The role of red nuclei. The red nucleus of the midbrain is the center of the extrapyramidal system
107. Midbrain. midbrain nuclei
midbrain (mesencephalon) develops from the middle brain bladder and is part of the brain stem. On the ventral side, it adjoins the posterior surface of the mastoid bodies in front and the anterior edge of the bridge behind (Fig. 3.14, 3.15). On the dorsal surface, the anterior border of the midbrain is the level of the posterior commissure and the base of the pineal gland (pineal gland), and the posterior border is the anterior margin of the medullary velum. The structure of the midbrain includes the legs of the brain and the roof of the midbrain (Fig. 3.27; Atl.). The cavity of this part of the brain stem is plumbing of the brain a narrow canal that communicates with the fourth ventricle from below, and from above with the third (Fig. 3.27). In the midbrain there are subcortical visual and auditory centers and pathways that connect the cerebral cortex with other brain formations, as well as pathways that transit through the midbrain and their own pathways.
four hills, or midbrain roof (tectum mesencephali)(Fig. 3.27) is divided by grooves perpendicular to each other into upper and lower hillocks. They are covered by the ridge of the corpus callosum and the cerebral hemispheres. On the surface of the mounds is a layer of white matter. Under it, in the upper colliculus, layers of gray matter lie, and in the lower gray matter forms nuclei. On neurons, gray matter ends and some pathways begin from them. The right and left hillocks in each colliculus are connected by commissures. Laterally depart from each mound knoll handles, which reach the geniculate bodies of the diencephalon.
Superior colliculus contains centers of orienting reflexes to visual stimuli. The fibers of the optic tract reach the lateral geniculate bodies, and then some of them along handles of the superior colliculus continues into the superior tubercles of the quadrigemina, the rest of the fibers go to the thalamus.
inferior colliculus serves as the center of orienting reflexes to auditory stimuli. From the mounds go forward and outward handles, ending at the medial geniculate bodies. Hillocks take part of the fibers lateral loop, the rest of its fibers go as part of the handles of the lower colliculus to the medial geniculate body.
Originates from the roof of the midbrain tectospinal path. Its fibers after cross in the tegmentum of the midbrain they go to the motor nuclei of the brain and to the cells of the anterior horns of the spinal cord. The path conducts efferent impulses in response to visual and auditory stimuli.
On the border of the midbrain and diencephalon lie preopercular(pretectal) core, having connections with the superior colliculus and parasympathetic nuclei of the oculomotor nerve. The function of these nuclei is the synchronous reaction of both pupils when the retina of one eye is illuminated.
Brain peduncles (pedunculi cerebri) occupy the anterior part of the midbrain and are located above the bridge. Between them, the roots of the oculomotor nerve (III pair) appear on the surface. The legs consist of a base and a tire, which are separated by highly pigmented cells of the substantia nigra (see Atl.).
AT base of legs passes the pyramidal path, consisting of corticospinal, heading across the pons to the spinal cord, and cortical-nuclear, the fibers of which reach the neurons of the motor nuclei of the cranial nerves located in the region of the fourth ventricle and the aqueduct, as well as cortical-bridge path, ending on the cells of the base of the bridge. Since the base of the legs consists of descending pathways from the cerebral cortex, this part of the midbrain is the same phylogenetically new formation as the base of the pons or pyramid of the medulla oblongata.
black substance separates the base and cover of the legs of the brain. Its cells contain the pigment melanin. This pigment exists only in humans and appears at the age of 3-4 years. The substantia nigra receives impulses from the cerebral cortex, striatum, and cerebellum and transmits them to the neurons of the superior colliculus and brainstem nuclei, and then to the motor neurons of the spinal cord. The substantia nigra plays an essential role in the integration of all movements and in the regulation of the plastic tone of the muscular system. Violation of the structure and function of these cells causes parkinsonism.
Leg cover continues the tegmentum of the pons and medulla oblongata and consists of phylogenetically ancient structures. Its upper surface serves as the bottom of the aqueduct of the brain. The cores are located in the tire bloc(iv) and oculomotor(III) nerves. These nuclei develop in embryogenesis from the main plate, which lies under the borderline groove, consist of motor neurons and are homologous to the anterior horns of the spinal cord. Lateral to the aqueduct along the entire midbrain stretches nucleus of the mesencephalic tract trigeminal nerve. It receives proprioceptive sensitivity from the muscles of mastication and the muscles of the eyeball.
Beneath the gray matter surrounding the plumbing, from neurons intermediate nucleus the phylogenetically old way begins - medial longitudinal bundle. It contains fibers that connect the nuclei of the oculomotor, trochlear and abducens nerves. Fibers also join the bundle, starting from the nucleus of the nerve of the vestibule (VIII) and carrying impulses to the nuclei of the III, IV, VI and XI cranial nerves, as well as descending to the motor neurons of the spinal cord. The bundle passes into the bridge and the medulla oblongata, where it lies under the bottom of the fourth ventricle near the midline, and then into the anterior column of the spinal cord. Due to such connections, when the balance apparatus is stimulated, the eyes, head and limbs are set in motion.
In the region of the nuclei of the third pair of nerves lies the parasympathetic nucleus; it develops at the site of the border furrow and consists of intercalary neurons of the autonomic nervous system. In the upper part of the tegmentum of the midbrain, a dorsal longitudinal bundle passes, connecting the thalamus and hypothalamus with the nuclei of the brainstem.
At the level of the inferior colliculus, cross fibers of the superior cerebellar peduncle. Most of them end in massive cell clusters lying in front - red nuclei (nucleus ruber), and a smaller part passes through the red nucleus and continues to the thalamus, forming dentate-thalamic pathway.
In the red nucleus, fibers from the cerebral hemispheres also terminate. From its neurons there are ascending paths, in particular, to the thalamus. The main downward path of the red nuclei is rubro-spinal (red-nuclear-spinal). Its fibers, which immediately cross out of the nucleus, are directed along the tires of the brain stem and the lateral funiculus of the spinal cord to the motor neurons of the anterior horns of the spinal cord. In lower mammals, this path transmits to them, and then to the musculature of the body, impulses switched in the red nucleus, mainly from the cerebellum. In higher mammals, the red nuclei function under the control of the cerebral cortex. They are an important part of the extrapyramidal system that regulates muscle tone and has an inhibitory effect on the structures of the medulla oblongata.
The red nucleus consists of large and small cells. The large cell part is developed to a large extent in lower mammals, while the small cell part is developed in higher mammals and in humans. The progressive development of the small cell part proceeds in parallel with the development of the forebrain. This part of the nucleus is, as it were, an intermediate node between the cerebellum and the forebrain. The large cell part in humans is gradually reduced.
Lateral to the red nucleus in the tire is located medial loop. Between it and the gray matter surrounding the plumbing lie nerve cells and fibers. reticular formation(continuation of the reticular formation of the bridge and the medulla oblongata) and pass the ascending and descending paths.
