Brain peduncles anatomy. Brain legs

Brain peduncles, pedunculi cerebri , And posterior perforated substance, substantia perforata interpeduncularis, located on the lower surface of the brain (see Fig. , , , ).

In transverse sections of the cerebral peduncles taken at different levels, one can distinguish the anterior part - base of the cerebral peduncle, basis pedunculi cerebri, and the back - tegmentum mesencephali; lies on the border between them black substance, substantia nigra(see fig.).

The base of the cerebral peduncle has a semilunar shape and contains fibers of the longitudinal tracts: corticospinal fibers, fibrae corticospinales, And corticonuclear fibers, fibrae corticonucleares(occupy the middle of the base of the cerebral peduncles), and also cortical-pontine fibers, fibrae corticopontinae.

The black substance, rich in pigment, also has a crescent shape, convexly facing the base of the cerebral peduncles. Within the substantia nigra there is a dorsally located compact part, pars compacta, and ventral reticular part, pars reticularis.

The tegmentum of the midbrain extends from the substantia nigra to the level of the cerebral aqueduct and contains the right and left red kernels, nuclei ruber, nuclei of III, IV, V cranial nerves, clusters of neurons of the reticular formation and longitudinal bundles of fibers. Within the red nucleus, a cranially located small cell part, pars parvocellularis, and caudally located magnocellular part, pars magnocellularis.

In front of the red nucleus at the level of the cranial end of the aqueduct of the brain lies intermediate nucleus, nucleus interstitialis. The neurons of this nucleus are the main source of fibers medial longitudinal fasciculus, fasciculus longitudinalis medialis. The latter can be traced throughout the entire brain stem and occupies a paramedian position. The medial longitudinal fasciculus contains fibers connecting the nuclei of the oculomotor, trochlear and abducens nerves, as well as fibers going from the vestibular nuclei to the nuclei of the III, IV and VI pairs of cranial nerves. These structures are also connected to the motor neurons of the anterior columns of the upper cervical segments of the spinal cord, which innervate the neck muscles. Due to the fibers of the medial longitudinal fasciculus, friendly movements of the head and eyeballs are ensured.

The midbrain tegmentum also contains tire crosses, decussationes tegmenti formed by intersecting fibers red nuclear spinal tract, tractus rubrospinalis, And tectospinal tract, tractus tectospinalis.

Above the tire lies a roof plate. In the middle, along the line separating the right colliculi from the left, there is an opening of the cerebral aqueduct, which connects the cavity of the third ventricle with the cavity of the fourth ventricle. The length of the water pipe is 2.0 – 2.5 cm.

Two cords are directed from the roof plate to the cerebellum - superior cerebellar peduncle, pedunculus cerebellaris rostralis(see fig. , , ). The fibers of each superior cerebellar peduncle begin in the cerebellar nuclei and approach the roof of the midbrain, covering the superior medullary velum on both sides. Next, the fibers follow ventral to the cerebral aqueduct and central gray matter, substantia grisea centralis, intersect, forming decussation of the superior cerebellar peduncles, decussatio pedunculorum cerebellarium rostralium, and almost all end in red nucleus, nucleus ruber. A smaller part of the fibers penetrates the red nucleus and follows to the thalamus, forming dentate-thalamic tract, tractus dentatothalamicus.

Longitudinal fibers pass ventrolateral to the cerebral aqueduct posterior longitudinal fasciculus, fasciculus longitudinalis dorsalis, connecting the thalamus and hypothalamus with the nuclear formations of the brain stem.

The junction of the midbrain and rhombencephalon is the most narrowed part of the brain stem. This part of the brain, sometimes called isthmus rhombencephali, better expressed in the fetus.

The following formations lie in the isthmus of the rhombencephalon (see Fig.,):

superior cerebellar peduncles, pedunculi cerebellares rostrales, which are located along the dorsolateral areas of the roof of the midbrain;
superior medullary velum, velum medullare rostralis, forming the anterior part of the roof of the IV ventricle;
loop triangle, trigonum lemnisci, - a paired formation located between the handle of the inferior colliculus and the inferior colliculus of the roof of the midbrain on one side, the cerebral peduncle on the other and the superior cerebellar peduncle on the third. The triangle contains fibers that form lateral loop, lemniscus lateralis. Most of these fibers consist of central auditory conductors, adjacent on the lateral side to medial loop, lemniscus medialis.

Lateral to the superior cerebellar peduncle, in the groove between it and the middle cerebellar peduncle, there are small bundles, which are the anterior bundles of the middle cerebellar peduncle separated from the substance of the pons.

Between the lower colliculi of the roof of the midbrain, from the groove between them, it originates frenulum of the superior medullary velum, frenulum veli medullaris rostralis, continuing posteriorly into the superior medullary velum. The latter is an unpaired elongated quadrangular thin plate of white matter stretched between the superior cerebellar peduncles (see Fig.).

Anteriorly, the superior medullary velum connects with the lower colliculi of the midbrain roof and with the posterior edges of the triangles of the loops, posteriorly with the white matter of the anterior part of the cerebellar vermis, and laterally with the superior cerebellar peduncles. The middle and posterior sections of its dorsal, or upper, surface are covered by the convolutions of the cerebellar uvula, and the ventral, or lower, surface, facing the cavity of the fourth ventricle, forms the anterosuperior sections of the roof of the cavity of this ventricle.

The superior medullary velum contains intersecting fibers belonging to the roots of the trochlear nerves that form decussation of trochlear nerves, decussatio nervorum trochlearium, and fibers anterior spinocerebellar tract, tractus spinocerebellares anteriores(see fig.).

Somewhat laterally from the frenulum of the superior medullary velum, perforating the latter, a thin trunk of the trochlear nerve emerges onto its surface. This nerve appears at the border between the posterior edge of the loop triangle and the anterior edge of the velum. This is the only cranial nerve that leaves the brain on its back surface, and not on the front, like all the others.

^ 1. Meninges and cavities of the brain

The brain, encephalon, with its surrounding membranes is located in the cavity of the cerebral part of the skull. In this regard, its convex superolateral surface corresponds in shape to the internal concave surface of the cranial vault. The lower surface - the base of the brain - has a complex topography corresponding to the shape of the cranial fossae of the inner base of the skull.

The brain, like the spinal cord, is surrounded by three meninges. These connective tissue sheets cover the brain, and in the area of the foramen magnum they pass into the membranes of the spinal cord. The outermost of these membranes is the dura mater of the brain. It is followed by the middle one - the arachnoid, and inwardly from it there is the inner soft (choroid) membrane of the brain, adjacent to the surface of the brain.

The dura mater of the brain differs from the other two in its special density, strength, and the presence in its composition of a large number of collagen and elastic fibers. Lining the inside of the cranial cavity, the dura mater of the brain is also the periosteum of the inner surface of the bones of the cerebral part of the skull. The hard shell of the brain is loosely connected to the bones of the vault (roof) of the skull and is easily separated from them.

At the inner base of the skull (in the region of the medulla oblongata), the dura mater of the brain fuses with the edges of the foramen magnum and continues into the dura mater of the spinal cord. The inner surface of the dura mater, facing the brain (towards the arachnoid membrane), is smooth.

The largest process of the dura mater of the brain is the falx cerebri (large falciform process), located in the sagittal plane and penetrating into the longitudinal fissure of the cerebrum between the right and left hemispheres. This is a thin crescent-shaped plate of the hard shell, which in the form of two sheets penetrates the longitudinal fissure of the cerebrum. Without reaching the corpus callosum, this plate separates the right and left hemispheres of the cerebrum from each other.

^ 2. Brain mass

The weight of the adult human brain ranges from 1100 to 2000 g; on average, for men it is 1394 g, for women it is 1245 g. The mass and volume of the brain of an adult over the course of 20 to 60 years remain maximum and constant for each given individual. After 60 years, the mass and volume of the brain decrease slightly.

^ 3. Classification of brain regions

When examining a specimen of the brain, its three largest components are clearly visible: the cerebral hemispheres, the cerebellum and the brain stem.

Cerebral hemispheres. In an adult, this is the most highly developed, largest and functionally most important part of the central nervous system. The sections of the cerebral hemispheres cover all other parts of the brain.

The right and left hemispheres are separated from each other by a deep longitudinal fissure of the cerebrum, which in the depths between the hemispheres reaches the large commissure of the brain, or the corpus callosum. In the posterior sections, the longitudinal fissure connects with the transverse fissure of the cerebrum, which separates the cerebral hemispheres from the cerebellum.

On the superolateral, medial and inferior (basal) surfaces of the cerebral hemispheres there are deep and shallow grooves. Deep grooves divide each of the hemispheres into lobes of the cerebrum. Small grooves are separated from each other by the convolutions of the cerebrum.

