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 the accompanying connective tissue.

In the gray matter, two lateral parts are distinguished, located in both halves of the spinal cord, and the 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 on a horizontal section has a different size and shape: in the region of the cervical and lumbar thickenings - oval, and in the chest - round with a diameter of up to 0.1 mm. In adults, the canal cavity can be overgrown in some areas. 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 1 mm on average; this section of the central channel was named end 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) substance surrounding the central channel 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. Another part lies behind the canal. Posterior to 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 more thickened anterior, narrower posterior 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 cervical segments and in the upper thoracic segments of the spinal cord.

The protrusions throughout the spinal cord form gray pillars, columnae griseae... Each of them on a cross section of the spinal cord is named horns, cornu(see fig.,). Distinguish front pillar, columna ventralis, in the cross section - front horn, cornu ventrale, back post, columna dorsalis (rear horn, cornu dorsale)and lateral pillar, columna lateralis (lateral horn, cornu laterale).

The anterior horn is much wider, but shorter than the posterior 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 hind horn, one can discern the top of the rear horn, apex cornus dorsalis, - the narrowest part of the dorsal part of the posterior horn, surrounding the head of the posterior horn, caputcornusdorsaliswhich goes into neck of the posterior horn, cervix cornus dorsalis, and that, in turn, into the widest part of the rear 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 - nuclei, or centers, of the spinal cord, which have their own constant topography (Fig. 883).

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

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

2.In back post sensitive cores lie:

1. gelatinous substance, substantia gelatinosa, has, in cross-section, the form of a half moon, bordering the apex of the posterior horn;
2. own nucleus of the posterior horn, nucleus proprius cornus posterioris(BNA), located in its central part, occupies almost the 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 kernels:

1. chest column [chest nucleus], \u200b\u200bcolumna thoracica, is limited by the segments Th I –L II and is located on the medial side of the base of the posterior horn, therefore some authors attribute it to the nuclei of the latter;
2. central intermediate (gray) substance, substantia (grisea) intermedia centralis, localized in the segments Th I –L III, in the central part of the 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 extending to the segments Th I –L III;
4. sacral parasympathetic nuclei,nuclei parasympathici 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, the gray matter in the form of processes penetrates into the white matter, forming a reticular structure - reticular formation, formatio reticularis, the 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 posterior lateral grooves of the spinal cord. This correspondence between the horns and grooves determines the topography of the white matter in cross sections: its division into anterior, posterior, and lateral white matter cords.

Nervous system

The nervous system unites parts of the body (integration), ensures the regulation of various processes, the coordination of the work of organs and the interaction of the body with the external environment. She perceives a variety of 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, an autonomous (autonomic) nervous system is distinguished, which innervates the internal organs, glands, blood vessels, and the somatic (cerebrospinal) nervous system, which regulates the activity of the rest of the body (skeletal muscle tissue).

Development of the nervous system

The development of the nervous system occurs 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 boundary membrane;

Ependymal layer;

Cloak layer;

Edge veil;

Outer pororganic membrane.

The source of all cells The central nervous system is the matrix (ventricular) cells of the inner layer. They are concentrated near the inner boundary membrane, actively multiply and move. Cells that have finished proliferating - neuroblasts, as well as glioblasts capable of proliferation, are moved into the mantle layer. Part of the ventricular cells remains in situ, and later on, this is the future ependyma.

Neuroblasts give rise to all neurons in the central nervous system, after migration they lose their ability to proliferate. Glioblasts become precursors of macroglia, they are capable of proliferation.

The rigidity of brain organization is determined by two factors: targeted cell migration 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 ontogenesis, 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 the spinal and vegetative nodes.

Spinal cord

The spinal cord is a part of the central nervous system that is located in the spinal canal and looks like a round cord, slightly flattened in the dorsal-abdominal direction. In the center of the spinal cord is the central spinal canal lined with ependymal glia.

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

The inner one is the 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 membrane. Between these membranes is the 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 covered from the inside with a layer of flat glial cells.

The spinal cord consists of two symmetrical halves, delimited from each other in front by a median fissure, and in the back by a median groove.

On the cross-section, gray and white substances 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 front, rear and lateral horns. There is an intermediate zone between the anterior and posterior horns. In reality, the horns are 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).

The gray matter is formed by the bodies of nerve cells, their dendrites and partly 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. Rexed in the gray matter of the spinal cord, 10 plates were identified. The topography of the nuclei corresponds to the topography of the plates, although they do not always coincide.