The midbrain develops in the process of evolution under the influence of visual afferentation. In lower vertebrates, in which the cerebral cortex is almost absent, the midbrain is highly developed. It reaches a considerable size and, together with the basal ganglia, performs the functions of a higher integrative center. However, only the superior colliculus is developed in it. In mammals, in connection with the development of hearing, in addition to the upper ones, the lower tubercles also develop. In higher mammals, and especially in humans, in connection with the development of the cerebral cortex, the higher centers of visual and auditory functions pass into the cortex. In this case, the corresponding centers of the midbrain are in a subordinate position.
| " |
RED CORE RED CORE
(nucleus ruber), the structure of the midbrain of terrestrial vertebrates, located symmetrically in the thickness of the legs of the brain under the central gray matter. K. i. consists of a phylogenetically ancient (reptiles, birds) large-celled part (neuron body diameter 50-90 microns), from which the descending rubrospinal path begins, and a young (mammals) small-celled (20-40 microns in diameter), switching impulses from the nuclei cerebellum to thalamus. The number of small cell neurons increases in primates and humans. K. i. has projections to the motor nuclei of the spinal cord, which controls the movement of the fore and hind limbs, and is under the control of the cerebral cortex. K. Ya. is an important intermediate instance for the integration of the influences of the forebrain and cerebellum during the formation of dvpgat. commands to neurons in the spinal cord.
.(Source: "Biological Encyclopedic Dictionary." Chief editor M. S. Gilyarov; Editorial board: A. A. Babaev, G. G. Vinberg, G. A. Zavarzin and others - 2nd ed., corrected . - M .: Sov. Encyclopedia, 1986.)
See what the "RED CORE" is in other dictionaries:
The core is something central and most important, often round. This word has different meanings in different areas: Contents 1 Nuclear physics 2 Biology 3 Earth sciences 4 Sports ... Wikipedia
Contents 1 Nuclear physics 2 Biology 3 Earth sciences ... Wikipedia
In the trunks of tree species, the juices absorbed from the soil go only along the outermost layers of the wood. The more inner layers serve only as receptacles for water and reserve nutrients; finally, the innermost layers stop everything ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron
Marked as RC This article incorporates material from ... Wikipedia
I The cellular nucleus, an obligatory, along with the cytoplasm, an integral part of the cell in protozoa, multicellular animals and plants, containing chromosomes and products of their activity. According to the presence or absence in the cells of I., all organisms are divided into ... ... Great Soviet Encyclopedia
- (n. ruber, PNA, BNA, jna) large I. reddish yellow, located in the anterior part of the midbrain tegmentum; refers to the extrapyramidal system ... Big Medical Dictionary
Brain- (encephalon) (Fig. 258) is located in the cavity of the brain skull. The average weight of the adult brain is approximately 1350 g. It has an ovoid shape due to the protruding frontal and occipital poles. On the outer convex upper lateral ... ... Atlas of human anatomy
midbrain- On the lower surface of the brain, the structures of the midbrain (mesencephalon) are clearly visible: the legs of the brain and fibers of the oculomotor nerve (III pair). The former are directed from the anterior edge of the bridge, the latter come out of the interpeduncular fossa and ... ... Atlas of human anatomy
Cerebellum- (cerebellum) (Fig. 253, 254, 255, 257) lies under the occipital lobes of the cerebral hemispheres, separated from it by a horizontal fissure (fissura horizontalis) (Fig. 261) and located in the posterior cranial fossa (fossa cranii posterior). Anterior to…… Atlas of human anatomy
telencephalon- (telencephalon), which is also called the large brain, consists of two hemispheres and is the largest part of the brain. The hemispheres are connected to each other with the help of the corpus callosum (corpus callosum) (Fig. 253, 256). Every… … Atlas of human anatomy
Functions of the spinal cord. The spinal cord performs two functions - reflex and conduction. The reflexes of the spinal cord can be divided into motor(carried out by alpha motor neurons of the anterior horns), and vegetative(carried out by cells of the lateral horns). Motor elementary reflexes - flexion and extensor, tendon, myotatic, rhythmic, tonic. The centers of the autonomic nervous system are located in the spinal cord: vasomotor, sweating, respiratory, urinary, defecation, genital.
The conduction function of the spinal cord is associated with the transmission of information flow from the periphery to the overlying parts of the nervous system and with the conduction of impulses coming from the brain to the spinal cord.
Functions of the brain. There are five main divisions in the brain: medulla oblongata, hindbrain, midbrain, diencephalon, and forebrain.
Functions of the medulla oblongata. Performs two functions - reflex and conduction. Through the medulla oblongata, the following reflexes are carried out: 1) protective: coughing, sneezing, blinking, vomiting, tearing; 2) food: sucking, swallowing, secretion of digestive glands; 3) cardiovascular, regulating the activity of the heart and blood vessels; 4) in the medulla oblongata there is a respiratory center that provides ventilation of the lungs; 5) posture change is carried out due to static and statokinetic reflexes.
Conducting pathways pass through the medulla oblongata, connecting the cortex, intermediate, middle, cerebellum and spinal cord with a two-way connection.
Functions of the hindbrain. The hindbrain includes the bridge and the cerebellum. Functions bridge determined by the structures it contains. The ascending and descending pathways pass through the pons, connecting the medulla oblongata and cerebellum with the cerebral hemispheres. It conducts impulses from one hemisphere of the cerebellum to the other, coordinating muscle movements on both sides of the body; participates in the regulation of complex motor acts, muscle tone and body balance.
Cerebellum is a suprasegmental department of the central nervous system that does not have a direct connection with the executive bodies. He takes part in the regulation of postural-tonic reactions and the coordination of motor activity. After the removal of the cerebellum, the animal experiences disorders of motor acts: body position reflexes, static reflexes, and voluntary movements are disturbed. With unilateral removal of the cerebellum, there is a violation of movements on the side of the operation: muscle tone increases, the head and trunk turn in the same direction, and therefore the animal makes movements in a circle. The cerebellum is involved in the regulation of autonomic functions: respiration, digestion, cardiovascular activity, thermoregulation.
midbrain functions. The midbrain consists of the cerebral peduncles and the quadrigemina. The main centers of the midbrain: the red nucleus and the substantia nigra. red core midbrain performs motor functions - regulates the tone of skeletal muscles. If a transverse incision is made in a cat between the medulla oblongata and midbrain, then her muscle tone, especially the extensor muscles, sharply increases. An animal placed on legs stretched out like sticks can stand. This condition is called decerebrate rigidity.
black substance the midbrain activates the forebrain, giving emotional coloring to some behavioral responses. The function of the substantia nigra is associated with the implementation of chewing and swallowing reflexes.
Nuclei of the superior colliculus are the primary visual centers. They turn the eyes and head towards the stimulus (visual orientation reflex). Nuclei of the inferior colliculus are the primary auditory centers. They regulate the orienting reflexes that occur in response to sound stimuli.
Functions of the diencephalon. The diencephalon consists of the thalamus, hypothalamus, epithalamus, and metathalamus. thalamus is a collector of almost all types of sensitivity (except olfactory). According to their functional significance, the nuclei of the thalamus are divided into specific, nonspecific and associative.
