Spinal cord, medulla spinalis (Greek myelos), lies in the spinal canal and in adults is a long (45 cm in men and 41-42 cm in women), somewhat flattened from front to back, cylindrical cord, which at the top (cranial) directly passes into medulla, and below (caudally) ends with a conical point, conus medullaris, at the level of the II lumbar vertebra. Knowledge of this fact is of practical importance (in order not to damage the spinal cord during a lumbar puncture for the purpose of taking cerebrospinal fluid or for the purpose of spinal anesthesia, it is necessary to insert a syringe needle between the spinous processes of the III and IV lumbar vertebrae). From the conus medullaris, the so-called terminal thread departs downward, filum terminale, representing the atrophied lower part spinal cord, which below consists of a continuation of the membranes of the spinal cord and is attached to the II coccygeal vertebra.

The spinal cord along its course has two thickenings corresponding to the nerve roots of the upper and lower extremities: the upper one is called the cervical thickening, intumescentia cervicalis, and the lower one is called the lumbosacral, intumescentia lumbosacralis. Of these thickenings, the lumbosacral is more extensive, but the cervical is more differentiated, which is associated with a more complex innervation of the hand as a labor organ.

Formed as a result of thickening of the side walls of the spinal tube and running along the midline of the anterior and posterior longitudinal grooves: deep fissura mediana anterior, and superficial, sulcus medianus posterior, the spinal cord is divided into two symmetrical halves - right and left; each of them, in turn, has a slightly pronounced longitudinal groove running along the line of entry of the posterior roots (sulcus posterolateralis) and along the line of exit of the anterior roots (sulcus anterolateralis). These grooves divide each half of the white matter of the spinal cord into three longitudinal cords: anterior - funiculus anterior, lateral - funiculus lateralis and posterior - funiculus posterior. The posterior cord in the cervical and upper thoracic regions is also divided by an intermediate groove, sulcus intermedius posterior, into two bundles: fasciculus gracilis and fasciculus cuneatus. Both of these bundles, under the same names, pass at the top to the posterior side of the medulla oblongata.

On both sides, the roots of the spinal nerves emerge from the spinal cord in two longitudinal rows. Anterior root, radix ventralis s. anterior, exiting through sulcus anterolateralis, consists of neurites of motor (centrifugal, or efferent) neurons, the cell bodies of which lie in the spinal cord, while the back root, radix dorsalis s. posterior, which is part of the sulcus posterolateralis, contains processes of sensitive (centripetal, or afferent) neurons, the bodies of which lie in the spinal nodes.

At some distance from the spinal cord, the motor root is adjacent to the sensory one, and together they form the trunk of the spinal nerve, truncus n. spinalis, which neuropathologists distinguish under the name of the funiculus, funiculus. With inflammation of the cord (funiculitis), segmental disorders occur simultaneously in the motor and sensory spheres; with root disease (sciatica), segmental disorders of one sphere are observed - either sensitive or motor, and with inflammation of the nerve branches (neuritis), the disorders correspond to the distribution zone of this nerve. The trunk of the nerve is usually very short, because after exiting the intervertebral foramen, the nerve splits into its main branches.

In the intervertebral foramina near the junction of both roots, the posterior root has a thickening - the spinal ganglion, ganglion spinale, containing false unipolar nerve cells (afferent neurons) with one process, which then divides into two branches: one of them, the central one, goes as part of the posterior root into the spinal cord, the other, peripheral, continues into the spinal nerve.

Thus, there are no synapses in the spinal nodes, since only the cell bodies of afferent neurons lie here. In this way, these nodes differ from vegetative nodes peripheral nervous system, since in the latter intercalary and efferent neurons come into contact. The spinal nodes of the sacral roots lie inside the sacral canal, and the node of the coccygeal root lies inside the sac of the dura mater of the spinal cord. Due to the fact that the spinal cord is shorter than the spinal canal, the exit point of the nerve roots does not correspond to the level of the intervertebral foramina. To get into the latter, the roots are directed not only to the sides of the brain, but also down, and the more sheer, the lower they depart from the spinal cord. In the lumbar part of the last nerve roots descend to the corresponding intervertebral foramina parallel to the filum terminate, enveloping it and the conus medullaris in a thick bundle, which is called the cauda equina.

Internal structure of the spinal cord. The spinal cord is made up of gray matter, which contains nerve cells, and white matter, which is made up of myelinated nerve fibers.

A. 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.

Central channel is a remnant of the cavity of the primary neural tube. Therefore, at the top it communicates with the IV ventricle of the brain, and in the region of the conus medullaris it ends with an extension - the terminal ventricle, ventriculus terminalis. The gray matter surrounding the central canal is called the intermediate, substantia intermedia centralis. In each column of gray matter there are two columns: anterior, columna anterior, and posterior, columna posterior. On transverse sections of the spinal cord, these pillars 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".

