The structure of the nervous tissue. neurons, neuroglia

neuroglia is an environment surrounding neurocytes and performing supporting, delimiting, trophic and protective functions in the nervous tissue. The selectivity of metabolism between nervous tissue and blood is ensured, in addition to the morphological features of the capillaries themselves (solid endothelial lining, dense basement membrane), also by the fact that the processes of gliocytes, primarily astrocytes, form a layer on the surface of the capillaries that delimits neurons from direct contact with the vascular wall. . Thus, the blood-brain barrier is formed.

Neuroglia is made up of cells that are divided into two genetically distinct types:

1) Gliocytes (macroglia);

2) Glial macrophages (microglia).

Gliocytes

Gliocytes, in turn, are divided into:

1) ependymocytes; 2) astrocytes; 3) oligodendrocytes.

Ependymocytes form a dense epithelial-like layer of cells lining the spinal canal and all the ventricles of the brain.

Ependymocytes are the first of the neural tube glioblasts to differentiate, performing delimiting and supporting functions at this stage of development. On the inner surface of the neural tube, elongated bodies form a layer of epithelial-like cells. On the cells facing the cavity of the neural tube canal, cilia are formed, the number of which on one cell can reach up to 40. The cilia apparently contribute to the movement of the cerebrospinal fluid. Long processes depart from the basal part of the ependymocyte, which, branching, cross the entire neural tube and form the apparatus supporting it. These processes on the outer surface take part in the formation superficial glial limiting membrane, which separates the substance of the tube from other tissues.

After birth, ependymocytes gradually lose their cilia, retaining them only in some parts of the central nervous system (midbrain aqueduct).

In the region of the posterior commissure of the brain, ependymocytes perform a secretory function and form a "subcommissural organ" that secretes a secret that is believed to be involved in the regulation of water metabolism.

Ependymocytes that cover the choroid plexuses of the ventricles of the brain have a cubic shape; in newborns, cilia are located on their surface, which are later reduced. The cytoplasm of the basal pole forms numerous deep folds, contains large mitochondria, inclusions of fat, and pigments.

astrocytes - These are small star-shaped cells, with numerous processes diverging in all directions.

There are two types of astrocytes:

1) protoplasmic;

2) fibrous (fibrous).

Protoplasmic astrocytes

¨Localization - the gray matter of the brain.

¨Dimensions - 15-25 microns, have short and thick highly branched processes.

¨The core is large, oval, light.

¨Cytoplasm - contains a small amount of cisterns of the endoplasmic reticulum, free ribosomes and microtubules, rich in mitochondria.

¨Function - delimitation and trophic.

fibrous astrocytes.

¨Localization - white matter of the brain.

¨Sizes - up to 20 microns, have 20-40 smoothly contoured, long, weakly branching processes that form glial fibers that form a dense network - the supporting apparatus of the brain. The processes of astrocytes on the blood vessels and on the surface of the brain form perivascular glial boundary membranes with their terminal extensions.

¨Cytoplasm - when electron microscopic examination is light, holds few ribosomes and elements of the granular endoplasmic reticulum, is filled with numerous fibrils with a diameter of 8-9 nm, which in the form of bundles go into processes.

The nucleus is large, light, the nuclear membrane sometimes forms deep folds, and the karyoplasm is characterized by a uniform electron density.

¨Function - supporting and isolation of neurons from external influences.

Oligodendrocytes - the most numerous and polymorphic group of gliocytes responsible for the production of myelin in the CNS.

¨Localization - they surround the bodies of neurons in the central and peripheral nervous system, are part of the sheaths of nerve fibers and nerve endings.

The cells are very small.

¨Shape - different parts of the nervous system are characterized by different shapes of oligodendrocytes (oval, angular). Several short and weakly branched processes depart from the cell body.

¨Cytoplasm - its density is close to that of nerve cells, does not contain neurofilaments.

¨Function - perform a trophic function, participating in the metabolism of nerve cells. They play a significant role in the formation of membranes around the processes of cells, while they are called neurolemmocytes (Schwann cells), participate in water-salt metabolism, degeneration and regeneration processes.

text_fields

arrow_upward

glia- the structure of the nervous system, formed by specialized cells of various shapes that fill the spaces between neurons or capillaries, making up 10% of the brain volume.

Glial cells are 3-4 times smaller than nerve cells, their number in the central nervous system of mammals reaches 140 billion. With age, the number of neurons in the brain decreases, and the number of glial cells increases.

Types of glia

text_fields

arrow_upward

There are the following types of glia: astroglia, oligodendroglia, microglia

A - fibrous astrocyte; B - protoplasmic astrocyte; B - microglia; G - oligodendrogliocytes

The number of glial elements in brain structures

text_fields

arrow_upward

The number of different forms of glial cells depends on the structure of the central nervous system (see Table 15.1).

Functions of neuroglia

text_fields

arrow_upward

astroglia - Represented by multi-processed cells. Their sizes range from 7 to 25 microns. Most of the processes end on the walls of the vessels. The nuclei contain DNA, the protoplasm has the Golgi apparatus, centrisome, mitochondria. Astroglia serves as a support for neurons, provides reparative processes of nerve trunks, insulates the nerve fiber, and participates in the metabolism of neurons.

Oligodendroglia - These are cells that have one process. The amount of oligodendroglia increases in the cortex from the upper layers to the lower ones. In subcortical structures, there are more oligodendroglia in the brainstem than in the cortex. It is involved in the myelination of axons, in the metabolism of neurons.

microglia - the smallest glial cells, belong to the wandering cells. They are formed from the structures of the membranes of the brain, penetrate into the white, and then into the gray matter of the brain. Microglial cells are capable of phagocytosis.

Features of glial cells

text_fields

arrow_upward

One of the features of glial cells is their ability to change their size. The change in the size of glial cells is of a rhythmic nature: the phases of contraction - 90 s, relaxation - 240 s, i.e. it is a very slow process. The average frequency of rhythmic changes varies from 2 to 20 per hour. In this case, the processes of the cell swell, but do not shorten in length.

Glial activity changes under the influence of various biologically active substances: serotonin causes a decrease in the indicated "pulsation" of oligodendroglial cells, norepinephrine - an increase. Chlorpromazine works in the same way as norepinephrine. The physiological role of the “pulsation” of glial cells is to push through the axoplasm of the neuron and influence the fluid flow in the intercellular space.

Physiological processes in the nervous system largely depend on the myelination of nerve cell fibers. In the central nervous system, myelination is provided by oligodendroglia, and in the peripheral nervous system, by Schwann cells.

Glial cells do not have impulse activity, like nerve cells, however, the glial cell membrane has a charge that forms membrane potential. Its changes are slow, depend on the activity of the nervous system, and are caused not by synaptic influences, but by changes in the chemical composition of the intercellular environment. The membrane potential of glia is approximately 70-90 mV.