Specific nuclei of the thalamus thalamus regulate tactile, temperature, pain and taste sensitivity, as well as auditory and visual sensations. Nonspecific nuclei of the thalamus have both an activating and inhibitory effect on small areas of the cortex. Associative nuclei of the thalamus transmit impulses from the switching nuclei to the associative zones of the cortex.
Hypothalamus is the highest subcortical center of the autonomic nervous system. Functionally, the nuclei of the hypothalamus are divided into anterior, middle and posterior groups of nuclei. Anterior nuclei hypothalamus are the centers of parasympathetic regulation, they also produce releasing factors that regulate the activity of the pituitary gland. Rear nuclei regulate sympathetic influences. Nucleus stimulation middle group leads to a decrease in the influence of the sympathetic nervous system.
Epithalamus (epiphysis) regulates the processes of sleep and wakefulness. Metathalamus (articulated bodies) involved in the regulation of vision and hearing.
limbic system. The limbic system includes the cingulate gyrus, the hippocampus, part of the nuclei of the thalamus and hypothalamus, the septum, etc. This system is involved in the regulation of autonomic functions, affects the change of sleep and wakefulness, provides memorization processes and plays an important role in the formation of emotions.
reticular formation. This is a special system of nerve cells with densely intertwined processes. It is located throughout the medulla oblongata, hindbrain, midbrain and diencephalon and has an activating and inhibitory effect on neurons in different parts of the central nervous system.
Basal ganglia (nucleus). The basal nuclei include the striatum, consisting of the caudate and lenticular nuclei and the orgada. These nuclei coordinate movements, participate in the formation of conditioned reflexes and the implementation of complex unconditioned reflexes (defensive, food-procuring, etc.).
Functions of the cerebral cortex. The cerebral hemispheres consist of white matter, covered on the outside with gray (bark), the thickness of which in various parts of the cerebral hemispheres is 1.3-5 mm. The number of neurons in the cortex reaches 10-14 mln. In the cerebral cortex, the bodies of neurons form six layers: 1st molecular; 2nd outer granular; 3rd external pyramidal; 4th internal granular; 5th internal pyramidal; 6th multimorphic. Areas of the cortex that are similar in structure, topography, according to the timing of differentiation in ontogenesis are called cytoarchitectonic fields. K. Brodman singled out 52 cytoarchitectonic (cellular) fields in the cortex.
Localization of functions in the cortex. In the cerebral cortex, the following zones are distinguished: sensitive (sensory), motor (motor) and associative
Sensory areas of the cortex. Afferent impulses from all receptors (with the exception of olfactory receptors) enter the cortex through the thalamus. The central projections of somatic and visceral sensitivity are separated into primary and secondary somatosensory zones. Primary somatosensory area located in the postcentral gyrus (fields 1,2,3). It receives impulses from the receptors of the skin and the motor apparatus . secondary somatosensory area located ventrally in the region of the lateral (Sylvian) furrow. Here there is a projection of the body surface, but less clear than in the primary somatosensory area.
visual cortex located in the occipital region of the cortex on both sides of the spur groove (fields 17,18,19). auditory cortex located in the temporal region (fields 41.42). Olfactory cortex located at the base of the brain, in the region of the parahippocampal gyrus (field 11). Projection of the taste analyzer localized in the lower part of the postcentral gyrus (field 43). Speech areas of the cortex. Fields 44 and 45 (Broca's center) and field 22 (Wernicke's center), located in the left cerebral hemisphere of right-handed people, are associated with the function of speech in the cerebral cortex.
Motor areas of the cortex localized in the precentral gyrus (fields 4, 6). Electrical stimulation of the upper part of the gyrus causes the movement of the muscles of the legs and torso, the middle part of the arms, and the lower part of the muscles of the face. Especially large is the zone that controls the movements of the hand, tongue, and mimic muscles.
association areas of the cortex occupy 1/3 of its entire area and communicate between different areas of the cortex, integrating all impulses entering the cortex into integral acts of learning (reading, speech, writing), logical thinking, memory and, finally, conscious reflection of reality.
Bioelectrical activity of the cortex. Fluctuations in the electric potentials of the crust were first recorded by V.V. Pravdich-Neminsky in 1913. The curve reflecting the electrical activity of cortical neurons is called an electroencephalogram (EEG). For EEG registration, multichannel electroencephalographs are used, and the international “10-20” scheme is used for electrode placement.
The following EEG rhythms are distinguished: alpha rhythm with a frequency of 8-13 Hz and an amplitude of 50 μV; beta rhythm with a frequency of 14-30 Hz and an amplitude of 25 μV; theta rhythm with a frequency of 4-8 Hz and an amplitude of 100-150 μV; delta rhythm with a frequency of 0.5-4 Hz and an amplitude of 250-300 μV.
In clinical practice, EEG allows you to assess the functional state of the brain.
⇐ Previous12345678910Next ⇒
The composition of the midbrain includes the quadrigemina and the legs of the brain (Fig. 28). The main centers of the midbrain: the red nucleus, the substantia nigra, the nuclei of the oculomotor and trochlear nerves.
The midbrain is a subcortical regulator of muscle tone, the center of visual and auditory orienting reflexes, as well as some complex motor reflex acts (swallowing and chewing).
The influence of the midbrain on the tone of the skeletal muscles is carried out through the red nucleus. Impulses converge to it from the cerebral cortex, subcortical nuclei and cerebellum, as well as from the reticular formation of the brain stem. Turning off the red nucleus leads to a sharp increase in the tone of the skeletal muscles (decerebrate rigidity).
The substantia nigra of the midbrain activates the forebrain, giving emotional coloring to some behavioral responses. Dopamine plays an important role in the transmission of these influences. The function of the substantia nigra is associated with the implementation of chewing and swallowing reflexes.
With the joint participation of the middle and medulla oblongata, congenital tonic reflexes are realized: postures (body positions), rectifying, lifting reflexes and reflex movements of the eyeballs during body rotation (nystagmus). The midbrain provides regulation of motor orienting reflexes. The anterior tubercles of the quadrigemina are the primary visual centers: they turn the eyes and head towards the stimulus (visual orienting reflex).
Fig.28. Anterior surface of the brain stem, inferior surface of the cerebellum:
1 - optic nerve; 2 - islet; 3 - pituitary gland; 4 - optic chiasm; 5 - funnel; 6 - gray tubercle; 7 - mastoid body; 8 - fossa between the legs of the brain; 9 - legs of the brain; 10 - semilunar node; 11 - small root of the trigeminal nerve; 12 - large root of the trigeminal nerve; 13 - abducens nerve; 14 - glossopharyngeal nerve; 15 - choroid plexus of the IV ventricle; 16 - vagus nerve; 17 - accessory nerve; 18 - the first cervical nerve; 19 - cross of pyramids; 20 - pyramid; 21 - hypoglossal nerve; 22 - auditory nerve; 23 - intermediate nerve; 24 - facial nerve; 25 - trigeminal nerve; 26 - varoli bridge; 27 - block nerve; 28 - outer cranked body; 29 - oculomotor nerve; 30 - visual path; 31-32 - anterior perforated substance; 33 - external olfactory strip; 34 - olfactory triangle; 35 - olfactory tract; 36 - olfactory bulb
The posterior tubercles of the quadrigemina are reflex centers of auditory orienting reflexes. When the auditory receptors are stimulated, alertness and a turn of the head towards the sound source occur.