The lower surface or base of the brain is formed by the ventral surfaces of the cerebral hemispheres, the cerebellum and the most visible ventral parts of the brain stem.

The brain has five sections, developing from five brain vesicles: 1) the telencephalon; 2) diencephalon; 3) midbrain; 4) hindbrain; 5) the medulla oblongata, which at the level of the foramen magnum passes into the spinal cord.

Rice. 7. Parts of the brain

1 - telencephalon; 2 - diencephalon; 3 - midbrain; 4 - bridge; 5 - cerebellum (hindbrain); 6 - spinal cord.

The extensive medial surface of the cerebral hemispheres hangs over the much smaller cerebellum and brain stem. On this surface, as on other surfaces, there are grooves that separate the convolutions of the cerebrum from each other.

The areas of the frontal, parietal and occipital lobes of each hemisphere are separated from the large commissure of the brain, the corpus callosum, which is clearly visible in the median section, by the groove of the same name. Under the corpus callosum there is a thin white plate - the fornix. All formations listed above belong to the telencephalon.

The structures below, with the exception of the cerebellum, belong to the brainstem. The most anterior parts of the brain stem are formed by the right and left visual thalamus - this is the posterior thalamus. The thalamus is located inferior to the body of the fornix and the corpus callosum and behind the column of the fornix. In a midline section, only the medial surface of the posterior thalamus is visible. The interthalamic fusion stands out on it. The medial surface of each posterior thalamus limits the lateral slit-like vertical cavity of the third ventricle. Between the anterior end of the thalamus and the column of the fornix there is an interventricular foramen, through which the lateral ventricle of the cerebral hemisphere communicates with the cavity of the third ventricle. In the posterior direction from the interventricular foramen, the hypothalamic groove stretches around the thalamus from below. The formations located downward from this groove belong to the hypothalamus. These are the optic chiasm, gray tubercle, infundibulum, pituitary gland and mastoid bodies, which participate in the formation of the floor of the third ventricle.

Above and behind the optic thalamus, under the splenium of the corpus callosum, is the pineal body.

The thalamus (optic thalamus), hypothalamus, third ventricle, pineal body belong to the diencephalon.

Caudal to the thalamus are formations related to the midbrain, mesencephalon. Below the pineal gland is the roof of the midbrain (plate quadrigeminal), consisting of the superior and inferior colliculi. The ventral plate of the midbrain roof is the cerebral peduncle, separated from the plate by the midbrain aqueduct. The midbrain aqueduct connects the cavities of the third and fourth ventricles. Even more posteriorly there are midline sections of the pons and cerebellum, related to the hindbrain and a section of the medulla oblongata. The cavity of these parts of the brain is the IV ventricle. The bottom of the IV ventricle is formed by the dorsal surface of the pons and medulla oblongata, which forms a rhomboid fossa on the whole brain. The thin plate of white matter that stretches from the cerebellum to the roof of the midbrain is called the superior medullary velum.

^ 4. Cranial nerves

At the base of the brain, in the anterior sections formed by the lower surface of the frontal lobes of the cerebral hemispheres, olfactory bulbs can be found. They look like small thickenings located on the sides of the longitudinal fissure of the cerebrum. 15-20 thin olfactory nerves (I pair of cranial nerves) approach the ventral surface of each of the olfactory bulbs from the nasal cavity through holes in the ethmoid plate.

A cord stretches back from the olfactory bulb - the olfactory tract. The posterior sections of the olfactory tract thicken and widen, forming the olfactory triangle. The posterior side of the olfactory triangle turns into a small area with a large number of small holes remaining after removal of the choroid. Medial to the perforated substance, closing the posterior sections of the longitudinal fissure of the cerebrum on the lower surface of the brain, there is a thin, gray, easily torn terminal, or terminal, plate. The optic chiasm is adjacent to this plate at the back. It is formed by fibers that are part of the optic nerves (II pair of cranial nerves), penetrating into the cranial cavity from the eye sockets. Two optic tracts extend from the optic chiasm in the posterolateral direction.

A gray tubercle is adjacent to the posterior surface of the optic chiasm. The lower sections of the gray mound are elongated in the form of a tube tapering downward, which is called a funnel. At the lower end of the funnel there is a rounded formation - the pituitary gland, an endocrine gland.

Adjacent to the gray tubercle at the back are two white spherical elevations - the mastoid bodies. Posterior to the optic tracts, two longitudinal white ridges are visible - the cerebral peduncles, between which there is a depression - the interpeduncular fossa, bounded in front by the mastoid bodies. On the medial surfaces of the cerebral peduncles facing each other, the roots of the right and left oculomotor nerves (III pair of cranial nerves) are visible. The lateral surfaces of the cerebral peduncles bend around the trochlear nerves (IV pair of cranial nerves), the roots of which exit the brain not at its base, like all the other 11 pairs of cranial nerves, but on the dorsal surface, behind the lower colliculi of the roof of the midbrain, on the sides of the frenulum superior medullary velum.

The cerebral peduncles posteriorly emerge from the upper parts of a wide transverse ridge, which is designated as the pons. The lateral sections of the pons continue into the cerebellum, forming the paired middle cerebellar peduncle.

At the border between the pons and the middle cerebellar peduncles on each side you can see the root of the trigeminal nerve (V pair of cranial nerves).

Below the bridge are the anterior sections of the medulla oblongata, which are represented by medially located pyramids, separated from each other by the anterior median fissure. Lateral from the pyramid there is a rounded elevation - an olive. At the border of the pons and the medulla oblongata, on the sides of the anterior median fissure, the roots of the abducens nerve (VI pair of cranial nerves) emerge from the brain. Also lateral, between the middle cerebellar peduncle and the olive, on each side the roots of the facial nerve (VII pair of cranial nerves) and the vestibulocochlear nerve (VIII pair of cranial nerves) are sequentially located. The dorsal olive roots in an inconspicuous groove pass from front to back the roots of the following cranial nerves: glossopharyngeal (IX pair), vagus (X pair), and accessory (XI pair). The roots of the accessory nerve also extend from the spinal cord in its upper part - these are the spinal roots. In the groove separating the pyramid from the olive, there are the roots of the hypoglossal nerve (XII pair of cranial nerves).

Topic 4. External and internal structure of the medulla oblongata and pons

^ 1. Medulla oblongata, its nuclei and pathways

The hindbrain and medulla oblongata were formed as a result of the division of the rhomboid vesicle. The hindbrain, metencephalon, includes the pons, located anteriorly (ventrally), and the cerebellum, which is located behind the pons. The cavity of the hindbrain, and with it the medulla oblongata, is the IV ventricle.

The medulla oblongata, medulla oblongata (myelencephalon), is located between the hindbrain and the spinal cord. The upper border of the medulla oblongata on the ventral surface of the brain runs along the lower edge of the pons; on the dorsal surface it corresponds to the medullary stripes of the fourth ventricle, which divide the bottom of the fourth ventricle into the upper and lower parts.

The boundary between the medulla oblongata and the spinal cord corresponds to the level of the foramen magnum or the place where the upper part of the roots of the first pair of spinal nerves exits the brain.

The upper sections of the medulla oblongata are somewhat thicker than the lower ones. In this regard, the medulla oblongata takes the shape of a truncated cone or bulb, for its similarity with which it is also called a bulb - bulbus.

The length of the medulla oblongata of an adult is on average 25 mm.

In the medulla oblongata, there are ventral, dorsal and two lateral surfaces, which are separated by grooves. The sulci of the medulla oblongata are a continuation of the sulci of the spinal cord and have the same names: anterior median fissure, posterior median sulcus, anterolateral sulcus, posterolateral sulcus. On both sides of the anterior median fissure on the ventral surface of the medulla oblongata there are convex, gradually tapering pyramidal ridges, pyramides.

In the lower part of the medulla oblongata, the bundles of fibers that make up the pyramids move to the opposite side and enter the lateral cords of the spinal cord. This fiber transition is called the pyramidal decussation. The decussation also serves as the anatomical boundary between the medulla oblongata and the spinal cord. On the side of each pyramid of the medulla oblongata there is an oval eminence - the olive, oliva, which is separated from the pyramid by the anterolateral groove. In this groove, the roots of the hypoglossal nerve (XII pair) emerge from the medulla oblongata.

On the dorsal surface, on the sides of the posterior median sulcus, thin and wedge-shaped bundles of the posterior cords of the spinal cord, separated from each other by the posterior intermediate sulcus, end with thickenings. The thin bundle lying more medially forms a tubercle of the thin nucleus. The lateral location is the wedge-shaped fasciculus, which forms the tubercle of the wedge-shaped nucleus on the side of the tubercle of the thin fasciculus. Dorsal to the olive, from the posterolateral groove of the medulla oblongata - behind the olive groove, the roots of the glossopharyngeal, vagus and accessory nerves (IX, X and XI pairs) emerge.

