Thalamus. Morphofunctional organization. Functions. Functions of the thalamus and hypothalamus

Thalamus (visual thalamus)

The neurons of the thalamus form 40 nuclei. Topographically, the nuclei of the thalamus are divided into anterior, median and posterior. Functionally, these nuclei can be divided into two groups: specific and nonspecific.

Specific nuclei are part of specific pathways. These are ascending pathways that transmit information from sensory organ receptors to the projection zones of the cerebral cortex.

The most important of the specific nuclei are the lateral geniculate body, which is involved in transmitting signals from photoreceptors, and the medial geniculate body, which transmits signals from auditory receptors.

The nonspecific ribs of the thalamus are classified as the reticular formation. They act as integrative centers and have a predominantly activating ascending effect on the cerebral cortex:

1 - anterior group (olfactory); 2 - posterior group (visual); 3 - lateral group (general sensitivity); 4 - medial group (extrapyramidal system; 5 - central group (reticular formation).

Frontal section of the brain at the level of the middle of the thalamus. 1a - anterior nucleus of the visual thalamus. 16 - medial nucleus of the visual thalamus, 1c - lateral nucleus of the visual thalamus, 2 - lateral ventricle, 3 - fornix, 4 - caudate nucleus, 5 - internal capsule, 6 - external capsule, 7 - external capsule (capsula extrema), 8 - ventral nucleus of the thalamus optic, 9 - subthalamic nucleus, 10 - third ventricle, 11 - cerebral peduncle. 12 - bridge, 13 - interpeduncular fossa, 14 - hippocampal peduncle, 15 - inferior horn lateral ventricle. 16 - black substance, 17 - insula. 18 - pale ball, 19 - shell, 20 - Trout N fields; and b. 21 - interthalamic fusion, 22 - corpus callosum, 23 - tail of the caudate nucleus.

Activation of neurons in the nonspecific nuclei of the thalamus is especially effective in causing pain signals (the thalamus is the highest center of pain sensitivity).

Damage to the nonspecific nuclei of the thalamus also leads to impairment of consciousness: loss of active communication between the body and the environment.

Subthalamus (hypothalamus)

The hypothalamus is formed by a group of nuclei located at the base of the brain. The nuclei of the hypothalamus are subcortical centers of the autonomic nervous system all vital functions of the body.

Topographically, the hypothalamus is divided into the preoptic area, the areas of the anterior, middle and posterior hypothalamus.

Studepedia.org - Lectures, Manuals, and many other materials useful for studying

All nuclei of the hypothalamus are paired.

Metathalamus and hypothalamus. 1 - aqueduct 2 - red nucleus 3 - tegmentum 4 - substantia nigra 5 - cerebral peduncle 6 - mastoid bodies 7 - anterior perforated substance 8 - oblique triangle 9 - infundibulum 10 - optic chiasm 11. optic nerve 12 - gray tubercle 13 - posterior perforated substance 14 - external geniculate body 15 - medial geniculate body 16 - cushion 17 - optic tract

Subcutaneous region (hypothalamus)

a - bottom view; b - mid-sagittal section.

Visual part (pars optica): 1 - terminal plate; 2 - visual chiasm; 3 - optic tract; 4 - gray tubercle; 5 - funnel; 6 - pituitary gland;

Olfactory part: 7 - mamillary bodies - subcortical olfactory centers; 8 - the subtubercular region in the narrow sense of the word is a continuation of the cerebral peduncles, contains the substantia nigra, the red nucleus and the Lewis body, which is a link in the extrapyramidal system and vegetative center; 9 - subtubercular Monroe's groove; 10 - sella turcica, in the fossa of which the pituitary gland is located.

Main nuclei of the hypothalamus

Diagram of the neurosecretory nuclei of the subtubercular region (Hypothalamus). 1 - nucleus supraopticus; 2 - nucleus preopticus; 3 - nuclius paraventricularis; 4 - nucleus infundibularus; 5 - nucleus cogroris mamillaris; 6 - optic chiasm; 7 - pituitary gland; 8 - gray tubercle; 9 - mastoid body; 10 bridge.

The preoptic area includes the periventricular, medial and lateral preoptic nuclei.

The anterior hypothalamus group includes the supraoptic, suprachiasmatic and paraventricular nuclei.

The middle hypothalamus makes up the ventromedial and dorsomedial nuclei.

In the posterior hypothalamus, the posterior hypothalamic, perifornical and mamillary nuclei are distinguished.

The connections of the hypothalamus are extensive and complex. Afferent signals to the hypothalamus come from the cortex cerebral hemispheres, subcortical nuclei and from the thalamus. The main efferent pathways reach the midbrain, thalamus and subcortical nuclei.

The hypothalamus is the highest regulatory center of cardio-vascular system, water-salt, protein, fat, carbohydrate metabolism. This area of the brain contains centers associated with the regulation eating behavior. An important role of the hypothalamus is regulation. Electrical stimulation of the posterior nuclei of the hypothalamus leads to hyperthermia, as a result of increased metabolism.

The hypothalamus also takes part in maintaining the sleep-wake biorhythm.

The nuclei of the anterior hypothalamus are connected to the pituitary gland and transport biologically active substances that are produced by the neurons of these nuclei. Neurons of the preoptic nucleus produce releasing factors (statins and liberins) that control the synthesis and release of pituitary hormones.

Neurons of the preoptic, supraoptic, paraventricular nuclei produce true hormones - vasopressin and oxytocin, which descend along the axons of neurons to the neurohypophysis, where they are stored until released into the blood.

Neurons of the anterior pituitary gland produce 4 types of hormones: 1) somatotropic hormone, which regulates growth; 2) gonadotropic hormone that promotes the growth of germ cells, corpus luteum, enhances milk production; 3) thyroid-stimulating hormone– stimulates function thyroid gland; 4) adrenocorticotropic hormone - enhances the synthesis of hormones of the adrenal cortex.

The intermediate lobe of the pituitary gland secretes the hormone intermedin, which affects skin pigmentation.