The gray matter consists of nerve cells grouped into nuclei, the location of which basically corresponds to the segmental structure of the spinal cord and its primary three-membered reflex arc. The first, sensitive, neuron of this arc lies in the spinal nodes, the peripheral process of which begins with receptors in organs and tissues, and the central one, as part of the posterior sensory roots, penetrates through the sulcus posterolateralis into the spinal cord. Around the top of the posterior horn, a border zone of white matter is formed, which is a collection of central processes of cells of the spinal ganglions ending in the spinal cord.

Cells of the posterior horns form individual groups or nuclei that perceive various types of sensitivity from the soma - somatically sensitive nuclei. Among them stand out: the thoracic nucleus, nucleus thoracicus (columna thoracica), most pronounced in the thoracic segments of the brain; the gelatinous substance located at the top of the horn, substantia gelatinosa, as well as the so-called own nuclei, nuclei proprii. The cells laid down in the posterior horn form the second, intercalary, neurons. In the gray matter of the posterior horns, scattered cells are also scattered, the so-called fascicular cells, the axons of which pass through the white matter in separate bundles of fibers. These fibers carry nerve impulses from certain nuclei of the spinal cord to its other segments or serve to communicate with third reflex arc neurons embedded in the anterior horns of the same segment. The processes of these cells, going from the posterior to the anterior horns, are located near the gray matter, along its periphery, forming a narrow border of white matter surrounding the gray on all sides. These are the own bundles of the spinal cord, fasciculi proprii. As a result, irritation coming from a certain area of ​​the body can be transmitted not only to the segment of the spinal cord corresponding to it, but also to others. As a result, a simple reflex can involve a whole group of muscles in a response, providing a complex coordinated movement, which, however, remains unconditioned reflex.

Anterior horns contain third, motor, neurons, the axons of which, leaving the spinal cord, make up the anterior, motor, roots. These cells form the nuclei of the efferent somatic nerves that innervate the skeletal muscles - the somatic motor nuclei. The latter have the form of short columns and lie in the form of two groups - medial and lateral. Neurons of the medial group innervate the muscles that developed from the dorsal part of the myotomes (autochthonous muscles of the back), and the lateral group - the muscles that originate from the ventral part of the myotomes (ventrolateral muscles of the trunk and muscles of the extremities); the more distally the innervated muscles, the more lateral the cells innervating them lie. The largest number of nuclei is contained in the anterior horns of the cervical enlargement of the spinal cord, from where they are innervated upper limbs, which is determined by the participation of the latter in the labor activity of a person. In the latter, due to the complication of the movements of the hand as an organ of labor, these nuclei are much larger than in animals, including anthropoids.

Thus, the posterior and anterior horns of gray matter are related to the innervation of the organs of animal life, especially the apparatus of movement, in connection with the improvement of which, in the process of evolution, the spinal cord developed. The anterior and posterior horns in each half of the spinal cord are interconnected by an intermediate zone of gray matter, which in the thoracic and lumbar regions of the spinal cord, extending from the I thoracic to the II-III lumbar segments, is especially pronounced and protrudes in the form of a lateral horn, cornu laterale. As a result, in these sections, the gray matter in the transverse section takes the form of a butterfly. The lateral horns contain cells that innervate the vegetative organs and are grouped into a nucleus, which is called columna intermediolateralis. The neurites of the cells of this nucleus leave the spinal cord as part of the anterior roots.

B. White matter, substantia alba, 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).
3. Long centrifugal (motor, efferent).

The first system (short fibers) refers to the own apparatus of the spinal cord, and the remaining two (long fibers) constitute the conductor apparatus of bilateral connections with the brain. The proper apparatus includes the gray matter of the spinal cord with the posterior and anterior roots and its own white matter bundles (fasciculi proprii), bordering the gray matter in the form of a narrow strip. In terms of development, its own apparatus is a phylogenetically older formation and therefore retains primitive structural features - segmentation, which is why it is also called the segmental apparatus of the spinal cord, in contrast to the rest of the non-segmented apparatus of bilateral connections with the brain.

Thus, the nerve segment is a transverse segment of the spinal cord and the right and left spinal nerves associated with it, which developed from one neurotome (neuromere). It consists of a horizontal layer of white and gray matter (posterior, anterior and lateral horns) containing neurons whose processes run in one paired (right and left) spinal nerve and its roots.

