1. Basic principles of the functioning of the central nervous system. Structure, functions, methods of studying the CNS

Criteria for determining, methods and principles of studying the health of the child population The health of the child population is made up of the health of individuals, but is also considered as a characteristic of public health. Public health is not only

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Methods for directly studying the functions of the central nervous system are divided into morphological and functional.

Morphological methods- macroanatomical and microscopic studies of the structure of the brain. This principle underlies the method of genetic mapping of the brain, which makes it possible to identify the functions of genes in the metabolism of neurons. Morphological methods also include the method of labeled atoms. Its essence lies in the fact that radioactive substances introduced into the body penetrate more intensively into those nerve cells of the brain that are most functionally active at the moment.

Function Methods: destruction and irritation of CNS structures, stereotaxic method, electrophysiological methods.

destruction method. The destruction of brain structures is a rather crude method of research, since extensive areas of brain tissue are damaged. In the clinic, for the diagnosis of brain damage of various origins (tumors, stroke, etc.) in humans, methods of computed X-ray tomography, echoencephalography, and nuclear magnetic resonance are used.

Irritation method structures of the brain allows you to establish the path of propagation of excitation from the site of irritation to the organ or tissue, the function of which changes in this case. Electric current is most often used as an irritating factor. In experiments on animals, the method of self-irritation of various parts of the brain is used: the animal gets the opportunity to send irritation to the brain, closing the electric current circuit and to stop the irritation, opening the circuit.

Stereotactic electrode insertion method.

Stereotaxic atlases, which have three coordinate values ​​for all brain structures, placed in the space of three mutually perpendicular planes - horizontal, sagittal and frontal. This method makes it possible not only to introduce electrodes into the brain with high accuracy for experimental and diagnostic purposes, but also to influence individual structures with ultrasound, laser or X-ray beams for therapeutic purposes, as well as to perform neurosurgical operations.

Electrophysiological methods CNS studies include analysis of both passive and active electrical properties of the brain.

Electroencephalography. The method of recording the total electrical activity of the brain is called electroencephalography, and the curve of changes in brain biopotentials is called an electroencephalogram (EEG). EEG is recorded using electrodes placed on the surface of the human head. Two methods of registration of biopotentials are used: bipolar and monopolar. With the bipolar method, the difference in electrical potentials between two closely spaced points on the surface of the head is recorded. With the monopolar method, the difference in electrical potentials is recorded between any point on the surface of the head and an indifferent point on the head, the self-potential of which is close to zero. These points are the earlobes, the tip of the nose, and the surface of the cheeks. The main indicators characterizing the EEG are the frequency and amplitude of fluctuations of biopotentials, as well as the phase and form of fluctuations. According to the frequency and amplitude of oscillations, several types of rhythms in the EEG are distinguished.

2. Gamma >35 Hz, emotional arousal, mental and physical activity, when irritated.

3. Beta 13-30 Hz, emotional arousal, mental and physical activity, when irritated.

4. Alpha 8-13 Hz state of mental and physical rest, with eyes closed.

5. Theta 4-8 Hz, sleep, moderate hypoxia, anesthesia.

6. Delta 0.5 - 3.5 deep sleep, anesthesia, hypoxia.

7. The main and most characteristic rhythm is the alpha rhythm. In a state of relative rest, the alpha rhythm is most pronounced in the occipital, occipital-temporal, and occipital-parietal areas of the brain. With a short-term action of stimuli, such as light or sound, a beta rhythm appears. Beta and gamma rhythms reflect the activated state of brain structures, theta rhythm is more often associated with the emotional state of the body. The delta rhythm indicates a decrease in the functional level of the cerebral cortex, associated, for example, with a state of light sleep or fatigue. The local appearance of a delta rhythm in any area of ​​the cerebral cortex indicates the presence of a pathological focus in it.

microelectrode method. Registration of electrical processes in individual nerve cells. Microelectrodes - glass or metal. Glass micropipettes are filled with an electrolyte solution, most often a concentrated solution of sodium or potassium chloride. There are two ways to register cellular electrical activity: intracellular and extracellular. At intracellular The location of the microelectrode registers the membrane potential, or resting potential of the neuron, postsynaptic potentials - excitatory and inhibitory, as well as the action potential. Extracellular microelectrode registers only the positive part of the action potential.

2. Electrical activity of the cerebral cortex, electroencephalography.

EEG IN THE FIRST QUESTION!

Functional significance of various structures of the CNS.

The main reflex centers of the nervous system.

Spinal cord.

The distribution of functions of the incoming and outgoing fibers of the spinal cord obeys a certain law: all sensory (afferent) fibers enter the spinal cord through its posterior roots, and motor and autonomic (efferent) fibers exit through the anterior roots. back roots formed by the fibers of one of the processes of afferent neurons, the bodies of which are located in the intervertebral ganglia, and the fibers of the other process are associated with the receptor. Front roots consist of processes of motor neurons of the anterior horns of the spinal cord and neurons of the lateral horns. The fibers of the former are sent to the skeletal muscles, and the fibers of the latter switch in the autonomic ganglia to other neurons and innervate the internal organs.