Depending on from axonal topography spinal cord neurons are subdivided as follows:

♦ Internal - neurons whose axons end 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.

♦ Root - their axons leave the ich of the spinal cord as part of the anterior roots.

The rear horns are distinguished: spongy layer, gelatinous substance, own nucleus of the posterior horn and pectoral nucleus.

Spongy layer stretches continuously along the spinal cord, forming the dorsal lobe of the posterior horn, which corresponds to the I plate, is characterized by the glial skeleton, which contains a large number of small intercalary neurons. These neurons respond to pain and temperature stimuli and donate fibers to the spinal thalamic pathway on the opposite side. Among these neurons 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, few of them. They are approached by axons coming from the posterior cord, and fibers of pain and tactile sensitivity. The axons of the neurons of this layer either end within a given segment of the spinal cord (enter the Lissauer's marginal 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 in this layer produce enkephalin, an opioid-type peptide that inhibits pain effects.

The main value 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 fibers of the brain. 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 there are thick myelinated collaterals of sensory neurons, delivering proprioceptive sensory sensitivity from joints, tendons and muscles. The axons of the Clarke nucleus cells form the posterior spinal cord.

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

The lateral horns contain: the medial and lateral nuclei.

The lateral nucleus (Th I - L II) contains the neurons of the autonomic reflex arc - the center sympathetic division... The sympathetic nucleus includes the axons of the pseudo-unipolar spinal ganglion, which carry visceral sensitivity. The second group of axons comes from the medial nucleus of the lateral horn. Axons of neurons in the lateral nucleus give rise to preganglionic fibers that emerge from the spinal cord through the anterior roots.

The medial nucleus (S II - Co III) is located in the intermediate zone, where the lateral horns are absent - it receives impulses from the 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.

In the VII plate, Renshaw's interoneurons are concentrated, which are necessary for the implementation of motor function. They receive an excitatory impulse from the collagerals of the axon of motor neurons and inhibit their function. This is important for the coordinated work of motoneurons and muscles innervated by them for alternate flexion and extension of the limbs.

In the VIII plate, the interstitial nucleus of Cajal is localized. Its interoneurons switch information from afferent neurons to motoneurons. 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 the X plate, is located throughout the spinal cord and is formed by intercalary neurons of the autonomic part of the nervous system.

The anterior horns contain multipolar motoneurons (plate IX), which are the only executive cells of the spinal cord that send information to skeletal muscles. They combine into nuclei, each of which usually stretches over several segments. Motor neurons end in:

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

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

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

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

According to classical concepts, motoneurons 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 trunk.

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

The central nucleus - located in the lumbar and cervical regions, innervates the muscles of the girdles of the limbs.

White matter - it is divided by the anterior and posterior roots into symmetrical ventral, lateral and dorsal cords. It consists of longitudinal nerve fibers (mainly myelin), which form the descending and ascending paths (tracts), and astrocytes. Each tract is characterized by a predominance of fibers formed by the same type of neurons.

The pathways include 2 groups: propriospinal and supraspinal.

Propriospinal pathways - the spinal cord's own apparatus, formed by the axons of intercalary neurons, which carry out communication between the segments of the spinal cord. These paths pass mainly on the border of white and gray matter in the composition of the lateral and ventral cords.

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

Pain, temperature, deep and tactile sensitivity is carried out along the ascending paths. These are the dorsal-thalamic tract, the dorsal and ventral spinal-cerebellar tracts, the tender and wedge-shaped bundles.

The spinal tracts provide the transmission of impulses to the brain. Some of them (there are 20 of them in total) are formed by the axons of the cells of the spinal cord 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 for the most part pass to the opposite side and form the lateral and ventral cortico-spinal tracts. The pyramidal system controls the precise voluntary movements of the skeletal muscles, especially the limbs.

The extrapyramidal system is formed by neurons whose bodies lie in the nuclei of the medulla and medulla oblongata and the pons, and the axons end on motor neurons and interneurons. This system predominantly controls the contraction of the tonic muscles responsible for maintaining posture and body balance.

Extrapyramidal descending pathways are represented by the rubrospinal pathway originating from the red nucleus and conducting an impulse from the nuclei of the cerebellum, as well as the tecto-spinal pathway, starting from the tectum 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, memorize facts, distinguish melodies, pass on experience to generations and much more. The human body is a complex, ideally 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 stimulates scientists to continue studying the brain and its functions, where one of the pressing issues remains - the role of gray matter in human life and in the formation of human intelligence.