In the spinal cord, 31 segments are distinguished, which are topographically divided into 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal. A short reflex arc closes within the nerve segment. Since the own segmental apparatus of the spinal cord arose when there was still no brain, its function is the implementation of those reactions in response to external and internal stimuli that arose earlier in the process of evolution, i.e., innate reactions. The apparatus of bilateral connections with the brain is phylogenetically younger, since it arose only when the brain appeared. As the latter developed, the pathways connecting the spinal cord with the brain also grew outwards. This explains the fact that the white matter of the spinal cord, as it were, surrounded the gray matter on all sides. Thanks to the conduction apparatus, the own apparatus of the spinal cord is connected with the apparatus of the brain, which unites the work of the entire nervous system. Nerve fibers are grouped into bundles, and the cords visible to the naked eye are made up of the bundles: posterior, lateral and anterior. In the posterior funiculus, adjacent to the posterior (sensory) horn, there are bundles of ascending nerve fibers; in the anterior cord, adjacent to the anterior (motor) horn, are bundles of descending nerve fibers; finally, both are located in the lateral funiculus. In addition to the cords, the white matter is located in the white commissure, comissura alba, which is formed due to the intersection of the fibers in front of the substantia intermedia centralis; there is no white spike behind.

The posterior cords contain fibers of the posterior roots of the spinal nerves, which are composed of two systems:

• Medially located thin bundle, fasciculus gracilis.
• Laterally located wedge-shaped bundle, fasciculus cuneatus. The thin and wedge-shaped bundles conduct from the corresponding parts of the body to the cerebral cortex conscious proprioceptive (muscle-articular feeling) and skin (sense of stereognosis - recognition of objects by touch) sensitivity related to determining the position of the body in space, as well as tactile sensitivity.

The lateral cords contain the following bundles:

A. Ascending.

To the hindbrain:

• tractus spinocerebellaris posterior, the posterior spinal cerebellar path, is located in the posterior part of the lateral funiculus along its periphery;
• tractus spinocerebellaris anterior, the anterior spinal cerebellar path, lies ventral to the previous one. Both spinal cerebellar tracts conduct unconscious proprioceptive impulses (unconscious motor coordination).

To the midbrain:

• tractus spinotectalis, dorsal tract, adjacent to the medial side and anterior part of tractus spinocerebellaris anterior. To the diencephalon:
• tractus spinothalamics lateralis adjoins medially to tractus spinocerebellaris anterior, immediately behind tractus spinotectalis. It conducts temperature stimuli in the dorsal part of the tract, and pain in the ventral part;
• tractus spinothalamicus anteriror s. ventralis is similar to the previous one, but is located anterior to the lateral one of the same name and is the path for conducting impulses of touch, touch (tactile sensitivity). According to recent data, this tract is located in the anterior funiculus.

B. Descending.

From the cerebral cortex:

• lateral corticospinal (pyramidal) path, tractus corticospinalis (pyramidalis) lateralis. This tract is a conscious efferent motor pathway.

From the midbrain:

• tractus rubrospinalis. It is an unconscious efferent motor pathway.

From the hindbrain:

• tractus olivospinalis, lies ventral to tractus spinocerebellaris anterior, near the anterior funiculus. The anterior cord contains descending pathways.

From the cerebral cortex:

• the anterior corticospinal (pyramidal) path, tractus corticospinalis (pyramidalis) anterior, constitutes a common pyramidal system with the lateral pyramidal bundle.

From the midbrain:

• ractus tectospinalis, lies medial to the pyramidal bundle, limiting the fissura mediana anterior. Thanks to him, reflex protective movements are carried out with visual and auditory stimuli - the visual-auditory reflex tract.

A number of bundles go to the anterior horns of the spinal cord from various nuclei of the medulla oblongata related to balance and coordination of movements, namely:

• from the nuclei of the vestibular nerve - tractus vestibulospinalis - lies on the border of the anterior and lateral cords;
• from formatio reticularis - tractus reticulospinalis anterior, lies in the middle part of the anterior cord;
• the bundles proper, fasciculi proprii, are directly adjacent to the gray matter and belong to the spinal cord's own apparatus.

Which doctors to contact for examination of the Spinal Cord:

Neurosurgeon

Neurologist

Traumatologist

What diseases are associated with the spinal cord:

What tests and diagnostics need to be done for the spinal cord:

spinal cord CT

MRI of the spinal cord

X-ray of the spine

Angiography of the vessels of the spinal cord

Lumbar puncture

The human spinal cord refers to the organs of the central nervous system, which performs regulatory functions. The structure of the spinal cord of the brain.

The human spinal cord is located in the spinal canal, where there is a cavity formed by all parts of the spine.

There is no clear boundary for the transition of the spinal cord to the brain, therefore, the upper level of the first cervical vertebra is tentatively taken beyond the border.

In fact, the spinal cord is formed from white and gray matter, which are surrounded by three membranes: pia mater, arachnoid and dura mater. The cavities in between them and the spinal canal are filled with CSF.

