The bulk of the diencephalon (20 g) is the thalamus. The paired organ is ovoid in shape, the anterior part of which is pointed (anterior tubercle), and the posterior part is widened (cushion) hanging over the geniculate bodies. The left and right thalami are connected by the interthalamic commissure. The gray matter of the thalamus is divided by lamellae of white matter into anterior, medial and lateral parts. When talking about the thalamus, they also include the metathalamus (geniculate body), which belongs to the thalamic region. The thalamus is the most developed in humans. The thalamus, the visual thalamus, is a nuclear complex in which the processing and integration of almost all signals going to the cortex occurs big brain from the spinal, midbrain, cerebellum, basal ganglia of the brain.

Morphofunctional organization

The thalamus, the visual thalamus, is a nuclear complex in which the processing and integration of almost all signals going to the cerebral cortex from the spinal cord, midbrain, cerebellum, and basal ganglia of the brain occurs. In the nuclei of the thalamus, information coming from extero-, proprioceptors and interoreceptors is switched and thalamocortical pathways begin. Considering that the geniculate bodies are the subcortical centers of vision and hearing, and the frenulum node and the anterior visual nucleus are involved in the analysis of olfactory signals, it can be argued that the visual thalamus as a whole is a subcortical “station” for all types of sensitivity. Here, irritations from the external and internal environment are integrated and then enter the cerebral cortex.

The visual thalamus is the center of organization and implementation of instincts, drives, and emotions. The ability to receive information about the state of many body systems allows the thalamus to participate in the regulation and determination of the functional state of the body. In general (this is confirmed by the presence of about 120 multifunctional nuclei in the thalamus).

Functions of the thalamic nuclei

The nuclei form unique complexes, which can be divided into 3 groups based on their projection into the cortex. The anterior one projects the axons of its neurons into the cingulate gyrus of the cerebral cortex. Medial - in the frontal lobe of the cortex. Lateral - in the parietal, temporal, occipital lobes of the cortex. The nuclei of the thalamus are functionally divided into specific, nonspecific and associative according to the nature of the pathways entering and exiting them.

Specific sensory and non-sensory nuclei

Specific nuclei include the anterior ventral, medial, ventrolateral, postlateral, postmedial, lateral and medial geniculate bodies. The latter belong to the subcortical centers of vision and hearing, respectively. The main functional unit of specific thalamic nuclei are “relay” neurons, which have few dendrites and a long axon; their function is to switch information going to the cerebral cortex from skin, muscle and other receptors.

In turn, specific (relay) nuclei are divided into sensory and non-sensory. From specific sensory nuclei, information about the nature of sensory stimuli arrives in strictly defined areas of the III-IV layers of the cerebral cortex. Dysfunction of specific nuclei leads to loss of specific types of sensitivity, since the nuclei of the thalamus, like the cerebral cortex, have a somatotopic localization. Individual neurons of specific thalamic nuclei are excited by receptors only of their own type. Signals from receptors in the skin, eyes, ear, and muscular system go to specific nuclei of the thalamus. Signals from the interoceptors of the projection zones of the vagus and celiac nerves and the hypothalamus also converge here. The lateral geniculate body has direct efferent connections with the occipital lobe of the cerebral cortex and afferent connections with the retina and the anterior colliculus. Neurons of the lateral geniculate bodies react differently to color stimulation, turning on and off the light, i.e. can perform a detector function. The medial geniculate body receives afferent impulses from the lateral lemniscus and from the inferior colliculi. Efferent pathways from the medial geniculate bodies go to the temporal zone of the cerebral cortex, reaching there the primary auditory area of ​​the cortex.

Non-sensory the nuclei switch to the cortex non-sensory impulses entering the thalamus from different parts of the brain. The anterior nuclei receive impulses mainly from the papillary bodies of the hypothalamus. Neurons of the anterior nuclei are projected into the limbic cortex, from where axonal connections go to the hippocampus and again to the hypothalamus, resulting in the formation of a neural circle, the movement of excitation along which ensures the formation of emotions (“Peipetz’s emotional ring”). In this regard, the anterior nuclei of the thalamus are considered part of the limbic system. The ventral nuclei are involved in the regulation of movement, thus performing a motor function. In these nuclei, impulses from the basal ganglia, the dentate nucleus of the cerebellum, and the red nucleus of the midbrain switch, which is then projected into the motor and premotor cortex. Through these nuclei of the thalamus, complex motor programs formed in the cerebellum and basal ganglia are transmitted to the motor cortex.