The dorsal part of the lateral funiculus widens slightly upward. Here it is joined by fibers extending from the wedge-shaped and tender nuclei. Together they form the inferior cerebellar peduncle. The surface of the medulla oblongata, bounded below and laterally by the inferior cerebellar peduncles, participates in the formation of the rhomboid fossa, which is the bottom of the fourth ventricle.

A transverse section through the medulla oblongata at the level of the olives reveals accumulations of white and gray matter. In the inferolateral sections there are the right and left lower olive nuclei.

They are curved in such a way that their hilum faces medially and upward. Slightly above the lower olivary nuclei there is a reticular formation formed by the interweaving of nerve fibers and the nerve cells lying between them and their clusters in the form of small nuclei. Between the lower olive nuclei there is the so-called interolive layer, represented by internal arcuate fibers - processes of cells lying in the thin and wedge-shaped nuclei. These fibers form the medial lemniscus. The fibers of the medial lemniscus belong to the proprioceptive pathway of the cortical direction and form the decussation of the medial lemniscus in the medulla oblongata. In the superolateral parts of the medulla oblongata, the right and left inferior cerebellar peduncles are visible on the section. The fibers of the anterior spinocerebellar and red nuclear spinal tracts pass somewhat ventrally. In the ventral part of the medulla oblongata, on the sides of the anterior median fissure, there are pyramids. Above the intersection of the medial loops is the posterior longitudinal fasciculus.

The medulla oblongata contains the nuclei of the IX, X, XI and XII pairs of cranial nerves, which take part in the innervation of internal organs and derivatives of the branchial apparatus. The ascending pathways to other parts of the brain also pass here. The ventral sections of the medulla oblongata are represented by descending motor pyramidal fibers. Dorsolaterally, ascending pathways pass through the medulla oblongata, connecting the spinal cord with the cerebral hemispheres, brain stem and cerebellum. In the medulla oblongata, as in some other parts of the brain, there is a reticular formation, as well as such vital centers as the circulatory and respiratory centers.

Figure 8.1. The anterior surfaces of the frontal lobes of the cerebral hemispheres, diencephalon and midbrain, pons and medulla oblongata.

III-XII - corresponding pairs of cranial nerves.

^ 2. The bridge, its cores and pathways

IN
The roots of the right and left abducens nerves emerge from the deep transverse groove separating the pons from the pyramids of the medulla oblongata. In the lateral part of this groove the roots of the facial (VII pair) and vestibulocochlear (VIII pair) nerves are visible.

A cross-section of the bridge shows that the substance that forms it is heterogeneous. In the central sections of the bridge section, a thick bundle of fibers is noticeable, running transversely and relating to the conduction path of the auditory analyzer - the trapezoidal body. This formation divides the bridge into a posterior part, or tegmentum, and an anterior (basilar) part.

Between the fibers of the trapezoidal body are the anterior and posterior nuclei of the trapezoidal body. Longitudinal and transverse fibers are visible in the front part of the bridge. The longitudinal fibers of the bridge belong to the pyramidal tract (corticonuclear fibers). There are also cortical-pontine fibers, which end on the nuclei (proprietary) of the bridge, located between groups of fibers in the thickness of the bridge. The processes of the nerve cells of the pontine nuclei form bundles of transverse fibers of the bridge. The latter are directed towards the cerebellum, forming the middle cerebellar peduncles.

In the posterior (dorsal) part (pons tegmentum), in addition to the ascending fibers, which are a continuation of the sensitive pathways of the medulla oblongata, there are focal accumulations of gray matter - the nuclei, V, VI, VII, VIII pairs of cranial nerves. Directly above the trapezoid body lie the fibers of the medial lemniscus, and lateral to them - the spinal lemniscus.

Above the trapezoidal body, closer to the median plane, is the reticular formation, and even higher is the posterior longitudinal fasciculus. Lateral and above the medial lemniscus lie the fibers of the lateral lemniscus.

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is. 8.2. Brain stem, top and back view

^ Fourth (IV) ventricle is a derivative of the cavity of the rhombencephalon. The medulla oblongata, pons, cerebellum and isthmus of the rhombencephalon take part in the formation of the walls of the fourth ventricle. The shape of the cavity of the IV ventricle resembles a tent, the bottom of which has the shape of a rhombus (diamond-shaped fossa) and is formed by the posterior (dorsal) surfaces of the medulla oblongata and the pons. The border between the medulla oblongata and the pons on the surface of the rhomboid fossa is the medullary stripes (IV ventricle). They run in the transverse direction, originate in the area of the lateral corners of the rhomboid fossa and plunge into the median sulcus.

The roof of the IV ventricle in the form of a tent hangs over the rhomboid fossa. The superior cerebellar peduncles and the superior medullary velum stretched between them take part in the formation of the anterosuperior wall of the tent.

^ Diamond fossa It is a diamond-shaped depression, the long axis of which is directed along the brain. It is bounded laterally in its upper section by the superior cerebellar peduncles, and in the lower section by the inferior cerebellar peduncles. In the posteroinferior corner of the rhomboid fossa, under the lower edge of the roof of the fourth ventricle, there is an entrance to the central canal of the spinal cord. In the anterior-superior corner there is a hole leading into the midbrain aqueduct, through which the cavity of the third ventricle communicates with the fourth ventricle. The lateral corners of the rhomboid fossa form the lateral recesses. In the median plane, along the entire surface of the rhomboid fossa, from its upper corner to the lower, a shallow median groove extends. On the sides of this groove there is a paired medial eminence. In the upper parts of the eminence related to the pons, there is a facial tubercle, corresponding to the nucleus of the abducens nerve (VI pair) located in this place in the thickness of the brain and the genus of the facial nerve encircling it, the nucleus of which lies somewhat deeper and lateral. The anterior (cranial) sections of the border sulcus, somewhat deepening and widening upward (anteriorly), form the superior (cranial) fossa. The posterior (caudal, lower) end of this groove continues into the lower (caudal) fossa, barely visible on preparations.

In the anterior (upper) sections of the rhomboid fossa, slightly to the side of the median eminence, a small area is noticeable, differing from the others in a bluish color, and therefore it received the name bluish place. In the lower parts of the rhomboid fossa, which belongs to the medulla oblongata, the median eminence gradually narrows, passing into the triangle of the hypoglossal nerve. Laterally there is a smaller triangle of the vagus nerve, in the depth of which lies the autonomic nucleus of the vagus nerve. The nuclei of the vestibulocochlear nerve lie in the lateral corners of the rhomboid fossa.

^ Projection of the cranial nerve nuclei onto the rhomboid fossa . The gray matter in the area of the rhomboid fossa is located in the form of separate clusters, or nuclei, which are separated from each other by white matter. To understand the topography of the gray matter of the rhomboid fossa, it should be remembered that the neural tube in the region of the medulla oblongata and the pons opened on its posterior (dorsal) surface and unfolded in such a way that its posterior sections turned into the lateral parts of the rhomboid fossa. Thus, the sensitive nuclei of the rhomboid brain, corresponding to the posterior horns of the spinal cord, occupy a lateral position in the rhomboid fossa. The motor nuclei, corresponding to the anterior horns of the spinal cord, are located medially in the rhomboid fossa. In the white matter between the motor and sensory nuclei of the rhomboid fossa there are the nuclei of the autonomic (autonomic) nervous system.

In the gray matter of the medulla oblongata and the pons (in the rhomboid fossa) lie the nuclei of the cranial nerves (from the V to the XII pairs). In the area of the superior triangle of the rhomboid fossa lie the nuclei of the V, VI, VII and VIII pairs of cranial nerves. The V pair, the trigeminal nerve, has four nuclei.

1. The motor nucleus of the trigeminal nerve is located in the upper parts of the rhomboid fossa, in the region of the cranial fossa. The processes of the cells of this nucleus form the motor root of the trigeminal nerve.

2. The sensitive nucleus, to which the fibers of the sensory root of this nerve approach, consists of two parts:

A) the pontine nucleus of the trigeminal nerve lies lateral and somewhat posterior to the motor nucleus; the projection of the pontine nucleus corresponds to the locus coeruleus.

B) the (lower) nucleus of the spinal trigeminal nerve is, as it were, a continuation of the previous nucleus, has an elongated shape and lies throughout the entire length of the medulla oblongata, extends into the upper (I-V) segments of the spinal cord;

C) the nucleus of the midbrain tract of the trigeminal nerve is located cranial (upward) from the motor nucleus of this nerve, next to the midbrain aqueduct.