The soft shell is represented by a connective tissue, in the thickness of which there is a circulatory network that feeds soft tissues. The arachnoid membrane is separated from the pia mater by a subarachnoid space filled with cerebrospinal fluid and blood vessels. The arachnoid membrane has growths or granulations that bulge into the venous circulatory network, and carry out the outflow of cerebrospinal fluid into the venous network. The dura mater, together with the periosteum, forms the epidural space, where adipose tissue and circulatory network. Merging with the periosteum of the intervertebral foramen, it forms sheaths for the spinal ganglia.

Human anatomy considers the structure of an organ above the intracellular level. The external is organized by segmentation type. Each segment is connected to the brain and peripheral nerves that innervate a specific area of ​​the human body.

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Content

The organ of the central nervous system is the spinal cord, which performs special functions and has a unique structure. It is located in the spinal column, in a special channel, directly connected with the brain. The functions of the organ are conductive and reflex activity, it ensures the work of all parts of the body at a given level, transmits impulses and reflexes.

What is the spinal cord

Latin name spinal cord medulla spinalis. This central organ of the nervous system is located in the spinal canal. The border between it and the brain passes approximately at the intersection of the pyramidal fibers (at the level of the occiput), although it is conditional. Inside is the central canal - a cavity protected by the pia, arachnoid and dura mater. Between them is the cerebrospinal fluid. The epidural space between the outer shell and the bone is filled with adipose tissue and a network of veins.

Structure

Segmental organization distinguishes the structure of the human spinal cord from other organs. This serves to connect with the periphery and reflex activity. The organ is located inside the spinal canal from the first cervical vertebra to the second lumbar, maintaining curvature. From above, it begins with an oblong section - at the level of the back of the head, and below - ends with a conical sharpening, a terminal thread of connective tissue.

The organ is characterized by longitudinal segmentation and the significance of the links: the anterior radicular filaments (axons of nerve cells) emerge from the anterolateral groove, forming the anterior motor root, which serves to transmit motor impulses. The posterior radicular threads form the posterior root, which conducts impulses from the periphery to the center. The lateral horns are equipped with motor, sensitive centers. The roots create the spinal nerve.

Length

In an adult, the organ is 40-45 cm in length, 1-1.5 cm in width, weighing 35 g. It increases in thickness from the bottom up, reaches the largest diameter at the upper cervical region (up to 1.5 cm) and the lower lumbar sacral (up to 1.2 cm). In the chest area, the diameter is 1 cm. Four surfaces are distinguished from the organ:

• flattened front;
• convex back;
• two rounded sides.

Appearance

On the front surface, along the entire length, there is a median fissure, which has a fold of the meninges - the intermediate cervical septum. Behind, a median groove is isolated, connected to a plate of glial tissue. These gaps divide the spinal column into two halves, connected by a narrow bridge of tissue, in the center of which is the central canal. From the sides there are also furrows - anterolateral and posterolateral.

Segments of the spinal cord

The sections of the spinal cord are divided into five parts, the meaning of which does not depend on the location, but on the section in which the outgoing nerves leave the spinal canal. In total, a person can have 31-33 segments, five parts:

• cervical part - 8 segments, at its level there is more gray matter;
• chest - 12;
• lumbar - 5, the second area with a large amount of gray matter;
• sacral - 5;
• coccygeal - 1-3.

gray and white matter

On the section of the symmetrical halves, a deep median fissure, a connective tissue septum, is visible. The inner part is darker - this is gray matter, and on the periphery is lighter - white matter. In cross section, the gray matter is represented by a "butterfly" pattern, and its protrusions resemble horns (anterior ventral, posterior dorsal, lateral lateral). Most of the gray matter is in the lumbar region, less in the thoracic region. At the brain cone, the entire surface is made gray, and along the periphery there is a narrow layer of white.

Functions of gray matter

What formed the gray matter of the spinal cord - it consists of bodies of nerve cells with processes without a myelin sheath, thin myelin fibers, neuroglia. The basis is multipolar neurons. Cells lie inside groups-nuclei:

• radicular - axons leave as part of the anterior roots;
• internal - their processes end in synapses;
• bundle - axons pass to the white matter, carry nerve impulses, form pathways.

Between the posterior and lateral horns, the gray extends into the white in strands, forming a mesh-like loosening - a mesh formation. The functions of the gray matter of the CNS are: the transmission of pain impulses, information about temperature sensitivity, the closure of reflex arcs, and the receipt of data from muscles, tendons and ligaments. The neurons of the anterior horns are involved in the connection of the departments.

