The brain is the anterior section of the central nervous system located in the cavity of the skull . It consists of the hemispheres and the brainstem with the cerebellum.
The brain is divided into five sections: 1) the medulla oblongata (myelencephalon); 2) the posterior brain (metencephalon), consisting of the bridge (variolyeva) and the cerebellum; 3) the middle brain (mesencephalon), in which are located the legs of the brain and quadruple; 4) the intermediate brain (diencephalon), consisting of the visual hillock (thalamus), the over-the-mountains, the foreign and foreign quarters; 5) the terminal brain (telencephalon), or the large hemispheres.
Just like in the spinal cord (see), the brain distinguishes between gray and white matter. From gray matter - accumulations of nerve cells - the brain and nucleus of the cerebral hemispheres and cerebellum are formed in the brain. White matter - a bundle of long and short nerve fibers, connecting the various formations of the brain with the spinal cord. In the brain stem there are accumulations of nerve cells with short numerous fibers - reticular formation (formatio reticularis).The
The medulla oblongata is a direct extension of the spinal cord. In the nuclei of the medulla oblongata the important cranial nerves originate (lingual-pharyngeal, wandering, extra and sublingual). Through it pass the way, conducting impulses from the spinal cord to the brain (centripetal) and from the brain to the spinal cord (centrifugal). One of the important ways is the pyramidal path connecting the motor region of the cerebral cortex with the motor cells of the anterior horns of the spinal cord. On the border of the medulla oblongata and the spinal cord, a crossroads of pyramidal pathways occur, which causes functional disturbances in case of damage to one or another area of the brain. When the pyramidal fascicle is damaged above the cross, hemiplegia develops (see) on the opposite side of the body; if cranial nerves are simultaneously affected, their function is disturbed on the side of the body, with the same lesion (see Alternating syndromes).
The bridge of the brain also contains the nuclei of cranial nerves - trigeminal, discharge, facial and stato-acoustic (pre-door-cochlear).
The junction of the bridge, medulla oblongata and cerebellum is called the bridge-cerebellar angle. It is located on the basis of the brain in the posterior cranial fossa. In this area, the facial and static-acoustic nerves emerge on the surface of the brain. In tumors in the region of the bridge-cerebellar angle, the nearest segments of the medulla oblongata, bridge and cerebellum are squeezed and the corresponding clinical symptoms develop.
The midbrain consists of a quadruple and the legs of the brain. The quadruple is located on the dorsal surface of the midbrain. Anterior tubercles of the quadruple are the primary visual centers, and the posterior ones are auditory. In the legs of the brain there is a red nucleus and a black substance that participate in the regulation of the plastic tonus of the muscles of the body, and at the bottom of the brain (sylvia) water pipe - the nucleus of the oculomotor and block craniocerebral nerves. Through the legs of the brain are the ascending paths that carry impulses to the visual mound and the large hemispheres, and descending paths that impulse impulses to the oblong and spinal cord. In the middle brain there is also a reticular substance (see above).
The main formations of the intermediate brain are visual knolls, which are the collector of all sensitive pathways (except olfactory ones) that pass to the large brain, the hypothalamus , the cranial bodies with subcortical visual and auditory centers, and the pineal body with adjacent formations.The
In each department of the brain there are cavities - the ventricles of the brain. Ascending, the central channel of the spinal cord, expanding, turns into the IV ventricle, the bottom of which is a rhomboid fossa formed by an oblong brain and a bridge. In the thickness of the bottom of the IV ventricle there are nuclei of cranial nerves (from V to XII pairs). Above the IV ventricle is the cerebellum (see). On the outside, the IV ventricle is bounded by the legs of the cerebellum, from above - by the vascular plate, the upper and lower cerebral sail. Above the IV the ventricle narrows and in the middle brain area passes into the cerebral (sylvia) aqueduct, surrounded by gray matter. The cerebral aqueduct at the top passes into the third ventricle - the cavity of the intermediate brain. The lateral walls of the third ventricle are visual bumps; the upper epithelial plate (roof of the third ventricle), above which lies the vault and corpus callosum of the cerebral hemispheres; front - front spike and column vault. Between the columns of the arch and the anterior part of the corpus callosum there is a transparent septum. The bottom of the third ventricle is a lowland: the terminal plate, the cross of the optic nerves, the funnel, the pituitary gland, the gray mound, the nipple bodies.