Overview of gray matter

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

The gray substance (Latin substantia grisea) is responsible for most of the functions of human higher nervous activity. Thanks to her, a person perceives the 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 about 86 billion neurons, of course, this number is extremely approximate, since modern medicine does not yet have the ability to count the exact number of nerve cells.

The white substance or (Latin 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 gray matter. Each nucleus has a corresponding responsibility and function: visual, auditory functions, blood circulation, breathing, movement, urination, etc.

Consists of gray matter nuclei that 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 brain (medulla oblongata, thalamus, hypothalamus, etc.).

The gray matter appears as a membrane of the brain, under which there is white, however, in the spinal cord, the 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 outline of the letter H, and it is already covered with white matter.

Gray matter structure

Substantia grisea is a perfectly arranged structure, which includes:

• neurons;
• dendrites;
• myelin-free axons;
• glial cells;
• thin capillaries.

The latter color the bark brown and, contrary to popular belief, the substance is not gray, but gray-brown. Numerous labyrinth-like cavities and bulges - forming convolutions - known as gyri. The main function of gray matter is to ensure the connection of the human body with the outside world, as well as to regulate reflexes and ensure higher mental functions.

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

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

• The back ones are composed of intermediate nerve cells. Receive signals from 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 substantia grisea functions 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 ensuring higher nervous activity, due to which a person is able to think, remember, perceive, etc.
2. In the medulla oblongata, the nuclei of the substance regulate motor processes, balance, provide coordination of movements, and also regulate metabolism, respiratory processes and blood supply.
3. In the cerebellar cortex, the gray nuclei are responsible for coordination of movements and orientation in space.
4. AT diencephalon the nuclei are responsible for controlling the activity of internal organs, regulate reflexes and body temperature.
5. In the terminal brain, 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 conductive. The first three functions are assigned to gray, 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. The corresponding cells of the spinal cord send signals to a specific muscle group, prompting one or another action, so that we can purposefully turn our head, move our neck, raise and lower our arms, and walk.
3. The sensory function is the transmission of an impulse coming from the afferent fibers of the trunk to the parts of the brain, from where a command containing a reaction to a stimulus comes.
4. The conductive function is to ensure 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 human abilities

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

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

Experiments by British scientists have shown that the thinner the cerebral cortex, therefore, the smaller the volume of gray substance, the worse a person copes with solving logical problems, the less various abilities he has, and also with a low volume of substance, the subjects often had problems with the speed of reaction , speech dysfunctions, problems with memorization and weak intellectual abilities.

At the same time, studies have shown that the study foreign languages, memorizing poetry, scientific or artistic works and playing music affects the increase in the cerebral cortex. The longer and more intense the study process, the larger the volume of the gray substance becomes, therefore, the more abilities, including mental, manifests a person.

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

• a person's way of life is 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, a significant decrease in the amount of brain tissue is observed, which affects 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 former argue that the mass and volume of the brain affects the mental abilities of a person.
2. The latter are sure that the volume of gray matter plays a secondary role.

At different times, scientists from different countries tried to determine the connection 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. person.

We can say with confidence that a weak connection 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 lobes of the brain.

Modern scientists suggest that human IQ is a complex and multifaceted concept, and various structures are involved in the formation of human intelligence, 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 the substantia grisea is associated with the intellectual abilities of a 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 efficiently 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'll 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 consists of two types of nervous tissue - gray matter and white. Gray matter nervous system is a collection of nerve cells responsible for most of the functions of human higher nervous activity. Function white cells - transmission of electrical impulses to different parts of the brain. The thickness of the gray brain tissue reaches about half a centimeter in the population. Topographically, the gray matter is the shell of the brain, underneath 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, myelin-free long processes - axons - are part of the gray matter. Unlike gray matter, which does not have myelin fibers, white matter is called white because the color is given by the myelin sheaths of axons.

The nuclei of the gray matter are histological structures, a concentric accumulation of bodies of nerve cells that performs 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 a regulator of a specific function of the body, be it the act of urination or the center of the heartbeat.

There is a partial misconception that the gray matter consists of long processes of neurons. Specialized processes, equipped with a fast myelin conductor, consist in the structure of the white matter of the brain and spinal cord, while in the gray matter there are only dendrites and myelin-free long fibers. 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 to transmit 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 set of elements that is inherent in other brain structures also belongs to the gray matter of the final brain.

