Responsible for the mechanisms of wakefulness and sleep, changes in body temperature and metabolic processes in the body. The performance of all organs and tissues of the body depends on it. Human emotional reactions are also under the control of the hypothalamus. In addition, the hypothalamus controls the work of the endocrine glands, participates in the digestion process, as well as in procreation. The hypothalamus is located in the brain under the visual thalamus - the thalamus. Therefore, hypothalamus, translated from Latin means “ hypothalamus».
- The hypothalamus is the size of the phalanx of the thumb.
- Scientists have found centers of “heaven” and “hell” in the hypothalamus. These areas of the brain are responsible for pleasant and unpleasant sensations in the body.
- The division of people into “larks” and “night owls” is also within the competence of the hypothalamus.
- Scientists call the hypothalamus the “inner sun of the body” and believe that further study of its capabilities can lead to an increase in human life expectancy, to victory over many endocrine diseases, as well as to further exploration of space, thanks to a controlled lethargic sleep into which astronauts can be immersed, covering distances of tens and hundreds of light years.
Healthy foods for the hypothalamus
- Raisins, dried apricots, honey - contain glucose necessary for the full functioning of the hypothalamus.
- Greens and leafy vegetables. Lovely and potassium. They are excellent antioxidants. Protect the hypothalamus from the risk of hemorrhage and stroke.
- Milk and dairy products. They contain B vitamins, which are necessary for the proper functioning of the nervous system, as well as calcium and other nutrients.
- Eggs . They reduce the risk of stroke due to the content of substances that are beneficial for the brain.
- Coffee, dark chocolate. In small quantities they tone up the hypothalamus.
- Bananas, tomatoes, oranges. They lift your spirits. They facilitate the work of not only the hypothalamus, but also all structures of the brain. Useful for the nervous system, the activity of which is closely related to the work of the hypothalamus.
- Walnuts . Stimulates the performance of the hypothalamus. Slow down the aging process of the brain. Rich in healthy fats, vitamins and microelements.
- Carrot . Slows down the aging process in the body, stimulates the formation of young cells, and participates in the conduction of nerve impulses.
- Sea kale. Contains substances necessary to provide the hypothalamus with oxygen. The large amount of iodine contained in seaweed helps fight insomnia and irritability, fatigue and stress.
- Fatty fish and vegetable oils. They contain polyunsaturated fatty acids, which are important components of the nutrition of the hypothalamus. They prevent cholesterol deposition and stimulate hormone production.
For the full functioning of the hypothalamus, you need:
- Therapeutic exercise and daily walks in the fresh air (especially in the evening, before bed).
- Regular and nutritious meals. A dairy-vegetable diet is preferable. Doctors advise avoiding overeating.
- Following a daily routine helps the hypothalamus enter its usual rhythm of work.
- Eliminate alcoholic beverages and get rid of harmful cravings for smoking, which harm the functioning of the nervous system, with the activity of which the hypothalamus is closely connected.
- Avoid watching TV and working on the computer before bed. Otherwise, due to a violation of the light regime of the day, disruptions in the functioning of the hypothalamus and the entire nervous system may occur.
- In order to prevent overexcitation of the hypothalamus, it is recommended to wear sunglasses on a bright sunny day.
Traditional methods of restoring the functions of the hypothalamus
The causes of dysfunction of the hypothalamus are:
- 1 Infectious diseases, intoxication of the body.
- 2 Disturbances in the functioning of the nervous system.
- 3 Weak immunity.
In the first case Anti-inflammatory herbs (chamomile, calendula, St. John's wort) can be used - on the recommendation of a doctor. For intoxication, iodine-containing products are useful - chokeberry, seaweed, feijoa, walnuts.
In the second case When the functioning of the nervous system is disrupted, tonics (chicory, coffee) are used, or vice versa, sedatives - tincture of valerian, motherwort and hawthorn, pine baths.
For tachycardia and an unreasonable increase in pressure associated with improper functioning of the hypothalamus, water procedures are useful: a warm shower followed by vigorous rubbing of the skin.
For depressive conditions, a decoction of St. John's wort herb helps well, of course, if there are no medical contraindications for use!
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 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 focused not point to point, but on many different neurons, which ensures its complete analysis and the possibility of transmission 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 multiple 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 leads to 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 microns 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 the left side of 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 tends to result in poor performance 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 deleted 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 accurately assessing individual image elements. 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.