Nonspecific nuclei

An evolutionarily more ancient part of the thalamus, including paired reticular nuclei and the intralaminar (intralamellar) nuclear group. The reticular nuclei contain predominantly small, multi-processed neurons and are functionally considered to be a derivative of the reticular formation of the brainstem. The neurons of these nuclei form their connections according to the reticular type. Their axons rise into the cerebral cortex and contact all its layers, forming diffuse connections. Nonspecific nuclei receive connections from the reticular formation of the brainstem, hypothalamus, limbic system, basal ganglia, and specific nuclei of the thalamus. Thanks to these connections, the nonspecific nuclei of the thalamus act as an intermediary between the brain stem and cerebellum, on the one hand, and the new cortex, limbic system and basal ganglia, on the other hand, combining them into a single functional complex.

Associative kernels

Association nuclei receive impulses from other nuclei of the thalamus. Efferent outputs from them are directed mainly to the associative fields of the cortex. The main cellular structures of these nuclei are multipolar, bipolar triprocess neurons, i.e. neurons capable of performing polysensory functions. A number of neurons change activity only with simultaneous complex stimulation. Pillow receives the main impulse from the geniculate bodies and nonspecific nuclei of the thalamus. Efferent pathways go from it to the temporo-parietal-occipital zones of the cortex, which are involved in gnostic (recognition of objects, phenomena), speech and visual functions (integration of a word with a visual image), as well as in the perception of a “body diagram”. Mediodorsal nucleus receives impulses from the hypothalamus, amygdala, hippocampus, thalamic nuclei, and central gray matter of the brainstem. The projection of this nucleus extends to the associative frontal and limbic cortex. It is involved in the formation of emotional and behavioral motor activity. Lateral nuclei receive visual and auditory impulses from the geniculate bodies and somatosensory impulses from the ventral nucleus.

The complex structure of the thalamus, the presence of interconnected specific, nonspecific and associative nuclei in it, allows it to organize such motor reactions as sucking, chewing, swallowing, and laughter. Motor reactions are integrated in the thalamus with the autonomic processes that provide these movements.

Thalamus- a massive paired formation that occupies the main part of the diencephalon.

Nerve cells thalamus, when grouped, they form a large number of nuclei: in total, up to 40 such formations are distinguished. They are divided into several main groups: anterior, intralaminar, median and posterior. In each of these main groups, smaller nuclei are distinguished, differing from each other both in neural organization and in the characteristics of afferent and efferent projections. From a functional point of view, it is customary to distinguish between nonspecific and specific nuclei of the thalamus. Neurons of nonspecific nuclei send axons diffusely to the entire neocortex, while neurons of specific nuclei form connections only with cells of certain cortical fields.

The fibers of various ascending tracts end on the neurons of specific nuclei. The axons of these neurons form direct monosynaptic connections with neurons of the sensory and associative cortex. The cells of the nuclei of the lateral group of the thalamus, including the posterior ventral nucleus, receive impulses from skin receptors, the motor apparatus, and the cerebellothalamic pathway.

Neurons of a specific complex of nuclei send axons that have almost no collaterals towards the cortex. In contrast, neurons of the nonspecific system send axons that give rise to many collaterals.

Functions of the thalamus

All sensory signals, with the exception of those arising in the olfactory tract, reach the cerebral cortex only through thalamocortical projections. The thalamus is a kind of gate through which basic information about the world around us and the state of our body enters the cortex and reaches consciousness.

The fact that afferent signals on their way to the cerebral cortex are switched on thalamic neurons is important. Inhibitory influences coming to the thalamus from the cortex, other formations and neighboring thalamic nuclei allow for better transmission of the most important information to the cerebral cortex. Inhibition suppresses weak excitatory influences, due to which the most important information coming to the thalamus from various receptors is highlighted.

Through the nonspecific nuclei of the thalamus, ascending activating influences from the reticular formation of the brain stem enter the cerebral cortex. The system of nonspecific nuclei of the thalamus controls the rhythmic activity of the cerebral cortex and performs the functions of an intrathalamic integrating system.