Glial cells are capable of propagating potential changes among themselves. This propagation comes with a decrement (with damping). When the distance between the irritating and recording electrodes is 50 μm, the propagation of excitation reaches the registration point in 30-60 ms. The spread of excitation between glial cells is facilitated by special gap junctions of their membranes. These contacts have reduced resistance and create conditions for electrotonic current propagation from one glial cell to another.

Since glia is in close contact with neurons, the processes of excitation of nerve elements affect the electrical phenomena in the glial elements. This effect is associated with the fact that the membrane potential of glia depends on the concentration of K + in the environment. During excitation of the neuron and repolarization of its membrane, the entry of K + ions increases. This significantly changes its concentration around the glia and leads to depolarization of its cell membranes.

secretory neurons. In some nuclei of the anterior hypothalamus of the brain (for example, in the supraoptic and paraventricular) there are cellular systems consisting of specialized neurons - large secretory neurons.

The latter are characterized by typical neurons organelles. They are exposed to other neurons through synaptic contacts. However, their responses, along with membrane depolarization and neurotransmitter release, also include the release of peptide neurohormones into the blood or tissue fluids. In appearance, these cells are similar to multipolar neurons.

They have several short dendrites and one axon. On the dendrites and the body of secretory neurons, numerous synapses are revealed - places for switching impulses from neurons located in the nuclear centers of the brain. Neurosecretion granules (eg, oxytocin and vasopressin) are determined in the cytoplasm and along the axon of secretory neurons. Neurosecretion granules are excreted into the blood or fluid of the ventricles of the brain. Secretory neurons of the hypothalamus are involved in the interactions of the nervous and humoral systems of regulation.

neuroglia. In the process of development of the tissues of the nervous system, glioblasts develop from the material of the neural tube, as well as the neural crest. The result of glioblastic differentiation is the formation of neuroglial cell differons. They perform supporting, delimiting, trophic, secretory, protective and other functions. Neuroglia creates a constant, stable internal environment for the nervous tissue, providing tissue homeostasis and normal functioning of nerve cells. According to the structure and localization of cells, ependymal glia, astrocytic glia and oligodendroglia are distinguished. Often these varieties of glia are united by the generalized concept of "macroglia".

ependymal glia has an epithelioid structure. It lines the central canal of the spinal cord and the cerebral ventricles. As an ependymal epithelium, this type of neuroglia belongs to the neuroglial type of epithelial tissues. The protrusions of the pia mater of the brain into the lumen of its ventricles are covered with cuboidal ependymocytes. They take part in the formation of cerebrospinal fluid. In the wall of the 3rd ventricle of the brain there are specialized cells - tanycytes, which provide a connection between the contents of the ventricle and the blood due to ultrafiltration of the elements of the cerebrospinal fluid.

Astrocyte glia is the supporting structure (skeleton) of the spinal cord and brain. In astrocyte glia, two types of cells are distinguished: protoplasmic and fibrous astrocytes. The first of them are located mainly in the gray matter of the brain. They have short and thick, often flattened processes. The second - are in the white matter of the brain. Fibrous astrocytes have numerous processes containing argyrophilic fibrils. Due to these fibrils, the glial backbone and delimiting membranes in the nervous system, the boundary membranes around the blood vessels and the so-called "legs" of the astrocyte processes on the blood vessels are formed.

Oligodendroglia consists of differently differentiated cells - oligodendrocytes. They tightly surround the bodies of neurons and their processes all the way to the terminal branches. There are several types of oligodendrocytes. In the organs of the central nervous system, oligodendroglia is represented by small process cells called gliocytes. Around the bodies of sensitive neurons of the spinal ganglia are ganglion gliocytes (mantle gliocytes).

Outgrowths of nerve cells accompany neurolemmocytes, or Schwann cells. The source of their development in the peripheral nerves, according to some authors, is the ectomesenchyme of the neural crest.

Functions of oligodendrogliocytes are diverse and extremely important for the normal activity of nerve cells. They provide trophic neurons. In a single metabolic system "neuron-glia" there is an interchange of some enzymes, proteins and RNA. Oligodendrocytes play an essential role in the processes of excitation and inhibition of neurons and in the conduction of nerve impulses along their processes.

So, neurolemmocytes Together with the processes of neurons, they form myelinated and unmyelinated nerve fibers of the peripheral nervous system, while performing the role of insulators that prevent the scattering of impulses. Oligodendrocytes are involved in the regulation of water-salt balance in the nervous system. They can swell, redistribute ions, etc. Specialized gliocytes of nerve endings are involved in the processes of reception, as well as in the transmission of a nerve impulse to working structures.

In addition to macroglia in the nervous system There is also microglia. The source of its development is the mesenchyme, and microglial cells are glial macrophages and belong to neuroglia only on the basis of histotopography. Microglial cells can multiply, show phagocytic activity, synthesize antigens that are not characteristic of the body, which is observed in some diseases.

Educational video - the structure of a neuron

You can download this video and view it from another video hosting on the page:

Neuroglia is a collection of cells of the nervous tissue. Neuroglia performs trophic, delimiting, secretory and protective functions.

Macroglia and microglia are isolated in the CNS.

Macroglia are of neural origin and are subdivided into epindemocytes, astrocytes, and oligodendrocytes. Epidemocytes line the ventricles of the brain and the central canal of the spinal cord. Astrocytes perform supporting and delimiting functions. Oligodendrocytes are involved in the myelination of axons.

Microglia are phagocytic, process-like cells that are located in the gray and white matter of the brain.

In the peripheral nervous system, neuroglia are represented by lemmocytes (Schwann cells), satellite cells.

Schwann cells form along the axons of the peripheral nervous system. Provide myelination of neurons, perform supporting and trophic functions. Satellite cells provide life support for neurons in the peripheral nervous system.

2nd part Reflex arcs can be of two types:

simple - monosynaptic reflex arcs (reflex arc of the tendon reflex), consisting of 2 neurons (receptor (afferent) and effector), there is 1 synapse between them;

complex - polysynaptic reflex arcs. They include 3 neurons (there may be more) - receptor, one or more intercalary and effector.

12)question General plan of the structure of the nervous system.

All nervous system divided into central and peripheral. to the central nervous system includes the brain and spinal cord. From them all over the body diverge nervous fibers - peripheral nervous system. It connects the brain with the sense organs and with the executive organs - the muscles and glands.

2) Development

human nervous system develops from the outer germ layer - the ectoderm.

3) features

The main functions of the nervous system are the receipt, storage and processing of information from the external and internal environment, the regulation and coordination of the activities of all organs and organ systems.