Where is 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 brain sciences study brain function rather than location and structure.
The gray matter is the cortex of the cerebral hemispheres. The average layer of dark fabric is about 3-4mm (from 1.5 to 5mm). It has the most pronounced thickness in the region of the anterior central gyrus. Due to the arrangement of the set, the area of \u200b\u200bgray matter is significantly increased. In addition to the brain, the gray matter layer is located inside the spinal cord.

In the cerebellum, the bulk of the gray matter is located by analogy with the brain: the gray matter is the cerebellar cortex 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 - a molecular ball, pear-shaped neurons and a 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 foramen magnum, and goes 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 reticular formation. The nuclei formed by dark tissue include the hypoglossal, accessory, vagus and glossopharyngeal nerves. It should be noted that all these centers are not lower or higher centers of regulation - they occupy an intermediate position in the hierarchy of the brain's regulatory systems.

The structure located above the oblong is called a bridge. At the place of its connection with the adjacent structure, several nerves emerge, 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 nerves. These nerves are responsible for the innervation of the facial (facial) muscles, the scalp (scalp), some muscles of the eyes and parts of the tongue. In addition to such functions, the task of the Varolium 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 striopadllidal system of the brain.

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

The conclusion suggests itself that any structure with 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 the lower, and even higher mammals, the gray substance endowed a person with the ability to have a unique property of matter, the object of study of all neurosciences and philosophy is consciousness and self-awareness, the result of which is abstract thinking, developed memory, inner speech and many other specific attributes of higher nervous activity Homo sapiens.

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

• Physiological tasks: generation, transmission, reception 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. Back in the 18th century, Franz Gall drew attention to the dark substance of the brain. The scientist was the first to manage 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 cerebral function was lost. A serious impetus for further research was the study of the work of the cortex by Academician Pavlov, who studied basic reflexes and the principles of fixing a conditioned reflex. Parallel to him, his French colleagues found the speech center in the cortex - the lower part of the frontal gyrus. Modern science, although he knows many properties of the cerebral cortex, he claims that the percentage of knowledge and it is no more than one thousandth.

One blank spot in the empirical knowledge of the brain and its formation is the question of what is the heterotopy 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, symptoms are removed by one. As you know, heterotopy is a defective accumulation of neurons that have stopped at a certain place and have not reached their histological site. So, if there is a cause of the pathology - there will be an etiological treatment. A variant of the manifestation of heterotopy is childhood epilepsy.

Difference from white matter

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

Gray matter

• Created by the nuclei of nerve cells and similar ones.
• It is located mainly in the central parts of the nervous system.
• It makes up no more than 40% of the total brain mass.
• It consumes about 3-5 ml of oxygen per minute.
• A structure with a 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 a nerve impulse through the nervous system

It should be remembered that in contrast to the structure of the cerebral cortex, where the gray matter is a membrane and covers the white matter, 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 using microelectrodes, which, being close to the cells, touch them and seem to bite 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 the minimum 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 key in the study of biological rhythms, in particular sleep. Also, electroencephalography painlessly allows you to see the change in the gray matter in a child. The technique is not invasive, unlike the previous one.
• Magnetoencephalography. MEG allows one to study the synchronous activity of gray matter fields. After all, part of it is desynchronization that is the cause of many pathological states 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 imaging. With this method, gray matter can be seen in the brain, since NMRI gives a picture of tissue structure.

Introduction

The nervous system (systema nervosum) is divided into central and peripheral divisions. The central nervous system (CNS) is represented by the brain (encephalon) and the spinal cord (medulla spinalis). 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 vertebral canal and is a cylindrical cord, flattened from front to back, 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. By participating in the perception of sensory information, the spinal cord regulates segmental reflex activity.

The spinal cord is protected by the bone tissue of the spine and surrounded by membranes. The thickness of the spinal cord is not the same and 2 thickenings are distinguished 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 it is attached to it. The thickening develops in parallel with the growth and formation of the limbs. Nerves extend from the cervical thickening to the arms, and from the lumbar to the legs. Thickening is a collection of nerve cells.

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

Figure: The structure of the spinal cord: 1 - Pia mater spinalis (soft shell); 2 - Sulcus medianus posterior (posterior median groove); 3 - Sulcus intermedius posterior (intermediate posterior groove); 4 - Radix dorsalis (back spine); 5 - Cornu dorsale (rear horn); 6 - Cornu laterale (lateral horn); 7 - Cornu ventrale (front horn); 8 - Radix ventralis (front spine); 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. Allocate gray and white matter.

