Brain. Medulla. Cranial nerve nuclei

The medulla oblongata is a direct continuation of the spinal cord. The lower border is the exit site of the roots of the 1st cervical spinal nerve or the decussation of the pyramids, the upper border is the posterior edge of the bridge. The medulla oblongata is about 25 mm long and has the shape of a truncated cone. The anterior surface of the medulla oblongata is divided anterior median fissure, on the sides of which there are longitudinal rollers - pyramids. The pyramids are formed by bundles of nerve fibers of the pyramidal pathways. Pyramidal tract fibers connect the cortex big brain with the nuclei of the cranial nerves and the anterior horns of the spinal cord. On each side of the pyramid there is olive, separated from the pyramid anterior lateral groove.

The posterior surface of the medulla oblongata is divided posterior median sulcus. On the sides of the groove there are continuations of the posterior cords of the spinal cord, which diverge upward and pass into inferior cerebellar peduncles. These legs limit the rhomboid fossa below. The posterior cord in the lower parts of the medulla oblongata consists of two bundles- wedge-shaped(lateral) and thin(medially), on which tubercles containing wedge-shaped And thin kernels.

The medulla oblongata consists of white and gray matter.

Gray matter of the medulla oblongata represented by the nuclei of IX, X, XI, XII pairs of cranial nerves, olives, reticular formation, centers of respiration and circulation.

White matter formed by nerve fibers that make up the corresponding pathways. The motor pathways (descending) are located in the anterior parts of the medulla oblongata, the sensory (ascending) pathways lie more dorsally.

Reticular formation is a collection of cells, cell clusters and nerve fibers that form a network located in the brain stem (medulla oblongata, pons and midbrain). The reticular formation is connected to all sense organs, motor and sensory areas of the cerebral cortex, the thalamus and hypothalamus, and the spinal cord. It regulates the level of excitability and tone of various parts of the nervous system, including the cerebral cortex, and is involved in the regulation of the level of consciousness, emotions, sleep and wakefulness, autonomic functions, and purposeful movements.

Above the medulla oblongata is the pons, and posterior to it is the cerebellum.

Bridge.

Bridge ( Pons) has the appearance of a lying transversely thickened ridge, from the lateral side of which there are middle cerebellar peduncles. The posterior surface of the pons, covered by the cerebellum, participates in the formation of the rhomboid fossa. The anterior surface below forms a clear boundary with the medulla oblongata, and at the top the pons borders the cerebral peduncles. The anterior surface of the pons is transversely striated due to the transverse direction of the fibers that go from the own nuclei of the pons to the middle cerebellar peduncles and further to the cerebellum. On the front surface of the bridge along the midline there is a longitudinal basilar groove, in which the artery of the same name lies. In the frontal section through the bridge, two of its parts are visible: the anterior ( basilar) and back (tire).

In the tegmentum of the bridge there is a reticular formation, the nuclei of the V, VI, VII, VIII pairs of cranial nerves lie and ascending pathways pass through.

The anterior (basilar) part of the bridge consists of nerve fibers that form pathways, among which there are cell clusters - nuclei. The pathways of the basilar part connect the cerebral cortex with the spinal cord, with the motor nuclei of the cranial nerves and with the cerebellar hemisphere cortex. Between the nerve fibers of the pathways lie own bridge cores. On the border between both parts of the bridge lies trapezoid body, formed by the fibers of the conductive path of the auditory analyzer.

The posterior (dorsal) surface of the pons and medulla oblongata serves as the bottom of the IV ventricle, which in its origin is the cavity of the rhombencephalon.

IV ventricle downwards it continues into the narrow central canal of the spinal cord, and upwards into the cerebral aqueduct - the cavity of the midbrain. The bottom of the fourth ventricle due to its shape is called diamond-shaped fossa. The superior sides of the fossa are bounded by the superior cerebellar peduncles, and the inferior sides are formed by the inferior cerebellar peduncles. The median groove divides the bottom of the rhomboid fossa into two symmetrical halves. On both sides of the furrow, the right and left are visible facial tubercles. In the thickness of the facial tubercle lies the nucleus of the VI pair of the cranial abducens nerve, and in the depths and slightly laterally lies the nucleus of the VII pair of the cranial nerve - the facial nerve. Below, the medial eminence becomes triangle of the hypoglossal nerve, lateral to which is located triangle of the vagus nerve. In the triangles, in the thickness of the brain substance, lie the nuclei of the nerves of the same name. The lateral sections of the rhomboid fossa are called vestibular fields, since in their thickness lie the auditory and vestibular nuclei of the vestibulocochlear nerve - the VIII pair of the cranial nerves. Transverse ones extend from the auditory nuclei to the median sulcus. brain stripes, located on the border between the medulla oblongata and the pons and are the fibers of the conductive path of the auditory analyzer.

In the thickness of the rhomboid fossa lie the nuclei of the V, VI, VII, VIII, IX, X, XI, XII pairs of the cranial nerves. The sensory nuclei of the cranial nerves are located laterally. More medially than them lie the autonomic nuclei, and the most medial are the motor nuclei.

Trigeminal nerve(V pair of cranial nerves) has four nuclei, including motor and sensitive - the pontine nucleus of the midbrain tract and the nucleus of the spinal tract of the trigeminal nerve. Abducens nerve(VI pair of cranial nerves) has only one motor nucleus. U facial nerve(VII pair of cranial nerves) three nuclei: the motor nucleus, the sensitive nucleus of the solitary tract and the parasympathetic - superior salivary nucleus. vestibulocochlear nerve(VIII pair of the cranial nerve) has two groups of nuclei: two auditory cochlear (anterior and posterior) and four vestibular: medial, lateral, superior and inferior. Glossopharyngeal nerve(IX pair of the cranial nerve) has three nuclei: the motor double, common to the IX and X pairs, the sensitive nucleus of the solitary tract (common to the VII, IX, X pairs) and the parasympathetic - lower salivary. At the vagus nerve(X pairs) three nuclei: double motor (common with IX pair) and sensitive, as well as parasympathetic - the posterior nucleus of the vagus nerve. Accessory nerve(XI pair of cranial nerves) has only a motor nucleus. U hypoglossal nerve(XII pairs of the cranial nerves) is also one motor nucleus.

Through three holes in the roof, the cavity of the fourth ventricle communicates with the subarachnoid space. In the thickness of the vascular base of the fourth ventricle there is its choroid plexus, which produces cerebrospinal fluid - cerebrospinal fluid

Above the fourth ventricle, which is essentially the cavity of the pons and medulla oblongata, is the cerebellum, or, as it is called, the “small brain.”

Functions of the medulla oblongata and pons. The medulla oblongata and the pons perform essential functions. The sensitive nuclei of the cranial nerves, located in these parts of the brain, receive nerve impulses from the scalp, mucous membranes of the mouth and nasal cavity, pharynx and larynx, from the digestive and respiratory organs, from the organ of vision and organ of hearing, from the vestibular apparatus, heart and blood vessels . Along the axons of the cells of the motor and autonomic (parasympathetic) nuclei of the medulla oblongata and the pons, impulses follow not only to the skeletal muscles of the head, but also to the smooth muscles of the digestive, respiratory and cardiovascular systems, to the salivary and other glands.

Through the nuclei of the medulla oblongata, many reflex acts are performed, including protective ones (coughing, blinking, tearing, sneezing). The nuclei of the medulla oblongata are involved in reflex acts of swallowing and the secretory function of the digestive glands. The vestibular nuclei, in which the vestibulospinal tract originates, perform complex reflex acts of redistribution of skeletal muscle tone, balance, and provide a “standing posture.” These reflexes are called installation reflexes. The most important respiratory and cardiovascular centers located in the medulla oblongata are involved in the regulation of respiratory function, the activity of the heart and blood vessels. Damage to these centers leads to death.

LECTURE.

BRAIN DEVELOPMENT. DIVISIONS OF THE BRAIN.

In the third week of uterine development, the cranial portion of the neural tube is divided into 3 brain vesicles (anterior, middle, posterior (or rhomboid).

In the fourth week, vesicles 1 and 3 divide into two parts - the 5 vesicle stage of brain development.

Thus, the brain consists of trunk (medulla oblongata, pons and midbrain), subcortical department (diencephalon and basal ganglia) and bark cerebral hemispheres .

MEDULLA.

The medulla oblongata is a direct continuation of the spinal cord and basically retains its shape and structure. It is located on the slope of the skull in the posterior cranial fossa. The length of the brain is 2-3 cm. It has the shape of a truncated cone or onion. Unlike the spinal cord, it does not have a metameric, repeating structure. Gray matter is located in the center, and the nuclei are located on the periphery.

