Gray matter of the spinal cord, substantia grisea (see fig.,), consists mainly of the bodies of nerve cells with their processes that do not have a myelin sheath. In addition to them, in the gray matter there are processes of those nerve cells that are located in other parts of the spinal cord and brain, neuroglia, as well as blood vessels and their accompanying connective tissue.

In the gray matter, there are two lateral parts located in both halves of the spinal cord, and a transverse part connecting them in the form of a narrow bridge - . It continues into the lateral parts, occupying their middle, as lateral intermediate (gray) substance, substantia (grisea) intermedia lateralis.

In the middle sections of the central intermediate gray matter there is a very narrow cavity - central canal, canalis centralis. At different levels of the spinal cord, its lumen in a horizontal section has a different size and shape: in the region of the cervical and lumbar thickenings - oval, and in the thoracic - rounded with a diameter of up to 0.1 mm. In adults, the canal cavity in a number of areas may overgrow. The central canal stretches throughout the entire spinal cord, passing at the top into the cavity of the IV ventricle. Below, in the region of the cerebral cone, the central canal is expanded and its diameter reaches an average of 1 mm; this section of the central canal is called terminal ventricle, ventriculus terminalis.

The tissue surrounding the central canal of the spinal cord and consisting mainly of neuroglia and a small number of neurons with their fibers is called central gelatinous substance, substantia gelatinosa centralis.

The central intermediate (gray) matter surrounding the central canal is divided into two parts. One part is located in front of the canal and is adjacent to the white commissure that connects the anterior cords of both halves of the spinal cord. The other part lies behind the canal. Behind the central intermediate (gray) substance, directly adjacent to the posterior median septum, is located .

Each of the lateral parts of the gray matter forms three protrusions: a thicker anterior one, a narrower posterior one, and between them a small lateral protrusion, which is not expressed at all levels of the spinal cord. The lateral protrusion is especially clearly visible in the lower segments of the cervical part and in the upper segments of the thoracic part of the spinal cord.

Protrusions throughout the spinal cord form gray pillars, columnae griseae. Each of them on the transverse section of the spinal cord receives the name horns, cornu(see fig. , ). Distinguish anterior column, columna ventralis, on the cross section - anterior horn, cornu ventrale, back column, columna dorsalis (posterior horn, сornu dorsale), And lateral column, columna lateralis (lateral horn, cornu laterale).

The anterior horn is much wider, but shorter than the posterior one, and does not reach the periphery of the spinal cord, while the posterior horn, narrower and longer, reaches the outer surface of the brain.

In the posterior horn can be seen apex of the posterior horn, apex cornus dorsalis, - the narrowest part of the dorsal posterior horn, surrounding head of the posterior horn, caputcornus dorsalis, which goes into neck of the posterior horn, cervix cornus dorsalis, and that in turn - in the widest part of the posterior horn - base of the posterior horn, basiscornusdorsalis(see fig.).

The apex of the posterior horn is bordered by an area rich in neuroglia, with a large number of nerve cells, which is called gelatinous substance, substantia gelatinosa.

Nerve cells in the gray matter form clusters - the nuclei, or centers, of the spinal cord, which have their own constant topography (Fig. 883).

1. In front pillar motor nuclei lie, the cells of which send their axons to the composition of the anterior roots of the spinal cord:

1. anterolateral nucleus, nucleus ventrolateralis, which has two parts: the upper one, lying in the segments C IV -C VIII, and the lower one, located in the segments L II -S I;
2. anterior medial nucleus, nucleus ventromedialis, often also represented by two parts: the upper one in C II -L IV and the lower one in S II -Co I; less often these parts do not have a break in the segments (L V –S I);
3. posterolateral nucleus, nucleus dorsolateralis, divided into two parts: the larger upper one in C V–C VIII and the lower one in L III–S II;
4. posterolateral nucleus, nucleus retrodorsolateralis, lies posterior to the previous one. It is represented by two small clusters of cells in C VIII -Th I and in S I -S III;
5. posteromedial nucleus, nucleusdorsomedialis, is represented by a small upper part lying in the upper cervical segment C I, and lower - in the segments Th I -S II ;
6. central nucleus, nucleus centralis, more often located in segments Th I–L III, but may also have an additional part in S I–S V;
7. accessory nerve nucleus, nucleusn. accessorii, usually limited to C I–C VI segments;
8. phrenic nerve nucleusnucleus n. phrenici, occurs in segments C IV–C VII;
9. lumbar dorsal nucleus,nucleus lumbodorsalis, lies in segments L III - S I .

2. In rear pillar sensitive nuclei lie:

1. gelatinous substance, substantia gelatinosa, has the appearance of a crescent on a transverse section, bordering the top of the posterior horn;
2. own nucleus of the posterior horn, nucleus proprius cornus posterioris(BNA), located in its central part, occupies almost its entire area and extends along the entire posterior column (C I –Co I);
3. secondary visceral substance, substantia visceralis secundaria, lies somewhat dorsal to the central intermediate (gray) substance.

3. side post contains the following cores:

1. thoracic column [thoracic nucleus], ​​columna thoracica, is limited by segments Th I -L II and is located on the medial side of the base of the posterior horn, so some authors attribute it to the nuclei of the latter;
2. central intermediate (gray) substance, substantia (grisea) intermedia centralis, is localized in segments Th I –L III, in central department lateral horn, almost reaching the central canal;
3. lateral intermediate (gray) substance, substantia (grisea) intermedialateralis, lies lateral to the previous nucleus, occupying the protrusion of the lateral horn and spreading to segments Th I–L III;
4. sacral parasympathetic nuclei,nuclei parasympathetic sacrales, occupy segments S II –S IV, located somewhat ahead of the previous one.

