Diencephalon anatomy of the diencephalon. Complex structure of the diencephalon

diencephalon, diencephalon , on a whole preparation of the brain it is not accessible for viewing, since it is entirely hidden under the cerebral hemispheres (Fig. 146). Only at the base of the brain can one see the central part of the diencephalon, the hypothalamus.

The gray matter of the diencephalon consists of nuclei belonging to the subcortical centers of all types of sensitivity. The diencephalon contains the reticular formation, centers of the extrapyramidal system, vegetative centers (regulate all types of metabolism), and neurosecretory nuclei.

The white matter of the diencephalon is represented by conducting pathways in the ascending and descending directions, providing bilateral communication of the subcortical formations with the cerebral cortex and the nuclei of the spinal cord. In addition, the diencephalon includes two endocrine glands - the pituitary gland, which takes part together with the corresponding nuclei of the hypothalamus in the formation hypothalamic-pituitary system, and the pineal gland of the brain (pineal body).

The boundaries of the diencephalon at the base of the brain are posteriorly the anterior edge of the posterior perforated substance and the optic tracts, and anteriorly the anterior surface of the optic chiasm. On the dorsal surface, the posterior border is a 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. It is formed by the terminal strip (stria terminalis), the corresponding chest between the thalamus and the internal capsule, .

The diencephalon includes sections

thalamic region (area of ​​the visual thalamus, visual brain), which is located in the dorsal areas; j^moTa^uMiiC, uniting the ventral parts of the diencephalon; Ш same-^ small bulbs.

Thalamic region

The thalamic region includes the tadamur, metathalamus and epithalamus.

Thalamus, or rear thalamus, or visual bead,thala-

tnus dorsalis, - narjHoe_jo6rja3_o,BaHje, having a shape close to ovoid, race tsolrzhen on both sides of the third ventricle (Fig. 147). IN anterior section the thalamus narrows and ends with the anterior tubercle, tuberculum anterius thalami [ thalamicum]. The rear end is thickened and is called... under the head, pulvinar. Only two surfaces of the thalamus are free: the medial one, facing the third ventricle and forming its lateral wall, and the upper one, which takes part in the formation of the bottom of the central part of the lateral ventricle.

The superior surface is separated from the medial white thin medullary stripe of the thalamus, stria medullaris thaldmi-sa. The medial surfaces of the posterior thalami of the right and left are connected to each other by interthalamic fusion, adhesio interthaldmica. The lateral surface of the thalamus is adjacent to the internal capsule. 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 (Fig. 148). These clusters are separated by thin layers white matter. Currently, there are up to 40 cores that perform various functions. The main nuclei of the thalamus are front,nuclei anteriores; medial,nuclei mediales, rear,nuclei posteriores. The processes of nerve cells of the second (conductor) neurons of all sensory pathways (with the exception of olfactory, gustatory and auditory) come into contact with the nerve cells of the thalamus. In this regard, the thalamus is actually a subcortical sensory center. Some of the processes of thalamic neurons are directed to the nuclei of the striatum of the telencephalon (in this regard, the thalamus is considered as a sensitive center of the extrapyramidal system), and some - thalamocortical bundles,fasciculi thalamocortica- les, - to the cerebral cortex. Below the thalamus is the so-called subthalamic region,regio subthaldmica (BNA), which continues downward into the tegmentum of the cerebral peduncle. This is a small area of ​​the medulla, separated from the thalamus on the side of the third ventricle by the hypothalamic groove. The red nucleus and black matter midbrain. Placed on the side of the black substance subthalamic nucleus(Lewis body), nucleus subthaldmicus.

Metathalamus(zathalamic area), tnetathdla- mus, represented by the lateral and medial geniculate bodies - paired formations. These are oblong-oval bodies connected to the colliculi of the midbrain roof with the help of the handles of the superior and inferior colliculi. Lateral geniculate body corpus geniculatum later, located near the inferolateral surface of the thalamus, on the side of the pillow. It can be easily detected by following the optic tract, the fibers of which are directed to the lateral geniculate body.

Somewhat inward and posterior to the lateral geniculate body, under the pillow, is the medial geniculate body, corpus geniculatum mediale, 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), epithdla- mus, includes the pineal body (see “Pineal body”), which, with the help of leashes, habenulae, connects to the medial surfaces of the right and left thalami. At the places where the leashes transition into the thalami there are triangular extensions - triangular extensions of the leash, trigdnum habenulae. The anterior sections of the leashes, before entering the pineal gland, form a commissure of the leashes, comissura habenuldrum. In front and below the pineal body there is a bundle of transversely running fibers - the epithalamic commissure, commissura epithalamica. Between the epithalamic commissure and the commissure of the leashes, a shallow blind pocket protrudes into the anterosuperior part of the pineal body, into its base, the pineal recess.

12.1. GENERAL INFORMATION ABOUT THE BUILDING

DENAMERABRAIN

Diencephalon (diencephalon) located between the cerebral hemispheres. The bulk of it consists thalamus (thalami, visual cusps). In addition, it includes structures located behind the thalamus, above and below them, constituting, respectively, metathalamus (metathalamus, foreign countries), epithalamus (epithalamus, epithalamus) and hypothalamus (hypothalamus, hypothalamus).

The epithalamus (epithalamus) includes the pineal gland (epiphysis). The pituitary gland is connected to the hypothalamus (subthalamus). The diencephalon also includes optic nerves, optic chiasm And optic tracts - structures included in the composition visual analyzer. The cavity of the diencephalon is the third ventricle of the brain - the remnant of the cavity of the primary forebrain bladder, from which this part of the brain is formed in the process of ontogenesis.

III ventricle of the brain It is represented by a narrow cavity located in the center of the brain between the thalami, in the sagittal plane. Through the interventricular foramen (foramen interventriculare, foramen of Monroe), it communicates with the lateral ventricles, and through the cerebral aqueduct with the fourth cerebral ventricle. The upper wall of the third ventricle consists of the fornix (fornix) and the corpus callosum (corpus callosum), and in the back part there are foreign formations. Its anterior wall is formed by the legs of the fornix, delimiting the interventricular foramina in front, as well as the anterior medullary commissure and the terminal plate. The lateral walls of the third ventricle make up the medial surfaces of the thalami; in 75% of them they are connected to each other by interthalamic fusion (adhesio interthalamica, or massa intermedia). The lower parts of the lateral surfaces and the bottom of the third ventricle consist of formations belonging to the hypothalamic part of the diencephalon.

12.2. THALAMUS

The thalami, or visual thalamus, are located on the sides of the third ventricle and make up up to 80% of the mass of the diencephalon. They are ovoid in shape with an approximate volume of 3.3 cubic meters. cm and consist of cellular

clusters (nuclei) and layers of white matter. Each thalamus has four surfaces: internal, external, superior and inferior.

The inner surface of the thalamus forms the lateral wall of the third ventricle. It is separated from the underlying hypothalamus by a shallow hypothalamic groove (sulcus hypothalamicus), going from the interventricular foramen to the entrance to the cerebral aqueduct. The inner and upper surfaces are separated by the medullary stripe (stria medullaris thalami). The upper surface of the thalamus, like the inner one, is free. It is covered by the fornix and the corpus callosum, with which it has no fusions. In the anterior part of the superior surface of the thalamus is its anterior tubercle, which is sometimes called the eminence of the anterior nucleus. The posterior end of the thalamus is thickened - this is the so-called thalamic cushion (pulvinar). The outer edge of the upper surface of the thalamus approaches the caudate nucleus, from which it is separated by the border strip (stria terminalis).

A vascular groove runs along the upper surface of the thalamus in an oblique direction, which is occupied by the choroid plexus of the lateral ventricle. This groove divides the superior surface of the thalamus into outer and inner parts. The outer part of the upper surface of the thalamus is covered with the so-called attached plate, which makes up the bottom of the central section of the lateral ventricle of the brain.

The outer surface of the thalamus is adjacent to the internal capsule, separating it from the lenticular nucleus and the head of the caudate nucleus. Behind the thalamic cushion are the geniculate bodies, which belong to the metathalamus. The rest of the lower side of the thalamus is fused with the formations of the hypothalamic region.

The thalami are located along the ascending tracts that run from the spinal cord and brain stem to the cerebral cortex. They have numerous connections with the subcortical ganglia, passing mainly through the loop of the lenticular nucleus (ansa lenticularis).

