The hypothalamus is a part of the diencephalon located below the thalamus. It is responsible for heat exchange processes in the body, sexual behavior, changes in sleep and wakefulness, feelings of thirst, hunger, regulates metabolism and maintains physical and physiological balance (homeostasis).

The hypothalamus is connected to virtually all nerve centers and plays a particularly important role in controlling higher brain functions (memory), emotional states, thus influencing human behavior patterns. He is responsible for autonomic reactions nervous system and controls the functioning of the organs of the endocrine system through the release of liberins and statins, which stimulate or “inhibit” the pituitary gland’s production of somatotropin, luteinizing and follicle-stimulating hormones, prolactin, and corticotropin.

The most common diseases of the hypothalamus are hypo- and hyperfunctions caused by inflammation or tumor, stroke, and head injury. Hyperfunction can be expressed through the appearance of secondary sexual characteristics in children aged 8-9 years, and hypofunction leads to the development of diabetes insipidus.

Pituitary

The pituitary gland is an appendage of the brain, the main endocrine gland, “subordinate” to which are the thyroid, gonads and adrenal glands. This organ consists of the neuro- and adenohypophysis. The first accumulates vasopressin and oxytocin synthesized by the hypothalamus.

Vasopressin increases blood pressure, and its deficiency can trigger the development of diabetes insipidus. Oxytocin is important during childbirth, as it causes contractions of the uterus, and in the postpartum period it promotes the formation of milk in the female body. The adenohypophysis is responsible for the production of other hormones (growth, prolactin, thyroid stimulating hormone, etc.).

The following diseases are associated with pituitary gland disorders: pathological tall stature, dwarfism, Cushing's disease, hyperfunction and insufficient concentration of thyroid hormones, menstrual irregularities in women. Excess prolactin in the body of men leads to impotence.

A possible cause of excess levels of pituitary hormones is an adenoma, which manifests itself in frequent headaches and significant deterioration in vision. The reasons for the lack of hormones in the body are various blood flow disorders, traumatic brain injuries, previous operations, radiation, congenital insufficient development of the pituitary gland, hemorrhage.

The hypothalamus is one of the main structures involved in the formation of behavioral reactions of the body, which are necessary for the constancy of the internal environment. Stimulation of its nuclei leads to the formation of purposeful behavior - eating, sexual, aggressive, etc. It also plays a major role in the emergence of the body’s basic drives (motivations).

In vertebrates, the hypothalamus is the main subcortical center for the integration of visceral processes. It controls all the basic homeostatic functions of the body. The integrative function of the hypothalamus is ensured by autonomic, somatic and endocrine mechanisms.

Transmission of information in the hypothalamus

Sensitive information from internal organs and the surface of the body enters the hypothalamus along the ascending spinobulbar tract. Some of them pass through the thalamus, others through the limbic region of the midbrain, and others follow as yet incompletely identified polysynaptic pathways. In addition, the hypothalamus is equipped with its own specific “inputs”. It contains osmoreceptors that are highly sensitive to changes in the osmotic pressure of the internal environment and thermoreceptors that are sensitive to changes in blood temperature. The efferent pathways of the hypothalamus are polysynaptic. They associate it with the reticular formation of the brain stem and the nuclei of the spinal cord. Descending influences of the hypothalamus provide regulation of functions mainly through the autonomic nervous system. At the same time, an important component in the implementation of descending influences of the hypothalamus are pituitary hormones . In addition to afferent and efferent connections, there is a commissural pathway in the hypothalamus. Thanks to it, the medial hypothalamic nuclei of one side come into contact with the medial and lateral nuclei of the other side.

Hypothalamic connections

Numerous connections of the hypothalamus with other brain formations contribute to the generalization of excitations arising in the cells of the hypothalamus. Excitation primarily spreads to the limbic structures of the brain and through the nuclei of the thalamus to the anterior parts of the cerebral cortex. The degree of distribution of ascending activating influences of the hypothalamus depends on the magnitude of the initial excitation of the hypothalamic centers.

Hypothalamus and behavioral reactions of the body

Hypothalamus- one of the main structures involved in the formation of behavioral reactions of the body, which are necessary for the constancy of the internal environment. Stimulation of its nuclei leads to the formation of purposeful behavior - eating, sexual, aggressive, etc. It also plays the main role in the emergence of the basic drives (motivations) of the body.

Blood supply to the hypothalamus

The main source of arterial blood supply to the hypothalamic nuclei is the arterial circle of the brain. Its branches provide an abundant isolated blood supply to individual groups of nuclei, the capillary network of which is several times denser than the blood supply to other parts of the nervous system. The capillary network of the hypothalamus is distinguished by high permeability for large molecular compounds. The virtual absence of a blood-brain barrier in this area allows these blood compounds to have a direct effect on hypothalamic neurons.

Hypothalamic-pituitary system

Numerous neural and vascular connections between the hypothalamus and pituitary gland form the basis of a functional complex called the hypothalamic-pituitary system. The main purpose of the complex is to integrate the nervous and hormonal regulation of the visceral functions of the body. From the hypothalamus, it is carried out in two ways: paraadenopituitary (bypassing the adenohypophysis) and transadenopituitary (through the adenohypophysis).

Pituitary hormones

The release of hormones from the anterior pituitary gland is influenced by the hormones of neurons in the hypophysiotropic zone of the medial region of the hypothalamus. They are able to have a stimulating and inhibitory effect on pituitary cells. In the first case, these are the so-called releasing factors (liberins), in the second - inhibitory factors (statins). Regulation of visceral functions by the hypothalamic-pituitary system is carried out according to the feedback principle. Its effect is manifested even after complete separation of the medial region of the hypothalamus from other parts of the brain. The role of the central nervous system is to adapt this regulation to the internal and external needs of the body.

Hypothalamic cells

The cells of the hypothalamus are selectively sensitive to the content of certain substances in the blood and with any change in their concentration they become excited. For example, hypothalamic neurons are sensitive to the slightest deviations in blood pH, O2 and CO2 voltage, and ion content, especially K and Na. Thus, the supraoptic nucleus contains cells that are selectively sensitive to changes in blood osmotic pressure, the ventromedial nucleus – to glucose content, and the anterior hypothalamus – to sex hormones. Consequently, the cells of the hypothalamus function as receptors that perceive changes in homeostasis. They have the ability to transform humoral changes in the internal environment into a nervous process - biologically colored excitation. However, they can be selectively activated not only by changes in certain blood constants, but also by nerve impulses from the corresponding organs associated with this need. Receptor cells operate according to a trigger type. Excitation does not arise in them immediately as soon as any blood constant changes, but after a certain period of time, when their depolarization reaches a critical level. Consequently, the neurons of the motivational centers of the hypothalamus are distinguished by the periodicity of their work. In the case when a change in the blood constant is maintained for a long time, the depolarization of neurons rises to a critical level and the state of excitation is established at this level as long as there is a change in the constant that caused the development of the excitation process. The constant impulse activity of these neurons disappears only when the irritation that caused it is eliminated, i.e., the content of one or another blood factor is normalized. Excitation of some cells of the hypothalamus can occur periodically after a few hours, as, for example, with a lack of glucose, others - after several days or even months, as, for example, with a change in the content of sex hormones.