In addition to specific influences on the cortex, a number of thalamic nuclei, especially the nuclei of the dorsal group, have a regulatory effect on subcortical structures. It is likely that through these nuclei the closure of the pathways of some reflexes occurs without the participation of the cerebral cortex.

HYPOTHALAMUS is the center for the regulation of autonomic functions and the highest endocrine center.

The hypothalamus is formed by a group of small nuclei located at the base of the brain, near the pituitary gland. The cell nuclei that form the hypothalamus are the highest subcortical centers of the autonomic nervous system and all vital functions of the body.

The cluster of neuronal formations that form the hypothalamus can be divided into preoptic, anterior, middle, outer and posterior groups of nuclei. The organization of the hypothalamus is characterized by extensive and very complex afferent and efferent connections.

Afferent signals to the hypothalamus come from the cerebral cortex, thalamic structures, and the nuclei of the basal ganglia. One of the main efferent pathways is the medullary fasciculus, or paraventricular system, and the mamillotegmental tract. The fibers of these pathways run in a caudal direction along the walls of the cerebral aqueduct or aqueduct of Sylvius and give numerous branches to the structures of the midbrain. The axons of the cells of the hypothalamic nuclei also form a large number of short efferent pathways going to the thalamic and subthalamic regions and to other subcortical formations.

Functions of the hypothalamus

Results obtained by selective stimulation or destruction of certain nuclei showed that the lateral and dorsal groups of nuclei increase the tone of the sympathetic nervous system. Irritation of the area of ​​the middle nuclei (in particular, the gray tuberosity) causes a decrease in the tone of the sympathetic nervous system. There is experimental evidence of the presence of a sleep center and a wake-up center in the hypothalamus.

The hypothalamus plays an important role in thermoregulation.

In the area of ​​the middle and lateral nuclei there are groups of neurons considered as centers of satiety and hunger.

During fasting, the content of amino acids, fatty acids, glucose and other substances decreases in the blood. This leads to the activation of certain hypothalamic neurons and the development of complex behavioral reactions of the body aimed at satisfying the feeling of hunger.

Adaptive behavioral reactions develop when there is a lack of water in the body, which leads to a feeling of thirst due to the activation of the hypothalamic zones. As a result, water consumption increases sharply (polydipsia). On the contrary, the destruction of these hypothalamic centers leads to a refusal of water (adipsia).

The hypothalamus contains centers associated with the regulation of sexual behavior.

The hypothalamus takes part in the process of alternating sleep and wakefulness.

The main hormones secreted by the posterior lobe of the pituitary gland are antidiuretic hormone, which regulates water metabolism, as well as hormones that regulate the activity of the uterus and the function of the mammary glands.

Like any other organ of the brain, the thalamus has an extremely important and irreplaceable function for the body. It’s hard to imagine, but this relatively small organ is responsible for all mental functions: perception and understanding, memory and thinking, because thanks to it we see, understand, feel the world and perceive everything that surrounds us. Thanks to its work, we navigate in space and time, feel pain, this “sensitivity collector” perceives and processes information received from all receptors, except the sense of smell, and transmits the necessary signal to the desired part of the cerebral cortex. As a result, the body gives the correct reaction, displays the correct behavior patterns to the corresponding stimulus or signal.

General information

The diencephalon is located under the corpus callosum and consists of: the thalamus (thalamic brain) and the hypothalamus.

The thalamus (aka: visual thalamus, sensitivity collector, body informant) is a section of the diencephalon located in its upper part, above the brain stem. Sensory signals, impulses from the most different parts body and from all receptors (except smell). Here they are processed, the organ evaluates how important the incoming impulses are for a person and sends the information further to the CNS (central nervous system) or to the cerebral cortex. This painstaking and vital process occurs thanks to the components of the thalamus - 120 multifunctional nuclei that are responsible for receiving signals, impulses and sending processed information to the appropriate one.

Thanks to its complex structure, the “visual thalamus” is capable of not only receiving and processing signals, but also analyzing them.

Ready information about the state of the body and its problems reaches the cerebral cortex, which, in turn, develops a strategy for solving and eliminating the problem, a strategy for further actions and behavior.

Structure

The thalamus is a paired ovoid formation consisting of nerve cells that are united into nuclei, thanks to which the perception and processing of signals and impulses coming from different sense organs occurs. The thalamus occupies the bulk of the diencephalon (approximately 80%). Consists of 120 multifunctional gray matter nuclei. It is shaped like a small chicken egg.