In the lower cervical and upper thoracic segments of the spinal cord, in the angle between the lateral horn and the lateral edge of the posterior horn, gray matter in the form of processes penetrates into the white matter, forming a reticular structure - reticular formation, formatio reticularis, spinal cord, in the loops of which the white matter is located.

The location of the anterior and posterior horns corresponds to the anterior and posterolateral grooves of the spinal cord. This correspondence between the horns and the sulci determines the topography of the white matter in transverse sections: its division into anterior, posterior, and lateral cords of the white matter.

Nervous system

The nervous system unites parts of the body (integration), ensures the regulation of various processes, coordination of the work of organs and the interaction of the body with the external environment. It perceives diverse information coming from the external environment and internal organs, processes it and generates signals that determine adequate responses.

Anatomically, the nervous system is divided into central (brain and spinal cord) and peripheral (peripheral nerve nodes, nerve trunks and nerve endings). From a physiological point of view, a distinction is made between the autonomic (vegetative) nervous system, which innervates the internal organs, glands, blood vessels, and the somatic (cerebrospinal), which regulates the activity of the rest of the body (skeletal muscle tissue).

Development of the nervous system

The development of the nervous system comes from the neuroectoderm (neural plate), which forms the neural tube, neural crest, and neurogenic placodes. The spinal cord and brain develop from the neural tube, in which the following layers differentiate:

Inner limiting membrane;

ependymal layer;

Raincoat layer;

edge veil;

Outer boundary membrane.

source of all cells The CNS are the matrix (ventricular) cells of the inner layer. They are concentrated near the inner boundary membrane, actively multiply and move. Cells that have completed proliferation - neuroblasts, as well as glioblasts capable of proliferation, are evicted into the mantle layer. Part of the ventricular cells remains in situ, in the future it is the future ependyma.

Neuroblasts give rise to all CNS neurons; after migration, they lose their ability to proliferate. Glioblasts become precursors of macroglia, they are capable of proliferation.

The rigidity of the organization of the brain is determined by two factors: targeted migration of cells and directed growth of processes. The mechanism of directed movements is due to chemotropism, which is carried out along a pre-marked path. At certain stages of ontogeny, programmed cell death occurs. The volume of the subpopulation of dying neurons is estimated in the range of 25-75%. At the same time, the cellular elements of the ganglionic plate form spinal and autonomic nodes.

Spinal cord

The spinal cord is a section of the central nervous system, which is located in the spinal canal and has the form of a rounded cord, slightly flattened in the dorsal-abdominal direction. In the center of the spinal cord runs the central spinal canal, lined with ependymal glia.

The spinal cord, like the brain, is covered by three meninges:

Inner - pia mater with vessels and nerves in its loose connective tissue. It is directly adjacent to the spinal cord.

This is followed by a thin layer of loose connective tissue - the arachnoid. Between these membranes there is a subarachnoid (subarachnoid) space with thin connective tissue fibers connecting the two membranes. This space with cerebrospinal fluid communicates with the ventricles of the brain.

The outer shell is a dura mater, consisting of dense connective tissue, fused with the periosteum in the cranial cavity. In the spinal cord there is an epidural space between the periosteum of the vertebrae and the dura mater, filled with loose fibrous connective tissue, which gives some mobility to the membrane. Between the dura mater and the arachnoid there is a subdural space with a small amount of fluid. The subdural and subarachnoid spaces are internally covered with a layer of squamous glial cells.

The spinal cord consists of two symmetrical halves, delimited from each other in front - by the median fissure, from behind - by the median sulcus.

On a transverse section, gray and white matter are easily distinguished.

Gray matter located in the central part, surrounded by white matter.

The gray matter in cross section has the shape of butterfly wings. The protrusions of the gray matter are called horns: there are anterior, posterior and lateral horns. There is an intermediate zone between the anterior and posterior horns. The horns are actually pillars that run along the spinal cord.

The gray matter of both symmetrical halves is connected to each other in the region of the spinal canal by a central gray commissure (formed by commissures).

Gray matter is formed by the bodies of nerve cells, their dendrites and partially axons, as well as glial cells.

Nerve cells are located in the gray matter in the form of not always sharply demarcated clusters - nuclei. Based on the location of neurons, the nature of their connections and the function of B. Rexedom, 10 plates were isolated in the gray matter of the spinal cord. The topography of the nuclei corresponds to the topography of the plates, although they do not always coincide.

depending from axon topography spinal cord neurons are divided as follows:

♦ Internal - neurons whose axons terminate within the gray matter of a given segment of the spinal cord.

♦ Beam - their axons form bundles of fibers in the white matter of the spinal cord.

♦ Radicular - their axons exit from the spinal cord as part of the anterior roots.

In the posterior horns there are: spongy layer, gelatinous substance, posterior horn proper nucleus and thoracic nucleus.

spongy layer stretches continuously along the spinal cord, forming the dorsal lobe of the posterior horn, which corresponds to plate I, is characterized by a glial skeleton, which contains a large number of small intercalary neurons. These neurons respond to pain and temperature stimuli and give off fibers to the spinothalamic tract on the opposite side. Among these neurons there are cells containing substance P and enkephalin.