13)question Peripheral nervous system:

divisions: sensory nerves, motor nerves are divided into: somatic and autonomic divided into: sympathetic and parasympathetic

14) question Cranial and spinal nerves

to classification and functions: Numbering Name Functions
I Olfactory Susceptibility to smells
II Visual Transmission of visual stimuli to the brain
III Oculomotor Eye movements, pupillary reaction to light exposure
IV Block Movement of the eyes down, to the outside
V Trigeminal Facial, oral, pharyngeal sensitivity; the activity of the muscles responsible for the act of chewing
VI Abductor Movement of the eyes to the outside
VII Facial Muscle movement (facial, stirrup); activity of the salivary gland, sensitivity of the anterior part of the tongue
VIII Auditory Transmission of sound signals and impulses from the inner ear
IX Glossopharyngeal Movement of the levator pharynx muscle; activity of paired salivary glands, sensitivity of the throat, middle ear cavity and auditory tube
X Wandering Motor processes in the muscles of the throat and some parts of the esophagus; providing sensitivity in the lower part of the throat, partly in the ear canal and eardrums, the dura mater; smooth muscle activity (gastrointestinal tract, lungs) and cardiac
XI Additional Abduction of the head in various directions, shrugging the shoulders and bringing the shoulder blades to the spine
XII Hyoid Movement and movements of the tongue, acts of swallowing and chewing

15) question Autonomic nervous system:

Centers of the autonomic nervous system. The highest autonomic center is the hypothalamus. The hypothalamus is an accumulation of about 50 pairs of nuclei, which are combined into groups: preoptic anterior, middle, external and posterior. The role of various groups of nuclei of the hypothalamus is determined by their relationship with the sympathetic or parasympathetic divisions of the ANS. Irritation of the anterior nuclei of the hypothalamus causes changes in the body, similar to those observed when the parasympathetic nervous system is activated. Irritation of the posterior nuclei of the hypothalamus is accompanied by effects similar to stimulation of the sympathetic nervous system. The main structural and functional features of the hypothalamus are the following:
The neurons of the hypothalamus have a receptor function - they are able to directly capture changes in the chemical composition of blood and cerebrospinal fluid. This is achieved, firstly, due to the powerful network of capillaries and their exceptionally high permeability; secondly, due to the fact that there are cells in the hypothalamus that are selectively sensitive to changes in blood parameters. These "receptor" neurons in the hypothalamus have little to no adaptation. They generate impulses until one or another indicator of the body is normalized as a result of the adaptive work of vegetative effectors.
The hypothalamus has extensive bilateral connections with the limbic system, with the cerebral cortex, with the central gray matter of the midbrain, and with the somatic nuclei of the brain stem. These connections are carried out not only by nerve cells, but also by neurosecretory cells, the axons of which go to the limbic system, the thalamus, and the medulla oblongata.
The hypothalamus produces its own hormones involved in the regulation of autonomic functions. The effector hormones oxytocin and vasopressin are produced in the neurons of the nuclei of the anterior group of the hypothalamus (supraoptic and paraventricular nuclei) in an inactive state, then enter the neurohypophysis, where they are activated and then secreted into the blood. Releasing hormones of the hypothalamus (liberins) stimulate the function of the pituitary gland, and statins (inhibiting hormones) inhibit it. These hormones are produced by neurons in the arcuate and ventromedial nuclei of the hypothalamus and regulate the production of tropic pituitary hormones. Libirins and statins of the hypothalamus are released from the nerve processes in the area of the median eminence and through the hypothalamic-pituitary portal system with blood enter the adenohypophysis. Regulation according to the principle of negative feedback, in which the hypothalamus, pituitary gland and peripheral endocrine glands participate, is also carried out in the absence of influences from the overlying parts of the CNS.
In the hypothalamus there are centers for the regulation of water and salt metabolism (supraoptic and paraventricular nuclei); protein, carbohydrate and fat metabolism; centers of regulation of the cardiovascular system, endocrine glands; center of hunger (lateral hypothalamic nucleus) and saturation (ventrolateral nucleus); thirst center; drinking cessation center; center for regulation of urination; center of sleep and wakefulness (suprachiasmatic nucleus); center of sexual behavior; centers that provide emotional experiences of a person, and other centers involved in the processes of adaptation of the body.

Peripheral department:
autonomic (autonomous) nerves, branches and nerve fibers emerging from the brain and spinal cord;
vegetative (autonomous, visceral) plexus;
nodes (ganglia) of vegetative (autonomous, visceral) plexuses;
sympathetic trunk (right and left) with its nodes (ganglia), internodal and connecting branches and sympathetic nerves;
end nodes (ganglia) of the parasympathetic part of the autonomic nervous system.

The autonomic nervous system performs a number of functions:
Controls the activity of internal organs, blood and lymphatic vessels, innervating smooth muscle cells and glandular epithelium.
Regulates metabolism, adapting its level to a decrease or increase in organ function. Thus, it performs an adaptive-trophic function, which is based on the transport of axoplasm - the process of continuous movement of various substances from the body of the neuron along the processes in the tissue. Some of them are included in the metabolism, others activate the metabolism, improving tissue trophism.

Coordinates the work of all internal organs, maintaining the constancy of the internal environment of the body.

Terminal brain.

1) localization of gray and white matter

White matter of the brain consists of a large number of nerve fibers that fill the space between the cerebral cortex and the basal nuclei. They spread in different directions and form the pathways of the cerebral hemispheres.

17. Spinal cord .● The spinal cord looks like a thick cord, the diameter of which is about 1 cm. The length of the spinal cord in an adult is 43 cm. The mass is from 34 to 38 grams, which is 2% of the mass of the brain. It is somewhat flattened in the anterior-posterior direction. The spinal cord has a segmental structure. At the level of the foramen magnum, it passes into the brain, and at the level of 1-2 lumbar vertebrae, it ends with a cerebral cone, from which the terminal (terminal) thread departs, surrounded by the roots of the lumbar and sacral spinal nerves. In places where the nerves originate to the upper and lower extremities, there are thickenings - cervical and lumbar (lumbosacral). These thickenings are not expressed in uterine development. Cervical thickening - at the level of the V-VI cervical segments and lumbosacral in - the region of III-IV lumbar segments. Morphological boundaries between segments of the spinal cord do not exist, so the division into segments is functional.

The anterior median fissure and posterior median sulcus divide the spinal cord into two symmetrical halves. Each half, in turn, has two weakly expressed longitudinal grooves, from which the anterior and posterior roots of the spinal nerves emerge. The anterior root consists of processes of motor (motor, efferent, centrifugal) nerve cells located in the anterior horn of the spinal cord. The posterior root, sensitive (afferent, centripetal), is represented by a set of central processes of pseudo-unipolar cells penetrating the spinal cord, the bodies of which form the spinal ganglion.

