The olfactory brain (rhinencephalon) is located on the lower and medial surfaces of the cerebral hemispheres and is conditionally divided into peripheral and central sections.

The peripheral part of the olfactory brain includes the olfactory bulb (bulbus olfactorius) and the tract (tractus olfactorius), located on the lower surface of the frontal lobe in the olfactory groove (sulcus olfactorius). The olfactory tract ends with an olfactory triangle (trigonum olfactorium), which diverges in front of the anterior perforated substance (substantia perforata anterior) with two olfactory strips (striae olfactoriae laterales) (see). The lateral strip goes around the bottom of the lateral groove (sulcus lateralis) and ends in the cortex of the hook of the temporal lobe (uncus). The medial strip goes to the medial longitudinal fissure in the subcallosal gyrus (gyrus subcallosus) and the olfactory field (area paraolfactoria), which are located under the beak of the corpus callosum (rostrum corporis callosi) (Fig. 474).

474. Scheme of the structure of the olfactory brain.

1 - bulbus olfactorius;
2 - stria olfactoria medialis;
3 - stria olfactoria lateralis;
4 - uncus hippocampi;
5 - corpus mamillare;
6 - fissura hippocampi;
7 - lamina terminalis;
8 - area olfactoria;
9 - trigonum olfactorium;
10-tr. olfactorius.

The central part of the olfactory brain includes: the vaulted gyrus, the hippocampus, the dentate gyrus, the hook, the intramarginal gyrus, the fascicular gyrus and the gray layer over the corpus callosum.

The vaulted gyrus (gyrus fornicatus) (see) has an annular shape, goes around the corpus callosum and is located on the medial surface of the hemispheres. The vaulted gyrus consists of three parts: the cingulate gyrus (gyrus cinguli) and the parahippocampal gyrus (gyrus parahippocampalis), connected by an isthmus (isthmus gyri cinguli).

The cingulate gyrus lies above the corpus callosum on the medial surface of the cerebral hemisphere and is not only the center of smell, but also the regulation of the function of internal organs (primarily the cardiovascular system). From above, it is limited by the cingulate groove (sulcus cinguli), from below by the groove of the corpus callosum (sulcus corporis callosi). In front, the cingulate gyrus connects with the near-terminal gyrus (sulcus paraterminalis), and behind, at the level of the parietal-occipital sulcus (sulcus parietooccipitalis), it passes into the isthmus of the fornix (isthmus fornicatus), which, below the posterior edge of the corpus callosum, connects with the gyrus of the hippocampus (gyrus parahippocam palis).

475. The structure of the central part of the olfactory brain.
1 - uncus;
2 - fimbria hyppocampi;
3 - gyrus dentatus,
4 - gyrus parahippocampalis.

The hippocampus (hippocampus) is an invagination of gray matter due to the sulcus hyppocampi from the side of the medial wall of the lower horn of the lateral ventricle (Fig. 475). The hippocampus is clearly visible in the cavity of the lower horn in the form of a club-shaped body. It is limited on the lateral side and in the back by a circumferential groove (sulcus collateralis), in front - by a nasal groove (sulcus rhinalis). The hippocampus at the anterior perforated substance is bent in the form of a hook (uncus), being the center of smell.

The dentate gyrus (gyrus dentatus) is a twisted part of the cortex of the medial edge of the sulcus hippocampi. The gray matter of the dentate gyrus also extends to the inner edge of the hippocampus, as well as to the dorsal surface of the corpus callosum, forming the so-called gray vestment (indusium griseum), which ends in the supracosal gyrus.

The hook (uncus) represents the anterior end of the hippocampal sulcus (fissura hippocampi), which is divided by a cord into two parts: anterior and posterior. The anterior part refers to the hook, and the posterior part forms the intramarginal gyrus (gyrus intralimbicus), which runs between the dentate gyrus and the white fringe, ending in the ligamentous gyrus (gyrus fasciolaris).