Removal of the hypothalamus

Destruction of the nuclei or removal of the entire hypothalamus is accompanied by a disruption of the homeostatic functions of the body. The hypothalamus plays a leading role in maintaining optimal levels of metabolism (protein, carbohydrate, fat, mineral, water) and energy, in regulating the temperature balance of the body, cardiovascular, digestive, excretory, respiratory systems. The functions of the endocrine glands are influenced by it. When hypothalamic structures are excited, the nervous component of complex reactions is necessarily supplemented by the hormonal component.

Posterior nuclei of the hypothalamus

Studies have shown that stimulation of the posterior nuclei of the hypothalamus is accompanied by effects similar to irritation of the sympathetic nervous system: dilation of the pupils and palpebral fissure, increased heart rate, increased blood pressure blood, inhibition of the motor activity of the stomach and intestines, and an increase in the concentration of adrenaline in the blood. The 3rd region of the hypothalamus has an inhibitory effect on sexual development. Its damage also leads to hyperglycemia, and in some cases to the development of obesity. Destruction of the posterior nuclei of the hypothalamus is accompanied by a complete loss of thermoregulation. The body temperature of these animals cannot be maintained. Reactions that occur upon stimulation of the posterior hypothalamus and are accompanied by activation of the sympathetic nervous system, mobilization of the body's energy, and an increase in the ability to exercise are called ergotropic.

Anterior nuclei of the hypothalamus

Stimulation of the group of anterior nuclei of the hypothalamus is characterized by reactions similar to irritation of the parasympathetic nervous system, constriction of the pupils and palpebral fissure, a decrease in heart rate, a decrease in blood pressure, increased motor activity of the stomach and intestines, activation of the secretion of gastric glands, increased insulin secretion and, as a result, decrease in blood glucose levels. The group of anterior nuclei of the hypothalamus has a stimulating effect on sexual development. The mechanism of heat loss is also associated with it. The destruction of this area leads to disruption of the heat transfer process, as a result of which the body quickly overheats.

Middle nuclei of the hypothalamus

The middle group of hypothalamic nuclei provides mainly regulation of metabolism. The study of the regulation of eating behavior has shown that it occurs as a result of reciprocal interactions of the lateral and ventromedial hypothalamic nuclei. Activation of the first causes increased food consumption, and its bilateral destruction is accompanied by a complete refusal of food, up to exhaustion and death of the animal. On the contrary, increased activity of the ventromedial nucleus reduces the level of food motivation. When this nucleus is destroyed, an increase in food consumption (hyperphagia) and obesity occur. These data made it possible to regard the ventromedial nuclei as structures through which food intake is limited, i.e., associated with satiety, and the lateral nuclei as structures that increase the level of food motivation, i.e., associated with hunger. At the same time, it has not yet been possible to identify the functional or structural accumulations of neurons responsible for this or that behavior. Consequently, cellular formations that ensure the formation of holistic behavior from individual reactions should not be considered as anatomically limited structures known as the hunger center and the satiety center. Probably, groups of hypothalamic cells associated with the performance of any function differ from each other in the nature of afferent and efferent connections, synaptic organization and mediators. It is assumed that the neural networks of the hypothalamus contain numerous programs and their activation through signals from other parts of the brain or interoceptors leads to the formation of the necessary behavioral and neurohumoral reactions. Studies of the role of the hypothalamus by methods of irritating or destroying its nuclei have led to the conclusion that the areas responsible for food and water intake appear to overlap each other. The most increased need for water was observed with stimulation of the paraventricular nucleus of the hypothalamus.

Interaction of the hypothalamus with other parts of the brain

The hypothalamus is in continuous cyclical interactions with other parts of the subcortex and cerebral cortex. Due to the fact that nervous and humoral signaling about various internal needs is addressed to the hypothalamic nuclei, they acquire the significance of a trigger mechanism for motivational excitations. The introduction of neurotropic substances of specific action can selectively block various hypothalamic mechanisms involved in the formation of such body states as fear, hunger, thirst, etc. The hypothalamus is under the regulatory influence of the cerebral cortex. Receiving information about the initial state of the body and the environment, cortical neurons exert a descending influence on all subcortical structures, including the hypothalamus, regulating their level of excitation. Cortical mechanisms suppress many emotions and primary excitations formed with the participation of the hypothalamic nuclei. Therefore, removal of the cortex often leads to the development of reactions of imaginary rage, expressed in dilated pupils, tachycardia, salivation, increased intracranial pressure, etc. Thus, the hypothalamus, having a well-developed and complex system of connections, occupies a leading place in the regulation of many functions of the body and, above all, in the constancy of the internal environment. The function of the autonomic nervous system and endocrine glands is under its control. It is involved in the regulation of eating and sexual behavior, sleep and wakefulness, emotional activity, maintaining body temperature, etc.

Hypothalamus(hypothalamus) - a section of the diencephalon, which plays a leading role in the regulation of many functions of the body, and above all the constancy of the internal environment, the hypothalamus is the highest vegetative center, carrying out the complex integration of the functions of various internal systems and their adaptation to the integral activity of the body, plays a significant role in maintaining an optimal level of metabolism and energy, in thermoregulation, in regulating the activity of the digestive, cardiovascular, excretory, respiratory and endocrine systems. Under the control of the hypothalamus are endocrine glands such as pituitary gland, thyroid gland, gonads (see Testicle, Ovaries), pancreas, adrenal glands and etc.

The hypothalamus is located inferior to the thalamus under the hypothalamic sulcus. Its anterior border is the optic chiasma (chiasma opticum), the terminal plate (lamina terminalis) and the anterior commissure (commissura ant.). The posterior border passes behind the lower edge of the mastoid bodies (corpora mamillaria). Anteriorly, the cell groups of the hypothalamus without interruption pass into the cell groups of the plate of the transparent septum (lamina septi pellucidi).

Pathways closely connect the hypothalamus with neighboring structures brain . The blood supply to the nuclei of the hypothalamus is carried out by branches of the arterial circle of the brain. The relationship between the hypothalamus and the adenohypophysis occurs through the portal vessels of the adenohypophysis. A characteristic feature of the blood vessels of the hypothalamus is the permeability of their walls to large protein molecules.

Despite small sizes hypothalamus, its structure is characterized by significant complexity. Groups of cells form separate nuclei of the hypothalamus (see illustration to Art. Brain). In humans and other mammals, the hypothalamus usually has 32 pairs of nuclei. Between adjacent nuclei there are intermediate nerve cells or small groups of them, so not only the nuclei, but also some internuclear hypothalamic zones may have physiological significance. The nuclei of the hypothalamus are formed by nerve cells that do not have secretory function and neurosecretory cells. Neurosecretory nerve cells are concentrated directly near the walls of the third ventricle of the brain. In their structural characteristics, these cells resemble cells of the reticular formation and produce physiologically active substances - hypothalamic neurohormones.