31 pairs of spinal nerves depart from the spinal cord: 8 pairs of cervical, 12 pairs of thoracic, 5 pairs of lumbar, 5 pairs of sacral and a pair of coccygeal. The section of the spinal cord corresponding to two pairs of roots (two anterior and two posterior) is called a segment.

The anterior roots perform a different function. The posterior roots contain only afferent fibers and conduct sensory impulses to the spinal cord, while the anterior roots contain efferent fibers that transmit motor impulses from the spinal cord to the muscles.

● Structure and functions. The spinal cord is located in the spinal canal, it is covered with membranes. The spinal cord begins at the level of the foramen magnum of the skull and ends at the level of the second lumbar vertebra. Below are the sheaths of the spinal cord surrounding the roots of the lower spinal nerves. If we examine the transverse section of the spinal cord, we can see that the central part of it is occupied by a gray matter shaped like a butterfly, consisting of nerve cells. In the center of the gray matter is visible a narrow central canal filled with cerebrospinal fluid. Outside of the gray matter is the white matter. It contains nerve fibers that connect the neurons of the spinal cord with each other and with the neurons of the brain. The spinal nerves depart from the spinal cord in symmetrical pairs, there are 31 pairs of them. Each nerve starts from the spinal cord in the form of two strands, or roots, which, when combined, form a nerve. The spinal nerves and their branches travel to the muscles, bones, joints, skin, and internal organs. The spinal cord in our body performs two functions: reflex and conduction. The reflex function of the spinal cord consists in the response of the nervous system to irritation. In the spinal cord there are centers of many unconditioned reflexes, for example, reflexes that provide movement of the diaphragm and respiratory muscles. The spinal cord (under the control of the brain) regulates the functioning of internal organs: the heart, kidneys, and digestive organs. In the spinal cord, reflex arcs are closed that regulate the functions of the flexor and extensor skeletal muscles of the trunk and limbs. Reflexes are congenital (which can be determined from birth) and acquired (formed in the process of life during learning), they are closed at various levels. For example, the knee jerk closes at the level of the 3rd-4th lumbar segments. Checking it, the doctor is convinced of the safety of all elements of the reflex arc, including segments of the spinal cord. The conductive function of the spinal cord is to transmit impulses from the periphery (from the skin, mucous membranes, internal organs) to the center (the brain) and vice versa. The conductors of the spinal cord, which make up its white matter, carry out the transmission of information in the ascending and descending direction. An impulse about external influences is sent to the brain, and a certain sensation is formed in a person (for example, you stroke a cat, and you get a feeling of something soft and smooth in your hand) Centrifugal fibers come out of the spinal cord, along which impulses go to organs and tissues. Injury to the spinal cord disrupts its functions: the areas of the body located below the site of injury lose sensitivity and the ability to voluntarily move. The brain has a great influence on the activity of the spinal cord. All complex movements are under the control of the brain: walking, running, labor activity. The spinal cord is a very important anatomical structure. Its normal functioning ensures the entire life of a person. Knowledge of the features of the structure and functioning of the spinal cord is necessary for the diagnosis of diseases of the nervous system.

●The anterior roots of the spinal cord are the nerve endings contained in the gray matter. The posterior roots are sensitive cells, or rather, their processes. The spinal ganglion is located at the junction of the anterior and posterior roots. This knot creates sensitive cells.

The roots of the human spinal cord extend from the spinal column on both sides. On the left and right sides, thirty-one roots depart.

A segment is a specific part of an organ located between each pair of such roots. If you remember the mathematics, it turns out that each person has thirty-one such segments:

five segments fall on the lumbar region;

five sacral segments;

eight cervical;

twelve chest;

one coccygeal.

On a transverse section of the spinal cord, the gray matter has the shape of a butterfly or the letter “H”, it has a wider anterior horn and a narrow posterior horn. In the anterior horns are large nerve cells - motor neurons.

The gray matter of the posterior horns of the spinal cord is heterogeneous. The bulk of the nerve cells of the posterior horn form their own nucleus, and at the base of the posterior horn, the thoracic nucleus is noticeably well outlined by a layer of white matter, consisting of large nerve cells.

The cells of all nuclei of the posterior horns of the gray matter are, as a rule, intercalary, intermediate, neurons, the processes of which go in the white matter of the spinal cord to the brain.

The composition of cells located in the posterior and anterior horns of the spinal cord is heterogeneous. Sensory cells are located in the posterior horns, the processes of which pass through the midline of the spinal cord into the lateral column of the opposite side and form the path of superficial sensitivity. At the base of the posterior horn, a separate group of cells belonging to the cerebellar proprioception system is distinguished. The processes of these cells are sent to the lateral columns of the spinal cord (the anterior one crosses at the level of its own segment, the posterior one goes to the lateral funiculus of its side) and, as part of the spinal cerebellar pathways, reach the nucleus of the tent of the cerebellar vermis.

In addition, a large number of intercalary neurons are located in the anterior and posterior horns of the spinal cord, which ensure the closure of reflex arcs, the connection between the higher and lower segments of the spinal cord, the connection between the halves of the spinal cord, which ensure desynchronization of the work of? inhibition (Renshaw cells). Between the gray matter cells are glial cells.

18. Brain .

● The brain consists of five parts: medulla oblongata, cerebellum, midbrain, diencephalon and forebrain.

The medulla oblongata is a continuation of the spinal cord. It contains the nuclei of VIII-XII pairs of cranial nerves. Here are vital centers for the regulation of respiration, cardiovascular activity, digestion, and metabolism. The nuclei of the medulla oblongata are involved in the implementation of unconditioned food reflexes (separation of digestive juices, sucking, swallowing), protective reflexes (vomiting, sneezing, coughing, blinking). The conductor function of the medulla oblongata is to transmit impulses from the spinal cord to the brain and vice versa.

The cerebellum and pons form the hindbrain. Nerve pathways pass through the bridge, connecting the forebrain and midbrain with the medulla oblongata and spinal cord. The nuclei of the V-VIII pairs of cranial nerves are located in the bridge. The gray matter of the cerebellum is outside and forms a cortex with a layer of 1-2.5 mm. The cerebellum is formed by two hemispheres connected by a worm. The nuclei of the cerebellum provide coordination of complex motor acts of the body. The cerebral hemispheres through the cerebellum regulate skeletal muscle tone and coordinate body movements. The cerebellum takes part in the regulation of some autonomic functions (blood composition, vascular reflexes).

The midbrain is located between the pons and the diencephalon. It consists of the quadrigemina and the legs of the brain. Through the midbrain, ascending paths pass to the cerebral cortex and cerebellum and descending paths to the medulla oblongata and spinal cord (conductor function). The midbrain contains the nuclei of the III and IV pairs of cranial nerves. With their participation, primary orienting reflexes to light and sound are carried out: eye movement, head turning towards the source of irritation. The midbrain is also involved in maintaining skeletal muscle tone.