The anterior surface is divided by the anterior median fissure; on the sides there are pyramids (anterior cords), formed by bundles of nerve fibers of the pyramidal tracts, partially intersecting (pyramid decussation). On each side of the pyramids there are olives (the ventral part of the lateral funiculi), separated from the pyramid by the anterior lateral groove.

The posterior surface of the medulla oblongata is divided by the posterior median sulcus. On the sides there are thickenings - thin and wedge-shaped bundles of the posterior cords of the spinal cord with their tubercles in the upper part. The posterior lateral sulcus separates the posterior funiculi from the dorsal part of the lateral funiculi, represented by the inferior cerebellar peduncles.

Between the pyramid and the olive, the XII pair of cranial nerves (hypoglossal) emerges from the anterior lateral groove, and the roots of the IX, X, XI pairs of cranial nerves (glossopharyngeal, vagus, accessory) emerge from the posterior lateral groove.

The upper part of the posterior surface has the shape of a triangle and forms the bottom of the fourth ventricle.

Internal structure medulla oblongata.

The medulla oblongata contains gray matter nuclei related to balance, coordination of movements, regulation of metabolism, respiration and blood circulation.

Gray matter brain represented by:

1. Olive Kernel, which is associated with the dentate nucleus of the cerebellum and is the intermediate nucleus of balance.

2. Reticular formation, which is a collection of cellular clusters, cells and nerve fibers located in the brain stem and forming a network. The reticular formation is connected to all sensory organs, motor and sensory areas of the CPB, the thalamus and hypothalamus, and the spinal cord. It regulates the level of excitability and tone of various parts of the central nervous system, including the CP, and is involved in the regulation of the level of consciousness, emotions, sleep and wakefulness, autonomic functions, and purposeful movements.

3. Nuclei IX-XII pairs of cranial nerves related to the innervation of the viscera. Of particular importance is the vagus (X) nerve, which innervates the respiratory, digestive, circulatory, etc. organs.

4. Vital centers of respiration and circulation Therefore, if the medulla oblongata is damaged, death may occur due to the cessation of breathing and cardiac activity.

White matter The medulla oblongata contains long and short processes. The long ones include the descending pyramidal tracts passing in the anterior cords of the spinal cord, which partly intersect in the area of ​​the pyramids.

Short pathways include bundles of nerve fibers that connect individual nuclei of the gray matter, as well as the nuclei of the medulla oblongata with neighboring parts of the brain.

Functions of the medulla oblongata.

Like the spinal cord, the medulla oblongata performs two functions: reflex and conductive.

The medulla oblongata, due to its nuclear formations and reticular formation, is involved in the implementation of vegetative, somatic, gustatory, auditory, and vestibular reflexes. Here are the centers for chewing, sucking, swallowing, secretion of saliva and gastric juice, and protective reflexes (coughing, sneezing, vomiting). A feature of the medulla oblongata is that its nuclei, being excited sequentially, ensure the execution of complex reflexes that require the sequential activation of different muscle groups, which is observed, for example, when swallowing.

The conductor function of the medulla oblongata is to transmit impulses from the spinal cord to the brain. It contains ascending and descending pathways. There are pathways connecting the nuclei of the medulla oblongata and pons with other parts of the central nervous system.

HINDBRAIN.

From the substance adjacent to the wall; brain bladder forms the hindbrain, consisting of pons and cerebellum .

Pons.

It is located on the slope of the skull above the medulla oblongata and performs sensory, conductive, motor, integrative, and reflex functions. It has the appearance of a transverse shaft, separated by transverse grooves from the medulla oblongata (bottom) and midbrain (top). The lateral border of the bridge is the conventional line from which the V pair of cranial nerves (trigeminal) emerges. Here it borders with the middle cerebellar peduncles. The anterior median sulcus continues along the anterior surface of the pons, in which the main artery of the brain lies. On both sides of the median sulcus there are arcuate elevations - pyramidal tracts.

Gray matter is located inside the pons and white matter is located outside. Its front part (base) mainly consists of white matter, these are longitudinal and transverse fibers. In the dorsal sections of the bridge there are ascending sensory pathways, and in the ventral sections there are descending pyramidal and extrapyramidal pathways. There are also fiber systems here that provide bilateral communication between the cerebellum and the cerebral cortex. In the posterior part of the bridge (tire) there are nuclei: the trigeminal nerve (V pair), abducens (VI pair), facial (VII pair), vestibulocochlear (VIII pair), as well as fibers of the medial loop coming from the medulla oblongata, on which the reticular formation of the bridge is located. On top of the reticular formation is the bottom of the rhomboid fossa. The pathways of the medulla oblongata also continue in the dorsal (posterior) part of the pons.

Cerebellum.

The cerebellum is located under the occipital lobes of the cerebral hemispheres and lies in the occipital fossa. Its maximum width is 11.5 cm, length - 3-4 cm. The cerebellum is divided into hemispheres, and between them is the cerebellar vermis. The surface of the cerebellum is covered with gray matter or cortex, which forms convolutions separated from each other by grooves. In the thickness of the cerebellum there is white matter, consisting of fibers that provide intracerebral connections.

The cerebellar cortex is three-layered, consisting of an outer molecular layer, a ganglion (or Purkinje cell layer) and a granular (granular) layer. The cortex contains five types of neurons: granular, stellate, basket, Golgi and Purkinje cells, which have sufficient complex system connections. Between the cerebellum and the pons with the medulla oblongata there is the fourth ventricle filled with spinal fluid.

In the molecular layer there are 3 types of interneurons: basket, short- and long-processed stellate cells.

In the ganglion layer there are Purkinje cells, the axons of which from the cortex penetrate into the white matter to the cerebellar nuclei.

In the granular (granular) layer there are granular cells, Golgi cells. The axons of granule cells ascend to the surface, branch in a T-shape, forming parallel fibers.

Cerebellar nuclei located deep in the cerebellum in the thickness of the white matter above the fourth cerebral ventricle - this is tent core, corky core, globose and denticulate core. The largest nucleus of the cerebellum is the dentate nucleus. In all 4 nuclei, neurons have a similar structure. Its conductive pathways begin from the neurons of the cerebellar nuclei. The cerebellar nuclei play important role in the implementation of various motor functions and their damage causes their disruption:

Tent core – body balance is disturbed,

Corky and spherical nuclei - the functioning of the muscles of the neck and torso is disrupted,

Dentate nucleus - the functioning of the muscles of the limbs is disrupted.

Pathways. The cerebellum is connected to other parts by three pairs of peduncles.

The lower peduncles of the cerebellum connect it with the medulla oblongata and spinal cord, the middle ones connect the cerebellum with the pons, and the upper ones consist of nerve fibers passing in both directions to the midbrain.

The peculiarities of the connections of the cerebellum are, on the one hand, a rich spectrum of afferent impulses (impulses from receptors of the skin, muscles and tendons), and on the other hand, the presence of connections mediated by the thalamus with motor systems allows it to perform the functions of correction of movement. Thus, without direct access to motor neurons, the cerebellum provides fine coordination of the activity of motor systems.

Functions of the cerebellum.

The cerebellum coordinates movements, makes them clear and smooth, plays an important role in maintaining body balance, and influences muscle tone. When the cerebellum is damaged, a person experiences decreased muscle tone, gait disturbance, and speech slows down. The cerebellum also takes part in the regulation of some autonomic functions (blood composition, vascular reflexes, gastrointestinal tract).

IV STOMACH.

IV ventricle represents the remains of the cavities of the IV and V brain vesicles. Below the ventricle communicates with central channel of the spinal cord, at the top it passes into the midbrain aqueduct, bounded above by the pons, below by the medulla oblongata, and behind by the cerebellum. The IV ventricle resembles a tent, in which a bottom and a roof are distinguished. The bottom of the IV ventricle has the shape of a rhombus (therefore it is called rhomboid fossa), it is as if pressed into the posterior surface of the medulla oblongata and the pons. The lateral angles of the ventricle end blindly in the form of 2 pockets that bend around the lower cerebellar peduncles.

The roof of the IV ventricle has the shape of a tent and is composed of two cerebral sails: upper and lower.

At the bottom of the IV ventricle there is a median groove and two medullary stripes perpendicular to it. The rhomboid fossa contains the nuclei of the V – XII pairs of cranial nerves. Pattern of nuclear placement: the middle position is occupied by the motor nuclei, the lateral position is occupied by the sensory nuclei, the intermediate position is occupied by the nuclei of the autonomous (vegetative) nervous system.

MIDDLE BRAIN.

The midbrain is formed from the substance adjacent to the wall of the third medullary vesicle. It has a roof and legs. The cavity of the midbrain is the cerebral aqueduct.

