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 tract

(conducts pain, temperature and partially tactile sensitivity)

* medial loop

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

*bulbo-thalamic tract

(conductor of articular-muscular, tatkil, vibration sensitivity, sense of pressure, weight. Proprioceptors are located in muscles, joints, ligaments, etc.)

* trigeminal loop

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

*lateral loop

(auditory tract of the brain stem. Ends in the internal geniculate body and posterior colliculus)
* spinocerebellar tracts
(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 capable of performing complex motor and autonomic reflexes. It is connected by afferent - sensitive - pathways to receptors, and by efferent pathways - to skeletal muscles and all internal organs. The spinal cord connects the periphery with the brain through long ascending and descending tracts. Afferent impulses along the spinal cord pathways are carried to the brain, carrying information about changes in the external and internal environment of the body. Along descending pathways, impulses from the brain are transmitted to 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 to receptors and working organs. In addition to the spinal cord, such centers are present in the medulla oblongata and midbrain. The suprasegmental centers do not have a direct connection with the periphery. They control it through segmental centers. 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, the spinal cord contains a number of sympathetic and parasympathetic autonomic centers. 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. This is where the neurons directly connected to the peripheral sympathetic ganglia lie. In the upper thoracic segment, there is a sympathetic center for pupil dilation, in the five upper thoracic segments there are sympathetic cardiac centers. The sacral part of the spinal cord contains parasympathetic centers that innervate 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 legs on the side where the back roots are cut will lose sensitivity, and on the opposite side, where the front roots are cut, they will be paralyzed. Consequently, the dorsal roots of the spinal cord are sensitive, and the anterior ones 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.

Conducting function of the spinal cord. The spinal cord performs a conductive function due to the ascending and descending tracts 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 basic pattern of distribution of motor and sensory fibers in the nerve roots of the spinal cord. B. - M. z. established in 1822 by the French physiologist F. Magendie. It was partially based on the observations of the English anatomist and physiologist Charles 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 dorsal roots. Centrifugal nerve fibers also exit through the anterior roots, innervating smooth muscles, vessels and glands.

No. 31 Segmental and intersegmental principles 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 becomes 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 fusiform 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 there is a 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 conus medullaris, from which a long thin terminal filament extends.

Segmental and intersegmental principles of operation 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 arise from each spinal segment. 1 sensory and 1 motor root innervates its transverse layer of the body, i.e. metamer. This is the segmental principle of the spinal cord. The intersegment operating principle is in the innervation of the sensory and motor roots of its metamere, the 1st overlying and 1st underlying metamer. Knowledge of the boundaries of body metameres makes it possible to carry out topical diagnosis of spinal cord diseases. 3. Conductive organization of the spinal cord Axons of the spinal ganglia and gray matter of the spinal cord go into its white matter, and then into other structures of the central nervous system, thereby creating the so-called conducting pathways, functionally divided into proprioceptive, spinocerebral (ascending) and cerebrospinal (descending). Propriospinal tracts connect neurons of the same or different segments of the spinal cord. The function of such connections is associative and consists in coordinating posture, muscle tone, and movements of various metameres of the body.

No. 33 Physiological characteristics of 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, and neck.

Motor nerves begin in the motor nuclei of the brainstem. The predominantly motor nerves include the group of oculomotor nerves: oculomotor (3rd), trochlear (4th), abducens (6th), as well as 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, sublingual (12th), innervating the muscles of the tongue.

Sensitive ones are formed from the fibers of those neurons whose bodies lie in the cranial ganglia outside the brain. The sensitive ones include the olfactory (1st), visual (2nd), pre-cochlear, or auditory (8th), which respectively provide 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 muscle function. pharynx and larynx. The vagus also provides parasympathetic innervation of internal organs.

Cranial nerves are designated by Roman numerals in the order in which they are located:

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 is 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 rhombencephalon and is a direct continuation of the spinal cord. The medulla oblongata is divided into several parts by the same grooves as the spinal cord. On the sides of one of them (anterior median sulcus) are the so-called pyramids of the medulla (it turns out that the anterior cords of the spinal cord continue into these pyramids).