The posterior lobe of the pituitary gland secretes two hormones - vasopressin, which affects the smooth muscles of the arterioles, and oxytocin, which acts on the smooth muscles of the uterus and stimulates milk secretion.

The hypothalamus also plays an important role in emotional and sexual behavior.

The epithalamus (pineal gland) includes the pineal gland. The pineal gland hormone, melatonin, inhibits the formation of gonadotropic hormones in the pituitary gland, and this in turn delays sexual development.

Nonspecific core

Page 1

Nonspecific nuclei are more ancient in origin and include the median and intralaminar nuclei, as well as the medial part of the anterior ventral nucleus. Neurons of nonspecific nuclei first transmit signals to subcortical structures, from which impulses arrive in parallel to different departments bark. Nonspecific nuclei are a continuation of the reticular formation of the midbrain, representing the reticular formation of the thalamus.

Functions of the diencephalon

Electrical stimulation of the nonspecific nuclei of the thalamus causes periodic fluctuations in potentials in the cerebral cortex, synchronous with the rhythm of activity of the thalamic structures. The reaction in the cortex occurs with a long latent period and increases significantly with repetition. Thus, the neurons of the cerebral cortex are involved in the activity process as if gradually. This reaction involving the cerebral cortex differs from its specific responses in its generalization, covering large areas of the cortex. Impulses traveling along the paths of pain sensitivity are formed when various areas of the body are irritated and internal organs. Latent periods of responses in the thalamus are characterized by great duration and variability.

Another type of endings of thalamocortical projections is formed by axons of neurons of nonspecific nuclei of the thalamus.

When recording the electrical activity of various parts of the rabbit’s brain, it was found that reactions in the form of an increase in the number of soap waves and spindles occur simultaneously in all leads (at a recording speed of 15 mm/s), and the most intense reaction was observed in the hypothalamus, followed by the sensomotor cortex. visual, specific nuclei of the thalamus, nonspecific nuclei of the thalamus. It can be concluded that the most reactive formations of the central nervous system when exposed to PMP are the cortex and hypothalamus.

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.

To study the mechanism of formation of conditioned reflexes, it is essential not only to accurately record the response itself (salivation, movement, etc.), but also to study the electrical activity that occurs in various brain structures during the action of conditioned and unconditioned stimuli. To record electrical activity, electrodes are used that are chronically implanted into various areas or layers of the cerebral cortex, as well as into specific and nonspecific nuclei of the thalamus, reticular formation, hippocampus and other parts of the brain. In experiments with conditioned reflexes Microelectrode methods are widely used to record the electrical activity of individual neurons involved in the implementation of a conditioned reflex reaction. Electronic computers are used for automatic analysis of electroencephalograms recorded from various areas of the cortex in experiments on animals directly during conditioned reflex reactions.

Nonspecific nuclei are more ancient in origin and include the median and intralaminar nuclei, as well as the medial part of the anterior ventral nucleus. Neurons of nonspecific nuclei first transmit signals to subcortical structures, from which impulses arrive in parallel to different parts of the cortex. Nonspecific nuclei are a continuation of the reticular formation of the midbrain, representing the reticular formation of the thalamus.

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. At the same time, the fibers coming from the cortex to the neurons of specific nuclei are characterized by the topographic localization of their endings, in contrast to the widely branched system of diffusely ending fibers in nonspecific nuclei.

The spinothalamic tract is significantly different from the lemniscal tract. Its first neurons are also located in the dorsal ganglion, from where they send slow-conducting unmyelinated nerve fibers to the spinal cord. These neurons have large receptive fields, sometimes including a significant portion of the skin surface. The second neurons of this pathway are localized in the gray matter spinal cord, and their axons as part of the ascending spinothalamic tract are sent after decussation at the spinal level to the ventrobasal nuclear complex of the thalamus (differentiated projections), as well as to the ventral nonspecific nuclei of the thalamus, the internal geniculate body, the nuclei of the brainstem and the hypothalamus. The third neurons of the spinothalamic tract localized in these nuclei only partially give projections to the somatosensory zone of the cortex.

Pages: 1

8. Structure and functional role of the thalamus and hypothalamus

Thalamus (lat. Thalamus, latin pronunciation: thalamus; from Greek θάλαμος - “hillock”) is a region of the brain responsible for the redistribution of information from the senses, with the exception of smell, to the cerebral cortex.

This information (impulses) enters the nuclei of the thalamus. The nuclei themselves consist of gray matter, which is formed by neurons. Each nucleus is a collection of neurons. The nuclei are separated by white matter. In the thalamus, four main nuclei can be distinguished: a group of neurons that redistribute visual information; the core redistributes auditory information; the core that redistributes tactile information and the core that redistributes the sense of equilibrium and balance. After information about any sensation has entered the thalamic nucleus, it occurs there. primary processing, that is, for the first time, temperature, visual image, etc. are realized. It is believed that the thalamus plays an important role in the implementation of memory processes. Information is recorded as follows: the first stage of engram formation occurs in the SS. It begins when a stimulus excites peripheral receptors. From them, along the pathways, nerve impulses go to the thalamus, and then to the cortex. In it the highest synthesis of sensation is realized. Damage to the thalamus can lead to anterograde amnesia and also cause tremor - an involuntary shaking of the limbs at rest - although these symptoms are absent when the patient performs movements consciously. Associated with the thalamus rare disease called "fatal familial insomnia". http://www.bibliotekar.ru/447/52.htm medbiol.ru/medbiol/mozg/0001b9d3.htm

Thalamus (visual thalamus): general information

The thalamus is a part of the forebrain.

Anatomically, the thalamus (visual thalamus) is a paired organ formed mainly by gray matter. It is the subcortical center of all types of sensitivity; it has several dozen nuclei that receive information from all sensory organs and transmit it to the cerebral cortex. The thalamus is connected to the limbic system, reticular formation, hypothalamus, cerebellum, and basal ganglia. The thalamus is an ovoid mass of gray matter with a thicker posterior end (Fig. 38, Fig. 39).