Based on the structure and location of individual parts, the thalamic brain can be divided into: metathalamus, epithalamus and subthalamus.

Metathalamus(subcortical auditory and visual center) - consists of medial and lateral geniculate bodies. The auditory lemniscus ends in the nucleus of the medial geniculate body, and the visual tracts end in the lateral geniculate nucleus.

The medial geniculate bodies constitute the auditory center. In the medial part of the metathalamus, from the subcortical auditory center, cell axons are directed to the cortical end of the auditory analyzer (superior temporal gyrus). Dysfunction of this part of the metathalamus can lead to hearing loss or deafness.

Lateral geniculate bodies constitute the subcortical visual center. This is where the optic tracts end. The axons of the cells form the optic radiation, along which visual impulses reach the cortical end of the visual analyzer (occipital lobe). Dysfunction of this center can lead to vision problems, and severe damage can lead to blindness.

Epithalamus(suprathalamus) - the upper posterior part of the thalamus, which rises above it: includes the pineal gland, which is the supracerebral endocrine gland (pineal gland). The pineal gland is in a suspended state, as it is located on leashes. It is responsible for the production of hormones: during the day it produces the hormone serotonin (the hormone of joy), and at night it produces melatonin (a regulator of the daily routine and the hormone responsible for the color of the skin and eyes). The epithalamus plays a role in the regulation of life cycles, regulates the onset of puberty, sleep and wakefulness patterns, and inhibits the aging process.

Lesions of the epithalamus lead to disruption of life cycles, including insomnia, as well as sexual dysfunction.

Subthalamus(subthalamus) or prethalamus is a small-volume brain substance. It consists mainly of the subthalamic nucleus and has connections with the globus pallidus. The subthalamus controls muscle responses and is responsible for action selection. Damage to the subthalamus leads to motor disturbances, tremors, and paralysis.

In addition to all of the above, the thalamus has connections with the spinal cord, with the hypothalamus, subcortical nuclei and, naturally, with the cerebral cortex.

Each department of this unique organ has a specific function and is responsible for vital processes, without which the normal functioning of the body is impossible.

Functions of the thalamus

The “sensitivity collector” receives, filters, processes, integrates and sends information to the brain that comes from all receptors (except smell). We can say that in its centers the formation of perception, sensation, and understanding occurs, after which the processed information or signal enters the cerebral cortex.

The main functions of the body are:

• processing of information received from all organs (receptors of vision, hearing, taste and touch) senses (except smell);
• managing emotional reactions;
• regulation of involuntary motor activity and muscle tone;
• maintaining a certain level of activity and excitability of the brain, which is necessary for the perception of information, signals, impulses and irritations coming from the outside, from the environment;
• responsible for the intensity and feeling of pain.

As we have already said, each lobe of the thalamus consists of 120 nuclei, which, based on functionality, can be divided into 4 main groups:

• lateral (lateral);
• medial (middle);
• associative.

Reticular group of nuclei (responsible for balance) – responsible for ensuring balance when walking and balance in the body.

The lateral group (vision center) is responsible for visual perception, receives and transmits impulses to the parietal, occipital part of the cerebral cortex - the visual zone.

The medial group (hearing center) is responsible for auditory perception, receives and transmits impulses to the temporal part of the cortex - the auditory zone.

Associative group (tactile sensations) - receives and transmits tactile information to the cerebral cortex, that is, signals emanating from receptors of the skin and mucous membranes: pain, itching, shock, touch, irritation, etc.

Also, from a functional point of view, nuclei can be divided into: specific and nonspecific.

Specific nuclei receive signals from all receptors (except smell). They provide a person’s emotional reaction and are responsible for the occurrence of pain.

Specific kernels, in turn, are:

• external - receive impulses from the corresponding receptors and send information to specific areas of the cortex. Through these impulses feelings and sensations arise;
• internal - do not have direct connections with receptors. They receive information already processed by the relay cores. From them, impulses go to the cerebral cortex to the associative zones. Thanks to these impulses, primitive sensations arise and the relationship between sensory areas and the cerebral cortex is ensured.

Nonspecific nuclei support the general activity of the cerebral cortex, sending nonspecific impulses and stimulating brain activity. Having no direct connection with the cortex, the nonspecific nuclei of the thalamus transmit their signals to subcortical structures.

