The structure and function of the central nervous system. The structure and function of the human nervous system. Features of the PNS structure

24.07.2020

Nerve endings are located throughout the human body. They have an essential 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 upon exposure and transmit impulse. The impulses reach the centers where they are analyzed. After analyzing the received signal, the brain transmits the necessary response to the stimulus to the corresponding 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 stimuli;
interaction of all organs.

The importance of the nervous system is to ensure the vital activity 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.

CNS structure

The anatomy of the central nervous system (CNS) is a collection of neuronal cells and neural processes in 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 the processing of impulses from the PNS.

The anatomy of the central nervous system, the main node of which is the brain, is a complex structure of branched fibers.

Higher nerve centers are concentrated in the cerebral hemispheres. This is the consciousness of a person, his personality, his intellectual abilities and speech. The main function of the cerebellum is to provide coordination of movements. The brain stem is inextricably linked with the hemispheres and cerebellum. This section contains the main nodes of the motor and sensory pathways, due to which such vital functions of the body as the regulation of blood circulation and the provision of respiration are provided. The spinal cord is the distribution structure of the central nervous system; it provides the branching of the fibers that form the PNS.

The spinal ganglion (ganglion) is a place where sensitive cells are concentrated. With the help of the spinal ganglion, the activity of the autonomic part of the peripheral nervous system is carried out. Ganglia or nerve nodes in the human nervous system are referred to as PNS, they function as analyzers. The ganglia are not part of the human central nervous system.

Features of the PNS structure

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

The structure and functions of the human peripheral nervous system are very complex, therefore, any slightest damage, for example, damage to blood vessels in the legs, can cause serious disruption of its work. Thanks to PNS, control over all parts of the body is carried out and the vital activity of all organs is ensured. The importance of this nervous system for the body cannot be overestimated.

PNS is divided into two divisions - the somatic and vegetative systems of the PNS.

The somatic nervous system does a double job - collecting information from the sense organs, and further transmitting this data to the central nervous system, as well as ensuring the body's motor activity 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, since it processes signals received from the organs of vision, hearing and taste buds.

The autonomic nervous system provides the functions of all organs. It controls the heartbeat, blood supply, respiratory activity. 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 - it is the vegetative part of the PNS that controls this. The principles of the structure and function of the PNS are studied in neurology.

PNS departments

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

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 some kind of influence.

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

One of the important parts of the vegetative part 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 provides motility to the small and large intestine. This department also regulates the secretion secreted in the gastrointestinal tract, and provides local blood supply.

The importance of the nervous system lies in ensuring the work of internal organs, intellectual function, motor skills, sensitivity and reflex activity. The central nervous system of a child 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 the development of the brain is formed already in the third week after conception. The main functional nodes are indicated 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 regions of the brain are already better developed than the spinal region.

By the time the baby is born, the brain is the most developed. The size of the brain in a newborn is about one-eighth of the weight of a child and fluctuates around 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 the 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 rebuild. 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.

CNS types

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

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

People can 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 inhibition process to the excitation process, and vice versa.

The types of the nervous system are divided into four types.

The weak type, or melancholic, is considered the most susceptible to the onset 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 distinguished by the predominance of excitation processes over inhibition processes.
Strong and agile is the type of sanguine person. All processes occurring in the cerebral cortex are strong and active. The strong, but inert, or phlegmatic type, is characterized by a low speed of switching of nervous processes.

The types of the nervous system are interrelated 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 the physiological characteristics of the processes occurring in the central nervous system.

CNS protection

The anatomy of the nervous system is very complex. The CNS and PNS are affected by stress, overexertion and lack of nutrition. For the normal functioning of the central nervous system, vitamins, amino acids and minerals are needed. Amino acids take part in the work of the brain and are the building blocks for neurons. Having figured out why and for what vitamins and amino acids are needed, 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 scheme of 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 bundles of nerve fibers, 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 - immobilization, paresis, muscle atrophy, encephalitis and much more.