Roof of the midbrain It is a plate of the quadrigeminalis, which is located above the cerebral aqueduct. It consists of four elevations - 4 mounds (quadrigeminals), shaped like hemispheres, which are separated from each other by two grooves intersecting at right angles. Inside them there is an accumulation of gray matter - nuclei, which are subcortical centers: in the upper colliculi there are subcortical visual centers, in the lower ones there are subcortical hearing centers. From each of the mounds, thickenings extend in the lateral direction in the form of a roller - the handle of the mound. The handle of the superior colliculus is located posterior to the thalamus and goes to the lateral geniculate body, and partly continues into the optic tract. The handle of the inferior colliculus is directed towards the medial geniculate body.

Brain stems in the form of two thick white ridges they emerge from the pons, are directed forward and laterally (diverging at an acute angle) to the right and left hemispheres of the cerebrum. A frontal section of the midbrain shows that the roof of the midbrain (collices) consists of gray matter (gray and white layers of the superior colliculus and the nucleus of the inferior colliculus), which is externally covered with a thin layer of white matter. On a cross section of the midbrain, in the cerebral peduncle it clearly stands out for its dark color(due to the melanin pigment contained in nerve cells) black matter(black substance) . It divides the cerebral peduncle into two sections: posterior (dorsal) - the tegmentum of the midbrain and anterior (ventral) - the base of the cerebral peduncle. In the tegmentum of the midbrain, around the aqueduct, there is a central gray matter, in which the nuclei of the midbrain lie and the ascending pathways pass. Tire cores:

1) nucleus of the third pair of cranial nerves (oculomotor), which consists of a somatic nucleus and 2 autonomic nuclei.

2) nucleus of the IV pair of cranial nerves (trochlear).

3) the red nucleus, from which the red nucleus-spinal tract begins.

The base of the cerebral peduncle consists entirely of white matter; descending pathways pass here.

Midbrain plumbing(Aqueduct of Sylvius) - a narrow canal about 1.5-2 cm long, connects the cavities of the III and IV ventricles. It contains cerebrospinal fluid. In its origin, the cerebral aqueduct is a derivative of the cavity of the middle cerebral bladder.

DENAMEBRAIN

During embryogenesis, the diencephalon develops from the wall of the second brain vesicle. The diencephalon is located under corpus callosum and consists of the thalamus, epithalamus, metathalamus and hypothalamus.

Thalamus (visual thalamus) They are an ovoid-shaped accumulation of gray matter. The anterior end of the thalamus is pointed, and the posterior end (cushion - subcortical centers of vision) is expanded and thickened. The thalamus is a large subcortical sensory center through which various afferent pathways pass into the cerebral cortex (the collector of all types of sensitivity). The thalamus receives signals from the visual, auditory, gustatory, skin, muscle systems, from the nuclei of the cranial nerves, brainstem, cerebellum, medulla oblongata and spinal cord. Its nerve cells are grouped into a large number of cores (up to 40). The processes of thalamic neurons are directed partly to the nuclei of the striatum of the telencephalon (in this regard, the thalamus is considered as a sensitive center of the extrapyramidal system), partly to the cerebral cortex, forming thalamocortical pathways.

Thus, the thalamus is the subcortical center of all types of sensitivity, except for the olfactory. The ascending (afferent) pathways, through which information from various receptors are transmitted, are approached and switched.

In addition to the thalamus, the diencephalon also includes its areas:

Hypothalamus– phylogenetic old department the diencephalon, which plays an important role in maintaining the constancy of the internal environment and ensuring the integration of the functions of the autonomic, endocrine and somatic systems. The hypothalamus is involved in the formation of the floor of the third ventricle. The hypothalamus includes the optic chiasm, optic tract, gray tubercle with infundibulum and mastoid body.

Optic chiasm (chiasma)– the place in the brain where the optic nerves (II pair) coming from the right and left eyes meet and partially cross. It has the appearance of a transversely lying ridge, on each side, laterally and posteriorly, continuing into the optic tract, which passes behind the anterior perforated substance, bends around the cerebral peduncle from the lateral side and ends with two roots in the subcortical centers of vision. The larger lateral root approaches the lateral geniculate body, and the thinner medial root goes to the superior colliculus of the midbrain roof.

Behind the optic chiasm is a gray tubercle. Downwards, the gray tubercle passes into a funnel, which connects to the pituitary gland. The walls of the gray tuberosity are formed by a thin plate of gray matter containing gray tuberous nuclei. The nerve cells that make up the gray tubercle form the nuclei of the autonomic nervous system, influencing heat regulation and metabolism (water-salt, protein, fat metabolism, etc.), and also being a motivational center (appetite, thirst, rage, pleasure).

The mastoid bodies are located anteriorly between the gray tubercle. They look like two small, about 0.5 cm in diameter each, spherical formations white. The white matter is located only on the outside of the mastoid body. Inside there is gray matter, which forms the nuclei of the mammillary body. According to their function, the mammillary bodies belong to the subcortical olfactory centers.

Epithalamus. The epithalamic region is located dorsal to the visual thalamus and occupies a relatively small volume. It consists of the medullary striae, a triangle of leashes formed as an extension of the lower part of the medullary striae of the thalamus. The triangles are connected by leashes. The unpaired pineal body, or epiphysis, a conical formation about 6 mm long, is suspended on leashes - paired cords starting from the triangle. The pineal gland is an endocrine gland.

In the pineal body of adults, especially in old age, there are often bizarre deposits that give the pineal gland a certain resemblance to fir cone, which explains its name.

Metathalamus represented by the lateral and medial geniculate bodies - paired formations. They have an oblong-oval shape and are connected to the colliculi of the roof of the midbrain using the handles of the superior and inferior colliculi.

The metathalamus consists of gray matter. The lateral geniculate body, right and left, is the subcortical, primary center of vision. Nerve fibers of the optic tract (from the retina) approach the neurons of its nucleus. The axons of these neurons go to the visual cortex. The medial geniculate bodies are the subcortical primary hearing centers.

III VENTRICLE

III ventricle It is a narrow vertical slit that serves as a continuation of the aqueduct forward into the diencephalon region. On the sides of its anterior part, the third ventricle communicates with the right and left interventricular foramina with the lateral ventricles lying inside the hemispheres. The lateral walls of the third ventricle are formed by the medial sides of the visual tuberosities. The floor of the third ventricle is made of the following entities(from front to back): optic chiasm, infundibulum, gray tuberosity, mastoid bodies and posterior perforated space. The roof is formed by the ependyma, which is part of the choroid plexuses of the third and lateral ventricles.

END BRAIN

The telencephalon (forebrain) is formed from the substance adjacent to the wall of the first cerebral bladder. It is divided along the midline by a deep vertical fissure into the right and left hemisphere, connected to each other using corpus callosum. In each hemisphere there are: cerebral cortex– a layer of gray matter (2.5-5 mm) lying outside, and white matter, located inside and acting as conductive pathways. In addition, in the thickness of each hemisphere there is an accumulation of gray matter - basal ganglia(ganglia), and also has a cavity - lateral ventricle. The surface of the cerebral hemispheres is indented by numerous furrows, between which there are elevations called convolutions. Due to this relief, the surface area of ​​the cortex increases. In an adult it is 2200 cm².

In each hemisphere there are three surfaces: medial, superolateral, And lower, or the base of the brain. Deep (primary) sulci divide each hemisphere into lobes: frontal, parietal, temporal, occipital, limbic and insula. The lateral sulcus separates the temporal lobe from the frontal and parietal lobes. The central sulcus is the frontal from the parietal. The parieto-occipital sulcus separates the parietal and occipital lobes on the medial surface of the hemispheres. The insular lobe is located deep in the lateral sulcus. The limbic (marginal) lobe consists of 3 convolutions:

1. cingulate gyrus, which is separated above by the cingulate groove, and below by the groove of the corpus callosum;

2. parahippocampal gyrus

3. hook.

Secondary, tertiary and other grooves divide each lobe into corresponding convolutions.

The structure of the cortex.

The cortex is phylogenetically the youngest and at the same time complex part of the brain, designed for processing sensory information, forming behavioral reactions body.

The cortex consists of 6 layers of cells. Cytoarchitecture- This is the location of neurons in the cortex.

1. Molecular layer– small neurons and fibers. Afferent thalamocortical fibers from the nonspecific nuclei of the thalamus come here, regulating the level of excitability of cortical neurons.

2. Outer granular layer formed by small granule-shaped neurons and small pyramidal cells.

3. Outer pyramidal layer consists of pyramidal cells of different sizes. Functionally, layers II and III of the cortex unite neurons, the processes of which provide cortico-cortical associative connections.

4. Inner granular layer formed by stellate cells. Afferent thalamocortical fibers coming from the projection nuclei of the thalamus end here.