As already mentioned, the thalamus is a paired formation: there is a dorsal thalamus and a ventral thalamus. Between the thalamus is the cavity of the third ventricle. The surface of the thalamus, facing the cavity of the third ventricle, is covered with a thin layer of gray matter. The medial surfaces of the right and left thalami are connected to each other by an interthalamic fusion, which lies almost in the middle. The medial surface of the thalamus is separated from the superior thin medullary strip. The upper part of the optic hillocks is free and faces the cavity of the central part of the lateral ventricles. In the anterior section, the thalamus narrows and ends with the anterior tubercle. The posterior end of the thalamus is thickened and is called the thalamic cushion. The name “pillow” arose due to the fact that the hemispheres lie on the thalami telencephalon, and they rest on pillow-like thickenings. The lateral surface of the thalamus is adjacent to the internal capsule and borders the caudate nucleus of the telencephalon. The lower surface of the thalamus is located above the cerebral peduncle, fused with the tegmentum of the midbrain.

A pronounced evolutionary pattern of changes in quantitative relationships between the dorsal and ventral thalamus can be traced. During the process of evolution, the size of the ventral part of the thalamus decreases, and the dorsal part increases. In lower vertebrates, the ventral thalamus is developed, while in mammals the nuclei of the dorsal thalamus predominate. This is due to the fact that the dorsal part of the thalamus is associated primarily with the development of ascending pathways from visual system, auditory system and sensorimotor systems to the cerebral cortex.

The thalamus terminates the axons of most sensory neurons that carry impulses to the cerebral cortex. Here the nature and origin of these impulses are analyzed, and they are transmitted to the corresponding sensory areas of the cortex along fibers originating in the thalamus. Thus, the thalamus plays the role of a processing, integrating and switching center for all sensory information. In addition, the thalamus modifies information coming from certain areas of the cortex and is believed to be involved in the sensation of pain and pleasure. The area of the reticular formation that is related to the regulation of motor activity begins in the thalamus. The dorsal region lying immediately in front of the thalamus - the anterior choroid plexus - is responsible for the transport of substances between the cerebrospinal fluid located in the third ventricle and the fluid filling the subarachnoid space. Thus, the thalamus filters information coming from all receptors and carries it out pre-treatment and then directs it to various areas of the cortex. In addition, the thalamus makes connections between the cortex, on the one hand, and the cerebellum and basal ganglia on the other.

In other words, through the thalamus, consciousness controls automatic movements.

Axons of the posterior columnar medial lemniscal tract and spinothalamic tract terminate in synapses on neurons of the VPL nucleus of the thalamus. This nucleus also terminates several other parallel ascending sensory tracts, such as the spinocervical tract and the pathway through the z nucleus. The trigeminothalamic tracts from the main sensory nucleus of the trigeminal nerve and the spinal nucleus of the trigeminal nerve form synapses in the thalamic ILM nucleus.

The responses of many neurons of the VPL-iVPM nuclei are similar to the reactions of neurons of the first and second orders of the ascending tracts. Among these responses, reactions of sensory receptors of a certain type sometimes predominate, and their receptive fields may be small, although usually larger than those of primary afferents.

These fields are located contralateral to the thalamic neurons, the localization of which is topographically related to the location of the receptive fields, i.e. VPL- and VLM-nuclei, and have a somatotopic organization. The lower limb is represented by neurons of the lateral part of the VPL nucleus, the upper limb is represented by neurons of the medial part of the VPL nucleus, and the face is represented by neurons of the VLM nucleus (Fig. 34.10).

Many thalamic neurons contain not only excitatory, but also inhibitory receptive fields. The process of inhibition can be realized in the dorsal column nuclei or the dorsal horn of the spinal cord, but inhibitory neural circuits also exist in the thalamus. Inhibitory interneurons are present in the VPL and VLM nuclei (in primates, but not in rodents), in addition, some inhibitory interneurons of the reticular nucleus of the thalamus are projected. In the intrinsic inhibitory neurons of these nuclei and neurons of the reticular nucleus, the inhibitory transmitter is GABA.

Neurons of the VPL and VLM nuclei have an interesting feature: in contrast to the activity of sensory neurons, more low levels of the somatosensory system, the excitability of thalamic neurons depends on the stage of the sleep-wake cycle and changes with anesthesia.

During drowsiness or barbiturate anesthesia, thalamic neurons tend to induce alternating sequences of excitatory and inhibitory postsynaptic potentials. Intermittent discharges, in turn, cause periodic activity of neurons in the cerebral cortex. On the encephalogram this is reflected in the alpha rhythm or spindle bursts. This alternation of series of excitatory and inhibitory postsynaptic potentials possibly reflects the level of excitation of thalamic neurons, which is mediated by the interaction of excitatory neurotransmitter amino acids with non-NMDA-type and NMDA-type postsynaptic membrane receptors. In addition, inhibition of thalamic neurons mediated by the recurrent pathways of the reticular nucleus may be involved in this periodic process.

The spinothalamic tract and part of the trigeminothalamic tract, starting from the spinal trigeminal nucleus, send projections to the central lateral nucleus of the intraplate complex of the thalamus. The intralamellar nuclei do not have a somatotopic organization and are diffusely projected in the cerebral cortex, as well as in the basal ganglia. It is possible that projections of the central lateral nucleus in the SI cortical area are involved in the formation of the awakening reaction in this area and the mechanism of selective attention.

After the destruction of the VPL and VLM nuclei, the sensitivity of the contralateral side of the torso and face decreases. The deficit concerns primarily sensory categories related to the transmission of information along the posterior columnar medial lemniscal tract and its equivalent trigeminal system. The sensory-discriminative component of pain sensitivity is also lost, but with an intact medial thalamus, the motivational-affective component is preserved, presumably due to the medial spinothalamic and spinoreticulothalamic projections.

