Nervous System (NS): functions, structure and diseases. Lek nervous system

LECTURE ON THE TOPIC: HUMAN NERVOUS SYSTEM

Nervous system is a system that regulates the activity of all human organs and systems. This system determines: 1) the functional unity of all human organs and systems; 2) the connection of the whole organism with environment.

From the point of view of maintaining homeostasis, the nervous system provides: maintaining the parameters of the internal environment at a given level; inclusion of behavioral responses; adaptation to new conditions if they persist for a long time.

Neuron(nerve cell) - the main structural and functional element nervous system; Humans have over 100 billion neurons. The neuron consists of a body and processes, usually one long process - an axon and several short branched processes - dendrites. Along the dendrites, impulses follow to the cell body, along the axon - from the cell body to other neurons, muscles or glands. Thanks to the processes, neurons contact each other and form neural networks and circles through which nerve impulses circulate.

A neuron is the functional unit of the nervous system. Neurons are susceptible to stimulation, that is, they are able to be excited and transmit electrical impulses from receptors to effectors. In the direction of impulse transmission, afferent neurons (sensory neurons), efferent neurons (motor neurons) and intercalary neurons are distinguished.

Nervous tissue is called excitable tissue. In response to some influence, the process of excitation arises and spreads in it - the rapid recharging of cell membranes. The emergence and spread of excitation (nerve impulse) is the main way the nervous system implements its control function.

The main prerequisites for the occurrence of excitation in cells: the existence of an electrical signal on the membrane at rest - the resting membrane potential (RMP);

the ability to change the potential by changing the permeability of the membrane for certain ions.

The cell membrane is a semi-permeable biological membrane, it has channels for potassium ions to pass through, but there are no channels for intracellular anions that are held at the inner surface of the membrane, while creating a negative charge of the membrane from the inside, this is the resting membrane potential, which is on average - - 70 millivolts (mV). There are 20-50 times more potassium ions in the cell than outside, this is maintained throughout life with the help of membrane pumps (large protein molecules capable of transporting potassium ions from the extracellular environment to the inside). The MPP value is due to the transfer of potassium ions in two directions:

1. outside into the cage under the action of pumps (with a large expenditure of energy);

2. out of the cell by diffusion through membrane channels (without energy costs).

In the process of excitation, the main role is played by sodium ions, which are always 8-10 times more outside the cell than inside. Sodium channels are closed when the cell is at rest, in order to open them, it is necessary to act on the cell with an adequate stimulus. If the stimulation threshold is reached, sodium channels open and sodium enters the cell. In thousandths of a second, the membrane charge will first disappear, and then change to the opposite - this is the first phase of the action potential (AP) - depolarization. The channels close - the peak of the curve, then the charge is restored on both sides of the membrane (due to potassium channels) - the stage of repolarization. Excitation stops and while the cell is at rest, the pumps change the sodium that has entered the cell for the potassium that has left the cell.

AP evoked at any point of the nerve fiber itself becomes an irritant for neighboring sections of the membrane, causing AP in them, and they, in turn, excite more and more new sections of the membrane, thus spreading throughout the cell. In myelin-coated fibers, PD will only occur in myelin-free areas. Therefore, the speed of signal propagation increases.

The transfer of excitation from a cell to another occurs with the help of a chemical synapse, which is represented by the point of contact between two cells. The synapse is formed by the presynaptic and postsynaptic membranes and the synaptic cleft between them. Excitation in the cell resulting from AP reaches the area of the presynaptic membrane, where synaptic vesicles are located, from which a special substance, the mediator, is ejected. The neurotransmitter enters the gap, moves to the postsynaptic membrane and binds to it. Pores for ions open in the membrane, they move inside the cell and a process of excitation occurs.

Thus, in the cell, the electrical signal is converted into a chemical one, and the chemical signal is again converted into an electrical one. Signal transmission in the synapse is slower than in the nerve cell, and also one-sided, since the mediator is released only through the presynaptic membrane, and can only bind to the receptors of the postsynaptic membrane, and not vice versa.

