They are separated by the anterior median fissure and contain descending conductors from the anterior central gyrus, stem and subcortical formations to the anterior horns of the spinal cord.

* spinothalamic pathway

(conducts pain, temperature and partially tactile sensitivity)

* medial loop

(common path of all types of sensitivity. They end in the thalamus)

* bulbothalamic pathway

(conductor of articular-muscular, tatkil, vibrational sensitivity, feeling of pressure, weight. Proprioreceptors are located in muscles, joints, ligaments, etc.)

* loop of the trigeminal nerve

(joins the inner loop, approaching it from the other side)

* lateral loop

(auditory pathway of the brain stem. It ends in the internal geniculate body and the posterior tubercle of the quadrigemina)
* spino-cerebellar pathways
(carry proprioceptive information to the cerebellum. The Gowers bundle begins at the periphery in the proprioceptors)
* posterior spin-cerebellar pathway
(flexic sheaf) has the same origin

№30 Physiology of the spinal cord. Bell–Magendie law

The spinal cord has two functions: reflex and conduction. As a reflex center, the spinal cord is able to carry out complex motor and autonomic reflexes. Afferent - sensitive - ways it is connected with receptors, and efferent - with skeletal muscles and all internal organs. The spinal cord connects the periphery with the brain through long ascending and descending pathways. Afferent impulses along the pathways of the spinal cord are carried to the brain, carrying information about changes in the external and internal environment of the body. Downward pathways impulses from the brain are transmitted to the effector neurons of the spinal cord and cause or regulate their activity.

reflex function. The nerve centers of the spinal cord are segmental or working centers. Their neurons are directly connected with receptors and working organs. In addition to the spinal cord, such centers are found in the medulla oblongata and midbrain. The suprasegmental centers have no direct connection with the periphery. They govern it through segmental centers. The motor neurons of the spinal cord innervate all the muscles of the trunk, limbs, neck, as well as the respiratory muscles - the diaphragm and intercostal muscles. In addition to the motor centers of skeletal muscles, there are a number of sympathetic and parasympathetic autonomic centers in the spinal cord. In the lateral horns of the thoracic and upper segments of the lumbar spinal cord, there are spinal centers of the sympathetic nervous system that innervate the heart, blood vessels, sweat glands, digestive tract, skeletal muscles, i.e. all organs and tissues of the body. It is here that neurons lie that are directly connected with the peripheral sympathetic ganglia. In the upper thoracic segment, there is a sympathetic center for pupil dilation, in the five upper thoracic segments - sympathetic cardiac centers. In the sacral spinal cord, there are parasympathetic centers innervating the pelvic organs (reflex centers for urination, defecation, erection, ejaculation). The spinal cord has a segmental structure. A segment is a segment that gives rise to two pairs of roots. If the back roots of a frog are cut on one side and the front roots on the other, then the paws on the side where the back roots are cut lose sensitivity, and on the opposite side, where the front roots are cut, they will be paralyzed. Consequently, the posterior roots of the spinal cord are sensitive, and the anterior roots are motor. Each segment of the spinal cord innervates three transverse segments, or metameres, of the body: its own, one above and one below. Skeletal muscles also receive motor innervation from three adjacent segments of the spinal cord. The most important vital center of the spinal cord is the motor center of the diaphragm, located in the III-IV cervical segments. Damage to it leads to death due to respiratory arrest.

The conduction function of the spinal cord. The spinal cord performs a conductive function due to the ascending and descending pathways passing through the white matter of the spinal cord. These pathways connect individual segments of the spinal cord with each other, as well as with the brain.

Bella - Magendie law in anatomy and physiology, the main regularity in the distribution of motor and sensory fibers in the nerve roots of the spinal cord. B. - M. h. established in 1822 by the French physiologist F. Magendie. It was partly based on the observations of the English anatomist and physiologist C. Bell published in 1811. According to B. - M. z., centrifugal (motor) nerve fibers exit the spinal cord as part of the anterior roots, and centripetal (sensitive) fibers enter the spinal cord as part of the posterior roots. Centrifugal nerve fibers also exit through the anterior roots, innervating smooth muscles, vessels and glands.

№ 31 Segmental and intersegmental principle of the spinal cord

The spinal cord is a cylindrical cord, covered with membranes, freely located in the cavity of the spinal canal. At the top, it passes into the medulla oblongata; below the spinal cord reaches the region of the 1st or upper edge of the 2nd lumbar vertebra. The diameter of the spinal cord is not the same everywhere, in two places two spindle-shaped thickenings are found: in the cervical region - cervical thickening - intumescentia cervicalis (from the 4th cervical to the 2nd thoracic vertebra); in the lowest part of the thoracic region - lumbar thickening - intumescentia lumbalis - (from the 12th thoracic to the 2nd sacral vertebra). Both thickenings correspond to areas of closure of reflex arcs from the upper and lower extremities. The formation of these thickenings is closely related to segmental principle structures of the spinal cord. There are a total of 31-32 segments in the spinal cord: 8 cervical (C I - C VIII), 12 thoracic (Th I -Th XII), 5 lumbar (L I -L V), 5 sacral (S I -S V) and 1 - 2 coccygeal (Co I - C II).

The lumbar thickening passes into a short cone-shaped section, into the medullary cone - from which a long thin terminal thread departs.