In gelatinous substance, or Roland gelatinous substance(plate II, III), glial elements predominate. Nerve cells here are small, there are few of them. They are approached by axons coming from the posterior funiculus, and fibers of pain and tactile sensitivity. The axons of the neurons of this layer either end within this segment of the spinal cord (they enter the marginal Lissauer belt, which forms transverse and longitudinal connections on the surface of the gelatinous substance), or go into their own bundles or to the thalamus, cerebellum, and lower olives. The neurons of this layer produce enkephalin, an opioid-type peptide that inhibits pain effects.

The main significance of the gelatinous substance is the implementation of an inhibitory effect on the functions of the spinal cord by controlling the sensory information entering it: skin, partially visceral and proprioceptive.

Own core consists of intercalary neurons that receive afferent impulses from the spinal nodes and descending brain fibers. Their axons pass through the anterior white commissure to the opposite side and ascend to the thalamus, just as the gelatinous substance is responsible for exteroceptive sensitivity.

The thoracic nucleus of the posterior horn (Clark's nucleus) is located in the VII plates. It is formed by neurons to which thick myelinated collaterals of sensory neurons approach, delivering proprioceptive sensory input from the joints, tendons, and muscles. The axons of Clark's nucleus cells form the posterior spinal cerebellar tract.

In the intermediate zone of the VI and partially VII plates, the outer and inner basilar nuclei are located. They process the bulk of the information coming from the brain and transmit it to motor neurons. On the cells of the outer nucleus, thick, fast-conducting axons are interrupted, originating from the largest and giant pyramids of the motor zone of the cerebral cortex. Thin slowly conducting fibers are projected onto the neurons of the inner nucleus. In humans, about 90% of the fibers of the cortico-spinal tract end on the neurons of the basilar nuclei.

Lateral horns contain: medial and lateral nuclei.

The lateral nucleus (Th I - L II) contains the neurons of the autonomic reflex arc - the center of the sympathetic department. The axons of the pseudounipolar spinal ganglion enter the sympathetic nucleus, carrying visceral sensitivity. The second group of axons comes from the medial nucleus of the lateral horn. The axons of the neurons of the lateral nucleus give rise to preganglionic fibers emerging from the spinal cord through the anterior roots.

The medial nucleus (S II - Co III) is located in the intermediate zone, where there are no lateral horns - it receives impulses from sensitive neurons of the autonomic reflex arc.

In addition, the Onufrovich nucleus is located in the lateral horns of the sacral segments (S2 - S4) of the spinal cord. It contains neurons of the parasympathetic division of the autonomic nervous system, which are involved in the innervation of the pelvic organs.

Plate VII contains the Renshaw interoneurons necessary for the implementation of the motor function. They receive an excitatory impulse from the axon collagens of motor neurons and inhibit their function. It has importance for the coordinated work of motor neurons and the muscles innervated by them for alternate flexion and extension of the limbs.

The interstitial nucleus of Cajal is localized in the VIII plate. Its interoneurons switch information from afferent neurons to motor neurons. The axons of the neurons of this nucleus are part of their own bundles and form collateral connections on several segments.

The periependymal gray matter corresponds to plate X, is located throughout the spinal cord and is formed by intercalary neurons of the autonomic nervous system.

The anterior horns contain multipolar motor neurons (lamina IX), which are the only executive cells in the spinal cord that send information to the skeletal muscles. They are combined into nuclei, each of which usually stretches for several segments. Ends on motor neurons:

♦ Collaterals of axons of pseudo-unipolar cells, forming two-neuronal reflex arcs with them.

♦ Axons of intercalary neurons, whose bodies lie in the posterior horns of the spinal cord.

♦ Axons of Renshaw cells forming inhibitory axosomatic synapses. The bodies of these small cells are located in the middle of the anterior horn and are innervated by the collaterals of the axons of motor neurons.

♦ Fibers of the descending pathways of the pyramidal and extrapyramidal systems, carrying impulses from the cerebral cortex and nuclei of the brain stem.

According to classical concepts, motor neurons in the spinal cord are distributed over 5 motor nuclei.

Medial - anterior and posterior - are present throughout the spinal cord, innervate the muscles of the body.

Lateral - anterior and posterior - are localized in the cervical and lumbar thickenings, innervate the flexors and extensors of the limbs.

The central nucleus - is located in the lumbar and cervical regions, innervates the muscles of the limb belts.

white matter- is divided by the anterior and posterior roots into symmetrical ventral, lateral and dorsal cords. It consists of longitudinally running nerve fibers (mainly myelinated), forming descending and ascending pathways (tracts), and astrocytes. Each tract is characterized by the predominance of fibers formed by neurons of the same type.

The pathways include 2 groups: propriospinal and supraspinal.

propriospinal pathways- own apparatus of the spinal cord, formed by axons of intercalary neurons, which communicate between the segments of the spinal cord. These paths pass mainly on the border of white and gray matter as part of the lateral and ventral cords.

supraspinal pathways- provide a connection between the spinal cord and the brain and include ascending and descending spinal-cerebral pathways.

Pain, temperature, deep and tactile sensitivity are carried out along the ascending paths. These are the dorsal and thalamic pathway, the dorsal and ventral spinal cerebellar pathways, the tender and sphenoid bundles.