Functions of the midbrain briefly
In the human brain, almost every part of it is irreplaceable. Together, these parts create a single incredibly well-oiled system. It is hardly worth expecting that in the near future any technique will be able to even replicate the functions of the brain. Unfortunately, today only a very small percentage of the human brain has been studied. However, quite a lot is known about the functions of the brain and parts of it such as the midbrain.
Briefly, the functions of the midbrain can be reduced to the following types: sensory, movement, conductive function, reflexes.
The midbrain is necessary for a person for the normal functioning of some reflexes, for example, rectifying and adjusting. Thanks to such reflexes, a person can stand and walk. In addition, the midbrain coordinates muscle tone and regulates it.
The structure and functions of the midbrain
Therefore, the normal functioning of the midbrain is a necessary condition for proper coordination of movements. The next important function of the midbrain is associated with vegetative processes. These processes include: chewing, swallowing, breathing, blood pressure.
Based on the foregoing, it can be seen that, in general, the midbrain is responsible for the body's response to various stimuli. Further, in addition to the reflexes already mentioned, the midbrain also provides for the restoration of balance, posture, when its normal position has been disturbed.
Thus, it can be seen that the midbrain is responsible for a number of functions and reflexes in the human body: movements as a reaction to stimuli, binocular vision, pupil response to light (accommodation), simultaneous rotation of the eyes and head, processing of primary information coming from the sense organs , muscle tone.
All this means that the importance of the midbrain is difficult to overestimate.
download dle 12.1
The gray matter of the telencephalon.
The gray matter of the telencephalon is represented by two formations: the basal (subcortical) nuclei, which are earlier structures, and the cerebral cortex, a later and perfect structure of the brain.
Basal nuclei lie in the form of separate formations in the thickness of the white matter, closer to the base of the brain (Fig. 27). In connection with their position, they got their name basal (subcortical, central) nuclei, nuclei basales. There are four nuclei in each hemisphere: the caudate, lenticular, fence and amygdala.
The caudate nucleus, nucleus caudatus, is localized most medially and anterior to the thalamus. It distinguishes an expanded anterior part - the head, caput nuclei caudati, which is located in the frontal lobe and below adjoins the anterior perforated substance, in contact with the lenticular nucleus. Posteriorly, the head narrows and passes into the body, corpus nuclei caudati, which is located in the parietal lobe and adjoins the thalamus, separated from it by a terminal strip. The body passes into the thinnest part - the tail, cauda nuclei caudati, which passes into the temporal lobe and reaches the amygdala nucleus.
The lentiform nucleus, nucleus lentiformis, is located lateral to the caudate nucleus and thalamus. It has the shape of a triangle with its base turned laterally. Thin layers of white matter, located sagittally, divide it into three parts. The lateral part is called the shell, putamen, dark in color. The other two parts of a lighter color are located medially and are called the medial and lateral cerebral plates, laminae medullares medialis et lateralis, which are combined under the common name pale ball, globus pallidus. The plates have another name - medial and lateral pale balls, globus pallidus medialis et lateralis.
The caudate and lenticular nuclei are united under the general name of the striatum, corpus striatum. The caudate nucleus and shell are newer formations - neostriatum (striatum), and the pale ball is an older formation - paleostriatum (pallidum). These names formed the basis of the term striopallidary system.
The fence, claustrum, is located laterally from the shell. This core has the appearance of a thin plate and is separated from the shell by a layer of white matter - the outer capsule, capsula externa.
The amygdala, corpus amygdaloideum, is located in the temporal lobe 1.5–2 cm posterior to its pole.
All basal nuclei belong to the subcortical motor centers. They have a wide connection with the thalamus and hypothalamus, with the substantia nigra and the red nucleus, and through them with the cortex of the telencephalon and motor neurons of the anterior columns of the spinal cord.
Their function is to maintain the tone of the skeletal muscles, the implementation of involuntary movements by these muscles and the automatism of a number of functions based on voluntary movements, but switched to an automatic mode of execution, for example, walking, speaking, stereotyped movements.
The cerebral cortex (cloak), cortex cerebri (pallium), It is represented by a layer of gray matter 1.5–5 mm thick, located outside over the entire surface of the cerebral hemispheres.
The cortex is made up of six layers of nerve cells. The distribution of these cells is referred to as "cytoarchitectonics". The largest cells (a layer of large pyramidal cells, or Betz cells) are concentrated in the fifth layer - the inner pyramidal plate. Between the cells are many nerve fibers. The peculiarity of their distribution in the cortex is defined by the term "myeloarchitectonics".
Based on the structural features of individual sections of the cortex, cytoarchitectonic maps were created, in which, according to various authors, from 52 to 150 fields or more are distinguished. Within these fields there are centers that regulate certain functions in the human body.
midbrain functions
Localization of the cortical nuclei of the analyzers on the upper lateral surface of the left hemisphere of the brain: 1 - the core of the skin analyzer; 2 - the core of stereognosy; 3 - the core of the motor analyzer; 4 - core of praxia; 5 - the core of the combined turn of the head and eyes; 6 - the core of the auditory analyzer; 7 - the core of the vestibular analyzer; A - the core of the motor analyzer of oral speech; B - the core of the auditory analyzer of oral speech; B - the core of the motor analyzer of written speech; G - the core of the visual analyzer of written speech
Rice. 29. Localization of the cortical nuclei of the analyzers on the medial and lower surfaces of the right hemisphere of the brain: 1 - the core of the analyzers of smell and taste; 2 - the core of the motor analyzer; 3 - the core of the vision analyzer
Localization of functions in the cerebral cortex. IP Pavlov considered the cortex of the telencephalon as a huge perceiving surface (450,000 mm 2), as a set of cortical ends of analyzers. The analyzer consists of three parts: 1) peripheral or receptor, 2) conductor and 3) central or cortical. The cortical part (the end of the analyzer) has a nucleus and a periphery. The nucleus contains identical neurons belonging to only one specific analyzer. Its location is clearly defined. It is where the highest analysis and synthesis of information coming from the receptors takes place.
The periphery of the cortical end of the analyzer has no clear boundaries, the cell density decreases compared to the nucleus. The peripheries of the analyzers overlap each other and are represented by neurons of the cortical representations of adjacent nuclei. In them, a simple, elementary analysis and synthesis of information takes place.
Ultimately, in the cortical end of the analyzer, based on the analysis and synthesis of incoming information, responses are developed that regulate all types of human activity. In the clinical aspect, the cortical ends of the analyzers (their nuclei) are considered in relation to the proportions of the hemispheres of the telencephalon, their convolutions and furrows. The cortical ends of almost all analyzers are located symmetrically in both hemispheres.