The diencephalon is located above the midbrain. Its main divisions are the thalamus (visual tubercles) and the hypothalamus (hypothalamus). Centripetal impulses from all receptors of the body (with the exception of the olfactory one) pass through the thalamus to the cerebral cortex. Information receives the corresponding emotional coloring in the thalamus and is transmitted to the cerebral hemispheres. The hypothalamus is the main subcortical center for the regulation of the autonomic functions of the body, all types of metabolism, body temperature, the constancy of the internal environment (homeostasis), and the activity of the endocrine system. The hypothalamus contains the centers of satiety, hunger, thirst, and pleasure. The nuclei of the hypothalamus are involved in the regulation of the alternation of sleep and wakefulness.

The forebrain is the largest and most developed part of the brain. It is represented by two hemispheres - left and right, separated by a longitudinal slit. The hemispheres are connected by a thick horizontal plate - the corpus callosum, which is formed by nerve fibers running transversely from one hemisphere to another. Three furrows - central, parietal-occipital and lateral - divide each hemisphere into four lobes: frontal, parietal, temporal and occipital. Outside, the hemisphere is covered with a layer of gray matter - the cortex, inside are white matter and subcortical nuclei. The subcortical nuclei are a phylogenetically ancient part of the brain that controls unconscious automatic actions (instinctive behavior).

The cerebral cortex has a thickness of 1.3-4.5 mm. Due to the presence of folds, convolutions and furrows, the total area of the cortex of an adult is 2000-2500 cm2. The cortex consists of 12-18 billion nerve cells arranged in six layers.

Although the cerebral cortex functions as a whole, the functions of its individual sections are not the same. The sensory (sensitive) zones of the cortex receive impulses from all receptors in the body. Thus, the visual zone of the cortex is located in the occipital lobe, the auditory zone is located in the temporal lobe, etc. In the associative zones of the cortex, storage, evaluation, comparison of incoming information with previously received information, etc. are carried out. Thus, in this zone, the processes of memorization and learning take place. , thinking. Motor (motor) zones are responsible for conscious movements. From them, nerve impulses are sent to the striated muscles.

The white matter of the forebrain is formed by nerve fibers that connect different parts of the brain.

Thus, the cerebral hemispheres are the highest part of the CNS, providing the highest level of adaptation of the body to changing environmental conditions. The cerebral cortex is the material basis of mental activity.

● The lateral ventricles are cavities in the brain that contain CSF. Such ventricles are the largest in the ventricular system. The left ventricle is called the first, and the right - the second. It is worth noting that the lateral ventricles communicate with the third ventricle using the interventricular or Monroe foramina. Their location is below the corpus callosum, on both sides of the midline, symmetrically. Each lateral ventricle has an anterior horn, posterior horn, body, and inferior horn.

The third ventricle is located between the visual tubercles. It has an annular shape, since intermediate visual tubercles grow into it. The walls of the ventricle are filled with central gray medulla. It contains subcortical vegetative centers. The third ventricle communicates with the aqueduct of the midbrain. Behind the nasal commissure, it communicates through the interventricular foramen with the lateral ventricles of the brain.

The fourth ventricle is located between the medulla oblongata and the cerebellum. The arch of this ventricle is the cerebral sails and the worm, and the bottom is the bridge and the medulla oblongata.

This ventricle is a remnant of the cavity of the brain bladder, the Ventricles of the brain located behind. That is why this is a common cavity for the parts of the hindbrain that make up the rhomboid brain - the cerebellum, medulla oblongata, isthmus and bridge.

The fourth ventricle is similar in shape to a tent in which you can see the bottom and roof. It is worth noting that the bottom or base of this ventricle has a diamond shape, it is, as it were, pressed into the posterior surface of the bridge and the medulla oblongata. Therefore, it is customary to call it a rhomboid fossa. The canal of the spinal cord is open in the posterior inferior corner of this fossa. At the same time, in the anterior upper corner, the fourth ventricle communicates with the water supply.

The lateral angles end blindly in the form of two pockets that fold ventrally near the inferior cerebellar peduncles.

The lateral ventricles of the brain are relatively large and C-shaped. In the cerebral ventricles, the synthesis of cerebrospinal fluid or cerebrospinal fluid occurs, which after that it ends up in the subarachnoid space. If the outflow of cerebrospinal fluid from the ventricles is disturbed, a person is diagnosed with hydrocephalus.

●WHAT IS THE HUMAN MENAIN

The human brain consists of soft tissues that are subject to mechanical damage. The meninges directly cover the brain, keeping it safe while walking, running, or being hit accidentally.

Liquor constantly circulates between the layers. Cerebrospinal fluid flows around the human brain, so that it is constantly in limbo, which provides additional cushioning.

In addition to protection against mechanical stress, each of the three shells performs several secondary functions.

FUNCTIONS OF THE BRAIN

The human spinal cord is protected by three membranes, originating in the mesoderm (middle germ layer). Each layer has its own functions and anatomical structure.

It is customary to distinguish:

anatomical arrangement of the meninges The hard shell is the densest among all the protective layers. The outer surface is adjacent to the inner part of the skull. The hard shell of the brain is involved in the formation of processes that separate several important areas from each other. Among them: the cerebral crescent, the crescent and sickle of the cerebellum, the diaphragm of the saddle.

The arachnoid membrane - in addition to the protective function, is involved in the circulation of cerebrospinal fluid. Forms an interarachnoid space through which cerebrospinal fluid circulates.

Soft or choroid - with the help of glial tissue grows together with the surface of the spinal cord. Inside the layer are arteries and numerous vessels that envelop the brain. The layer is involved in the work of the blood supply system.

●Cerebral pathways

Allocate associative, commissural and projection pathways of the brain. The first pathways of the brain connect different parts of the gray matter located in the same hemisphere. Among them are short and long. Short associative pathways are located within the brain lobe - intralobar fibers. They are also subdivided into intracortical (arcuate), when the bundle of fibers does not leave the cortex and goes around the gyrus in the form of an arc; and extracortical, when the nerve pathway extends beyond the gray matter. Long associative pathways connect groups of nerve cells that lie in the same hemisphere, but in its different lobes. The most significant of them include the superior longitudinal bundle (connects the cortex of the frontal, parietal and occipital lobes), the lower longitudinal bundle (connects the temporal and occipital lobes) and the uncinate bundle (connects the frontal lobe with the anterior part of the temporal). Commissural, or adhesive, nerve pathways connect areas of gray matter in different hemispheres. With their help, the activity of similar nerve centers of the cerebral hemispheres is coordinated. Transitions of commissural fibers from one hemisphere to another form adhesions. There are three of them: corpus callosum, anterior commissure, and fornix commissure. The corpus callosum is formed by fibers connecting the new parts of the brain; in the white matter of the hemispheres, these fibers diverge in a fan-like fashion. The knee and beak of the corpus callosum carry fibers from the frontal lobes of the brain; in the white matter, bundles of these fibers form frontal forceps on the sides of the longitudinal fissure of the brain. Sections of the cortex of the central gyri, temporal, parietal lobes are connected through the trunk of the corpus callosum. The roller of the corpus callosum carries fibers from the posterior regions of the parietal and occipital lobes. In the white matter on the sides of the longitudinal fissure of the brain, the bundles of these fibers form the occipital forceps. The fornix commissure connects the gray matter of the temporal lobes and the hippocampus of different hemispheres. The anterior commissure consists of fibers coming from the medial areas of the cortex of the temporal lobes and the cortex of the region of the olfactory triangles. Projection pathways of the brain