Spinal cord reflexes can be subdivided into motor, carried out by alpha motor neurons of the anterior horns, and vegetative, carried out by efferent cells of the lateral horns. Motor neurons of the spinal cord innervate all skeletal muscles (with the exception of the muscles of the face). The spinal cord carries out elementary motor reflexes - flexion and extension, arising from irritation of skin receptors or proprioreceptors of muscles and tendons, and also sends constant impulses to the muscles, maintaining their tension - muscle tone. Muscle tone occurs as a result of irritation of the proprioreceptors of muscles and tendons when they are stretched during human movement or when exposed to gravity. Impulses from proprioreceptors are sent to the motor neurons of the spinal cord, and impulses from motor neurons are sent to the muscles, maintaining their tone.

medulla oblongata and pons. The medulla oblongata and the pons are referred to as the hindbrain. It is part of the brain stem. The hindbrain carries out complex reflex activity and serves to connect the spinal cord with the overlying parts of the brain. In its median region, there are posterior sections of the reticular formation, which have nonspecific inhibitory effects on the spinal cord and brain.

Pass through the medulla oblongata ascending pathways from auditory and vestibular receptors. End in the medulla oblongata afferent nerves carrying information from skin receptors and muscle receptors.

, Midbrain. Through the midbrain, which is a continuation of the brain stem, there are ascending paths from the spinal cord and medulla oblongata to the thalamus, cerebral cortex and cerebellum.

Intermediate brain. The diencephalon, which is the anterior end of the brain stem, contains visual tubercles - thalamus and hypothalamus - hypothalamus.

thalamus represents the most important "station" on the way of afferent impulses to the cerebral cortex.

thalamus nuclei subdivided into specific and non-specific.

Subcortical nodes. Through subcortical nuclei different sections of the cerebral cortex can be connected to each other, which is of great importance in the formation of conditioned reflexes. Together with the diencephalon, the subcortical nuclei are involved in the implementation of complex unconditioned reflexes: defensive, food, etc.

Cerebellum. This - suprasegmental education, having no direct connection with the executive apparatus. The cerebellum is part of the extrapyramidal system. It consists of two hemispheres and a worm located between them. The outer surfaces of the hemispheres are covered with gray matter - cerebellar cortex, and accumulations of gray matter in white matter form cerebellar nuclei.

FUNCTIONS OF THE SPINAL CORD

The first function is reflex. The spinal cord carries out motor reflexes of skeletal muscles relatively independently
Thanks to reflexes from proprioreceptors in the spinal cord, motor and autonomic reflexes are coordinated. Through the spinal cord, reflexes are also carried out from internal organs to skeletal muscles, from internal organs to receptors and other organs of the skin, from an internal organ to another internal organ.

The second function is conductor. Centripetal impulses entering the spinal cord through the posterior roots are transmitted along short pathways to its other segments, and along long pathways to different parts of the brain.

The main long pathways are the following ascending and descending pathways.

Ascending pathways of the posterior pillars. 1. A gentle bundle (Goll), which conducts impulses to the diencephalon and cerebral hemispheres from skin receptors (touch, pressure), interoceptors and proprioceptors of the lower body and legs. 2. The wedge-shaped bundle (Burdakh), which conducts impulses to the diencephalon and cerebral hemispheres from the same receptors in the upper body and arms.

Ascending paths of side pillars. 3. Posterior spinal-cerebellar (Flexiga) and 4. Anterior spinal-cerebellar (Govers), conducting impulses from the same receptors to the cerebellum. 5. Spinal-thalamic, conducting impulses to the diencephalon from skin receptors - touch, pressure, pain and temperature, and from interoreceptors.

Descending pathways from the brain to the spinal cord.
1. Direct pyramidal, or anterior cortico-spinal bundle, from the neurons of the anterior central gyrus of the frontal lobes of the cerebral hemispheres to the neurons of the anterior horns of the spinal cord; crosses over in the spinal cord. 2. Crossed pyramidal, or cortico-spinal lateral bundle, from the neurons of the frontal lobes of the cerebral hemispheres to the neurons of the anterior horns of the spinal cord; crosses in the medulla oblongata. In these bundles, which reach the greatest development in humans, voluntary movements are carried out in which behavior is manifested. 3. The rubro-spinal bundle (Monakova) conducts centrifugal impulses to the spinal cord from the red nucleus of the midbrain, which regulate the tone of skeletal muscles. 4. The vestibulo-spinal bundle conducts from the vestibular apparatus to the spinal cord through the oblong and middle impulses, which redistribute the tone of the skeletal muscles

The formation of cerebrospinal fluid

In the subarachnoid (subarachnoid) space is cerebrospinal fluid, which in composition is a modified tissue fluid. This fluid acts as a shock absorber for brain tissue. It is also distributed along the entire length of the spinal canal and in the ventricles of the brain. Cerebrospinal fluid is secreted into the ventricles of the brain from the choroid plexuses, formed by numerous capillaries extending from the arterioles and hanging in the form of brushes into the cavity of the ventricle.

The surface of the plexus is covered with a single layer of cuboidal epithelium that develops from the neural tube ependyma. Beneath the epithelium lies a thin layer of connective tissue that arises from the pia mater and arachnoid.

Cerebrospinal fluid is also formed by blood vessels that penetrate the brain. The amount of this fluid is insignificant, it is released to the surface of the brain along the soft membrane that accompanies the vessels.

Midbrain.