Segmental and intersegmental principle of the spinal cord: The spinal cord is characterized by a segmental structure, reflecting the segmental structure of the body of vertebrates. Two pairs of ventral and dorsal roots depart from each spinal segment. 1 sensory and 1 motor root innervates its transverse layer of the trunk i.e. metamer. This is the segmental principle of the spinal cord. The intersegment principle of operation is in the innervation by the sensory and motor roots of its metamere, the 1st overlying and 1st underlying metamere. Knowing the boundaries of body metameres makes it possible to carry out topical diagnostics of diseases of the spinal cord. 3. The conduction organization of the spinal cord The axons of the spinal ganglia and gray matter of the spinal cord go to its white matter, and then to other structures of the central nervous system, thereby creating the so-called conducting pathways, functionally subdivided into proprioceptive, spinocerebral (ascending) and cerebrospinal (descending). Propriospinal pathways connect neurons of one or different segments of the spinal cord. The function of such connections is associative and consists in the coordination of posture, muscle tone, movements of various body metameres.

№33 Physiological characteristics of the cranial nerves

Cranial nerves - 12 pairs of nerves emerging from the medulla at the base of the brain and innervating the structures of the skull, face, neck.

The motor nerves originate in the motor nuclei of the trunk. The predominantly motor nerves include a group of oculomotor nerves: oculomotor (3rd), trochlear (4th), abducens (6th), and also facial (7th), which controls mainly facial muscles, but also contains fibers of taste sensitivity and autonomic fibers that regulate the function of the lacrimal and salivary glands, accessory (11th), innervating the sternocleidomastoid and trapezius muscles, hyoid (12th), innervating the muscles of the tongue.

Sensory neurons are formed from the fibers of those neurons whose bodies lie in the cranial ganglia outside the brain. Sensitive ones include olfactory (1st), visual (2nd), vestibulocochlear, or auditory (8th), which provide, respectively, smell, vision, hearing and vestibular function.

The mixed nerves include the trigeminal (5th), which provides facial sensitivity and control of the masticatory muscles, as well as the glossopharyngeal (9th) and vagus (10th), which provide sensitivity to the posterior parts of the oral cavity, pharynx and larynx, as well as the functioning of the muscles pharynx and larynx. The vagus also provides parasympathetic innervation to the internal organs.

The cranial nerves are designated by Roman numerals in the order of their location:

I - olfactory nerve;

II - optic nerve;

III - oculomotor nerve;

IV - trochlear nerve;

V - trigeminal nerve;

VI - abducens nerve;

VII - facial nerve;

VIII - vestibulocochlear nerve;

IX - glossopharyngeal nerve;

X - vagus nerve;

XI - accessory nerve;

XII - hypoglossal nerve

No. 32 Medulla oblongata and pons. Their structure and functional significance

The structure and significance of the medulla oblongata subject to the general laws of the structure of the nervous system (the entire nervous system consists of gray and white matter). The medulla oblongata is an integral part of the rhomboid brain and is a direct continuation of the spinal cord. The medulla oblongata is divided into several parts by the same furrows as the spinal cord. On the sides of one of them (the anterior median sulcus) are the so-called pyramids of the medulla (it turns out that, as it were, the anterior cords of the spinal cord continue into these pyramids).

In these pyramids, the intersection of nerve fibers occurs. On the back side of the medulla oblongata runs the posterior median sulcus, on the sides of which lie the posterior cords of the medulla oblongata. In these posterior cords of the medulla oblongata are the continuation of the sensitive thin and wedge-shaped bundles. Three pairs of cranial nerves come out of the medulla oblongata - IX, X, XI pairs, which are respectively called - glossopharyngeal nerve, vagus nerve, accessory nerve. Also, the medulla oblongata takes part in the formation of the rhomboid fossa, which is the bottom of the 4th ventricle of the brain. In this 4th ventricle (more precisely, in the rhomboid fossa), the vasomotor and respiratory centers are located, if damaged, death occurs instantly. The internal structure of the medulla oblongata is very complex. It contains several nuclei of gray matter:

1. The core of the olive is an intermediate center of balance.

2. Reticular formation - a network of nerve fibers and their processes, passing throughout the entire brain, carries out the relationship and coordination of all brain structures.

3. nuclei of the cranial nerves described above.

4. Vasomotor and respiratory center

In the white matter of the medulla oblongata are fibers: long and short. Short ones carry out the relationship of various structures of the medulla oblongata itself, and long ones - the connection of the medulla oblongata with other structures of the central nervous system.

Bridge - the ventral part of the hindbrain, is a massive protrusion on the ventral surface of the brainstem (hindbrain).

Ventral the surface of the bridge faces the slope of the skull, dorsal participates in the formation of the rhomboid fossa.

* In the lateral direction, the bridge continues into a massive middle cerebellar peduncle leading to the cerebellum. At the border with the bridge, the trigeminal nerve (V) emerges from the pedicle. On the ventral surface of the bridge there is a shallow groove in which the basilar (main) artery lies. On its dorsal surface, on the border with the medulla oblongata, white cerebral stripes are visible, running transversely.

Inside the bridge there is a powerful bundle of transverse fibers called the trapezoid body, which divides the bridge into ventral and dorsal parts.

In the ventral part of the pons, there are own pontine nuclei, which are connected to the cerebral cortex with the help of cortical-bridge fibers. The axons of the pons' own nuclei, forming pontocerebellar fibers, go through the middle cerebellar peduncles to the cerebellar cortex. Through these connections, the cerebral cortex influences the activity of the cerebellum. Pyramid paths run at the base of the bridge.