Nerve fibers intersect in these pyramids. On the posterior side of the medulla oblongata there is a posterior median sulcus, on either side of which lie the posterior cords of the medulla oblongata. In these posterior cords of the medulla oblongata there are continuations of the sensitive thin and cuneate fasciculi. Three pairs of cranial nerves emerge from the medulla oblongata - pairs IX, X, XI, which are respectively called - glossopharyngeal nerve, vagus nerve, accessory nerve. The medulla oblongata also 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 gray matter nuclei:

1. The olive kernel is an intermediate center of balance.

2. The reticular formation is a network of nerve fibers and their processes, running throughout the entire brain, interconnecting and coordinating the action 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 there are fibers: long and short. The short ones connect the various structures of the medulla oblongata itself, and the long ones connect the medulla oblongata with other structures of the central nervous system.

Bridge - the ventral part of the hindbrain, represents a massive protrusion on the ventral surface of the brain stem (hindbrain).

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

* Laterally, the pons continues into the massive middle cerebellar peduncle, which extends to the cerebellum. At the border with the bridge, the trigeminal nerve (V) emerges from the pedicle. On the ventral surface of the pons 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 through the base of the bridge.

The dorsal part of the pons is located dorsal to the trapezoid body and contains 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. This section contains centers that control the activity of the facial and chewing muscles and one of the oculomotor muscles. The pons receives nerve impulses from receptors of the sensory organs located on the head: from the tongue (taste sensitivity), inner ear (auditory sensitivity and balance) and skin.

№34 Anatomy and physiology of sensory cranial nerves

Cranial nerves are peripheral nerves that originate from parts of the brain, and the nuclei of these nerves are located in the brain stem (midbrain, pons and cerebellum).

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

Sensory:

Olfactory nerve(The olfactory nerves are sensitive in function and consist of nerve fibers that are processes of the olfactory cells of the olfactory organ. These fibers form 15-20 olfactory filaments (nerves), which exit the olfactory organ and, through the cribriform plate of the reticular bone, enter the cranial cavity, where they approach To the 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 and consists of nerve fibers that are processes of the so-called glanglionic 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 decussation with the nerve of the opposite side (optic chiasm) and lasts for optic 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 visual tracts approach the subcortical visual centers - the nuclei of the upper colliculi of the midbrain roof, lateral geniculate bodies and thalamic cushions. The nuclei of the superior colliculus are connected to the nuclei of the oculomotor nerve (through which the pupillary reflex is carried out) and to the nuclei of the anterior horns of the spinal cord (orienting reflexes to sudden light stimulation are carried out). From the nuclei of the lateral geniculate bodies and pillows of the thalamus, nerve fibers in the white matter of the hemispheres follow to the cortex of the occipital lobes (visual sensory area of the cortex).)

Spatiocochlear(a nerve of special sensitivity, consisting of two roots with different functions: the vestibular root, which carries impulses from the static apparatus, represented by the semicircular ducts of the vestibular labyrinth and the cochlear root, which carries auditory impulses from the spiral organ of the cochlear labyrinth. VIII pair - the vestibular-cochlear 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(motor in function, 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 accessory parasympathetic nucleus. They are located in the cerebral peduncle at the level of the superior colliculi of the roof of the midbrain. The nerve exits the cavity 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 (all of them are striated) , and the parasympathetic fibers are the constrictor pupillary muscle and the ciliary muscle (both smooth). Parasympathetic fibers on the way to the muscles switch in the ciliary ganglion, which lies in the posterior part of the orbit.)

Trochlear nerve(functionally motor, consists of nerve fibers extending from the nucleus. The nucleus is located in the cerebral peduncles at the level of the lower colliculi of the roof of the midbrain. The nerves exit the cranial cavity through the superior orbital fissure into the orbit and innervate 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 pons. 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 sensitive taste fibers. Motor fibers arise from the nucleus of the facial nerve located in the bridge. Secretory parasympathetic and sensitive taste fibers are part of the intermediate nerve, which has parasympathetic and sensory nuclei in the bridge and leaves the brain next to the facial nerve. Both nerves (the facial and the intermediate) follow into the internal auditory canal, in which the intermediate nerve exits into the facial nerve. After this, the facial nerve penetrates the canal of the same name, located in the pyramid of the temporal bone. In the canal it gives off several branches: the greater petrosal nerve, the chorda tympani, etc. The greater petrosal nerve contains secretory parasympathetic fibers to the lacrimal gland. The chorda tympani 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 the taste buds of the body and the tip of the tongue and secretory parasympathetic fibers in the submandibular and sublingual salivary glands.)