In some people, after damage to the somatosensory thalamus, a syndrome of central pain occurs, called thalamic. However, pain that does not differ from thalamic pain can also develop after damage to the brain stem or cortex.

Diencephalon. Thalamus. Thalamus nuclei. Hypothalamus. SOYBEAN and PVN hormones.

33, fig. 42, fig. 43, fig. 44, fig. 59, fig. 63, fig. 64, fig. 75.

To have an idea of what the thalamus and hypothalamus are, you must first understand what the diencephalon is. This part of the brain is located under the so-called corpus callosum, just above the midbrain.

It includes the metathalamus, hypothalamus and thalamus. Functions diencephalon very extensive - it integrates motor, sensory and autonomic reactions, which are extremely important for normal human activity. The diencephalon develops from the forebrain, with its walls forming the third ventricle of the brain structure.

The thalamus is a substance that makes up the bulk of the diencephalon. Its functions are to receive and transmit to the cerebral cortex and central nervous system almost all impulses, with the exception of olfactory ones.

The thalamus has two symmetrical parts and is part of the limbic system. This structure is located in the forebrain, near the center of the heads.

The functions of the thalamus are carried out through nuclei, of which it has 120. These nuclei are actually responsible for receiving and sending signals and impulses.

Neurons that arise from the thalamus are divided as follows:

Specific– transmit information received from the eye, auditory, muscle and other sensitive areas.
Nonspecific- are mainly responsible for human sleep, so if damage to these neurons occurs, the person will want to sleep all the time.
Associative– regulate the excitation of the modality.

Based on the above, we can say that the thalamus regulates various processes occurring in the human body, and is also responsible for receiving signals about the state of the sense of balance.

If we talk about sleep regulation, then if the functionality of some thalamic neurons is disrupted, a person can develop such persistent insomnia that he can even die from it.

Thalamic diseases

When the thalamic thalamus is damaged, thalamic syndrome develops; the symptoms can be very diverse, since they depend on the specific function of the nuclei that have lost their functionality. The cause of the development of thalamic syndrome is a functional disorder of the vessels of the posterior cerebral artery. In this case, you may observe:

impaired facial sensitivity;
pain syndrome that covers one half of the body;
lack of vibration sensitivity;
paresis;
muscle atrophy is observed in the affected half of the body;
a symptom of the so-called thalamic hand - a certain position of the phalanges of the fingers and the hand itself,
attention disorder.

Hypothalamus brain

The structure of the hypothalamus is very complex, so this article will only discuss its functions. They consist in human behavioral responses, as well as in the influence on vegetation. In addition, the hypothalamus actively takes part in the regeneration of reserves.

The hypothalamus also has many nuclei, which are divided into posterior, middle and anterior. The nuclei of the posterior category regulate the sympathetic reactions of the body - increased blood pressure, rapid pulse, dilation of the pupil of the eye. On the contrary, nuclei of the middle category reduce sympathetic manifestations.

The hypothalamus is responsible for:

thermoregulation;
feeling of fullness and hunger;
fear;
sexual desire and so on.

All these processes occur as a result of activation or inhibition of various nuclei.

For example, if a person’s blood vessels dilate and he becomes cold, it means that the anterior group of nuclei has been irritated, and if the posterior nuclei are damaged, this can provoke lethargic sleep.

The hypothalamus is responsible for the regulation of movements; if excitation occurs in this area, a person can make chaotic movements. If disturbances occur in the so-called gray mound, which is also part of the hypothalamus, then the person begins to suffer from metabolic disorders.

Pathologies of the hypothalamus

All diseases of the hypothalamus are associated with dysfunction of this structure, or more precisely with the characteristics of hormonal synthesis. Diseases can occur due to excess production of hormones, due to decreased secretion of hormones, but illnesses can also appear due to the normal production of hormones from the hypothalamus. There is a very close connection between the hypothalamus and the pituitary gland - they have a common blood circulation, a similar anatomical structure and identical functions. Therefore, diseases are often combined into one group, which is called pathologies of the hypothalamic-pituitary system.

Often the cause of pathological symptoms is the occurrence of a pituitary adenoma or the hypothalamus itself. In this case, the hypothalamus begins to produce a large number of hormones, as a result of which the corresponding symptoms appear.

A typical lesion of the hypothalamus is prolactinoma, a tumor that is hormonally active because it produces prolactin.

Another dangerous disease is hypothalamic-pituitary syndrome; this disease is associated with impaired functionality of both the pituitary gland and the hypothalamus, which leads to the development of a characteristic clinical picture.

Due to the fact that there are many diseases affecting the hypothalamic-pituitary system, below will be given general symptoms, which can be used to suspect pathologies of this part of the brain:

Problems with saturation of the body. The situation can develop in two directions - either a person completely loses his appetite, or does not feel full no matter how much he eats.
Problems with thermoregulation. This manifests itself in an increase in temperature, but no inflammatory processes not observed in the body. In addition, an increase in temperature is accompanied by chills, increased sweating, increased thirst, obesity and uncontrollable hunger.
Epilepsy on a hypothalamic basis - interruptions in heart function, high blood pressure, painful sensations in the epigastric region. During an attack, a person loses consciousness.
Changes in the functioning of the vegetative-vascular system. They manifest themselves in the functioning of the digestive system (belching, abdominal pain, bowel movements), in the functioning of the respiratory system (tachypnea, difficulty breathing, suffocation) and in the functioning of the heart and blood vessels (failures in heart rate, high or low blood pressure, chest pain).

Neurologists, endocrinologists and gynecologists treat diseases of the hypothalamus.

Conclusion and conclusions

Since the hypothalamus regulates a person's day and night rhythms, it is important to maintain a daily routine.
It is necessary to improve blood circulation and saturate all parts of the brain with oxygen. Smoking and drinking alcoholic beverages is prohibited. Recommended walks on fresh air and sports activities.
It is important to normalize the synthesis of hormones.
It is recommended to saturate the body with all essential vitamins and minerals.