The VI pair, the abducens nerve, has one motor nucleus of the abducens nerve, located in the genu loop of the facial nerve, deep in the facial colliculus.

VII pair, the facial nerve, has three nuclei.

Facial nerve nucleus
The nucleus of the solitary tract, sensitive, common to the VII, IX, X pairs of cranial nerves, lies in the depth of the rhomboid fossa, projects to the lateral border sulcus.
The superior salivatory nucleus, rior), autonomic (parasympathetic), is located in the reticular formation of the pons,

The VIII pair, the vestibular-cochlear nerve, has two groups of nuclei: two cochlear (auditory) and four vestibular (vestibular), which lie in the lateral sections of the pons and are projected into the area of the vestibular field of the rhomboid fossa.

The nuclei of the last four pairs of cranial nerves (IX, X, XI and XII) lie in the inferior triangle of the rhomboid fossa, formed by the dorsal part of the medulla oblongata.

The IX pair, the glossopharyngeal nerve, has three nuclei, one of which (motor) is common to the IX and X pairs of cranial nerves.

The double nucleus (motor) is located in the reticular formation, in the lower half of the rhomboid fossa, and is projected in the area of the caudal fossa.
Nucleus of the solitary tract, (sensitive), common to the VII, IX and X pairs of cranial nerves.
The inferior salivary nucleus is vegetative (parasympathetic), located in the reticular formation of the medulla oblongata between the inferior olivary nucleus and the double nucleus.

The X pair, the vagus nerve, has three nuclei: motor, sensory and autonomic (parasympathetic).

The XIth pair, the accessory nerve, has a motor nucleus of the accessory nerve.

The XII pair, the hypoglossal nerve, has one nucleus in the lower corner of the rhomboid fossa, deep in the triangle of the hypoglossal nerve. This is the motor nucleus of the hypoglossal nerve.

Topic 4. Structure of the cerebellum

^ 1. General plan of the structure of the cerebellum

The cerebellum (small brain), cerebellum, is located posterior to the pons and from the upper (dorsal) part of the medulla oblongata. It lies in the posterior cranial fossa. Above the cerebellum hang the occipital lobes of the cerebral hemispheres, which are separated from the cerebellum by the transverse fissure of the cerebrum.

The cerebellum is distinguished between superior and inferior surfaces, the boundary between which is the posterior edge of the cerebellum, where a deep horizontal fissure runs. It begins at the point where its middle peduncles enter the cerebellum. The superior and inferior surfaces of the cerebellum are convex. On the lower surface there is a wide depression - the cerebellar valley; the dorsal surface of the medulla oblongata is adjacent to this depression.

In the cerebellum, there are two hemispheres and an unpaired median part, the cerebellar vermis (phylogenetically the oldest part). The upper and lower surfaces of the hemispheres and the vermis are cut by many transverse parallel fissures of the cerebellum, between which there are long and narrow leaves (gyri) of the cerebellum. Groups of gyri, separated by deeper grooves, form the cerebellar lobules.

The grooves of the cerebellum run, without interruption, through the hemispheres and through the vermis, and each lobe of the vermis corresponds to two (right and left) lobes of the hemispheres. The more isolated and phylogenetically older lobule of each hemisphere is the shred. It is adjacent to the ventral surface of the middle cerebellar peduncle. With the help of the long leg of the flocculus, the flocculus is connected to the cerebellar vermis, with its node.

The cerebellum is connected to neighboring parts of the brain by three pairs of peduncles. The inferior cerebellar peduncles extend downward and connect the cerebellum to the medulla oblongata. The middle cerebellar peduncles are the thickest, they go anteriorly and pass into the pons. The superior cerebellar peduncles connect the cerebellum to the midbrain. The cerebellar peduncles contain fibers of the pathways that connect the cerebellum with other parts of the brain and the spinal cord.

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Fig. 9. Brain stem and cerebellum, lateral view

^2. Cerebellar cortex

The cerebellar hemispheres and the vermis consist of the intracerebral body, white matter and a thin plate of gray matter covering the white matter - the cerebellar cortex.

In the thickness of the leaves of the cerebellum, the white matter has the appearance of thin white stripes (plates). The white matter of the cerebellum contains paired cerebellar nuclei. The most significant of these is the dentate nucleus. On a horizontal section of the cerebellum, this nucleus has the shape of a thin curved gray strip, which with its convex part faces laterally and backward. In the medial direction, the gray stripe is not closed; this place is called the hilum of the dentate nucleus; it is filled with white matter fibers that form the superior cerebellar peduncle. Inward from the dentate nucleus, in the white matter of the cerebellar hemisphere, are the corky nucleus and the globular nucleus. Here, in the white matter of the worm, is the most medial nucleus - the tent nucleus.

The white matter of the worm, bordered by bark and divided along the periphery by numerous deep and shallow grooves, on a sagittal section has a bizarre pattern reminiscent of a tree branch, hence its name “tree of life.”

The gray matter of the pons is represented by the nuclei of the V, VI, VII, VIII pairs of cranial nerves, which provide eye movements, facial expressions, and the activity of the auditory and vestibular apparatus; the nuclei of the reticular formation and the proper nuclei of the pons, which participate in the connections of the cerebral cortex with the cerebellum and transmit impulses from one part of the brain to another through the pons. In the dorsal sections of the bridge, ascending sensory pathways follow, and in the ventral sections, descending pyramidal and extrapyramidal pathways follow. There are also fiber systems here that provide bilateral communication between the cerebral cortex and the cerebellum. The cerebellum has nuclei (centers) that provide coordination of movements and maintain body balance.

Topic 5. Midbrain. The concept of the extrapyramidal system

^ 1. Structure of the midbrain: quadrigeminal and cerebral peduncles

The midbrain, mesencephalon, unlike other parts of the brain, is less complex. It has a roof and legs. The cavity of the midbrain is the cerebral aqueduct. The upper (anterior) border of the midbrain on its ventral surface is the optic tracts and mammillary bodies, and on the rear - the anterior edge of the pons. On the dorsal surface, the upper (anterior) border of the midbrain corresponds to the posterior edges of the thalami, the posterior (lower) border corresponds to the level of exit of the roots of the trochlear nerve (n. trochlearis, IV pair).

The roof of the midbrain, which is the quadrigeminal plate, is located above the cerebral aqueduct. On a brain specimen, the roof of the midbrain can be seen only after the cerebral hemispheres have been removed. The roof of the midbrain consists of four elevations - mounds, shaped like hemispheres. The latter are separated from each other by two grooves intersecting at right angles. The longitudinal groove is located in the median plane and in its upper (anterior) sections forms a bed for the pineal gland, and in the lower sections it serves as the place from which the frenulum of the superior medullary velum begins. A transverse groove separates the superior colliculi from the inferior colliculi. From each of the mounds, thickenings in the form of a roller extend in the lateral direction - the handle of the mound. The handle of the superior colliculus is located posterior to the thalamus and goes to the lateral geniculate body. The handle of the inferior colliculus is directed towards the medial geniculate body.

In humans, the superior colliculus of the midbrain roof (quadrigeminal) and the lateral geniculate body perform the function of subcortical visual centers. The inferior colliculus and medial geniculate body are subcortical auditory centers.

The cerebral peduncles are clearly visible at the base of the brain in the form of two thick white, longitudinally striated ridges that emerge from the pons, go forward and laterally (diverge at an acute angle) to the right and left hemispheres of the cerebrum. The depression between the right and left cerebral peduncles is called the interpeduncular fossa.

On the medial surface of each cerebral peduncle there is a longitudinal oculomotor groove from which the roots of the oculomotor nerve (III pair) emerge.

The cerebral peduncles are located anterior to the cerebral aqueduct. On a cross section of the midbrain in the cerebral peduncle, the black substance, substantia nigra, clearly stands out with its dark color (due to the melanin pigment contained in the nerve cells). It extends in the cerebral peduncle from the pons to the diencephalon. The substantia nigra divides the cerebral peduncle into two sections: the posterior section, the tegmentum of the midbrain, and the anterior section, the base of the cerebral peduncle. The midbrain nuclei lie in the tegmentum and ascending pathways pass through.

The base of the cerebral peduncle consists entirely of white matter; descending pathways pass here. The midbrain aqueduct (Sylvian aqueduct) is a narrow canal about 1.5 cm long; connects the cavity of the third ventricle with the fourth and contains cerebrospinal fluid. In its origin, the cerebral aqueduct is a derivative of the cavity of the middle cerebral bladder. A frontal section of the midbrain shows that the roof of the midbrain (collices) consists of gray matter (gray and white layers of the superior colliculus and the nucleus of the inferior colliculus), which is externally covered with a thin layer of white matter.