The hypothalamus has three vaguely demarcated regions: anterior, middle and posterior. Neurosecretory cells are concentrated in the anterior region of the hypothalamus, where they form the supraopticus (nucl. supraopticus) and paraventricular (nucl. paraventricularis) nuclei on each side. The episodic nucleus consists of cells lying between the wall of the third ventricle of the brain and the dorsal surface of the optic chiasm. The paraventricular nucleus looks like a plate between the fornix (fornix) and the wall of the third ventricle of the brain. The axons of the neurons of the paraventricular and supravisual nuclei, forming the hypothalamic-pituitary bundle, reach the posterior lobe of the pituitary gland, where hypothalamic neurohormones accumulate, from where they enter the bloodstream.

Between the supravisual and paraventricular nuclei there are numerous single neurosecretory cells or groups of them. Neurosecretory cells of the supravisual nucleus of the hypothalamus produce predominantly antidiuretic hormone (vasopressin), and the paraventricular nucleus produces oxytocin.

In the middle region of the hypothalamus, around the lower edge of the third ventricle of the brain, lie the gray tuberous nuclei (nucll. tuberaies), arcuately covering the infundibulum of the pituitary gland. Above and slightly lateral to them are the large ventromedial and dorsomedial nuclei.

In the posterior region of the hypothalamus there are nuclei consisting of scattered large cells, among which there are clusters of small cells. This section also includes the medial and lateral nuclei of the mastoid body (nucll. corporis mamillaris mediales et laterales), which on the lower surface of the diencephalon look like paired hemispheres . The cells of these nuclei give rise to one of the so-called projection systems of the hypothalamus into the medulla oblongata and spinal cord. The largest cell cluster is the medial nucleus of the mastoid body. Anterior to the mammillary bodies protrudes the bottom of the third ventricle of the brain in the form of a gray mound (tuber cinereum), formed by a thin plate of gray matter. This protrusion extends into a funnel, which passes distally into the pituitary stalk and further into the posterior lobe of the pituitary gland. The expanded upper part of the funnel - the median eminence - is lined with ependyma, followed by a layer of nerve fibers of the hypothalamic-pituitary fascicle and thinner fibers originating from the nuclei of the gray tuberosity. The outer part of the median eminence is formed by supporting neuroglial (ependymal) fibers, between which numerous nerve fibers lie. Deposition of neurosecretory granules is observed in and around these nerve fibers. That., hypothalamus formed by a complex of nerve conduction and neurosecretory cells. In this regard, regulatory influences are transmitted to the hypothalamus to effectors, incl. and to the endocrine glands, not only with the help of hypothalamic neurohormones carried by the bloodstream and, therefore, acting humorally, but also along efferent nerve fibers.

The hypothalamus plays a significant role in the regulation and coordination of the functions of the autonomic nervous system. The nuclei of the posterior region of the hypothalamus participate in the regulation of the function of its sympathetic part, and the functions of the parasympathetic part of the autonomic nervous system are regulated by the nuclei of its anterior and middle regions. Stimulation of the anterior and middle regions of the hypothalamus causes reactions characteristic of the parasympathetic nervous system - a decrease in heart rate, increased intestinal motility, increased bladder tone, etc., and irritation of the posterior region of the hypothalamus is manifested by an increase in sympathetic reactions - increased heart rate, etc.

Vasomotor reactions of hypothalamic origin are closely related to the state of the autonomic nervous system. Various types of arterial hypertension that develop after stimulation of the hypothalamus are caused by the combined influence of the sympathetic part of the autonomic nervous system and the release of adrenaline adrenal glands, although in this case the influence of the neurohypophysis cannot be excluded, especially in the genesis of stable arterial hypertension.

From a physiological point of view, the hypothalamus has a number of features, primarily this concerns its participation in the formation of behavioral reactions that are important for maintaining the constancy of the internal environment of the body (see. Homeostasis). Irritation of the hypothalamus leads to the formation of purposeful behavior - eating, drinking, sexual, aggressive, etc. The hypothalamus plays a major role in the formation of the body’s basic drives (see. Motivations). In some cases, when the superomedial nucleus and gray tuberous region of the hypothalamus are damaged, excessive obesity is observed as a result of polyphagia (bulimia) or cachexia. Damage to the posterior hypothalamus causes hyperglycemia. The role of the suprasensory and paraventricular nuclei in the mechanism of diabetes insipidus has been established (see. Diabetes insipidus). Activation of neurons in the lateral hypothalamus causes the formation of food motivation. With bilateral destruction of this section, food motivation is completely eliminated.

Extensive connections of the hypothalamus with other structures of the brain contribute to the generalization of excitations that arise in its cells. The hypothalamus is in continuous interaction with other parts of the subcortex and the cerebral cortex. This is precisely what underlies the participation of the hypothalamus in emotional activity (see. Emotions). The cerebral cortex may have an inhibitory effect on the functions of the hypothalamus. Acquired cortical mechanisms suppress many emotions and primary impulses that are formed with its participation. Therefore, decortication often leads to the development of an “imaginary rage” reaction (pupil dilation, tachycardia, development of intracranial hypertension, increased salivation, etc.).

Hypothalamus is one of the main structures involved in the regulation of shifts sleep and wakefulness. Clinical studies have established that the symptom of lethargic sleep in epidemic encephalitis is caused precisely by damage to the hypothalamus. In maintaining a state of wakefulness decisive role plays the posterior region of the hypothalamus. Extensive destruction of the middle region of the hypothalamus in the experiment led to the development of long-term sleep. Sleep disturbance in the form of narcolepsy is explained by damage to the hypothalamus and the rostral part of the reticular formation of the midbrain.

The hypothalamus plays an important role in thermoregulation. Destruction of the posterior parts of the hypothalamus leads to a persistent decrease in body temperature.

The cells of the hypothalamus have the ability to transform humoral changes in the internal environment of the body into a nervous process. The centers of the hypothalamus are characterized by pronounced selectivity of excitation depending on various changes in blood composition and acid-base state, as well as nerve impulses from the corresponding organs. Excitation in hypothalamic neurons, which have selective reception in relation to blood constants, does not occur immediately as soon as any of them changes, but after a certain period of time. If the change in the blood constant is maintained for a long time, then in this case the excitability of the hypothalamic neurons quickly rises to a critical value and the state of this excitation is maintained at a high level as long as the change in the constant exists. Excitation of some cells of the hypothalamus can occur periodically after a few hours, as, for example, during hypoglycemia, others - after several days or even months, as, for example, when the content of sex hormones in the blood changes.

Informative methods for studying the hypothalamus are plethysmographic, biochemical, X-ray studies, etc. Plethysmographic studies (see. Plethysmography) reveal a wide range of changes in the hypothalamus - from a state of autonomic vascular instability and paradoxical reaction to complete areflexia. In biochemical studies in patients with damage to the hypothalamus, regardless of its cause (tumor, inflammatory process, etc.), an increase in the content of catecholamines and histamine in the blood is often determined, the relative content of a-globulins increases and the relative content of b-globulins in the blood serum decreases, excretion changes with urine 17-ketosteroids. With various forms of damage to the hypothalamus, disturbances in thermoregulation and sweating intensity appear. Damage to the nuclei of the hypothalamus (mainly the supraocular and paraventricular) is most likely in diseases of the endocrine glands, traumatic brain injuries leading to redistribution of cerebrospinal fluid, tumors, neuroinfections, intoxications, etc. Due to increased permeability of the vascular walls during infections and intoxications, the hypothalamic nuclei can be exposed to pathogenic exposure to bacterial and viral toxins and chemicals circulating in the blood. Neuroviral infections are especially dangerous in this regard. Hypothalamic lesions are observed in basal tuberculous meningitis, syphilis, sarcoidosis, lymphogranulomatosis, and leukemia.