5. Inner pyramidal layer includes large pyramidal cells - Betz cells, the axons of which go to the brain and spinal cord.

6. Polymorphic layer (multiform)– multiform neurons having a triangular and fusiform shape.

Myeloarchitecture- This is the distribution of fibers in the cerebral cortex. There are 3 types of fibers:

1 . Associative fibers are short and long. They unite the cells of neighboring convolutions: in one lobe they are short, the cells of the lobes in one hemisphere are long.

2 . Commissural– connect the corresponding lobes of the left and right hemispheres, form the basis of the corpus callosum.

3 . Projection– pass from the cortex to the lower parts of the brain and in the opposite direction.

The beginning of the different-quality structure of the cerebral cortex was laid in 1674 by the Kyiv anatomist A.A. Betsom. Later K. Brodman in 1903-09. identified 52 cytoarchitectonic fields. O. Vogt and C. Vogt identified 150 myeloarchitectonic fields in the cortex.

Basal ganglia of the hemispheres.

These include: striatum, fence And amygdala.

Striatum ( striopallidal system) consists of 2 nuclei - caudate and lentiform, separated by a layer of white matter - the internal capsule. The caudate nucleus is located near the thalamus. It has a horseshoe shape and consists of a head, body and tail. The lenticular nucleus has the shape of a lentil grain and is located lateral to the thalamus and caudate nucleus. The lenticular nucleus is divided into 3 parts thanks to the white matter. The putamen lies most laterally and is dark in color, and the two lighter parts are called the lateral and medial globus pallidus.

The shell is characterized by participation in the organization of feeding behavior: food search, food orientation, food capture and food possession. Irritation of the shell leads to changes in breathing and salivation.

Connections between the globus pallidus and the thalamus, putamen, caudate nucleus, midbrain, hypothalamus, somatosensory system, etc. indicate its participation in the organization of simple and complex forms of behavior.

Stimulation of the globus pallidus, unlike stimulation of the caudate nucleus, does not cause inhibition, but provokes an orienting reaction, movements of the limbs, feeding behavior (sniffing, chewing, swallowing, etc.).

The striatum controls the processes of thermoregulation and carbohydrate metabolism. To the outside of the lenticular nucleus there is a thin plate of gray matter - the fence.

Amygdala nucleus(major commissure of the brain) is located in anterior section temporal lobe, part of the limbic system.

Thus, the basal ganglia of the brain are integrative centers for the organization of motor skills, emotions, higher nervous activity, and each of these functions can be enhanced or inhibited by the activation of individual formations of the basal ganglia.

Lateral ventricles.

Lateral ventricle– the cavity of the hemispheres (I and II ventricles) and communicating through the interventricular foramen with the III ventricle. In each ventricle there is a central part and three horns: anterior (frontal) - in the frontal lobe; posterior (occipital) – in occipital lobe and lower (temporal) - in the temporal lobe. The lateral ventricles, like other ventricles of the brain, and the central canal of the spinal cord are lined from the inside with a layer of ependymocytes. Ependymal cells form cerebrospinal fluid and regulate its composition.

CRANIAL NERVES

All cranial nerves arise from the base of the brain, with the exception of one (IV pair), which exits the brain from its dorsal side (below the roof of the midbrain). Each nerve is assigned a pair number and name. The numbering order reflects the sequence of exit of the nerves: I - olfactory nerve, II - optic nerve, III - oculomotor nerve, IV - trochlear nerve, V - trigeminal nerve, VI - abducens nerve, VII - facial nerve, VIII - vestibulocochlear nerve, IX - glossopharyngeal nerve, X - vagus nerve, XI - accessory nerve, XII - hypoglossal nerve.

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

Unlike spinal nerves, which are mixed, cranial nerves are divided into sensory (I, II, VIII), motor (III, IV, VI, XI, XII) and mixed (V, VII, IX, X). Some nerves (III, VII, IX, X) contain parasympathetic fibers going to smooth muscles, blood vessels, and glands. Sensory nerves are considered along with their pathways along the path of excitation.

Localization of functions in the cerebral cortex.

I.P. Pavlov considered the cerebral cortex as a continuous perceptual surface, as a set of cortical ends of analyzers. I.P. Pavlov showed that the cortex distinguishes between nuclei and scattered elements. The nucleus is the place where neurons are concentrated, where all peripheral receptor structures are projected and where important analysis and synthesis and integration of functions.

Scattered elements can be located along the periphery of the nucleus and at different distances from it. They provide simpler analysis and synthesis.

Let's consider some localization of the nuclei of motor analyzers:

1. In the cortex of the postcentral gyrus (fields 1, 2, 3) and the superior parietal lobule (fields 5 and 7) lie nerve cells that form the core of the cortical analyzer of the general sensitivity(temperature, pain, tactile and proprioceptive).

2. Core motor The analyzer is located mainly in the so-called motor area of ​​the cortex, which includes the precentral gyrus (fields 4 and 6) and the paracentral lobule on the medial surface of the hemisphere. In the upper parts of the precentral gyrus and in the paracentral lobule there are cells, impulses from which are sent to the muscles of the lowermost parts of the trunk and lower extremities. In the lower part of the precentral gyrus there are motor centers that regulate the activity of the facial muscles.

3. Core visual The analyzer is located in the occipital lobe of the cerebral hemisphere (fields 17, 18, 19). The nucleus of the visual analyzer of the right hemisphere is connected by pathways to the lateral half of the retina of the right eye and the medial half of the retina of the left eye. Thus, only bilateral damage to the nuclei of the visual analyzer leads to complete cortical blindness.

4. In depth lateral sulcus on the surface of the middle part of the superior temporal gyrus facing the insula there is a nucleus auditory analyzer (fields 41, 42, 52). To the nerve cells that make up the core of the auditory analyzer of each hemisphere, conductive paths pass from receptors of both the left and right side. In this regard, unilateral damage to this nucleus does not cause a complete loss of the ability to perceive sounds. Bilateral lesions are accompanied by cortical deafness, as in the case of complete cortical blindness.

5. Motor analyzer core speech articulation(speech motor analyzer, Broca's center) is located in the posterior parts of the inferior frontal gyrus (field 44). It is adjacent to the motor cortex. This is the motor center of speech, which controls the muscles of the tongue, jaws and pharynx, due to which sounds are pronounced. If this center is damaged, aphasia occurs and motor acts become difficult. After strokes, this center is paralyzed, while understanding speech, reading and writing are not impaired, and the patient is aware of his defect.

6. Core auditory analyzer of oral speech ( Wernicke's center) is closely interconnected with the cortical center of the auditory analyzer and is located in the superoposterior part of the left temporal lobe. This is the sensory center of speech, which is responsible for understanding speech and comprehending it. When it is damaged, Wernicke's aphasia occurs, when understanding speech is very difficult, speech is fluent, meaningless, reading and writing are impaired, and the patient does not realize the meaninglessness of his speech.

7. In direct connection with the core of the visual analyzer there is a core visual analyzer of written speech(field 39), located in the angular gyrus of the inferior parietal lobule. Damage to this nucleus leads to loss of the ability to perceive written text and read.

The medulla oblongata - part of the brain stem - got its name due to the features anatomical structure(Fig. 15). It is located in the posterior cranial fossa, bordered above by the pons; downwards without a clear boundary it passes into the spinal cord through the foramen magnum. The posterior surface of the medulla oblongata together with the pons constitutes the bottom of the fourth ventricle. The length of the medulla oblongata of an adult is 8 cm, diameter is up to 1.5 cm.

The medulla oblongata consists of the nuclei of the cranial nerves, as well as the descending and ascending conduction systems. Important education medulla oblongata - reticular substance, or reticular formation. The nuclear formations of the medulla oblongata are: 1) olives, related to the extrapyramidal system (they are connected to the cerebellum); 2) Gaulle and Burdach nuclei, in which the second proprioceptive neurons are located;

Rice. 15.

(a) and a diagram of the rhomboid fossa with the location of the cranial nerve nuclei in it (b): 1 - cerebral peduncles; 2 - brain bridge; 3 - medulla oblongata; 4 - cerebellum (articular-muscular) sensitivity; 3) nuclei of the cranial nerves: hypoglossal (XII pair), accessory (XI pair), vagus (X pair), glossopharyngeal (IX pair), the descending part of one of the sensory nuclei of the trigeminal nerve (its head part is located in the bridge).

The medulla oblongata contains conducting pathways: descending and ascending, connecting the medulla oblongata with the spinal cord, the upper part of the brain stem, the striopallidal system, the cerebral cortex, the reticular formation, and the limbic system.