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

Hypoglossal nerve(The nucleus of the hypoglossal nerve is motor, lies in the middle parts 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, with which it is divided into three more or less isolated cell groups. Innervates the muscles of the tongue: styloglossus, hyoglossus 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. At the base of the brain, it appears from the thickness of the pons at the place where the middle cerebellar peduncle originates from the last in two parts: the sensory and motor roots.

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

The motor root goes around the trigeminal ganglion from the inside, goes to the foramen ovale, where it joins 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 with 4-6 roots behind the olive, below the vestibular-cochlear nerve (VIII pair of cranial nerves). It is directed outward and forward and leaves the skull through the anterior part of the jugular foramen. In the area of the foramen, the nerve thickens somewhat due to superior ganglion located here). Having emerged through the jugular foramen, the glossopharyngeal nerve thickens for the second time due to the inferior ganglion), which lies in the stony fossa on the lower surface of the pyramid of the temporal bone. IX pair - Provides: motor innervation of the stylopharyngeal muscle, levator 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.)

No. 37 The 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 cerebellar nuclei developed in parallel with its development and represent paired accumulations of gray matter, located in the depths of the white matter, closer to the “worm”. There are:

* jagged;

* corky;

* spherical,

* the core of the tent.

Anterior to it is the pons and the medulla oblongata.

Cerebellum consists of two hemispheres, each of which has an upper and lower surface.

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

Gray matter The cerebellar cortex, consisting of neuron bodies, is divided into lobules by deep grooves. Smaller grooves separate the layers of the cerebellum from each other.

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

White matter, branching out, penetrates the convolutions 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 connects the cerebellum to the midbrain

- average- with 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 to this, it performs some autonomic functions, taking part in managing the activity of autonomic organs and partly controlling skeletal muscles.

The cerebellum has three main functions

1. coordination of movements

2. balance regulation

3. regulation of muscle tone

No. 38 Diencephalon, its structure and functions

Structure of the diencephalon. It consists of two parts - the thalamus and hypothalamus. The hypothalamus serves as 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 human structure has 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 each side 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 pad is the visual center, and the anterior part is the center of the afferent (sensory) 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 information from sense organizations. Isolation and transmission of the most important information to the cerebral cortex. Regulation of emotional behavior. The highest subcortical center of the autonomic nervous system and all vital functions of the org. Ensuring the constancy of the internal environment and metabolic processes of the organization. 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

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 in 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 filament , 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 length has two thickenings corresponding to the nerve roots of the upper and lower extremities: the upper one is called cervical thickening , intumescentia cervicalis, and the lower - 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. Anterior root , radix ventral is s. anterior, exiting through the sulcus anterolateralis, consists of neurites motor (centrifugal, or efferent) neurons, whose cell bodies lie in the spinal cord, while dorsal root , radix dorsalis s. posterior, part of the sulcus posterolateralis, contains processes sensitive (centripetal, or afferent) neurons, whose bodies lie in the spinal ganglia.

At some distance from the spinal cord, the motor root is adjacent to the sensory and they together form the trunk of the spinal nerve, truncus n. spinalis, which neurologists distinguish under the name cord, 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 Facts About White Matter

The spinal cord (medulla spinalis) is located in the spinal canal. At the level of the 1st cervical vertebra and occipital bone, the spinal cord passes into the medulla oblongata, and extends downwards to the level of the 1st–2nd lumbar vertebrae, where it thins out and turns into a thin filament terminale. The length of the spinal cord is 40–45 cm, thickness 1 cm. The spinal cord has cervical and lumbosacral thickenings, where the nerve cells that provide innervation to the upper and lower extremities are localized.

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 area 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 slightly 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 downwards before emerging from the corresponding intervertebral foramina. In the lower sections, the roots go straight down, forming the so-called ponytail.