Of the hypothalamic tumors, the most common are various types of gliomas, craniopharyngiomas, ectopic pinealomas and teratomas, meningiomas: suprasellar tumors grow in the hypothalamus pituitary adenomas. Clinical manifestations and treatment of dysfunctions and diseases of the hypothalamus - see. Hypothalamic-pituitary insufficiency, Hypothalamic syndromes, Adiposogenital dystrophy, Itsenko-Cushing disease, Diabetes insipidus, Hypogonadism, Hypothyroidism and etc.

Bibliography: Babichev V.N. Neuroendocrinology of gender. M., 1981; aka, Neurohormonal regulation of the ovarian cycle, M., 1984; Schreiber V. Pathophysiology of the endocrine glands, trans. from Czech, Prague, 1987.

Cerebral cortex

The highest division of the central nervous system is the cerebral cortex (cerebral cortex). It ensures the perfect organization of animal behavior based on innate and acquired functions during ontogenesis.

Morphofunctional organization

The cerebral cortex has the following morphofunctional features:

Multilayer arrangement of neurons;

Modular principle of organization;

Somatotopic localization of receptive systems;

Screenness, i.e., the distribution of external reception on the plane of the neuronal field of the cortical end of the analyzer;

Dependence of the level of activity on the influence of subcortical structures and reticular formation;

Availability of representation of all functions of the underlying structures of the central nervous system;

Cytoarchitectonic distribution into fields;

The presence in specific projection sensory and motor systems of secondary and tertiary fields with associative functions;

Availability of specialized associative areas;

Dynamic localization of functions, expressed in the possibility of compensation for the functions of lost structures;

Overlap of zones of neighboring peripheral receptive fields in the cerebral cortex;

Possibility of long-term preservation of traces of irritation;

Reciprocal functional relationship between excitatory and inhibitory states;

The ability to irradiate excitation and inhibition;

The presence of specific electrical activity.

Deep grooves divide each cerebral hemisphere into the frontal, temporal, parietal, occipital lobes and insula. The insula is located deep in the Sylvian fissure and is covered from above by parts of the frontal and parietal lobes of the brain.

The cerebral cortex is divided into ancient (archicortex), old (paleocortex) and new (neocortex). The ancient cortex, along with other functions, is related to smell and ensuring the interaction of brain systems. The old cortex includes the cingulate gyrus and hippocampus. In the neocortex, the greatest development of size and differentiation of functions is observed in humans. The thickness of the neocortex ranges from 1.5 to 4.5 mm and is maximum in the anterior central gyrus.

The functions of individual zones of the neocortex are determined by the characteristics of its structural and functional organization, connections with other brain structures, participation in the perception, storage and reproduction of information in the organization and implementation of behavior, regulation of the functions of sensory systems and internal organs.

The peculiarities of the structural and functional organization of the cerebral cortex are due to the fact that in evolution there was a corticalization of functions, i.e., the transfer of the functions of underlying brain structures to the cerebral cortex. However, this transfer does not mean that the cortex takes over the functions of other structures. Its role comes down to the correction of possible dysfunctions of systems interacting with it, a more advanced, taking into account individual experience, analysis of signals and the organization of an optimal response to these signals, the formation in one’s own and other interested brain structures of memorable traces about the signal, its characteristics, meaning and the nature of the reaction to it. Subsequently, as automation occurs, the reaction begins to be carried out by subcortical structures.

The total area of ​​the human cerebral cortex is about 2200 cm2, the number of cortical neurons exceeds 10 billion. The cortex contains pyramidal, stellate, and fusiform neurons.

Pyramidal neurons are of different sizes, their dendrites bear a large number of spines; the axon of a pyramidal neuron, as a rule, goes through the white matter to other areas of the cortex or to the structures of the central nervous system.

Stellate cells have short, well-branched dendrites and a short ascon, which provides connections between neurons within the cerebral cortex itself.

Fusiform neurons provide vertical or horizontal connections between neurons of different layers of the cortex.

The cerebral cortex has a predominantly six-layer structure

Layer I is the upper molecular layer, represented mainly by the branches of the ascending dendrites of pyramidal neurons, among which rare horizontal cells and granule cells are located; fibers of the nonspecific nuclei of the thalamus also come here, regulating the level of excitability of the cerebral cortex through the dendrites of this layer.

Layer II - external granular, consists of stellate cells that determine the duration of circulation of excitation in the cerebral cortex, i.e., related to memory.

Layer III is the outer pyramidal layer, formed from small pyramidal cells and, together with layer II, provides cortico-cortical connections of various convolutions of the brain.

Layer IV is internal granular and contains predominantly stellate cells. Specific thalamocortical pathways end here, i.e., pathways starting from the receptors of the analyzers.

Layer V is the internal pyramidal layer, a layer of large pyramids that are output neurons, their axons go to the brain stem and spinal cord.

Layer VI is a layer of polymorphic cells; most of the neurons in this layer form corticothalamic tracts.

The cellular composition of the cortex in terms of diversity of morphology, function, and forms of communication has no equal in other parts of the central nervous system. The neuronal composition and distribution of neurons into layers in different areas of the cortex are different, which made it possible to identify 53 cytoarchitectonic fields in the human brain. The division of the cerebral cortex into cytoarchitectonic fields is more clearly formed as its function improves in phylogenesis.

In higher mammals, in contrast to lower ones, secondary fields 6, 8 and 10 are well differentiated from the motor field 4, functionally ensuring high coordination and accuracy of movements; around visual field 17 are secondary visual fields 18 and 19, which are involved in analyzing the meaning of a visual stimulus (organizing visual attention, controlling eye movement). Primary auditory, somatosensory, skin and other fields also have nearby secondary and tertiary fields that ensure the association of the functions of this analyzer with the functions of other analyzers. All analyzers are characterized by the somatotopic principle of organizing the projection of peripheral receptive systems onto the cerebral cortex. Thus, in the sensory area of ​​the cortex of the second central gyrus there are areas representing the localization of each point on the skin surface; in the motor area of ​​the cortex, each muscle has its own topic (its own place), by irritating which one can obtain the movement of a given muscle; in the auditory area of ​​the cortex there is a topical localization of certain tones (tonotopic localization); damage to a local area of ​​the auditory area of ​​the cortex leads to hearing loss for a certain tone.

In the same way, there is a topographic distribution in the projection of retinal receptors onto the visual field of cortex 17. In the event of the death of the local zone of field 17, the image is not perceived if it falls on the part of the retina projecting onto the damaged zone of the cerebral cortex.

A special feature of cortical fields is the screen principle of their functioning. This principle lies in the fact that the receptor projects its signal not onto one cortical neuron, but onto a field of neurons, which is formed by their collaterals and connections. As a result, the signal is not focused point to point, but on many different neurons, which ensures it full analysis and the possibility of transfer to other interested structures. Thus, one fiber entering the visual cortex can activate a zone measuring 0.1 mm. This means that one axon distributes its action over more than 5,000 neurons.