The midbrain includes the legs of the brain, located ventrally, and the roof plate (lamina tecti), or quadrigemina, lying dorsally. The cavity of the midbrain is the aqueduct of the brain. The roof plate consists of two upper and two lower mounds, in which the nuclei of gray matter are laid. The superior colliculus is associated with the visual pathway, the inferior colliculus with the auditory pathway. From them originates the motor path going to the cells of the anterior horns of the spinal cord. On the transverse section of the midbrain, three of its sections are clearly visible: the roof, the tegmentum, and the base of the brain stem. Between the tire and the base is a black substance. There are two large nuclei in the tire - red nuclei and nuclei of the reticular formation. The aqueduct of the brain is surrounded by a central gray matter, which contains the nuclei of III and IV pairs of cranial nerves. The base of the legs of the brain is formed by the fibers of the pyramidal pathways and pathways connecting the cerebral cortex with the nuclei of the bridge and the cerebellum. In the tire, there are systems of ascending pathways that form a bundle called the medial (sensitive) loop. The fibers of the medial loop begin in the medulla oblongata from the cells of the nuclei of the thin and wedge-shaped bundles and end in the nuclei of the thalamus. The lateral (auditory) loop consists of fibers of the auditory pathway that extend from the pons to the inferior colliculi of the pontine tegmentum (quadrigemina) and the medial geniculate bodies of the diencephalon.

Physiology of the midbrain

The midbrain plays an important role in the regulation of muscle tone and the implementation of the installation and rectifying reflexes, due to which standing and walking are possible.

The role of the midbrain in the regulation of muscle tone is best observed in a cat that has had a transverse incision made between the medulla oblongata and the midbrain. In such a cat, muscle tone sharply increases, especially extensor. 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 legs stretched out 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 torso, then she gets up on her paws and can start walking. Consequently, the nervous apparatus for the regulation of muscle tone and the function of standing and walking are located in the midbrain.

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

The sensory nuclei of the midbrain perform a number of important reflex functions. The nuclei located in the superior colliculus are the primary visual centers. They receive impulses from the retina and participate in the orienting reflex, i.e. turning the head towards the light. This changes the width of the pupil and the curvature of the lens (accommodation), which contributes to a clear vision of the object. The nuclei of the inferior colliculus are the primary auditory centers. They are involved in the orienting reflex to sound - turning the head towards the sound. Sudden sound and light stimuli cause a complex alert reaction (start reflex), which mobilizes the animal for a quick response.

Cerebellum.

Physiology of the cerebellum

The cerebellum is above the segmental part of the CNS, which does not have a direct connection with the receptors and effectors of the body. In numerous ways, it is connected with all departments of the central nervous system. Afferent pathways are directed to it, carrying impulses from the proprioreceptors of muscles, tendons, vestibular nuclei of the medulla oblongata, subcortical nuclei and the cerebral cortex. In turn, the cerebellum sends impulses to all parts of the central nervous system.

The functions of the cerebellum are examined by stimulating it, partial or complete removal, and studying bioelectrical phenomena. The Italian physiologist Luciani characterized the consequences of the removal of the cerebellum and the loss of its functions by the famous triad A: astasia, atony and asthenia. Subsequent researchers added another symptom, ataxia.

Without a cerebellar dog stands on widely spaced paws, makes continuous rocking movements (astasia). She has impaired proper distribution of flexor and extensor muscle tone (atony). Movements are poorly coordinated, sweeping, disproportionate, abrupt. When walking, the legs are thrown behind the midline (ataxia), which is not observed in normal animals. Ataxia is due to the fact that the control of movements is disturbed. The analysis of signals from the proprioreceptors of muscles and tendons falls out. The dog cannot get his muzzle into a bowl of food. Tilt the head down or to the side causes a strong opposing 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 non-cerebellar dog smooth out. She eats on her own, her gait is almost normal. Only biased observation reveals some disturbances (compensation phase).

As shown by E.A. Asratyan, compensation of functions occurs due to the cerebral cortex. If the bark is removed from such a dog, then all violations are revealed again and will never be 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, vegetative functions are disturbed in non-cerebellar dogs. Blood constants, vascular tone, the work of the digestive tract and other vegetative functions become very unstable, easily shifted under the influence of various reasons (food intake, muscle work, temperature changes, etc.).

When half of the cerebellum is removed, the motor functions on the side of the operation are disturbed. This is due to; that the pathways of the cerebellum either do not cross at all, or cross 2 times.

Intermediate brain.

diencephalon

The diencephalon (diencephalon) is located under the corpus callosum and fornix, growing together on the sides with the cerebral hemispheres. It includes the thalamus (visual hillocks), epithalamus (above the hillock region), metathalamus (above the hillock "area") and the hypothalamus (under the hillock region). The cavity of the diencephalon is the third ventricle.

The thalamus is a pair of ovoid accumulations of gray matter, covered with a layer of white matter. The anterior sections are adjacent to the interventricular openings, the posterior ones are dilated - to the quadrigemina. The lateral surfaces of the thalamus fuse with the hemispheres and border on 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 the pineal body, suspended on two leashes in the recess between the upper mounds of the roof plate. The metathalamus is represented by medial and lateral geniculate bodies connected by bundles of fibers (handles of the hillocks) with the upper (lateral) and lower (medial) hillocks of the roof plate. They contain the nuclei, which are the reflex centers of vision and hearing.

The hypothalamus is located ventral to the thalamus and includes the subtuberous area itself and a number of formations located on the base of the brain. These include: the end plate, the optic chiasm, the gray tubercle, the funnel with the lower appendage of the brain extending from it - the pituitary gland and the mastoid bodies. In the hypothalamic region there are nuclei (supra-optic, periventricular, etc.) containing large nerve cells that can secrete a secret (neurosecrete) that enters their axons into the posterior lobe of the pituitary gland, and then into the blood. In the posterior hypothalamus lie nuclei formed by small nerve cells that are connected to the anterior pituitary by a special system of blood vessels.