The thalamus consists of cellular clusters (nuclei), delimited from each other by layers of white matter. Each nucleus has its own afferent and efferent connections. Neighboring nuclei form groups. There are: 1) anterior nuclei (nucll. anteriores)- have reciprocal connections with the mastoid body and fornix, known as the mastoid-thalamic fascicle (Vic d'Azir fascicle) with the cingulate gyrus, related to the limbic system; 2) posterior nuclei, or nuclei of the tubercle cushion (nucll. posteriores)- associated with the associative fields of the parietal and occipital regions; play important role in integration various types sensory information coming here; 3) dorsal lateral nucleus (nucl. dorsolateralis)- receives afferent impulses from the globus pallidus and projects them into the caudal parts of the cingulate gyrus; 4) ventrolateral nuclei (nucll. ventrolaterales)- the largest specific nuclei are the collector of most somatosensory pathways: the medial lemniscus, spinothalamic tracts, trigeminothalamic and gustatory tracts, along which impulses of deep and superficial sensitivity pass, etc.; from here, nerve impulses are sent to the cortical projection somatosensory zone of the cortex (fields 1, 2, 3a and 3b, according to Brodmann); 5) medial nuclei (nucll. mediales)- associative, receive afferent impulses from the ventral and intralaminar thalamic nuclei, hypothalamus, midbrain nuclei and globus pallidus; efferent pathways from here they are sent to the associative areas of the prefrontal cortex located in front

motor area; 6) intralamellar nuclei (intralaminar nuclei, nucll. intralaminares) - constitute the main part of the nonspecific projection system of the thalamus; They receive afferent impulses partly through the ascending fibers of the reticular formation of the nerve trunk, partly through fibers starting from the nuclei of the thalamus. The pathways emanating from these nuclei are sent to the caudate nucleus, putamen, globus pallidus, which belong to the extrapyramidal system, and, probably, to other nuclear complexes of the thalamus, which then send them to the secondary associative zones of the cerebral cortex. An important part of the intralaminar complex is the central nucleus of the thalamus, which represents the thalamic section of the ascending reticular activating system.

The thalami are a kind of collector of sensory pathways, a place in which all the pathways conducting sensory impulses coming from the opposite half of the body are concentrated. In addition, olfactory impulses enter its anterior nucleus through the mastoid-thalamic fascicle; taste fibers (axons of second neurons located in the solitary nucleus) end in one of the nuclei of the ventrolateral group.

Thalamic nuclei that receive impulses from strictly defined areas of the body and transmit these impulses to the corresponding limited areas of the cortex (primary projection zones) are called projection, specific or switching nuclei. These include the ventrolateral nuclei. The switching nuclei for visual and auditory impulses are located, respectively, in the lateral and medial geniculate bodies, adjacent to the posterior surface of the visual tuberosities and constituting the bulk of the thalamus.

The presence in the projection nuclei of the thalamus, primarily in the ventrolateral nuclei, of a certain somatotopic representation makes it possible, with a pathological focus in the thalamus limited in volume, to develop a sensitivity disorder and associated motor disorders in any limited part of the opposite half of the body.

Associative nuclei, receiving sensitive impulses from switching nuclei, they are subjected to partial generalization - synthesis; as a result, impulses are sent from these thalamic nuclei to the cerebral cortex, already complicated due to the synthesis of information arriving here. Hence, The thalamus is not only an intermediate switching center, but can also be a place for partial processing of sensitive impulses.

In addition to the switching and associative nuclei, the thalamus contains, as already mentioned, intralaminar (parafascicular, middle and medial, central, paracentral nuclei) and reticular nuclei, having no specific function. They are considered as part of the reticular formation and are combined under the name nonspecific diffuse thalamic system. Being associated with the cerebral cortex and the structures of the limbic-reticular complex. This system takes part in the regulation of tone and in the “tuning” of the cortex and plays a certain role in the complex mechanism of the formation of emotions and the corresponding expressive involuntary movements, facial expressions, crying and laughter.

Thus, to the thalami afferent pathways information from almost all receptor zones converges. This information is subject to significant processing. From here, only

part of it, the other and probably the majority takes part in the formation of unconditioned and, possibly, some conditioned reflexes, the arcs of which are closed at the level of the thalamus and formations of the striopallidal system. The thalami are the most important part of the afferent part reflex arcs, causing instinctive and automated motor acts, in particular habitual locomotor movements (walking, running, swimming, cycling, skating, etc.).

Fibers going from the thalamus to the cerebral cortex take part in the formation of the posterior femur of the internal capsule and the corona radiata and form the so-called radiation of the thalamus - anterior, middle (upper) and posterior. The anterior radiate connects the anterior and partly the internal and external nuclei with the cortex of the frontal lobe. The middle radiation of the thalamus - the widest - connects the ventrolateral and medial nuclei with the posterior parts of the frontal lobe, with the parietal and temporal lobes of the brain. The posterior radiation consists mainly of optic fibers (radiatio optica, or Graziole's bundle), going from the subcortical visual centers to the occipital lobe, to the cortical end of the visual analyzer, located in the area of ​​the calcarine sulcus (fissura calcarina). The corona radiata also contains fibers that carry impulses from the cerebral cortex to the thalamus (corticothalamic connections).

The complexity of the organization and variety of functions of the thalamus determines the polymorphism of possible clinical manifestations his defeat. Damage to the ventrolateral part of the thalamus usually leads to an increase in the sensitivity threshold on the side opposite to the pathological focus, while the affective coloring of pain and temperature sensations changes. The patient perceives them as difficult to localize, diffuse, and having an unpleasant, burning tint. Characteristic in the corresponding part of the opposite half of the body is hypalgesia in combination with hyperpathy, with a particularly pronounced disorder of deep sensitivity, which can lead to clumsiness of movements and sensory ataxia.

With damage to the posterolateral part of the thalamus, the so-called thalamic Dejerine-Roussy syndrome[described in 1906 by French neurologists J. Dejerine (1849-1917) and G. Roussy (1874-1948)], including burning, painful, sometimes unbearable thalamic pain in the opposite half of the body in combination with a violation of superficial and especially deep sensitivity, pseudoasteriognosis and sensitive hemiataxia, the phenomena of hyperpathia and dysesthesia. Thalamic syndrome Dezherina-Roussi more often occurs when an infarct focus develops in it due to the development of ischemia in the lateral arteries of the thalamus (aa. thalamic laterales)- branches of the posterior cerebral artery. Sometimes, on the side opposite to the pathological focus, transient hemiparesis occurs and homonymous hemianopsia develops. Sensitive hemiataxia and pseudoastriognosis can be a consequence of deep sensitivity disorder. In case of damage to the medial part of the thalamus, the dentate-thalamic tract, along which impulses from the cerebellum pass to the thalamus, and rubrothalamic connections on the side opposite the pathological focus, ataxia appears in combination with athetoid or choreoathetoid hyperkinesis, usually especially pronounced in the hand and fingers (“thalamic” hand). In such cases, there is a tendency to fix the hand in a certain position: the shoulder is pressed to the body, the forearm and hand are bent and pronated, the main phalanges of the fingers

are bent, the rest are straightened. At the same time, the fingers make slow, elaborate movements of an athetoid nature.

The arterial blood supply to the thalamus involves the posterior cerebral artery, posterior communicating artery, anterior and posterior villous arteries.

12.3. METATALAMUS

Metathalamus (metathalamus, subcutaneous) constitute the medial and lateral geniculate bodies, located under the posterior part of the thalamic cushion, above and lateral to the superior colliculi of the quadrigeminal.

Medial geniculate body (corpus geniculatum medialis)contains the cell nucleus in which the lateral (auditory) loop ends. Nerve fibers constituting the inferior handle of the quadrigeminal (brachium colliculi inferioris), it is connected with the lower colliculi of the quadrigeminal and together with them forms subcortical auditory center. Axons of cells embedded in the subcortical auditory center, mainly in the medial geniculate body, are directed to the cortical end of the auditory analyzer, located in the superior temporal gyrus, more precisely in the cortex of Heschl’s small gyri located on it (fields 41, 42, 43, according to Brodmann), while auditory impulses are transmitted to the projection auditory the cortical field in tonotopic order. Damage to the medial geniculate body leads to hearing loss, which is more pronounced on the opposite side. Damage to both medial geniculate bodies can cause deafness in both ears.

If the medial part of the metathalamus is damaged, a clinical picture may appear Frankl-Hochwart syndrome, which is characterized by bilateral hearing loss, increasing and leading to deafness, and ataxia, combined with upward gaze paresis, concentric narrowing of the visual fields and signs of intracranial hypertension. This syndrome was described by the Austrian neuropathologist L. Frankl-Chochwart (1862-1914) for a tumor of the pineal gland.

Lateral geniculate body (corpus geniculatum laterale), as well as the upper tubercles of the quadrigeminal, with which it is connected by the upper handles of the quadrigeminal (brachii colliculi superiores), consists of alternating layers of gray and white matter. The lateral geniculate bodies make up subcortical visual center. Mainly the optic tracts end in them. The axons of the cells of the lateral geniculate bodies pass compactly as part of the posterior part of the posterior femur of the internal capsule, and then form the optic radiation (radiatio optica), along which visual impulses reach the cortical end of the visual analyzer in a strict retinotopic order - mainly the area of ​​the calcarine groove on the medial surface of the occipital lobe (field 17, according to Brodman).

Issues related to the structure, function, methods of examining the visual analyzer, as well as the significance of the pathology revealed during its examination for topical diagnostics should be discussed in more detail, since many structures that make up the visual system are directly related to the diencephalon and in the process of ontogenesis they are formed from the primary forebrain.

12.4. VISUAL ANALYZER

12.4.1. Anatomical and physiological basis of vision

Light rays carrying information about the surrounding space pass through the refractive media of the eye (cornea, lens, vitreous) and affect the receptors of the visual analyzer located in the retina of the eye; in this case, the image of visible space is projected onto the retina in an inverted form.