Mediators can cause in cells not only excitation, but also inhibition. At the same time, pores are opened on the membrane for such ions, which increase the negative charge that existed on the membrane at rest. One cell can have many synaptic contacts. An example of a mediator between a neuron and a skeletal muscle fiber is acetylcholine.

The nervous system is divided into central nervous system and peripheral nervous system.

In the central nervous system, the brain is distinguished, where the main nerve centers and the spinal cord are concentrated, here there are centers of a lower level and there are pathways to peripheral organs.

Peripheral - nerves, ganglia, ganglia and plexuses.

The main mechanism of activity of the nervous system - reflex. A reflex is any response of the body to a change in the external or internal environment, which is carried out with the participation of the central nervous system in response to irritation of the receptors. The structural basis of the reflex is the reflex arc. It includes five consecutive links:

1 - Receptor - a signaling device that perceives the impact;

2 - Afferent neuron - leads the signal from the receptor to the nerve center;

3 - Intercalary neuron - the central part of the arc;

4 - Efferent neuron - the signal comes from the central nervous system to the executive structure;

5 - Effector - a muscle or gland that performs a certain type of activity

Brain consists of clusters of bodies nerve cells, nerve tracts and blood vessels. Nerve tracts form the white matter of the brain and consist of bundles of nerve fibers that conduct impulses to or from different parts of the gray matter of the brain - the nuclei or centers. Pathways connect the various nuclei, as well as the brain with the spinal cord.

Functionally, the brain can be divided into several sections: the forebrain (consisting of the telencephalon and diencephalon), the midbrain, the hindbrain (consisting of the cerebellum and the pons), and the medulla oblongata. The medulla oblongata, pons, and midbrain are collectively referred to as the brainstem.

Spinal cord located in the spinal canal, reliably protecting it from mechanical damage.

The spinal cord has a segmental structure. Two pairs of anterior and posterior roots depart from each segment, which corresponds to one vertebra. There are 31 pairs of nerves in total.

The posterior roots are formed by sensitive (afferent) neurons, their bodies are located in the ganglia, and the axons enter the spinal cord.

The anterior roots are formed by axons of efferent (motor) neurons whose bodies lie in the spinal cord.

The spinal cord is conditionally divided into four sections - cervical, thoracic, lumbar and sacral. It closes a huge number of reflex arcs, which ensures the regulation of many body functions.

The gray central substance is nerve cells, the white one is nerve fibers.

The nervous system is divided into somatic and autonomic.

To somatic nervous system (from the Latin word "soma" - body) refers to the part of the nervous system (both cell bodies and their processes), which controls the activity of skeletal muscles (body) and sensory organs. This part of the nervous system is largely controlled by our consciousness. That is, we are able to bend or unbend an arm, a leg, and so on at will. However, we are unable to consciously stop perceiving, for example, sound signals.

Autonomic nervous a system (translated from Latin “vegetative” - vegetable) is a part of the nervous system (both the cell body and their processes) that controls the processes of metabolism, growth and reproduction of cells, that is, functions that are common to both animals and plants organisms. The autonomic nervous system controls, for example, the activity of internal organs and blood vessels.

The autonomic nervous system is practically not controlled by consciousness, that is, we are not able to relieve gallbladder spasm at will, stop cell division, stop intestinal activity, expand or narrow blood vessels

Together with the endocrine system, it regulates the functions of the body, controls all the processes occurring in it. It consists of the central sections, which include the brain and spinal cord, and the peripheral part - nerve fibers and nodes.

The Russian scientist I. Pavlov classified variants of the nervous system in humans depending on functional characteristics: the strength and displacement of the processes of excitation and inhibition, as well as their ability to be in balance. These properties are expressed in a particular person making decisions, expressiveness of emotions.

What are the types of the human nervous system

There are four of them and they correlate in an interesting way with the types of human temperament identified by Hippocrates. Pavlov argued that the types of the nervous system largely depend only on innate qualities and change little under the influence of the environment. Now scientists think differently and say that in addition to hereditary factors big role also plays and education.