The third (III) ventricle is located in the midline and is a narrow vertical gap. Its lateral walls are formed by the medial surfaces of the thalamus and under the tuberous region, the anterior - by the columns of the arch and the anterior commissure, the lower - by the formations of the hypothalamus and the posterior - by the legs of the brain and above the tuberous region. The upper wall - the cover of the third ventricle - is the thinnest and consists of a soft shell of the brain, lined from the side of the cavity of the ventricle with an epithelial plate (ependyma). The soft shell has here a large number of blood vessels that form the choroid plexus. From the front, the III ventricle communicates with the lateral ventricles (I-II) through the interventricular foramens, and from behind it passes into the aqueduct

Physiology of the diencephalon

The thalamus is a sensitive subcortical nucleus. It is called the "collector of sensitivity", since afferent paths from all receptors converge to it, excluding the olfactory ones. In the lateral nuclei of the thalamus there is a third neuron of the afferent pathways, the processes of which end in the sensitive areas of the cerebral cortex.

The main functions of the thalamus are the integration (unification) of all types of sensitivity, the comparison of information received through various communication channels, and the assessment of its biological significance. The nuclei of the thalamus are divided by function into specific (ascending afferent pathways end on the neurons of these nuclei), non-specific (nuclei of the reticular formation) and associative. Through the associative nuclei, the thalamus is connected with all the subcortical motor nuclei: the striatum, the globus pallidus, the hypothalamus - and with the nuclei of the midbrain and medulla oblongata.

The study of the functions of the thalamus is carried out by transections, irritation and destruction. The cat, in which the incision is made above the diencephalon, differs sharply from the cat in which the highest part of the CNS is the midbrain. She not only rises and walks, that is, performs complexly coordinated movements, but also shows all the signs of emotional reactions. A light touch causes a vicious reaction: the cat beats with its tail, bares its teeth, growls, bites, releases its claws. In humans, the thalamus plays a significant role in emotional behavior, characterized by peculiar facial expressions, gestures, and shifts in the functions of internal organs. With emotional reactions, blood pressure rises, the pulse and respiration become more frequent, the pupils dilate. The facial reaction of a person is innate. If you tickle the nose of the fetus for 5-6 months, you can see a typical grimace of displeasure (P.K. Anokhin). In animals, when the thalamus is stimulated, motor and pain reactions occur: squealing, grumbling. The effect can be explained by the fact that the impulses from the visual tubercles easily pass to the motor subcortical nuclei associated with them.

In the clinic, the symptoms of a thalamus lesion are severe headache, sleep disturbances, disturbances in sensitivity (increase or decrease), movements, their accuracy, proportionality, the occurrence of violent involuntary movements.

The hypothalamus is the highest subcortical center of the autonomic nervous system. In this area there are centers that regulate all vegetative functions, ensure the constancy of the internal environment of the body, as well as regulate fat, protein, carbohydrate and water-salt metabolism. In the activity of the autonomic nervous system, the hypothalamus plays the same important role that the red nuclei of the midbrain play in the regulation of the skeletal-motor functions of the somatic nervous system.

The earliest studies on the function of the hypothalamus are due to Claude Bernard. He found that an injection into the diencephalon of a rabbit caused an increase in body temperature of almost 3°C. This classic experiment, which made it possible to discover the thermoregulatory center in the hypothalamus, was called the heat prick. After the destruction of the hypothalamus, the animal becomes poikilothermic, i.e., loses the ability to maintain a constant body temperature.

Later it was found that almost all organs innervated by the autonomic nervous system can be activated by stimulation under the tuberous region. In other words, all the effects that can be obtained by stimulating the sympathetic and parasympathetic nerves are observed by stimulating the hypothalamus.

Currently, the method of electrode implantation is widely used to stimulate various brain structures. With the help of a special, so-called stereotactic technique, electrodes are inserted through a burr hole in the skull into any given area of ​​the brain. The electrodes are insulated throughout, only their tip is free. By including electrodes in the circuit, it is possible to irritate certain zones narrowly locally.

With irritation of the anterior parts of the hypothalamus, parasympathetic effects occur: increased bowel movements, separation of digestive juices, slowing down of heart contractions, etc .; when the posterior sections are irritated, sympathetic effects are observed: increased heart rate, vasoconstriction, increased body temperature, etc. Consequently, parasympathetic centers are located in the anterior sections of the hypothalamus, and sympathetic centers are located in the posterior sections.

Since stimulation with the help of implanted electrodes is carried out on the animal without anesthesia, it is possible to judge the behavior of the animal. In Andersen's experiments on a goat with implanted electrodes, a center was discovered, the irritation of which causes unquenchable thirst - the center of thirst. With his irritation, the goat could drink up to 10 liters of water. By stimulating other areas, it was possible to force a well-fed animal to eat (hunger center).

The experiments of the Spanish scientist Delgado on a bull were widely known. The bull was implanted with an electrode in the center of fear. When an angry bull rushed at the bullfighter in the arena, irritation was turned on and the bull retreated with clearly expressed signs of fear.

The American researcher D. Olds proposed to modify the method: to allow the animal itself to make contact (self-irritation method). He believed that the animal would avoid unpleasant stimuli and, on the contrary, strive to repeat pleasant ones. Experiments have shown that there are structures whose irritation causes an unbridled desire for repetition. The rats drove themselves to exhaustion by pressing the lever up to 14,000 times. In addition, structures were found, the irritation of which, apparently, causes an unpleasant sensation, since the rat avoids pressing the lever a second time and runs away from it. The first center is obviously the center of pleasure, the second is the center of displeasure.

Extremely important for understanding the functions of the hypothalamus was the discovery in this part of the brain of receptors that detect changes in blood temperature (thermoreceptors), osmotic pressure (osmoreceptors) and blood composition (glucoreceptors).