The pathways of the medulla oblongata are a continuation of the spinal cord pathways. In front there are pyramidal pathways forming a cross. Most of the fibers of the pyramidal tract cross and pass into the lateral column of the spinal cord. The smaller, uncrossed part passes into the anterior column of the spinal cord. The final station of motor voluntary impulses traveling along the pyramidal tract are the cells of the anterior horns of the spinal cord. In the middle part of the medulla oblongata there are proprioceptive sensory pathways from the Gaulle and Burdach nuclei; these paths go to the opposite side. Fibers of superficial sensitivity (temperature, pain) pass outward from them.

Along with the sensory pathways and the pyramidal pathway, the descending efferent pathways of the extrapyramidal system pass through the medulla oblongata.

At the level of the medulla oblongata, the ascending pathways to the cerebellum pass through the inferior cerebellar peduncle. Among them, the main place is occupied by the spinocerebellar, olivo-cerebellar tracts, collateral fibers from the Gaulle and Burdach nuclei to the cerebellum, fibers from the nuclei of the reticular formation to the cerebellum (reticular-cerebellar tract). There are two spinocerebellar tracts. One goes to the cerebellum through the inferior peduncles, the second through the superior peduncles.

The following centers are located in the medulla oblongata: regulating cardiac activity, respiratory and vasomotor, inhibiting the activity of the heart (vagus nerve system), stimulating lacrimation, secretion of the salivary, pancreas and gastric glands, causing the secretion of bile and contraction of the gastrointestinal tract, i.e. . centers that regulate the activity of the digestive organs. The vasomotor center is in a state of increased tone.

Being part of the brain stem, the medulla oblongata takes part in the implementation of simple and complex reflex acts. The reticular formation of the brain stem, the system of nuclei of the medulla oblongata (vagus, glossopharyngeal, vestibular, trigeminal), descending and ascending conduction systems of the medulla oblongata are also involved in the performance of these acts.

The medulla oblongata plays an important role in the regulation of respiration and cardiovascular activity, which are excited by both neuro-reflex impulses and chemical stimuli acting on these centers.

The respiratory center regulates the rhythm and frequency of breathing. Through the peripheral, spinal respiratory center, it sends impulses directly to the respiratory muscles chest and to the diaphragm. In turn, centripetal impulses entering the respiratory center from the respiratory muscles, receptors of the lungs and respiratory tract support its rhythmic activity, as well as the activity of the reticular formation. The respiratory center is closely interconnected with the cardiovascular center. This connection is illustrated by the rhythmic slowdown of cardiac activity at the end of exhalation, before the start of inhalation - the phenomenon of physiological respiratory arrhythmia.

At the level of the medulla oblongata there is a vasomotor center, which regulates the constriction and dilation of blood vessels. The vasomotor and inhibitory centers of the heart are interconnected with the reticular formation.

The nuclei of the medulla oblongata take part in providing complex reflex acts (sucking, chewing, swallowing, vomiting, sneezing, blinking), thanks to which orientation in the surrounding world and the survival of the individual are carried out. Due to the importance of these functions, the systems of the vagus, glossopharyngeal, hypoglossal and trigeminal nerves develop at the earliest stages of ontogenesis. Even with anencephaly ( we're talking about about children who are born without the cerebral cortex) the acts of sucking, chewing, and swallowing are preserved. The preservation of these acts ensures the survival of these children.

Medulla. The medulla oblongata is a direct continuation of the spinal cord. Its lower border is at the level of the foramen magnum. At the top, the medulla oblongata borders the hindbrain - the lower edge of the pons.

The length of the medulla oblongata is about 25 mm . In shape it resembles a truncated cone. The anterior surface of the medulla oblongata is divided anterior median fissure. On the sides of this gap there are longitudinal elevations - pyramids, formed by bundles of nerve fibers of descending pathways. On each side of the pyramids, they come out of the brain hypoglossal nerve roots(XII pairs of cranial nerves).

The posterior surface of the medulla oblongata is divided posterior median sulcus. On the sides of it there are suitable posterior cords of the spinal cord. On the sides of the posterior cords they exit from the brain roots of the glossopharyngeal, vagus And accessory nerves (IX, X, XI pairs of cranial nerves). The cavity of the medulla oblongata (common with the hindbrain) is the IV ventricle.

Internal structure. The medulla oblongata consists of gray And white matter bases and tires. The white matter of the base of the medulla oblongata consists of long nerve fibers, descending pathways. Descending pathways go from the cerebral cortex and brainstem nuclei to the motor nerve cells of the spinal cord. The white matter of the tegmentum of the medulla oblongata consists of ascending and descending pathways. The ascending pathways are a continuation of the spinal cord pathways leading to the nuclei (gray matter) of the brain.

The gray matter of the tegmentum of the medulla oblongata consists of separate groups of nerve cells located within the white matter. This cranial nerve nuclei from IX to XII pairs and clusters of neurons of the reticular formation. Reticular formation(reticular substance) is formed by individual nerve cells and their small clusters (nuclei), connected to each other by numerous processes (nerve fibers).

Functional significance of the medulla oblongata. Nuclei of the medulla oblongata provide sensory, motor and autonomic innervation to many organs of the head, neck, chest and abdomen. Thus, the axons of the motor nerve cells of the hypoglossal nerve, forming hypoglossal nerve, innervate all the muscles of the tongue. Nerve fibers accessory nerve(XI pair) are directed to some muscles of the neck. Vagus nerve(X pair) innervates the organs of the thoracic and abdominal cavities of the body (heart, lungs, digestive system organs, etc.). I glossopharyngeal nerve(IX pair), together with the vagus, innervates the muscles of the pharynx, and the sensory fibers of these nerves - the mucous membrane of the tongue, pharynx, and larynx.

Cells and cell clusters reticular formation participate in the formation of ascending and descending pathways, influence the nerve impulses passing through them (strengthen them or weaken them). The nuclei of the reticular formation regulate the rhythmic contractions of the diaphragm (inhalation - exhalation) - the respiratory center, the level of blood pressure in the vessels (vasomotor center).

Brain pons (Varoliev pons)

The pons is located in front of the medulla oblongata in the form of a thickened ridge. The transverse fibers of the bridge form right And left middle legs cerebellum, which connect the pons to the cerebellum. The posterior surface of the bridge, covered by the cerebellum, participates together with the medulla oblongata in the formation of the bottom of the fourth ventricle - the so-called rhomboid fossa. Cranial nerves emerge from the pons (pairs V to VII): these are trigeminal nerve(V), abducens nerve(VI), facial nerve (VII) and vestibulocochlear nerve (VIII).

Internal structure. The white matter of the bridge is formed by ascending and descending pathways. The white matter of the pons contains conductive pathways for hearing and balance, as well as sensory pathways that conduct nerve impulses from the skin of the face and other organs of the head. The gray matter of the pons consists of the motor, sensory and autonomic nuclei of the cranial nerves and neurons of the reticular formation, which continues into the pons from the medulla oblongata.

Functional significance of the bridge. Sensitive, motor and autonomic innervation of the head organs, including some sensory organs, is carried out from the pons nuclei. So, trigeminal nerve(V pair) innervates the masticatory muscles with motor fibers, and its sensory fibers, forming three branches, conduct sensitive impulses from the skin of the face and other organs of the head to the bridge. Abducens nerve(VI pair) carries motor impulses to one of the oculomotor muscles (abducens). Axons of motor nucleus nerve cells facial nerve(VII pair) innervate the facial muscles, and its sensory fibers conduct taste sensitivity from the tongue receptors into the bridge. To the cores vestibulocochlear nerve Nerve impulses come from the organs of hearing and balance (inner ear).

Cerebellum. The cerebellum (small brain) is located posterior to the pons of the medulla oblongata. It consists of a middle unpaired part - worm and paired right and left hemispheres. The surface of the hemispheres and the worm is separated by numerous transverse grooves, between which there are narrow stripes - leaves of the cerebellum. Pathways connect the cerebellum with other parts of the central nervous system. They form three pairs of cerebellar peduncles - inferior, superior And average. The lower ones connect the cerebellum with the medulla oblongata, the upper ones with the midbrain, the middle ones with the pons.

Internal structure. The cerebellum is divided into gray and white matter. Gray matter is located superficially and forms cerebellar cortex thickness 1 – 2.5 mm. Nerve cells in the cortex form three layers. The outer molecular and inner granular layers consist of small nerve cells. The middle layer is formed by large pear-shaped cells. The white matter of the cerebellum is represented by nerve fibers and lies under the cortex. In the thickness of the white matter there are groups of neurons that form paired cerebellar nuclei. The shoots of one of the largest of them (dentate nucleus) are part of the superior cerebellar peduncle. Other kernels (cork-shaped, spherical and the so-called tent cores) lie between the dentate nuclei.