Disruption of the thalamus and hypothalamus leads to various diseases, most of which end sadly, so you need to be very attentive to your health and, at the first ailment, contact specialists for advice.

Introduction

Thalamus (visual thalamus)

Hypothalamus

Conclusion

The medial geniculate body is located behind the thalamic cushion; together with the lower colliculi of the midbrain roof plate, it is the subcortical center of the auditory analyzer.

The lateral geniculate body is located inferior to the thalamic cushion. Together with the superior colliculus, it forms the subcortical center of the visual analyzer.

Epithalamus (suprathalamic region) includes pineal body (epiphysis), leashes and triangles of leashes. The triangles of the leashes contain nuclei related to the olfactory analyzer. The leashes extend from the triangles of the leashes, go caudally, are connected by a commissure and pass into the pineal gland. The latter is, as it were, suspended on them and is located between the upper tubercles of the quadrigeminal. The pineal gland is an endocrine gland. Its functions have not been fully established; it is assumed that it regulates the onset of puberty.

Thalamus (visual thalamus)

General structure and location of the thalamus.

Figure 1. Diencephalon in sagittal section.

The thickness of the gray matter of the thalamus is divided by a vertical Y-shaped layer (plate) of white matter into three parts - anterior, medial and lateral.

Medial surface of the thalamus clearly visible on the sagittal (sagittal - sagittal (lat. " sagitta"- arrow), dividing into symmetrical right and left halves) in a section of the brain (Fig. 1). The medial (i.e., located closer to the middle) surface of the right and left thalamus, facing each other, form side walls III cerebral ventricle (diencephalon cavity) in the middle they are connected to each other interthalamic fusion .

Anterior (inferior) surface of the thalamus fused with the hypothalamus, through it, from the caudal side (i.e., located closer to the lower part of the body), pathways from the cerebral peduncles enter the diencephalon.

Lateral ( those. lateral) surface thalamus borders on internal capsule - a layer of white matter of the cerebral hemispheres, consisting of projection fibers connecting the cerebral cortex with the underlying brain structures.

Each of these parts of the thalamus contains several groups thalamic nuclei. In total, the thalamus contains from 40 to 150 specialized nuclei.

Functional meaning thalamic nuclei.

According to topography, the thalamic nuclei are divided into 8 main groups:

1. anterior group;

2. mediodorsal group;

3. group of midline nuclei;

4. dorsolateral group;

5. ventrolateral group;

6. ventral posteromedial group;

7. posterior group (nuclei of the thalamic cushion);

8. intralaminar group.

The nuclei of the thalamus are divided into sensory ( specific and nonspecific), motor and associative. Let us consider the main groups of thalamic nuclei necessary to understand its functional role in the transmission of sensory information to the cerebral cortex.

Located in the anterior part of the thalamus front group thalamic nuclei ( Fig.2). The largest of them are anteroventral core and anteromedial core. They receive afferent fibers from the mammillary bodies, the olfactory center of the diencephalon. Efferent fibers (descending, i.e. carrying impulses from the brain) from the anterior nuclei are directed to the cingulate gyrus of the cerebral cortex.

The anterior group of thalamic nuclei and associated structures are an important component of the limbic system of the brain, which controls psycho-emotional behavior.

Rice. 2. Topography of thalamic nuclei

In the medial part of the thalamus there are mediodorsal nucleus And group of midline nuclei.

Mediodorsal nucleus has bilateral connections with the olfactory cortex of the frontal lobe and the cingulate gyrus of the cerebral hemispheres, the amygdala and the anteromedial nucleus of the thalamus. Functionally, it is also closely connected with the limbic system and has bilateral connections with the parietal, temporal and insula brain

The mediodorsal nucleus is involved in the implementation of higher mental processes. Its destruction leads to a decrease in anxiety, anxiety, tension, aggressiveness, and the elimination of obsessive thoughts.

Midline nuclei are numerous and occupy the most medial position in the thalamus. They receive afferent (i.e., ascending) fibers from the hypothalamus, from the raphe nuclei, the locus coeruleus of the reticular formation of the brain stem, and partially from the spinothalamic tracts as part of the medial lemniscus. Efferent fibers from the midline nuclei are sent to the hippocampus, amygdala and cingulate gyrus of the cerebral hemispheres, which are part of the limbic system. Connections with the cerebral cortex are bilateral.

The midline nuclei play an important role in the processes of awakening and activation of the cerebral cortex, as well as in supporting memory processes.

In the lateral (i.e. lateral) part of the thalamus there are dorsolateral, ventrolateral, ventral posteromedial And posterior group of nuclei.

Nuclei of the dorsolateral group relatively little studied. They are known to be involved in the pain perception system.

Nuclei of the ventrolateral group anatomically and functionally differ from each other. Posterior nuclei of the ventrolateral group often considered as one ventrolateral nucleus of the thalamus. This group receives fiber upward path general sensitivity as part of the medial loop. Fibers of taste sensitivity and fibers from the vestibular nuclei also come here. Efferent fibers starting from the nuclei of the ventrolateral group are sent to the cortex of the parietal lobe of the cerebral hemispheres, where they carry somatosensory information from the whole body.

TO posterior group nuclei(nucleus of the thalamic cushion) there are afferent fibers from the superior colliculi and fibers in the optic tracts. Efferent fibers are widely distributed in the cortex of the frontal, parietal, occipital, temporal and limbic lobes of the cerebral hemispheres.

The nuclear centers of the thalamic cushion are involved in the complex analysis of various sensory stimuli. They play a significant role in the perceptual (related to perception) and cognitive (cognitive, thinking) activity of the brain, as well as in memory processes - storing and reproducing information.

Intralaminar group of nuclei The thalamus lies deep in a vertical Y-shaped layer of white matter. The intralaminar nuclei are interconnected with the basal ganglia, the dentate nucleus of the cerebellum and the cerebral cortex.

These nuclei play an important role in the activation system of the brain. Damage to the intralaminar nuclei in both thalami leads to sharp decline motor activity, as well as apathy and destruction of the motivational structure of the individual.