The cavity of the third ventricle is connected by means of interventricular orifices with lateral ventricles of the cerebral hemispheres. In the lateral ventricles distinguish the anterior, posterior and lower horn of the lateral ventricles. Just like in IV and III ventricles, they contain vascular plexuses.
The vascular plexuses produce a cerebrospinal fluid (see) that fills the ventricles of the brain and the cavity of the central spinal canal. Through the openings of the lower cerebral sail, cerebrospinal fluid comes from the cavity of the IV ventricle into the subarachnoid space (see Brain shells) and also bathes the outer surface of the brain and spinal cord. If the permeability of these holes is impaired, as well as when the cerebral conduit is compressed by a tumor, occlusive hydrocephalus may develop (see).
The final brain is divided by a longitudinal furrow into two hemispheres connected by a corpus callosum, a vault and an anterior commissure. The corpus callosum is a powerful bundle of fibers that connect the hemispheres of the brain. The vault is divided anteriorly into columns, and the back to the legs. Between the legs of the arch lies the spike of the arch. Columns of the vault are directed to the nipple bodies, from the inner core of which the bundle originating to the visual tubercle originates. The hemispheres of the brain are divided into the frontal, parietal, temporal, occipital lobe and islet. The surface of the cerebral hemisphere - the cloak (pallium) - is furrowed by furrows, between which lie convolutions. The deepest lateral (sylvian) furrow separates the temporal lobe from the frontal and parietal fissures. In the depth of the lateral furrow is an islet. Part of the frontal and parietal lobes over the lateral furrow is called the central cover. The frontal and parietal lobes are separated from each other by a central (Roland) furrow. Around the central furrow lie the precentral and postcentral gyrus. In the frontal lobe there are two or three frontal furrows, the lower surface of which is cut by the orbital and olfactory grooves. At the latter is the olfactory tract.
The dark share is divided into the lower and upper lobes, it is cut by the intertematic sulcus. On the inner surface of the occipital lobe there pass the spinal and parieto-occipital furrows. Between them is the so-called wedge. A furrow of the corpus callosum and a furrow furrow pass along the inner surface of the hemisphere; between them lies the girdle, which is part of the limbic region.
Under the gray matter of the hemispheres - the cortex of the brain - there are white matter and basal nuclei. A white substance consisting of fibers forms the outer and inner bags.
In the cortex of the terminal brain there is representation of various functions (cortical centers). According to the teachings of IP Pavlov , the crust is the cortical end of the analyzers. In the occipital region the visual analyzer is presented, in the temporal - auditory, in the postcentral - the general sensitivity, in the precentral - the motor analyzer.
The limbic region has to do with vegetative functions. Such areas as the frontal, inferior parietal, temporo-parieto-occipital subregion, refer to the interzonalizatornym zones, performing higher mental, speech functions, as well as subtle, purposeful movements of the hands.
Fig. 2. The brain. Side view: 1- frontal lobe; 2 - temporal lobe; 3 - medulla oblongata; 4 - cerebellum; 5- occipital lobe; b - parietal lobe; 7 - lateral groove; 8 - central furrow.
Fig. 3. The brain. Top view: 1 - frontal lobes of hemispheres; 2 - parietal hemispheres; 3 - occipital hemispheres; 4 - longitudinal slit of the brain.
Fig. 4. The trunk of the brain. View from above: 1-visual hillock; 2 - pineal body; 3 - quadruple; 4 - the nerve block; 5 - the trigeminal nerve ; 6 - upper cerebral sail; 7-upper cerebellar pedicle; 8 - middle leg of the cerebellum; 9 - facial nerve; 10 - a rhomboid fossa; 11 - pharyngeal nerve; 12 - the vagus nerve; 13 - additional nerve; 14 - medulla oblongata; 15 - the lower leg of the cerebellum; 16 - the leg of the brain.
Fig. 5. The basis of the brain: 1 - frontal lobes of the hemisphere; 2 - olfactory tract; 3 - optic nerve; 4 is the hemispheric part of the hemisphere; 5 - oculomotor nerve; 6 - the block nerve; 7-bridge; 8 - the trigeminal nerve; 9 - the abducent nerve; 10 - facial and pre-vertebral-cochlear nerves; 11 - pharyngeal nerve; 12 - the vagus nerve; 13 - additional nerve; 14 - cerebellum; 15 - occipital hemispheres; 16 - pyramids of the medulla oblongata; 17 - sublingual nerve ; 18 - mastoid body; 19 - a gray hillock and a funnel; 20 - cross of the optic nerves.