The cerebrospinal tracts provide the transmission of impulses to the brain. Some of them (there are 20 in total) are formed by the axons of the cells of the spinal nodes, while the majority are represented by the axons of various intercalary neurons, the bodies of which are located on the same or on the opposite side of the spinal cord.

Cerebrospinal tracts include pyramidal and extra-rapyramidal systems.

The pyramidal system is formed by long axons of the pyramidal cells of the cerebral cortex, which at the level of the medulla oblongata mostly pass to the opposite side and form the lateral and ventral corticospinal tracts. The pyramidal system controls the precise voluntary movements of the skeletal muscles, especially the limbs.

The extrapyramidal system is formed by neurons, the bodies of which lie in the nuclei of the middle and medulla oblongata and the bridge, and the axons end on motor neurons and intercalary neurons. This system controls mainly the contraction of the tonic muscles responsible for maintaining the posture and balance of the body.

The extrapyramidal descending pathways are represented by the rubrospinal pathway, originating from the red nucleus and conducting impulses from the nuclei of the cerebellum, as well as the tecto-spinal pathway, starting from the tegmentum and conducting impulses from the visual and auditory pathways, as well as the vestibulo-spinal pathway, originating from the nuclei of the vestibular nerve and carrying impulses of a static nature.

It is difficult to underestimate the function and role of the human brain. A person is characterized by: coherent speech, the ability to fantasize, the ability to analyze, remember facts, distinguish melodies, pass on experience to generations, and much more. The human body is a complex, perfectly adjusted structure that provides physical activity, vital activity, basic mental functions: thinking, perception, memory, speech, etc.

The obvious connection between the brain and reflex-sensory activity encourages scientists to continue studying the brain and its functions, where one of the topical issues remains the role of gray matter in human life and in the formation of human intelligence.

General information about gray matter

The central nervous system (CNS) of a person is one of the most complex structures of the body, it has an extremely responsible role - it ensures the functional integrity of the body and its relationship with the outside world. The CNS consists of the brain and spinal cord and their protective membranes, which, in turn, consist of gray and white matter.

The gray substance (lat. substantia grisea) is responsible for most of the functions of the higher nervous activity of a person. Thanks to her, a person perceives external environment, hears, sees, speaks and most importantly, a person can express an attitude, show sympathy or negative emotions, show types of human behavior, empathy, etc.

The substance consists of approximately 86 billion neurons, of course, this number is extremely approximate, since modern medicine does not yet have the ability to calculate the exact number of nerve cells.

The white substance or (lat. Substantia alba) serves mainly for signal transmission and ensures the interconnection of both hemispheres, and also transfers information from the cerebral cortex to the nervous system.

Clusters of neurons form the gray matter. Each nucleus has a corresponding responsibility and function: visual, auditory functions, blood circulation, respiration, movement, urination, etc.

Consists of nuclei of gray matter, which form the corresponding centers. Substantia grisea is one of the main components of the spinal cord, and its nuclei are located in the cerebellar cortex and in the internal structures of the large brain (medulla oblongata, thalamus, hypothalamus, etc.).

Gray matter appears as a shell of the brain, under which there is white matter, however, in the spinal cord, substantia grisea is located in the inner part of the spinal system, enveloping a narrow central canal filled with cerebrospinal fluid, the substance forms the contour of the letter H, and it is already covered with white matter.

The structure of the gray matter

Substantia grisea is a perfectly arranged structure, which includes:

• neurons;
• dendrites;
• unmyelinated axons;
• glial cells;
• thin capillaries.

The latter stain the bark in Brown color and contrary to popular belief, the substance is not gray, but gray-brown. Numerous labyrinthine depressions and bulges form convolutions - known as cerebral convolutions. The main function of the gray matter is to provide communication human body with the outside world, as well as the regulation of reflexes and the provision of higher mental functions.

And if substantia grisea consists of neurons, then substantia alba appears in the form of axons covered with myelin (processes of neurons), which act as conductors and serve to transmit signals and provide communication between the hemispheres and nerve centers. The myelin sheath gives the characteristic White color substance.

The gray substance in the spinal structure resembles in structure the contours of the letter H or the wings of a butterfly. Depending on the location and function, gray pillars are divided into: rear, front and side. From the lateral parts of the dorsal region, in turn, are divided into:

• Posterior - consist of intermediate nerve cells. They receive signals from the ganglia.
• Anterior - consist of motor neurons. The main function is to provide muscle tone.
• Lateral - consist of sensory and visceral neurons. Responsible for motor functions.

Functions of gray matter

The work of the central nervous system provides a large number of connections in the body that perform two main functions: control of muscle activity (motor reflex) and provision of sensory perception (sensory reflexes) and higher mental functions: memory, speech, emotions.

The functions of substantia grisea are determined by its location, for example:

1. In the cerebral cortex, the substance is responsible for the connection of the body with the outside world, and also carries information and regulates the activity of internal organs, is responsible for providing higher nervous activity, thanks to which a person is able to think, remember, perceive, etc.
2. In the medulla oblongata, the substance nuclei regulate motor processes, balance, provide coordination of movements, and also regulate metabolism, respiratory processes and blood supply.
3. In the cerebellar cortex, gray nuclei are responsible for the coordination of movements and orientation in space.
4. IN diencephalon nuclei are responsible for controlling the activity of internal organs, regulate reflexes and body temperature.
5. In the telencephalon, the nuclei provide motor, reflex control and regulation of higher mental functions: coherent speech, vision, smell, taste, hearing, touch.