The hypothalamus is part of the diencephalon and is part of the limbic system. This is a complexly organized part of the brain that performs a number of vegetative functions, is responsible for the humoral and neurosecretory supply of the body, emotional behavioral reactions and other functions.
Morphologically, about 50 pairs of nuclei are distinguished in the hypothalamus, divided topographically into 5 large groups: 1) preoptic group or region, which includes: periventricular, preoptic nucleus, medial and lateral preoptic nuclei, 2) anterior group: supraoptic, paraventricular and suprachiasmatic nuclei, 3) middle group: ventromedial and dorsomedial nuclei, 4) outer group: lateral hypothalamic nucleus, nucleus of the gray tuberosity, 5) posterior group: posterior hypothalamic nucleus, perifornical nucleus, medial and lateral nuclei of the mammillary bodies.
Neurons of the hypothalamus have a special sensitivity to the composition of the blood washing them: changes in pH, pCO 2 pO 2 content of catecholamines, potassium and sodium ions. The supraoptic nucleus contains osmoreceptors. The hypothalamus is the only brain structure that lacks the blood-brain barrier. Neurons of the hypothalamus are capable of neurosecretion of peptides, hormones, and mediators.
Neurons sensitive to adrenaline were identified in the posterior and lateral hypothalamus. Adrenoreceptive neurons can be located in the same nucleus of the hypothalamus along with cholinoreceptive and serotonin receptor neurons. The injection of epinephrine or norepinephrine into the lateral hypothalamus causes a food reaction, and the injection of acetylcholine or carbocholine causes a drinking reaction. Neurons of the ventromedial and lateral nuclei of the hypothalamus exhibit high sensitivity to glucose due to the presence of “glucoreceptors” in them.
Conductor function of the hypothalamus
The hypothalamus has afferent connections with the olfactory brain, basal ganglia, thalamus, hippocampus, orbital, temporal and parietal cortices.
The efferent pathways are represented by: mamillothalamic, hypothalamic-thalamic, hypothalamic-pituitary, mamillotegmental, hypothalamic-hippocampal tracts. In addition, the hypothalamus sends impulses to the autonomic centers of the brain stem and spinal cord. The hypothalamus has close connections with the reticular formation of the brain stem, which determines the course of the body’s autonomic reactions, its eating and emotional behavior.
Own functions of the hypothalamus
The hypothalamus is the main subcortical center that regulates autonomic functions. Irritation of the anterior group of nuclei imitates the effects of the parasympathetic nervous system, its trophotropic effect on the body: constriction of the pupil, bradycardia, decreased blood pressure, increased secretion and motility of the gastrointestinal tract. The supraoptic and paraventricular nuclei are involved in the regulation of water and salt metabolism due to the production of antidiuretic hormone.
Stimulation of the posterior group of nuclei has ergotropic effects, activates sympathetic effects: pupil dilation, tachycardia, increased blood pressure, inhibition of motility and secretion of the gastrointestinal tract.
The hypothalamus provides mechanisms for thermoregulation. Thus, the nuclei of the anterior group of nuclei contain neurons responsible for heat transfer, and the posterior group - for the process of heat production. The nuclei of the middle group are involved in the regulation of metabolism and eating behavior. The saturation center is located in the ventromedial nuclei, and the hunger center is located in the lateral nuclei. Destruction of the ventromedial nucleus leads to hyperphagia - increased food consumption and obesity, and destruction of the lateral nuclei - to complete refusal of food. The center of thirst is located in the same core. The hypothalamus contains centers for protein, carbohydrate and fat metabolism, centers for the regulation of urination and sexual behavior (suprachiasmatic nucleus), fear, rage, and the sleep-wake cycle.
The regulation of many body functions by the hypothalamus is carried out through the production of pituitary hormones and peptide hormones: Liberins, stimulating the release of hormones from the anterior pituitary gland, and statins - hormones that inhibit their release. These peptide hormones (thyrotropin-releasing hormone, corticotropin-releasing hormone, somatostatin, etc.) reach its anterior lobe through the portal vascular system of the pituitary gland and cause a change in the production of the corresponding hormone of the adenohypophysis.
The supraoptic and paraventricular nuclei, in addition to their participation in water-salt metabolism, lactation, and uterine contractions, produce hormones of a polypeptide nature - oxytocin And antidiuretic hormone (vasopressin), which, with the help of axonal transport, reach the neurohypophysis and, accumulating in it, have a corresponding effect on the reabsorption of water in the renal tubules, on vascular tone, and on the contraction of the pregnant uterus.