Input (afferent) impulses enter the cortex from below and ascend to the stellate and pyramidal cells of the III-V layers of the cortex. From the stellate cells of layer IV, the signal goes to pyramidal neurons of layer III, and from here along associative fibers to other fields, areas of the cerebral cortex. Stellate cells of field 3 switch signals going to the cortex to layer V pyramidal neurons, from here the processed signal leaves the cortex to other brain structures.

In the cortex, input and output elements, together with stellate cells, form so-called columns - functional units of the cortex, organized in the vertical direction. The proof of this is the following: if the microelectrode is inserted perpendicularly into the cortex, then on its way it encounters neurons that respond to one type of stimulation, but if the microelectrode is inserted horizontally along the cortex, then it encounters neurons that respond to different types of stimuli.

The diameter of the column is about 500 µm and it is determined by the distribution zone of collaterals of the ascending afferent thalamocortical fiber. Adjacent columns have relationships that organize sections of many columns in the organization of a particular reaction. Excitation of one of the columns leads to inhibition of neighboring ones.

Each column can have a number of ensembles that implement any function according to the probabilistic-statistical principle. This principle lies in the fact that upon repeated stimulation, not the entire group of neurons, but part of it, participates in the reaction. Moreover, each time the part of the participating neurons may be different in composition, i.e., a group of active neurons is formed (probabilistic principle), which is statistically sufficient on average to provide the desired function (statistical principle).

As already mentioned, different areas of the cerebral cortex have different fields, determined by the nature and number of neurons, the thickness of the layers, etc. The presence of structurally different fields also implies their different functional purposes (Fig. 4.14). Indeed, the cerebral cortex is divided into sensory, motor and associative areas.

Sensory areas

The cortical ends of the analyzers have their own topography and certain afferents of the conducting systems are projected onto them. The cortical ends of the analyzers of different sensory systems overlap. In addition, in each sensory system of the cortex there are polysensory neurons that respond not only to “their” adequate stimulus, but also to signals from other sensory systems.

The cutaneous receptive system, thalamocortical pathways, project to the posterior central gyrus. There is a strict somatotopic division here. The receptive fields of the skin of the lower extremities are projected onto the upper sections of this gyrus, the torso onto the middle sections, and the arms and head onto the lower sections.

Pain and temperature sensitivity are mainly projected onto the posterior central gyrus. In the cortex of the parietal lobe (fields 5 and 7), where the sensitivity pathways also end, a more complex analysis is carried out: localization of irritation, discrimination, stereognosis.

When the cortex is damaged, the functions of the distal parts of the extremities, especially the hands, are more severely affected.

The visual system is represented in the occipital lobe of the brain: fields 17, 18, 19. The central visual pathway ends in field 17; it informs about the presence and intensity of the visual signal. In fields 18 and 19, the color, shape, size, and quality of objects are analyzed. Damage to field 19 of the cerebral cortex leads to the fact that the patient sees, but does not recognize the object (visual agnosia, and color memory is also lost).

The auditory system is projected in the transverse temporal gyri (Heschl's gyrus), in the depths of the posterior sections of the lateral (Sylvian) fissure (fields 41, 42, 52). It is here that the axons of the posterior colliculi and lateral geniculate bodies end.

The olfactory system projects to the region of the anterior end of the hippocampal gyrus (field 34). The bark of this area has not a six-layer, but a three-layer structure. When this area is irritated, olfactory hallucinations are observed; damage to it leads to anosmia (loss of smell).

The taste system is projected in the hippocampal gyrus adjacent to the olfactory area of ​​the cortex (field 43).

Motor areas

For the first time, Fritsch and Gitzig (1870) showed that stimulation of the anterior central gyrus of the brain (field 4) causes a motor response. At the same time, it is recognized that the motor area is an analytical one.

In the anterior central gyrus, the zones whose irritation causes movement are presented according to the somatotopic type, but upside down: in the upper parts of the gyrus - the lower limbs, in the lower - the upper.

In front of the anterior central gyrus lie premotor fields 6 and 8. They organize not isolated, but complex, coordinated, stereotypical movements. These fields also provide regulation of smooth muscle tone and plastic muscle tone through subcortical structures.

The second frontal gyrus, occipital, and superior parietal regions also take part in the implementation of motor functions.

The motor area of ​​the cortex, like no other, has a large number of connections with other analyzers, which apparently determines the presence of a significant number of polysensory neurons in it.

Associative areas

All sensory projection areas and the motor cortex occupy less than 20% of the surface of the cerebral cortex (see Fig. 4.14). The rest of the cortex constitutes the association region. Each associative area of ​​the cortex is connected by powerful connections with several projection areas. It is believed that in associative areas the association of multisensory information occurs. As a result, complex elements of consciousness are formed.

Association areas of the human brain are most pronounced in the frontal, parietal and temporal lobes.

Each projection area of ​​the cortex is surrounded by association areas. Neurons in these areas are often multisensory and have greater learning abilities. Thus, in associative visual field 18, the number of neurons “learning” a conditioned reflex response to a signal is more than 60% of the number of background active neurons. For comparison: there are only 10-12% of such neurons in the projection field 17.

Damage to area 18 results in visual agnosia. The patient sees, walks around objects, but cannot name them.

The polysensory nature of neurons in the associative area of ​​the cortex ensures their participation in the integration of sensory information, the interaction of sensory and motor areas of the cortex.

In the parietal associative area of ​​the cortex, subjective ideas about the surrounding space and our body are formed. This becomes possible due to the comparison of somatosensory, proprioceptive and visual information.

Frontal associative fields have connections with the limbic part of the brain and are involved in organizing action programs during the implementation of complex motor behavioral acts.

The first and most characteristic feature of the associative areas of the cortex is the multisensory nature of their neurons, and not primary, but rather processed information is received here, highlighting the biological significance of the signal. This allows you to formulate a program of targeted behavioral act.

The second feature of the associative area of ​​the cortex is the ability to undergo plastic rearrangements depending on the significance of incoming sensory information.

The third feature of the associative area of ​​the cortex is manifested in the long-term storage of traces of sensory influences. Destruction of the associative area of ​​the cortex leads to severe impairments in learning and memory. The speech function is associated with both sensory and motor systems. The cortical motor speech center is located in the posterior part of the third frontal gyrus (area 44), most often in the left hemisphere, and was described first by Dax (1835) and then by Broca (1861).

The auditory speech center is located in the first temporal gyrus of the left hemisphere (field 22). This center was described by Wernicke (1874). The motor and auditory speech centers are interconnected by a powerful bundle of axons.

Speech functions associated with written speech - reading, writing - are regulated by the angular gyrus of the visual cortex of the left hemisphere of the brain (field 39).

When the motor center of speech is damaged, motor aphasia develops; in this case, the patient understands speech, but cannot speak himself. If the auditory center of speech is damaged, the patient can speak, express his thoughts orally, but does not understand someone else's speech, hearing is preserved, but the patient does not recognize words. This condition is called sensory auditory aphasia. The patient often talks a lot (logorrhea), but his speech is incorrect (agrammatism), and there is a replacement of syllables and words (paraphasia).

Damage to the visual center of speech leads to the inability to read and write.