Rice. 10. Cross section of the midbrain at the level of the superior colliculus

^ 2. Midbrain nuclei

Around the midbrain aqueduct there is a central gray matter in which, in the area of the bottom of the aqueduct, there are the nuclei of two pairs of cranial nerves. At the level of the superior colliculi, under the ventral wall of the midbrain aqueduct, near the midline, there is a paired nucleus of the oculomotor nerve. It takes part in the innervation of the eye muscles. Ventral to it is the parasympathetic nucleus of the autonomic nervous system - the accessory nucleus of the oculomotor nerve (Yakubovich nucleus, Westphal-Edinger nucleus).

Fibers arising from the accessory nucleus innervate the smooth muscles of the eyeball (the muscle that constricts the pupil and the ciliary muscle). Anterior and slightly above the nucleus of the third pair is one of the nuclei of the reticular formation - the intermediate nucleus. The processes of the cells of this nucleus participate in the formation of the reticulospinal tract and the posterior longitudinal fasciculus.

At the level of the inferior colliculi, in the ventral sections of the central gray matter, lies the paired nucleus of the IV pair - the nucleus of the trochlear nerve. The trochlear nerve leaves the brain behind the inferior colliculus, on the sides of the frenulum of the superior medullary velum. In the lateral parts of the central gray matter throughout the entire midbrain there is the nucleus of the midbrain tract of the trigeminal nerve (V pair).

In the tegmentum, the largest and most noticeable on a cross section of the midbrain is the red nucleus, nucleus ruber, it is located slightly above (dorsal) the substantia nigra, has an elongated shape and extends from the level of the inferior colliculus to the thalamus. Lateral and above the red nucleus in the tegmentum of the cerebral peduncle, a bundle of fibers that are part of the medial lemniscus is visible in the frontal section. Between the medial lemniscus and the central gray matter is the reticular formation.

^ 3. Midbrain pathways

The base of the cerebral peduncle is formed by descending pathways. The inner and outer sections of the base of the cerebral peduncles form fibers of the cortical-pontine tract, the medial part of the base is occupied by the frontal-pontine tract, and the lateral part is occupied by the temporo-parietal-occipital-pontine tract. The middle part of the base of the cerebral peduncle is occupied by the pyramidal tracts. The corticonuclear fibers pass medially, and the corticospinal tracts pass laterally.

In the midbrain there are subcortical centers of hearing and vision, which provide innervation to the voluntary and involuntary muscles of the eyeball, as well as the midbrain nucleus of the V pair.

The extrapyramidal system includes the substantia nigra, red nucleus and nucleus interstitialis, which provide muscle tone and control automatic unconscious movements of the body. Ascending (sensory) and descending (motor) pathways pass through the midbrain.

The nerve fibers that make up the medial lemniscus are processes of the second neurons of the proprioceptive sensitivity pathways. The medial lemniscus is formed by internal arcuate fibers. The latter are processes of the cells of the nuclei of the sphenoid and thin fasciculi and are directed from the medulla oblongata to the nuclei of the thalamus along with the fibers of general sensitivity (pain and temperature), forming the spinal loop adjacent to it.

In addition, fibers from the sensitive nuclei of the trigeminal nerve pass through the tegmentum of the midbrain, called the trigeminal lemniscus and also heading to the nuclei of the thalamus.

The processes of nerve cells of some nuclei form the decussations of the tegmentum in the midbrain. One of them, the dorsal decussation of the tegmentum, belongs to the fibers of the tegmental spinal tract, the other, the ventral decussation of the tegmentum, belongs to the fibers of the red nuclear spinal tract.

In the process of studying how the brain changed during evolution, the idea was developed that there are three levels of it. The first of them (the highest) is the anterior section. It includes the basal subcortical ganglia, the diencephalic cortex and the olfactory brain. The middle department refers to the middle level. And the lower part includes the posterior section, which consists of the medulla oblongata, cerebellum and pons.

The midbrain, the functions and structure of which we will consider in detail, develops mainly under the influence of the visual receptor in the process of phylogenesis. Consequently, its most important formations relate to the innervation of the eye.

Hearing centers also formed in it, which later, together with the vision centers, grew and formed 4 mounds of the roof of the midbrain. We will look at its structure in detail below. And the functions of the midbrain are described in the second half of this article.

Midbrain development

The visual and auditory centers located in it became subcortical, intermediate, falling into a subordinate position with the appearance in humans and higher animals of the cortical end of the visual and in the forebrain cortex. Development in humans and higher mammals has led to the fact that the pathways connecting the terminal cortex with the spinal cord began to pass through the midbrain, the functions of which have changed somewhat. As a result, the latter has:

Subcortical auditory centers;

Visual subcortical centers, as well as the nuclei of nerves that innervate the muscles of the eye;

All descending and ascending pathways that connect the cerebral cortex with the spinal cord and pass through the middle transit;

Bundles of white matter connecting the midbrain with various parts of the central nervous system.

Structure

The midbrain, the functions and structure of which we are interested in, is the simplest and smallest section (in the photo above it is indicated in brown). It has the following 2 main parts:

Legs, where the conduction pathways mainly pass;

Subcortical centers of vision and hearing.

Roof of the midbrain

The roof of the midbrain, the dorsal part, is hidden under the corpus callosum (its posterior end). It is divided into 4 mounds located in pairs by means of two grooves (transverse and longitudinal), running crosswise. The two upper hillocks are the subcortical centers of vision, and the two lower ones are the hearing centers. Between the superior tubercles, in a flat groove, is the pineal gland. The handle of the mound is directed laterally, upward and anteriorly, and each mound passes into it. The handle of the superior colliculus runs under the thalamic cushion towards the lateral geniculate body. The manubrium of the inferior one disappears under the geniculate medial body. The geniculate bodies mentioned above no longer belong to the midbrain, but to the diencephalon.

Brain stems

We continue to describe the average human brain, functions and structure. The next thing we'll focus on is his legs. What is it? This is the ventral part, which contains all the pathways leading to the forebrain. Note that the legs are two semi-cylindrical thick white strands, diverging at an angle from the edge of the bridge and plunging into the hemispheres.

What is the midbrain cavity?

Many terms can be found in such a section as the anatomy of the midbrain. Its structure and functions require strict scientific accuracy when describing it. We have omitted complex Latin names and left only basic terms. This is enough for the first acquaintance.

Let's say a few words about the midbrain cavity. It is a narrow channel and is called a water pipe. This canal is lined with ependyma, it is narrow, its length is 1.5-2 cm. The cerebral aqueduct connects the fourth ventricle to the third. The peduncle tire limits it ventrally, and dorsally - the roof of the midbrain.

Parts of the midbrain in cross section

Let's continue our story. The features of the human midbrain can be better understood by examining it in a cross section. In this case, the following 3 main parts are distinguished in it:

Cover plate;

Tire;

The ventral section, that is, the base of the leg.

Midbrain nuclei

Under the influence of the visual receptor, according to how the midbrain is developed, it contains various nuclei. The functions of the midbrain nuclei relate to the innervation of the eye. The superior colliculus in lower vertebrates is the main place where the optic nerve ends and is also the main visual center. In humans and mammals, with the transfer of visual centers to the forebrain, the connection that remains between the superior colliculus and the optic nerve is important only for reflexes. The fibers of the auditory lemniscus end in the geniculate medial body, as well as in the nucleus of the inferior colliculus. The roof of the midbrain is connected to the spinal cord by a bidirectional connection. The plate of this roof can be considered a reflex center for movements that arise mainly under the influence of auditory and visual stimuli.

Brain plumbing

It is surrounded by central gray matter, which in its function belongs to the autonomic system. Under its ventral wall, in the tegmentum of the cerebral peduncle, there are the nuclei of two cranial motor nerves.

Oculomotor nerve nucleus

It consists of several sections of innervation of various muscles of the eyeball. Posterior and medial to it there is a paired small accessory vegetative nucleus, as well as a median unpaired one. The unpaired median and accessory nuclei innervate the muscles of the eye, which are involuntary. We attribute this part to the parasympathetic system. Rostral (above) the nucleus of the oculomotor nerve is located in the tegmentum of the cerebral peduncle the nucleus of the longitudinal medial fasciculus.

Brain stems

They are divided into the base of the stalk (ventral part) and the tire. The substantia nigra serves as the boundary between them. It owes its color to melanin, a black pigment found in the nerve cells that make it up. The tegmentum of the midbrain is the part of it located between the substantia nigra and the roof. The central tire track departs from it. This is a descending projection nerve pathway, which is located in the tegmentum of the midbrain (its central part). It consists of fibers that go from the globus pallidus, midbrain and thalamus to the olive and reticular formation of the medulla oblongata. This pathway is part of the extrapyramidal system.