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

There are many nerve endings in the human body, damage to which can cause a number of problems. Damage often results in impaired mobility of the body part. For example, an injury to the hand can lead to pain and impaired movement of the fingers. Osteochondrosis of the spine provoke the occurrence of pain in the foot due to the fact that an irritated or transmitted 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 with any accompanying problems, you must undergo an examination by a specialist.

SAINT PETERSBURG INSTITUTE

PSYCHOLOGY AND ACMEOLOGY

Department of Natural Sciences

Album of tables

by discipline

ANATOMY OF THE CNS

St. Petersburg

Album of tables for the discipline Anatomy of the central nervous system. Study guide / Comp .: Ginzburg I.A. - SPb .: SPbIPiA, 2009 .-- 26 p.

The manual is compiled in accordance with the state educational standard of higher professional education in the specialty 030301.65 "Psychology", approved on 17.03.2000, and the recommendations of the Ministry of Education of the Russian Federation.

The manual is intended for students of the Faculty of Psychology of all forms of education.

protocol no. 13 from " 29 » May 200 9 g.

© St. Petersburg Institute

psychology and acmeology, 2009

1. General neuroscience
1.1. General principles structure of the central nervous system ………………………… ...
1.2. Comparative table of the structure of the nervous system according to the topographic feature …………………………………….
1.3. Departments of the brain in ontogenesis …………………… ...
1.4. Comparative table of structural elements ………….
1.5. Microstructure of a neuron ………………………………… ....
1.6. Types of synapses ……………………………………………….
1.7. Comparative characteristics synapses ………………….
2. Private neuroscience
2.1. The membranes of the brain and spinal cord …………………….
2.2. The structure of the cerebral cortex ……………………………
2.3. Projection nerve centers …………………………….
2.4. Principles of the formation of cranial nerve fibers ……… ..
2.5. Cranial nerves ………………………………… .....
2.6. Distinctive features of the autonomic and somatic nervous system ………………………………………………….
2.7. Sympathetic and parasympathetic regulation of functions.

INTRODUCTION

The manual systematizes and summarizes data on the macro- and microscopic anatomy of the brain and spinal cord, outlines the structural features of the neuron, the system of afferent and efferent fibers, the functional purpose of individual anatomical structures of the central nervous system and the dynamic localization of functions in the cerebral cortex.

Materials are presented in the form of tables and graphical structures in order to complement and optimize the educational process for the course "Anatomy of the Central Nervous System".

The graphic material in a systematic form reflects the following sections of the course: general neurology (parts of the nervous system, the structure of nervous tissue and nerve cells, the structure of synaptic structures, ontogeny of the nervous system), private neuroscience (endbrain, autonomic nervous system, cranial nerves).

The album of tables and diagrams is intended for university students specializing in psychology. The manual does not replace existing textbooks and teaching aids, but is a systematic, additional material for the course Anatomy of the Central Nervous System.

1. GENERAL NEUROLOGY

1.1. GENERAL CONSTRUCTION PRINCIPLES

CENTRAL NERVOUS SYSTEM

central nervous system
Gray matter	White matter
The bodies of neurons, together with the nearest branches of their processes, are concentrated in the cerebral hemispheres, subcortical formations, in the brain stem, cerebellum and spinal cord.	Nerve fibers covered with myelin sheath and connecting individual centers with each other, i.e. pathways located in the brain and spinal cord.
In addition to nerve cells, the central nervous system has a neuroglia that surrounds nerve cells
Types of neurons
By function	By localization
1. Sensitive, perceiving or afferent (receptor) - carry out the function of perception and transmission to the central nervous system of information about the external world or the internal state of the body.	1. Afferent- lie outside the central nervous system in the nerve ganglia (nodes) of the peripheral nervous system. The process of the receiving neuron conducts excitation in the central nervous system (afferent fibers).
2. Motor, efferent neurons - transmit nerve impulses that regulate the state and activity of various organs.	2. Efferent neurons (their bodies) are located in the central nervous system or on the periphery - in the sympathetic and parasympathetic ganglia. The axons of efferent neurons are directed to the working organs (skeletal muscles, smooth muscles, glands).
3. Intermediate, associative or intercalary neurons communicate between different neurons, switch nerve impulses from afferent neurons to efferent ones.	3. Associative neurons are located within the central nervous system.