1. The cortical nucleus of general sensitivity, or skin analyzer (tactile, pain, temperature sensitivity), is located in the postcentral gyrus (Fig. 28). The skin surface of the human body in this gyrus is projected upside down and the area is directly proportional to the functional significance of one or another skin area of the body (Fig. 30, A). Therefore, most of the gyrus cortex is associated with receptors of the upper limb (especially the skin of the thumb) and the scalp (especially the skin of the lips).
The cortical nucleus of the sense of stereognosia (recognition of objects by touch) is located in the upper parietal lobe of the hemispheres.
3. The cortical nucleus of the motor analyzer, i.e., the nucleus of proprioceptive stimuli emanating from the structures of the musculoskeletal system, is localized in the precentral gyrus and the pericentral lobule. Receptor fields, like those of the skin analyzer, are projected upside down in direct proportion to the functional significance of a particular structure of the musculoskeletal system. In the upper section of the gyrus, the lower limb is projected, in the middle - the trunk and upper limb, in the lower - the neck and head. The figure of a person (Fig. 30, B) is projected into this gyrus with a huge face and mouth, a hand and especially a thumb, a small torso and a very small leg.
Rice. 30. Scheme of sensitive (A) and motor (B) homunculi: 1 - gyrus postcentralis; 2 - gyrus precentralis; 3 - ventriculus lateralis
4. The cortical nucleus of purposeful complex combined movements (the nucleus of praxia, from praxis - practice) is located in the lower parietal lobule within the gyrus supramarginalis. The function of this core is due to its large associative links. His defeat does not lead to paralysis, but excludes the possibility of performing practical (labor, professional) movements.
5. The cortical nucleus of the combined rotation of the head and eyes in the opposite direction is located in the posterior part of the middle frontal gyrus, which is part of the premotor zone.
The cortical nucleus of the olfactory analyzer is located in uncus et
7. Cortical nucleus of the taste analyzer hippocampus (Fig. 29)
8. The cortical nucleus of the visual analyzer is located on the medial surface of the occipital lobe of the cerebral hemispheres along the edges of the sulcus calcarinus, within the cuneus, gyrus occipitotemporalis medialis seu lingualis (Fig. 27). In each hemisphere, within the nucleus, the receptors of the lateral half of the retina of the eye of this side and the medial half of the retina of the opposite side are projected.
9. The cortical nucleus of the auditory analyzer is located in the middle section of the superior temporal gyrus (Geshl's gyrus), facing the insula. The nucleus receives nerve impulses from the receptors of the hearing organs of the left and right sides.
10. The cortical nucleus of the statokinetic (vestibular) analyzer is located in the middle parts of the inferior and middle temporal gyri.
11. Cortical nuclei of speech analyzers. In humans, these nuclei were formed in connection with the development of the second signaling system (oral and written speech) on the basis of associative connections with the cortical nuclei of vision and hearing (Fig. 28).
a) The core of the motor analyzer of oral speech (speech articulation), Broca's center (P. Broca), is located in the posterior part of the inferior frontal gyrus in the pars triangularis. The defeat of this nucleus leads to the loss of the ability to pronounce words, although the ability to pronounce sounds and sing remains. This phenomenon is called motor aphasia.
b) The core of the auditory analyzer of oral speech, the center of Wernicke (K. Wernicke), is located in the posterior part of the superior temporal gyrus, in the depth of the lateral sulcus, in close proximity to the nucleus of the auditory analyzer. Damage to the nucleus leads to the disappearance of the ability to understand sounding speech and control the pronunciation of words, verbal deafness, or sensory aphasia, occurs. However, the auditory perception of sounds remains.
c) The cortical nucleus of the motor analyzer of written speech is located in the posterior part of the middle frontal gyrus, which is adjacent to that part of the cortex of the precentral gyrus, from where the work of the muscles of the hand, in particular the hand, is regulated, which ensures the writing of letters and other signs.
The defeat of this core leads to agraphia - the inability to perform precise and subtle movements necessary to write letters, numbers and words.
d) The cortical nucleus of the visual analyzer of written speech is localized in the angular gyrus of the inferior parietal lobule, in gyrus angularis, in close proximity to the nucleus of the visual analyzer. If this nucleus is damaged, the ability to perceive the written text, i.e., to read, disappears in a person. This phenomenon is called alexia.
Previous123456789101112131415Next
VIEW MORE:
The human midbrain
midbrain is an ancient part of the brain, included in its trunk. It includes an ancient visual center. The midbrain is located below the cerebral cortex and above the hindbrain, being, as it were, in the very center of the brain. Caudally, the midbrain adjoins the hindbrain, and rostrally, to the diencephalon. In the ventral part of the midbrain are the so-called legs of the brain, most of which are occupied by the pyramidal pathways. In the midbrain, between the legs, there is an interpeduncular fossa, from which the third oculomotor nerve originates. Deep in the interpeduncular fossa is the posterior perforated substance.
The midbrain contains: midbrain roof(tectum) inferior colliculus(inferior colliculus), colliculus(superior colliculi), brain legs(cerebral peduncle) midbrain tegmentum(midbrain tegmentum), black matter(substantia nigra), brain stem(crus cerebri). It should be noted that there is no visible border with the diencephalon.
The midbrain is part of the brain stem. The substantia nigra of the midbrain is closely related to the musculoskeletal system of the basal ganglia pathways. Dopamine is produced in the substantia nigra and ventral tegmentum, which plays an important role in motivation and arousal. The midbrain transmits visual and auditory information.
quadrigemina
The quadrigemina of the midbrain consists of two pairs of lower and upper hillocks. The upper pairs are visual and the lower pairs are auditory. while the upper pairs of hillocks are somewhat larger than the lower pairs. These hillocks are connected with the structures of the diencephalon called geniculate bodies. In this case, the superior colliculi are associated with the lateral ones, and the inferior colliculi with the medial ones. The trochlear nerve emerges from the posterior surface of the midbrain. The four hard lobes help to cross several optic fibers at right angles. The auditory nuclei are located inside the inferior colliculus.
brain legs
The cerebral peduncles are paired structures located on the ventral side of the cerebral aqueduct. They transfer the tegmentum to the dorsal side. The middle part of the brain contains substantia nigra, which is a type of nucleus basalis. The substantia nigra is the only part of the brain that contains melanin. Between the legs is the interpeduncular fossa.
The structure of the midbrain, its functions and features
which is filled with cerebrospinal fluid, is like a flushing tank. The oculomotor nerve exits between the crura, and the trochlear nerve noticeably wraps around the outer sides of the crura.
The oculomotor nerve (parasympathetically) is responsible for pupillary constriction and for some eye movements.
The structure of the midbrain in sections
With a horizontal section of the midbrain at the level of the superior colliculus, there is a red nucleus, the nuclei of the oculomotor nerve and the nuclei of Edinger-Westphal associated with them, the cerebral peduncles, and also the substantia nigra.