Visual receptors (light energy receptors) are neuroepithelial formations known as rods and cones, which provide light-induced photochemical reactions that convert light energy into nerve impulses. In the retina of the human eye there are about 7 million cones and approximately 150 million rods. Cones have the highest resolution and provide mainly daytime and color vision. They are concentrated mainly in a region of the retina known as the macula, or macula. The spot occupies approximately 1% of the retinal area.

Rods and cones are regarded as specialized neuroepithelium, similar to the ependymal cells lining the ventricles of the brain. This light-sensitive neuroepithelium is located in one of the outer layers of the retina, in the area macular spot, in the fossa located in its center, a particularly large number of cones are concentrated, which makes it the place of the most clear vision. Impulses arising in the outer layer of the retina reach intermediate neurons located in the inner layers of the retina, mainly bipolar neurons, and then ganglion nerve cells. The axons of ganglion cells converge radially to one part of the retina, located medial to the spot, and form the optic disc, in fact, its initial segment.

optic nerve, n. opticus(II cranial nerve) consists of axons of ganglion cells of the retina, exits from eyeball close to its posterior pole, passes through the retrobulbar tissue. The retrobulbar (orbital) part of the optic nerve, located within the orbit, is about 30 mm long. The optic nerve here is covered by all three meninges: dura, arachnoid and soft. Next, it leaves the orbit through the optic foramen located in its depth and penetrates the middle cranial fossa (Fig. 12.1).

The intracranial part of the optic nerve is shorter (from 4 to 17 mm) and is covered only with soft meninges. The optic nerves, approaching the diaphragm of the sella turcica, come together and form an incomplete optic chiasm (chiasma opticum).

In the chiasm, only those fibers of the optic nerves cross over, which transmit impulses from the inner halves of the retina of the eyes. The axons of ganglion cells located in the lateral halves of the retina do not undergo decussation and, passing through the chiasma, only bend around the outside of the fibers involved in the formation of the decussation, constituting its lateral sections. Nerve fibers carrying visual information from the macula make up about 1/3 of the fibers of the optic nerve; passing as part of the chiasm, they also make a partial crossover, dividing into crossed and

Rice. 12.1.Visual analyzer and reflex arc pupillary reflex. 1 - retina; 2 - optic nerve; 3 - chiasma; 4 - visual tract; 5 - cells of the external geniculate body; 6 - visual radiance (Graziole beam); 7 - cortical projection visual zone - calcarine groove; 8 - anterior colliculus; 9 - nuclei of the oculomotor (III) nerve; 10 - autonomic part of the oculomotor (III) nerve; 11 - ciliary node.

straight fibers of the macular bundle. The blood supply to the optic nerves and chiasm is provided by branches of the ophthalmic artery (a. ophthalmica).

Having passed through the chiasm, the axons of the ganglion cells form two visual tracts, each of which consists of nerve fibers carrying impulses from the same halves of the retinas of both eyes. The visual tracts run along the base of the brain and reach the external geniculate bodies, which are the subcortical visual centers. The axons of the retinal ganglion cells end there, and the impulses are switched to the next neurons. The axons of the neurons of each lateral geniculate body pass through the pars reticulum (pars retrolenticularis) internal capsule and form visual radiance (radiatio optica), or the Graziole bundle, which is involved in the formation of white matter in the temporal and, to a lesser extent, parietal lobes of the brain, then in its occipital lobe and ends at the cortical end of the visual analyzer, i.e. in the primary visual cortex, located mainly on the medial surface of the occipital lobe in the area of ​​the calcarine sulcus (area 17, according to Brodmann).

It should be emphasized that throughout the visual pathways from the optic disc to the projection zone in the cerebral cortex, visual fibers are located in a strict retinotopic order.

The optic nerve is fundamentally different from the cranial nerves at the brainstem level. This, in fact, is not even a nerve, but a cerebral cord pushed forward to the periphery. The fibers that make it up do not have the characteristic peripheral nerve Schwann's sheath, distal to the exit site of the optic nerve of the eyeball, it is replaced by the myelin sheath, which is formed from the sheath of oligodendrocytes adjacent to the nerve fibers. This structure of the optic nerves is understandable if we consider that in the process of ontogeny

behind the optic nerves are formed from the stems (legs) of the so-called optic vesicles, which are protrusions of the anterior wall of the primary anterior medullary vesicle, which are subsequently transformed into the retina of the eyes.

12.4.2. Research of the visual analyzer

In neurological practice, the most significant information is about visual acuity (visus), the state of the visual fields and the results of ophthalmoscopy, during which it is possible to examine the fundus and visualize the optic nerve head. If necessary, fundus photography is also possible.

Visual acuity.Visual acuity testing is usually carried out according to special tables by D.A. Sivtsev, consisting of 12 lines of letters (for the illiterate - open rings, for children - contour drawings). A normally seeing eye at a distance of 5 m from a well-lit table clearly differentiates the letters that make up its 10th line. In this case, vision is considered normal and is conventionally taken as 1.0 (visus = 1.0). If the patient distinguishes only the 5th line at a distance of 5 m, then visus = 0.5; if it reads only the 1st row of the table, then visus = 0.1, etc. If the patient at a distance of 5 m does not differentiate the images included in the 1st line, then you can bring him closer to the table until he begins to distinguish the letters or drawings that make it up. Due to the fact that the strokes with which the letters of the first line are drawn have a thickness approximately equal to the thickness of a finger, when checking the vision of the visually impaired, the doctor often shows them the fingers of his hand. If the patient distinguishes the doctor’s fingers and can count them at a distance of 1 m, then the visus of the examined eye is considered equal to 0.02, if it is possible to count fingers only at a distance of 0.5 m, visus = 0.01. If the visus is even lower, then the patient distinguishes the fingers of the examiner only when the fingers are brought even closer, then they usually say that he is “counting the fingers in front of his face.” If the patient does not distinguish fingers even at a very close distance, but points to the light source, they say that he has a correct or incorrect projection of light. In such cases, visus is usually denoted by the fraction 1/b , which means: visus is infinitesimal.

" infinity"

When assessing visual acuity, if for some reason visus is determined not from a distance of 5 m, you can use Snellen’s formula: V = d/D, where V is visus, d is the distance from the eye being examined to the table, and D is the distance from which the strokes , the constituent letters are distinguishable at an angle of 1", - this indicator is indicated at the beginning of each line of Sivtsev’s table.

Visus should always be determined for each eye separately, while the other eye is covered. If the examination reveals a decrease in visual acuity, then it is necessary to find out whether it is a consequence of a purely ophthalmological pathology, in particular refractive error. In the process of checking visual acuity, if the patient has a refractive error (myopia, hyperopia, astigmatism), it is necessary to correct it using spectacle glasses. Therefore, a patient who usually wears glasses should wear them when testing visual acuity.

Decreased vision is designated by the term “amblyopia”, blindness - “amaurosis”.

Line of sight.Each eye sees only part of the surrounding space - a field of vision, the boundaries of which are at a certain angle from the optical axis of the eye. A.I. Bogoslovsky (1962) gave this space the following definition: “The entire field that the eye simultaneously sees, fixing with a fixed gaze and with a stationary position of the head a certain point in space, constitutes its field of vision.” The part of space visible to the eye, or the field of view, can be outlined on coordinate axes and additional diagonal axes, while converting angular degrees into linear units of measurement. Normally, the outer limit of the visual field is 90?, the upper and inner - 50-60?, the lower - up to 70?. In this regard, the field of view shown on the graph has the shape of an irregular ellipse, elongated outward (Fig. 12.2).

Field of view, same as visus, is checked for each eye separately. The second eye is covered during the examination. To study the field of view use perimeter, the first version of which was proposed in 1855 by the German ophthalmologist A. Grefe (1826-1870). There are various versions of it, but in most cases each of them has a graduated arc rotating around the center with two marks, one of which is stationary and located in the center of the arc, the other moves along the arc. The first mark serves

Rice. 12.2.Normal field of view.

The dotted line shows the field of view for white, and the colored lines show the corresponding colors.

for fixing the examined eye on it, the second, movable one, for determining the boundaries of its field of vision.

At neurological pathology can be various shapes narrowing of visual fields, in particular by concentric type and by type hemianopsia (loss of half the visual field), or quadrant hemianopia (loss of the upper or lower part of the visual field). In addition, during perimetry or campimetry 1, scotomas - areas of the visual field invisible to patients. It is necessary to keep in mind the obligatory presence in the field of vision of a healthy eye of a small physiological scotoma (blind spot) at 10-15? lateral from the center of the field, which is a projection of the area of ​​the fundus occupied by the optic nerve head and therefore devoid of photoreceptors.

An approximate idea of ​​the state of the visual fields can be obtained by asking the patient to fix the eye being examined at a certain point located in front of it, and then introduce an object into or out of the visual field, identifying the moment when this object becomes visible or disappears. The boundaries of the field of view in such cases are, of course, determined approximately.

Loss of the same (right or left) halves of the visual fields (homonymous hemianopsia) can be identified by asking the patient, looking in front of him, to divide in half a towel unfolded in front of him in the horizontal plane (test with a towel). If a patient has hemianopsia, he divides in half only the part of the towel that is visible to him and, therefore, it is divided into unequal sections (with complete homonymous heminanopsia, their ratio is 1:3). The towel test can be tested, in particular, with a patient in a horizontal position.