The dorsal part of the bridge is located dorsally from the trapezius body, here are the nuclei of the trigeminal (V), abducens (VI), facial (VII) and vestibulocochlear (VIII) cranial nerves. In the central sections of the dorsal part of the bridge, along its entire length, there is a reticular formation. In the lateral sections of the dorsal part, there is a medial loop.

Functions of the pons: conductive and reflex. In this department there are centers that control the activity of facial and chewing and one of the oculomotor muscles. The pons receives nerve impulses from the receptors of the sense organs located on the head: from the tongue (taste sensitivity), the inner ear (auditory sensitivity and balance) and the skin.

№34 Anatomy and physiology of sensory cranial nerves

The cranial nerves are called peripheral nerves that originate from parts of the brain, and the nuclei of these nerves are laid in the brainstem (midbrain, pons and cerebellum).

Most cranial nerves enter the skull through the hindbrain. The cranial nerves III, IV, and VI control the six external muscles of the eye, which carry out the movements of this organ. Cranial nerves V (trigeminal) receive sensory information and transmit agile signals to the mandible, while cranial nerves VII (facial) carry sensory information from structures in the hyoid arch. The eighth cranial nerves (auditory) contain sensory fibers that are involved in hearing and maintaining balance. The IXth pair of cranial nerves (glossopharyngeal nerve) nerves the pharyngeal arch, carrying both sensory and agile signals.

Touch:

Olfactory nerve(The olfactory nerves are sensitive in function, consisting of nerve fibers that are processes of the olfactory cells of the olfactory organ. These fibers form 15-20 olfactory filaments (nerves) that leave the olfactory organ and through the cribriform plate of the mesh bone enter the cranial cavity, where they approach neurons of the olfactory bulb, nerve impulses are transmitted through various formations of the peripheral part of the olfactory brain to its central part.)

Visual(The optic nerve is sensitive in function, consists of nerve fibers that are processes of the so-called ganglion cells of the retina of the eyeball. From the orbit through the optic canal, the nerve passes into the cranial cavity, where it immediately forms a partial intersection with the nerve of the opposite side (optic chiasm) and lasts for visual tract.Due to the fact that only the medial half of the nerve passes to the opposite side, the right optic tract contains nerve fibers from the right halves, and the left tract from the left halves of the retina of both eyeballs.The optic tracts approach the subcortical visual centers - the nuclei of the upper hillocks of the roof of the midbrain, lateral geniculate bodies and pillows of the thalamus.The nuclei of the upper hillocks are connected to the nuclei of the oculomotor nerve (through them the pupillary reflex is carried out) and to the nuclei of the anterior horns of the spinal cord (orienting reflexes to sudden light stimuli are carried out).From the nuclei of the lateral geniculate bodies and pillows of the thalamus, nerve fibers in the composition of the white matter of the hemispheres follow the cortex of the occipital lobes (visual sensory cortex).)

Spatial-cochlear(a nerve of special sensitivity, consisting of two roots of different function: the vestibular root, which carries impulses from the static apparatus, represented by the semicircular ducts of the vestibular labyrinth, and the cochlear root, which conducts auditory impulses from the spiral organ of the cochlear labyrinth. VIII pair - the vestibulocochlear nerve - connects the hearing organs , equilibrium and gravity)

№35 Anatomy and physiology of motor cranial nerves

(III, IV, VI, XI and XII pairs) - motor nerves:

oculomotor nerve(according to the motor function, it consists of motor somatic and efferent parasympathetic nerve fibers. These fibers are the axons of the neurons that make up the nuclei of the nerve. There are motor nuclei and an additional parasympathetic nucleus. They are located in the brain stem at the level of the upper mounds of the roof of the midbrain. The nerve exits the cavity of the skull through the superior orbital fissure into the orbit and is divided into two branches: superior and inferior.The motor somatic fibers of these branches innervate the superior, medial, inferior rectus and inferior oblique muscles of the eyeball, as well as the muscle that lifts the upper eyelid (they are all striated) , and the parasympathetic fibers - the muscle that narrows the pupil, and the ciliary muscle (both smooth. Parasympathetic fibers switch on the way to the muscles in the ciliary node, which lies in the posterior part of the orbit.)

Block nerve(according to the motor function, it consists of nerve fibers extending from the nucleus. The nucleus is located in the legs of the brain at the level of the lower mounds of the roof of the midbrain. The nerves exit the cranial cavity through the superior orbital fissure into the orbit and innervates the superior oblique muscle of the eyeball.)