Separately about the visual thalamus

Previously, it was believed that the thalamus processed only visual impulses, and then the organ received the name - visual thalamus. Now this name is considered obsolete, since the organ processes almost the entire range of afferent systems (except for smell).

The system that provides visual perception is one of the most interesting. The main external organ of vision is the eye, a receptor that has a retina and is equipped with special cells (cones, rods) that transform the light beam and electrical signal. The electrical signal, in turn, passing through the nerve cells enters the lateral center of the thalamus, which sends the processed signal to the central part of the cerebral cortex. Here the final analysis of the signal occurs, thanks to which what is seen is formed, that is, the picture.

What are the dangers of dysfunction of the thalamic zones?

The thalamus has a complex and well-established structure, therefore, if malfunctions or problems arise in the work of even a single zone of the organ, this leads to various consequences, affecting individual functions of the body and even the entire body as a whole.

Before reaching the corresponding center of the cortex, signals from the receptors enter the thalamus, or more precisely, to a certain part of it. If certain nuclei of the thalamus are damaged, then the impulse is not processed, does not reach the cortex, or arrives in an unprocessed form, therefore, the cerebral cortex and the entire body do not receive the necessary information.

Clinical manifestations of thalamic dysfunction depend on the specific affected area and can manifest themselves as: problems with memory, attention, understanding, loss of orientation in space and time, disorders of the motor system, problems with vision, hearing, insomnia, and mental disorders.

One of the manifestations of organ dysfunction may be specific amnesia, which leads to partial memory loss. In this case, the person forgets the events that occurred after damage or injury to the corresponding area of ​​the organ.

Another rare disorder affecting the thalamus is fatal insomnia, which can affect several members of the same family. The disease occurs due to a mutation in the corresponding zone of the thalamus, which is responsible for regulating the processes of sleep and wakefulness. Due to mutation, there is a failure in proper operation the corresponding area, and the person stops sleeping.

The thalamus is also the center of pain sensitivity. When the corresponding nuclei of the thalamus are damaged, unbearable pain occurs or, conversely, complete loss of sensitivity.

The thalamus, and the brain as a whole, continue to remain incompletely studied structures. And further research promises great scientific discoveries and help in understanding this vital and complex organ.

One of important entities The central nervous system involved in sensory functions is the thalamus. He is a kind of collector of sensory pathways. Almost all pathways enter here (with the exception of some of the scent pathways). The thalamus has more than 40 nuclei, most of which receive afferentation from various sensory pathways. There is a wide network of contacts between the neurons of the thalamus, which ensures both the processing of information from individual specific sensory systems and intersystem integration. In the thalamus, subcortical processing of ascending afferent signals is completed. Here, a partial assessment of its significance for the body occurs, due to which only part of the information is sent to the cerebral cortex. Most of the afferentation from the internal organs reaches only the thalamus. Although the neocortex contains a visceral zone in which so-called evoked potentials (EPs) are observed upon stimulation of any internal organ, a conscious sensation about the state of our internal organs does not arise in it. Afferentation from the soma does not always reach the cerebral cortex. Thanks to this, the cerebral cortex seems to be freed from evaluating less significant information and gets the opportunity to deal with significant issues of organizing human behavior. In assessing the significance of afferentation that entered the thalamus, a large role is given to the integration of information from various sensory systems, as well as those parts of the brain that are responsible for motivation, memory, etc.
The nuclear structures of the thalamus can be divided according to functional characteristics into 4 large groups.
1. Specific switching cores (relay). These nuclei receive afferents from the main sensory systems - somatosensory, visual and auditory - and switch them to the corresponding areas of the cerebral cortex.
2. Nonspecific nuclei receive afferents from all sensory organs, as well as from the reticular formation of the brain stem and hypothalamus. From here impulses are sent to all areas of the cerebral cortex (both in the sensory departments and in its other parts), as well as to the limbic system. These formations of the thalamus perform functions similar to the reticular formation of the brain.
3. Nuclei with associative functions (phylogenetically young) receive afferentation from the nuclei of the thalamus proper and carry out the above-mentioned specific and nonspecific functions. After analysis, information from these nuclei enters those parts of the cerebral cortex that perform associative functions. These departments are localized in the parietal, temporal and frontal lobes. In humans they are more developed than in animals. Thus, the thalamus is involved in the integration of these areas, which are sometimes located one far from each other.
4. Nuclei that are associated with the motor areas of the cerebral cortex, non-sensory relay. Receive afferentation from the cerebellum, basal ganglia the forebrain and are transmitted to the motor zones of the cerebral cortex, that is, to those departments that are involved in the formation of conscious movements.
In the thalamus, due to the interaction of sensory systems, a significant part of the information is inhibited, which from here does not enter the higher cortical sections of the sensory systems. It must be said that connections between the thalamus and the cerebral cortex are not one-sided. The cerebral cortex supplies descending efferent impulses various parts thalamus. In this way, the processing of information that enters the thalamus is regulated. Due to the strong inhibitory system of the thalamus itself and the descending influences of the cerebral cortex, a kind of “free corridor” is formed for the passage of only the most important signals in the cerebral cortex.