An isolated writing disorder, agraphia, also occurs in cases of dysfunction of the posterior parts of the second frontal gyrus of the left hemisphere.

In the temporal region there is field 37, which is responsible for remembering words. Patients with lesions in this field do not remember the names of objects. They resemble forgetful people who need to be prompted with the right words. The patient, having forgotten the name of an object, remembers its purpose and properties, so he describes their qualities for a long time, tells what they do with this object, but cannot name it. For example, instead of the word “tie,” the patient, looking at the tie, says: “this is something that is put on the neck and tied with a special knot so that it is beautiful when they go to visit.”

The distribution of functions across brain regions is not absolute. It has been established that almost all areas of the brain have polysensory neurons, that is, neurons that respond to various stimuli. For example, if field 17 of the visual area is damaged, its function can be performed by fields 18 and 19. In addition, different motor effects of irritation of the same motor point of the cortex are observed depending on the current motor activity.

If the operation of removing one of the zones of the cortex is carried out in early childhood, when the distribution of functions is not yet rigidly fixed, the function of the lost area is almost completely restored, i.e. in the cortex there are manifestations of mechanisms of dynamic localization of functions that make it possible to compensate for functionally and anatomically damaged structures.

An important feature of the cerebral cortex is its ability to retain traces of excitation for a long time.

Trace processes in the spinal cord after its irritation persist for a second; in the subcortical-stem regions (in the form of complex motor-coordinating acts, dominant attitudes, emotional states) last for hours; in the cerebral cortex, trace processes can be maintained according to the feedback principle throughout life. This property gives the cortex exceptional importance in the mechanisms of associative processing and storage of information, accumulation of a knowledge base.

The preservation of traces of excitation in the cortex is manifested in fluctuations in the level of its excitability; these cycles last 3-5 minutes in the motor cortex and 5-8 minutes in the visual cortex.

The main processes occurring in the cortex are realized in two states: excitation and inhibition. These states are always reciprocal. They arise, for example, within the motor analyzer, which is always observed during movements; they can also occur between different analyzers. The inhibitory influence of one analyzer on others ensures that attention is focused on one process.

Reciprocal activity relationships are very often observed in the activity of neighboring neurons.

The relationship between excitation and inhibition in the cortex manifests itself in the form of so-called lateral inhibition. With lateral inhibition, a zone of inhibited neurons is formed around the excitation zone (simultaneous induction) and its length, as a rule, is twice as large as the excitation zone. Lateral inhibition provides contrast in perception, which in turn makes it possible to identify the perceived object.

In addition to lateral spatial inhibition, in cortical neurons, after excitation, inhibition of activity always occurs, and vice versa, after inhibition - excitation - the so-called sequential induction.

In cases where inhibition is unable to restrain the excitatory process in a certain zone, irradiation of excitation occurs throughout the cortex. Irradiation can occur from neuron to neuron, along the systems of associative fibers of layer I, and it has a very low speed - 0.5-2.0 m/s. In another case, irradiation of excitation is possible due to axon connections of pyramidal cells of the third layer of the cortex between neighboring structures, including between different analyzers. Irradiation of excitation ensures the relationship between the states of the cortical systems during the organization of conditioned reflex and other forms of behavior.

Along with the irradiation of excitation, which occurs due to impulse transmission of activity, there is irradiation of the state of inhibition throughout the cortex. The mechanism of irradiation of inhibition is the transfer of neurons into an inhibitory state under the influence of impulses coming from excited areas of the cortex, for example, from symmetrical areas of the hemispheres.

Electrical manifestations of cortical activity

Assessing the functional state of the human cerebral cortex is a difficult and still unsolved problem. One of the signs that indirectly indicates the functional state of brain structures is the registration of electrical potential fluctuations in them.

Each neuron has a membrane charge, which, when activated, decreases, and when inhibited, it often increases, i.e., hyperpolarization develops. Glia in the brain also have charge cell membranes. The dynamics of the charge of the membrane of neurons, glia, processes occurring in synapses, dendrites, axon hillock, in the axon - all these are constantly changing processes, varied in intensity and speed, the integral characteristics of which depend on the functional state of the nervous structure and ultimately determine its electrical indicators. If these indicators are recorded through microelectrodes, then they reflect the activity of a local (up to 100 μm in diameter) part of the brain and are called focal activity.

If the electrode is located in a subcortical structure, the activity recorded through it is called a subcorticogram, if the electrode is located in the cerebral cortex - a corticogram. Finally, if the electrode is located on the surface of the scalp, then the total activity of both the cortex and subcortical structures is recorded. This manifestation of activity is called an electroencephalogram (EEG) (Fig. 4.15).

All types of brain activity are dynamically subject to intensification and weakening and are accompanied by certain rhythms of electrical oscillations. In a person at rest, in the absence of external stimuli, slow rhythms of changes in the state of the cerebral cortex predominate, which is reflected on the EEG in the form of the so-called alpha rhythm, the frequency of which is 8-13 per second, and the amplitude is approximately 50 μV.

A person’s transition to active activity leads to a change in the alpha rhythm to a faster beta rhythm, which has an oscillation frequency of 14-30 per second, the amplitude of which is 25 μV.

The transition from a state of rest to a state of focused attention or to sleep is accompanied by the development of a slower theta rhythm (4-8 vibrations per second) or delta rhythm (0.5-3.5 vibrations per second). The amplitude of slow rhythms is 100-300 μV (see Fig. 4.15).

When, against a background of rest or another state, the brain is presented with a new, rapidly increasing stimulus, so-called evoked potentials (EPs) are recorded on the EEG. They represent a synchronous reaction of many neurons in a given cortical area.

The latent period and amplitude of the EP depend on the intensity of the applied stimulation. The components of the EP, the number and nature of its fluctuations depend on the adequacy of the stimulus relative to the EP recording zone.

EP may consist of a primary response or of a primary and a secondary response. Primary responses are biphasic, positive-negative oscillations. They are recorded in the primary zones of the analyzer’s cortex and only with a stimulus adequate for the given analyzer. For example, visual stimulation for the primary visual cortex (field 17) is adequate (Fig. 4.16). Primary responses are characterized by a short latent period (LP), two-phase oscillation: first positive, then negative. The primary response is formed due to short-term synchronization of the activity of nearby neurons.

Secondary responses are more variable in latency, duration, and amplitude than primary ones. As a rule, secondary responses more often occur to signals that have a certain semantic meaning, to stimuli that are adequate for a given analyzer; they are well formed with training.

Interhemispheric relationships

The relationship of the cerebral hemispheres is defined as a function that ensures the specialization of the hemispheres, facilitating the implementation of regulatory processes, increasing the reliability of controlling the activities of organs, organ systems and the body as a whole.

The role of relationships between the cerebral hemispheres is most clearly manifested in the analysis of functional interhemispheric asymmetry.

Asymmetry in the functions of the hemispheres was first discovered in the 19th century, when attention was paid to the different consequences of damage to the left and right half of the brain.

In 1836, Mark Dax spoke at a meeting of the medical society in Montpellier (France) with a short report on patients suffering from loss of speech - a condition known to specialists as aphasia. Dax noticed a connection between the loss of speech and the damaged side of the brain. In his observations, more than 40 patients with aphasia showed signs of damage to the left hemisphere. The scientist was unable to detect a single case of aphasia with damage to only the right hemisphere. Summarizing these observations, Dax made the following conclusion: each half of the brain controls its own specific functions; speech is controlled by the left hemisphere.