Abducens nerve(by function, the motor consists of nerve fibers extending from the neurons of the nerve nucleus located in the bridge. It exits the skull through the superior orbital fissure into the orbit and innervates the lateral (external) rectus muscle of the eyeball.)

facial nerve(mixed in function, includes motor somatic fibers, secretory parasympathetic fibers and sensory taste fibers. Motor fibers depart from the nucleus of the facial nerve located in the bridge. Secretory parasympathetic and sensory taste fibers are part of the intermediate nerve, which has parasympathetic and sensory nuclei in the bridge and exits the brain near the facial nerve.Both nerves (both facial and intermediate) follow into the internal auditory canal, in which the intermediate nerve enters the facial.After that, the facial nerve penetrates into the canal of the same name, located in the pyramid of the temporal bone.In the canal it gives off several branches: a large stony nerve, a tympanic string, etc. A large stony nerve contains secretory parasympathetic fibers to the lacrimal gland.The tympanic string passes through the tympanic cavity and, after leaving it, joins the lingual nerve from the third branch of the trigeminal nerve; it contains taste fibers for taste papillae of the body and tip of the tongue and secretory parasympathetic fibers in the submandibular and sublingual salivary glands.)

accessory nerve(according to the motor function, it consists of nerve fibers extending from the neurons of the motor nuclei. These nuclei are located in the medulla oblongata and in the cervical segment of the spinal cord. The nerve exits the skull through the jugular foramen to the neck and innervates the sternomastoidal and trapezius muscles.)

hypoglossal nerve(The nucleus of the hypoglossal nerve is motor, lies in the middle sections of the posterior part of the medulla oblongata. From the side of the rhomboid fossa, it is projected into the region of the triangle of the hypoglossal nerve. The nucleus of the hypoglossal nerve consists of large multipolar cells and a large number of fibers located between them, by which it is divided into three more or less isolated cell groups innervates the muscles of the tongue: the styloglossus, hyoidoglossus and genioglossus muscles, as well as the transverse and rectus muscles of the tongue.)

№36 Anatomy and physiology of mixed cranial nerves

Trigeminal nerve(It consists of three branches. Of these, the first two are sensitive, the third contains both sensory and motor fibers. On the basis of the brain, it is shown from the thickness of the pons varolii at the point of departure from the last middle cerebellar peduncle in two parts: sensory and motor roots.

Both parts are directed forward and somewhat laterally and penetrate into the gap between the sheets of the dura mater. Along the sensitive root, between its leaves, a trigeminal cavity is formed, located on the trigeminal impression of the top of the temporal bone pyramid. The cavity contains a relatively large (15 to 18 mm long) trigeminal ganglion, which is concave posteriorly and convex anteriorly. Three main branches of the trigeminal nerve depart from its anterior convex edge: ophthalmic, maxillary and mandibular nerves.

The motor root goes around the trigeminal node from the inside, goes to the foramen ovale, where it enters into the third branch of the trigeminal nerve. V pair - trigeminal nerve - innervates the masticatory muscles)

Glossopharyngeal(The glossopharyngeal nerve appears on the lower surface of the brain 4-6 roots behind the olive, below the vestibulocochlear nerve (VIII pair of cranial nerves). It goes outward and forward and exits the skull through the anterior part of the jugular foramen. In the region of the hole, the nerve thickens somewhat due to the superior ganglion located here). Having exited through the jugular foramen, the glossopharyngeal nerve thickens again due to the lower ganglion), which lies in a stony dimple on the lower surface of the temporal bone pyramid. IX pair - Provides: motor innervation of the stylo-pharyngeal muscle, raising the pharynx; innervation of the parotid gland; providing its secretory function; general sensitivity of the pharynx, tonsils, soft palate, Eustachian tube, tympanic cavity, taste sensitivity of the posterior third of the tongue.)

№37 Cerebellum, its structure and functions

Cerebellum lies under the occipital lobes of the cerebral hemispheres, separated from it by a horizontal fissure and located in the posterior cranial fossa.

The nuclei of the cerebellum developed in parallel with its development and are paired accumulations of gray matter, lying deep in the white, closer to the "worm". Distinguish:

* jagged;

* corky;

* spherical,

* the core of the tent.

Anterior to it is the bridge and the medulla oblongata.

Cerebellum consists of two hemispheres, in each of which the upper and lower surfaces are distinguished.

In addition, in the cerebellum there is a middle part - worm separating the hemispheres from each other.

Gray matter the cerebellar cortex, consisting of the bodies of neurons, is divided into lobules by deep furrows. Smaller furrows separate the leaves of the cerebellum from each other.

Cerebellar cortex branches and penetrates into the white matter, which is the body of the cerebellum, formed by processes of nerve cells.

white matter, branching, penetrates into the gyrus in the form of white plates.

The gray matter contains paired nuclei, lying deep in the cerebellum and forming the core of the tent, related to the vestibular apparatus. Lateral to the tent are the spherical and cork-shaped nuclei, which are responsible for the work of the muscles of the body, then the dentate nucleus, which controls the work of the limbs.

The cerebellum communicates with the periphery through other parts of the brain, with which it is connected by three pairs of legs.

- upper legs connect the cerebellum to the midbrain

- medium- with a bridge

- lower- with the medulla oblongata (spinal-cerebellar bundle of Flexic and bundles of Gaulle and Burdach)

Functions of the cerebellum

The main function of the cerebellum- coordination of movements, however, in addition, it performs some autonomic functions, taking part in managing the activity of autonomic organs and partly controlling skeletal muscles.

The cerebellum performs three main functions

1. coordination of movements

2. balance regulation

3. regulation of muscle tone

№38 Diencephalon, its structure and functions

The structure of the diencephalon. It consists of two parts - the thalamus and the hypothalamus. The hypothalamus performs the function of the highest organ of the autonomic system. Physiologically, it is associated with the pituitary gland, so it is discussed in the endocrine system section.

The structure of man assigned a very important function to the diencephalon. It cannot even be separated and specifically named - the diencephalon is involved in the regulation of almost all processes in the body.