The cerebral cortex, thanks to bilateral connections with the nuclei of the thalamus, is capable of exerting a regulatory effect on their functional activity.

Thus, the main functions of the thalamus are:

processing of sensory information from receptors and subcortical switching centers with its subsequent transfer to the cortex;

participation in the regulation of movements;

ensuring communication and integration of different parts of the brain.

Hypothalamus

General structure and location of the hypothalamus.

Hypothalamus ( hypothalamus) is the ventral section (i.e., abdominal) of the diencephalon. It consists of a complex of formations located under the third ventricle. The hypothalamus is limited anteriorly visual cross ( chiasm), laterally - the anterior part of the subthalamus, the internal capsule and the optic tracts extending from the chiasm. Posteriorly, the hypothalamus continues into the tegmentum of the midbrain. The hypothalamus includes mastoid bodies, gray tubercle and optic chiasm. Mastoid bodies located on the sides of the midline anterior to the posterior perforated substance. These are formations of irregular spherical shape white. Anterior to the gray tubercle is located optic chiasm. There is a transition to the opposite side of some of the fibers optic nerve, coming from the medial half of the retina. After the decussation, the optic tracts are formed.

Gray tubercle located anterior to the mastoid bodies, between the optic tracts. The gray tubercle is a hollow protrusion of the lower wall of the third ventricle, formed by a thin plate of gray matter. The apex of the gray mound is elongated into a narrow hollow funnel, at the end of which is pituitary gland [ 4; 18].

Pituitary gland: structure and functioning

Pituitary(hypophysis) - an endocrine gland, it is located in a special depression at the base of the skull, the “sella turcica” and is connected to the base of the brain with the help of a pedicle. The pituitary gland contains the anterior lobe ( adenohypophysis - glandular pituitary gland) and posterior lobe ( neurohypophysis).

Posterior lobe, or neurohypophysis, consists of neuroglial cells and is a continuation of the hypothalamic infundibulum. Larger share - adenohypophysis, built of glandular cells. Due to the close interaction of the hypothalamus with the pituitary gland, a single system functions in the diencephalon hypothalamic-pituitary system, controlling the work of all endocrine glands, and with their help, the vegetative functions of the body (Fig. 3).

Figure 3. The pituitary gland and its influence on other endocrine glands

There are 32 pairs of nuclei in the gray matter of the hypothalamus. Interaction with the pituitary gland is carried out through neurohormones secreted by the nuclei of the hypothalamus - releasing hormones. By system blood vessels they enter the anterior lobe of the pituitary gland (adenohypophysis), where they contribute to the release of tropic hormones that stimulate the synthesis of specific hormones in other endocrine glands.

In the anterior lobe of the pituitary gland are being developed tropic hormones (thyroid-stimulating hormone - thyrotropin, adrenocorticotropic hormone - corticotropin and gonadotropic hormones - gonadotropins) and effector hormones (growth hormones - somatotropin and prolactin).

Hormones of the anterior pituitary gland

Thyroid-stimulating hormone (thyrotropin) stimulates thyroid function. If the pituitary gland is removed or destroyed in animals, atrophy of the thyroid gland occurs, and the administration of thyrotropin restores its functions.

Adrenocorticotropic hormone (corticotropin) stimulates the function of the zona fasciculata of the adrenal cortex, in which hormones are formed glucocorticoids. The effect of the hormone on the zona glomerulosa and reticularis is less pronounced. Removal of the pituitary gland in animals leads to atrophy of the adrenal cortex. Atrophic processes affect all zones of the adrenal cortex, but the most profound changes occur in the cells of the reticular and fascicular zones. The extra-adrenal effect of corticotropin is expressed in stimulation of lipolysis processes, increased pigmentation, and anabolic effects.

Gonadotropic hormones (gonadotropins). Follicle stimulating hormone ( follitropin) stimulates the growth of the vesicular follicle in the ovary. The effect of follitropin on the formation of female sex hormones (estrogens) is small. This hormone is present in both women and men. In men, under the influence of follitropin, the formation of germ cells (spermatozoa) occurs. Luteinizing hormone ( lutropin) necessary for the growth of the vesicular follicle of the ovary in the stages preceding ovulation, and for ovulation itself (rupture of the membrane of a mature follicle and the release of an egg from it), the formation of the corpus luteum at the site of the burst follicle. Lutropin stimulates the formation of female sex hormones - estrogens. However, in order for this hormone to exert its effect on the ovary, a preliminary long-term action of follitropin is necessary. Lutropin stimulates the production progesterone yellow body. Lutropin is available in both women and men. In men, it promotes the formation of male sex hormones - androgens.

Effector:

Growth hormone (somatotropin) stimulates body growth by enhancing protein formation. Under the influence of the growth of epiphyseal cartilages in the long bones of the upper and lower limbs bones grow in length. Growth hormone increases insulin secretion through somatomedins, formed in the liver.

Prolactin stimulates the formation of milk in the alveoli of the mammary glands. Prolactin exerts its effect on the mammary glands after the preliminary action of the female sex hormones progesterone and estrogens on them. The act of sucking stimulates the formation and release of prolactin. Prolactin also has a luteotropic effect (promotes the long-term functioning of the corpus luteum and the formation of the hormone progesterone).

Processes in the posterior lobe of the pituitary gland

The posterior lobe of the pituitary gland does not produce hormones. Inactive hormones that are synthesized in the paraventricular and supraoptic nuclei of the hypothalamus enter here.

The hormones are predominantly produced in the neurons of the paraventricular nucleus oxytocin, and in the neurons of the supraoptic nucleus - vasopressin (antidiuretic hormone). These hormones accumulate in the cells of the posterior pituitary gland, where they are converted into active hormones.

Vasopressin (antidiuretic hormone) plays an important role in the processes of urine formation and, to a lesser extent, in the regulation of blood vessel tone. Vasopressin, or antidiuretic hormone - ADH (diuresis - urine output) - stimulates the reabsorption (resorption) of water in the renal tubules.