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

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

In a cross-section of the spinal cord, the gray matter located in the central parts of the spinal cord and the white matter lying on its periphery are clearly distinguished. Gray matter in a cross section resembles the shape of a butterfly with open wings or the letter “H”. In the gray matter of the spinal cord, more massive ones are distinguished. wide and short anterior horns and thinner, elongated posterior horns. In the thoracic regions, a lateral horn is detected, 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 commissures of gray and white matter. Anterior to the central canal is the anterior gray commissure (comissura grisea anterior), followed by the anterior white commissure (comissura alba anterior); posterior to the central canal, the posterior gray commissure and the posterior white commissure are located successively.

Large motor nerve cells are localized in the anterior horns of the spinal cord, 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 along another 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 dorsal root may end on the cells of the dorsal or lateral horns or directly pass into the white matter of the spinal cord. Thus, the cells of the anterior horns carry out motor functions, the cells of the posterior horns carry out the sensitivity function, and the spinal vegetative centers are localized in the lateral horns.

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

The anterior cords of the spinal cord contain mainly pathways involved in motor functions:

1) anterior corticospinal (pyramidal) tract (uncrossed) coming mainly from the motor area of the cerebral cortex and ending on the cells of the anterior horns;

2) vestibulospinal tract, coming from the lateral vestibular nucleus of the same side and ending on the cells of the anterior horns;

3) tegmental-spinal tract, starting in the upper colliculi of the quadrigeminal tract 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.

The lateral cords of the spinal cord contain both motor and sensory PATHWAYS. Motor pathways include:

Lateral corticospinal (pyramidal) tract (crossed) coming 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 cord tracts, coming predominantly from the giant cell nucleus of the reticular formation of the opposite side and ending on the cells of the anterior horns;

The olivospinal tract connects the inferior olive to the motor neuron of the anterior horn.

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

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

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

3) the lateral spinothalamic tract, coming from the cells of the dorsal horns and ending in the thalamus.

In addition, the dorsal tegmental tract, spinal reticular tract, spino-olive tract and some other conduction systems pass through the lateral cord.

The afferent thin and cuneate fasciculi are located in the posterior cords of the spinal cord. The fibers included in them begin in the intervertebral nodes and end, respectively, in the nuclei of the thin and wedge-shaped fasciculi, 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 dorsal 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 successive 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 occurs and a response to them is developed; 3) the effector part of the reflex arc, where the response is carried out through skeletal muscles, smooth muscles and glands. The spinal cord is thus one of the first stages at which the analysis and synthesis of stimuli both from internal organs and from receptors of the skin and muscles are carried out.

The spinal cord carries out trophic influences, i.e. damage to the nerve cells of the anterior horns leads to disruption 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. Damage to the spinal centers of these organs or the corresponding roots and nerves leads to persistent disturbances in 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 unmyelinated 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? The substance contains many processes of nerve cells; they make up the conductive tracts 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 cerebral centers.
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 cross-section, the structural unit resembles a butterfly; the white and gray matter in it are evenly distributed. Inside the spinal cord, a white substance is covered with sulfur and forms the center of the structure.

The white matter is divided into segments, separated by the lateral, anterior and posterior grooves. They form the spinal cords:

The lateral cord is located between the anterior and posterior horn 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. Contains wedge-shaped, delicate, ascending tufts. They are separated from each other, the posterior intermediate grooves serve as separators. The wedge-shaped fasciculus is responsible for conducting impulses from the upper limbs. A gentle bundle transmits impulses from the lower extremities to the brain.
The anterior cord of white matter is located between the anterior fissure and the anterior horn of 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 pulpy 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. The white commissure also extends in the region of the transversely extending spinal canal, located in front of the central canal. The fibers are connected into bundles that conduct nerve impulses.

Main ascending paths

The task of the ascending pathways is to transmit impulses from peripheral nerves to the brain, most often to the cortical and cerebellar regions of the central nervous system. There are ascending paths that are too welded together; they cannot be assessed 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 into the spinal cord, pass through the dorsal roots, providing access to special neurons. They, in turn, go to the nuclei of the same name.
Lateral and ventral pathways. They consist of sensory cells of the spinal ganglia extending to the dorsal horns.
Govers' spinocerebellar tract. It contains special neurons, they go to the Clarke nucleus area. They rise to the upper parts of the nervous system trunk, where, through the upper legs, they enter the ipsilateral half of the cerebellum.
Flexing's spinocerebellar tract. At the very beginning of the path, the neurons of the spinal ganglia are contained, then the path goes to the nuclear cells in the intermediate zone of the gray matter. Neurons pass through the inferior cerebellar peduncle and reach the longitudinal medulla.