Consider the types of the nervous system in more detail. First of all, they can be divided into two large categories - strong and weak. In this case, the first group has a division into mobile and inert, or immobile.

Strong types of the nervous system:

Mobile unbalanced. It is characterized by a high strength of nervous processes, excitation in the nervous system of such a person dominates over inhibition. Personal qualities his following: he has an abundance of vital energy, but he is quick-tempered, difficult to restrain, highly emotional.

Movable balanced. The strength of processes is high without the predominance of one over the other. The owner of such characteristics of the nervous system is active, lively, adapts well and successfully resists life problems without much damage to the psyche.

As we can see, the mobile types of the nervous system are those whose functional qualities are the possibility of a rapid transition from excitation to inhibition and vice versa. Their owners can quickly adapt to changing environmental conditions.

Inert balanced. Nervous processes are strong and in balance, but the change from excitation to inhibition and vice versa is slowed down. A person with this type is unemotional, unable to quickly respond to changing conditions. However, it is resistant to long exhausting influences of unfavorable factors.

The last type of the nervous system - melancholic - is referred to as characterized by the predominance of inhibition, a person has pronounced passivity, low performance and emotionality.

The psyche is not resistant to negative influences.

The great ancient physician singled out four variants of temperament: they are nothing more than an external manifestation of the type of functioning of the nervous system. They are presented in the order corresponding to the types discussed above:

choleric (first),
sanguine (second),
phlegmatic (third),
melancholic (fourth).

The nervous system, together with the endocrine system, controls all processes in the body, both simple and complex. It consists of the brain, spinal and peripheral nerve fibers.

NS classification

The nervous system is divided into: central and peripheral.

The central nervous system is the main part, it includes the spinal cord and brain. Both of these organs are reliably protected by the skull and spine. The PNS is the nerves responsible for movement and sensory. It ensures the interaction of man with the environment. With the help of the PNS, the body receives signals and responds to them.

PNS is of two types:

Somatic - sensory and motor nerve fibers. Responsible for the coordination of movement, a person can consciously control his body.
Vegetative - is divided into sympathetic and parasympathetic. The first gives a response to danger and stress. The second - is responsible for peace, normalization of the organs (digestive, urinary).

Despite their differences, both systems are interconnected and cannot work autonomously.

Properties of nervous processes

The classification of GNI types is influenced by the properties of nervous processes, these include:

balance - the same flow of processes in the central nervous system, such as excitation and inhibition;
mobility - a quick change from one process to another;
strength - the ability to respond correctly to a stimulus of any strength.

What are signal systems

The signaling system is a set of reflexes that connect the body with the environment. They serve as a step in the formation of higher nervous activity.

There are two signal systems:

reflexes to specific stimuli - light, sound (animals and humans have);
speech system - developed in humans in the process of labor activity.

Evolution of the CNS

The evolution of the functions of CNS cells occurred in several stages:

improvement of individual cells;
formation of new properties capable of interacting with the environment.

The main stages of phylogenesis that the nervous system has gone through are:

The diffuse type is one of the oldest; it is found in organisms such as intestinal cavities (jellyfish). It is a type of network that consists of clusters of neurons (bipolar and multipolar). Despite the simplicity, the nerve plexuses, reacting to irritations, give a reaction throughout the body. The speed at which excitation propagates through the fibers is low.
In the process of evolution, a stem type stood out - a number of cells gathered into trunks, but diffuse plexuses also remained. It is represented in a group of protostomes (flatworms).
Further development led to the emergence of a nodal type - part of the CNS cells are assembled into nodes with the possibility of transmitting excitation from one node to another. The improvement of cells and the development of reception apparatuses occurred in parallel. Nerve impulses originating in any part of the body do not spread throughout the body, but only within the segment. Representatives of this type are invertebrates: mollusks, arthropods, insects.
Tubular - the highest, characteristic of chordates. Polysynaptic connections appear, which leads to a qualitatively new relationship between the organism and the environment. This type includes vertebrates: animals, different in appearance and having a different way of life, and a person. They have a nervous system in the form of a tube that ends in the brain.