Oxytocin (ocytonin) increases uterine contraction. Its contraction increases sharply if it was previously under the influence of the female sex hormones estrogen. During pregnancy, oxytocin does not affect the uterus, since under the influence of the corpus luteum hormone progesterone, it becomes insensitive to oxytocin. Mechanical irritation of the cervix causes the release of oxytocin reflexively. Oxytocin also has the ability to stimulate milk production. The act of sucking reflexively promotes the release of oxytocin from the neurohypophysis and the secretion of milk. In a state of stress in the body, the pituitary gland releases additional amounts of ACTH, which stimulates the release of adaptive hormones by the adrenal cortex.

Functional significance of the hypothalamic nuclei

IN anterolateral part hypothalamus is distinguished anterior and middle groups of hypothalamic nuclei (Fig. 4).

Figure 4. Topography of the hypothalamic nuclei

TO anterior group relate suprachiasmatic nuclei, preoptic nucleus, and the largest - supraoptic And paraventricular kernels.

In the nuclei of the anterior group are localized:

steam center sympathetic division(PSNS) of the autonomic nervous system.

Stimulation of the anterior hypothalamus leads to parasympathetic type reactions: constriction of the pupil, decreased heart rate, dilation of the lumen of blood vessels, fall blood pressure, increased peristalsis (i.e., wave-like contraction of the walls of hollow tubular organs, promoting the movement of their contents to the intestinal outlets);

heat transfer center. Destruction of the anterior section is accompanied by an irreversible increase in body temperature;

thirst center;

neurosecretory cells that produce vasopressin ( supraoptic core) and oxytocin ( paraventricular nucleus). In neurons paraventricular And supraoptic nuclei, a neurosecretion is formed, which moves along their axons to the posterior part of the pituitary gland (neurohypophysis), where it is released in the form of neurohormones - vasopressin and oxytocin entering the blood.

Damage to the anterior nuclei of the hypothalamus leads to the cessation of the release of vasopressin, resulting in the development of diabetes insipidus. Oxytocin has a stimulating effect on the smooth muscles of internal organs, such as the uterus. In general, the water-salt balance of the body depends on these hormones.

IN preoptic The nucleus produces one of the releasing hormones - luliberin, which stimulates the production of luteinizing hormone in the adenohypophysis, which controls the activity of the gonads.

Suprachiasmatic nuclei take an active part in the regulation of cyclical changes in the body's activity - circadian, or daily, biorhythms (for example, in the alternation of sleep and wakefulness).

TO middle group hypothalamic nuclei include dorsomedial And ventromedial nucleus, nucleus of the gray tuberosity And funnel core.

In the kernels middle group localized:

center of hunger and satiety. Destruction ventromedial hypothalamic nucleus leads to excess food consumption (hyperphagia) and obesity, and damage kernels of gray mound- loss of appetite and sudden weight loss (cachexia);

sexual behavior center;

center of aggression;

the center of pleasure, which plays an important role in the processes of formation of motivations and psycho-emotional forms of behavior;

neurosecretory cells that produce releasing hormones (liberins and statins), regulating the production of pituitary hormones: somatostatin, somatoliberin, luliberin, folliberin, prolactoliberin, thyreoliberin, etc. Through the hypothalamic-pituitary system they influence growth processes, speed physical development and puberty, the formation of secondary sexual characteristics, the functions of the reproductive system, as well as metabolism.

The middle group of nuclei controls water, fat and carbohydrate metabolism, affects blood sugar levels, the ionic balance of the body, the permeability of blood vessels and cell membranes.

Rear end The hypothalamus is located between the gray tubercle and the posterior perforated substance and consists of the right and left mastoid bodies.

In the posterior part of the hypothalamus, the largest nuclei are: medial And lateral nucleus, posterior hypothalamic nucleus .

In the nuclei of the posterior group are localized:

center that coordinates the activity of the sympathetic division (SNS) of the autonomic nervous system ( posterior hypothalamic nucleus). Stimulation of this nucleus leads to sympathetic reactions: pupil dilation, increased heart rate and blood pressure, increased respiration and decreased tonic contractions of the intestines;

heat production center ( posterior hypothalamic nucleus). Destruction of the posterior hypothalamus causes lethargy, drowsiness and decreased body temperature;

subcortical centers of the olfactory analyzer. Medial And lateral nucleus in each mastoid body they are the subcortical centers of the olfactory analyzer, and are also part of the limbic system;

neurosecretory cells that produce releasing hormones that regulate the production of pituitary hormones.

Features of the blood supply to the hypothalamus

The nuclei of the hypothalamus receive abundant blood supply. The capillary network of the hypothalamus is several times more branched than in other parts of the central nervous system. One of the features of the capillaries of the hypothalamus is their high permeability, caused by the thinning of the walls of the capillaries and their fenestration ("fenestration" - the presence of spaces - "windows" - between adjacent endothelial cells of the capillaries (from the Latin. " fenestra" - window). As a result, the blood-brain barrier (BBB) is weakly expressed in the hypothalamus, and hypothalamic neurons are able to perceive changes in the composition of the cerebrospinal fluid and blood (temperature, ion content, presence and amount of hormones, etc.).

Functional significance of the hypothalamus

The hypothalamus is the central link connecting the nervous and humoral mechanisms regulation of the body's vegetative functions. The control function of the hypothalamus is determined by the ability of its cells to secrete and axonally transport regulatory substances, which are transferred to other structures of the brain, cerebrospinal fluid, blood or pituitary gland, changing the functional activity of target organs.

There are 4 neuroendocrine systems in the hypothalamus:

Hypothalamic-extrahypothalamic system represented by neurosecretory cells of the hypothalamus, the axons of which extend into the thalamus, structures of the limbic system, and medulla oblongata. These cells secrete endogenous opioids, somatostatin, etc.