With a horizontal section of the midbrain at the level of the lower colliculus, a black substance is also observed, the nuclei of the trochlear nerve and the crosshairs of the upper cerebellar peduncles are also clearly visible.
In both cases, there is a cerebral aqueduct connecting the third and fourth ventricles and the periaqueductal gray matter.
midbrain development
During embryonic development, the midbrain develops from the second vesicle. It remains indivisible during further development, unlike the other two vesicles of the forebrain and hindbrain. The division into other areas of the brain during the development of the nervous system does not occur, in contrast to the forebrain, which is divided into the telencephalon and diencephalon.
During the period of embryonic development in the midbrain, there is a continuous development of nerve cells, which are gradually compressed by the cerebral aqueduct. In some cases (with impaired development), partial or complete blockage of the cerebral aqueduct may occur, which leads to congenital hydrocephalus.
midbrain comprises:
Mound of the quadrigemina,
red core,
black substance,
Seam core.
red core- provides skeletal muscle tone, redistribution of tone when changing posture. Just stretching is a powerful work of the brain and spinal cord, for which the red nucleus is responsible. The red core ensures the normal tone of our muscles. If the red core is destroyed, decerebration rigidity occurs, while the tone sharply increases in some animals of the flexors, in others - of the extensors. And with absolute destruction, both tones increase at once, and it all depends on which muscles are stronger.
black substance– How is the excitation from one neuron transmitted to another neuron? Excitation occurs - this is a bioelectric process. He reached the end of the axon, where a chemical substance is released - a neurotransmitter. Each cell has its own mediator. The neurotransmitter is produced in the substantia nigra in nerve cells dopamine. When the substantia nigra is destroyed, Parkinson's disease occurs (fingers, head constantly tremble, or stiffness is present as a result of a constant signal going to the muscles) because there is not enough dopamine in the brain. The substantia nigra provides subtle instrumental movements of the fingers and influences all motor functions. The substantia nigra exerts an inhibitory effect on the motor cortex through the stripolidar system. In case of violation, it is impossible to perform fine operations and Parkinson's disease (stiffness, tremor) occurs.
Above - the anterior tubercles of the quadrigemina, and below - the posterior tubercles of the quadrigemina. We look with our eyes, but we see with the occipital cortex of the cerebral hemispheres, where the visual field is located, where the image is formed. A nerve departs from the eye, passes through a series of subcortical formations, reaches the visual cortex, there is no visual cortex, and we will not see anything. Anterior colliculi is the primary visual area. With their participation, an orienting reaction to a visual signal occurs. The orienting response is “what is the response?” If the anterior tubercles of the quadrigemina are destroyed, vision will be preserved, but there will be no quick reaction to the visual signal.
Posterior tubercles of the quadrigemina This is the primary hearing area. With its participation, an orienting reaction to a sound signal occurs. If the posterior tubercles of the quadrigemina are destroyed, hearing will be preserved but there will be no orienting reaction.
Seam cores is the source of another mediator serotonin. This structure and this mediator takes part in the process of falling asleep. If the nuclei of the suture are destroyed, then the animal is in a constant state of wakefulness and quickly dies. In addition, serotonin is involved in learning with positive reinforcement (this is when a rat is given cheese). Serotonin provides such character traits as forgiveness, goodwill, in aggressive people there is a lack of serotonin in the brain.
12) Thalamus - a collector of afferent impulses. Specific and nonspecific nuclei of the thalamus. The thalamus is the center of pain sensitivity.
thalamus- visual tubercle. They were the first to discover in him a relation to visual impulses. It is a collector of afferent impulses, those that come from receptors. The thalamus receives signals from all receptors, except for the olfactory ones. Infa enters the thalamus from the cortex, from the cerebellum and from the basal ganglia. At the level of the thalamus, these signals are processed, only the most important information for a person at the moment is selected, which then enters the cortex. The thalamus consists of several dozen nuclei. The nuclei of the thalamus are divided into two groups: specific and nonspecific. Through specific nuclei of the thalamus, signals arrive strictly to certain areas of the cortex, for example, visual to the occipital, auditory to the temporal lobe. And through non-specific nuclei, information diffusely enters the entire cortex in order to increase its excitability in order to more clearly perceive specific information. They prepare the bp cortex for the perception of specific information. The highest center of pain sensitivity is the thalamus. The thalamus is the highest center of pain sensitivity. Pain is necessarily formed with the participation of the thalamus, and with the destruction of some nuclei of the thalamus, pain sensitivity is completely lost, with the destruction of other nuclei, barely tolerable pains arise (for example, phantom pains are formed - pain in the missing limb).
13) Hypothalamo-pituitary system. The hypothalamus is the center of regulation of the endocrine system and motivations.
The hypothalamus and pituitary gland form a single hypothalamic-pituitary system.
Hypothalamus. The pituitary stalk departs from the hypothalamus, on which it hangs pituitary- the main endocrine gland. The pituitary gland regulates the work of other endocrine glands. The hypoplamus is connected to the pituitary gland by nerve pathways and blood vessels. The hypothalamus regulates the work of the pituitary gland, and through it the work of other endocrine glands. The pituitary gland is divided into adenohypophysis(glandular) and neurohypophysis. In the hypothalamus (this is not an endocrine gland, this is a part of the brain) there are neurosecretory cells in which hormones are secreted. This is a nerve cell, it can be excited, it can be inhibited, and at the same time hormones are secreted in it. An axon departs from it. And if these are hormones, they are released into the blood, and then it goes to the decision organs, that is, to the organ whose work it regulates. Two hormones:
- vasopressin - contributes to the preservation of water in the body, it acts on the kidneys, with its deficiency, dehydration occurs;
- oxytocin - is produced here, but in other cells, provides contraction of the uterus during childbirth.
Hormones are secreted in the hypothalamus and secreted by the pituitary gland. Thus, the hypothalamus is connected to the pituitary gland by neural pathways. On the other hand: nothing is produced in the neurohypophysis, hormones come here, but the adenohypophysis has its own glandular cells, where a number of important hormones are produced:
- ganadotropic hormone - regulates the work of the sex glands;
- thyroid-stimulating hormone - regulates the functioning of the thyroid gland;
- adrenocorticotropic - regulates the work of the adrenal cortex;
- somatotropic hormone, or growth hormone, - ensures the growth of bone tissue and the development of muscle tissue;
- melanotropic hormone - is responsible for pigmentation in fish and amphibians, in humans it affects the retina.
All hormones are synthesized from a precursor called pro-opiomelanocortin. A large molecule is synthesized, which is cleaved by enzymes, and other hormones smaller in the number of amino acids are released from it. Neuroendocrinology.
The hypothalamus contains neurosecretory cells. They produce hormones:
1) ADG (antidiuretic hormone regulates the amount of urine excreted)
2) oxytocin (provides contraction of the uterus during childbirth).
3) statins
4) liberals
5) thyroid-stimulating hormone affects the production of thyroid hormones (thyroxine, triiodothyronine)
Thyroliberin -> thyroid stimulating hormone -> thyroxine -> triiodothyronine.