Diencephalon located under the corpus callosum and fornix, fused on the sides with the cerebral hemispheres.

This includes:

Thalamus (visual thalamus),

Epithalamus (supratubercular region),

Metathalamus (foreign region) and

Hypothalamus (subcutaneous region).

The cavity of the diencephalon is the third ventricle.

Thalamus are paired accumulations of gray matter, covered with a layer of white matter, having an ovoid shape.

There are three main groups of nuclei in the thalamus: anterior, lateral and medial. In the lateral nuclei, all sensory pathways heading to the cerebral cortex are switched.

IN epithalamus lies the upper appendage of the brain - the epiphysis, or pineal body, suspended on two leashes in the recess between the upper colliculi of the roof plate.

Metathalamus represented by the medial and lateral geniculate bodies. They are connected by bundles of fibers (handles of the mounds) to the upper and lower mounds of the roof plate. They contain nuclei that are reflex centers of vision and hearing.

Hypothalamus is located ventral to the thalamus opticus and includes the subtubercular region itself and a number of formations located at the base of the brain.

Third ventricle located in the midline and is a narrow vertical slit.

The main formations of the diencephalon are the thalamus (visual thalamus) and hypothalamus (subthalamic region).

Thalamus - sensitive nucleus of the subcortex. It is called the “collector of sensitivity”, since afferent (sensitive) pathways from all receptors converge to it, excluding olfactory receptors. Here is the third neuron of the afferent pathways, the processes of which end in the sensitive areas of the cortex.

The main function of the thalamus is the integration (unification) of all types of sensitivity. To analyze the external environment, there are not enough signals from individual receptors. Here the information received through various communication channels is compared and evaluated biological significance. In the visual thalamus, there are 40 pairs of nuclei, which are divided into specific (the ascending afferent pathways end on the neurons of these nuclei), nonspecific (nuclei of the reticular formation) and associative. Through the associative nuclei, the thalamus is connected with all the motor nuclei of the subcortex - the striatum, globus pallidus, hypothalamus and with the nuclei of the midbrain and medulla oblongata.

The study of the functions of the visual thalamus is carried out by cutting, irritation and destruction. A cat in which the incision is made above the diencephalon is very different from a cat in which the highest part of the central nervous system is the midbrain. She not only gets up and walks, that is, performs complexly coordinated movements, but also shows all the signs of emotional reactions. A light touch triggers an angry reaction. The cat beats its tail, bares its teeth, growls, bites, and extends its claws.

In humans, the visual thalamus plays a significant role in emotional behavior, characterized by peculiar facial expressions, gestures and shifts in the functions of internal organs. During emotional reactions, blood pressure rises, pulse and breathing quicken, and pupils dilate.

The facial reaction of a person is innate. If you tickle the nose of a fetus 5-6 months old, you can see a typical grimace of displeasure (P.K. Anokhin). When the optic thalamus is irritated, animals experience motor and pain reactions - squealing, grumbling. The effect can be explained by the fact that impulses from the visual thalamus easily transfer to the associated motor nuclei of the subcortex.

In the clinic, symptoms of damage to the visual thalamus are severe headache, sleep disturbances, sensitivity disturbances, both upward and downward, disturbances in movements, their accuracy, proportionality, and the occurrence of violent involuntary movements.

Hypothalamus is the highest subcortical center of the autonomic nervous system. In this area there are centers that regulate all vegetative functions, ensuring the constancy of the internal environment of the body, as well as regulating fat, protein, carbohydrate and water-salt metabolism.