Optic disc. The condition of the fundus of the eye, in particular the optic nerve head, is revealed by examining it with an ophthalmoscope. Ophthalmoscopes can be of different designs. The simplest is a mirror ophthalmoscope, consisting of a reflector mirror that reflects a beam of light onto the retina. In the center of this mirror there is a small hole through which the doctor examines the retina of the eye. To enlarge its image, use a 13 or 20 diopter magnifying glass. The magnifying glass is a biconvex lens, so the doctor sees through it an inverted (reverse) image of the area of ​​the retina being examined.

Direct non-reflex electric ophthalmoscopes are more advanced. Large non-reflex ophthalmoscopes make it possible not only to examine, but also to photograph the fundus of the eye.

Normally, the optic disc is round, pink, and has clear boundaries. Arteries (branches of the central retinal artery) diverge from the center of the optic disc in a radial direction, and retinal veins converge towards the center of the disc. The diameters of arteries and veins normally have a 2:3 ratio.

The fibers coming from the macula and providing central vision enter the optic nerve from the temporal side and, only after traveling a certain distance, they move to the central part of the nerve. Atrophy macular, i.e. coming from yellow spot, fibers causes a characteristic paleness of the temples

1 Method for identifying scotomas; consists of recording the perception by a fixed eye of objects moving along a black surface located in the frontal plane at a distance of 1 m from the eye under study.

no half of the optic nerve head, which can be combined with deterioration of central vision, while peripheral vision remains intact (a possible variant of visual impairment, in particular, with exacerbation of multiple sclerosis). When the peripheral fibers of the optic nerve are damaged in the extraorbital zone, a concentric narrowing of the visual field is characteristic.

When the axons of ganglion cells are damaged along any part of their path to the chiasm (optic nerve), degeneration of the optic disc occurs over time, called in such cases primary optic disc atrophy. The optic disc retains its size and shape, but its color fades and may become silvery-white, and its vessels become empty.

With damage to the proximal parts of the optic nerves and especially the chiasm, signs of primary disc atrophy develop later, while the atrophic process gradually spreads in the proximal direction - descending primary atrophy. Defeat of the chiasm and vision body tract can lead to a narrowing of the visual fields, while damage to the chiasm in most cases is accompanied by partial or complete heteronymous hemianopia. With complete damage to the chiasm or bilateral total damage to the optic tracts, blindness and primary atrophy of the optic discs should develop over time.

If the patient’s intracranial pressure increases, then the venous and lymphatic outflow from the optic nerve head is disrupted, which leads to the development of signs of stagnation in it (stagnant optic disc). At the same time, the disc swells, increases in size, its boundaries become blurred, and the edematous tissue of the disc can withstand the vitreous body. The arteries of the optic nerve head narrow, while the veins turn out to be dilated and congested with blood, tortuous. With pronounced symptoms of stagnation, hemorrhages into the tissue of the optic nerve are possible. The development of congestive optic discs in intracranial hypertension is preceded by an increase in the blind spot detected by campimetry (Fedorov S.N., 1959).

Stagnant optic discs, if the cause of intracranial hypertension is not eliminated, over time can pass into a state of secondary atrophy, while their size gradually decreases, approaching normal, the boundaries become clearer, and the color becomes pale. In such cases, they speak of the development of optic disc atrophy after stagnation or secondary atrophy of the optic discs. The development of secondary atrophy of the optic discs in a patient with severe intracranial hypertension is sometimes accompanied by a decrease in hypertensive headache, which can be explained by the parallel development degenerative changes in the receptor apparatus of the meninges and other tissues located in the cranial cavity.

The ophthalmoscopic picture of congestion in the fundus and optic neuritis has many common features, but with congestion, visual acuity for a long time (for several months) can remain normal or close to normal and decreases only with the development of secondary atrophy of the optic nerves, and with optic neuritis, visual acuity vision declines acutely or subacutely and very significantly, up to blindness.

12.4.3. Feature Changes visual system with damage to its various parts

Damage to the optic nerve leads to dysfunction of the eye on the side of the pathological focus, with a decrease in visual acuity, a narrowing of the visual field, often of a concentric type, sometimes pathological scotomas are detected, over time, signs of primary descending atrophy of the optic disc appear, the increase of which is accompanied by a progressive decrease visual acuity, and blindness may develop. It must be borne in mind that the more proximally the area of ​​damage to the optic nerve is located, the later the atrophy of its disc occurs.

In case of damage to the optic nerve, leading to blindness of the eye, the afferent part of the arc of the pupillary reflex to light turns out to be incompetent, and therefore the direct reaction of the pupil to light is impaired, while the conjugate reaction of the pupil to light is preserved. Due to the absence of a direct reaction of the pupil to light (its narrowing under the influence of increasing illumination), it is possible anisocoria, since the pupil of a blind eye, which does not react to light, does not narrow with increasing illumination.

Acute unilateral vision loss in young patients, if not due to damage to the retina, is most likely a consequence of demyelination of the optic nerve (retrobulbar neuritis). In elderly patients, decreased vision may be due to circulatory disorders in the retina or optic nerve. With temporal arteritis, ischemic retinopathy is possible, and a high ESR is usually detected; Diagnosis can be facilitated by the results of a biopsy of the wall of the external temporal artery.

In case of subacute visual impairment, on the one hand, one must keep in mind the possibility of the presence oncological pathology, in particular tumors of the optic nerve or tissues close to it. In this case, it is advisable to examine the condition of the orbit, optic nerve canal, and chiasm area using craniography, CT and MRI.

The cause of acute or subacute bilateral vision loss may be toxic optic neuropathy, in particular methanol poisoning.

Damage to the optic chiasm leads to bilateral visual field impairment and may also cause a decrease in visual acuity. Over time, in connection with descending atrophy of the optic nerves, in such cases, primary descending atrophy of the optic discs develops, while the course and nature of visual dysfunction depend on the primary localization and rate of damage to the chiasm. If the central part of the chiasm is affected, which often happens when it is compressed by a tumor, usually a pituitary adenoma, then the fibers crossing in the chiasm, coming from the inner halves of the retinas of both eyes, are first damaged. The inner halves of the retinas become blind, which leads to loss of the temporal halves of the visual fields - develops bitemporal hemianopsia, in which the patient, looking forward, sees that part of the space that is in front of him, and does not see what is happening on the sides. Pathological effects on the outer parts of the chiasm lead to loss of the inner halves of the visual fields - to binasal hemianopsia(Fig. 12.3).

Rice. 12.3.Changes in visual fields with damage to various parts of the visual analyzer (according to Homans).

a - with damage to the optic nerve, blindness on the same side; b - damage to the central part of the chiasm - bilateral hemianopsia on the temporal side (bitemporal hemianopsia); c - damage to the outer parts of the chiasm on one side - nasal hemianopia on the side of the pathological focus; d - damage to the optic tract - changes in both fields of vision according to the type of homonymous hemianopsia on the side opposite to the lesion; d, f - partial defeat visual radiance - upper or lower quadrant hemianopsia on the opposite side; g - damage to the cortical end of the visual analyzer (calcarine sulcus of the occipital lobe) - on the opposite side there is homonymous hemianopsia with preservation of central vision.

Visual field defects caused by compression of the chiasm may be a consequence of the growth of a craniopharyngioma, pituitary adenoma or meningioma of the tubercle of the sella, as well as compression of the chiasm arterial aneurysm. In order to clarify the diagnosis, in case of changes in the visual fields characteristic of chiasm lesions, craniography, CT or MRI scanning are indicated, and if the development of an aneurysm is suspected, an angiographic study is indicated.

Total defeat of the chiasm leads to bilateral blindness, while direct and friendly reactions of the pupils to light are lost. In the fundus of the eye on both sides, due to the descending atrophic process, signs of primary atrophy of the optic discs develop over time.

In the case of damage to the optic tract on the opposite side, incongruent (non-identical) homonymous hemianopsia usually occurs on the side opposite the pathological focus. Over time, signs of partial primary (descending) atrophy of the optic discs appear in the fundus, mainly on the side of the lesion. The possibility of atrophy of the optic discs is associated with the fact that the optic tracts are made up of axons that participate in the formation of the optic discs and are processes of ganglion cells located in the retina of the eyes. The cause of damage to the optic tract may be a basal pathological process (basal meningitis, aneurysm, craniopharyngioma, etc.).

Damage to the subcortical visual centers, primarily the lateral geniculate body, also causes homonymous incongruent hemianoptic, or sectoral loss of visual fields on the side opposite to the pathological focus, and the pupillary reactions to light usually change. Such disorders are possible, in particular, in case of circulatory disorders in the anterior villous artery basin (a. chorioidea anterior, branch internal carotid artery) or in the basin of the posterior villous artery (a. chorioidea posterior, branch of the posterior cerebral artery), providing blood supply to the lateral geniculate body.