The blood vessel enters the hypothalamus, where it branches into capillaries, then the capillaries gather and this vessel passes through the pituitary stalk, branches again in the glandular cells, exits the pituitary gland and carries with it all these hormones, which each go with the blood to its own gland. Why do we need this "wonderful vascular network"? There are nerve cells in the hypothalamus that terminate in the blood vessels of this wonderful vasculature. These cells produce statins and liberals - this is neurohormones. Statins inhibit the production of hormones in the pituitary gland, and liberals reinforce it. If an excess of growth hormone causes gigantism, this can be stopped with samamatostatin. On the contrary: the dwarf is injected with samatoliberin. And apparently for any hormone there are such neurohormones, but they are not yet open. For example, the thyroid gland produces thyroxine, and in order to regulate its production, the pituitary gland produces thyrotropic hormone, and in order to control thyroid-stimulating hormone, thyreostatin was not found, but thyroliberin is used perfectly. Although these are hormones, they are produced in nerve cells, therefore, in addition to endocrine effects, they have a wide range of extra-endocrine functions. Thyreoliberin is called panactivin, because it improves mood, increases efficiency, normalizes blood pressure, accelerates healing in case of spinal cord injuries, it cannot be used alone for disorders in the thyroid gland.
Previously, the functions associated with neurosecretory cells and cells that produce neurofebtides have been considered.
The hypothalamus produces statins and liberins, which are included in the body's stress response. If the body is affected by some harmful factor, then the body must somehow respond - this is the stress reaction of the body. It cannot proceed without the participation of statins and liberins, which are produced in the hypothalamus. The hypothalamus is necessarily involved in the response to stress.
The next function of the hypothalamus is:
It contains nerve cells that are sensitive to steroid hormones, that is, sex hormones to both female and male sex hormones. This sensitivity provides the formation of the female or male type. The hypothalamus creates the conditions for motivating behavior according to the male or female type.
A very important function is thermoregulation, in the hypothalamus there are cells that are sensitive to blood temperature. Body temperature can change depending on the environment. Blood flows through all the structures of the brain, but thermoreceptive cells that detect the slightest changes in temperature are found only in the hypothalamus. The hypothalamus turns on and organizes two body responses, either heat production or heat loss.
food motivation. Why does a person feel hungry?
The signal system is the level of glucose in the blood, it should be constant ~ 120 milligrams % - s.
There is a mechanism of self-regulation: if our blood glucose level decreases, liver glycogen begins to break down. On the other hand, glycogen stores are not enough. In the hypothalamus there are glucoreceptor cells, i.e. cells that register the level of glucose in the blood. Glucoreceptor cells form hunger centers in the hypothalamus. When the blood glucose level drops, these blood glucose-sensitive cells become excited, and a feeling of hunger occurs. At the level of the hypothalamus, only food motivation arises - a feeling of hunger, in order to search for food, the cerebral cortex must be connected, with its participation a true food reaction occurs.
The satiety center is also located in the hypothalamus, it inhibits the feeling of hunger, which prevents us from overeating. When the satiety center is destroyed, overeating occurs and, as a result, bulimia.
The hypothalamus also has a thirst center - osmoreceptive cells (osmotic pressure depends on the concentration of salts in the blood). Osmoreceptive cells register the level of salts in the blood. With an increase in salts in the blood, osmoreceptive cells are excited, and drinking motivation (reaction) occurs.
The hypothalamus is the highest center of regulation of the autonomic nervous system.
The anterior hypothalamus mainly regulates the parasympathetic nervous system, while the posterior hypothalamus regulates the sympathetic nervous system.
The hypothalamus provides only motivation and purposeful behavior of the cerebral cortex.
14) Neuron - structural features and functions. Differences between neurons and other cells. Glia, blood-brain barrier, cerebrospinal fluid.
I First, as we have already noted, in their diversity. Every nerve cell consists of a body - catfish and offshoots. Neurons are different:
1. by size (from 20 nm to 100 nm) and shape of the soma
2. by the number and degree of branching of short processes.
3. according to the structure, length and branching of axon endings (laterals)
4. by the number of spines
II Neurons also differ in functions:
a) perceiving information from the external environment
b) transmitting information to the periphery
in) processing and transmit information within the CNS,
G) exciting,
e) brake.
III Differ in chemical composition: a variety of proteins, lipids, enzymes are synthesized and, most importantly, - mediators .
WHY, WITH WHAT FEATURES IS IT RELATED TO?
This variety is defined high activity of the genetic apparatus neurons. During neuronal induction, under the influence of neuronal growth factor, NEW GENES are switched on in the cells of the ectoderm of the embryo, which are characteristic only for neurons. These genes provide the following features of neurons ( the most important properties):
A) The ability to perceive, process, store and reproduce information
B) DEEP SPECIALIZATION:
0. Synthesis of specific RNA;
1. No reduplication DNA.
2. Proportion of genes capable of transcriptions, make up in neurons 18-20%, and in some cells 40% (in other cells - 2-6%)
3. Ability to synthesize specific proteins (up to 100 in one cell)
4. The uniqueness of the lipid composition
C) Food Privilege => Level Dependence oxygen and glucose in blood.
Not a single tissue in the body is in such a dramatic dependence on the level of oxygen in the blood: 5-6 minutes of respiratory arrest and the most important structures of the brain die, and first of all - the cerebral cortex. A decrease in glucose levels below 0.11% or 80 mg% - hypoglycemia may occur and then coma.
And on the other hand, the brain is fenced off from the blood flow of the BBB. He does not let anything that could harm them into the cells. But, unfortunately, not all - many low-molecular toxic substances pass through the BBB. And pharmacologists always have a task: does this drug pass through the BBB? In some cases, this is necessary when it comes to diseases of the brain, in others it is indifferent to the patient if the drug does not damage nerve cells, and in still others this should be avoided. (NANOPARTICLES, ONCOLOGY).
Sympathetic NS is excited and stimulates the work of the adrenal medulla - the production of adrenaline; in the pancreas - glucagon - breaks down glycogen in the kidneys to glucose; glucocarticoids produced. in the adrenal cortex - provides gluconeogenesis - the formation of glucose from ...)
And yet, with all the variety of neurons, they can be divided into three groups: afferent, efferent and intercalary (intermediate).
15) Afferent neurons, their functions and structure. Receptors: structure, functions, formation of an afferent volley.
On its ventral surface there are two massive bundles of nerve fibers - the legs of the brain, through which signals are carried from the cortex to the underlying structures of the brain.
Rice. 1. The most important structural formations of the midbrain (cross section)
In the midbrain, there are various structural formations: the quadrigemina, the red nucleus, the substantia nigra, and the nuclei of the oculomotor and trochlear nerves. Each formation performs a specific role and contributes to the regulation of a number of adaptive reactions. All ascending paths pass through the midbrain, transmitting impulses to the thalamus, cerebral hemispheres and cerebellum, and descending paths, conducting impulses to the medulla oblongata and spinal cord. The neurons of the midbrain receive impulses through the spinal and medulla oblongata from the muscles, visual and auditory receptors along the afferent nerves.