1.2. COMPARATIVE BUILDING TABLE

NERVOUS SYSTEM

BY TOPOGRAPHIC SIGN

Structure and function	central nervous system		Peripheral nervous system
Main components	Brain	Spinal cord	Cranial, spinal nerves, complexes of nerve nodes and nerve trunks.
Structure of departments	Gray matter - a cluster of neuronal bodies - cerebral cortex, cerebellar cortex, nuclei of subcortical nodes and brainstem	Gray matter - a cluster of neuronal bodies - medial location, white matter - nerve fibers (processes of nerve cells) Lateral location	Spinal section - spinal nodes, spinal nerve roots, spinal nerves, plexuses and branches, nerve endings Cranial division - cranial sensory nodes, cranial nerves, cranial branches and their endings.
Functional value	Receiving, analyzing information, making decisions. Storage and reproduction of information.		Connection of the brain and spinal cord with receptors and effectors. Providing innervation of the muscular apparatus of the trunk, limbs, partly internal organs.

1.3. DEPARTMENTS OF THE BRAIN IN ONTOGENESIS

Stage of three brain bladders	The Five Brain Bladder Stage	The cavity of the brain bladder	Departments of the brain	Pairs (nuclei) of cranial nerves
1. Rhomboid brain	1. Medulla oblongata	Fourth ventricle	Medulla
1. Rhomboid brain	2 hindbrain	Fourth ventricle	Cerebellum
2. Midbrain	3. Midbrain	Brain plumbing	Brain legs Roof plate, (quadruple)
3. Forebrain	4. Diencephalon	Third ventricle	Thalamic brain Epithalamus Metathalamus Hypothalamus
3. Forebrain	5. Ultimate brain	Lateral (paired) ventricles	Hemispheres of the brain Basal ganglia Olfactory brain	II - I pairs of cranial nerves have no nuclei

1.4. COMPARATIVE TABLE OF STRUCTURAL

NERVE TISSUE ELEMENTS

The human body works as a whole. The coordination and interaction of all organs is provided by the central nervous system. It is found in all living things and consists of nerve cells and their processes.

The central nervous system in vertebrates is represented by the brain and spinal cord, in invertebrates - by a system of combined nerve nodes. The central nervous system is protected by the bone structures of the skeleton: the cranium and the spine.

The structure of the central nervous system

The anatomy of the central nervous system studies the structure of the brain and spinal cord, which are associated with each organ through the peripheral NA.

The central nervous system is responsible for feelings such as:

hearing;
vision;
touch;
emotions;
memory;
thinking.

The structure of the brain of the central nervous system mainly contains white and gray substances.

Gray - these are nerve cells with small processes. Located in the spinal cord, it occupies the central part, encircling the spinal canal. As for the brain of the head, in this organ the gray matter makes up its cortex and has separate formations in the white matter. The white substance is located under the gray. Its structure contains nerve fibers that form nerve bundles. A number of these "bundles" make up a nerve.

The brain and spinal cord are surrounded by three membranes:

Solid. This is the outer shell. It is located in the inner cavity of the cranium and spinal canal.
Cobweb. This cover is under the hard part. In its structure, it has nerves and blood vessels.
Vascular. This shell is directly connected to the brain. She goes into his furrows. Formed from a variety of blood arteries. The arachnoid is separated from the choroid by a cavity that is filled with medulla.

The spinal cord as part of the central nervous system

This component of the central nervous system is located in the spinal canal. It stretches from the back of the head to the lumbar region. The brain has longitudinal grooves on both sides, and the spinal canal in the center. On the outside of the back brain is a white substance.

The gray element is predominantly composed of the lateral, posterior and anterior horny areas. The anterior horns contain motor nerve cells, while the posterior horns have intercalated, contacting sensory (lying in the nodal regions) and motor cells. The processes that make up the fibers are attached to the anterior horny portions of the motor particles. Those neurons that create the dorsal roots attach to the dorsal horny zones.