His report was not successful. Some time after the death of Dax Broca, during a post-mortem examination of the brains of patients suffering from loss of speech and unilateral paralysis, in both cases clearly identified foci of damage that involved parts of the left frontal lobe. This area has since become known as Broca's area; it was defined by him as an area in the posterior parts of the inferior frontal gyrus.

Having analyzed the connection between preference for one of the two hands and speech, he suggested that speech and greater dexterity in the movements of the right hand are associated with the superiority of the left hemisphere in right-handed people.

Ten years after Broca's observations were published, the concept now known as hemispheric dominance had become the dominant view of the relationship between the two hemispheres of the brain.

In 1864, the English neurologist John Jackson wrote: “Not so long ago, it was rarely doubted that the two hemispheres were the same, both physically and functionally, but now, thanks to the research of Dax, Broca and others, it has become clear that the damage one hemisphere can cause a person to completely lose speech, the previous point of view has become untenable.”

D. Jackson put forward the idea of ​​a “leading” hemisphere, which can be considered as a predecessor to the concept of hemispheric dominance. “The two hemispheres cannot simply duplicate each other,” he wrote, “if damage to only one of them can lead to loss of speech. For these processes (speech), above which there is nothing, there must certainly be a leading party.” Jackson further concluded that “in most people the dominant side of the brain is left-hand side the so-called will, and that the right side is automatic."

By 1870, other researchers began to realize that many types of speech disorders could be caused by damage to the left hemisphere. K. Wernicke found that patients with damage to the posterior part of the temporal lobe of the left hemisphere often experienced difficulties in understanding speech.

Some patients with damage to the left rather than the right hemisphere had difficulty reading and writing. The left hemisphere was also thought to control “purposeful movements.”

The totality of these data became the basis for the idea of ​​the relationship between the two hemispheres. One hemisphere (usually the left in right-handed people) was considered to be leading for speech and other higher functions, the other (right), or “secondary,” was considered to be under the control of the “dominant” left.

The speech asymmetry of the brain hemispheres, which was the first to be identified, predetermined the idea of ​​the equipotentiality of the cerebral hemispheres of children before the appearance of speech. It is believed that brain asymmetry develops during the maturation of the corpus callosum.

The concept of hemispheric dominance, according to which in all gnostic and intellectual functions the left hemisphere is dominant in “right-handed people”, and the right one is “deaf and dumb”, has existed for almost a century. However, evidence gradually accumulated that the idea of ​​the right hemisphere as secondary, dependent, does not correspond to reality. Thus, patients with disorders of the left hemisphere of the brain perform worse on tests for the perception of shapes and assessment of spatial relationships than healthy people. Neurologically healthy subjects who speak two languages ​​(English and Yiddish) better identify English words presented in the right visual field, and Yiddish words in the left. It was concluded that this kind of asymmetry is related to reading skills: English words are read from left to right, and Yiddish words are read from right to left.

Almost simultaneously with the spread of the concept of hemispheric dominance, evidence began to appear indicating that the right, or secondary, hemisphere also has its own special abilities. Thus, Jackson made the statement that the ability to form visual images is localized in the posterior lobes of the right brain.

Damage to the left hemisphere usually leads to low rates on verbal ability tests. At the same time, patients with damage to the right hemisphere typically performed poorly on nonverbal tests that included manipulating geometric shapes, assembling puzzles, filling in missing parts of pictures or figures, and other tasks involving the assessment of shape, distance, and spatial relationships.

It was found that damage to the right hemisphere was often accompanied by profound disturbances in orientation and consciousness. Such patients have poor spatial orientation and are unable to find their way to the house in which they have lived for many years. Damage to the right hemisphere has also been associated with certain types of agnosia, i.e., impairments in the recognition or perception of familiar information, depth perception, and spatial relationships. One of the most interesting forms of agnosia is facial agnosia. A patient with such agnosia is not able to recognize a familiar face, and sometimes cannot distinguish people from each other at all. Recognition of other situations and objects, for example, may not be impaired. Additional evidence indicating a specialization of the right hemisphere was obtained from observations of patients suffering from severe speech disorders, who, however, often retain the ability to sing. In addition, clinical reports have suggested that damage to the right side of the brain can lead to loss of musical abilities without affecting speech. This disorder, called amusia, was most often seen in professional musicians who had suffered a stroke or other brain damage.

After neurosurgeons performed a series of commissurotomy operations and psychological studies were performed on these patients, it became clear that the right hemisphere has its own higher gnostic functions.

There is an idea that interhemispheric asymmetry depends critically on the functional level of information processing. In this case, decisive importance is attached not to the nature of the stimulus, but to the features of the gnostic task facing the observer. It is generally accepted that the right hemisphere is specialized in processing information at the figurative functional level, the left - at the categorical level. The use of this approach allows us to remove a number of intractable contradictions. Thus, the advantage of the left hemisphere, discovered when reading musical notes and finger signs, is explained by the fact that these processes occur at the categorical level of information processing. Comparison of words without their linguistic analysis is more successfully carried out when they are addressed to the right hemisphere, since to solve these problems it is sufficient to process information at the figurative functional level.

Interhemispheric asymmetry depends on the functional level of information processing: the left hemisphere has the ability to process information at both semantic and perceptual functional levels, the capabilities of the right hemisphere are limited to the perceptual level.

In cases of lateral presentation of information, three methods of interhemispheric interactions can be distinguished, manifested in the processes of visual recognition.

1. Parallel activities. Each hemisphere processes information using its own mechanisms.

2. Election activities. Information is processed in the “competent” hemisphere.

3. Joint activities. Both hemispheres are involved in information processing, consistently playing a leading role at certain stages of this process.

The main factor determining the participation of one or another hemisphere in the processes of recognition of incomplete images is what elements the image lacks, namely, what is the degree of significance of the elements missing in the image. If image details were removed without taking into account the degree of their significance, identification was more difficult in patients with lesions of the structures of the right hemisphere. This gives grounds to consider the right hemisphere to be the leading one in recognizing such images. If a relatively small but highly significant area was removed from the image, then recognition was impaired primarily when the structures of the left hemisphere were damaged, which indicates the predominant participation of the left hemisphere in the recognition of such images.

In the right hemisphere, a more complete assessment of visual stimuli is carried out, while in the left, their most significant, significant features are assessed.

When a significant number of details of the image to be identified are removed, the likelihood that the most informative, significant parts of it will not be distorted or removed is small, and therefore the left hemisphere recognition strategy is significantly limited. In such cases, the strategy characteristic of the right hemisphere, based on the use of all information contained in the image, is more adequate.

Difficulties in implementing the left-hemisphere strategy under these conditions are further aggravated by the fact that the left hemisphere has insufficient “abilities” for accurate assessment individual elements Images. This is also evidenced by studies according to which the assessment of the length and orientation of lines, the curvature of arcs, and the size of angles is impaired primarily with lesions of the right hemisphere.

A different picture is observed in cases where most of the image is removed, but its most significant, informative section is preserved. In such situations, a more adequate method of identification is based on the analysis of the most significant fragments of the image - a strategy used by the left hemisphere.