Functional significance of the cerebellum. The cerebellum influences various motor functions. It provides accuracy, dexterity and coordination of movements. The cerebellum takes part in the regulation of autonomic functions and affects the cardiovascular, respiratory and digestive systems.

Below the cerebellum is the IV ventricle, which is the cavity of the hindbrain and medulla oblongata. Below, the central canal of the spinal cord opens into the IV ventricle, and at the top, the IV ventricle passes into a narrow canal - brain aqueduct, which is the cavity of the midbrain. The bottom of the IV ventricle, formed by the posterior surface of the medulla oblongata and the pons, has the shape of a rhombus, which is why it is called diamond-shaped fossa. The roof of the IV ventricle has the shape of a tent, which is formed by a thin plate of the medulla (superior cerebellar peduncles, superior and inferior medullary velum). Bottom part the tent on the side of the IV ventricle is covered choroid plexus, whose cells produce cerebrospinal fluid.

Midbrain. The midbrain is located between the pons below and the diencephalon above. The midbrain includes the cerebral peduncles and the roof of the midbrain. The midbrain has a cavity, the so-called cerebral aqueduct - a narrow canal that connects the third and fourth ventricles of the brain.

The roof of the midbrain, or the quadrigeminal plate, is divided by transverse and longitudinal grooves into two superior and two inferior colliculi. The nuclei formed by the nerve cells of the superior colliculus are subcortical centers of vision, and the lower hillocks - subcortical hearing centers.

The cerebral peduncles are white round cords emerging from the pons and heading forward and upward to the diencephalon and the cerebral hemispheres. The third and fourth pairs of cranial nerves depart from the midbrain - oculomotor And trochlear nerves.

Each cerebral peduncle consists of grounds And tires, which are separated by black substance

It is formed by nerve cells, the cytoplasm of which contains a lot of melanin pigment. The substantia nigra is involved in maintaining muscle tone of skeletal muscles, as well as in regulating the functions of the autonomic nervous system.

At the base of the cerebral peduncles there are descending pathways from the cells of the cerebral cortex to the motor neurons of the anterior horns of the spinal cord and to the motor nuclei of the cranial nerves located in the brain stem.

Midbrain tegmentum formed by ascending and descending pathways. The gray matter of the midbrain tegmentum consists of the nuclei of cranial nerves III and IV pairs (oculomotor And block). red kernels and cells reticular formation. The processes of the cells of the III and IV nuclei are directed to the muscles of the eyeball. The red nuclei regulate the tone of skeletal muscles and provide habitual, automatic movements of skeletal muscles.

The functions of the midbrain are also associated with the nuclei of its colliculi - the quadrigeminal plate. The nerve cells of these nuclei, in response to light and sound stimulation, send impulses through motor neurons to the muscles of the head and torso, which provide rapid movements. These reflexes contribute to the body's rapid response to unexpected, sudden irritations.

21.Diencephalon located above the midbrain, under the cerebral hemispheres. Its structures are mainly hidden by the telencephalon hemispheres. In the diencephalon there are distinguished: paired thalamus (visual thalamus), subthalamus, suprathalamus regions and hypothalamus (subtubercular region). The cavity of the diencephalon is the third ventricle.

The thalamus (visual thalamus) is a paired ovoid-shaped formation. Its lower surface merges with the subtubercular region, the outer lateral (lateral) borders the cerebral hemisphere, the inner lateral (medial) forms the lateral wall of the third ventricle.

The thalami consist of gray And white matter. Gray matter is formed by clusters of nerve cells - cores. The optic thalamus has about 40 nuclei. On the cells of some of them the nerve fibers of the ascending pathways end, along which impulses of all types of general sensitivity (pain, temperature, touch, pressure, etc.) rise, including sensitive signals from muscles and tendons. Axons of interneurons of the thalamic nuclei form direct connections with nerve cells of the central (projection) fields of the cerebral cortex. Thus, all sensitive nerve impulses, signals that enter the cerebral cortex, pass through the thalamus of the diencephalon. Therefore, when the thalamus is damaged, conscious perception of various types of sensitivity decreases or completely disappears.

Scattered cells and nuclei reticular formation(reticular formation), located in the diencephalon and in the deep (central) parts of the midbrain, pons and medulla oblongata, perform a conductor function and also activate the activity of the cerebral cortex. Nerve impulses passing through the cells of the reticular formation are strengthened or weakened; the reticular formation has an exciting or inhibitory effect on them. Impulses passing through the reticular formation to the cerebral cortex maintain the working tone of the cortex. In connection with these functions, the reticular formation is called the activating system.

The subcutaneous region of the diencephalon consists of two pairs of geniculate bodies. External(lateral) geniculate bodies are the subcortical center of vision, medial geniculate bodies - subcortical hearing center. In the external geniculate bodies, part of the fibers of the visual pathway ending in the brain from the retina of the eyes. The nerve cells of the medial geniculate bodies terminate in fibers that carry auditory sensitivity from the cells of the inner ear that perceive sound stimulation.

The axons of the nerve cells of the geniculate bodies are directed to the corresponding centers (visual, auditory) located in the cerebral cortex. In the white matter of the cerebral hemispheres, these fibers form the so-called visual and auditory radiation.

The supra-tuberculous region is relatively small. It is located above the back of the thalamus. The supra-tuberculous region is formed leashes. leash triangles And soldering leashes, which are associated with the endocrine gland - the pineal gland, which is involved in the regulation of processes that occur rhythmically (cyclically) in the body.

The hypothalamus (subthalamic region) is located in front of the cerebral peduncles. The subtubercular region includes a number of structures: optic chiasm, gray tubercle, infundibulum, mastoid bodies. Mastoid bodies have a spherical shape. Some of the fibers of the olfactory pathway end on the cells of the mastoid bodies. Anterior to the mastoid bodies lies gray bump. Tapering downwards, the gray hillock turns into funnel, penetrating into the pituitary fossa of the body of the sphenoid bone. The pituitary gland, the endocrine gland, seems to be suspended on the funnel. Anterior to the gray tubercle, the optic nerves form visual cross. The cavity of the diencephalon is III ventricle, having the appearance of a narrow gap, limited on the sides by the inner surface of the thalamus, and below by the upper part of the hypothalamus (subthalamus). The upper wall of the third ventricle is formed by the fornix of the brain, to which the choroid plexus of the third ventricle, which produces cerebrospinal fluid, is adjacent below. In its posterior part, the third ventricle communicates with the fourth ventricle through the narrow cavity of the midbrain - the cerebral aqueduct.

Internal structure of the hypothalamus. The gray matter of the hypothalamus is represented by clusters of nerve cells - nuclei, which are grouped in the anterior, middle and posterior parts of the hypothalamus. Among the nerve cells of the hypothalamus there are many secretory neurons, which combine the properties of nerve and endocrine cells, being neurosecretory cells. Secretory neurons of the anterior hypothalamus synthesize biologically active substances, which pass along axons to the posterior lobe of the pituitary gland. Small neurosecretory cells of the middle section of the subtubercular region produce substances that control the hormone-forming activity of the anterior pituitary gland (adenohypophysis). In this case, one part of the biologically active substances stimulates the release and production of hormones by the cells of the anterior pituitary gland, while the other inhibits their function. Thus, the hypothalamus is a link between the nervous and endocrine systems.

Cortex

The cerebral cortex is the newest formation in terms of its evolutionary development. The thickness of the cerebral cortex (CBC) is 1.3-4.5 mm. The cortex contains from 10 to 18 billion nerve cells. The surface area of ​​the KBP is 2200 cm2. The main cells of the PBC are pyramidal, stellate and spindle-shaped.

The main afferents enter the CBP via fibers of the thalamocortical pathway.

CBP is characterized by numerous interneuron connections, the number of which increases rapidly until the age of 18. The final maturation of the PBC ends at 22-23 years.

Based on the density and shape of neurons, Brodmann divided the CBP into 53 cytoaritectonic fields.

The morpho-functional unit of the KBP is vertical column, which performs a specific function. The vertical column is large pyramidal cells with neurons located above and below them, which form a functional association. All neurons of the column respond to stimulation of the same receptor with the same reaction and jointly form an efferent response. The spread of excitation from one column to a nearby one is limited by lateral inhibition

There are several areas in the cortex:

Motor area. When it is stimulated, various movements appear.

Sensory area. This area of ​​the cortex receives specific afferent impulses from receptors from the periphery.

Association zones. These areas of the cortex receive information from various receptor fields of the CBP.

The KBP identifies areas with less defined functions. Yes, a significant part frontal lobes, especially on the right side, can be removed without noticeable damage. However, if a bilateral removal of the frontal areas is performed, severe mental disorders occur.