From the receptors "turned into the blood", there are reflexes aimed at maintaining the constancy of the internal environment of the body - homeostasis. "Hungry" blood, irritating glucoreceptors, excites the food center: there are food reactions aimed at finding and eating food.

One of the frequent manifestations of the disease of the hypothalamus is a violation of water-salt metabolism, manifested in the release of a large amount of urine of low density. The disease is called diabetes insipidus.

Under the hillock region is closely related to the activity of the pituitary gland. In large neurons of the supra-optic and paraventricular nuclei of the hypothalamus, the hormones vasopressin and oxytocin are formed. Hormones travel along the axons to the posterior pituitary gland, where they accumulate and then enter the bloodstream.

Another relationship between the hypothalamus and the anterior pituitary gland. The vessels surrounding the nuclei of the hypothalamus unite into a system of veins that reach the anterior lobe of the pituitary gland and here again break up into capillaries. With blood, releasing factors, or releasing factors that stimulate the formation of hormones in its anterior lobe, enter the pituitary gland.

17. Subcortical centers .

18. The cerebral cortex.

General organization plan bark. The cerebral cortex is the highest part of the central nervous system, which appears last in the process of phylogenetic development and is formed later than other parts of the brain in the course of individual (ontogenetic) development. The cortex is a layer of gray matter 2-3 mm thick, containing an average of about 14 billion (from 10 to 18 billion) nerve cells, nerve fibers and interstitial tissue (neuroglia). On its transverse section, according to the location of neurons and their connections, 6 horizontal layers are distinguished. Due to numerous convolutions and furrows, the surface area of ​​the bark reaches 0.2 m 2. Directly below the cortex is white matter, consisting of nerve fibers that transmit excitation to and from the cortex, as well as from one part of the cortex to another.

Cortical neurons and their connections. Despite the huge number of neurons in the cortex, very few of their varieties are known. Their main types are pyramidal and stellate neurons. Which do not differ in functional mechanism.

In the afferent function of the cortex and in the processes of switching excitation to neighboring neurons, the main role belongs to stellate neurons. They make up more than half of all cortical cells in humans. These cells have short branching axons that do not extend beyond the gray matter of the cortex, and short branching dendrites. Star-shaped neurons are involved in the processes of perception of irritation and the unification of the activities of various pyramidal neurons.

Pyramidal neurons carry out the efferent function of the cortex and intracortical processes of interaction between neurons distant from each other. They are divided into large pyramids, from which projection, or efferent, paths to subcortical formations begin, and small pyramids, which form associative paths to other sections of the cortex. The largest pyramidal cells - Betz's giant pyramids - are located in the anterior central gyrus, in the so-called motor cortex. A characteristic feature of large pyramids is their vertical orientation in the thickness of the crust. From the cell body, the thickest (apical) dendrite is directed vertically upwards to the surface of the cortex, through which various afferent influences from other neurons enter the cell, and the efferent process, the axon, departs vertically downwards.

The cerebral cortex is characterized by an abundance of interneuronal connections. As the human brain develops after birth, the number of intercentral interconnections increases, especially intensively up to 18 years.

The functional unit of the cortex is a vertical column of interconnected neurons. Vertically elongated large pyramidal cells with neurons located above and below them form functional associations of neurons. All neurons of the vertical column respond to the same afferent stimulus (from the same receptor) with the same response and jointly form efferent responses of pyramidal neurons.

The spread of excitation in the transverse direction - from one vertical column to another - is limited by the processes of inhibition. The occurrence of activity in the vertical column leads to the excitation of spinal motor neurons and the contraction of the muscles associated with them. This path is used, in particular, for voluntary control of limb movements.

Primary, secondary and tertiary fields of the cortex. Features of the structure and functional significance of individual sections of the cortex make it possible to distinguish individual cortical fields.

There are three main groups of fields in the cortex: primary, secondary and tertiary fields.

Primary fields are associated with the sense organs and organs of movement on the periphery; they mature earlier than others in ontogeny and have the largest cells. These are the so-called nuclear zones of the analyzers, according to I.P. Pavlov (for example, the field of pain, temperature, tactile and muscular-articular sensitivity in the posterior central gyrus of the cortex, the visual field in the occipital region, the auditory field in the temporal region and the motor field in the anterior central gyrus of the cortex) (Fig. 54). These fields carry out the analysis of individual stimuli entering the cortex from the corresponding receptors. When the primary fields are destroyed, so-called cortical blindness, cortical deafness, etc. occur. Secondary fields, or peripheral zones of analyzers, are located nearby, which are connected with individual organs only through primary fields. They serve to summarize and further process the incoming information. Separate sensations are synthesized in them into complexes that determine the processes of perception. When the secondary fields are affected, the ability to see objects, hear sounds is preserved, but the person does not recognize them, does not remember their meaning. Both humans and animals have primary and secondary fields.

Tertiary fields, or analyzer overlap zones, are the furthest from direct connections with the periphery. These fields are only available to humans. They occupy almost half of the territory of the cortex and have extensive connections with other parts of the cortex and with nonspecific brain systems. The smallest and most diverse cells predominate in these fields. The main cellular element here are stellate neurons. Tertiary fields are located in the posterior half of the cortex - on the borders of the parietal, temporal and occipital regions and in the anterior half - in the anterior parts of the frontal regions. In these zones, the largest number of nerve fibers connecting the left and right hemispheres ends, therefore their role is especially great in organizing the coordinated work of both hemispheres. Tertiary fields mature in humans later than other cortical fields; they carry out the most complex functions of the cortex. Here the processes of higher analysis and synthesis take place. In tertiary fields, on the basis of the synthesis of all afferent stimuli and taking into account the traces of previous stimuli, the goals and objectives of behavior are developed. According to them, the programming of motor activity takes place. The development of tertiary fields in humans is associated with the function of speech. Thinking (inner speech) is possible only with the joint activity of analyzers, the combination of information from which occurs in tertiary fields.