Dysfunction of the visual analyzer behind the lateral geniculate body - the lenticular part of the internal capsule, the optic radiation (Graziole's bundle) or the projection visual zone (cortex of the medial surface of the occipital lobe in the area of ​​the calcarine sulcus, area 17, according to Brodmann) also leads to complete or incomplete homonymous hemianopsia on the side opposite to the pathological focus, while hemianopsia is usually congruent. In contrast to homonymous hemianopsia with damage to the optic tract, in the case of damage to the internal capsule, optic radiation or the cortical end of the visual analyzer, homonymous hemianopsia does not lead to atrophic changes on the fundus and changes in pupillary reactions, since in such cases, visual impairment is caused by the presence of a lesion located behind the subcortical visual centers and a zone of closure of the reflex arcs of pupillary reactions to light.

Optic radiance fibers are arranged in a strict order. Its lower part, passing through the temporal lobe of the brain, consists of fibers carrying impulses from the lower parts of the same halves of the retinas. They end in the cortex of the lower lip of the calcarine groove. When they are affected, the upper parts of the halves of the visual fields opposite the pathological focus fall out or one of the varieties occurs quadrant hemianopsia, in this case - upper quadrant hemianopsia on the side opposite to the pa-

tological focus. If the upper parts of the optic radiation are affected (beams passing partially through parietal lobe and going to upper lip calcarine groove on the side opposite to the pathological process) lower quadrant hemianopsia occurs.

When the cortical end of the visual analyzer is damaged, the patient is usually not aware of the defect in the visual fields (unconscious homonymous hemianopia occurs), while dysfunction of any other part of the visual analyzer leads to a defect in the visual fields, which are recognized by the patient (conscious hemianopsia). In addition, with unconscious cortical hemianopia, vision is preserved in the area of ​​projection of the macular beam onto it.

With irritation caused by a pathological process of the cortical end of the visual analyzer, hallucinations in the form of flickering dots, circles, sparks, known as “simple photoms” or “photopsies,” may occur in the opposite halves of the visual fields. Photopsia are often a harbinger of an attack of the ophthalmic form of migraine and can constitute the visual aura of an epileptic seizure.

12.5. EPITHALAMUS

Epithalamus (epithalamus, epithalamus) can be considered as a direct continuation of the roof of the midbrain. The epithalamus usually includes the posterior epithalamic commissure (commissura epithalamica posterior), two leashes (habenulae) and their soldering (commissura habenularum), as well as the pineal gland (corpus pineale, pineal gland).

Epithalamic commissure located above the upper part of the cerebral aqueduct and is a commissural bundle of nerve fibers that originates from the nuclei of Darkshevich and Cajal. Anterior to this commissure is an unpaired pineal body, which has variable dimensions (its length does not exceed 10 mm) and the shape of a cone, with its apex facing backwards. The base of the pineal gland is formed by the inferior and superior medullary plates, which border the eversion of the pineal gland (recessus pinealis)- the protruding upper-posterior part of the third ventricle of the brain. The inferior medullary plate continues posteriorly and passes into the epithalamic commissure and the quadrigeminal plate. The anterior part of the superior cerebral plate passes into the commissure of the leashes, from the end of which the leashes extend forward, sometimes called the legs of the pineal gland. Each of the leashes stretches to the visual thalamus and, at the border of its upper and inner surfaces, ends in a triangular extension located above the small nucleus of the frenulum, already located in the substance of the thalamus. A white stripe stretches from the nucleus of the frenulum along the posterior surface of the thalamus - stria medullaris, consisting of fibers connecting the pineal gland with the structures of the olfactory analyzer. In this regard, there is an opinion that the epithalamus is related to the sense of smell.

Recently it has been established that parts of the epithalamus, mainly the pineal gland, produce physiologically active substances- serotonin, melatonin, adrenoglomerulotropin and antihypothalamic factor.

Pineal body represents a gland internal secretion. It has a lobular structure, its parenchyma consists of pineocytes, epithelial

nal and glial cells. The pineal body contains a large number of blood vessels; its blood supply is provided by branches of the posterior cerebral arteries. Confirms the endocrine function of the pineal gland and its high absorption capacity radioactive isotopes 32 P and 131 I. It absorbs more radioactive phosphorus than any other organ, and in terms of the amount absorbed radioactive iodine second only to the thyroid gland. Before puberty, the cells of the pineal gland secrete substances that inhibit the action of the pituitary gonadotropin hormone, and therefore delay the development of the reproductive system. This is confirmed by clinical observations of premature puberty in diseases (mainly tumors) of the pineal gland. There is an opinion that the pineal gland is in a state of antagonistic correlation with thyroid gland and adrenal glands and affects metabolic processes, in particular on vitamin balance and autonomic function nervous system.

The deposition of calcium salts in the pineal body observed after puberty has some practical significance. In this regard, on craniograms of adults, a shadow of the calcified pineal body is visible, which, with volumetric pathological processes(tumor, abscess, etc.) in the cavity of the supratentorial space can shift in the direction opposite to the pathological process.

12.6. HYPOTHALAMUS AND PITUITARY physis

Hypothalamus (hypothalamus) constitutes the lower, phylogenetically most ancient part of the diencephalon. The conventional border between the thalami and the hypothalamus passes at the level of the hypothalamic grooves, located on the lateral walls of the third ventricle of the brain.

The hypothalamus (Fig. 12.4) is conventionally divided into two parts: anterior and posterior. The posterior part of the hypothalamic zone includes the mastoid bodies located behind the gray tuberosity (corpora mammillaria) with adjacent areas of brain tissue. The anterior part includes the optic chiasm (chiasma opticum) and optic tracts (tracti optici), gray bump (tuber cinereum), funnel (infundibulum) and pituitary gland (hypophysis). The pituitary gland, connected to the gray tubercle through the infundibulum and the pituitary stalk, is located in the center of the base of the skull in the bone bed - the pituitary fossa of the sella turcica of the main bone. The diameter of the pituitary gland is no more than 15 mm, its weight is from 0.5 to 1 g.

The hypothalamic region consists of numerous cellular accumulations - nuclei and bundles of nerve fibers. Basic hypothalamic nuclei can be divided into 4 groups.

1. The anterior group includes the medial and lateral preoptic, supraoptic, paraventricular and anterior hypothalamic nuclei.

2. The intermediate group consists of the arcuate nucleus, gray tuberous nuclei, ventromedial and dorsomedial hypothalamic nuclei, dorsal hypothalamic nucleus, posterior paraventricular nucleus, and infundibulum nucleus.

3. The posterior group of nuclei includes the posterior hypothalamic nucleus, as well as the medial and lateral nuclei of the mastoid body.

4. The dorsal group includes the nuclei of the lenticular loop.

The nuclei of the hypothalamus have associative connections with each other and with other parts of the brain, in particular with frontal lobes, limbic structure-

Rice. 12.4.Sagittal section of the hypothalamus.

1 - paraventricular nucleus; 2 - mastoid-thalamic bundle; 3 - dorsomedial hypothalamic nucleus; 4 - ventromedial hypothalamic nucleus, 5 - pons; 6 - supraoptic pituitary tract; 7 - neurohypophysis; 8 - adenohypophysis; 9 - pituitary gland; 10 - visual chiasm; 11 - supraoptic core; 12 - preoptic nucleus.

mi cerebral hemispheres, various parts of the olfactory analyzer, thalamus, formations extrapyramidal system, reticular formation of the brain stem, nuclei of the cranial nerves. Most of these connections are bilateral. The nuclei of the hypothalamic region are connected to the pituitary gland passing through the infundibulum of the gray tuberosity and its continuation - the pituitary stalk - the hypothalamic-pituitary bundle of nerve fibers and a dense network of vessels.

Pituitary (hypophysis) is a heterogeneous formation. It develops from two different primordia. Front, large, his share (adenohypophysis) formed from the epithelium of the primary oral cavity or the so-called Rathke's pocket; it has a glandular structure. The posterior lobe consists of nerve tissue (neurohypophysis) and is a direct continuation of the funnel of the gray tubercle. In addition to the anterior and posterior lobes, the pituitary gland has a middle, or intermediate, lobe, which is a narrow epithelial layer containing vesicles (follicles) filled with serous or colloidal fluid.

Based on their function, the structures of the hypothalamus are divided into nonspecific and specific. Specific nuclei have the ability to release chemicals

compounds that have an endocrine function, regulating, in particular, metabolic processes in the body and maintaining homeostasis. The specific ones include the supraoptic and paraventricular nuclei, which are capable of neurocrinia and are connected to the neurohypophysis via the supraoptic-pituitary pathway. They produce the hormones vasopressin and oxytocin, which are transported via the mentioned pathway through the pituitary stalk to the neurohypophysis.

Vasopressin,or antidiuretic hormone (ADH), produced mainly by cells of the supraoptic nucleus, is very sensitive to changes in the salt composition of the blood and regulates water metabolism, stimulating water resorption in the distal nephrons. Thus, ADH regulates the concentration of urine. With a deficiency of this hormone due to damage to the mentioned nuclei, the amount of urine excreted with low relative density increases - develops diabetes insipidus, at which along with polyuria (up to 5 liters of urine or more) occurs strong thirst leading to consumption large quantity fluids (polydipsia).

OxytocinProduced by the paraventricular nuclei, it ensures contractions of the pregnant uterus and affects the secretory function of the mammary glands.