Varieties

The scientist Pavlov spent many years conducting laboratory research, studying the reflexes of dogs. He concluded that in humans, the type of nervous system mainly depends on congenital characteristics. It is the nervous system, its properties, physiologically affect the formation of temperament.

However, modern scientists argue that this is influenced not only by hereditary factors, but also by the level of education, training and social environment.

Thanks to all the research, highlighted the following types nervous system, depending on the course of the processes of excitation, inhibition and being in balance:

Strong, unbalanced - choleric. In this type, excitation of the nervous system predominates over inhibition. Choleric people are very energetic, but they are emotional, quick-tempered, aggressive, ambitious and lack self-control.
Strong, balanced, mobile - sanguine. People of this type are characterized as lively, active, easily adapt to different living conditions, have a high resistance to life's difficulties. They are leaders, and confidently go to their goal.
Strong, balanced, inert - phlegmatic. He is the opposite of sanguine. His reaction to everything that happens is calm, he is not prone to violent emotions, I am sure he has great resistance to problems.
Weak - melancholic. The melancholic is not able to withstand any stimuli, regardless of whether they are positive or negative. Characteristic features: lethargy, passivity, cowardice, tearfulness. With a strong stimulus, a violation of behavior is possible. A melancholic is always in a bad mood.

Interesting: psychopathic disorders more common in people with severe unbalanced and weak type GNI.

How to determine a person's temperament

It is not easy to determine what type of nervous system a person has, since this is influenced by the cerebral cortex, subcortical formations, and the level of development signaling systems and intellect.

In animals, the type of NS is more influenced by the biological environment. For example, puppies taken from the same litter, but raised in different conditions may have different temperaments.

Investigating the central nervous system and human psychology, Pavlov developed a questionnaire (test), after passing which, one can determine one's belonging to one of the types of GNA, subject to the veracity of the answers.

The nervous system controls the activity of all organs. Its type affects the character and behavior of a person. People who have general type are similar in their reactions to certain life situations.

Include organs of the central nervous system (brain and spinal cord) and organs of the peripheral nervous system (peripheral ganglions, peripheral nerves, receptor and effector nerve endings).

Functionally, the nervous system is divided into somatic, which innervates skeletal muscle tissue, i.e., controlled by consciousness, and vegetative (autonomous), which regulates activity internal organs, vessels and glands, i.e. does not depend on consciousness.

The functions of the nervous system are regulatory and integrating.

It is laid on the 3rd week of embryogenesis in the form of a neural plate, which is transformed into a neural groove, from which a neural tube is formed. There are 3 layers in its wall:

Internal - ependymal:

Medium - raincoat. Later it turns into gray matter.

External - edge. It produces white matter.

In the cranial part of the neural tube, an extension is formed, from which 3 cerebral vesicles are formed at the beginning, and later - five. The latter give rise to five parts of the brain.

The spinal cord is formed from the trunk of the neural tube.

In the first half of embryogenesis, there is an intensive proliferation of young glial and nerve cells. Subsequently, a radial glia is formed in the mantle layer of the cranial region. Its thin long processes penetrate the wall of the neural tube. Young neurons migrate along these processes. There is a formation of centers of the brain (especially intensively from 15 to 20 weeks - a critical period). Gradually, in the second half of embryogenesis, proliferation and migration fade. After birth, division stops. When the neural tube is formed, the cells that are located between the ectoderm and the neural tube are evicted from the neural folds (interlocking areas), forming the neural crest. The latter is split into 2 sheets:

1 - under the ectoderm, pigmentocytes (skin cells) are formed from it;

2 - around the neural tube - ganglionic plate. Peripheral nerve nodes (ganglia), the adrenal medulla, and sections of chromaffin tissue (along the spine) are formed from it. After birth, there is an intensive growth of the processes of nerve cells: axons and dendrites, synapses between neurons, neural circuits (a strictly ordered interneuronal connection) are formed, which make up reflex arcs (sequentially located cells that transmit information) that provide reflex activity of a person (especially the first 5 years of life). child, so stimuli are needed to form bonds). Also in the first years of a child's life, myelination is the most intensive - the formation of nerve fibers.