The main methods for studying the functions of the central nervous system in humans.

Methods for studying the functions of the central nervous system are divided into two groups: 1) direct study and 2) indirect (indirect) study.

The methods of recording the bioelectrical activity of individual neurons, the total activity of the neuronal pool or the brain as a whole (electroencephalography), computed tomography (positron emission tomography, magnetic resonance imaging), etc., are most widely used.

Electroencephalography - is registration from the surface of the skin head or from the surface of the cortex (the latter - in the experiment) total electric field of brain neurons during their excitation(Fig. 82).

Rice. 82. Electroencephalogram rhythms: A - basic rhythms: 1 - α-rhythm, 2 - β-rhythm, 3 - θ-rhythm, 4 - σ-rhythm; B - EEG desynchronization reaction of the occipital region of the cerebral cortex when opening the eyes () and restoration of the α-rhythm when closing the eyes (↓)

The origin of EEG waves is not well understood. It is believed that the EEG reflects the LP of many neurons - EPSP, IPSP, trace - hyperpolarization and depolarization, capable of algebraic, spatial and temporal summation.

This point of view is generally recognized, while the participation of AP in the formation of the EEG is denied. For example, W. Willes (2004) writes: "As for action potentials, their ion currents are too weak, fast and unsynchronized to be registered in the form of an EEG." However, this statement is not supported by experimental facts. To prove it, it is necessary to prevent the occurrence of AP in all CNS neurons and to record the EEG under the conditions of the occurrence of only EPSP and IPSP. But this is impossible. In addition, under natural conditions, EPSPs are usually the initial part of AP, so there are no grounds to assert that AP are not involved in the formation of the EEG.

Thus, EEG is a registration of the total electric field of AP, EPSP, IPSP, trace hyperpolarization and depolarization of neurons.

Four main physiological rhythms are recorded on the EEG: α-, β-, θ- and δ-rhythms, the frequency and amplitude of which reflect the degree of CNS activity.

In the study of the EEG describe the frequency and amplitude of the rhythm (Fig. 83).

Rice. 83. Frequency and amplitude of the electroencephalogram rhythm. T 1, T 2, T 3 - period (time) of oscillation; the number of oscillations in 1 second is the frequency of the rhythm; А 1 , А 2 – oscillation amplitude (Kiroi, 2003).

evoked potential method(EP) consists in registering changes in the electrical activity of the brain (electric field) (Fig. 84) that occur in response to irritation of sensory receptors (the usual version).

Rice. 84. Evoked potentials in a person to a flash of light: P - positive, N - negative components of EP; digital indices mean the sequence of positive and negative components in the composition of the EP. The start of recording coincides with the moment the flash light is turned on (arrow)

Positron emission tomography- a method of functional isotope mapping of the brain, based on the introduction of isotopes (13 M, 18 P, 15 O) into the bloodstream in combination with deoxyglucose. The more active part of the brain, the more it absorbs labeled glucose. The radioactive radiation of the latter is recorded by special detectors. Information from the detectors is sent to a computer that creates "slices" of the brain at the recorded level, reflecting the uneven distribution of the isotope due to the metabolic activity of brain structures, which makes it possible to judge possible CNS lesions.

Magnetic resonance imaging allows you to identify actively working areas of the brain. The technique is based on the fact that after the dissociation of oxyhemoglobin, hemoglobin acquires paramagnetic properties. The higher the metabolic activity of the brain, the greater the volumetric and linear blood flow in a given area of ​​the brain and the lower the ratio of paramagnetic deoxyhemoglobin to oxyhemoglobin. There are many foci of activation in the brain, which is reflected in the inhomogeneity of the magnetic field.

Stereotactic method. The method allows introducing macro- and microelectrodes, a thermocouple into various structures of the brain. Coordinates of brain structures are given in stereotaxic atlases. Through the inserted electrodes, it is possible to register the bioelectric activity of a given structure, to irritate or destroy it; through microcannulas, chemicals can be injected into the nerve centers or ventricles of the brain; With the help of microelectrodes (their diameter is less than 1 μm) brought close to the cell, it is possible to register the impulse activity of individual neurons and judge the participation of the latter in reflex, regulatory and behavioral reactions, as well as possible pathological processes and the use of appropriate therapeutic effects of pharmacological drugs.

Data on the functions of the brain can be obtained during operations on the brain. In particular, with electrical stimulation of the cortex during neurosurgical operations.

Questions for self-control

1. What are the three divisions of the cerebellum and their constituent elements that are structurally and functionally distinguished? What receptors send impulses to the cerebellum?

2. With what parts of the CNS is the cerebellum connected with the help of the lower, middle and upper legs?

3. With the help of what nuclei and structures of the brainstem does the cerebellum exercise its regulatory influence on the tone of skeletal muscles and motor activity of the body? Is it excitatory or inhibitory?

4. What structures of the cerebellum are involved in the regulation of muscle tone, posture and balance?

5. What structure of the cerebellum is involved in the programming of purposeful movements?

6. What effect does the cerebellum have on homeostasis, how does homeostasis change when the cerebellum is damaged?

7. List the parts of the CNS and the structural elements that make up the forebrain.

8. Name the formations of the diencephalon. What tone of skeletal muscles is observed in a diencephalic animal (the cerebral hemispheres have been removed), what is it expressed in?