The projection zones of the analyzers are located in the cortex. Based on their structure and functional significance, they were divided into 3 main groups of fields:

1.Primary fields(nuclear zones of analyzers).

2. Secondary fields

3. Tertiary fields.

Primary fields are associated with the senses and movement. They ripen early. I.P. Pavlov called them nuclear zones of analyzers. They carry out a primary analysis of individual stimuli that enter the cortex. If there is a violation of the primary fields, to which information comes from the organ of vision or hearing, then cortical blindness or deafness occurs.

Secondary fields are the peripheral zones of analyzers. They are located next to the primary ones and are connected to the senses through the primary fields. In these fields, generalization and further processing of information occurs. When secondary fields are damaged, a person sees, hears, but does not recognize or understand the meaning of the signals.

Tertiary fields are areas where analyzers overlap. They are located on the borders of the parietal, temporal and occipital regions, as well as in the anterior part of the frontal lobes. In the process of ontogenesis they mature later. These fields ensure coordinated work of both hemispheres. Here the highest analysis and synthesis take place, goals and objectives are developed. Tertiary fields have extensive connections.

The presence of structurally different fields in the KBP also implies their different functional meaning. The CBP is divided into sensory, motor and associative areas.

Sensory areas. Each hemisphere has two sensory zones:

Somatic(skin, muscle, joint sensitivity).

Visceral, impulses from internal organs arrive to this zone of the cortex.

The somatic zone is located in the area of ​​the postcentral gyrus. This zone receives information from the skin and motor system from specific nuclei of the thalamus. The cutaneous receptor system projects to the posterior central gyrus. A large surface area is occupied by receptors in the hands, facial muscles, and vocal apparatus, and much less on the thigh, lower leg, and torso, since fewer receptors are localized in these areas.

The second somatosensory zone is localized in the area of ​​the Sylvian fissure. In this zone, integration and critical evaluation of information from specific nuclei of the thalamus takes place. For example, the visual zone is localized in the occipital lobe in the area of ​​the calcarine sulcus. The auditory system projects to the temporal lobe (Heschl's gyrus).

All sensory and motor areas occupy less than 20% of the surface of the KBP. The rest of the crust is associative area. Each associative area of ​​the CPB is associated with several projection areas. The association areas of the cortex include parts of the parietal, frontal and temporal lobes. The boundaries of associative fields are unclear. Neurons of association areas are involved in the integration of various information. Here comes the highest analysis and synthesis of irritations. As a result, complex elements of consciousness are formed. The parietal cortex is involved in assessing the biological significance of information and spatial perception. The frontal lobes (fields 9-14), together with the limbic system, control motivational behavior and program behavioral acts. If parts of the frontal lobes are destroyed, memory impairment occurs.

EEG rhythms

Alpha - rhythm 8 -13 imp/sec,

amplitude 50 µV

Beta - rhythm 14-30 imp/sec,

amplitude 25 µV

Theta - rhythm 4-8 imp/sec

Delta - rhythm 0.5-3.5 pulse/sec

amplitude 100 – 300 µV

Electrical activity of the cortex

Changes in the functional state of the cortex are reflected in its biopotentials. Spontaneous electrical oscillations with a certain periodicity are called electroencephalography (EEG).

EEG is widely used in the clinic, as it allows one to assess the state of the cortex, obtain information about the depth of anesthesia, and the localization of the pathological process.

The following EEG rhythms are distinguished:

Alpha rhythm– frequency 8-13 per second, amplitude – 50 µV. This rhythm is recorded at rest, in the absence of external stimuli, when a person is in a comfortable position with his eyes closed.

Beta rhythm– frequency 14-30 per second, amplitude – 25 µV. This rhythm is recorded when a person enters an active state and indicates desynchronization of the cortex.

Theta rhythm– frequency 4-7 Hz, amplitude – 100-300 µV. Recorded during the transition from a state of rest to a state of concentration or sleep.

Delta rhythm– frequency 3-5 Hz, amplitude – 100-300 µV.

Recorded during deep sleep, during loss of consciousness, during anesthesia. In awake people, the delta rhythm is not recorded, but it is characteristic of the hippocampus even in an active state

Interhemispheric brain asymmetry

Left hemisphere

Verbal, forms temporary relationships, carries out analysis, sequence of perceptions, abstract perception

Right hemisphere

Non-verbal, forms spatial relationships, carries out synthesis, simultaneous and specific perception

Functional asymmetry of the brain.

There are 3 types of asymmetry:

Motor– unequal motor activity of the muscles of the right and left halves of the body.

Sensory– unequal perception of information by the right and left hemispheres.

Mental. People who are dominant left hemisphere They are prone to theories, have a large vocabulary, talk a lot, are mobile, purposeful and able to make forecasts.

People who are dominant right hemisphere, prefer specific types activity, slow, speak little, very sentimental, prone to memories.

Recently, the concept of the complementary influence of both hemispheres of the CBP has been adopted. This means that the advantage of one hemisphere can be expressed only in one type of activity.

Asymmetry

Motor – uneven motor activity of the muscles of the arms, legs, and face.

Sensory – unequal perception of objects on the left and right by each hemisphere

Mental: “left-hemisphere person”, “right-hemisphere person”.

The medulla oblongata and the pons perform two functions - reflex and conductive. Through the sensitive fibers of the roots of the cranial nerves, it receives impulses - information from the receptors of the scalp, mucous membranes of the eyes, nose, mouth (including taste buds), from the organ of hearing, the vestibular apparatus (organ of balance), from the receptors of the larynx, trachea, lungs, as well as from interoreceptors of the cardiovascular system and digestive apparatus.

Through the medulla oblongata, many simple and complex reflexes are carried out, covering not individual metameres of the body, but organ systems, for example, the digestive, respiratory, and circulatory systems. The reflex activity of the medulla oblongata can be observed in a bulbar cat, that is, a cat in which the brain stem above the medulla oblongata has been cut. The reflex activity of such a cat is complex and diverse.

The following reflexes occur through the medulla oblongata: 1) protective: coughing, sneezing, blinking, lacrimation, vomiting; 2) food: sucking, swallowing, secretion of juice from the digestive glands; 3) cardiovascular, regulating the activity of the heart and blood vessels; 4) in the medulla oblongata there is an automatically working respiratory center that provides ventilation to the lungs; 5) the vestibular nuclei are located in the medulla oblongata and the pons.

From the vestibular nuclei of the medulla oblongata begins the descending vestibulospinal tract, which is involved in the implementation of posture reflexes, namely in the redistribution of muscle tone. A bulbar cat can neither stand nor walk, but the medulla oblongata and cervical segments of the spinal cord provide those complex reflexes that are elements of standing and walking. All reflexes associated with the standing function are called positioning reflexes. Thanks to them, the animal holds its body, usually with the crown up.

The special importance of this part of the central nervous system is determined by the fact that the medulla oblongata contains vital centers: respiratory, cardiovascular. Therefore, not only removal, but even damage to the medulla oblongata ends in death.

In addition to the reflex function, the medulla oblongata performs a conductive function. Conducting pathways pass through it, connecting the cortex, diencephalon, midbrain, cerebellum and spinal cord with a two-way connection.

The cerebellum is located dorsal to the pons and medulla oblongata. It has two hemispheres and a middle part - the worm. The surface of the cerebellum is covered with a layer of gray matter (cerebellar cortex) and forms narrow convolutions separated by grooves. With their help, the surface of the cerebellum is divided into lobules. The central part of the cerebellum consists of white matter, which contains accumulations of gray matter - the cerebellar nuclei. The largest of them is the dentate nucleus. The cerebellum is connected to the brain stem by three pairs of peduncles: the upper ones connect it to the midbrain, the middle ones to the pons, and the lower ones to the medulla oblongata. The peduncles contain bundles of fibers connecting the cerebellum to various parts of the brain and spinal cord.

During development, the isthmus of the rhombencephalon forms the boundary between the hindbrain and midbrain. From it develop the superior cerebellar peduncles, the superior medullary velum located between them and the triangles of the loop, lying outward from the superior cerebellar peduncles.

During development, the fourth (IV) ventricle (ventriculus quartus) is a common cavity of the medulla oblongata and hindbrain. At the bottom, the IV ventricle communicates with the central canal of the spinal cord, at the top it passes into the cerebral aqueduct of the midbrain, and in the roof area it is connected by three openings to the subarachnoid space of the brain. Its anterior (ventral) wall - the bottom of the IV ventricle - is called the rhomboid fossa. The lower part of the rhomboid fossa is formed by the medulla oblongata, and the upper part by the pons and isthmus. The posterior (dorsal) wall - the roof of the IV ventricle - is formed by the superior and inferior medullary sails and is supplemented from behind by a plate of the pia mater lined with ependyma. This area contains a large number of blood vessels that form the choroid plexus of the fourth ventricle. The convergence of the superior and inferior sails protrudes into the cerebellum and forms a tent. The rhomboid fossa has a vital important, since most of the nuclei of the cranial nerves (V - XII pairs) are located in this area.