With an external examination of the human brain, three large parts are easily distinguished:

These anatomical names of such prominent departments have developed historically and do not reflect either the evolutionary history of the formation of the primate brain, or the real division into morphologically substantiated departments. The three obvious sections of the brain are only a tribute to the Renaissance, when faith in the progress and future of mankind was boundless. In neurobiological reality, the morphological structure of the brain looks much more prosaic.

With an average brain mass of 1310 g, the mass of the brain stem is usually 140-150 g, and the cerebellum is 120-160 g. Therefore, the mass of the hemispheres usually ranges from 78 to 90% of the total mass of the brain. The mass of the spinal cord rarely exceeds 34 g.

There are some other differences that characterize the features of the morphological structure of the brain regions. The surface of the large brain is covered with folds, which increases its area. Approximately 1/3 of the total area extends onto the outer surface, which in Europeans is about 4500 sq. cm (for both hemispheres of the forebrain). The human cerebellum has a huge number of grooves and convolutions. If you speculatively expand all the gyri of the cerebellum, then its length will be more than 2 m with a width of 15-20 cm. In other words, the surface area

Biology and genetics

By modern ideas in the process of evolution of vertebrates, the sense of smell, based on the olfactory brain, acted as the organizer of integral functions associated with the formation of all unconditionally reflex reactions of instincts: indicative defensive food sexual, etc. Thanks to the olfactory brain, a new morphofunctional association, the limbic system or visceral brain, was formed that provides a person with the following properties: emotional and motivational behavior ; complex behavior associated with a phase change ...

Olfactory brain

Olfactory brain, its central and peripheral parts.

According to modern concepts, in the process of evolution of vertebrates, the sense of smell, based on the olfactory brain, acted as the organizer of integral functions associated with the formation of all unconditionally reflex reactions (instincts): orientational, defensive, nutritional, sexual, etc.

Thanks to the olfactory brain, a new morpho-functional association has formed - the limbic system or the visceral brain, which provides a person with the following properties:

1. emotional and motivational behavior;
2. complex behavior associated with a change in the phases of wakefulness and sleep, operational and long-term memory, intuition, reproduction of offspring;
3. regulating influence on the cortical and subcortical structures of the brain for the necessary matching of their activity levels.

The central part of the olfactory brain and limbic system includes:

1. cingulate and parahippocampal gyrus, hook, dentate gyrus;
2. opercular parts of the frontal, parietal lobes, temporal pole, orbital gyrus, insula;
3. basal nuclei, hippocampus, hypothalamus, septum pellucidum, reticular formation.

The peripheral department includes:

1. olfactory bulbs, tracts, triangles;
2. anterior medulla, perforated substance;
3. olfactory stripes: lateral, medial, diagonal, intermediate.

The olfactory analyzer is represented by:

1. receptor department in the composition of the neuro-olfactory, supporting, basal cells and olfactory glands, which are located in the olfactory field of the nasal mucosa, which is in the region of the upper nasal passage and the upper part of the nasal septum;
2. conduction department: olfactory nerve of 15-20 olfactory filaments that pass through the ethmoid bone into the anterior cranial fossa and further to the peripheral part of the olfactory brain.
3. Olfactory bulbs with mitral cells, olfactory tracts and triangles, together with the anterior perforated substance and partly with the hippocampus, constitute the subcortical structures of the olfactory analyzer.
4. The cortical end (nucleus) is located on the lower temporal surface in the region of the hook of the parahippocampal gyrus (fields A and E) and partly in the hippocampus (field 11).

The mechanism of olfactory perception is implemented due to the spatial correspondence of odorous molecules to the shape of receptor sites on the surface of the olfactory villi of neurosensory cells, i.e. due to the stereochemical effect in the implementation of mint, flower, musky, ethereal, camphor odors. Through the charge density of odorous molecules, pungent and putrefactive odors are realized.

The olfactory brain, limbic system, "visceral brain" have different types of cortex and subcortical formations.