The spinal cord is a complex structure that has the following functions: reflex, motor, sensory and conduction. The first three functions are assigned to gray matter, and the third to white matter.

1. Reflex function - regulation of unconditioned reflexes: sucking reflex, knee reflex, instant reaction to painful stimuli, etc.
2. Motor function - control of muscle reflexes associated with the motor system. Corresponding cells of the spinal cord send signals to a specific muscle group, prompting one or another action, thanks to which we can purposefully turn our heads, move our necks, raise and lower our arms, and walk.
3. Sensory function - the transmission of an impulse coming from the afferent fibers of the body to the parts of the brain, from where the command containing the reaction to the stimulus comes from.
4. Conductor function - ensuring the passage of an impulse to the brain, and from there - the passage of an action command going to the corresponding organ. Regulated by white substance.

The gray substance ensures the normal life of a person, his interaction with the outside world, types of human activity, is the basis of cognitive and sensory perception, as well as the basis of motor, reflex, regulatory and all mental functions.

How gray matter affects some of the abilities of people

The gray tissue of the brain, by regulating the processing of signals from the outside and generating effector impulses, is not only responsible for the operation of the entire human nervous system, but also affects its abilities: mental, cognitive, physical, etc.

Various experiments by scientists have shown that a person's abilities depend on the volume of gray matter, while a change in the amount of white did not show tangible changes.

The experiments of British scientists have shown that the thinner the cerebral cortex, therefore, the smaller the volume of gray matter, the worse a person copes with solving logical problems, the less different abilities he has, and also with a low volume of substance, the subjects often had problems with reaction speed , speech dysfunctions, memory problems and poor intellectual abilities.

At the same time, studies have shown that foreign languages, memorization of poems, scientific or artistic works and music lessons affect the increase in the cerebral cortex. The longer and more intense the process of studying, the greater the volume of gray matter becomes, therefore, the more abilities, including mental ones, a person manifests.

The decrease in the amount of gray matter is affected by:

• a person's way of life - a sedentary, inert, inactive, from a physical and mental point of view, a way of life;
• abuse bad habits- alcohol, drug addiction and smoking reduce the volume of gray matter.

For example: in those suffering from alcoholism, there is a significant decrease in the amount of brain tissue, which affects the behavior and mental functions: incoherent speech, problems with memory and perception, inhibition of thought processes.

Gray matter and intelligence

Currently, the scientific world is divided into two fronts:

1. The first argue that the mass and volume of the brain affect mental capacity person.
2. The latter are sure that the volume of gray matter plays a secondary role.

At different times, scientists from different countries have tried to determine the relationship between substantia grisea and intelligence, however, it is necessary to take into account the fact that the study of the brain, due to the structure and location of the organ, is a rather difficult process, and much about the functions of the brain remains unexplored and unknown. to a person.

We can say with confidence that a weak relationship between mental, analytical abilities and brain size was discovered by scientists a couple of decades ago, however, other scientists in the course of experiments proved that the level of intelligence does not depend on the weight or size of the brain as a whole, but on the size of the anterior parts of the brain.

Modern scientists suggest that human IQ is a complex and multifaceted concept, and in the process of the formation of human intelligence, various structures are involved, where the speed of transmission of a nerve impulse or the number of connections between nerve cells plays an important role.

Another group of scientists found that people with high intelligence have more gray matter. However, this only led to another hypothesis that a certain percentage of the volume of substantia grisea is associated with intellectual abilities person.

There are many hypotheses related to the question, but to date, the scientific world has not yet given an experimentally proven, unambiguous answer.

One thing is for sure - the additional volume of gray matter allows you to more productively and quickly process information, damage and damage to the gray matter, depending on the location, leads to muscle, sensory and neurological disorders.

In this article, we will talk about gray matter, what it is, where it is located and what functions it performs.

What is it and what does it consist of

The human brain is made up of two types nervous tissue- gray matter and white. Gray matter The nervous system is an accumulation of nerve cells responsible for most of the functions of the higher nervous activity of a person. Function white cells transmission of electrical impulses to different parts of the brain. The thickness of the gray tissue of the brain reaches about half a centimeter in the population. Topographically, the gray matter is the shell of the brain, under it is a cluster of long processes (axons), that is, the substance is white.

The gray matter is formed by an accumulation of the smallest capillaries, glial tissue and short processes - dendrites. In addition, the composition of the gray matter includes non-myelinated long processes - axons. Unlike gray matter, which does not have myelinated fibers, white matter is called white because it is given color by the sheaths of axons, which consist of myelin.

Gray matter nuclei are histological structures, a concentric accumulation of nerve cell bodies that perform a specific function in the nervous system. Anatomically, two subspecies of nuclei are distinguished: nuclei in the topic of the central nervous system and those in the structure of the peripheral nervous system. Each nucleus is the regulator of a certain function of the body, whether it is the act of urination or the center of the heartbeat.

There is a partly erroneous opinion that the gray matter consists of long processes of neurons. Specialized processes, equipped with a fast conductor myelin, are in the structure of the white matter of the brain and spinal cord, while only dendrites and unmyelinated long fibers are present in the gray substance. The bottom line is that myelinated long axons are not needed in the cortex, because the gray matter of the brain consists of clusters of adjacent bodies of neurons, and information from cells to cells is transmitted by short processes (dendro-dendritic synapses), because the main task of long processes is the transmission of an electrical impulse from one center to another. There, the function of transmitting and receiving information is served by axo-axonal, or axo-dendritic synapses.
Gray matter is not different in all parts of the brain. It is the same in different departments. Therefore, the gray matter of the telencephalon includes the set of elements that is inherent in other brain structures.