The thalamic brain consists of three parts - the thalamus itself, the epithalamus and the metathalamus.

The thalamus occupies the most significant part of the diencephalon. It is a large accumulation of gray matter in the lateral walls on the sides of the diencephalon. The thalamus can be divided into two parts - the anterior end and the pad. This division is not accidental. The fact is that these two parts are functionally different parts - the small pillow is the visual center, and the front part is the center of the afferent (sensitive) pathways. The thalamus, through the so-called (part of the white matter), is very closely connected with the subcortical system, and, in particular, with the caudate nucleus.

Functions: Collection and evaluation of all incoming inf-and from org-s senses. Isolation and transmission to the cerebral cortex of the most important information. regulation of emotional behavior. The highest subcortical center of the vegetative NS and all vital fun-th org-ma. Ensuring the constancy of the internal environment and exchange processes-owls org-ma. Regulation of motivated behavior and defensive reactions (thirst. Hunger, satiety, fear, rage, non/pleasure) Participation in the change of sleep and wakefulness.

№39 Ascending pathways of the spinal cord, medulla oblongata, pons varolii and cerebral peduncles

The structure of the spinal cord

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 (cranially) directly passes into the medulla oblongata , and below (caudally) ends with a conical point, conus medullaris, at level II of the 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 , filum terminale, representing the atrophied lower part of the 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 roots of the nerves of the upper and lower extremities: the upper one is called cervical enlargement , intumescentia cervicalis, and the lower one - 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 passing along the midline 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: front - funiculus anterior, side - funiculus lateralis and rear - 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. front spine , radix ventral is s. anterior, exiting through sulcus anterolateralis, consists of neurites motor (centrifugal, or efferent) neurons, whose cell bodies lie in the spinal cord, while back spine , radix dorsalis s. posterior, included in sulcus posterolateralis, contains processes sensory (centripetal, or afferent) neurons whose bodies lie in the spinal nodes.

At some distance from the spinal cord, the motor root is adjacent to the sensory and together they form the trunk of the spinal nerve, truncus n. spinalis, which neuropathologists distinguish under the name of the funiculus, funiculus. Inflammation of the cord (funiculitis) causes segmental disorders of both 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 - spinal ganglion , ganglion spinale containing false unipolar nerve cells (afferent neurons) with one process, which is then divided into two branches: one of them, the central one, goes as part of the posterior root to 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 the autonomic nodes of the 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 latter, the nerve roots descend to the corresponding intervertebral foramens parallel to the filum terminate, enveloping it and the conus medullaris in a thick bundle, which is called ponytail , cauda equina.

White matter of the spinal cord, main parameters and functions. Spinal Cord Functions Interesting White Matter Facts

The spinal cord (medulla spinalis) is located in the spinal canal. At the level of the I cervical vertebra and the occipital bone, the spinal cord passes into the oblong, and downwards stretches to the level of the I-II lumbar vertebra, where it becomes thinner and turns into a thin terminal thread. The spinal cord is 40–45 cm long and 1 cm thick. The spinal cord has cervical and lumbosacral thickenings, where nerve cells are located that provide innervation to the upper and lower extremities.

The spinal cord consists of 31–32 segments. A segment is a section of the spinal cord that contains one pair of spinal roots (anterior and posterior).

The anterior root of the spinal cord contains motor fibers, the posterior root contains sensory fibers. Connecting in the region of the intervertebral node, they form a mixed spinal nerve.

The spinal cord is divided into five parts:

cervical (8 segments);

Thoracic (12 segments);

Lumbar (5 segments);

sacral (5 segments);

Coccygeal (1-2 rudimentary segments).

The spinal cord is somewhat shorter than the spinal canal. In this regard, in the upper parts of the spinal cord, its roots run horizontally. Then, starting from the thoracic region, they descend somewhat downward before exiting the corresponding intervertebral foramina. In the lower sections, the roots go straight down, forming the so-called ponytail.

Anterior median fissure, posterior median sulcus, symmetrically located anterior and posterior lateral sulci are visible on the surface of the spinal cord. Between the anterior median fissure and the anterior lateral sulcus is the anterior funiculus (funiculus anterior), between the anterior and posterior lateral sulci is the lateral cord (funiculus lateralis), between the posterior lateral sulcus and the posterior median sulcus is the posterior cord (funiculus posterior), which is in the cervical part the spinal cord is divided by a shallow intermediate groove into a thin bundle (fasciculus gracilis). adjacent to the posterior median sulcus, and located outward from it, a wedge-shaped bundle (fasciculus cuneatus). The cords contain pathways.

The anterior roots emerge from the anterior lateral sulcus, and the posterior roots enter the spinal cord in the region of the posterior lateral sulcus.

On a transverse section in the spinal cord, gray matter is clearly distinguished, located in the central parts of the spinal cord, and white matter, lying on its periphery. The gray matter in the transverse section resembles a butterfly with open wings or the letter "H" in shape. In the gray matter of the spinal cord, more massive ones are isolated. wide and short anterior horns and thinner, elongated posterior horns. In the thoracic regions, a lateral horn is revealed, which is also less pronounced in the lumbar and cervical regions of the spinal cord. The right and left halves of the spinal cord are symmetrical and connected by spikes of gray and white matter. Anterior to the central canal is the anterior gray commissure (comissura grisea anterior), then the anterior white commissure (comissura alba anterior); posterior to the central canal are the posterior gray commissure and the posterior white commissure in succession.