White matter functions

A complex system of myelinated, unmyelinated nerve fibers is the white matter of the spinal cord. It includes the supporting nervous tissue - neuroglia, plus blood vessels, a small amount of connective tissue. The fibers are assembled in bundles that make connections between the segments. White matter surrounds gray matter, conducts nerve impulses, and performs intermediary activities.

Spinal Cord Functions

The structure and functions of the spinal cord are directly related. There are two important tasks of the work of the body - reflex, conduction. The first is the implementation of the simplest reflexes (withdrawal of the hand during a burn, extension of the joints), connections with skeletal muscles. Conductor transmits impulses from the spinal cord to the brain, back along the ascending and descending paths of movement.

reflex

The reflex function consists in the response of the nervous system to irritation. It includes withdrawal of the hand when injected, coughing when foreign particles enter the throat. The impulse from the receptors enters the spinal canal, switches the motor neurons that are responsible for the muscles, and causes them to contract. This is a simplified diagram of a reflex ring (arc) without the participation of the brain (a person does not think when performing an action).

Allocate congenital reflexes (breast sucking, breathing) or acquired. The former help to identify the correct operation of the elements of the arc, segments of the organ. They are checked during a neurological examination. The knee, abdominal, plantar reflexes are mandatory for checking a person's health. These are superficial types, deep reflexes include flexion-elbow, knee, Achilles.

Conductor

The second function of the spinal cord is conduction, which transmits impulses from the skin, mucous membranes and internal organs to the brain, in the opposite direction. White matter serves as a conductor, carries information, an impulse about external influences. Due to this, a person receives a certain sensation (soft, smooth, slippery object). With the loss of sensitivity, sensations from touching something cannot be formed. In addition to commands, impulses transmit data on the position of the body in space, pain, and muscle tension.

What human organs control the functioning of the spinal cord

Responsible for the spinal canal and the control of all the work of the spinal cord is the main organ of the central nervous system - the brain. Numerous nerves and blood vessels act as assistants. The brain has a great influence on the activity of the spinal cord - it controls walking, running, labor movements. With the loss of communication between organs, a person becomes practically helpless in the end.

Risk of damage and injury

The spinal cord connects all body systems. Its structure plays an important role in the proper functioning of the musculoskeletal system. If it is damaged, a spinal cord injury will occur, the severity of which depends on the extent of the damage: sprains, torn ligaments, dislocations, damage to the discs, vertebrae, processes - light, medium. Severe fractures include displaced fractures and multiple damage to the canal itself. This is very dangerous, leading to disruption of the functionality of the cords and paralysis. lower extremities(spinal shock).

If the injury is severe, the shock lasts from a few hours to months. Pathology is accompanied by a violation of sensitivity below the site of injury and dysfunction of the pelvic organs, including urinary incontinence. Computed resonance imaging can detect injuries. For the treatment of minor bruises and damage to the zones, medicines can be used, therapeutic gymnastics massage, physiotherapy.

Severe variants require surgery, especially diagnosing compression (rupture - cells die instantly, there is a risk of disability). The consequences of injury to the spinal cord are a long recovery period (1-2 years), which can be accelerated by acupuncture, occupational therapy and other interventions. After a severe case, there is a risk of not fully regaining motor ability, and sometimes staying forever in a wheelchair.

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Attention! The information provided in the article is for informational purposes only. The materials of the article do not call for self-treatment. Only a qualified doctor can make a diagnosis and make recommendations for treatment, based on individual features specific patient.

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The spinal cord of a human or animal is the most important part of the CNS. Through it, the brain communicates with muscles, skin, internal organs, and the autonomic nervous system. This ensures the vital activity of the body of a person, dog, cat or other mammal. The structure of the spinal cord is characterized by a complex organization and a narrow specialization of each area. Its biology is so arranged that any serious violation manifests itself in problems with motor functions, somatic anomalies.

Outwardly, this organ is very similar to a cord stretched in a special canal of the spine. It has a right side and a left side. In length, it does not exceed half a meter, and the diameter is about a centimeter.

We will consider in detail the structure of the spinal cord, the features of its organization, the principles of operation. Knowing the structure of the spinal cord, one can easily understand how our movements are born, how the activity of neurons can manifest itself. We will also tell you what functions the spinal cord performs.

There are 31 to 33 pairs of nerves in the spinal cord, so it is divided into 31-32 segments. Each corresponds to a part of our body and continuously performs its functions. The mass of such an important organ, without which no movement is possible, is only 35 grams.

The location area is the spinal canal. At the top, it immediately passes into the medulla oblongata, and below it is completed by the vertebrae of the coccyx.

Segmentation

The role of the spinal cord is to organize any human movements. To ensure maximum efficiency of its work, in the course of evolution, segments were identified, each of which ensures the functioning of a certain area of ​​the body.