Besides, in specific nuclei of the hypothalamus, “releasing” factors (releasing factors) and “inhibiting” factors entering

from the hypothalamus to the anterior pituitary gland along the tubercular-pituitary tract (tractus tuberoinfundibularis) and portal vascular network pituitary stalk. Once in the pituitary gland, these factors regulate the secretion of hormones secreted by the glandular cells of the anterior pituitary gland.

adenohypophysis cells, producing hormones under the influence of releasing factors entering it are large and easily stained (chromophilic), while most of them are stained with acidic dyes, in particular eosin. They are called eosinophilic, or oxyphilic, or alpha cells. They make up 30-35% of all cells of the adenohypophysis and produce somatotropic hormone (STH), or growth hormone (GH), and prolactin (PRL). Cells of the adenohypophysis (5-10%), stained with alkaline (basic, basic) dyes, including hematoxylin, are called basophilic cells, or beta cells. They highlight adrenocorticotropic hormone (ACTH) and thyroid-stimulating hormone (TSH).

About 60% of adenohypophysis cells do not perceive paint well (chromophobe cells, or gamma cells) and do not have hormone secretory function.

The sources of blood supply to the hypothalamus and pituitary gland are the branches of the arteries that make up the arterial circle of the cerebrum (circulus arteriosis cerebri, circle of Willis), in particular the hypothalamic branches of the middle cerebral and posterior communicating arteries, while the blood supply to the hypothalamus and pituitary gland is extremely abundant. In 1 mm 3 of tissue of the gray matter of the hypothalamus, there are 2-3 times more capillaries than in the same volume of cranial nerve nuclei. The blood supply to the pituitary gland is represented by the so-called portal vascular system. The arteries extending from the arterial circle are divided into arterioles, then form a dense primary arterial network. The abundance of vessels in the hypothalamus and pituitary gland ensures the unique integration of the functions of the nervous, endocrine and humoral systems that occurs here. The vessels of the hypothalamic region and pituitary gland are highly permeable to various chemical and hormonal

blood ingredients, as well as protein compounds, including nucleoproteins, neurotropic viruses. This determines the increased sensitivity of the hypothalamic region to the effects of various harmful factors that enter the vascular bed, which is necessary at least to ensure their rapid removal from the body in order to maintain homeostasis.

Pituitary hormones are released into the bloodstream and hematogenously, reaching the appropriate targets. There is an opinion that they partially enter the cerebrospinal fluid pathways, primarily into the third ventricle of the brain.

The endocrine functions of the hypothalamus and pituitary gland are regulated by the nervous system. The hormones produced in them can be classified as ligands - biologically active substances, carriers of regulatory information. The targets for them are specialized receptors of organs and tissues. Therefore, hormones can be considered as a kind of mediators that can transmit information over long distances through the hematogenous route. In such cases, this path is considered as the humoral knee of complex reflex arcs that ensure activity individual organs and tissues on the periphery. By the way, information about the activity of these organs and tissues is sent to the structures of the central nervous system, in particular the hypothalamus, along the nerve afferent pathways, as well as through the hematogenous route, through which information about the degree of activity of various peripheral endocrine glands is transmitted from the periphery to the center (process reverse afferentation).

This interpretation of the role of hormones excludes ideas about the autonomy of the endocrine system and emphasizes the interconnection and interdependence of the endocrine glands and nervous tissue.

Hypothalamic structures regulate the functions of the sympathetic and parasympathetic parts of the autonomic nervous system and maintain vegetative balance in the body, while ergotropic and trophic zones can be distinguished in the hypothalamus (Hess W., 1881-1973).

Ergotropic system activates physical and mental activity, ensuring the activation of predominantly the sympathetic apparatus of the autonomic nervous system. The trophotropic system promotes the accumulation of energy, replenishment of expended energy resources, provides parasympathetic processes: tissue anabolism, reduction of heart rate, stimulation of the function of the digestive glands, reduction muscle tone etc.

Trophotropic zones are located mainly in the anterior parts of the hypothalamus, primarily in its preoptic zone, ergotropic ones - in the posterior parts, more precisely, in the posterior nuclei and lateral zone, which W. Hess called dynamogenic.

Differentiation of the functions of various parts of the hypothalamus has a functional and biological significance and determines their participation in the implementation of integral behavioral acts.

12.7. SYNDROMES OF DAMAGE TO THE HYPOTHALAMIC PITUITARY SYSTEM

The variety of functions of the hypothalamic-pituitary part of the diencephalon leads to the fact that when it is damaged, various

pathological syndromes, including neurological disorders of various nature, including signs endocrine pathology, manifestations of autonomic dysfunction, emotional imbalance.

Hypothalamic region ensures interaction between regulatory mechanisms that integrate the mental, primarily emotional, autonomic and hormonal spheres. Many processes that play an important role depend on the state of the hypothalamus and its individual structures. role in maintaining the body homeostasis. Thus, the preoptic area located in its anterior section provides thermoregulation due to changes in thermal metabolism. If this area is affected, the patient may not be able to give off heat in high ambient temperatures, which leads to overheating of the body and to hyperthermia, or so-called central fever. Damage to the posterior hypothalamus can lead to poikilothermia, in which the body temperature changes depending on the ambient temperature.

The lateral area of ​​the gray tuberosity is recognized "appetite center" and with the area where the ventromedial nucleus is located is usually associated feeling of fullness. When the “appetite center” is irritated, gluttony occurs, which can be suppressed by stimulating the satiety zone. Damage to the lateral nucleus usually leads to cachexia. Damage to the gray tuberosity can cause the development adiposogenital syndrome, or Babinski-Fröhlich syndrome

(Fig. 12.5).

An animal experiment showed that the gonadotropic center is localized in the infundibulum nucleus and the ventromedial nucleus and secretes gonadotropic hormone, while the inhibitory center of sexual function is localized anterior to the ventromedial nucleus. During the activity of these cellular structures, releasing factors affecting production by the pituitary gland

gonadotropic hormones.

The physicochemical properties of all tissues and organs, their trophism and, to some extent, their readiness to perform functions specific to them are dependent to a certain extent on the functional state of the hypothalamus. This also applies to nervous tissue, including the cerebral hemispheres. Some nuclei of the hypothalamic region function in close interaction with the reticular formation, and it is sometimes difficult to distinguish between their influence on physiological processes.

The activity of the cardiovascular and respiratory systems, the regulation of body temperature, the characteristics of various types of metabolism (water-salt, carbohydrate, fat, protein), the regulation of the work of the endocrine glands, the functions of the digestive tract are dependent to a certain extent on the state and functional activity of the hypothalamus.

Rice. 12.5.Adiposogenital syndrome.

tract, functional state genitourinary organs, in particular the implementation of complex sexual reflexes.

Autonomic dystonia may be a consequence of an imbalance in the activity of the trophotropic and ergotropic parts of the hypothalamus. Such imbalance is possible in practically healthy people during periods of endocrine changes (during puberty, during pregnancy, menopause). Due to the high permeability of the vessels supplying blood to the hypothalamic-pituitary region, infectious diseases, endogenous and exogenous intoxication may occur temporary or persistent vegetative imbalance, characteristic of the so-called neurosis-like syndrome. It is also possible that they arise against the background of vegetative imbalance vegetative-visceral disorders, manifested, in particular, by peptic ulcer disease, bronchial asthma, hypertension, as well as other forms of somatic pathology.

Particularly characteristic of damage to the hypothalamic part of the brain is the development of various forms of endocrine pathology. Among neuroendocrine-metabolic syndromes, a significant place is occupied by various forms of hypothalamic (cerebral) obesity (Fig. 12.6), while obesity is usually pronounced and fat deposition often occurs on the face, trunk and proximal extremities. Due to the uneven deposition of fat, the patient’s body often takes on bizarre shapes. With the so-called adiposogenital dystrophy (Babinski-Fröhlich syndrome), which may be a consequence of a growing tumor of the hypothalamic-pituitary region - craniopharyngiomas, already in the early childhood Obesity sets in, and during puberty, underdevelopment of the genital organs and secondary sexual characteristics becomes noticeable.

One of the main hypothalamic-endocrine symptoms is caused by insufficient production of antidiuretic hormone diabetes insipidus, characterized by increased thirst and the excretion of large quantities of urine with low relative density. Excessive secretion of adiurecrin is characterized by oliguria, accompanied by edema, and sometimes alternating polyuria in combination with diarrhea (Parhon's disease).

Excessive production of growth hormone by the anterior pituitary gland is accompanied by the development acromegaly syndrome.

Insufficiency of somatotropic hormone (GH) production, which manifests itself from childhood, leads to physical underdevelopment of the body, which manifests itself hypo-

Rice. 12.6.Cerebral obesity.

physical dwarfism, At the same time, the first thing that attracts attention is the proportional dwarf growth combined with underdevelopment of the genital organs.

Hyperfunction of oxyphilic cells of the anterior pituitary gland leads to excess production of growth hormone. If its excessive production manifests itself during puberty, it develops pituitary gigantism. If redundant function oxyphilic cells of the pituitary gland manifests itself in adults, this leads to the development acromegaly syndrome. In the pituitary giant, attention is drawn to the disproportionality of the growth of individual parts of the body: the limbs are very long, and the torso and head seem relatively small. With acromegaly, the size of the protruding parts of the head increases: the nose, the upper edge of the eye sockets, the zygomatic arches, lower jaw, ears. The distal parts of the limbs also become excessively large: hands, feet. There is a general thickening of the bones. The skin becomes coarser, becomes porous, folded, greasy, and hyperhidrosis appears.