In the anterior horns of the spinal cord, large motor nerve cells are localized, the axons of which go to the anterior roots and innervate the striated muscles of the neck, trunk and limbs. The motor cells of the anterior horns are the final authority in the implementation of any motor act, and also have trophic effects on the striated muscles.

Primary sensory cells are located in the spinal (intervertebral) nodes. Such a nerve cell has one process, which, moving away from it, is divided into two branches. One of them goes to the periphery, where it receives irritation from the skin, muscles, tendons or internal organs. and on the other branch, these impulses are transmitted to the spinal cord. Depending on the type of irritation and, therefore, the pathway along which it is transmitted, the fibers entering the spinal cord through the posterior root may terminate on the cells of the posterior or lateral horns, or pass directly into the white matter of the spinal cord. Thus, the cells of the anterior horns perform motor functions, the cells of the posterior horns perform the function of sensitivity, and the spinal vegetative centers are localized in the lateral horns.

The white matter of the spinal cord consists of fibers of pathways that interconnect both different levels of the spinal cord with each other, and all overlying parts of the central nervous system with the spinal cord.

In the anterior cords of the spinal cord, there are mainly pathways involved in the implementation of motor functions:

1) anterior cortical-spinal (pyramidal) path (non-crossed) going mainly from the motor area of the cerebral cortex and ending on the cells of the anterior horns;

2) pre-door-spinal (vestibulospinal) path, coming from the lateral vestibular nucleus of the same side and ending on the cells of the anterior horns;

3) the occlusal-spinal tract, starting in the upper colliculus of the quadrigemina of the opposite side and ending on the cells of the anterior horns;

4) the anterior reticular-spinal tract, coming from the cells of the reticular formation of the brain stem of the same side and ending on the cells of the anterior horn.

In addition, near the gray matter there are fibers that connect different segments of the spinal cord with each other.

Both motor and sensory pathways are located in the lateral cords of the spinal cord. Movement paths include:

Lateral cortical-spinal (pyramidal) path (crossed) going mainly from the motor area of the cerebral cortex and ending on the cells of the anterior horns of the opposite side;

The spinal tract, coming from the red nucleus and ending on the cells of the anterior horns of the opposite side;

Reticular-spinal tracts, coming mainly from the giant cell nucleus of the reticular formation of the opposite side and ending on the cells of the anterior horns;

Olivospinal tract, connecting the lower olives with the motor neuron of the anterior horn.

The afferent, ascending conductors include the following paths of the lateral cord:

1) posterior (dorsal uncrossed) dorsal-cerebellar path, coming from the cells of the posterior horn and ending in the cortex of the superior cerebellar vermis;

2) anterior (crossed) dorsal-cerebellar path, coming from the cells of the posterior horns and ending in the cerebellar vermis;

3) the lateral dorsal-thalamic pathway, coming from the cells of the posterior horns and ending in the thalamus.

In addition, in the lateral funiculus, the dorsal-cover way, dorsal-reticular way, spinal-olive way and some other conductor systems pass.

In the posterior funiculi of the spinal cord are afferent thin and wedge-shaped bundles. The fibers included in them begin in the intervertebral nodes and end, respectively, in the nuclei of the thin and wedge-shaped bundles located in the lower part of the medulla oblongata.

Thus, part of the reflex arcs is closed in the spinal cord and the excitation coming through the fibers of the posterior roots is subjected to a certain analysis, and then transmitted to the cells of the anterior horn; the spinal cord transmits impulses to all overlying parts of the central nervous system up to the cerebral cortex.

The reflex can be carried out in the presence of three consecutive links: 1) the afferent part, which includes receptors and pathways that transmit excitation to the nerve centers; 2) the central part of the reflex arc, where the analysis and synthesis of incoming stimuli take place and a response to them is developed; 3) the effector part of the reflex arc, where the response occurs through the skeletal muscles, smooth muscles and glands. The spinal cord, therefore, is one of the first stages at which the analysis and synthesis of stimuli are carried out both from the internal organs and from the receptors of the skin and muscles.

The spinal cord carries out trophic influences, i.e. damage to the nerve cells of the anterior horns leads to a violation of not only movements, but also the trophism of the corresponding muscles, which leads to their degeneration.

One of the important functions of the spinal cord is the regulation of the activity of the pelvic organs. The defeat of the spinal centers of these organs or the corresponding roots and nerves leads to persistent disorders of urination and defecation.

All systems and organs in the human body are interconnected. And all functions are controlled by two centers: . Today we will talk about, and the white education contained in it. The white matter of the spinal cord (substantia alba) is a complex system of non-myelinated nerve fibers of varying thickness and length. This system includes both supporting nervous tissue and blood vessels surrounded by connective tissue.

What is white matter made of? There are many processes of nerve cells in the substance, they make up the pathways of the spinal cord:

descending bundles (efferent, motor), they go to the cells of the anterior horns of the human spinal cord from the brain.
ascending (afferent, sensory) bundles that go to the cerebellum and centers of the brain.
short bundles of fibers that connect segments of the spinal cord, they are present at various levels of the spinal cord.

Basic parameters of white matter

The spinal cord is a special substance located inside the bone tissue. This important system is located in the human spine. In a section, the structural unit resembles a butterfly, white and gray matter is evenly distributed in it. Inside the spinal cord, a white substance is covered with sulfur, which forms the center of the structure.