Where is it located in the brain

The question of where the gray matter of the brain is located is answered by several basic theoretical medical sciences - normal and topographic anatomy and histology. Other sciences of the brain study its function, rather than its location and structure.
Gray matter is the cerebral cortex. On average, the layer of dark tissue is about 3-4 mm (from 1.5 to 5 mm). It has the most pronounced thickness in the region of the anterior central gyrus. Due to the location of the set, the area of ​​\u200b\u200bthe gray matter increases significantly. In addition to the brain, a layer of gray matter is located inside the spinal cord.

In the cerebellum, the bulk of the gray matter is located by analogy with the brain: gray matter is the cortex of the cerebellum and is located on the surface of the structure itself, being its shell when it is located inside the cerebellum. In addition, the cortex of the coordinating center of the human body consists of three layers - the molecular ball, pear-shaped neurons and the granular layer.

The bulb of the brain also has a gray substance, like other parts of the brain. is one of the first evolutionarily formed structures of the brain. This part is located at the level of the occipital foramen, and passes into the spinal cord. The gray matter of the medulla oblongata forms some nuclei and nerve centers, among which are the nuclei of the cranial nerves and the mesh formation. The nuclei formed by dark tissue include the hypoglossal, accessory, vagus, and glossopharyngeal nerves. It should be noted that all these centers are neither the lowest nor the highest centers of regulation - they occupy an intermediate position in the hierarchy of the regulatory systems of the brain.

The structure located above the oblong is called the bridge. At its junction with a neighboring structure, several nerves exit, including the vestibulocochlear nerve. The gray matter of the bridge forms its own centers of a mixed nature: the nucleus of the trigeminal nerve, the facial and abducens nerve. Such nerves are responsible for the innervation of the facial (facial) muscles, the scalp (its scalp), some eye muscles and certain parts of the tongue. In addition to such functions, the task of the Varolian bridge is to maintain the correct posture and partially preserve the location of the body in space.
The gray matter of the midbrain is represented by red nuclei and substantia nigra. These structures are collectors of conscious and unconscious movements: the nuclei have rich connections with the cerebellum. In general, these structures are included in the complex of the striatal system of the brain.

The cortex, consisting of gray matter, covers many structures of the brain, including:

The conclusion suggests itself that any structure that has a specific regulatory function is covered with an accumulation of gray matter.

What is the role of gray matter

Millions of years of evolution, natural selection and the origin of species have given the human being a unique structure - a relatively thick cerebral cortex. It is known that the structure of gray matter is properly developed only in representatives of the human species. Unlike lower and even higher mammals, the gray substance endowed a person with the opportunity to have a unique property of matter, the object of study of all neurosciences and philosophy - consciousness and self-awareness, the result of which is abstract thinking, developed memory, inner speech and many other specific attributes of the higher nervous activity of a reasonable person.

It must be remembered that gray matter is an accumulation of nerve cells, namely neurons. Speaking about the function of gray matter, we are talking about the function of all clusters of neurons with short processes. So, the functions of gray matter are diverse:

• Physiological tasks: generation, transmission, receipt and processing of electrical signals.
• Neurophysiological: perception, speech, thinking, memory, vision, emotions, attention.
• Psychological: personality formation, worldview, motivation, will.

For a long time, scientists have wondered what the gray matter of the brain is responsible for. As early as the 18th century, Franz Gall drew attention to the dark brain substance. The scientist for the first time managed to localize some mental functions on the cortex. Subsequent research was carried out by the type of removal of a section of the cortex and observation of what brain function had fallen out. A serious impetus to further research was the study of the work of the cortex by Academician Pavlov, who studied the basic reflexes and the principles of fixing the conditioned reflex. Parallel to him, his French colleagues found a speech center in the cortex - the lower part of the frontal gyrus. modern science, although he knows many properties of the cerebral cortex, claims that the percentage of knowledge and it is no more than one thousandth.

One blind spot in the empirical evidence about the knowledge of the brain and its formation is the question of what is the heterotopia of the gray matter of the brain. In particular, this question is often raised in the field of clinical medicine, where treatment is only symptomatic, that is, only symptoms are removed. As you know, heterotopia is a defective accumulation of neurons that have stopped in certain place and did not reach their histological place. So, there is a cause of pathology - there is also an etiological treatment. A variant of the manifestation of heterotopia is childhood epilepsy.

difference from white matter

This section is intended to calibrate concepts and answer the question of what is the gray and white matter of the brain.

Gray matter

• Created by the nuclei of nerve cells and its counterparts.
• It is located mainly in the central parts of the nervous system.
• It makes up no more than 40% of the total mass of the brain.
• Consumes about 3-5 ml of oxygen per minute.
• The structure that carries the regulatory function.

white matter

• Formed by long myelinated axons.
• It is located mainly in the peripheral nervous system.
• It makes up more than 60% of the weight of the human brain.
• Consumes less than 1 ml of oxygen per minute.
• Responsible for conducting nerve impulses through the nervous system

It should be remembered that in contrast to the structure of the cerebral cortex, where the gray matter is a shell and covers the white substance, in the spinal cord the gray matter is surrounded by the white matter of the brain.