9. What groups and subgroups are the thalamic nuclei divided into and how are they connected with the cerebral cortex?

10. What is the name of the neurons that send information to specific (projection) nuclei of the thalamus? What are the names of the paths that form their axons?

11. What is the role of the thalamus?

12. What functions do the nonspecific nuclei of the thalamus perform?

13. Name the functional significance of the associative zones of the thalamus.

14. What nuclei of the midbrain and diencephalon form subcortical visual and auditory centers?

15. In the implementation of what reactions, besides the regulation of the functions of internal organs, does the hypothalamus take part?

16. What part of the brain is called the highest autonomic center? What is Claude Bernard's thermal injection called?

17. What groups of chemicals (neurosecrets) come from the hypothalamus to the anterior pituitary gland and what is their significance? What hormones are released into the posterior pituitary gland?

18. What receptors that perceive deviations from the norm of the parameters of the internal environment of the body are found in the hypothalamus?

19. Centers of regulation of what biological needs are found in the hypothalamus

20. What structures of the brain make up the striopallidar system? What reactions occur in response to the stimulation of its structures?

21. List the main functions in which the striatum plays an important role.

22. What are the functional relationships between the striatum and the globus pallidus? What movement disorders occur when the striatum is damaged?

23. What movement disorders occur when the globus pallidus is damaged?

24. Name the structural formations that make up the limbic system.

25. What is characteristic for the spread of excitation between the individual nuclei of the limbic system, as well as between the limbic system and the reticular formation? How is this provided?

26. From what receptors and parts of the CNS do afferent impulses come to various formations of the limbic system, where does the limbic system send impulses?

27. What influences does the limbic system have on the cardiovascular, respiratory and digestive systems? Through what structures are these influences carried out?

28. Does the hippocampus play an important role in the processes of short-term or long-term memory? What experimental fact testifies to this?

29. Give experimental evidence that indicates the important role of the limbic system in the species-specific behavior of the animal and its emotional reactions.

30. List the main functions of the limbic system.

31. Functions of the circle of Peipets and the circle through the amygdala.

32. Bark of the cerebral hemispheres: ancient, old and new bark. Localization and functions.

33. Gray and white matter of CPB. Functions?

34. List the layers of the new cortex and their functions.

35. Fields of Brodmann.

36. Columnar organization of the KBP for Mountcastle.

37. Functional division of the cortex: primary, secondary and tertiary zones.

38. Sensory, motor and associative zones of the CBP.

39. What does the projection of general sensitivity in the cortex mean (Sensitive homunculus according to Penfield). Where in the cortex are these projections?

40. What does the projection of the motor system in the cortex mean (Motor homunculus according to Penfield). Where in the cortex are these projections?

50. Name the somatosensory zones of the cerebral cortex, indicate their location and purpose.

51. Name the main motor areas of the cerebral cortex and their locations.

52. What are Wernicke's and Broca's zones? Where are they located? What are the consequences if they are violated?

53. What is meant by a pyramidal system? What is its function?

54. What is meant by the extrapyramidal system?

55. What are the functions of the extrapyramidal system?

56. What is the sequence of interaction between the sensory, motor and association areas of the cortex when solving problems of recognizing an object and pronouncing its name?

57. What is interhemispheric asymmetry?

58. What functions does the corpus callosum perform and why is it cut in case of epilepsy?

59. Give examples of violations of interhemispheric asymmetry?

60. Compare the functions of the left and right hemispheres.

61. List the functions of the various lobes of the cortex.

62. Where is praxis and gnosis carried out in the cortex?

63. Neurons of what modality are located in the primary, secondary and associative zones of the cortex?

64. What zones occupy the largest area in the cortex? Why?

66. In what areas of the cortex are visual sensations formed?

67. In what areas of the cortex are auditory sensations formed?

68. In which areas of the cortex are tactile and pain sensations formed?

69. What functions will fall out in a person in violation of the frontal lobes?

70. What functions will fall out in a person in case of violation of the occipital lobes?

71. What functions will fall out in a person with a violation of the temporal lobes?

72. What functions will fall out in a person in case of violation of the parietal lobes?

73. Functions of the associative areas of the KBP.

74. Methods for studying the work of the brain: EEG, MRI, PET, the method of evoked potentials, stereotaxic and others.

75. List the main functions of the KBP.

76. What is understood by the plasticity of the nervous system? Explain with an example of the brain.

77. What functions of the brain will fall out if the cerebral cortex is removed from different animals?

2.3.15 . General characteristics of the autonomic nervous system

autonomic nervous system- this is a part of the nervous system that regulates the work of internal organs, the lumen of blood vessels, metabolism and energy, homeostasis.

Departments of the VNS. Currently, two departments of the ANS are generally recognized: sympathetic and parasympathetic. On fig. 85 shows the divisions of the ANS and the innervation of its divisions (sympathetic and parasympathetic) of various organs.

Rice. 85. Anatomy of the autonomic nervous system. The organs and their sympathetic and parasympathetic innervation are shown. T 1 -L 2 - nerve centers of the sympathetic division of the ANS; S 2 -S 4 - nerve centers of the parasympathetic division of the ANS in the sacral spinal cord, III-oculomotor nerve, VII-facial nerve, IX-glossopharyngeal nerve, X-vagus nerve - nerve centers of the parasympathetic division of the ANS in the brain stem

Table 10 lists the effects of the sympathetic and parasympathetic divisions of the ANS on effector organs, indicating the type of receptor on the cells of effector organs (Chesnokova, 2007) (Table 10).