Anterior colliculi are the primary visual centers, and they receive information from the visual receptors. With the participation of the anterior tubercles, visual orienting and watchdog reflexes are carried out by moving the eyes and turning the head in the direction of the action of visual stimuli. The neurons of the posterior tubercles of the quadrigemina form the primary auditory centers and, upon receiving excitation from the auditory receptors, ensure the implementation of auditory orienting and sentinel reflexes (the animal's auricles tense up, it becomes alert and turns its head towards a new sound). The nuclei of the posterior tubercles of the quadrigemina provide a sentinel adaptive reaction to a new sound stimulus: redistribution of muscle tone, increased tone of the flexors, increased heart and breathing contractions, increased blood pressure, i.e. the animal prepares for defense, flight, attack.
black substance receives information from muscle receptors and tactile receptors. It is associated with the striatum and the globus pallidus. Neurons of the substantia nigra are involved in the formation of an action program that coordinates the complex acts of chewing, swallowing, as well as muscle tone and motor reactions.
red core receives impulses from muscle receptors, from the cerebral cortex, subcortical nuclei and cerebellum. It has a regulatory effect on the motor neurons of the spinal cord through the nucleus of Deiters and the rubrospinal tract. The neurons of the red nucleus have numerous connections with the reticular formation of the brain stem and, together with it, regulate muscle tone. The red nucleus has an inhibitory effect on the extensor muscles and an activating effect on the flexor muscles.
Eliminating the connection of the red nucleus with the reticular formation of the upper part of the medulla oblongata causes a sharp increase in the tone of the extensor muscles. This phenomenon is called decerebrate rigidity.
|
Name |
midbrain functions |
|
Kernels of the roof of the superior and inferior tubercles of the quadrigemina |
Subcortical centers of vision and hearing, from which the tectospinal path originates, through which orienting auditory and visual reflexes are carried out |
|
The nucleus of the longitudinal medial bundle |
Participates in providing a combined turn of the head and eyes to the action of unexpected visual stimuli, as well as irritation of the vestibular apparatus |
|
Nuclei III and IV pairs of cranial nerves |
They participate in the combination of eye movement due to the innervation of the external muscles of the eye, and the fibers of the autonomic nuclei after switching in the ciliary ganglion innervate the muscle that narrows the pupil and the muscle of the ciliary body |
|
Red cores |
They are the central link of the extrapyramidal system, since the paths from the cerebellum (tr. cerebellotegmenlalis) and the basal nuclei (tr. pallidorubralis) end on them, and the rubrospinal path begins from these nuclei |
|
black substance |
It has a connection with the striatum and the cortex, participates in complex coordination of movements, regulation of muscle tone and posture, as well as in coordinating the acts of chewing and swallowing, is part of the extrapyramidal system |
|
Kernels of the reticular formation |
Activating and inhibitory effects on the nuclei of the spinal cord and various areas of the cerebral cortex |
|
Gray central periaqueductal substance |
Part of the antinociceptive system |
The structures of the midbrain are directly involved in the integration of heterogeneous signals necessary for the coordination of movements. With the direct participation of the red nucleus, the black substance of the midbrain, the neural network of the stem movement generator and, in particular, the eye movement generator, is formed.
Based on the analysis of signals entering the stem structures from proprioreceptors, vestibular, auditory, visual, tactile, pain and other sensory systems, a flow of efferent motor commands is formed in the stem movement generator, sent to the spinal cord along descending pathways: rubrospinal, retculospinal, vestibulospinal, tectospinal. In accordance with the commands developed in the brainstem, it becomes possible to carry out not just the contraction of individual muscles or muscle groups, but the formation of a certain body posture, maintaining the balance of the body in various postures, performing reflex and adaptive movements when performing various types of body movement in space (Fig. 2 ).
Rice. 2. The location of some nuclei in the brain stem and hypothalamus (R. Schmidt, G. Thews, 1985): 1 - paraventricular; 2 - dorsomedial: 3 - preoptic; 4 - supraoptic; 5 - back
The structures of the stem movement generator can be activated by arbitrary commands that come from the motor areas of the cerebral cortex. Their activity can be enhanced or inhibited by signals from sensory systems and the cerebellum. These signals can modify already running motor programs so that their execution changes to meet new requirements. So, for example, the adaptation of a posture to purposeful movements (as well as the organization of such movements) is possible only with the participation of the motor centers of the cerebral cortex.
The red nucleus plays an important role in the integrative processes of the midbrain and its stem. Its neurons are directly involved in the regulation, distribution of skeletal muscle tone and movements that ensure the preservation of the normal position of the body in space and the adoption of a posture that creates readiness to perform certain actions. These influences of the red nucleus on the spinal cord are realized through the rubrospinal tract, the fibers of which terminate on the intercalary neurons of the spinal cord and have an excitatory effect on the a- and y-motor neurons of the flexors and inhibit most of the neurons of the extensor muscles.
The role of the red nucleus in the distribution of muscle tone and maintaining body posture is well demonstrated in animal experiments. When the brainstem is cut (decerebrated) at the level of the midbrain below the red nucleus, a condition develops called decerebrate rigidity. The limbs of the animal become straightened and tense, the head and tail are thrown back to the back. This position of the body occurs due to an imbalance between the tone of the antagonist muscles in the direction of a sharp predominance of the extensor tone. After transection, the inhibitory effect of the red nucleus and the cerebral cortex on the extensor muscles is eliminated, and the excitatory effect of the reticular and vestibular (Deigers) nuclei on them remains unchanged.
Decerebrate rigidity occurs immediately after crossing the brainstem below the level of the red nucleus. In the origin of rigidity, the y-loop is of paramount importance. Rigidity disappears after the intersection of the posterior roots and the cessation of the influx of afferent nerve impulses to the neurons of the spinal cord from the muscle spindles.
The vestibular system is related to the origin of rigidity. Destruction of the lateral vestibular nucleus eliminates or reduces the tone of the extensors.
In the implementation of the integrative functions of the structures of the brain stem, an important role is played by the substantia nigra, which is involved in the regulation of muscle tone, posture and movements. It is involved in the integration of signals necessary to coordinate the work of many muscles involved in the acts of chewing and swallowing, and affects the formation of respiratory movements.
Through the substantia nigra, the motor processes initiated by the stem generator of movements are influenced by the basal ganglia. There are two-way connections between the substantia nigra and the basal ganglia. There is a bundle of fibers that conducts nerve impulses from the striatum to the substantia nigra, and a path that conducts impulses in the opposite direction.
The substantia nigra also sends signals to the nuclei of the thalamus, and further along the axons of the thalamic neurons, these signal flows reach the cortex. Thus, the substantia nigra participates in the closing of one of the neural circuits through which signals circulate between the cortex and subcortical formations.
The functioning of the red nucleus, the substantia nigra and other structures of the stem movement generator is controlled by the cerebral cortex. Its influence is carried out both through direct connections with many stem nuclei, and indirectly through the cerebellum, which sends bundles of efferent fibers to the red nucleus and other stem nuclei.