1. The ancient cortex (paleocortex) is found in the olfactory bulbs, the septum pellucidum, and the periamygdolar zone of the temporal pole.
2. The old cortex (archicortex) is concentrated in foci in the cingulate and dentate gyrus, the hippocampus.
3. Ancient and old bark (2.8%) is considered to be modern man heterogeneous due to the primitive structure.
4. The interstitial cortex (mesocortex) is located in the parahippocampal gyrus and insula.
5. The new cortex is located in large gyri - vaulted, opercular, etc.

In the subcortical structures of the limbic system, there are nuclei from ancient to new nuclear-cell formations. The pale balls belong to the paleostriatum, the amygdala complex to the archistriatum, and the putamen and caudate nucleus to the neostriatum.

The processes of the neurons of the limbic system form ascending and descending paths in the form of many closed circles of different diameters and lengths - large and small. For example, the large limbic circle of Paipez includes the hippocampus - the mastoid bodies of the hypothalamus - the anterior thalamic nuclei - the vaulted gyrus - the hippocampus. Through big circle learning processes are realized: attention, perception, reproduction, emotional coloring of information, memory. In a small circle: amygdala - hypothalamus - reticular formation of the midbrain - amygdala formed aggressive-defensive, eating, sexual behavior.

Another classification of limbic structures can be proposed:

1. anatomical layout with the allocation of two parts: basal and vaulted (around the corpus callosum);
2. anatomical and functional - with the anterior section along the lower and medial surface of the frontal lobe, which regulates behavior associated with nutrition, emotions, sex and the posterior section (posterior parts of the vaulted gyrus and hippocampus), where complex behavior, memory, intuition are realized.
3. In the cortex of the orbital convolutions, the islet, the temporal pole, the preservation of the life of the individual is ensured (the instinct of self-preservation); in the cingulate gyrus, hippocampus - preservation of the species and generative function.

All structures of the visceral brain receive terminals of neurons that release biogenic amines: dopamine, serotonin, norepinephrine, kinins, etc. They are delivered by axons formed into bundles: dopaminergic, serotoninergic, norepinephrine.

Thus, the visceral brain, integrating vegetative functions into consciousness, forms a holistic human response to external and internal stimuli, which is expressed in different types situational behaviour.

12

Olfactory brain, rhinencephalon, is the phylogenetically oldest part forebrain, which arose in connection with the analyzer of smell, when the forebrain had not yet become an organ of animal behavior. Therefore, all its components are different parts of the olfactory analyzer (for the concept of the analyzer, see "Morphological foundations of the localization of functions").

In fish, almost the entire forebrain is the organ of smell. With the development of a new cortex, which is observed in mammals and humans, a new part forebrain (neencephalon) - raincoat, pallium. But the cloak also goes its long way of development and contains three parts of different phylogenetic age. Older parts:

1. paleopallium, which is part of the temporal lobe. At first, this section was located on the lateral surface of the hemisphere, but later, under the influence of a greatly increasing neopallium, it folded into a sausage-shaped formation - the hippocampus and shifted medially into the cavity of the lateral ventricle of the telencephalon in the form of a protrusion of its lower horn. The hippocampus is covered ancient bark, paleocortex.

2. Archipallium- a small area of ​​the cortex on the ventral surface of the frontal lobe, lying near bulbus olfactorius and covered with old bark, archicortex.

3. Neopallium, a new cloak, in whose cortex, neocortex, higher centers of smell appeared - the cortical ends of the analyzer. This - uncus, which is part of the vaulted gyrus.

As a result, the human olfactory brain contains a number of formations various origins, which can be topographically divided into two sections. The peripheral department is olfactory lobe, lobus olfactorius, which means a number of formations lying on the basis of the brain: 1) bulbus olfactorius; 2) tractus olfactorius; 3) trigonum olfactorium; 4) substantia perforata anterior.

The central section is the convolutions of the brain: 1) parahippocampal gyrus, gyrus parahippocampali s; 2) dentate gyrus, gyrus dentatus; 3) vaulted gyrus, gyrus fornicatus, with its anterior part located near the temporal pole - crochet, uncus.