In the activity of the autonomic nervous system, the hypothalamus plays the same important role as the red nuclei of the midbrain play in the regulation of skeletal-motor functions of the somatic nervous system.

The earliest studies of the functions of the hypothalamus belong to Claude Bernard. He discovered that an injection into the diencephalon of a rabbit caused an increase in body temperature of almost 3°C. This classic experiment, which discovered the localization of the thermoregulation center in the hypothalamus, was called heat injection. After the destruction of the hypothalamus, the animal becomes poikilothermic, that is, it loses the ability to maintain a constant body temperature. In a cold room, body temperature decreases, and in a hot room it increases.

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

Currently, the method of implanting electrodes is widely used to stimulate various brain structures. Using a special, so-called stereotactic technique, electrodes are inserted into any given area of ​​the brain through a burr hole in the skull. The electrodes are insulated throughout, only their tip is free. By connecting electrodes in a circuit, you can locally irritate certain areas.

When the anterior parts of the hypothalamus are irritated, parasympathetic effects occur - increased intestinal movements, separation of digestive juices, slowing down heart contractions, etc.

When the posterior sections are irritated, sympathetic effects are observed - increased heart rate, constriction of blood vessels, increased body temperature, etc. Consequently, parasympathetic centers are located in the anterior sections of the subthalamic region, and sympathetic centers in the posterior sections.

Since stimulation with the help of implanted electrodes is carried out on the animal, without the use of anesthesia, it becomes possible to judge the behavior of the animal. In Andersen's experiments on a goat with implanted electrodes, a center was found whose irritation causes unquenchable thirst - the thirst center. When irritated, the goat could drink up to 10 liters of water. By irritating 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 with an electrode implanted into the “center of fear” became widely known. When an angry bull rushed at a bullfighter in the arena, irritation was turned on, and the bull retreated with clearly expressed signs of fear.

American researcher D. Olds proposed modifying the method - allowing the animal to close the electrodes itself, assuming that the animal would avoid unpleasant stimuli and, conversely, strive to repeat pleasant ones.

Experiments have shown that there are structures whose irritation causes an uncontrollable desire to repeat. The rats worked themselves into exhaustion by pressing the lever up to 14,000 times! In addition, structures were discovered whose irritation apparently causes an extremely unpleasant sensation, since the rat for the second time avoids pressing the lever again and runs away from it. The first center is obviously the center of pleasure, and 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 receptors facing the blood, reflexes arise aimed at maintaining the constancy of the internal environment of the body - homeostasis. “Hungry blood”, irritating gluco-receptors, excites the food center: food reactions arise, aimed at searching and eating food.

One of the common manifestations of hypothalamic disease in the clinic is a violation of water-salt metabolism, manifested in the secretion large quantity urine with low density. The disease is called diabetes insipidus or diabetes insipidus.

Podbugorny region closely related to the activity of the pituitary gland. The hormones vasopressin and oxytocin are produced in large neurons of the supra-visual and periventricular nuclei of the pituitary gland. Hormones flow along the axons to the pituitary gland, where they accumulate and then enter the blood.

A different relationship between the hypothalamus and the anterior pituitary gland. The vessels surrounding the nuclei of the hypothalamus unite into a system of veins, which descend to the anterior lobe of the pituitary gland and here break up into capillaries. With the blood, substances enter the pituitary gland - releasing factors, or releasing factors, which stimulate the formation of hormones in its anterior lobe.

Pituitary closely connected with the hypothalamus structurally and functionally. The posterior parts of the pituitary gland (neurohypophysis) accumulate hormones produced by the hypothalamus and regulating water-salt balance, controlling the functions of the uterus and mammary glands.

The anterior parts of the pituitary gland (adenohypophysis) produce:

adrenocorticotropic hormone - ACTH, which stimulates the adrenal glands;

thyroid-stimulating hormone - stimulates the growth and secretion of the thyroid gland;

gonadotropic hormone - regulates the activity of the sex glands;

somatotropic hormone - ensures the development of the skeletal system; prolactin - stimulates the growth and activity of the mammary glands, etc.

Neuroregulatory enkephalins and endorphins, which have a morphine-like effect and help reduce stress, are also formed in the hypothalamus and pituitary gland.