation for the exam and exam

The human nervous system. Structure and function

Output

Absolutely any movement, every thought, look, sigh and heartbeat - all this is controlled by a network of nerves. It is responsible for human interaction with the outside world and connects all other organs into a single whole - the organism.

The nervous system is an integral morphological and functional set of various interconnected nervous structures, which, together with the humoral system, provides an interconnected regulation of the activity of all body systems and a response to changes in the conditions of the internal and external environment. The nervous system is made up of neurons, or nerve cells, and neuroglial cells (neuroglia). Neurons are the main structural and functional elements in both the central and peripheral nervous systems. Neurons- these are excitable cells, that is, they are able to generate and transmit electrical impulses (action potentials). Neurons have different shapes and sizes, they form processes of two types: axons and dendrites... A neuron usually has several short branched dendrites, along which impulses follow to the body of the neuron, and one long axon, along which impulses go from the body of the neuron to other cells (neurons, muscle or glandular cells). The transfer of excitation from one neuron to other cells occurs through specialized contacts - synapses. Neuroglial cells are more numerous than neurons and account for 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, demarcation and protective functions. By functional purpose, they distinguish 1) the somatic or animal nervous system, 2) the autonomous or autonomic nervous system.

In turn, in the autonomic nervous system, there are:

• The sympathetic division of the autonomic nervous system,
• Parasympathetic division of the autonomic nervous system,
• Metasympathetic division of the autonomic nervous system (enteric nervous system).

Central nervous system (CNS) - the main part of the nervous system of animals and humans, consisting of an accumulation of nerve cells (neurons) and their processes; It is represented in invertebrates by a system of closely interconnected nerve nodes (ganglia), in vertebrates and humans - by the spinal cord and brain.

The main and specific function of the central nervous system is the implementation of simple and complex highly differentiated reflective reactions, which are called. In higher animals and humans, the lower and middle parts of the central nervous system - the spinal cord, medulla oblongata, midbrain, diencephalon and cerebellum - regulate the activity of individual organs and systems of a highly developed organism, carry out communication and interaction between them, ensure the unity of the organism and the integrity of its activity. The higher part of the central nervous system - the cortex of the cerebral hemispheres and the nearest subcortical formations - mainly regulates the connection and relationship of the organism as a whole with the environment.

The central nervous system is connected to all organs and tissues through the peripheral nervous system, which in vertebrates includes cranial nerves extending from the brain, and spinal nerves from the spinal cord, intervertebral nerve nodes, as well as the peripheral part of the autonomic nervous system - nerve nodes, with suitable him (preganglionic) and the nerve fibers extending from them (postganglionic). Sensory, or afferent, nerve adductor fibers carry excitation in the central nervous system from peripheral receptors; along the efferent efferent (motor and autonomic) nerve fibers, excitation from the central nervous system is directed to the cells of the executive working apparatus (muscles, glands, blood vessels, etc.). In all parts of the central nervous system, there are afferent neurons that receive stimuli coming from the periphery, and efferent neurons that send nerve impulses to the periphery to various executive effector organs. Afferent and efferent cells with their processes can contact each other and make up a two-neuronal reflex arc that carries out elementary reflexes (for example, tendon reflexes of the spinal cord). But, as a rule, interneurons, or interneurons, are located in the reflex arc between afferent and efferent neurons. Communication between different parts of the central nervous system is also carried out with the help of a variety of processes of afferent, efferent and intercalary neurons of these parts, which form intracentral short and long pathways. The central nervous system also includes neuroglial cells, which perform a supporting function in it, and also participate in the metabolism of nerve cells.

The autonomic nervous system is a part of the nervous system that has a two-neuron structure and innervates the internal organs, smooth muscles, heart, endocrine glands and skin;

Through the autonomic nervous system, the central nervous system regulates the functions of internal organs, blood supply and trophism of all organs. In the autonomic nervous system, the sympathetic and parasympathetic divisions are distinguished.

The sympathetic nervous system is the peripheral part of the autonomic nervous system that mobilizes the body's available to perform urgent work. The sympathetic nervous system stimulates the heart, constricts blood vessels and enhances skeletal muscle performance. The sympathetic nervous system is represented by:

• gray matter of the lateral horns of the spinal cord;
• two symmetrical sympathetic trunks with their ganglia;
• inter-nodal and connecting branches; and
• branches and ganglia involved in the formation of nerve plexuses.

The parasympathetic nervous system is the peripheral part of the autonomic nervous system, responsible for maintaining the constancy of the internal environment of the body. The parasympathetic nervous system consists of:

• the cranial section, in which the preganglionic fibers leave the middle and rhomboid brain as part of several cranial nerves; and
• the sacral section, in which the preganglionic fibers leave the spinal cord as part of its ventral roots.

The parasympathetic nervous system inhibits the work of the heart, dilates some blood vessels.

The main directions of research of the nervous system

Modern science of the nervous system unites many scientific disciplines: along with classical neuroanatomy, neurology and neurophysiology, molecular biology and genetics, chemistry, cybernetics and a number of other sciences make important contributions to the study of the nervous system. This interdisciplinary approach to the study of the nervous system is reflected in the term neuroscience. In the Russian-language scientific literature, the term "neurobiology" is often used as a synonym. 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 is various mental processes: thinking, emotions, consciousness.<В соответствие с этой задачей изучение нервной системы ведется на разных уровнях организация, начиная с молекулярного и заканчивая изучением сознания, творческих способностей и социального поведения.