Hyperfunction of basophilic cells of the anterior pituitary gland leads to the development Itsenko-Cushing's disease, caused mainly by excess production of adrenocorticotropic hormone (ACTH) and the associated increase in the release of adrenal hormones (steroids). Disease characterized first of all a kind of obesity. The round, purple, greasy face attracts attention. Acne-type rashes are also typical on the face, and in women there is also growth of facial hair. male type. Hypertrophy of fatty tissue is especially pronounced on the face, on the neck in area VII cervical vertebra, in the upper abdomen. The patient's limbs appear thin in comparison with the obese face and torso. On the skin of the abdomen and the anterior inner surface of the thighs, stretch marks are usually visible, reminiscent of stretch marks of pregnant women. Besides, characterized by an increase blood pressure, amenorrhea or impotence are possible.

With severe insufficiency of the functions of the hypothalamic-pituitary region, pituitary wasting, or Simons disease. The disease progresses gradually, and exhaustion reaches a sharp degree of severity. Skin that has lost turgor becomes dry, matte, wrinkled, the face acquires a Mongoloid character, hair turns gray and falls out, and nails become brittle. Amenorrhea or impotence occurs early. A narrowing of the circle of interests, apathy, depression, and drowsiness are noted.

Sleep-wake syndromes may be paroxysmal or protracted, sometimes persistent (see Chapter 17). Among them, perhaps the best studied narcolepsy syndrome, manifested by an uncontrollable desire to sleep, arising in daytime, even in the most inappropriate circumstances. Often associated with narcolepsy cataplexy characterized by seizures sharp decline muscle tone, leading the patient to a state of immobility for a period of several seconds to 15 minutes. Attacks of cataplexy often occur in patients who are in a state of passion (laughter, feelings of anger, etc.), states of cataplexy that occur upon awakening are also possible (awakening cataplexy).

Modern methods physiological research, in particular the experience of stereotactic operations, allowed us to establish that hypothalamic region, along with other structures of the limbic-reticular complex, takes part in the formation of emotions, the creation of the so-called emotional background (mood) and the provision of external emotional manifestations. According to P.K. Anokhina (1966), the hypothalamic region determines

the primary biological quality of an emotional state, its characteristic external expression.

Emotional reactions first of all sthenic emotions, lead to an increase in the functions of the ergotropic structures of the hypothalamus, which, through the autonomic nervous system (mainly its sympathetic department) and the endocrine-humoral system stimulate the functions of the cerebral cortex, which, in turn, affects many organs and tissues and activates metabolic processes in them. As a result arises voltage or stress, manifested by the mobilization of the body's means of adaptation to a new environment, helping him to protect himself from harmful endogenous and exogenous factors affecting him or only expected ones.

The causes of stress (stressors) can be a wide variety of chronic and acute mental effects that provoke emotional stress, infections, intoxication, and trauma. During periods of stress, the function of many systems and organs usually changes, primarily cardiovascular and respiratory systems(increased heart rate, increased blood pressure, redistribution of blood, increased breathing, etc.).

According to G. Selye (Selye H., born in 1907), stress syndrome, or general adaptation syndrome, goes through its development 3 phases: alarm reaction, during which they mobilize protective forces body; stage resistance, reflecting complete adaptation to stress; stage exhaustion, which occurs inevitably if the stressor turns out to be excessively intense or acts on the body for too long, since the energy of adaptation or adaptability of a living organism to stress is not unlimited. The exhaustion stage of stress syndrome is manifested by the emergence of a painful condition that is nonspecific in nature. Various options G. Selye called such painful conditions diseases of adaptation. They are characterized by shifts in hormonal and autonomic balance, dysmetabolic disorders, metabolic disorders, and changes in the reactivity of nervous tissue. “In this sense,” wrote Selye, “certain nervous and emotional disorders, arterial hypertension, some types of rheumatism, allergic, cardiovascular and kidney diseases are also diseases of adaptation.”

The diencephalon, the largest part of the brain stem, has the most complex structure and develops from the second cerebral vesicle (the posterior part of the anterior cerebral vesicle). From the lower wall of this bladder, a phylogenetically older region is formed - the hypothalamus, hypothalamus. The lateral walls of the second brain bladder significantly increase in volume and turn into the thalamus, thalamus, and metathalamus, metathalamus, which are phylogenetically younger formations. The upper wall of the brain bladder grows less intensively and forms the epithalamus, epithalamus, and the roof of the third ventricle, which is the cavity of the diencephalon.

In the whole brain preparation, the diencephalon is not accessible for viewing, because entirely hidden by the cerebral hemispheres. Only at the base of the brain can one see the central part of the diencephalon - the hypothalamus.

The diencephalon consists of gray and white matter. The gray matter of the diencephalon consists of nuclei belonging to the subcortical centers of all types of sensitivity. The diencephalon contains the reticular formation, centers of the extrapyramidal system, vegetative centers (regulate metabolism), and neurosecretory nuclei.

The white matter of the diencephalon is represented by conducting pathways of descending and ascending directions, providing bilateral communication of the subcortical formations with the cerebral cortex and the nuclei of the spinal cord.

In addition, the diencephalon includes two endocrine glands - the pituitary gland and the pineal gland.

Boundaries of the diencephalon. At the base of the brain, the posterior border is anterior edge of the posterior perforated substance and posterior surfaces of the optic tracts, front – anterior surface of the optic chiasm and anterior edges of the optic tracts.

On the dorsal surface, the posterior border of the diencephalon corresponds to the anterior border of the midbrain and runs along groove separating the superior colliculi of the quadrigeminal from the posterior edges of the thalamus and pineal gland. The anterolateral border is formed by the stria terminalis, which separates the thalamus from the caudate nucleus.

The diencephalon includes the following sections: the thalamic region (visual brain), the hypothalamus and the third ventricle.

Thalamic region

The thalamic region includes the thalamus, metathalamus and epithalamus.

The thalamus, the optic thalamus, is a paired formation that has an irregular ovoid shape and is located on both sides of the third ventricle. In the anterior section, the thalamus narrows and ends with the anterior tubercle, tuberculum anterius thalami, the posterior end is thickened and called the cushion, pulvinar. Only two surfaces of the thalamus are free: the medial one, facing the third ventricle and forming its lateral wall (from below it is limited by the hypothalamic groove), and the upper one, which takes part in the formation of the bottom of the central part of the lateral ventricle. The medial surfaces of the right and left thalami are connected to each other by interthalamic fusion, adhesio interthalamica.

The superior surface of the thalamus is separated from the medial surface by the stria medullaris thalami, and from the lateral caudate nucleus by the stria terminalis.

The lateral surface of the thalamus is adjacent to the internal capsule, which separates it from the striatum. Inferiorly and posteriorly it borders with the tegmentum of the midbrain.

Internal structure. The thalamus consists of gray matter, in which individual clusters of nerve cells are distinguished - the nuclei of the thalamus, nuclei thalami. These clusters are separated from each other by thin layers of white matter. About 40 nuclei of the thalamus are known, which perform various functions. The main nuclei of the thalamus are: anterior, nuclei anteriores, posterior, nuclei posteriores, medial, nuclei mediales, median, nuclei mediani, inferolateral, nuclei inferolateralis, and a number of others.

The processes of the second neurons of all sensitive pathways (with the exception of olfactory, gustatory and auditory) come into contact with the nerve cells of the thalamic nuclei. In this regard, the thalamus can rightfully be considered a subcortical sensitive center.

Some of the processes of thalamic neurons are directed to the nuclei of the striatum (and therefore the thalamus is considered as a sensitive center of the extrapyramidal system). Another part of the processes of thalamic neurons goes to the cerebral cortex, forming the thalamocortical bundle, fasciculus thalamocorticalis.

Below the thalamus is the so-called subthalamic region, regio subthalamica. It contains the subthalamic nucleus, nucleus subthalamicus (Lewis body). It is one of the centers of the extrapyramidal system.

The red nucleus and substantia nigra of the midbrain continue into the subthalamic region from the midbrain and end there.

The metathalamus (zathalamic region), metathalamus, is represented by paired formations - the lateral and medial geniculate bodies. These are oblong-oval bodies connected to the colliculi of the midbrain roof with the help of the handles of the superior and inferior colliculi.

The lateral geniculate body, corpus geniculatum laterale, is located near the inferolateral surface of the thalamus, on the side of the pillow. It can be easily detected by following the optic tract, the fibers of which follow the lateral geniculate body. This connection is explained by the fact that the lateral geniculate body, together with the superior colliculi of the midbrain quadrigeminal, are subcortical centers of vision.

Somewhat inward and posterior to the lateral geniculate body, under the pillow, is the medial geniculate body, corpus geniculatum mediale, in which the fibers of the lateral (auditory) loop end. Thus, the medial geniculate body and the inferior colliculus of the midbrain quadrigeminal form the subcortical hearing centers.