These roots are mediators between the brain and the back. Excitation arriving in the brain enters the intercalary neuron, and then through the axon enters the desired organ. Reaching the opening between the vertebrae, sensory cells connect with motor counterparts. After that, they are divided into posterior and anterior branches, which also consist of motor and sensory fibers. 62 mixed nerves depart from each vertebra in two directions.

Human head brain

This organ is located in the cerebral section of the cranium. Conventionally, it has five sections, inside it there are four cavities that are filled with cerebrospinal fluid. Most of the organ is hemispheres (80%). The second largest share is taken by the trunk.

It has the following structural areas:

middle;
cerebral;
oblong;
intermediate.

Areas of the brain

Medulla. This area continues the spinal cord and has a similar structure. Its structure is formed of white matter with areas of gray matter from which the nerves of the skull recede. The upper section ends with a varoli bridge, and the lower legs join the sides from the cerebellum. Almost all of this brain is covered by the hemispheres. The gray element of this part of the brain contains the centers responsible for the functioning of the lungs, heart function, swallowing, coughing, tears, salivation and the formation of gastric juice. Any damage to this area can stop breathing and heart activity, that is, lead to death.
Hindbrain. This part includes the cerebellum and the pons varoli. The Varoliev Bridge is a section that starts from the oblong and ends at the top with "legs". The lateral parts of it form the middle pedicles of the cerebellum. The pons of varoli includes: the facial, trigeminal, abducens and auditory nerves. The cerebellum is located behind the bridge and the medulla oblongata. This part of the organ consists of a gray component, which is the cortex, and a white substance with gray areas. The cerebellum consists of two hemispheres, a middle section and three pairs of legs. It is through these legs, which are composed of nerve fibers, that it is connected to other areas of the brain. Thanks to the cerebellum, a person can coordinate their movements, maintain balance, keep muscles in good shape, and perform clear and smooth movements. Through the pathways of the central nervous system, the cerebellum transmits impulses to muscle tissues. But its work is controlled by the cortex of the cerebral hemispheres.
Midbrain. Anatomically placed in front of the pons varoli. Consists of four hillocks and brain legs. In the center is the channel connecting the third and fourth ventricles. This duct surrounds the gray element. In the legs of the brain, there are pathways connecting the oblong and varoli bridge with the hemispheres. Thanks to the midbrain, it is possible to maintain tone and realize reflexes. It allows you to perform activities such as standing and walking. In addition, sensory nuclei are located in the hillocks of the quadruple, which have a connection with vision and hearing. They carry out light and sound reflexes.
Intermediate. It is located in front of the cerebral "legs". The divisions of this part of the central nervous system are a pair of visual hillocks, geniculate bodies, supra-hillock and sub-hillock regions. The structure of the diencephalon includes white matter and accumulations of gray matter. Here are the main centers of sensitivity - the visual hillocks. It is here that impulses from all over the body enter and then are sent to the cerebral cortex. The hypothalamus is located under the tubercles, where the vegetative system is shown by the subcortical higher center. Thanks to him, metabolism and heat transfer occur. This center maintains the stability of the internal environment. The auditory and optic nerves are located in the geniculate bodies.
Forebrain. Its structure is a large hemisphere with a connecting middle part. These hemispheres are separated by a "passage", below it is the corpus callosum. It connects both parts with nerve cell processes. The top of the hemispheres is the cerebral cortex, which consists of neurons and processes. Under it is a white substance that acts as a pathway. It unites the centers of the hemisphere into one whole. This substance consists of nerve cells that form the subcortical nuclei of the gray element. The cerebral cortex has a rather complex structure. It consists of over 14 billion nerve particles arranged in six balls. They have different shapes, sizes and connections.

The cerebral cortex of the head has convolutions and grooves.

Those, in turn, divide the surface into four sections:

occipital;
frontal;
parietal;
temple.

The central and temporal grooves are among the deepest. The first passes through the hemispheres, the second separates the temporal region of the brain from the others. In the area of \u200b\u200bthe frontal lobe, in front of the central sulcus, the central anterior gyrus is located. The posterior central gyrus is located behind the main sulcus.