PERIPHERAL NERVOUS SYSTEM (PNS).

Peripheral nerve trunks are part of the neurovascular bundle. They are mixed in function, contain sensory and motor nerve fibers (afferent and efferent). Myelinated nerve fibers predominate, and non-myelinated ones are in small quantities. Around each nerve fiber is a thin layer of loose connective tissue with blood and lymphatic vessels - endoneurium. Around the bundle of nerve fibers is a sheath of loose fibrous connective tissue - the perineurium - with a small number of vessels (it mainly performs a frame function). Around the entire peripheral nerve there is a sheath of loose connective tissue with larger vessels - the epineurium. Peripheral nerves regenerate well, even after complete damage. Regeneration is carried out due to the growth of peripheral nerve fibers. The growth rate is 1-2 mm per day (the ability to regenerate is a genetically fixed process).

spinal node

It is a continuation (part) of the posterior root of the spinal cord. Functionally sensitive. Outside covered with a connective tissue capsule. Inside - connective tissue layers with blood and lymphatic vessels, nerve fibers (vegetative). In the center - myelinated nerve fibers of pseudo-unipolar neurons located along the periphery of the spinal ganglion. Pseudo-unipolar neurons have a large rounded body, a large nucleus, well-developed organelles, especially the protein-synthesizing apparatus. A long cytoplasmic outgrowth departs from the body of the neuron - this is part of the body of the neuron, from which one dendrite and one axon depart. Dendrite - long, forms a nerve fiber that goes as part of a peripheral mixed nerve to the periphery. Sensitive nerve fibers end at the periphery with a receptor, i.e. sensitive nerve ending. Axons are short and form the posterior root of the spinal cord. In the posterior horns of the spinal cord, axons form synapses with interneurons. Sensitive (pseudo-unipolar) neurons constitute the first (afferent) link of the somatic reflex arc. All cell bodies are located in ganglia.

Spinal cord

Outside, it is covered with a pia mater, which contains blood vessels that penetrate into the substance of the brain. Conventionally, 2 halves are distinguished, which are separated by the anterior median fissure and the posterior median connective tissue septum. In the center is the central canal of the spinal cord, which is located in the gray matter, lined with ependyma, contains cerebrospinal fluid, which is in constant motion. Along the periphery is white matter, where there are bundles of nerve myelin fibers that form pathways. They are separated by glial-connective tissue septa. In the white matter, the anterior, lateral and posterior cords are distinguished.

In the middle part there is a gray matter, in which the posterior, lateral (in the thoracic and lumbar segments) and anterior horns are distinguished. The halves of the gray matter are connected by the anterior and posterior commissures of the gray matter. In gray matter, there are in large numbers glial and nerve cells. Gray matter neurons are divided into:

1) Internal neurons, completely (with processes) located within the gray matter, are intercalated and are located mainly in the posterior and lateral horns. There are:

a) Associative. located within one half.

b) Commissural. Their processes extend into the other half of the gray matter.

2) Beam neurons. They are located in the posterior horns and in the lateral horns. They form nuclei or are located diffusely. Their axons enter the white matter and form bundles of nerve fibers in an ascending direction. They are inserts.

3) Radicular neurons. They are located in the lateral nuclei (kernels of the lateral horns), in the anterior horns. Their axons extend beyond the spinal cord and form the anterior roots of the spinal cord.

In the superficial part of the posterior horns is a spongy layer, which contains big number small intercalary neurons.

Deeper than this strip is a gelatinous substance containing mainly glial cells, small neurons (the latter in small quantities).

In the middle part is the own nucleus of the posterior horns. It contains large beam neurons. Their axons go to the white matter of the opposite half and form the dorsal-cerebellar anterior and dorsal-thalamic posterior pathways.

The cells of the nucleus provide exteroceptive sensitivity.

At the base of the posterior horns is the thoracic nucleus (Clark-Shutting column), which contains large bundle neurons. Their axons go to the white matter of the same half and participate in the formation of the posterior spinal cerebellar tract. Cells in this pathway provide proprioceptive sensitivity.