This part of the nervous system begins to form as early as the 4th week of embryonic development, but the main functions of the spinal cord will not be able to perform immediately.

The parts of the spinal cord and their functions are now well understood. It is segmented into:

• neck segments (8 pieces);
• chest (12 pieces);
• lumbar (5 pieces);
• sacral (5 pieces);
• coccygeal (from 1 to 3 pieces).

The human back ends with a small coccyx. It is a rudiment, that is, a part that has lost its significance in the course of evolution. This is, in fact, the rest of the tail. Therefore, a person has very few coccygeal segments. He just doesn't need a tail anymore.

What is it needed for

The spinal cord is the center that collects all the information coming from the periphery. Then he sends commands to the muscles and tissues, bringing them into tone. This is how all movements are born. This is a complex and painstaking work, because a person makes hundreds of thousands of tiny movements a day. Its physiology is distinguished by the complex organization and interaction of all parts of the central nervous system.

The spinal cord is reliably protected by three membranes at once:

• hard;
• soft;
• cobweb.

Inside is cerebrospinal fluid. The center of the brain is filled with gray matter. In cross section, this area looks like a butterfly with its wings unfolded. Gray matter is a concentrate of neurons, it is they who are able to transmit a bioelectric signal.

Each segment consists of tens and even hundreds of thousands of neurons. They ensure the full operation of the motor apparatus.

There are three types of protrusions (horns) in the gray matter:

• front;
• rear;
• side.

distributed between the zones. different types neurons. This is a complex and well-organized system, which has its own characteristics. In the zone of the anterior horns there are a huge number of large motor neurons. Small intercalary neurons are located in the posterior horns, and visceral (sensory and motor) neurons are located in the lateral horns.

It is the nerve fibers that form the pathways along which the signal is conducted.

In total, scientists have counted more than thirteen million nerve fibers in the human spinal cord. The protective function for them is performed by the external vertebrae that form the spine. It is in them that the inner delicate and vulnerable spinal cord is located.

The gray matter is surrounded on all sides by many nerve fibers. The transmission of bioelectrical signals is carried out through the thinnest processes of neurons. Each can have from one to many such processes. Neurons themselves are extremely small. Their diameter is not more than 0.1 mm, but the processes are striking in their length - it can reach one and a half meters.

The gray matter has different types cells. The anterior sections are composed of motor cells, they are very large. As the name suggests, they are responsible for motor functions. These are thin, but very long fibers that go directly from the spinal cord to the muscles and set them in motion. These fibers form large bundles and leave the spinal cord. These are the front roots. One of them goes to the right, and the other to the left.

In each department there are such sensitive fibers, from which a pair of roots is formed. Some of the sensory fibers are connected to the brain. The second part is directed directly to the gray matter. It terminates the fibers. Different types of cells become the ending for them - motor, intermediate, intercalary. Through them, continuous regulation of movements and organs is carried out.

Organization of pathways

The pathways of the whole organism are usually divided into:

• associative;
• afferent;
• efferent.

The task of associative paths is to connect neurons between all segments. These connections are considered short.

Afferent provide sensitivity. These are ascending pathways that receive information from all receptors and send it to the brain. Efferent pathways carry signals from the brain to neurons throughout the body. They belong to the descending paths.

Functions

The activity of the spinal cord is continuous. It provides the motor activity of the body. There are two main functions of the human spinal cord - reflex and conduction.

Each department provides the work of a completely specific area of ​​\u200b\u200bthe body. Segments (cervical, thoracic, for example) provide the functions of the organs of the sternum, hands. The lumbar segment is responsible for the full functioning of the muscles and the digestive system. The sacral segment is responsible for the functions of the pelvic organs and legs.

reflex

The reflex brain function is to organize reflexes. This allows the body, for example, to instantly respond to a signal of pain. The action of reflexes is striking in its efficiency. A person withdraws his hand from a hot object in a split second. During this time, information from receptors to the brain and back has managed to travel a long way along the reflex arc.

When the sensitive nerve endings of the skin, muscle fibers, tendons, joints are irritated, this means that a nerve impulse has been sent to them. Such signals propagate along the posterior roots of the nerve fibers and arrive in the spinal cord. Receiving a signal, motor and intercalary cells are excited. Then, along the motor fibers of the already anterior roots, the impulses are sent to the muscles. Having received such a signal, the muscle fibers contract. Simple reflexes occur according to this mechanism.

A reflex is the body's response to a stimulus. All reflexes are provided by the work of the central nervous system. One of the functions of the spinal cord is reflex. It is provided by the so-called reflex arc. This is a complex path that nerve impulses travel from the peripheral components of the body to its spinal cord, and from it directly to the muscles. This is a difficult but vital process.