The suprachiasmatic nucleus is related to the regulation of sexual behavior, and pathological processes in the region of this nucleus lead to accelerated puberty and menstrual irregularities. This same nucleus is the central driver of the circadian (circadian) rhythms of many functions in the body.
The hypothalamus is directly related, as noted above, to the regulation of the sleep-wake cycle. In this case, the posterior hypothalamus stimulates wakefulness, the anterior hypothalamus stimulates sleep, and damage to the posterior hypothalamus can cause pathological Sopor.
The hypothalamus and pituitary gland produce neuropeptides related to the antinoticeptive (pain-relieving) system, or opiates: enkephalins And endorphins.
The hypothalamus is part of the limbic system, which is involved in emotional behavior.
D. Olds, implanting electrodes into some nuclei of the rat's hypothalamus, observed that when some nuclei were stimulated, a negative reaction occurred, while others were positive: the rat did not move away from the pedal that closed the stimulating current, and pressed it until exhaustion (experiment with self-irritation). It is possible to assume
live that it irritated the “pleasure centers.” Irritation of the anterior hypothalamus provoked a picture of rage, fear, and a passive defensive reaction, and the posterior hypothalamus provoked active aggression and an attack reaction.
“Endocrine brain” is what anatomists call the hypothalamus (from the Greek “hypo” - under, “thalamus” - room, bedroom). It is located in the human brain, but is very closely connected with the pituitary gland, the most important organ of the human endocrine system. Despite its small size, the hypothalamus has a very complex structure and performs both autonomic and endocrine functions in our body.
What is the hypothalamus?
The hypothalamus is located at the very base of the brain - the intermediate section, forming the walls and base of the lower part of the third cerebral ventricle. This is a small area that is located directly below the thalamus, in the subcutaneous zone. Hence the second name of the hypothalamus - hypothalamus.
Anatomically, the hypothalamus is a full-fledged part of the central nervous system and is connected by nerve fibers to its main structures - the cortex and brain stem, cerebellum, spinal cord, etc. On the other hand, the hypothalamus directly controls the work of the pituitary gland and, in conjunction with it, makes up the hypothalamic-pituitary system. It is also called neuroendocrine - the system performs both the central nervous system (for example, metabolism) and endocrine functions (the pituitary gland produces hormones, and the centers of the hypothalamus control these processes).
The most important role of the hypothalamus in the functioning of the entire body does not allow scientists to unambiguously classify it as any system of the body. It is supposedly located at the junction of two systems, the endocrine and the central nervous system, being the connecting link between them.
The hypothalamic groove separates the hypothalamus from the thalamus; this is the upper border of the organ. In front, it is limited by a terminal plate of gray matter, which serves as a kind of layer between the hypothalamus and the optic chiasm.
The lateral borders of the hypothalamus are the optic tracts. And the lower part of the hypothalamus, or the bottom of the lower ventricle, is called the gray tubercle. It passes into the funnel, which in turn extends into the pituitary stalk. The pituitary gland hangs on it.
The hypothalamus weighs very little - about 3-5 grams; scientists are still arguing about its size. Some researchers compare it in volume to an almond nut, others believe that it can reach the length of the phalanx of a person’s thumb. The hypothalamus has a streamlined, slightly elongated shape. Many cells of the hypothalamus are thoroughly “soldered” into neighboring areas of the brain, so a clear description of the hypothalamus does not exist today.
But if the true size and appearance of this part of the brain is still not precisely known, the structure of the hypothalamus has been studied for a very long time.
The hypothalamus is divided into several areas in which special clusters of neurons are collected - the nuclei of the hypothalamus. Each group of nuclei performs its own special functions. Most of these nuclei are paired and located on either side of the third ventricle, where the organ itself is located. The exact number of these nuclei in the human hypothalamus is unknown; different data on this issue can be found in the medical literature. Scientists agree on one thing - the number of nuclei fluctuates in the range of 32-48.
There are several classifications that describe the structure of the hypothalamus. One of the most popular is the typology of Soviet anatomists L.Ya. Pines and R.M. Maiman. According to them, the hypothalamus consists of three parts:
- anterior section (includes neurosecretory cells);
- middle section (area of the gray tubercle and funnel);
- lower section (mastoid bodies).