In the intermediate zone are the lateral and medial nuclei. The medial intermediate nucleus contains large bundle neurons. Their axons go to the white matter of the same half and form the anterior spinal cerebellar tract, which provides visceral sensitivity.

The lateral intermediate nucleus refers to the autonomic nervous system. In the thoracic and upper lumbar regions it is the sympathetic nucleus, and in the sacral region it is the nucleus of the parasympathetic nervous system. It contains an intercalary neuron, which is the first neuron of the efferent link of the reflex arc. This is a radicular neuron. Its axons exit as part of the anterior roots of the spinal cord.

In the anterior horns are large motor nuclei, which contain motor radicular neurons with short dendrites and a long axon. The axon exits as part of the anterior roots of the spinal cord, and then goes as part of the peripheral mixed nerve, represents motor nerve fibers and is pumped at the periphery by a neuromuscular synapse on skeletal muscle fibers. They are effectors. Forms the third effector link of the somatic reflex arc.

In the anterior horns, a medial group of nuclei is isolated. It is developed in the thoracic region and provides innervation to the muscles of the body. The lateral group of nuclei is located in the cervical and lumbar regions and innervates the upper and lower extremities.

In the gray matter of the spinal cord there is a large number of diffuse bundle neurons (in the posterior horns). Their axons go into the white matter and immediately divide into two branches that go up and down. Branches through 2-3 segments of the spinal cord return back to the gray matter and form synapses on the motor neurons of the anterior horns. These cells form their own apparatus of the spinal cord, which provides a connection between neighboring 4-5 segments of the spinal cord, which ensures the response of a muscle group (an evolutionarily developed protective reaction).

The white matter contains ascending (sensitive) pathways, which are located in the posterior cords and in the peripheral part of the lateral horns. Descending nerve pathways (motor) are located in the anterior cords and in the inner part of the lateral cords.

Regeneration. Very poorly regenerates gray matter. Regeneration of white matter is possible, but the process is very long.

Histophysiology of the cerebellum. The cerebellum refers to the structures of the brain stem, i.e. is a more ancient formation that is part of the brain.

Performs a number of functions:

balance;

The centers of the autonomic nervous system (ANS) (intestinal motility, blood pressure control) are concentrated here.

Outside covered with meninges. The surface is embossed due to deep furrows and convolutions, which are deeper than in the cerebral cortex (CBC).

On the cut is represented by the so-called "tree of life".

The gray matter is located mainly along the periphery and inside, forming nuclei.

In each gyrus, the central part is occupied by white matter, in which 3 layers are clearly visible:

1 - surface - molecular.

2 - medium - ganglionic.

3 - internal - granular.

1. The molecular layer is represented by small cells, among which basket and stellate (small and large) cells are distinguished.

Basket cells are located closer to the ganglion cells of the middle layer, i.e. inside the layer. They have small bodies, their dendrites branch in the molecular layer, in a plane transverse to the course of the gyrus. The neurites run parallel to the plane of the gyrus above the bodies of the pear-shaped cells (the ganglion layer), forming numerous branches and contacts with the dendrites of the pear-shaped cells. Their branches are braided around the bodies of pear-shaped cells in the form of baskets. Excitation of basket cells leads to inhibition of pear-shaped cells.

Outwardly, stellate cells are located, the dendrites of which branch out here, and the neurites participate in the formation of the basket and communicate by synapses with the dendrites and bodies of the pear-shaped cells.

Thus, the basket and stellate cells of this layer are associative (connecting) and inhibitory.

2. Ganglion layer. Here are located large ganglion cells (diameter = 30-60 microns) - Purkin' cells. These cells are located strictly in one row. The cell bodies are pear-shaped, there is a large nucleus, the cytoplasm contains EPS, mitochondria, the Golgi complex is poorly expressed. One neurite departs from the base of the cell, which passes through the granular layer, then into the white matter and ends at the cerebellar nuclei with synapses. This neurite is the first link in the efferent (descending) pathways. 2-3 dendrites depart from the apical part of the cell, which branch intensively in the molecular layer, while the branching of the dendrites occurs in a plane transverse to the course of the gyrus.