Functions of the midbrain

It plays a very important role in the formation of righting and righting reflexes, which make walking and standing possible. In addition, the midbrain has the following functions: it regulates muscle tone and takes part in its distribution. And this is a necessary condition for the implementation of coordinated movements. Another function is that thanks to it, a number of vegetative processes are regulated (swallowing, chewing, breathing, blood pressure). Due to sentinel auditory and visual reflexes, as well as an increase in the tone of the flexor muscles, the midbrain (shown in red in the photo above) prepares the body to respond to a sudden irritation. Statokinetic and static reflexes are realized at its level. Tonic reflexes ensure the restoration of balance and posture that was disturbed as a result of a change in position. They appear when the position of the head and body in space changes due to the excitation of proprioceptors, as well as tactile receptors located on the skin. All these functions of the midbrain indicate that it plays an important role in the body.

Cerebellum

Let us now move on to consider the cerebellum. What is it? This is the structure of the rhombencephalon. It is formed in ontogenesis from the rhomboid vesicle (its dorsal wall). It is connected to various parts of the nervous system that control our movements. Its development occurs along the path of improving connections with the spinal cord, as well as weakening them with the vestibular system.

Research by Luigi Luciani

The functions of the midbrain and cerebellum were studied by Luigi Luciani, an Italian physicist. In 1893, he conducted experiments on animals with the cerebellum completely or partially removed. He also analyzed its bioelectrical activity, recording it during irritation and at rest.

It turned out that the tone of the extensor muscles increases when half of the cerebellum is removed. The animal's limbs are stretched, the body is bent, and the head is tilted towards the operated side. Movements occur in a circle (“maneuver movements”) towards the operated side. The described disturbances are gradually smoothed out, but a certain incoordination of movements remains.

If the entire cerebellum is removed, severe movement disorders occur. They are smoothed out gradually due to the fact that the cerebral cortex (its motor zone) is activated. However, the animal still remains with a lack of coordination. Imprecise, awkward, sweeping movements and a shaky gait are observed.

Contribution of Academician Orbeli

In 1938, academician Orbeli discovered that the cerebellum also influences the receptor apparatus and vegetative processes. In addition, there is a connection with the state of the muscles of internal organs. Changes in blood composition, blood circulation, respiration, and digestion, which occur under the influence of the cerebellum, are aimed at ensuring (trophic) activity of skeletal muscles.

Academician Orbeli considered the cerebellum not only as an assistant to the cerebral cortex in regulating muscle movements and tone, but also as an adaptation-trophic center. In this role, it influences everything through the nervous system (sympathetic division). This is how metabolism is regulated, and the central nervous system adapts to environmental conditions. It was found that the activity of the cerebellum is inextricably linked with the cerebral cortex and occurs under its control.

Conclusion

So, we briefly looked at the human cerebellum and midbrain. Their functions have been described by us. Now you know what an important role they play. Our body is generally designed in such a way that all its organs do their job, they are all necessary. The functions of the medulla oblongata and midbrain, as well as other parts of the body, should be known.

And in conclusion, a few more words. The brain is a complex unit consisting of billions of cells working together. It supports life in a flexible and unique but unchanging way and is capable of responding to changing stimuli, behaviors and needs. As we move through life from infancy to childhood, and then to youth, maturity and old age, our body follows the same path with us. Accordingly, the brain changes. It follows, on the one hand, strictly programmed evolutionary and ontogenetic patterns of development. But on the other hand, it is able to adapt to changing interactions between the external environment and the body.

Midbrain, mesencephalon. It has a roof and legs. The cavity of the midbrain is the cerebral aqueduct. The upper (anterior) border of the midbrain on its ventral surface is the optic tracts and mammillary bodies, and on the rear - the anterior edge of the pons. On the dorsal surface, the upper (anterior) border of the midbrain corresponds to the posterior edges (surfaces) of the thalamus, the posterior (lower) border corresponds to the level of exit of the trochlear nerve roots.

The superior colliculus of the midbrain roof (quadrigeminal) and the lateral geniculate body perform the function of subcortical visual centers. The inferior colliculus and medial geniculate body are subcortical auditory centers.

legs of the brain,pedunculi cerebri, coming out of the bridge. The depression between the right and left cerebral peduncles is called the interpeduncular fossa. The bottom of this fossa serves as the place where blood vessels penetrate the brain tissue. On the medial surface of each cerebral peduncle there is a longitudinal oculomotor groove, sulcus oculomotorus, from which they come roots of the oculomotor nerve, n. oculomotorius(3 pairs).

In the cerebral peduncle it is secreted black matter,substantia nigra. The substantia nigra divides the cerebral peduncle into two sections: the posterior (dorsal) tegmentum of the midbrain, , and the anterior (ventral) section - the base of the cerebral peduncle . The midbrain nuclei lie in the tegmentum and ascending pathways pass through. The base of the cerebral peduncle consists entirely of white matter; descending pathways pass here.

Midbrain plumbing connects the cavity of the 3rd ventricle with the 4th and contains cerebrospinal fluid. The central gray matter is located around the midbrain aqueduct. , in which, in the area of the bottom of the aqueduct, there are nuclei of two pairs of cranial nerves. At the level of the upper mounds there is a steam room nucleus of the oculomotor nerve. It takes part in the innervation of the eye muscles. More ventrally, the parasympathetic nucleus of the autonomic nervous system is localized - accessory nucleus of the oculomotor nerve,. . Anterior and slightly above the nucleus of the III pair is located intermediate nucleus. The processes of the cells of this nucleus participate in the formation of the reticulospinal tract and the posterior longitudinal fasciculus.

At the level of the inferior colliculus in the ventral sections of the central gray matter lies trochlear nerve nucleus. In the lateral sections there is the nucleus of the midbrain tract of the trigeminal nerve (5 pairs).

In the tegmentum, the largest and most noticeable in the cross section of the midbrain is red core, The base of the cerebral peduncle is formed by descending pathways. The internal and external sections of the base of the cerebral peduncles form the fibers of the cortical-pontine tract, namely the medial part of the base is occupied by the frontal-pontine tract, the lateral part is occupied by the temporo-parietal-occipital-pontine tract. The middle part of the base of the cerebral peduncle is occupied by the pyramidal tracts.

The corticonuclear fibers pass medially, and the corticospinal tracts pass laterally.

In the midbrain there are subcortical centers of hearing and vision, which provide innervation to the voluntary and involuntary muscles of the eyeball, as well as the midbrain nucleus of the V pair.

Ascending (sensory) and descending (motor) pathways pass through the midbrain.

Diencephalon: sections, internal structure, connections with other parts of the brain. 3rd ventricle.

Boundaries of the diencephalon are behind - the anterior edge of the posterior perforated substance and the optic tracts, in front - the anterior surface of the optic chiasm. On the dorsal surface, the posterior border is the groove separating the superior colliculi of the midbrain from the posterior edge of the thalamus. The anterolateral border separates the diencephalon and telencephalon on the dorsal side.

The diencephalon includes the following sections: the thalamic region (the area of the visual thalamus, the visual brain), the hypothalamus, which unites the ventral parts of the diencephalon;

3rd ventricle.

The thalamic region includes the thalamus, metathalamus and

Epithalamus.

Thalamus, or thalamus located on both sides of the 3rd ventricle. In the anterior section, the thalamus ends with the anterior tubercle, . The back end is called the cushion. The upper surface is separated from the medial medullary strip of the thalamus. Inferiorly and posteriorly it borders with the tegmentum of the midbrain peduncle.

The thalamus consists of gray matter, in which individual clusters of nerve cells are distinguished - the nuclei of the thalamus. The main nuclei of the thalamus are anterior, medial, posterior, . In fact, it is a subcortical sensitive center.

Metathalamus(zathalamic region), represented by the lateral and medial geniculate bodies. Lateral geniculate body , located near the inferolateral surface of the thalamus, on the side of the pillow. Somewhat inward and posterior to the lateral geniculate body, under the pillow, is the medial geniculate body , on the cells of the nucleus of which the fibers of the lateral (auditory) loop end. The lateral geniculate bodies, together with the superior colliculi of the midbrain, are subcortical centers of vision. The medial geniculate body and the inferior colliculus of the midbrain form the subcortical hearing centers.

Epithalamus(suprathalamic region), includes the pineal body, which, with the help of leashes, connects to the medial surfaces of the right and left thalamus. At the places where the leashes transition into the thalami there are triangular extensions - leash triangles, Hypothalamus, hypothdlamus, forms the lower parts of the diencephalon and participates in the formation of the fundus 3 ventricle The hypothalamus includes the optic chiasm, optic tract, gray tubercle with infundibulum, and mammillary bodies.