According to a number of scientists, the anterior hypothalamus consists of 2 zones, preoptic and anterior. Some experts share these areas. The anterior hypothalamus includes the suprachiasmatic, supraoptic (supraoptic), paraventricular (periventricular) nuclei.
The middle section of the hypothalamus consists of the gray tubercle - a thin plate of gray matter of the brain. Externally, the tubercle looks like a hollow protrusion of the lower wall of the third ventricle. The top of this tubercle is elongated into a narrow funnel, which connects to the pituitary gland. The following nuclei are concentrated in this area: tuberal (grey tuberous), ventromedial and dorsomedial, pallido-infundibular, mammilo-infundibular.
The mammillary bodies are part of the posterior hypothalamus. They are two hilly formations of white matter, with 2 gray nuclei hidden inside. In the posterior region of the hypothalamus there are the following groups of nuclei: mammillary-infundibular, nuclei of mammillary (mastoid) bodies, supra-mammillary. The largest nucleus in this zone is the medial mastoid body.
The hypothalamus is one of the oldest parts of the brain; scientists find it even in lower vertebrates. And in many fish, the hypothalamus is generally the most developed part of the brain. In humans, the development of the hypothalamus begins in the first weeks of embryonic development, and by the birth of the baby this organ is already fully formed.
Or the subthalamic region, is a small area located below the thalamic region in the diencephalon. Despite their small size, hypothalamic neurons form from 30 to 50 groups of nuclei responsible for all kinds of homeostatic indicators of the body, as well as regulating most neuroendocrine functions of the brain and the body as a whole. Hypothalamic neurons have extensive connections with almost all centers and departments of the central nervous system, while the neuroendocrine connections of the hypothalamus and pituitary gland deserve special attention. They determine the formation of the so-called functionally unified hypothalamic-pituitary system, which is responsible for the production of pituitary and hypothalamic hormones and is the central link between the nervous and endocrine systems. Let's take a closer look at how the hypothalamus works, what it is, and what specific body functions are provided by this small area of the brain.
Anatomical features
Although the functional activity of the hypothalamus has been studied quite well, today there are no sufficiently clear anatomical boundaries defining the hypothalamus. The structure from the point of view of anatomy and histology is associated with the formation of extensive neuronal connections of the hypothalamic region with other parts of the brain. Thus, the hypothalamus is located in the subthalamic region (below the thalamus, which is where its name comes from) and takes part in the formation of the walls and floor of the third ventricle of the brain. The lamina terminalis anatomically forms the anterior border of the hypothalamus, and its posterior border is formed by a hypothetical line running from the posterior commissure of the brain to the caudal mammillary bodies.
Despite its small size, the hypothalamic region is structurally divided into several smaller anatomical and functional areas. In the lower part of the hypothalamus, structures such as the gray tubercle, the infundibulum and the median eminence are distinguished, and the lower part of the infundibulum often passes anatomically into the pituitary stalk.
Hypothalamic nuclei
Let's look at which nuclei are included in the hypothalamus, what they are, and what groups they are divided into. So, by nuclei in the central nervous system we mean the accumulation of gray matter (neuron bodies) in the thickness of white matter (axon and dendritic terminals - pathways). Functionally, the nuclei ensure the switching of nerve fibers from one nerve cell to another, as well as the analysis, processing and synthesis of information.
Anatomically, there are three groups of clusters of neuron bodies that form the nuclei of the hypothalamus: anterior, middle and posterior groups. Today, it is quite difficult to establish the exact number of hypothalamic nuclei, since various domestic and foreign literary sources provide different data regarding their number. The anterior group of nuclei is located in the area of the optic chiasm, the middle group lies in the area of the gray tuberosity, and the back group in the area of the mastoid bodies, forming the same-named sections of the hypothalamus.
The anterior group of hypothalamic nuclei includes the supraoptic and paraventricular nuclei, the middle group of nuclei, corresponding to the area of the infundibulum and gray tuberosity, includes the lateral nuclei, as well as the dorsomedial, tuberal and ventromedial nuclei, and the posterior group includes the mammillary bodies and posterior nuclei. In turn, the autonomic function of the hypothalamus is ensured through the function of nuclear structures, anatomical and functional relationships with the rest of the brain, control of basic behavioral reactions and the release of hormones.