Pear-shaped cells are the main effector cells of the cerebellum, where an inhibitory impulse is produced.

3. Granular layer, saturated with cellular elements, among which cells - grains stand out. These are small cells, with a diameter of 10-12 microns. They have one neurite, which goes into the molecular layer, where it comes into contact with the cells of this layer. Dendrites (2-3) are short and branch into numerous "bird's foot" branches. These dendrites come into contact with afferent fibers called bryophytes. The latter also branch out and come into contact with the branching of the dendrites of cells - grains, forming glomeruli of thin weaves like moss. In this case, one mossy fiber is in contact with many cells - grains. And vice versa - the cell - the grain is also in contact with many mossy fibers.

Mossy fibers come here from the olives and the bridge, i.e. they bring here the information that comes through the associative neurons to the pear-shaped neurons. Large stellate cells are also found here, which lie closer to the pear-shaped cells. Their processes contact the granule cells proximal to the mossy glomeruli and in this case block the impulse transmission.

Other cells can also be found in this layer: stellate with a long neurite extending into the white matter and further into the adjacent gyrus (Golgi cells are large stellate cells).

Afferent climbing fibers - liana-like - enter the cerebellum. They come here as part of the spinal tracts. Then they crawl along the bodies of pear-shaped cells and along their processes, with which they form numerous synapses in the molecular layer. Here they carry an impulse directly to the pear-shaped cells.

Efferent fibers come out of the cerebellum, which are the axons of the piriform cells.

The cerebellum has a large number of glial elements: astrocytes, oligodendrogliocytes, which perform supporting, trophic, restrictive and other functions. A large amount of serotonin is released in the cerebellum, thus. the endocrine function of the cerebellum can also be distinguished.

Cerebral cortex (CBC)

This is a newer part of the brain. (It is believed that the CBP is not a vital organ.) It has great plasticity.

Thickness can be 3-5mm. The area occupied by the cortex increases due to furrows and convolutions. CBP differentiation ends by the age of 18, and then there are processes of accumulation and use of information. The mental abilities of an individual also depend on the genetic program, but in the end it all depends on the number of synaptic connections formed.

There are 6 layers in the cortex:

1. Molecular.

2. External granular.

3. Pyramidal.

4. Internal grainy.

5. Ganglionic.

6. Polymorphic.

Deeper than the sixth layer is the white matter. The bark is divided into granular and agranular (according to the severity of granular layers).

In KBP cells have different shape and different sizes, in diameter from 10-15 to 140 microns. The main cellular elements are pyramidal cells, which have a pointed apex. Dendrites extend from the lateral surface, and one neurite from the base. Pyramidal cells can be small, medium, large, giant.

In addition to pyramidal cells, there are arachnids, cells - grains, horizontal.

The arrangement of cells in the cortex is called cytoarchitectonics. The fibers that form myelin pathways or various systems of associative, commissural, etc. form the myeloarchitectonics of the cortex.

1. In the molecular layer, cells are found in small numbers. The processes of these cells: the dendrites go here, and the neurites form an external tangential path, which also includes the processes of the underlying cells.

2. Outer granular layer. There are many small cellular elements of pyramidal, stellate and other forms. The dendrites either branch here or pass into another layer; neurites go to the tangential layer.

3. Pyramid layer. Quite extensive. Basically, small and medium pyramidal cells are found here, the processes of which also branch out in the molecular layer, and the neurites of large cells can go into the white matter.

4. Inner granular layer. It is well expressed in the sensitive zone of the cortex (granular type of cortex). Represented by many small neurons. The cells of all four layers are associative and transmit information to other departments from the underlying departments.

5. Ganglion layer. Here are located mainly large and giant pyramidal cells. These are mainly effector cells, tk. the neurites of these neurons go into the white matter, being the first links of the effector pathway. They can give off collaterals, which can return to the cortex, forming associative nerve fibers. Some processes - commissural - go through the commissure to the neighboring hemisphere. Some neurites switch either on the nuclei of the cortex, or in the medulla oblongata, in the cerebellum, or they can reach the spinal cord (Ir. congestion-motor nuclei). These fibers form the so-called. projection paths.