In the process of recognizing incomplete images, structures of both the right and left hemispheres are involved, and the degree of participation of each of them depends on the characteristics of the presented images, and primarily on whether the image contains the most significant informative elements. In the presence of these elements, the predominant role belongs to the left hemisphere; when they are removed, the right hemisphere plays a predominant role in the recognition process.

Hypothalamus, what is it and what is it responsible for, this main organ of the endocrine system? It is called the endocrine brain, it is found in amphibians and mammals, and they need it to regulate the functions of the organs of the hormonal system. Scientists say this ancient brain organ allowed amphibians and mammals to survive as species on earth. The hypothalamus is responsible for preserving youth, prolonging life, mental and physical unity of a representative of the species. It is his well-coordinated work that makes a person harmonious and energetic, and disruptions in his work lead to premature old age.

The hypothalamus is located in the brain, representing a part of the diencephalon.

Its location is at the bottom of the third ventricle of the brain. This is a nerve formation capable of producing hormones. The hypothalamus occupies a small place in the brain. Its weight is only 5 g, but this mass is enough to combine nervous and endocrine regulatory mechanisms into a common neuroendocrine system. It controls the activity of the human endocrine system with the help of neurons that produce hormones that affect the production of hormones from another important hormonal organ - the pituitary gland.

The hypothalamus does not have a strictly limited location. This part of the brain is considered to be part of a network of neurons that stretches from the midbrain to the deep parts of the forebrain, including the olfactory system. Its location is limited above by the thalamus, below by the midbrain, and in front of it is the optic chiasm. At the back is the pituitary gland, which is connected to the hypothalamus by the pituitary stalk and participates with it in processes that regulate metabolism.

The structure of the hypothalamus is designed so that it can receive all the information it needs and instantly respond to signals, regulating the production of hormones by the internal secretion organs.

The hypothalamus is conventionally divided into 3 zones:

  • periventricular;
  • medial;
  • lateral.

The periventricular zone is a thin strip adjacent to the third ventricle, at the bottom of which the hypothalamus is located.

In the medial zone, several nuclear regions are distinguished, located in the anteroposterior direction. The medial part of the hypothalamus largely has bilateral connections with the lateral zone and independently receives signals from some parts of the brain. It is an intermediate link between the nervous and endocrine systems.

In this area there are special neurons that perceive the most important parameters of blood and cerebrospinal fluid. They monitor the internal state of the body and control the water and electrolyte composition of the plasma, blood temperature and the content of hormones in it.

In the lateral hypothalamus, neurons are randomly located around the medial forebrain bundle, going to the anterior centers of the diencephalon. The bundle consists of long and short fibers directed in different sides from the center. These fibrous tissues are involved in the implementation of afferent and efferent connections of the hypothalamus, through which the central organ of the endocrine system communicates with other parts of the brain.

Its nerve and secretion-producing cells have the form of nuclei and are arranged in pairs. The nuclei of the hypothalamus regulate connections between neurons and are responsible for communication between sections of the brain and endocrine organs. The nuclei of the hypothalamus represent clusters of nerve cells in the anterior, posterior and intermediate regions and form more than 30 pairs located on the right and left sides of the third ventricle. The nuclei of the hypothalamus produce neurosecretion, which is transported through the processes of these cells to the region of the neurohypophysis, enhancing or inhibiting the production of hormones.

Some of the nuclei, connecting with the pituitary gland, form connections that regulate the production of hormones that have a vasoconstrictor and antidiuretic effect. These same connections are responsible for the mechanisms that stimulate the contractility of the uterine muscles, enhance lactation, and inhibit the development and function of the corpus luteum. Hormones secreted by these important representatives of the endocrine system affect changes in the tone of the smooth muscles of the gastrointestinal tract.

Functions of the organ

The processes occurring in the hypothalamus are responsible for the functioning of the autonomic nervous and endocrine systems necessary to maintain homeostasis. This is the name given to the body’s ability to maintain a constant internal environment and ensure the preservation of functions responsible for life, excluding automatic respiratory movements, heart rhythm and blood pressure. The functions of the hypothalamus are designed to maintain important vital parameters. They are responsible for body temperature, acid-base balance, energy balance, regulating them in a small range and keeping them near optimal physiological values.

The functions of the hypothalamus extend to the organization of population behavior and its preservation as a species. It shapes various aspects behavior and is responsible for the instincts of self-preservation, which contribute to the preservation of humanity as a biological species. With changes and stressful situations regulates the state of internal and external environment, causing mechanisms such as:

  • appetite;
  • caring for offspring;
  • memory;
  • food-procuring behavior;
  • sexual behavior;
  • reproduction;
  • sleep and wakefulness;
  • emotions.

The body, thanks to the hypothalamus, is able to provide vitality to a person in extreme conditions. It controls the constancy of the internal environment during sudden changes in the individual’s living conditions. The normal functioning of the hypothalamus allows people to survive in the most difficult conditions of life, when strength is running out.

Causes of Pineal Gland Disorder

Under what circumstances can an area of ​​the brain deeply hidden in the skull become significantly damaged? Pathological changes in the hypothalamus are mostly observed in women. The cause of disruption of the pineal gland is the peculiarity of the vessels of the hypothalamic region, which have a high degree of permeability. When the body is affected by toxins and viruses, there is always a danger that the infection can affect the brain and easily penetrate the endocrine gland through the bloodstream. Disturbances in the functioning of the hypothalamus cause various life situations. It can be:

  • a brain tumor;
  • flu;
  • various viral neuroinfections;
  • malaria;
  • rheumatism;
  • chronic tonsillitis;
  • closed craniocerebral injury;
  • vascular diseases;
  • chronic intoxication.

Brain injury that destroys the hypothalamus leads to death. The destruction of the nerve pathways between the midbrain and medulla oblongata causes disturbances in thermoregulation processes, which leads to the rapid decline of life.

When to see a doctor

Disturbance in the activity of the hypothalamus due to compression by a brain tumor leads to disruptions in the functioning of many systems and organs. Women aged 30-40 years especially suffer from disorders, when their reproductive functions begin to fade and the endocrine system begins to fail.

They develop hyperprolactinemia, in which the production of the hormone prolactin increases. Disorders of the hypothalamus cause menstrual dysfunction.

If the pineal gland malfunctions, the actions of the pituitary gland are inhibited, which causes disturbances in the production of the hormone cortisone. Very often this causes dysfunction in the thyroid gland.

If a malfunction of the organ occurs in childhood, the patient stops growing and the child does not develop secondary sexual characteristics. The development of diabetes insipidus directly indicates pathology of the hypothalamus.

The presence of pathologies in the area of ​​the pineal gland leads to dysfunction of the nervous system and organ of vision. Patients may find:

  • atherosclerosis;
  • sudden increase in body weight;
  • myocardial dystrophy;
  • hematopoietic pathologies.

In patients who were healthy yesterday, when the hypothalamus is damaged, the following pathological disorders appear:

  • vegetative;
  • endocrine;
  • exchange;
  • trophic.

If a person suspects signs and symptoms of hypothalamic damage, he should seek medical help from an endocrinologist or neurologist.