Hypothalamic hormones
The hypothalamic region secretes highly specific and biologically active substances, which are called “hypothalamic hormones.” The word “hormone” comes from the Greek “I excite,” i.e. hormones are highly active biological compounds that, in nanomolar concentrations, can lead to significant physiological changes in the body. Let's look at what hormones the hypothalamus secretes, what they are and what their regulatory role is in the functional activity of the whole organism.
According to their functional activity and point of application, hypothalamic hormones are divided into the following groups:
- releasing hormones, or liberins;
- statins;
- hormones of the posterior lobe of the pituitary gland (vasopressin or antidiuretic hormone and oxytocin).
Functionally, releasing hormones influence the activity and release of hormones by the cells of the anterior pituitary gland, increasing their production. Statin hormones perform the exact opposite function, stopping the production of biologically active substances. Posterior pituitary hormones are actually produced in the supraoptic and paraventricular nuclei of the hypothalamus and are then transported via axon terminals to the posterior pituitary. Thus, the hormones of the hypothalamus are a kind of control elements that regulate the production of other hormones. Liberins and statins regulate the production of pituitary tropic hormones, which, in turn, affect target organs. Let's look at the main functional aspects of the hypothalamic region, or what the hypothalamus is responsible for in the body.
Hypothalamus in regulation of cardiovascular system function
To date, it has been experimentally shown that electrical stimulation of various hypothalamic areas can lead to any of the known neurogenic effects on the cardiovascular system. In particular, by stimulating the centers of the hypothalamus, it is possible to achieve an increase or decrease in blood pressure, an increase or decrease in heart rate. It has been shown that in various areas of the hypothalamus these functions are organized in a reciprocal manner (that is, there are centers responsible for increasing blood pressure and centers responsible for reducing it): stimulation of the lateral and posterior hypothalamic region leads to an increase in blood pressure and frequency. heart contractions, while stimulation of the hypothalamus in the area of the optic chiasm can cause exactly the opposite effects. The anatomical basis for regulatory influences of this type are specific centers that regulate the activity of the cardiovascular system, located in the reticular areas of the pons and medulla oblongata, and extensive neural connections passing from them to the hypothalamus. The regulatory functions are precisely ensured through the close exchange of information between these areas of the brain.
Participation of the hypothalamic region in maintaining a constant body temperature
Nuclear formations of the hypothalamic region are directly involved in the regulation and maintenance of constant body temperature. The preoptic area contains a group of neurons that are responsible for constant monitoring of blood temperature.
When the temperature of flowing blood increases, this group of neurons is able to increase impulses, transmitting information to other structures of the brain, thereby triggering heat transfer mechanisms. When the blood temperature decreases, the impulse from neurons decreases, which causes the launch of heat production processes.
Participation of the hypothalamus in the regulation of water balance in the body
The body's water-salt balance, vasopressin, hypothalamus - what is it? The answer to these questions is given later in this section. Hypothalamic regulation of the body's water balance is carried out in two main ways. The first of them is the formation of a feeling of thirst and a motivational component, which includes behavioral mechanisms leading to the satisfaction of the arisen need. The second way is to regulate the loss of fluid from the body through urine.
The thirst center, which determines the formation of the feeling of the same name, is localized in the lateral hypothalamic region. At the same time, sensitive neurons in this area constantly monitor not only the level of electrolytes in the blood plasma, but also osmotic pressure, and with increasing concentrations they cause the formation of a feeling of thirst, which leads to the formation of behavioral reactions aimed at searching for water. After water is found and thirst is satisfied, the osmotic pressure of the blood and electrolyte composition are normalized, which returns the firing of neurons to normal. Thus, the role of the hypothalamus is reduced to the formation of the autonomic basis of behavioral mechanisms aimed at satisfying emerging nutritional needs.
The regulation of the loss or excretion of water by the body through the kidneys lies with the so-called supraoptic and paraventricular nuclei of the hypothalamus, which are responsible for the production of a hormone called vasopressin, or antidiuretic hormone. As the name suggests, this hormone regulates the amount of water reabsorbed in the collecting ducts of the nephrons. In this case, the synthesis of vasopressin is carried out in the above-mentioned nuclei of the hypothalamus, and then it is transported through axon terminals to the posterior part of the pituitary gland, where it is stored until the required moment. If necessary, the posterior lobe of the pituitary gland releases this hormone into the blood, which increases the reabsorption of water in the renal tubules and leads to an increase in the concentration of urine excreted and a decrease in the level of electrolytes in the blood.