Gray matter - substantia grisea

White matter - substantia alba

On the cross section of the spinal cord, the area of \u200b\u200bgray matter surrounding the central canal is clearly visible in the form of a butterfly, or in the form of the letter H. This area 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 determines the characteristic color of this zone.

Gray matter of the spinal cord

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

1. Root cells - large motor neurons (motoneurons) 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 are directed to the periphery and innervate skeletal muscles.

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

The gray matter, substantia grisea, lies inside the spinal cord and is surrounded on all sides by white matter. The gray matter forms two vertical columns located in the right and left halves of the spinal cord. In the middle of it lies a narrow central canal, canalis centralis, of the spinal cord, which runs along 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 the transverse sections of the spinal cord, these columns have the appearance of horns: anterior, expanded, cornu anterius, and posterior, pointed, cornu rosterius. Therefore, the general appearance of gray matter against a white background resembles the letter N.

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

On a cross section in the gray matter, three horns are distinguished: cornu posterior, cornu lateralis and cornu anterior (front, side and rear horns).

Rear horns

In the posterior horns there are intercalary neurons, which are either part of the reflex arcs, which are closed at the segment level, or form ascending pathways that conduct sensory information to the brain. Neurons that switch and process pain signals are located closest to the surface of the dorsal horn. Cells lie somewhat ventrally, the axons of which conduct impulses from skin receptors. The insertion neurons are located deepest in the posterior horns, receiving information from muscle receptors.

Hind horn structure

Roland's gelatinous substance consists of neuroglia. It contains small stellate and triangular neurons. Their axons serve intra-segment connections. Roland's substance is especially clearly expressed in the upper cervical and lumbar segments, and in the thoracic segment it decreases slightly.

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

The Lissauer's marginal zone is well expressed in the lumbosacral region and mainly consists of the central processes of the cells of the spinal ganglia, which enter the spinal cord as part of the dorsal roots (radix dorsalis). There are also small fusiform neurons. Their dendrites branch in the spongy zone, and axons go out into the lateral cord of the white matter and participate in the formation of their own bundles of the spinal cord.

The head of the posterior horn has its own nucleus. Its head forms the dorsal thalamic tract and the anterior spinal tract. At the base of the posterior horn, in its medial part, there is Clark's pillar. This is a large pectoral nucleus. Clark's pillar stretches from I thoracic to II lumbar segment of the vertebrae. From it, fibers that form the posterior spinal tract depart. The lateral part of 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.

Neurons of the spongy zone and gelatinous substance, as well as insertion cells in other parts of the posterior pillars, close reflex connections between the sensitive cells of the spinal ganglia and the motor cells of the anterior horns with switching in their own nucleus.

Side horns

The lateral horns are clearly expressed only in the case of the sympathetic nervous system. The axons of the lateral horn cells emerge from 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 thoracolumbar spinal cord and contain sympathetic neurons. The medial and lateral intermediate nuclei lie here.

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

Front horns

The ventral horns of the gray matter contain motonerons. They are not arranged randomly, but in accordance with the innervated muscles. Thus, the contractions of the muscles of the trunk are triggered by motor neurons located more ventrally, and the muscles of the limbs are triggered more dorsally. The anterior horns are most developed in the cervical and sacral regions of the spinal cord, where the motor neurons that innervate 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.

Between the lateral and posterior horns of the white matter, there are short strands of gray matter that make up the reticular formation of the spinal cord

The right and left columns of the gray matter of the spinal cord are connected by 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 down 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 pathways connect neurons above and below the segments of the spinal cord. This is necessary for the coordinated work of the gray matter zones that control different muscles while contracting (for example, the muscles of the arms and legs during walking and running). In addition, in the case of many large muscles, the motor neurons innervating them are stretched in the rostro-caudal direction over 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, which 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 (sensory, afferent) neurons.

3. Long centrifugal (motor, efferent) neurons.

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

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

In the posterior cords, there are ascending paths, in the anterior ones - mainly descending ones, in the lateral ones - both of them. The spinal cord's own pathways are directly adjacent to the gray matter in the region of both the posterior and anterior and lateral cords.

On a cross-section of different levels of the spinal cord, it can be seen that in the upper segments there is much more white matter than gray; in the lower segments the opposite is true. This is due to the fact that in the thoracic and, especially the cervical, sections in the white matter, there are practically all the axons connecting the spinal cord with the brain (both ascending and descending). The fibers that have reached the lower sections connect only the lumbar, sacral and coccygeal segments of the spinal cord to the brain. Consequently, there are significantly fewer of them.