The base of the brain is made up of the lower hemispheres and the trunk. Each part of the cerebral cortex has its own part of the body. This segment houses the centers of almost all sensitive systems. The analysis of the incoming information takes place in the cerebral cortex. The main areas of the cortex are olfactory, motor, sensory, auditory, visual.

The structure of the central nervous system in higher and lower living organisms is different. The system of lower animals has a reticular structure, higher organisms (including humans) have a neurogenic type of NS structure. In the first case, impulses can be transmitted diffusely; in the second, each cell functions as a separate unit, although it is connected with other neurons. The afferent nervous system transmits impulses from all organs to the central nervous system.

The connection points of these particles are called synapses. The area between the cell and its process is filled with glia. This is a collection of special particles that, unlike neurons, are able to divide. The most common type of such particles is astrocytes. They cleanse the extracellular space from excess ions and mediators, eliminate chemical problems that prevent coordinated reactions on the surface of nerve cells. In addition, astrocytes provide active cells with glucose and change the direction of oxygen transfer.

In the departments of the central nervous system, many nervous processes take place. Simple and complex highly differentiated reflective reactions are realized thanks to this system. The functions of the central nervous system can be characterized by two purposes: communication and interaction of a living organism and the external environment and regulation of the work of organs. This is one of the necessary conditions for the normal functioning of the body.

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

central nervous system (CNS), when viewed in detail, consists of the forebrain, midbrain, hindbrain and spinal cord. In these main parts of the central nervous system, in turn, the most important structures are distinguished that are directly related to mental processes, states and properties of a person: the thalamus, hypothalamus, pons, cerebellum and medulla oblongata.

Main and specific function CNS - implementation of simple and complex highly differentiated reflective reactions, called reflexes. 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. Higher department CNS - 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.
Almost all parts of the central and peripheral nervous system are involved in the processing of information coming through external and internal receptors located on the periphery of the body and in the organs themselves. The work of the cerebral cortex and subcortical structures included in the forebrain is associated with higher mental functions, with the thinking and consciousness of a person.

The central nervous system is connected to all organs and tissues of the body through the nerves that leave the brain and spinal cord. They carry information that comes to the brain from the external environment, and conduct it in the opposite direction to individual parts and organs of the body. Nerve fibers entering the brain from the periphery are called afferent, and those that conduct impulses from the center to the periphery are called efferent.
central nervous system is a collection of nerve cells - neurons. 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 tree-like processes extending from the bodies of nerve cells are called dendrites. One of these processes is elongated and connects the bodies of some neurons with the bodies or dendrites of other neurons. It is called an axon. Some of the axons are covered with a special myelin sheath, which facilitates faster conduction of impulses along the nerve.
The places where nerve cells contact each other are called synapses. Through them, nerve impulses are transmitted from one cell to another. The mechanism of synaptic impulse transmission, which works on the basis of biochemical metabolic processes, can facilitate or hinder the passage of nerve impulses through the central nervous system and thereby participate in the regulation of many mental processes and states of the body.

CNS connected with all organs and tissues through the peripheral nervous system, which in vertebrates includes the 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 to them (preganglionic) and extending from them (postganglionic) nerve fibers. 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 departments CNS 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. The connection 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, forming intracentral short and long pathways. Part CNS also includes neuroglia cells, which perform a supporting function in it, and also participate in the metabolism of nerve cells.