Participation of the hypothalamus in the regulation of contractile activity of the uterus
Neurons of the paraventricular nuclei produce a hormone such as oxytocin. This hormone is responsible for the contractility of the muscle fibers of the uterus during childbirth, and in the postpartum period - for the contractility of the milk ducts of the mammary glands. Towards the end of pregnancy, closer to childbirth, an increase in specific receptors for oxytocin occurs on the surface of the myometrium, which increases the sensitivity of the latter to the hormone. At the time of birth, a high concentration of oxytocin and the sensitivity of the uterine muscle fibers to it contribute to the normal course of labor. After birth, when the baby takes the nipple, this leads to stimulation of oxytocin production, which causes the milk ducts of the mammary glands to contract and milk to be released.
In addition, in the absence of pregnancy and breastfeeding, as well as in males, this hormone is responsible for the formation of feelings of love and sympathy, for which it received its second name - “love hormone” or “happiness hormone”.
Participation of the hypothalamus in the formation of feelings of hunger and satiety
In the lateral hypothalamic region there are specific centers, organized in a reciprocal manner, responsible for the formation of feelings of thirst and satiety. It was experimentally shown that electrical stimulation of the centers responsible for the formation of the feeling of hunger leads to the appearance of a behavioral reaction of seeking and eating food even in a well-fed animal, and stimulation of the satiety center leads to the refusal of food in an animal that has been starving for several days.
With damage to the lateral hypothalamic region and the centers responsible for the formation of feelings of hunger, so-called starvation may occur, which leads to death, and with pathology and bilateral damage to the ventromedial region, an insatiable appetite and lack of satiety occurs, which leads to the formation of obesity.
The hypothalamus in the mammillary body region also takes part in the formation of behavioral reactions related to food. Irritation of this area leads to reactions such as lip licking and swallowing.
Regulation of behavioral activity
Despite its small size, only a few cubic centimeters, the hypothalamus takes part in the regulation of behavioral activity and emotional behavior, being part of the limbic system. At the same time, the hypothalamus has extensive functional connections with the brain stem and the reticular formation of the midbrain, with the anterior thalamic region and limbic parts of the cerebral cortex, the infundibulum of the hypothalamus and pituitary gland for the implementation and coordination of the secretory and endocrine functions of the latter.
Hypothalamic diseases
Pathogenetically, all diseases of the hypothalamus are divided into three large groups, depending on the characteristics of hormone production. Thus, there are diseases associated with increased hormonal production of the hypothalamus, with decreased hormonal production, as well as with normal levels of hormone production. In addition, diseases of the hypothalamus and pituitary gland are very closely related to each other, which is due to the common blood supply, anatomical structure and functional activity. Often, pathologies of the hypothalamus and pituitary gland are combined into a general group of diseases of the hypothalamic-pituitary system.
The most common cause leading to the appearance of clinical symptoms is the occurrence of an adenoma - a benign tumor from the glandular tissue of the pituitary gland. Moreover, as a rule, its occurrence is accompanied by an increase in hormonal production with the corresponding typical manifestation of clinical symptoms. The most common are tumors that produce excess amounts of corticotropin (corticotropinoma), somatotropin (somatotropinoma), thyrotropin (thyrotrypinoma), etc.
Among the typical lesions of the hypothalamus, prolactinoma should be noted - a hormonally active tumor that produces prolactiin. This pathological condition is accompanied by a clinical diagnosis of hyperprolactinemia and is most characteristic of the female gender. Increased production of this hormone leads to menstrual irregularities, the appearance of disorders of the sexual sphere, cardiovascular system, etc.
Another serious disease associated with disruption of the functional activity of the hypothalamic-pituitary system is hypothalamic syndrome. This condition is characterized not only by hormonal imbalance, but also by the appearance of disorders in the vegetative sphere, disturbances in metabolic and trophic processes. Diagnosis of this condition is sometimes extremely difficult, since some symptoms are masked as symptoms of other diseases.
Conclusion
Thus, the hypothalamus, whose functions in ensuring vital functions are difficult to overestimate, is the highest integrative center responsible for controlling the autonomic functions of the body, as well as behavioral and motivational mechanisms. Being in a complex relationship with the rest of the brain, the hypothalamus takes part in the control of almost all vital constants of the body, and its defeat often leads to severe illness and death.