The simplest reflexes can save a person's life and health. Pulling away the hand that touched the hot, we do not even suspect that the signal from the skin was transmitted at lightning speed along the nerve fibers to the brain, and then to the spinal cord. In response, an impulse was sent out that contracted the muscles of the arm to avoid being burned. This is a vivid manifestation of the reflex function.

Neurophysiologists have studied in detail almost all reflexes and neural arcs that ensure their implementation. These data allow for effective rehabilitation after injuries and a number of diseases, as well as help in their diagnosis.

It is on this reflex that the diagnosis by a neurologist is based, in which the doctor easily strikes the tendon of the patient's patella with a hammer. This is how the knee reflex is studied, by which one can judge the state of a certain section of the spinal cord.

However, the spinal cord is not an independent reflex system. Its functions are constantly controlled by the brain. They are closely connected by special bundles of nerve fibers. The fibers are very long, thin, composed of white matter. Signals are transmitted one by one to the brain up, and by others - to the spinal cord.

The entire central nervous system is involved in the formation of coordinated complex movements. Each movement is a continuous stream of impulses from the brain to the spinal cord, from it to the muscle fibers.

Conductor

This is the second important feature. It consists in the fact that nerve signals are transmitted from the spinal cord higher to the brain. There, in the subcortical and cortical regions, all information is instantly processed, and appropriate signals are sent in response to it.

The conductor function works at those moments when we decide to take something, get up, go. This happens instantly, without spending time thinking.

This function is mostly provided by intermediate or intercalary neurons. They send a signal to motor neurons, and also process information that comes from the skin and muscles. Here there are peripheral signals and impulses from the brain.

An excitatory impulse is sent with the help of inserted cells to different groups of motor cells. At the same time, the activity of other groups is inhibited. It is this complex process that ensures coherence and high coordination of human movements. This is how the refined movements of the pianist, ballerina appear.

Possible diseases

In the human body there is a unique section, which is called the "horse tail". The spinal cord itself is absent in it, and only cerebrospinal fluid and bundles of nerves remain. If they are compressed, the body begins to experience pain, there are violations of the musculoskeletal system. This disease at the location of the main cause is called "ponytail".

If a ponytail develops, a number of symptoms bother the person. There is pain in the lower back, the muscles experience weakness, the body begins to react much more slowly to external stimuli. Inflammation may appear, even the temperature rises. If these alarming symptoms are ignored, the condition worsens. It becomes difficult for a person to move or sit for a long time.

The spinal cord is an important link that transmits commands from the human brain. It is this organ that is responsible for all movements of the arms and legs, as well as for breathing and digestion. The spinal cord has a very complex structure and is located in the canal along the entire length of the spine. This channel is reliably protected by a special tube.

It is very difficult to overestimate the importance of the spinal cord, because only with its help all motor functions in humans are carried out. Even the beating of the heart is regulated with the help of signals, the conductor of which is the spinal structure. The length of this organ, of course, changes with age and in a middle-aged person it can average 43 cm.

The anatomy of the spinal cord suggests its conditional division into several sections:

• the cervical region is the transition of the spinal cord to the brain;
• in thoracic region the smallest thickness of the spinal cord;
• in the lumbar region there are nerve endings responsible for the action of the limbs;
• sacral calving performs the same function as the lumbar;
• the coccygeal region forms a cone and is the end of the spinal cord.

The spinal cord is protected by 3 sheaths that cover it along its entire length. These shells are called soft, arachnoid and hard. Soft meninges, internal, is closest to the organ and provides its blood supply, being a receptacle blood vessels. The arachnoid meninge is medium in its location. The space between the soft and arachnoid membranes is filled with liquid. This fluid is called cerebrospinal fluid or, in medical terminology, cerebrospinal fluid. It is this liquid that is of interest to physicians when taking a puncture.

Being part of the central nervous system, the brain is formed already at the beginning of the 4th week of fetal development inside the mother's womb. However, some parts of this organ are fully formed only by 2 years of a child's life.

The dura mater is external or external. This sheath serves to conduct and maintain nerve endings - roots. The so-called ligaments, which are part of the anatomy of the spinal cord, serve to secure the organ to the spine. Each such ligament is located inside the spinal canal. A small tube runs through the center of the spinal cord called the central canal. It also contains cerebrospinal fluid, or cerebrospinal fluid. The so-called fissures protruding into the spinal cord conditionally divide it into left and right halves.

Each such nerve fiber is a conductor of nerve impulses that carry specific information.

Segments are conditional components of the spinal cord. Each segment has nerve roots that connect nerves with certain organs and parts of the human body. Each segment has 2 roots - anterior and posterior. Each root of the anterior pair is responsible for the transmission of information for the contraction of certain muscle groups and is called motor. The posterior roots are responsible for transmitting information in the opposite direction - from the receptors to the spinal canal. For this reason, the roots are called sensitive.