In addition to associative and commissural pathways, there are also projection pathways that connect the gray matter of the cerebral hemispheres with the underlying structures of the central nervous system, including the spinal cord, as well as simply various clusters of neurons, various parts of the central nervous system among themselves. Thanks to the projection fibers, the interconnection and joint activity of the structures of the central nervous system is carried out. Among the projection pathways, ascending (afferent) and descending (efferent) are distinguished. The former carry information received from receptors of both the external and internal environment to the brain. In this regard, according to the nature of the information, ascending paths are exteroceptive (impulses from pain, temperature, tactile receptors of the skin and impulses from the sense organs - visual, gustatory, auditory, olfactory), proprioceptive (carry impulses from receptors of the muscle-tendon-tendon - articular apparatus about the position of the body, muscular work, etc.) and interoceptive (convey information about the internal environment of the body received from the receptors of internal organs and blood vessels).

Exteroceptive pathways of the brain

The exteroceptive pathways of the brain, carrying information from the receptor apparatus of the skin, include the lateral and anterior spinal-thalamic pathways. Temperature and pain sensitivity is carried out along the lateral spinal-thalamic pathway. The path consists of two neurons. The body of the first lies in the spinal ganglion, its dendrites end in the skin and mucous membranes. Along the axons, impulses arrive in the posterior roots to the spinal cord, where they pass in the posterior horns to the body of the second neuron. In the spinal cord, the axon of the second neuron passes to the opposite side (segmental transition). Along the lateral funiculus, the bundle rises to the bulb of the brain, where it is located behind the nucleus of the olive. Along the pons and midbrain, the axon of the second neuron goes to the anterior tubercle of the thalamus and forms a synapse with the neuron body of the thalamocortical projection of the lateral spinal thalamic pathway (it is possible to consider a three-neuron lateral spinal cortical pathway of temperature and pain sensitivity). The axon of this neuron passes through the middle of the posterior femur of the internal capsule and forms synapses with the neurons of the postcentral gyrus cortex. The pathway from touch and pressure receptors is represented by the anterior spinal-thalamic pathway. This path is three-neural. The body of the first neuron is located in the spinal sensory ganglion. The cells give off axons to the dorsal root, from where they pass into the dorsal horn and are interrupted, connecting with the body of the second neuron. In turn, its central processes through the anterior gray commissure penetrate into the anterior horn of the opposite side. As part of the anterior cord, the axon of the second neuron follows to the overlying sections. In the medulla, the fibers merge with the fibers that form the medial loop. In the dorsal lateral nucleus of the thalamus lies the body of the third neuron; here the central process of the second neuron is interrupted. The fibers leaving the nucleus on their way pass through the posterior thigh of the internal capsule into the cortex of the postcentral gyrus, the cortical center of general sensitivity.

Often, when the horns are damaged on one side, the feeling of touch and pressure partially disappears. This is due to the fact that some of the fibers do not cross over to the opposite side and go to the cortex along with other ascending pathways.

proprioceptive pathways in the brain

Proprioceptive pathways include several pathways. The bulbothalamic pathway conducts impulses from the receptors of the musculoskeletal system to the postcentral gyrus. The bodies of the first neurons in the spinal ganglion give off the central processes to the posterior root, from where they pass into the posterior funiculus and further to the thin and wedge-shaped bundles that are located in the medulla oblongata and contain nuclei of the same name, in which the axon of the first connects to the body of the second neuron. Its processes in the inter-olivate layer are formed by the decussation of the medial loops. These fibers, which have passed to the opposite side, are called internal arcuate. Some fibers of the second neuron form posterior and anterior arcuate fibers. They, passing along the lateral funiculus and the lower cerebellar pedicle, conduct impulses of the muscular-articular feeling to the cerebellar vermis. Bypassing the pontine tire, the fibers connect to the body of the third neuron, which is localized in the dorsolateral nucleus of the thalamus. Its processes go into the postcentral gyrus.

spinal cerebellar tract pathways of the brain

The posterior spinal cerebellar path, or Flexig's bundle, is the path of proprioceptive sensitivity from the receptors of the muscular apparatus to the cortex of the cerebellar vermis. From the body of the first neuron, excitation goes along the axon to the posterior horn, to the thoracic nucleus, in which the body of the second neuron is located. There is no crossing of fibers in this path; the axon of the third neuron follows through the lower leg to the cerebellum. As part of this path, the presence of fibers is also noted, through which it is possible to conduct an impulse to the red nucleus, the cerebellar hemispheres and the cortex.

The anterior dorsal cerebellar pathway, or Gowers bundle, is a little more complicated. It differs from the back one in that it makes two crosses and as a result returns to its side.

Among the projection pathways of the descending direction, pyramidal and extrapyramidal motor pathways are distinguished. Along the pyramidal pathways, impulses follow from the cortex to the anterior horns of the spinal cord or to the nuclei of the cranial nerves. In the pyramidal tracts, the cortical-nuclear, lateral and anterior cortical-spinal tracts are distinguished.

The corticonuclear pathway starts from the Betz cells of the lower part of the precentral gyrus and goes to the underlying sections, passing through the knee of the internal capsule. In the medulla oblongata, the fibers cross and end in synapses with the body of the second neuron in the nuclei from III to VI and from IX to XII cranial nerves. The axons of the second neuron exit as cranial nerve fibers and innervate the organs of the head and neck.

The lateral cortico-spinal tract, like the anterior one, comes from the Betz cells of the upper two-thirds of the precentral gyrus. The fibers pass through the beginning of the posterior leg of the internal capsule, the legs of the brain and the bridge. The medulla oblongata is the site of the intersection of the lateral cortical-spinal tract, which then continues to the anterior horns of the spinal cord, where the axon of the first neuron contacts the second, giving motor branches to the muscles. The fibers of the anterior cortical-spinal tract also cross, but in the spinal cord.

Among the extrapyramidal pathways, the red nuclear-spinal, vestibulo-spinal and cortical-bridge-cerebellar pathways are called.

The red nuclear-spinal path starts from the red nucleus and immediately crosses, then goes along the underlying sections to the motor neurons of the spinal cord along the lateral cords.