NERVOUS SYSTEM, a very complex network of structures that permeates the entire body and provides self-regulation of its life 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 mammals, the nervous system includes three main components: 1) nerve cells (neurons); 2) associated glial cells, in particular neuroglia cells, as well as cells that form neurilemma; 3) connective tissue. Neurons provide the conduction of nerve impulses; neuroglia perform 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 fiber sheaths 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). CNSincludes the brain and spinal cord, and the PNS, which provides the connection 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 tiny structures - organelles (see also

CNS - what is it? The structure of the human nervous system is described as an extensive electrical network. Perhaps this is the most accurate metaphor possible, since the current really runs through the thin filaments. Our cells generate micro-discharges themselves in order to quickly deliver information from receptors and sensory organs to the brain. But the system does not function by chance, everything is subject to a strict hierarchy. That is why they distinguish

Central nervous system departments

Let's consider this system in more detail. And yet, the central nervous system - what is it? Medicine gives a comprehensive answer to this question. It is the main part of the nervous system of chordates in animals and humans. It consists of structural units - neurons. In invertebrates, this whole structure is similar to an accumulation of nodules that do not have a clear subordination to each other.

The human central nervous system is represented by a ligament of the brain and spinal cord. In the latter, the cervical, thoracic, lumbar and sacrococcygeal regions are distinguished. They are located in the corresponding parts of the body. Almost all peripheral nerve impulses are conducted to the spinal cord.

The brain is also divided into several parts, each of which has a specific function, but the neocortex, or cerebral cortex, coordinates their work. So, anatomically distinguish:

brain stem;
medulla;
hindbrain (pons and cerebellum);
midbrain (plate of the quadruple and the legs of the brain);
forebrain

More details about each of these parts will be discussed below. Such a structure of the nervous system was formed in the process of human evolution so that he could ensure his existence in new conditions of life.

Spinal cord

It is one of the two organs of the central nervous system. The physiology of its work does not differ from that in the brain: with the help of complex chemical compounds (neurotransmitters) and the laws of physics (in particular, electricity), information from small branches of nerves is combined into large trunks and either is realized in the form of reflexes in the corresponding part of the spinal cord, or enters the brain for further processing.

It is located in the opening between the arches and the vertebral bodies. It is protected, like the head, by three membranes: hard, arachnoid and soft. The space between these tissue sheets is filled with fluid, which nourishes the nervous tissue and also acts as a shock absorber (dampens vibrations during movement). The spinal cord begins from the hole in the occipital bone, on the border with the medulla oblongata, and ends at the level of the first or second lumbar vertebra. Further there are only membranes, cerebrospinal fluid and long nerve fibers ("cauda equina"). Conventionally, anatomists divide it into sections and segments.

On the sides of each segment (corresponding to the height of the vertebra), there are sensory and motor nerve fibers called roots. These are long processes of neurons, the bodies of which are located directly in the spinal cord. They are a collector of information from other parts of the body.

Medulla

The medulla oblongata is also engaged in activity. It is part of an entity such as the brain stem and is in direct contact with the spinal cord. There is a conditional border between these anatomical formations - this is a cross. It is separated from the bridge by a transverse groove and a section of the auditory tract that pass in the rhomboid fossa.

In the thickness of the medulla oblongata are the nuclei of the 9th, 10th, 11th and 12th cranial nerves, fibers of the ascending and descending nerve pathways and the reticular formation. This site is responsible for performing protective reflexes such as sneezing, coughing, vomiting, and others. It also keeps us alive by regulating breathing and heart rate. In addition, the medulla oblongata contains centers for regulating muscle tone and maintaining posture.

Bridge

Together with the cerebellum, it is the back of the central nervous system. What is this? An accumulation of neurons and their processes, located between the transverse groove and the exit site of the fourth pair of cranial nerves. It is a roller-like thickening with a depression in the center (there are vessels in it). The fibers of the trigeminal nerve emerge from the middle of the bridge. In addition, the upper and middle pedicles of the cerebellum depart from the bridge, and in the upper part of the Varoliev bridge are the nuclei of the 8th, 7th, 6th and 5th pairs of cranial nerves, a section of the auditory tract and the reticular formation.

The main function of the bridge is to transfer information to the higher and lower parts of the central nervous system. Many ascending and descending paths pass through it, which end or begin their journey in different parts of the cerebral cortex.

Cerebellum

This is the department of the CNS (central nervous system), which is responsible for coordinating movements, maintaining balance and maintaining muscle tone. It is located between the bridge and the midbrain. For information on environment it has three pairs of legs in which nerve fibers pass.