Furrows are the second type of depressions in the spinal cord. Such furrows conditionally divide the brain into cords. In total, there are 4 such cords - two on the back of the canal and one on the sides. The nerves, which are the basis of the spinal cord, pass through these cords in the form of fibers.

Each segment is located in its department, has well-defined functions and performs specific tasks. Each department contains several segments. Yes, in cervical region there are 8 of them, in the chest - 12, in the lumbar and sacral regions - 5 each. The coccygeal remains. The fact is that this is the only department that can contain an indefinite number of segments - from 1 to 3.

The spaces between the vertebrae serve to conduct the roots of specific segments. The roots, depending on the location of the department, can be of different lengths. This is due to the fact that in different departments the distance from the spinal cord to the intervertebral space is not the same. The direction of the roots may also differ from the horizontal.

Any segment has its own area of ​​responsibility: muscles, organs, skin and bones. This circumstance makes it possible for experienced neurosurgeons to easily determine the affected area in the spinal cord based on the sensitivity of a particular area of ​​the human body. This principle takes into account the sensitivity of both, for example, the skin, as well as muscles and various human organs.

In the structure of this organ, the presence of two more substances is distinguished - gray and white. By gray spinal substance can determine the location of neurons, and white gives out the presence of the nerve fibers themselves. White matter, arranged in the form of butterfly wings, has several protrusions resembling horns. There are anterior, posterior and lateral horns. The latter are not found in all segments. The anterior horns are neurons responsible for the motor functions of the body. And the posterior horns are those neurons that receive incoming information from receptors. Each of the lateral horns is responsible for the functioning of the human autonomic system.

Special sections of the spinal cord are responsible for the work of the internal organs. So, each segment is associated with a specific organ. This fact is widely used in diagnostics.

Functions and features of physiology

- conductive and reflex. The reflex function is responsible for a person's reaction to external stimuli. An example to demonstrate the reflex function is the temperature effect on the skin. If a person gets burned, he withdraws his hand. This is a manifestation of the reflex function of the spinal cord. It is very important, as it protects a person from unwanted external influences.

The mechanism of reflex action is as follows. Receptors on human skin are sensitive to hot and cold. Receptors instantly transmit information about any effect on the skin to the spinal cord in the form of an impulse. For such transmission, special nerve fibers are used.

The impulse is received by the neural body located in the space between the vertebrae. The body of the neuron and the nerve fiber are interconnected by the so-called spinal ganglion. Further, the impulse received from the receptor and passed along the fiber and through the node is transmitted to the posterior horns discussed above. The posterior horns transmit impulses to another neuron. Already located in the anterior horns, this neuron, to which the impulse was transmitted, is motor, and thus an impulse is formed that makes the hand withdraw, for example, from a hot kettle. At the same time, we do not think whether to withdraw our hand or not, she does it as if by herself.

This mechanism describes the general principle of creating a reflex arc, which provides a closed cycle from receiving a command from the receptor to transmitting a motor impulse to the muscle. This mechanism is the basis of the reflex function.

Types of reflexes can be both congenital and acquired. Each arc closes at a certain level. For example, a favorite reflex, checked by a neurologist, when struck under the kneecap, closes its arc on the 3rd or 4th segment lumbar spinal cord. In addition, according to the level of external influence, superficial and deep reflexes are distinguished. A deep reflex is just determined when exposed to a hammer. Superficial ones occur with a light touch or prick.

The transmission of impulses from receptors to the brain center is called the conduction function of the spinal cord. Part of this mechanism has been discussed above. The center of this is the brain. That is, the spinal brain is an intermediary in this chain. The conductive function ensures the transmission of impulses in the opposite direction, for example, from the brain to the muscles. The conductive function is provided by the white matter. After processing the transmitted impulse by the brain, a person receives one or another sensation, for example, of a tactile nature. At the same time, the brain of the spinal region does nothing by itself, except for the accurate transmission of impulses.

If at least one link in the transmission of information is broken, then a person may lose some feelings. Violation in the activity of the spinal cord can occur with back injuries. So, we found out that the conductive function ensures the movement of the human body in one direction and forms sensations, passing information in another. How many neurons and connections are involved in this? They number in the thousands, and it is impossible to calculate the exact number.

But that's not all, the conductive function of the spinal cord also controls human organs. For example, through the dorsal region, the human heart receives information from the brain about the frequency of contractions required at the moment. Thus, it is very difficult to overestimate the importance of the spinal cord. After all, all functions of the body, without exception, pass through the spinal cord. Understanding how the human spinal cord is arranged is widely used in neurology to accurately determine the causes of certain disorders.