The vestibulo-spinal path starts from the nuclei of the VIII pair of cranial nerves, which are projected onto the lateral parts of the superior triangle of the rhomboid fossa, and continues to the nuclei of the anterior cords of the spinal cord. This path makes setting reactions possible.

Cortical-pontocerebellar path from the cells of the cortex of all lobes, except for the insular. The axons of these cells (cortical-bridge fibers) pass through the internal capsule. The first neuron is interrupted at the base of the bridge on the nuclei of the second neuron, which give off crossing axons there (transverse fibers of the bridge) going to the cerebellar hemispheres.

19. Cervical plexus.

● The cervical plexus (plexus cervicalis) is formed by the anterior branches of the four upper cervical nerves. Upon exiting through the intervertebral foramen (foramen intervertebrale), these nerves lie on the anterior surface of the deep muscles of the neck at the level of the upper four cervical vertebrae behind the sternocleidomastoid muscle.

The cervical plexus forms sensory, motor (muscular) and mixed branches.

sensitive branches. The sensory branches give rise to the cutaneous nerves of the neck (transverse nerve of the neck, medial, intermediate and lateral supraclavicular nerves, greater auricular nerve and lesser occipital nerve) described above.

motor branches. The motor branches of the cervical plexus innervate

Send your good work in the knowledge base is simple. Use the form below

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

Posted on http://www.allbest.ru/

NORTH CAUCASUS FEDERAL UNIVERSITY

Department of Anatomy and Physiology

Discipline abstract

fundamentals of neuroscience

"Neuroglia. Classification and functions "

Completed by: 3rd year student,

Faculty of Biology,

Institute of Living Systems

Strelnik Alexandra Dmitrievna

Checked by: Doctor of Biological Sciences,

Professor Belyaev Nikolai Georgievich

Stavropol, 2015

Plan

Introduction

1. General ideas about neuroglia 4

2. Classification of glial cells

2.1 Macroglia and its types

2.2 Microglia

2.3 Other glial structures

Conclusion

Bibliography

Introduction

The human brain is made up of hundreds of billions of cells, with nerve cells (neurons) not making up the majority. Most of the volume of the nervous tissue (up to 9/10 in some areas of the brain) is occupied by glial cells (from the Greek to glue). The fact is that a neuron performs a gigantic, very delicate and difficult job in our body, for which it is necessary to free such a cell from everyday activities related to nutrition, removal of toxins, protection from mechanical damage, etc. - this is provided by other, serving cells, i.e. glia cells.

Glial cells were first described in 1846 by R. Virchow, who gave them this name, meaning by it a substance that glues nervous tissue.

The purpose of this abstract is to get acquainted with the available data on neuroglia and to systematize the information received.

When compiling the abstract, scientific literature, information about modern studies of neuroglia, and Internet sources were used.

1 . General ideas aboutneuroglia

It is known that a neuron performs a gigantic, very delicate and difficult work in our body, for which it is necessary to free such a cell from everyday activities related to nutrition, removal of toxins, protection from mechanical damage, etc. The fulfillment of these tasks is provided by other, serving cells, i.e. glia cells. The collection of these cells is called neuroglia.

Neuroglia is a vast heterogeneous group of cells of the nervous tissue that ensures the activity of neurons and performs supporting, trophic, delimiting, barrier, protective and secretory functions. Without neuroglia, neurons cannot exist and function.

Throughout a person's life, glial cells interact with neurons in all parts of the nervous system. The relationship between them develops from the early embryogenesis of the nervous tissue. At the first stage of development, glial cells extend their processes perpendicular to the plane of the breeding zone and are therefore called radial glial cells. The neuron wraps its body around the process of the glial cell and slowly, as it were, climbs up it, moving further and further away from the place of its initial origin to the place of its final location. glia cell astrocyte

The origin of the term neuroglia (from the Greek neuron - nerve and glia - glue) is associated with the initial idea of the presence of a certain substance that fills the space between neurons and nerve fibers and binds them together like glue. Neuroglia was discovered in 1846 by the German scientist R. Virchow. He called it an intermediate substance containing spindle-shaped and stellate cells, which are difficult to distinguish from small neurons. He also saw for the first time that neuroglia separates the nervous tissue from the bloodstream.

Glial cells are 3-4 times smaller than neurons. In the human brain, the content of gliocytes is 5-10 times higher than the number of neurons, and all cells occupy about half of the brain volume. The ratio between the number of gliocytes and neurons in humans is higher than in animals. This means that in the course of evolution the number of glial cells in the nervous system has increased more significantly than the number of neurons.

Unlike neurons, adult gliocytes are capable of dividing. In damaged areas of the brain, they multiply, filling the defects and forming a glial scar. As a person ages, the number of neurons in the brain decreases and the number of glial cells increases.

From the period of embryonic development to extreme old age, neurons and glia conduct a very lively dialogue. Glia influences the formation of synapses and helps the brain determine which neural connections are strengthening or weakening over time (these changes are directly related to the processes of communication and long-term memory). Recent studies have shown that glial cells communicate with each other, affecting the activity of the brain as a whole. Neuroscientists are taking great care to endow glia with new powers. However, one can imagine how excited they are at the thought that a large part of our brain is almost unexplored and, therefore, can still reveal many secrets.

2 . Classification of glial cells

Neuroglia is subdivided into macroglia and microglia. In addition, glial structures that are part of the peripheral nervous system include satellite cells, or mantle cells located in the spinal, cranial and autonomic ganglia, as well as lemmocytes, or Schwann cells.

These types of neuroglia have an even more detailed classification, which will be described below.

2 .1 Macroglia and its types

Macroglia in the embryonic period, like neurons, develops from the ectoderm. Macroglia are subdivided into astrocytic, oligodendrocyte and epidymocytic glia. The basis of these types of macroglia are, respectively, astrocytes, oligodendrocytes and epindimocytes.

astrocytes - these are multi-processed (stellate), the largest forms of gliocytes. They account for about 40% of all gliocytes. They are found in all parts of the central nervous system, but their number is different: in the cerebral cortex they contain 61.5%, in the corpus callosum - 54%, in the brain stem - 33%.

Astrocytes are divided into two subgroups - protoplasmic and fibrous, or fibrous. Protoplasmic astrocytes are found predominantly in the gray matter of the central nervous system. They are characterized by numerous branches of short, thick processes. Fibrous astrocytes are located mainly in the white matter of the central nervous system. Long, thin, slightly branching processes depart from them.

Astrocytes perform four main functions -

Support (support neurons. This function allows you to perform the presence of dense bundles of microtubules in their cytoplasm);

Delimitation (transport and barrier) (separate neurons with their bodies into groups (compartments);

Metabolic (regulatory) - regulation of the composition of the intercellular fluid, the supply of nutrients (glycogen). Astrocytes also ensure the movement of substances from the capillary wall to the plasma membrane of neurons;

Protective (immune and reparative) in case of damage to the nervous tissue, for example, during a stroke, astrocytes can be converted into a neuron.