6. The layer of polymorphic cells is located on the border with the white matter. There are large neurons of various shapes. Their neurites can return in the form of collaterals to the same layer, or to another gyrus, or to myelin pathways.

The entire cortex is divided into morpho-functional structural units - columns. 3-4 million columns are distinguished, each of which contains about 100 neurons. The column passes through all 6 layers. The cellular elements of each column are concentrated around the top column, which includes a group of neurons capable of processing a unit of information. This includes afferent fibers from the thalamus, and cortico-cortical fibers from the adjacent column or from the adjacent gyrus. This is where the efferent fibers come out. Due to collaterals in each hemisphere, 3 columns are interconnected. Through commissural fibers, each column is connected to two columns of the adjacent hemisphere.

All organs of the nervous system are covered with membranes:

1. The pia mater is formed by loose connective tissue, due to which furrows are formed, carries blood vessels and is delimited by glial membranes.

2. The arachnoid meninges are represented by delicate fibrous structures.

Between the soft and arachnoid membranes there is a subarachnoid space filled with cerebral fluid.

3. Dura mater, formed from coarse fibrous connective tissue. It is fused with bone tissue in the region of the skull, and is more mobile in the region of the spinal cord, where there is a space filled with cerebrospinal fluid.

The gray matter is located on the periphery, and also forms nuclei in the white matter.

Autonomic nervous system (ANS)

Subdivided into:

sympathetic part,

parasympathetic part.

The central nuclei are distinguished: the nuclei of the lateral horns of the spinal cord, the medulla oblongata, and the midbrain.

On the periphery, nodes can form in organs (paravertebral, prevertebral, paraorganic, intramural).

The reflex arc is represented by the afferent part, which is common, and the efferent part is the preganglionic and postganglionic link (they can be multi-storied).

In the peripheral ganglia of the ANS, various cells can be located in structure and function:

Motor (according to Dogel - type I):

Associative (type II)

Sensitive, the processes of which reach the neighboring ganglia and extend far beyond.

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

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

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

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

The value 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.

Structure of the CNS

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

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

Structural features of the PNS

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

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

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

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

Ensures the performance of the functions of all organs. It controls the heartbeat, blood supply, and 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.

Departments of the PNS

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

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

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

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

The value of the nervous system is to ensure the work of internal organs, intellectual function, motor skills, sensitivity and reflex activity. The child's CNS develops not only during intrauterine period but also during the first year of life. The 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 parts 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 approximately one eighth of the weight of the child and fluctuates within 400 g.

The activity of the central nervous system and PNS is greatly reduced in the first few days after birth. This may be in the abundance of new irritating factors for the baby. This is how the plasticity of the nervous system is manifested, 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 simultaneously interact - inhibition and excitation. The rate at which these states change determines the types of the nervous system. While one section of the CNS center is excited, the other is slowed down. This is the reason for the peculiarities of intellectual activity, such as attention, memory, concentration.

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

Types of the nervous system are divided into four types.

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

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

CNS protection

The anatomy of the nervous system is very complex. The CNS and PNS suffer from the effects of stress, overexertion, and malnutrition. Vitamins, amino acids and minerals are necessary for the normal functioning of the central nervous system. Amino acids are involved in brain function and are building material for neurons. Having figured out why and what vitamins and amino acids are needed for, it becomes clear how important it is to provide the body necessary quantity 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.

Beam damage, congenital pathologies and anomalies in the development of the brain, 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 you suspect an oncological disease of the central nervous system, an analysis is prescribed - the histology of the affected departments, 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. With benign formations, histology is also performed.

There are many nerve endings in the human body, damage to which can cause a number of problems. Damage often leads to a violation of the mobility of a part of the body. For example, an injury to the hand can lead to pain in the fingers and impaired movement. 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 any related problems, you should be examined by a specialist.