The white matter is divided into segments, the lateral, anterior and posterior sulci serve as separators. They form spinal cords:

The lateral cord is located between the anterior and posterior horns of the spinal cord. It contains descending and ascending paths.
The posterior funiculus is located between the anterior and posterior horn of the gray matter. Contain wedge-shaped, tender, ascending bundles. They are divided among themselves, the rear intermediate furrows serve as separators. The wedge-shaped bundle is responsible for conducting impulses from the upper limbs. A gentle beam transmits impulses from the lower extremities to the brain.
The anterior cord of the white matter is located between the anterior fissure and the anterior horn of the gray matter. It contains descending pathways, through which the signal goes from the cortex, as well as from the midbrain to important human systems.

The structure of the white matter is a complex system of fleshy fibers of different thicknesses; together with the supporting tissue, it is called neuroglia. It contains small blood vessels that have almost no connective tissue. The two halves of the white matter are interconnected by adhesions. A white spike also goes in the region of the transversely stretching spinal canal, located in front of the central one. The fibers are connected into bundles that conduct nerve impulses.

Major ascending pathways

The task of the ascending pathways is the transmission of impulses from peripheral nerves to the brain, most often to the cortical and cerebellar regions of the central nervous system. There are ascending paths too soldered together, they cannot be regarded separately from each other. Let's single out six soldered and independent ascending beams of white matter.

The wedge-shaped bundle of Burdach and the thin bundle of Gaulle (in Figure 1.2). The bundles are made up of spinal ganglion cells. The wedge-shaped bundle is the 12 upper segments, the thin bundle is the 19 lower ones. The fibers of these bundles go to the spinal cord, pass through the posterior roots, providing access to special neurons. They, in turn, go to the nuclei of the same name.
Lateral and ventral routes. They consist of sensitive cells of the spinal ganglia extending to the posterior horns.
Spinal cerebellar pathway of Gowers. It contains special neurons, they go to the area of Clark's nucleus. They rise to the upper parts of the trunk of the nervous system, where they enter the ipsilateral half of the cerebellum through the upper legs.
Spinal cerebellar flexing pathway. At the very beginning of the path contains neurons of the spinal nodes, then the path goes to the cells of the nucleus in the intermediate zone of gray matter. Neurons pass through the inferior cerebellar peduncle and reach the longitudinal brain.

Main descending pathways

The descending tracts are connected with the ganglia and the gray matter area. Nerve impulses are transmitted through bundles, they come from the human nervous system and are sent to the periphery. These pathways are not yet well understood. They are often intertwined with each other, forming monolithic structures. Some paths cannot be considered without separation:

Lateral and ventral corticospinal tracts. They start from the pyramidal neurons of the motor cortex in their lower part. Then the fibers pass through the base of the midbrain, the cerebral hemispheres, pass through the ventral parts of the Varoliyev, the medulla oblongata, reaching the spinal cord.
Vestibulospinal pathways. This concept is generalizing, it includes several types of bundles formed from the vestibular nuclei, which are located in the medulla oblongata. They end in the anterior cells of the anterior horns.
Tectospinal path. It rises from the cells in the region of the quadrigemina of the midbrain, ends in the region of the mononeurons of the anterior horns.
Rubrospinal path. It originates from cells located in the region of the red nuclei of the nervous system, crosses in the region of the midbrain, and ends in the region of the neurons of the intermediate zone.
reticulospinal route. This is the link between the reticular formation and the spinal cord.
Olivospinal path. Formed by neurons of olive cells located in the longitudinal brain, it ends in the region of mononeurons.

We examined the main ways that are more or less studied by scientists at the moment. It is worth noting that there are also local bundles that perform a conductive function, which also connect various segments of different levels of the spinal cord.

The role of the white matter of the spinal cord

The connective system of the white matter acts as a conductor in the spinal cord. There is no contact between the gray matter of the spinal cord and the main brain, they do not contact each other, do not transmit impulses to each other and affect the functioning of the body. These are all functions of the white matter of the spinal cord. The body, due to the connecting capabilities of the spinal cord, works as an integral mechanism. The transmission of nerve impulses and information flows occurs according to a certain scheme:

Impulses sent by the gray matter pass through thin threads of white matter that connect to different parts of the main human nervous system.
Signals activate the right parts of the brain, moving at lightning speed.
Information is quickly processed in our own centers.
The informational response is immediately sent back to the center of the spinal cord. For this, strings of white substance are used. From the center of the spinal cord, signals diverge to different parts of the human body.

This is all a rather complex structure, but the processes are actually instantaneous, a person can lower or raise his hand, feel pain, sit down or stand up.

Communication between white matter and brain regions

The brain includes several areas. The human skull contains the oblong, final, middle, diencephalon and cerebellum. The white matter of the spinal cord is in good contact with these structures, it can establish contact with a specific section of the spine. When there are signals associated with speech development, motor and reflex activity, taste, auditory, visual sensations, speech development, the white matter of the telencephalon is activated. The white substance of the medulla oblongata is responsible for the conductive and reflex function, activating the complex and simple functions of the whole organism.

The gray and white matter of the midbrain, which interact with spinal connections, take responsibility for various processes in the human body. The white matter of the midbrain has the ability to enter into the active phase the processes:

Activation of reflexes due to sound exposure.
Regulation of muscle tone.
Regulation of the centers of auditory activity.
Performing installation and rectifying reflexes.