Main descending paths

Descending pathways are associated with ganglia and the gray matter region. Nerve impulses are transmitted through bundles, they come from the human nervous system and are sent to the periphery. These pathways have not yet been sufficiently studied. They often intertwine with each other, forming monolithic structures. Some paths cannot be considered without separation:

Lateral and ventral corticospinal tracts. They begin 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 sections of the Varoliev, medulla oblongata, reaching the spinal cord.
Vestibulospinal tracts. This is a general concept; 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 tract. It ascends from cells in the quadrigeminal region of the midbrain and ends in the region of the mononeurons of the anterior horns.
Rubrospinal tract. It originates from cells that are located in the region of the red nuclei of the nervous system, intersects in the region of the midbrain, and ends in the region of the neurons of the intermediate zone.
Reticulospinal tract. This is the connecting link between the reticular formation and the spinal cord.
Olive spinal tract. Formed by neurons of olivary cells located in the longitudinal brain, it ends in the region of mononeurons.

We looked at the main ways that have been 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 different segments of different levels of the spinal cord.

The role of white matter of the spinal cord

The white matter connective system 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 pattern:

Impulses sent by gray matter travel along thin threads of white matter that connect to different parts of the main human nervous system.
The signals activate the right parts of the brain, moving at lightning speed.
Information is quickly processed in our own centers.
The information response is immediately sent back to the center of the spinal cord. For this purpose, 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.

Connection between white matter and brain regions

The brain includes several zones. The human skull contains the medulla oblongata, telencephalon, midbrain, diencephalon and cerebellum. The white matter of the spinal cord is in good contact with these structures; it can establish contact with a specific part 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 conduction and reflex function, activating complex and simple functions of the whole organism.

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

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

In order for information to quickly travel through the spinal cord to the central nervous system, its path lies through the diencephalon, so the body’s work 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, rest and move.

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

Risk of damage to the spinal cord tracts

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

Functional impairment may be reversible, partially reversible, or 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. When an extensive rupture or damage to the spinal cord occurs, irreversible consequences appear and the conduction function is disrupted. When a spinal bruise occurs, 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 considerable time, because nerve fibers grow together very poorly, and the possibility of conducting nerve impulses depends on their integrity. The conductivity of electrical impulses can be partially restored with some damage, then sensitivity will be restored, but not completely.

The likelihood 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 conduct electrical impulses again. The recovery process is also affected by age, the presence of chronic diseases, and metabolic rate.

Interesting facts about white matter

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

The spinal cord actively develops and grows from birth until the age of five to reach a size of 45 cm.
The older a person is, the more white matter there is 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 promotes the proper development of the spinal cord.
Interesting, but in fact the white substance is beige in color.

I. Dorsal (posterior) cords. These are ascending (afferent) pathways formed by collaterals of the axons 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 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 Spinocerebellar tract(Gowers Path) (these are axons of interneurons of the dorsal horns). They transmit signals from the receptors of the musculoskeletal system and tactile receptors of the skin to the cerebellum.

Ø Spinothalamic tract. Axons of interneurons of the dorsal 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) pathways (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 neither 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 pyramidal neurons of the motor (motor) zone of the cerebral cortex, which pass through the entire brain stem to interneurons in 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 subtle and precise movements, mainly of the limbs.

III. Ventral (anterior) funiculi. There are ascending and descending tracts.

· Descending tracts:

Ø Vestibulospinal tract. These are axons of neurons of the vestibular nuclei of the brain stem, which end on neurons of the anterior horns. Functions: k control limb extension.

Ø Reticulospinal tract. These are the axons of the neurons of the reticular nuclei of the trunk, which end on the interneurons of the intermediate zone. Functions: control the movement of the torso and ensure the initiation 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 is the body’s response to a stimulus, carried out with the participation and control of the nervous system. RD – This is a chain of neurons along which signals pass during the implementation of a 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 a stimulus and transforms it into a nervous process.