Physiology of the cerebellum

The cerebellum is a suprasegmental part of the central nervous system that does not have a direct connection with the receptors and effectors of the body. It is connected in numerous ways to all parts of the central nervous system. Afferent pathways are sent to it, carrying impulses from proprioceptors of muscles, tendons, vestibular nuclei of the medulla oblongata, subcortical nuclei and cerebral cortex. In turn, the cerebellum sends impulses to all parts of the central nervous system.

The functions of the cerebellum are studied by irritating it, partially or completely removing it, and studying bioelectrical phenomena. The Italian physiologist Luciani characterized the consequences of removal of the cerebellum and loss of its functions with the famous triad A: astasia, atony and asthenia. Subsequent researchers added another symptom - ataxia.

A dog without a cerebellum stands on widely spaced legs and makes continuous rocking movements (astasia). She has impaired proper distribution of flexor and extensor muscle tone (atonia). Movements are poorly coordinated, sweeping, disproportionate, abrupt. When walking, the paws are thrown beyond the midline (ataxia), which is not observed in normal animals. Ataxia is explained by the fact that movement control is impaired. Analysis of signals from proprioceptors of muscles and tendons is missing. The dog cannot get its muzzle into the food bowl. Tilt of the head downwards or to the side causes a strong opposite movement.

The movements are very tiring: the animal, after walking a few steps, lies down and rests. This symptom is called asthenia.

Over time, movement disorders in a cerebellar dog smooth out. She eats on her own and her gait is almost normal. Only biased observation reveals some violations (compensation phase).

As E. A. Asratyan showed, compensation of functions occurs due to the cerebral cortex. If the bark of such a dog is removed, then all the violations are revealed again and are never compensated.

The cerebellum is involved in the regulation of movements, making them smooth, precise, proportionate. According to the figurative expression of L. A. Orbeli, the cerebellum is an assistant to the cerebral cortex in controlling skeletal muscles and the activity of autonomic organs. As studies by L.A. Orbeli have shown, cerebellar dogs have impaired autonomic functions. Blood constants, vascular tone, the functioning of the digestive tract and other autonomic functions become very unstable and easily shift under the influence of certain reasons (food intake, muscle work, temperature changes, etc.).

When half of the cerebellum is removed, motor functions on the side of the operation are impaired. This is explained by the fact that the cerebellar pathways either do not cross at all or cross twice.

Midbrain

The midbrain includes the cerebral peduncles, located ventrally, and the roof plate (lamina tecti), or quadrigemina, lying dorsally. The cavity of the midbrain is the cerebral aqueduct. The roof plate consists of two superior and two inferior colliculi, which contain the nuclei of gray matter. The superior colliculi are associated with the visual pathway, the inferior colliculi with the auditory pathway. From them originates the motor pathway that goes to the cells of the anterior horns of the spinal cord. On a cross section of the midbrain, three of its sections are clearly visible: the roof, the tegmentum and the base of the cerebral peduncle (Fig. 114). Between the tire and the base is a black substance. The tegmentum contains two large nuclei - the red nuclei and the nuclei of the reticular formation. The cerebral aqueduct is surrounded by central gray matter, which contains the nuclei of the III and IV pairs of cranial nerves. The base of the cerebral peduncles is formed by fibers of the pyramidal tracts and tracts connecting the cerebral cortex with the nuclei of the bridge and the cerebellum. The tegmentum contains systems of ascending pathways that form a bundle called the medial (sensitive) loop. The fibers of the medial lemniscus begin in the medulla oblongata from the cells of the nuclei of the thin and cuneate fasciculi and end in the nuclei of the thalamus. The lateral (auditory) loop consists of fibers of the auditory tract running from the pons to the inferior colliculi of the pontine tegmentum (quadrigeminal) and the medial geniculate bodies of the diencephalon.

Rice. 114. Cross section of the midbrain (diagram). 1 - cerebral peduncle; 2 - black substance; 3 - roof plate; 4 - red core; 5 - nucleus of the oculomotor nerve; 6 - oculomotor nerve; 7 - cerebral aqueduct

Physiology of the midbrain

The midbrain plays an important role in regulating muscle tone and implementing the righting and righting reflexes, which make standing and walking possible.

The role of the midbrain in the regulation of muscle tone is best observed in a cat in which a transverse incision is made between the medulla oblongata and the midbrain. Such a cat has a sharp increase in muscle tone, especially extensor muscles. The head is thrown back, the paws are sharply straightened. The muscles are so strongly contracted that an attempt to bend the limb ends in failure - it immediately straightens. An animal placed on outstretched paws like sticks can stand. This condition is called decerebrate rigidity. If the incision is made above the midbrain, then decerebrate rigidity does not occur. After about 2 hours, such a cat makes an effort to get up. First she raises her head, then her body, then stands on her paws and can begin to walk. Consequently, the nervous apparatus for regulating muscle tone and the functions of standing and walking are located in the midbrain.

The phenomena of decerebrate rigidity are explained by the fact that the red nuclei and reticular formation are separated from the medulla oblongata and spinal cord by transection. The red nuclei do not have a direct connection with receptors and effectors, but they are connected with all parts of the central nervous system. They are approached by nerve fibers from the cerebellum, basal ganglia, and cerebral cortex. The descending rubrospinal tract begins from the red nuclei, through which impulses are transmitted to the motor neurons of the spinal cord. It is called the extrapyramidal tract

The sensitive nuclei of the midbrain perform a number of important reflex functions. The nuclei located in the superior colliculi are the primary visual centers. They receive impulses from the retina and participate in the orientation reflex, i.e. turning the head towards the light. At the same time, the width of the pupil and the curvature of the lens (accommodation) change, which contributes to clear vision of the object.

The nuclei of the inferior colliculi are the primary auditory centers. They participate in the orienting reflex to sound - turning the head towards the sound. Sudden sound and light stimulation cause a complex alarm reaction (start reflex), mobilizing the animal for a quick response.

Diencephalon

The diencephalon is located under the corpus callosum and fornix, fused on the sides with the cerebral hemispheres. It includes the thalamus (visual thalamus), epithalamus (supra-tubercular region), metathalamus (sub-tubercular region) and hypothalamus (sub-tubercular region). The cavity of the diencephalon is the third ventricle.

The thalamus is a paired, ovoid collection of gray matter covered by a layer of white matter. The anterior sections are adjacent to the interventricular foramina, the posterior sections are expanded - to the quadrigeminal. The lateral surfaces of the thalamus grow together with the hemispheres and border the caudate nucleus and the internal capsule. The medial surfaces form the walls of the third ventricle, the lower ones continue into the hypothalamus. In the thalamus, there are three main groups of nuclei: anterior, lateral and medial, and there are 40 nuclei in total. In the epithalamus lies the upper appendage of the brain - the pineal gland, or pineal body, suspended on two leashes in the recess between the upper colliculi of the roof plate. The metathalamus is represented by the medial and lateral geniculate bodies, connected by bundles of fibers (handles of the colliculi) with the superior (lateral) and inferior (medial) colliculi of the roof plate. They contain nuclei that are reflex centers of vision and hearing.

The hypothalamus is located ventral to the thalamus and includes the subcutaneous region itself and a number of formations located at the base of the brain. These include: the terminal plate, the optic chiasm, the gray tubercle, the infundibulum with the lower appendage of the brain extending from it - the pituitary gland and the mastoid bodies. In the hypothalamic region there are nuclei (supravisceral, periventricular, etc.) containing large nerve cells capable of secreting a secretion (neurosecretion) that flows along their axons into the posterior lobe of the pituitary gland and then into the blood. In the posterior part of the hypothalamus lie nuclei formed by small nerve cells, which are connected to the anterior lobe of the pituitary gland by a special system of blood vessels.

The third (III) ventricle is located in the midline and is a narrow vertical slit. Its side walls are formed medial surfaces thalamus and subtubercular region, anterior - by the columns of the fornix and the anterior commissure, lower - by the formations of the hypothalamus and posterior - by the cerebral peduncles and supracuberous region. The upper wall - the lid of the third ventricle - is the thinnest and consists of the soft membrane of the brain, lined on the side of the ventricular cavity with an epithelial plate (ependyma). The soft shell has a large number of blood vessels here, forming the choroid plexus. In front, the third ventricle communicates with the lateral ventricles (I - II) through the interventricular foramina, and behind it passes into the cerebral aqueduct.