In addition, astrocytes perform the function of participating in the growth of nervous tissue: astrocytes are able to secrete substances, the distribution of which sets the direction of neuronal growth during embryonic development.

Astrocytes also regulate synaptic signaling. The axon transmits a nerve signal to the postsynaptic membrane due to the release of a neurotransmitter. In addition, the axon releases ATP. These compounds cause calcium to move into the interior of astrocytes, which encourages them to communicate with each other by releasing their own ATP.

Oligodendrocytes - this is an extensive group of diverse nerve cells with short, few processes. Oligodendrocytes in the cerebral cortex contains 29%, in the corpus callosum - 40%, in the brain stem - 62%. They are found in the white and gray matter of the central nervous system. White matter is the site of preferential localization. There they are arranged in rows, dense to the nerve fibers passing here. In the gray matter, they are located along myelinated nerve fibers and around the bodies of neurons, forming close contact with them. Thus, oligodendrocytes surround the bodies of neurons, and also lead to the composition of nerve fibers and nerve endings. In general, oligodendrocytes isolate these formations from neighboring structures and thereby contribute to the conduction of excitation.

They are divided into large (light), small (dark) and intermediate (by size and density). It turned out that these are different stages of development of oligodendrocytes.

Non-dividing light oligodendrocytes are formed as a result of mitotic division of oligodendroblasts. After a few weeks, they turn into intermediate and then after a while - into dark. Therefore, in an adult organism, mainly only dark oligodendrocytes are found. The volume of a dark oligodendrocyte is only 1/4 of a light one. After the end of the growth of the organism, the mitotic division of oligodendroblasts sharply slows down, but does not stop completely. Therefore, the oligodendrocyte population can, albeit slowly, be renewed in the adult.

Oligodendrocytes perform 2 main functions:

The formation of myelin as a component of the insulating sheath of nerve fibers in the central nervous system, which ensures somersault movement of the nerve impulse along the fiber;

Trophic, including participation in the regulation of neuronal metabolism.

epindimocytes form ependymal glia, or ependyma. Ependyma is a single-layer lining of the cavities of the ventricles of the brain and the central canal of the spinal cord, consisting of ependymocytes, which are epithelial-like cells of a cubic or cylindrical shape. Ependymocytes perform supporting, delimiting and secretory functions in the central nervous system. The bodies of ependymocytes are elongated, at the free end there are cilia (lost in many parts of the brain after the birth of an individual). The beating of the cilia promotes the circulation of the cerebrospinal fluid. There are slit-like junctions and plexus bands between neighboring cells, but there are no tight junctions, so that cerebrospinal fluid can penetrate between them into the nervous tissue.

In the lateral parts of the bottom of the third ventricle of the brain are ependymocytes of a special structure, which are called tanycytes. On their apical part, there are no cilia and microvilli, and at the end, facing the medulla, there is a branching process that adjoins neurons and blood vessels. It is believed that these cells transmit information about the composition of the cerebrospinal fluid to the primary capillary network of the pituitary portal system.

Some ependymocytes perform a secretory function, participating in the formation and regulation of the composition of cerebrospinal fluid. Choroid ependymocytes (i.e. ependymocytes lining the surface of the choroid plexus) contain a large number of mitochondria, a moderately developed synthetic apparatus, numerous vesicles and lysosomes.

2 .2 Microglia

Microglia are a collection of small elongated stellate cells with short, few branching processes. Microgliocytes are located along the capillaries in the central nervous system, in white and gray matter and are a variant of wandering cells. The number of microgliocytes in different parts of the brain is relatively low: in the cerebral cortex - 9.5%, in the corpus callosum - 6%, in the brain stem - 8% of all types of gliocytes.

The main function of microglia is protective. Microglial cells are specialized CNS macrophages with significant mobility. They can be activated and multiply in inflammatory and degenerative diseases of the nervous system. To perform the phagocytic function, microgliocytes lose their processes and increase in size. They are able to phagocytose the remnants of dead cells. Activated microglial cells behave like macrophages.

Thus, the brain, separated from the "general" immune system by the blood-brain barrier, has its own immune system, which is represented by microgliocytes, as well as lymphocytes of the cerebrospinal fluid. It is these cells that become active participants in all pathological processes occurring in the brain.

Microglial cells play a very important role in the development of lesions of the nervous system in AIDS. They carry (together with monocytes and macrophages) the human immunodeficiency virus (HIV) throughout the CNS.

2 .3 Other glial structures

These include satellite cells, or mantle cells, and lemmocytes, or Schwann cells.

Satellite cells (mantle cells) cover the bodies of neurons in the spinal, cranial, and autonomic ganglia. They have a flattened shape, a small round or oval core. They provide a barrier function, regulate the metabolism of neurons, capture neurotransmitters.

Lemmocytes (Schwann cells) are characteristic of the peripheral nervous system. They are involved in the formation of nerve fibers, isolating the processes of neurons. They have the ability to produce myelin sheath. They are, in fact, analogues of CNS oligodendrocytes for the PNS.

Conclusion

Neuroglia is an extensive heterogeneous group of elements of the nervous tissue that ensures the activity of neurons and performs supporting, trophic, delimiting, barrier, secretory and protective functions.

Neuroglia is being studied and researched even now, experimentally finding its new properties. Research is being carried out on the transmission of metabolic signals in the neuron-neuroglia system and elucidating the question of the possible role of glia in providing neurons with ATP.

After getting acquainted with the functions of various types of glial cells, it can be concluded that the normal existence and functioning of nerve cells without them would be impossible.

Bibliography

1. Babmindra V.P. Morphology of the nervous system. - L.: LGU, 1985. - p. 160

2. Borisova I.I. The Human Brain and Nervous System: An Illustrated Reference. - M.: For-um, 2009. - p. 112

3. Kamensky M.A., Kamenskaya A.A. Fundamentals of neurobiology: a textbook for university students. - M.: Bustard, 2014. - p. 324

4. Nicholls J.G., Martin A.R., Wallas B.J., Fuchs P.A. From neuron to brain. - M.: Editorial URSS, 2003. - p. 672

5. Prishchepa I.M., Efremenko I.I. Neurophysiology. - Minsk: Higher School, 2013. - p.288

6. Shulgovsky V.V. Fundamentals of neurophysiology: Textbook for university students. - M.: Aspect Press, 2000. - p. 277

Internet resources

1. http://www.braintools.ru/tag/glia - clippings from articles and books on the "glia" section

2. http://scisne.net/a-1101 - Douglas Fields study of neuroglial function

Hosted on Allbest.ru