The cerebellum acts as an intermediate collector of all information. It receives signals from sensory fibers of the spinal cord, as well as from motor fibers starting in the cortex. After analyzing the data obtained, the cerebellum sends impulses to the motor centers and corrects the position of the body in space. All this happens so quickly and smoothly that we do not notice his work. All our dynamic automatisms (dancing, playing musical instruments, writing) are the responsibility of the cerebellum.

Midbrain

There is a department in the human central nervous system that is responsible for visual perception. It is the midbrain. It consists of two parts:

The lower one represents the legs of the brain, in which the pyramidal pathways pass.
The upper one is the plate of the quadruple, on which, in fact, the visual and auditory centers are located.

The formations in the upper part are closely connected with the diencephalon, so there is not even an anatomical border between them. It can be tentatively assumed that this is the posterior commissure of the cerebral hemispheres. In the depths of the midbrain, the nuclei of the third cranial nerve - the oculomotor nerve - are located, and besides this, there is also a red nucleus (it is responsible for controlling movements), a substantia nigra (initiates movements) and the reticular formation.

The main functions of this area of \u200b\u200bthe central nervous system:

orienting reflexes (reaction to strong stimuli: light, sound, pain, etc.);
vision;
pupil response to light and accommodation;
friendly turn of the head and eyes;
maintaining skeletal muscle tone.

Diencephalon

This formation is located above the midbrain, just below the corpus callosum. It consists of the thalamic part, the hypothalamus and the third ventricle. The thalamic part includes the thalamus proper (or optic tubercle), epithalamus and metathalamus.

The thalamus is the center of all types of sensitivity, it collects all afferent impulses and redistributes it to the corresponding motor pathways.
The epithalamus (pineal gland, or pineal gland) is an endocrine gland. Its main function is to regulate human biorhythms.
The metathalamus is formed by the medial and lateral geniculate bodies. The medial bodies represent the subcortical center of hearing, and the lateral bodies represent the vision.

The hypothalamus is in charge of the pituitary gland and other endocrine glands. In addition, it partially regulates the autonomic nervous system. We must thank him for the metabolic rate and maintenance of body temperature. The third ventricle is a narrow cavity that contains the fluid needed to feed the central nervous system.

Bark of hemispheres

CNS neocortex - what is it? This is the youngest part of the nervous system, phylo - and ontogenetically, it is formed by one of the last and is a series of cells, densely layered on top of each other. This area takes up about half of the entire space of the cerebral hemispheres. It contains convolutions and grooves.

There are five parts of the cortex: frontal, parietal, temporal, occipital and insular. Each of them is responsible for its own area of \u200b\u200bwork. For example, the frontal lobe contains centers of movement and emotion. In the parietal and temporal - the centers of writing, speech, small and complex movements, in the occipital - visual and auditory, and the insular lobe corresponds to balance and coordination.

All information that is perceived by the endings of the peripheral nervous system, be it smell, taste, temperature, pressure, or anything else, enters the cerebral cortex and is carefully processed. This process is so automated that when, due to pathological changes, it stops or gets upset, a person becomes disabled.

CNS functions

For such a complex formation as the central nervous system, the corresponding functions are also characteristic. The first of them is integrative coordination. It implies the well-coordinated work of various organs and systems of the body to maintain the constancy of the internal environment. The next function is the connection between a person and his environment, adequate reactions of the body to physical, chemical or biological stimuli. It also includes social activities.

The functions of the central nervous system also cover metabolic processes, their speed, quality and quantity. There are separate structures for this, such as the hypothalamus and pituitary gland. Higher mental activity is also possible only thanks to the central nervous system. When the cortex dies off, the so-called "social death" is observed, when the human body still remains viable, but as a member of society it no longer exists (cannot speak, read, write and perceive other information, as well as reproduce it).

It is difficult to imagine humans and other animals without a central nervous system. Its physiology is complex and has not yet been fully studied. Scientists are trying to understand how the most complex biological computer ever existed. But this is similar to the way "a bunch of atoms study other atoms", so progress in this area has not yet been sufficient.