Research

Modern science has many methods for studying the activity of the gray substance of the brain. These include:

• Registration of impulse activity of nerve cells. Registration is carried out with the help of microelectrodes, which, being close to the cells, touch them and seem to stick into them. Thus, the electrical potential of the neuron, its voltage and amplitude are investigated. Qualitative changes can characterize the decay of gray matter.
• Electroencephalography. This method allows you to explore and register minimal fluctuations in electrical potentials directly from the surface of the skull. With the help of EEG, various rhythms of brain activity are studied, and is the key to the study. biological rhythms especially sleep. Also, electroencephalography painlessly allows you to see a change in the gray matter in a child. The technique is not invasive, unlike the previous one.
• Magnetoencephalography. MEG makes it possible to study the synchronous activity of gray matter fields. After all, part of it is desynchronization that is the cause of many pathological conditions of the activity of the central nervous system.
• Positron emission tomography. This computer method makes it possible to visualize the functional activity of the cerebral cortex. PET allows you to "see" a spatial image of the structure of the brain.
• Nuclear magnetic resonance introscopy. With this method, you can see the gray matter in the brain, since NMRI gives a picture of the structure of tissues.

Introduction

The nervous system (systema nervosum) is divided into central and peripheral sections. The central nervous system (CNS) is represented by the brain (encephalon) and spinal (medulla spinalis) brain. The central nervous system ensures the interconnection of all parts of the nervous system and their coordinated work.

Spinal cord

The spinal cord is located in the spinal canal and is a cylindrical cord, flattened from front to back, with an average length of 45 cm in men and 41-42 cm in women.

The spinal cord performs two important functions: reflex and conduction. The entire nervous system functions according to reflex principles. Participating in the perception of sensory information, the spinal cord regulates segmental reflex activity.

The spinal cord is protected bone tissue spine and surrounded by membranes. The thickness of the spinal cord is not the same and 2 thickenings stand out along its length: cervical (intemescentia cervicalis) and lumbar (intumescentia lumbalis)

Following the lumbar thickening, the brain comes to naught, forming a cerebral cone (conus medullaris). It is located at the level of the second lumbar vertebra. And then the final thread stretches, which ends at the level of the second coccygeal vertebra. And attached to it. Thickening develops in parallel with the growth and formation of the limbs. From the cervical thickening nerves depart to the arms, and from the lumbar to the legs. Thickenings are accumulations of nerve cells.

The spinal cord is much shorter than the spine, as it matures earlier and finishes its growth earlier.

Rice. The structure of the spinal cord: 1 - Pia mater spinalis (soft shell); 2 - Sulcus medianus posterior (posterior median sulcus); 3 - Sulcus intermedius posterior (intermediate posterior groove); 4 - Radix dorsalis (back root); 5 - Cornu dorsale (posterior horn); 6 - Cornu laterale (lateral horn); 7 - Cornu ventrale (front horn); 8 - Radix ventralis (anterior root); 9 - A. spinalis anterior (anterior spinal artery); 10 - Fissura mediana anterior (anterior median fissure)

Gray and white matter of the spinal cord

The substance of the spinal cord is heterogeneous. Separate gray and white matter.

Gray matter - substantia grisea

White matter - substantia alba

On the transverse section of the spinal cord, the zone of gray matter surrounding the central canal is clearly visible in the form of a butterfly, or in the form of the letter H. This zone is formed by the bodies and dendrites of neurons. On the periphery there is a white matter consisting of axons, the fat-like myelin sheaths of which determine the characteristic color of this zone.

Gray matter of the spinal cord

Gray matter is formed by a huge number of neurons grouped into nuclei. It distinguishes three types of multipolar neurons:

1. Radicular cells - large motor neurons (motor neurons) and efferent motor neurons of the autonomic nervous system. They are involved in the formation of the anterior roots (Radix ventralis) of the spinal nerves. They go to the periphery and innervate the skeletal muscles.

2. Beam neurons - their axons form most of the ascending pathways going from the spinal cord to the brain (white matter bundles), as well as their own bundles of the spinal cord, connecting various segments of the spinal cord. These are switch neurons.

3. Internal cells - their numerous processes do not go beyond the gray matter, forming synapses in it with other neurons of the spinal cord.

Gray matter, substantia grisea, is embedded inside the spinal cord and surrounded on all sides by white matter. Gray matter forms two vertical columns placed in the right and left halves of the spinal cord. In the middle of it is laid a narrow central canal, canalis centralis, of the spinal cord, which runs the entire length of the latter and contains cerebrospinal fluid. The gray matter surrounding the central canal is called the intermediate, substantia intermedia centralis. Each column of gray matter has 2 columns: anterior, coliimna anterior, and posterior, coliimna posterior.

On transverse sections of the spinal cord, these columns look like horns: anterior, expanded, cornu anterius, and posterior, pointed, cornu posterius. That's why general form gray matter on a white background resembles the letter H.

Throughout the spinal cord, gray matter is subdivided into paired anterior and posterior columns (columna grisea anterior et posterior). In the interval from the I thoracic to the I-II lumbar vertebrae, lateral columns (columna lateralis) are added to them.