Third (III) ventricle occupies a central position in the diencephalon, limited by six walls: two lateral, superior, inferior, anterior and posterior. Lateral walls The third ventricle is the medial surface of the thalamus, as well as the medial parts of the subthalamic region. Bottom wall, or the bottom of the third ventricle, is the hypothalamus. Front wall The third ventricle is formed by the terminal plate, columns of the fornix and the anterior commissure. Rear wall The third ventricle is the epithalamic commissure

Brain, with the surrounding membranes, is located in the cavity of the brain skull. The upper ventral surface of the brain corresponds in shape to the inner concave surface of the cranial vault. The lower surface, the base of the brain, has a complex topography corresponding to the cranial fossae of the inner base of the skull.

Brain mass an adult ranges from 1100 to 2000. Over the course of 20 to 60 years, mass and volume remain maximum and constant for each individual.

When examining a brain specimen, its three largest components are clearly visible:

paired cerebral hemispheres,
cerebellum,
brain stem

Oblong The brain is a direct continuation of the spinal cord. The border between the medulla oblongata and the spinal cord corresponds to the level of the edges of the foramen magnum. The upper border of the medulla oblongata on the ventral surface runs along the posterior edge of the pons.

Anterior sections The medulla oblongata becomes somewhat thicker compared to the posterior ones, and this part of the brain takes on the shape of a truncated cone. Furrows The medulla oblongata are a continuation of the grooves of the spinal cord and have the same names. On both sides of the anterior median fissure on the ventral surface of the medulla oblongata there are convex pyramids gradually tapering towards the bottom.

IN lower part stretches on the dorsal surface of the medulla oblongata posterior median sulcus, on the sides of which the thin and wedge-shaped bundles of the posterior cords of the spinal cord end with thickenings. In these thickenings are located the nuclei of these bundles, from which the fibers that form medial loop. The medial lemniscus at the level of the medulla oblongata forms cross. The bundles of this precross are located dorsal to the pyramids, in the interolive layer. The fibers of the medial bundle also pass here. Lateral to the olive, thin roots of the glossopharyngeal, vagus and accessory nerves emerge from the posterior lateral sulcus, the nuclei of which lie in the dorsolateral parts of the medulla oblongata.

Gray matter the medulla oblongata is represented in the ventral sections by clusters of neurons that form the lower olive kernels. Dorsal to the pyramids along the entire medulla oblongata there is a reticular formation, which is represented by an interweaving of nerve fibers and nerve cells lying between them.

At the level of the medulla oblongata there are vital centers such as respiratory and circulatory centers.

Bridge – at the base of the brain stem, it looks like a transversely located white ridge, which has the appearance of a transversely located white ridge, which in the caudal section borders on the pyramids and olives of the medulla oblongata, and in the cranial section – on the cerebral peduncles. The continuation of the bridge in the lateral direction forms middle cerebellar peduncle. The dorsal surface of the pons is covered by the cerebellum and is not visible from the outside. In the lower parts of the bridge, accumulations of gray matter are noticeable, called cores of the bridge itself, which act as intermediaries in the implementation of connections between the cerebral cortex and the cerebellar hemispheres. In the dorsal part of the pons lie the fibers of the medial lemniscus, coming from the medulla oblongata, above which the reticular formation of the pons is located. The fibers of the auditory lemniscus pass more laterally.

Cerebellum constitutes a larger part of the hindbrain than the pons, which fills most of the posterior cranial fossa.

In the cerebellum there are top and bottom surfaces, the boundaries between which are front and back the edges. The upper surface of the cerebellum on the whole brain is covered by the occipital lobes of the cerebral hemispheres and is separated from them by the deep transverse fissure of the cerebrum. In the cerebellum there are:

unpaired middle part - worm,
two hemispheres.

Transverse grooves the worm is dissected into small convolutions, which give it some resemblance to an annelid worm. Both surfaces of the hemispheres and the vermis are cut by many transverse parallel small grooves, between which there are long and narrow convolutions of the cerebellum. A group of convolutions separated by deeper grooves form cerebellar lobules. The cerebellar hemispheres and the vermis consist of white matter located internally and a thin layer of gray matter of the cerebellar cortex bordering the white matter at the periphery. The cerebellar cortex is represented three layers of nerve cells. On a sagittal section, the white matter of the cerebellum is presented three layers of nerve cells and has the appearance of a branched tree.

In the thickness of the white matter, separate paired clusters of nerve cells are found, which form jagged, cork-shaped, sphericalcerebellar nuclei and tent nucleus.

In the brain stem, the next section after the pons, small but functionally important, is isthmus of the rhombencephalon, consisting of:

superior cerebellar peduncles,
superior medullary velum,
a triangular loop in which the fibers of the lateral (auditory) loop pass.

Midbrain comprises:

dorsal roof of the midbrain,
ventral - the cerebral peduncles, which are delimited by the cavity - the cerebral aqueduct.

The lower border of the midbrain on its ventral surface is the anterior edge of the pons, the superior optic tract and the level of the mammillary bodies. On a brain specimen, the quadrigeminal plate, or the roof of the midbrain, can be seen only after the cerebral hemispheres have been removed.

At the base of the brain, the second part of the midbrain is clearly visible in the form of two thick white diverging bundles going into the tissue of the cerebral hemispheres - this is cerebral peduncles. The depression between the right and left cerebral peduncles is called interpeduncular fossa, the roots of the oculomotor nerves emerge from it. Anterior to the nucleus of the oculomotor nerve lies nucleus of the medial longitudinal fasciculus. The largest nucleus of the midbrain is red core– one of the central coordination nuclei of the extrapyramidal system. Next to the aqueduct lies the reticular form of the midbrain.

The cross section clearly shows the cranial substance, which divides the cerebral peduncle into two sections:

dorsal - midbrain tegmentum,
ventral – base of the cerebral peduncle.

IN tire The midbrain contains the midbrain nuclei and ascending pathways. Ventral The sections of the cerebral peduncles consist entirely of white matter; descending pathways pass here.

Diencephalon educated:

the area of the visual hillocks (thalamic area), which is located in its dorsal areas;
the hypothalamus (subthalamic region), which makes up the ventral sections of the diencephalon;
III ventricle, which has the form of a longitudinal (sagittal) fissure between the right and left visual tuberosities and connects through the interventricular foramen with the lateral ventricles.

In turn, the thalamic region is divided into:

thalamus (visual thalamus),
metathalamus (medal and lateral geniculate body),
epithalamus (pineal body, leashes, leash commissures and epithalamic commissure).

Visual tuberosities consist of gray matter, in which individual clusters of nerve cells (nuclei of the thalamus opticum) are distinguished, separated by thin layers of white matter. Due to the fact that most of the sensory pathways switch here, the thalamus opticum is actually a subcortical sensory center, and its cushion is a subcortical visual center.

The pineal gland is attached to the medial surface of the visual tuberosities using leashes. – pineal gland.

Hypothalamus makes up the ventral part of the diencephalon and participates in the formation of the floor of the third ventricle. The hypothalamus includes:

gray tubercle with a funnel and pituitary gland - iron endocrine, optic tract,
optic chiasm,
mastoid bodies.

The hypothalamus is a continuation of the cerebral peduncles into the diencephalon. The gray matter of the subthalamic region is located in the form of nuclei capable of producing neurosecretion and transporting it to the pituitary gland, regulating the endocrine functioning of the latter.

White matter The diencephalon is represented by conducting pathways of ascending and descending directions, providing bilateral communication of the cerebral cortex with subcortical formations and centers of the spinal cord. In addition, the diencephalon includes two endocrine glands - pituitary gland and pineal gland, taking part together with the corresponding nuclei of the hypothalamus and epithalamus in the formation of the hypothalamic-hypophyseal and epithalamic-epiphyseal systems.

Finite brain consists of two cerebral hemispheres, each of which is represented by the mantle, the olfactory brain and the basal ganglia. The cavity of the telencephalon is the lateral ventricles, located in each hemisphere. The hemispheres of the cerebrum are separated from each other by the longitudinal fissure of the cerebrum and are connected by the corpus callosum, the anterior and posterior commissures and the commissure of the fornix. Corpus callosum consists of transverse fibers, which continue in the lateral direction into the hemispheres, forming the radiance of the corpus callosum, connecting parts of the frontal and occipital lobes of the hemispheres with each other, bending in an arcuate manner and forming the anterior - frontal and posterior - occipital forceps. Adjacent to the posterior and middle parts of the corpus callosum below is the fornix of the brain, consisting of two arched cords fused in its middle part with the help of the anterior commissure of the brain.

Cerebral cortex formed by white and gray matter. There are 6 layers of nerve cells in the cortex, its different sections have different thicknesses (from 1.5 to 5.0 mm, on average 2–3 mm). Each hemisphere has three surfaces:

the most convex superolateral,
flat, facing the opposite hemisphere, medial, having a complex relief corresponding to the internal base of the skull,
inferior, surface of the hemisphere or base of the brain.