The epithalamus (suprathalamic region), epithalamus, includes the following formations: the pineal body, corpus pineale, which, with the help of leashes, habenulae, connects to the medial surfaces of the right and left thalamus. At the junction of the leashes into the thalami there are triangular extensions - triangles of the leash, trigonum habenulae. The anterior sections of the leashes are connected to each other using the adhesion of the leashes, commissura habenularum. Each leash contains the medial and lateral nuclei of the leash, nuclei habenulae medialis et lateralis. In the cells of the leash nuclei, most of the fibers of the medullary stria of the thalamus end. In front and below the pineal body there is a bundle of transversely running fibers - the epithalamic commissure, commissura epithalamica, connecting the divergent legs of the fornix. Between the epithalamic commissure below and the commissure of the leashes above, a shallow blind pocket protrudes into the anterosuperior part of the pineal body - the pineal recess, recessus pinealis.

Shape, topography, external structure: The boundaries on the ventral side are the optic chiasm and the posterior perforated substance; on the dorsal side, the lamina terminalis and the groove between the superior colliculi of the midbrain roof and the thalamus. Represented by two visual tubercles - thalamus and adjacent to them epithalamus(brain stripes, leash triangles, leashes, pineal gland), metathalamus(pillows, medial and lateral geniculate bodies, located under the pillows and connected to the roof of the midbrain by the handles of the superior and inferior colliculi), hypothalamus And subthalamus. On the ventral surface of the brain, hypothalamic structures are visible - the infundibulum, adjacent to the optic chiasm posteriorly and passing into the pituitary stalk, gray tubercle, mammillary bodies.

Cavity of the diencephalon - third ventricle, vertical fissure, in the depth of which the interthalamic fusion is located. The lateral walls are the medial surfaces of the thalamus, the anterior wall is the columns of the fornix, the posterior wall is the posterior commissure above the entrance to the aqueduct of Sylvius, the upper wall is the epithelial plate, above which is the choroid plexus, above is the fornix, and above it is the corpus callosum.

Internal structure: the bulk are the nuclei of gray matter. IN thalamus and metathalamus In accordance with their functions, specific (sensory and non-sensory switching and associative) and non-specific nuclei are distinguished. Specific switch cores receive afferents from various sensory systems or other parts of the brain and send axons to certain projection zones of the cortex (lateral geniculate bodies, pillow - visual nuclei, medial geniculate bodies - auditory nuclei, posterior ventral nucleus - general sensitivity, ventrolateral nuclei - motor centers, in which pathways from the cerebellar nuclei and basal ganglia switch). Associative kernels receive afferents from other thalamic nuclei and send axons to the associative zones of the cortex (intersensory integration). Nonspecific nuclei receive afferentation through collaterals from various sensory pathways and from the reticular formation, and their efferents go diffusely to many areas of the cortex (regulation of activity level).

IN hypothalamus allocate 32 pairs of cores that perform many tasks different functions. Many nuclei contain neurosecretory cells that transform nerve impulse into neurohormonal influences realized through the pituitary gland (a single hypothalamic-pituitary system). The nuclei of the anterior group (supraoptic and paraventricular) produce the neuropeptides vasopressin (antidiuretic hormone) and oxytocin, which enter the posterior lobe of the pituitary gland, and from there into the blood. Vasopressin regulates vascular tone and the process of reabsorption of water in the renal tubules, oxytocin affects the function reproductive system, sexual behavior and causes contraction of the muscles of the pregnant uterus. Other nuclei of the anterior hypothalamus increase parasympathetic activity. The nuclei of the medial group produce releasing factors (liberins and statins), which enter the anterior lobe of the pituitary gland and affect the secretion of pituitary hormones. Neurons that perceive information about the physical and chemical properties of the body’s internal environment are also located here. Some medial nuclei (grey tuberous) affect the emotional state and level of wakefulness. The nuclei of the posterior group are subcortical centers of smell (nuclei of the mammillary bodies), associated with thermoregulation and defensive behavior, activate sympathetic division autonomic nervous system.

Epiphysis, or pineal gland - neuroendocrine gland weighing 0.2 grams. Synthesizes melatonin and serotonin, the secretion of which depends on the level of illumination and obeys circadian rhythms. Is a component of " biological clock", participates in anti-stress protection of the brain, influences the process of puberty.

Pituitary gland – The central endocrine gland weighs 0.6 g, lies in the sella turcica of the base of the skull, is connected to the hypothalamus and is subject to its regulatory influences ( hypothalamic-pituitary system).

The human structure is a very complex thing, especially when it comes to the brain. This is a tireless part of our body, which hides all the secrets of human essence. Next, let's talk about the functions of the diencephalon and its role in the entire human body.

The main task of the diencephalon is to regulate the motor reflexes of the body, coordinate the work of internal organs, as well as carry out metabolism, maintain body temperature, etc.

It goes without saying that the diencephalon itself can carry out and regulate few processes. But together with the head, it creates a complete system of regulation, coordination and integration of internal processes in the body.

Structure

Before the conversation turns to functions, we need to remember the structure of the diencephalon, which each of us learned in school, but today we hardly remember. So, the habitat of this brain is between the cerebral hemispheres and. Thus, it is located at the top of the trunk and consists of three parts:

• thalamus;
• hypothalamus;
• epithalamus.

Each of these terms has a simpler interpretation that is understandable to almost every person: the visual tuberosities, the subtuberculous part and the supra-tubercular part, respectively. It’s okay if you are confused and don’t quite understand what we’re talking about. Now we'll sort it all out.

Structure and functions of the thalamus

The thalamus is egg-shaped, and its narrow part faces backward. It also has several parts, but we'll talk more about the functions than the structure. So, it is in the thalamus that the processes of integration and processing of vital important signals that enter the human brain.

Presentation on the topic: "Structure and functions of the diencephalon"

And this happens thanks to the nuclei, which are the structural unit of the thalamus, their number reaches 120 pieces. Actually, these kernels are responsible for different functions. They receive signals and send projections to different structures. Thus, the thalamus receives signals from the visual and auditory system, as well as cutaneous taste and muscle.

If we talk about neurons that enter and exit the thalamus, then functionally they can be divided into several categories:

• Specific - this is where the paths that are directed to the cortex from the muscular, auditory, skin, eye, and other types of sensitive areas intersect. From them, information is transmitted exclusively to certain areas, namely 3-4 layers of the cortex. When dysfunction occurs in these nuclei, a person loses certain types of sensitivity.
• Non-specific nuclei represent very diverse complexes, most of which are responsible for the sleepy state. Thus, if the function of these complexes is impaired, the person will have a constantly sleepy state.
• Associative. The main components of the associative nuclei are neurons; they perform multisensory functions, it is thanks to them that modalities are excited, and also create an integrated signal that transmits information to the cerebral cortex.

Thus, the thalamus is responsible for regulating processes in different human organs, this is how the redistribution of visual information, auditory and tactile information occurs, as well as the distribution and collection of information about the sense of equilibrium and balance.

In addition, regarding the function of sleep regulation, if it is disturbed, a person can develop a disease such as fatal familial insomnia, in which the patient dies from insomnia, but fortunately, only 40 families are known who had such symptoms.

Main functions of the hypothalamus

The structure of the hypothalamus is very complex, so we will consider the structure and its functions in parallel. The hypothalamus organizes the homeostatic, emotional and behavioral reactions of the human body. It can also affect autonomic functions human (humoral and nervous), which influences sympathetic regulation. In addition, the structural elements of the hypothalamus have an impact on the preservation and regeneration of reserves in the human body. So, the nuclei of this part of the diencephalon are divided into several categories:

• nuclei of the anterior category;
• posterior category nuclei;
• middle category cores.

Now greatest attention will be given to the nuclei of the posterior category, because thanks to them sympathetic reactions occur in the body: an increase blood pressure, dilated pupils, increased heart rate.

So, if the posterior nuclei increase sympathetic reactions, then the nuclei of the middle group, on the contrary, reduce them. The processes of the following centers occur in the hypothalamus:

• thermoregulation;
• feelings of hunger;
• rage;
• fear;
• sexual desire, etc.

The listed processes depend on the activation or inhibition of various parts of the nuclei.

For example, when the nuclei of the anterior group are irritated, the human body instantly loses heat, and the blood vessels dilate; in addition, they are responsible for erotic pleasure and euphoria. And damage to the posterior hypothalamus can cause lethargic sleep.

The hypothalamus also regulates the coordination of human movements; for example, when this area is irritated, chaotic movements can occur, which are characteristic of movements during pain. Very important function The gray tubercle also functions as a component of the hypothalamus. When it is damaged, “out of order,” problems with metabolism begin, so, for example, a person may experience a strong craving for food, thirst, excessive secretion urine, convulsions, changes in blood composition, etc.

Thus, we can say that the functions of the diencephalon are as follows:

• in the implementation of vegetative functions;
• in the transmission of sensory processes in brain analyzers;
• in the regulation of sleep, behavior and memory;
• in the perception of pain.

And, of course, the pituitary gland

The pituitary gland is in very close contact with the functions of the hypothalamus. It accumulates hormones:

• which regulate water-salt balance;
• which are produced by the hypothalamus;
• who are responsible for normal functioning uterus and mammary glands in females.