Table 10. Influence of the sympathetic and parasympathetic divisions of the autonomic nervous system on some effector organs

In recent years, convincing evidence has been obtained proving the presence of serotonergic nerve fibers that are part of the sympathetic trunks and enhance contractions of the smooth muscles of the gastrointestinal tract.

Autonomic reflex arc has the same links as the arc of the somatic reflex (Fig. 83).

Rice. 83. Reflex arc of the autonomic reflex: 1 - receptor; 2 - afferent link; 3 - central link; 4 - efferent link; 5 - effector

But there are features of its organization:

1. The main difference is that the ANS reflex arc may close outside the CNS- intra- or extraorganically.

2. Afferent link of the autonomic reflex arc can be formed both by its own - vegetative, and somatic afferent fibers.

3. In the arc of the vegetative reflex, segmentation is less pronounced, which increases the reliability of autonomic innervation.

Classification of autonomic reflexes(by structural and functional organization):

1. Highlight central (various levels) And peripheral reflexes, which are divided into intra- and extraorganic.

2. Viscero-visceral reflexes- a change in the activity of the stomach when the small intestine is filled, inhibition of the activity of the heart when the P-receptors of the stomach are stimulated (Goltz reflex), etc. The receptive fields of these reflexes are localized in different organs.

3. Viscerosomatic reflexes- a change in somatic activity when the sensory receptors of the ANS are excited, for example, muscle contraction, movement of the limbs with strong irritation of the gastrointestinal tract receptors.

4. Somatovisceral reflexes. An example is the Dagnini-Ashner reflex - a decrease in heart rate with pressure on the eyeballs, a decrease in urine production with painful skin irritation.

5. Interoceptive, proprioceptive and exteroceptive reflexes - according to the receptors of the reflexogenic zones.

Functional differences between the ANS and the somatic nervous system. They are associated with the structural features of the ANS and the degree of influence of the cerebral cortex on it. Regulation of the functions of internal organs with the help of ANS can be carried out with a complete violation of its connection with the central nervous system, but less completely. ANS effector neuron located outside the CNS: either in extra- or intraorganic autonomic ganglia, forming peripheral extra- and intraorganic reflex arcs. If the connection between the muscles and the central nervous system is disturbed, somatic reflexes are eliminated, since all motor neurons are located in the central nervous system.

Influence of VNS on organs and tissues of the body not controlled directly consciousness(a person cannot arbitrarily control the frequency and strength of heart contractions, stomach contractions, etc.).

Generalized (diffuse) nature of influence in the sympathetic division of the ANS explained by two main factors.

Firstly, most adrenergic neurons have long postganglionic thin axons that branch many times in the organs and form the so-called adrenergic plexuses. The total length of the terminal branches of the adrenergic neuron can reach 10–30 cm. These branches along their course have numerous (250–300 per 1 mm) extensions in which norepinephrine is synthesized, stored, and recaptured. When an adrenergic neuron is excited, norepinephrine is released from a large number of these extensions into the extracellular space, while it acts not on individual cells, but on many cells (for example, smooth muscle), since the distance to postsynaptic receptors reaches 1-2 thousand nm. One nerve fiber can innervate up to 10 thousand cells of the working organ. In the somatic nervous system, the segmental nature of innervation provides a more accurate sending of impulses to a specific muscle, to a group of muscle fibers. One motor neuron can innervate only a few muscle fibers (for example, in the muscles of the eye - 3-6, fingers - 10-25).

Secondly, there are 50-100 times more postganglionic fibers than preganglionic ones (there are more neurons in ganglia than preganglionic fibers). In parasympathetic nodes, each preganglionic fiber contacts only 1-2 ganglion cells. Small lability of neurons of autonomic ganglia (10-15 pulses/s) and speed of excitation in autonomic nerves: 3-14 m/s in preganglionic fibers and 0.5-3 m/s in postganglionic ones; in somatic nerve fibers - up to 120 m/s.

In organs with double innervation effector cells receive sympathetic and parasympathetic innervation(Fig. 81).

Each muscle cell of the gastrointestinal tract appears to have a triple extraorganic innervation - sympathetic (adrenergic), parasympathetic (cholinergic) and serotonergic, as well as innervation from neurons of the intraorganic nervous system. However, some of them, such as the bladder, receive mainly parasympathetic innervation, and a number of organs (sweat glands, muscles that raise hair, spleen, adrenal glands) receive only sympathetic innervation.

The preganglionic fibers of the sympathetic and parasympathetic nervous systems are cholinergic(Fig. 86) and form synapses with ganglionic neurons with the help of ionotropic N-cholinergic receptors (mediator - acetylcholine).

Rice. 86. Neurons and receptors of the sympathetic and parasympathetic nervous system: A - adrenergic neurons, X - cholinergic neurons; solid line - preganglionic fibers; dotted line - postganglionic

The receptors got their name (D. Langley) because of their sensitivity to nicotine: small doses excite ganglion neurons, large doses block them. Sympathetic ganglia located extraorganically, Parasympathetic- usually, intraorganically. In the autonomic ganglia, in addition to acetylcholine, there are neuropeptides: methenkephalin, neurotensin, CCK, substance P. They perform modeling role. N-cholinergic receptors are also localized on the cells of skeletal muscles, carotid glomeruli and the adrenal medulla. N-cholinergic receptors of neuromuscular junctions and autonomic ganglia are blocked by various pharmacological drugs. In the ganglia there are intercalary adrenergic cells that regulate the excitability of ganglion cells.

Mediators of postganglionic fibers of the sympathetic and parasympathetic nervous systems are different.