The most prominent areas of the hemispheres are called frontal, occipital, temporal poles. The surface of the hemispheres is cut with deep crevices, furrows. The terrain located between them complicates the terrain - convolutions. The depth, length of the furrows, their shape and direction are very variable.

The fissures and grooves divide the hemispheres into:

frontal,
parietal,
temporal,
occipital,
insular lobe.

The latter is not visible when viewing the surfaces of the hemispheres, because the insula is located at the bottom of the lateral sulcus and is covered by areas of other lobes.

Frontal lobe. In front of the central sulcus, the precentral sulcus stretches almost parallel to it, which gives rise to two parallel sulci running towards the frontal pole. These grooves divide the surface of the brain into the precentral gyrus, which lies in front of the central sulcus, and the horizontally running superior, middle and inferior frontal gyri.

Parietal lobe. Behind the central sulcus and almost parallel to it runs the postcentral sulcus, from which the longitudinal intraparietal sulcus runs towards the occipital lobe. These two sulci divide the parietal lobe into the postcentral gyrus and the superior and inferior parietal lobules.

Temporal lobe. The superior lateral surface of the temporal lobe is represented by two grooves running parallel to the lateral sulcus, which divide the surface of the brain into the superior, middle and inferior gyri.

Gray matter of the hemispheres The cerebrum is represented by the cortex and basal ganglia of the telencephalon. The basal ganglia include striatum, consisting of the caudate and lenticular nuclei; fence and amygdala. The layers of white matter between them form the outer and inner capsules, the latter being a thick layer of white matter consisting of the brain's pathways. In the inner capsule they secrete front and back legs and knee.

The cerebral cortex is represented gray matter located on their periphery.

White matter of the hemispheres The cerebrum forms a white semi-oval center, which consists of a huge number of nerve fibers. All nerve fibers are represented by three systems of pathways in the telencephalon:

associative,
commissural,
projection.

Ascending (sensitive) projection pathways at the place of their termination are divided into conscious and reflexive.

The functioning and interconnection of associative, commissural, as well as ascending and descending pathways ensures the existence of complex reflex arcs that allow the body to adapt to constantly changing conditions of the internal and external environment.

Lateral ventricles are located in the thickness of the white matter of the cerebral hemispheres. The cavity of the ventricles has a bizarre shape due to this. That the departments of each of them are located in all lobes of the hemisphere (with the exception of the insula). The middle - central - part of the ventricle lies downward from the corpus callosum, in the parietal lobe of the hemisphere. From the central part, cavities called horns diverge into all lobes of the brain:

anterior (frontal horn) - into the frontal lobe,
lower (temporal horn) - into the temporal,
posterior – (occipital horn) – into the occipital lobe.

The brain, like the spinal cord, is surrounded by three connective tissues leaves or shells, which are a continuation of the membranes of the spinal cord, each of which is separated from its neighbors by the intershell space.

TO peripheral nervous system There are 12 pairs of cranial nerves and 31 pairs of spinal nerves.

All cranial nerves extend from the base of the brain, with the exception of one (IV pair), which leaves the brain from its dorsal side (below the roof of the midbrain). Each nerve is assigned a pair number and name. The numbering order reflects the sequence of exit of the nerves:

I – olfactory nerve,

II – optic nerve,

II – 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.

The olfactory and optic nerves are connected to telencephalon; oculomotor and trochlear – with midbrain; trigeminal, pharyngeal, vagus, accessory and sublingual - with medulla oblongata.

Unlike spinal nerves, which are mixed, cranial nerves are divided into:

sensitive (I, II, VIII),
motor (III, IV, VI, XI, XII),
mixed (V, VII, IX, X).

Some nerves (III, VII, IX, X) contain parasympathetic fibers going to smooth muscles, blood vessels, and glands. Sensory nerves are considered together with their pathways, along the path of excitation, in the centripetal abducens, facial and vestibulocochlear - with the hindbrain; tongue - direction (from the periphery - to the center), motor and mixed nerves - on the contrary, in the centrifugal direction (from the nuclei of the brain - to the periphery).

Ipair – olfactory nerve– sensitive. It consists of olfactory filaments (15–20), which arise from the olfactory cells of the nasal mucosa and are the first neurons of the olfactory pathway. The olfactory filaments enter the cranial cavity through the openings of the cribriform plate and approach the olfactory bulb, where the second neurons of the olfactory pathway are located.

IIpair – optic nerve– sensitive. It originates from the retina of the eyeball and enters the cranial cavity through the optic canal of the sphenoid bone. Further, the fibers of the optic nerves partially intersect and go along the optic tract to the subcortical visual centers located in the superior colliculi of the midbrain roof, the external geniculate bodies and the cushion of the visual colliculi.

IIIpair – oculomotor nerve– motor. Contains parasympathetic fibers going to the muscle that constricts the pupil and to the ciliary muscle, which provides accommodation of the eye. The nerve nucleus lies in the tegmentum of the cerebral peduncles (at the bottom of the midbrain aqueduct).

IV pair – trochlear nerve– motor. The nucleus of the nerve lies in the tegmentum of the cerebral peduncles, next to the nucleus of the oculomotor nerve.

Vpair - trigeminal nerve– mixed. Contains sensory and motor fibers. The nerve nucleus lies in the pons, in the upper part of the rhomboid fossa.

VIpair – abducens nerve– motor. Its core lies in the pons, in the upper part of the rhomboid fossa.

VIIpair - facial nerve– mixed. Contains parasympathetic fibers that go to all salivary glands except the parotid. Its core lies in the pons (in the upper part of the rhomboid fossa).

VIIIpair – vestibulocochlear nerve– sensitive. It is divided into two parts - cochlear and vestibule. The cochlear part transmits auditory excitations from the inner ear to the cortical end of the hearing analyzer, the vestibular part transmits excitation from the balance organs to the cerebellum. The vestibular part of the nerve begins from the receptors of the semicircular ducts and the vestibule of the inner ear, which perceive the position of the body in space. It exits the petrous part of the temporal bone through the internal auditory foramen and enters the brain behind the olive. The nerve fibers approach the pontine nuclei, from where they are directed to the cerebellum.

IXpair - glossopharyngeal nerve– mixed. Contains parasympathetic fibers going to the parotid salivary gland. Its nuclei lie in the medulla oblongata, in the lower part of the rhomboid fossa.

Xpair – vagus nerve– mixed. Contains parasympathetic fibers that go to the smooth muscles of organs located in the chest and abdominal cavities. Its nuclei are located in the medulla oblongata, in the lower part of the rhomboid fossa.

XIpara – accessory nerve– motor. Its nuclei lie in the medulla oblongata and the upper cervical segments of the spinal cord. Accordingly, two parts are distinguished in the nerve - cranial roots and spinal roots.

XIIpair - hypoglossal nerve– motor. Its core lies in the medulla oblongata. The nerve leaves the brain between the pyramid and the olive, and from the skull through the canal of the hypoglossal nerve.

Autonomic nervous system innervates:

internal organs,
vessels,
involuntary muscles,
glands,
skin.

Vegetative means “vegetative” in contrast to somatic - “animal”. However, this division of a single nervous system is conditional, since the autonomic nervous system innervates not only internal organs, but also the apparatus of voluntary movement, sensitivity, and even the central nervous system itself. The autonomic nervous system in close interaction with endocrine and humoral processes:

maintains the constancy of the internal environment,
provides trophic innervation of skeletal muscles (i.e. the function of their nutrition and metabolism).

The autonomic nervous system consists of two sections - sympathetic and parasympathetic, having their centers in various parts of the brain and spinal cord. The functional influence of the sympathetic and parasympathetic divisions of the autonomic nervous system on the internal organs is diametrically opposed. The autonomic nervous system has central and peripheral divisions. The central division is located in the cerebral cortex. In the regulation of autonomic functions, a major role belongs to the frontal and temporal lobes of the brain. They have a coordinating and controlling effect on the activity of the autonomic nervous system through the subcutaneous region. The hypothalamus has three groups of nuclei: front, middle and back. Each group of nuclei regulates one or another function. Thus, the anterior group of nuclei regulates the parasympathetic division, the posterior group - the sympathetic division of the nervous system.

Brain peduncles anatomy. Brain legs

Midbrain development

Structure

Roof of the midbrain

Brain stems

What is the midbrain cavity?

Parts of the midbrain in cross section

Midbrain nuclei

Brain plumbing

Oculomotor nerve nucleus

Brain stems

Functions of the midbrain

Cerebellum

Research by Luigi Luciani

Contribution of Academician Orbeli

Conclusion

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