In order for information to quickly reach the central nervous system through the spinal cord, its path lies through the diencephalon, so the work of the body is more coordinated and accurate.

More than 13 million neurons are contained in the gray matter of the spinal cord; they make up entire centers. From these centers, signals are sent to the white matter every fraction of a second, and from it to the main brain. It is thanks to this that a person can live a full life: smell, distinguish sounds, relax and move.

Information moves along the descending and ascending paths of white matter. Ascending pathways move information that is encrypted in nerve impulses to the cerebellum and large centers of the main brain. The processed data is returned in descending directions.

Risk of injury to spinal cord pathways

White matter is under three membranes, they protect the entire spinal cord from damage. It is also protected by a solid frame of the spine. But there is still a risk of injury. The possibility of an infectious lesion cannot be ignored, although these are not frequent cases in medical practice. Spinal injuries are more common, in which the white matter is primarily affected.

Functional dysfunction can be reversible, partially reversible, and have irreversible consequences. It all depends on the nature of the damage or injury.

Any injury can lead to the loss of the most important functions of the human body. With the appearance of an extensive gap, damage to the spinal cord, irreversible consequences appear, the conduction function is disturbed. With a bruise of the spine, when the spinal cord is compressed, damage occurs to the connections between the nerve cells of the white matter. The consequences may vary depending on the nature of the injury.

Sometimes certain fibers are torn, but the possibility of restoration and healing of nerve impulses remains. This may take a considerable time, because the nerve fibers grow together very poorly, namely, the possibility of conducting nerve impulses depends on their integrity. The conductivity of electrical impulses can be partially restored with some damage, then the sensitivity will be restored, but not completely.

The probability of recovery is affected not only by the degree of injury, but also by how professionally first aid was provided, how resuscitation and rehabilitation were carried out. After all, after damage, it is necessary to teach the nerve endings to re-conduct electrical impulses. Also, the recovery process is affected by: age, the presence of chronic diseases, metabolic rate.

Interesting White Matter Facts

The spinal cord is fraught with many mysteries, so scientists around the world are constantly conducting research, studying it.

The spinal cord actively develops and grows from birth until the age of five to reach a size of 45 cm.
The older the person, the more white matter in his spinal cord. It replaces dead nerve cells.
Evolutionary changes in the spinal cord occurred earlier than in the brain.
Only in the spinal cord are the nerve centers responsible for sexual arousal.
It is believed that music contributes to the proper development of the spinal cord.
Interestingly, the white matter is actually a beige hue.

I. Dorsal (posterior) cords. These ascending (afferent) pathways are formed by axon collaterals of sensory neurons of the spinal ganglia. There are two bundles:

· Thin (gentle) bundle (Gaul's bundle). It starts from the lower segments of the spinal cord, is located more medially. Carries information from the receptors of the musculoskeletal system and tactile receptors of the skin of the lower extremities and the lower half of the body.

· Wedge-shaped bundle (Bundach's bundle). Appears at the level of 11-12 thoracic segments. Located more laterally. Carries information from the same receptors in the upper half of the body and upper limbs.

II. Lateral (lateral cords). There are ascending and descending paths:

· Ascending pathways (afferent, sensory):

Ø Spinal tract(Gowers path) (these are the axons of the interneurons of the posterior horns). Transmit signals from musculoskeletal receptors and skin tactile receptors to the cerebellum.

Ø Spinal thalamic tract. The axons of the interneurons of the posterior horns transmit signals from pain receptors, thermoreceptors, skin, as well as from all receptors of internal organs (transmit to the thalamus and further to the cerebral cortex (our sensations))

· Descending (efferent) paths (motor tracts):

Ø Rubrospinal tract- axons of neurons of the red nucleus (Nucleus ruber) of the midbrain, which are directed to the interneurons of the intermediate zone. Features: about nor control the flexor muscles.

Ø Corticospinal (pyramidal) tract. There is a motor zone in the cortex (in the frontal lobe). These are the axons of the pyramidal neurons of the motor (motor) zone of the cerebral cortex, which pass through the entire brain stem to the interneurons to the intermediate zone of the spinal cord. In humans, 8% of the fibers of this tract terminate directly on the motor neurons of the anterior horns. Path function: voluntary regulation of fine and precise movements, mainly of the limbs.

III. Ventral (anterior) cords. There are ascending and descending paths.

· Downstream paths:

Ø Vestibulo-spinal tract. These are the axons of the neurons of the vestibular nuclei of the brainstem, which terminate in the neurons of the anterior horns. Functions: to control limb extension.

Ø Reticulospinal tract. These are the axons of the neurons of the reticular nuclei of the trunk, which terminate in the interneurons of the intermediate zone. Functions: control the movement of the body and provide the launch of locomotion (rhythmic movements, for example, running).

The general principle of the brain:

Reflex arc. The activity of the nervous system is carried out according to the reflex principle. Reflex - the body's response to a stimulus, carried out with the participation and under the control of the nervous system. RD - this is a chain of neurons along which signals pass during the implementation of the reflex. Protozoa RD consists of two neurons, between which the synapse is called a two-neuron RD or monosynaptic RD. Such RD not much in the body.

There are always 5 functional links in the reflex arc:

1. Receptor- a specialized cell that perceives the stimulus and transforms it into a nervous process.