On a transverse section in the gray matter, three horns are distinguished: cornu posterior, cornu lateralis and cornu anterior (anterior, lateral and posterior horns).

rear horns

In the posterior horns there are intercalary neurons, which are either part of reflex arcs that close at the level of the segment, or form ascending pathways that conduct sensory information to the brain. Closest to the surface of the dorsal horn are neurons that switch and process pain signals. Slightly more ventral are cells whose axons conduct impulses from skin receptors. Deepest of all in the posterior horns are intercalary neurons that receive information from muscle receptors.

The structure of the posterior horn

Roland's gelatinous substance consists of neuroglia. It contains small neurons of stellate and triangular shape. Their axons serve intrasegmental connections. Roland's substance is especially pronounced in the upper cervical and lumbar segments, and in the thoracic segment it decreases somewhat.

The spongy zone is also formed by glial tissue and contains small multipolar neurons.

The Lissauer marginal zone is well defined in the lumbosacral region and mainly consists of the central processes of spinal ganglion cells, which enter the spinal cord as part of the dorsal roots (radix dorsalis). There are also small spindle-shaped neurons. Their dendrites branch in the spongy zone, and the axons enter the lateral funiculus of the white matter and participate in the formation of their own bundles of the spinal cord.

The head of the posterior horn contains its own nucleus. Its head forms the spinal thalamic tract and the anterior spinal tract. At the base of the posterior horn, in its medial part, is Clark's column. This is a large thoracic nucleus. Clark's column extends from the 1st thoracic to the 2nd lumbar segment of the vertebrae. From it depart the fibers that form the posterior spinal tract. Side part the base of the posterior horn is occupied by neurons that are involved in the formation of intra- and intersegmental connections of the spinal cord.

The neurons of the spongy zone and the gelatinous substance, as well as intercalary cells in other parts of the posterior columns close the reflex connections between the sensory cells of the spinal ganglia and the motor cells of the anterior horns with switching in their own nucleus.

Lateral horns

Lateral horns are clearly expressed only in the case of the sympathetic nervous system. The axons of the cells of the lateral horns exit the spinal cord as part of the anterior roots. In the sacral region, the lateral horns no longer stand out, and the vegetative cells located there lie at the base of the anterior horn.

The lateral horns protrude only in the thoracic-lumbar region of the spinal cord and contain sympathetic neurons. Here lie the medial and lateral intermediate nuclei.

Parasympathetic neurons are located below, reaching the V sacral segment. They also form an intermediate core. Its fibers go to the pelvic internal organs.

Anterior horns

In the ventral horns of the gray matter are motonerons. They are located not randomly, but in accordance with the innervated muscles. Thus, contractions of the trunk muscles are triggered by motoneurons located more ventrally, and the muscles of the limbs are triggered by more dorsally localized ones. The anterior horns are most developed in the cervical and sacral regions of the spinal cord, where motor neurons innervating the limbs are located. The largest motor nerve cells belong to the group of alpha motor neurons. In addition to them, relatively small gamma motor neurons are also present in the ventral horns. Their function is not associated with the control of skeletal muscle contractions (as in the case of alpha neurons), but with the work of muscle receptors.

Short strands of gray matter pass between the lateral and posterior horns of the white matter, making up the mesh formation of the spinal cord.

The right and left columns of the gray matter of the spinal cord are connected by spikes - commissures (commissura grissa posterior and commissura grissa anterior), separated by the central canal of the spinal cord.

The gray matter of the spinal cord directly passes into the gray matter of the brain stem, and part of it spreads along the rhomboid fossa and the walls of the aqueduct, and partly breaks into separate nuclei of cranial nerves or nuclei of bundles of pathways.

White matter of the spinal cord

The white matter of the spinal cord performs a conductive function, transmits nerve impulses. It includes three systems of pathways - ascending, descending, and own pathways of the spinal cord.

The ascending pathways of the spinal cord transmit sensory information from the trunk and limbs (pain, skin, muscle, visceral) to the brain. Descending pathways carry control commands (somatic and autonomic) from the brain to the spinal cord. Own paths connect neurons above and below the spinal cord segments. This is necessary for the coordinated work of the gray matter zones that control different muscles with simultaneous contraction (for example, the muscles of the arms and legs while walking and running). In addition, in the case of many large muscles, the motor neurons innervating them are stretched in the rostro-caudal direction into several segments. The connection between them is also provided by the spinal cord's own pathways.

The white matter of the spinal cord consists of nerve processes that make up three systems of nerve fibers:

1. Short bundles of associative fibers connecting parts of the spinal cord at different levels (afferent and intercalary neurons)

2. Long centripetal (sensitive, afferent) neurons.

3. Long centrifugal (motor, efferent) neurons.

The first system (short fibers) refers to the own apparatus of the spinal cord, and the other two make up the conductor apparatus of bilateral connections with the brain.

The distribution of white fibers in the white matter is ordered. Having the same origin, original function, nerve fibers are collected in bundles, forming funiculus - posterior, middle and anterior.

In the posterior cords, ascending paths pass, in the anterior - mainly descending, in the lateral - both those and others. The intrinsic pathways of the spinal cord are directly adjacent to the gray matter in the region of both the posterior, anterior and lateral cords.

A cross section of different levels of the spinal cord shows that in the upper segments there is much more white matter than gray matter; in the lower segments - on the contrary. This is explained by the fact that in the thoracic and, especially, cervical regions, almost all axons connecting the spinal cord with the brain (both ascending and descending) are present in the white matter. The fibers that have reached the lower sections connect only the lumbar, sacral and coccygeal segments of the spinal cord with the brain. Consequently, there are significantly fewer of them.