Hypothalamic-adenopituitary system connects the nuclei of the posterior hypothalamus with the anterior lobe of the pituitary gland. Releasing hormones (liberins and statins) are transported along this pathway. Through them, the hypothalamus regulates the secretion of tropic hormones of the adenohypophysis, which determine the secretory activity of the endocrine glands (thyroid, reproductive, etc.).

Hypothalamic-metapituitary system connects the neurosecretory cells of the hypothalamus with the pituitary gland. The axons of these cells transport melanostatin and melanoliberin, which regulate the synthesis of melanin, the pigment that determines the color of the skin, hair, iris and other body tissues.

Hypothalamic-neurohypophyseal system connects the nuclei of the anterior hypothalamus with the posterior (glandular) lobe of the pituitary gland. These axons transport vasopressin and oxytocin, which accumulate in the posterior lobe of the pituitary gland and are released into the bloodstream as needed.

Conclusion

Thus, the dorsal part of the diencephalon is phylogenetically younger thalamic brain, being the highest subcortical sensory center in which almost all afferent pathways carrying sensory information from the body organs and sensory organs to the cerebral hemispheres are switched. The tasks of the hypothalamus also include the management of psycho-emotional behavior and participation in the implementation of higher mental and psychological processes, in particular memory.

Ventral section - hypothalamus is a phylogenetically older formation. The hypothalamic-pituitary system controls the humoral regulation of water-salt balance, metabolism and energy, the functioning of the immune system, thermoregulation, reproductive function etc. Playing a regulatory role for this system, the hypothalamus is the highest center that controls the autonomic (autonomic) nervous system.

Bibliography

1. Human Anatomy / Ed. M.R. Sapina. - M.: Medicine, 1993.

2. Bloom F., Leiserson A., Hofstadter L. Brain, mind, behavior. - M.: Mir, 1988.

3. Histology / Ed. V.G. Eliseeva. - M.: Medicine, 1983.

4. Prives M.G., Lysenkov N.K., Bushkovich V.I. Human anatomy. - M.: Medicine, 1985.

5. Sinelnikov R.D., Sinelnikov Ya.R. Atlas of human anatomy. - M.: Medicine, 1994.

6. Tishevskoy I.A. Anatomy of the central nervous system: Tutorial. - Chelyabinsk: SUSU Publishing House, 2000.

Red core

Anterior and posterior tubercles of the quadrigeminal.

Cerebellum.

The white matter of the cerebellum is the cerebellar pathways. Among the WM are the cerebellar nuclei. The cerebellum receives signals from all structures associated with movement. There they are processed, then a huge stream of inhibitory influences on the SC comes from the cerebellum.

Midbrain - quadrigeminal, substantia nigra, cerebral peduncles.

The anterior tubercles - the primary visual zone - form an orienting reflex to a visual signal

The posterior colliculi - the primary auditory zone - form an orienting reflex to a sound signal

Function - guard reflexes (indicative)

Skeletal muscle tone

Redistribution of tone when changing posture

Streamline the relationship between flexor and extensor muscles

Decerebrate rigidity – damage to the red nucleus, excitability/tone increases sharply strong muscles

Black substance– source of dopamine

The inhibitory function of the basal ganglia prevents stimulation of the cerebral hemispheres

Tone skeletal muscles responsible for subtle instrumental movements

Example of dysfunction: Parkinson's disease

Thalamus– signals come from all receptors except the olfactory one; it is called the collector of afferent impulses.

Before entering the cortex, information enters the thalamus. If the thalamus is destroyed, then the cortex does not receive this information. If visual signals enter the geniculate bodies (one of the nuclei of the thalamus), they go immediately to the occipital lobe of the cerebral cortex. The same goes for the auditory ear, only it goes to the temporal lobe. The thalamus processes information and selects the most appropriate

The thalamus contains dozens of nuclei, which are divided into 2 groups: specific and nonspecific.

When information enters the specific nuclei of the thalamus, evoked responses arise in the cortex, but the responses arise in strictly selected areas of the hemispheres. Information from the nonspecific nuclei of the thalamus reaches the entire cerebral cortex. This occurs to increase the excitability of the entire cortex so that it more clearly perceives specific information.

Adequate pain occurs with the participation of the frontal, parietal cortex, and thalamus. The thalamus is the highest center of pain sensitivity. When some nuclei of the thalamus are destroyed, unbearable pain occurs; when other nuclei are destroyed, pain sensitivity is completely lost.

Nonspecific nuclei are very similar in function to the reticular formation; they are also called reticular nuclei.

I.I. Sechenov 1864 - discovered the reticular formation, experiments on frogs. He proved that in the central nervous system, along with the phenomena of excitation, there are phenomena of inhibition.

Reticular formation– supports the cortex in a state of wakefulness. Inhibitory influences on the SM.

Corpus callosum– tight bun nerve fibers, connects the hemispheres, ensures their joint work.

Hypothalamus- connected to the pituitary gland. Pituitary– endocrine gland, main. It produces tropic hormones that affect the functioning of other endocrine glands.

Neurosecretory cells of the hypothalamus secrete neurohormones:

Statins - inhibit the production of pituitary tropic hormones

Liberins – enhance the production of pituitary tropic hormones

Functions- the highest center of regulation of the endocrine glands

Neurosecretory cells, the axons of which reach the pituitary gland and secrete hormones into the pituitary gland:

Oxytocin – ensures uterine contractions during childbirth

Antidiuretic hormone– regulates kidney function

The cells of the hypothalamus are sensitive to the level of sex hormones (estrogen and androgen) and, depending on which ones predominate in a person, one or another sexual motivation arises. Hypothalamic cells are sensitive to blood temperature and regulate heat transfer.

The main signal of hunger is the level of glucose in the blood. Only the hypothalamus contains glucoreceptive cells that are sensitive to blood glucose levels. Gathered together to form the center of hunger.

The center of satiety is the emergence of a feeling of satiety.

Example of dysfunction: Bulimia – diseases of the satiety center

Osmoreceptive cells, sensitive to the level of salts in the blood, become excited and a feeling of thirst arises.

At the level of the hypothalamus, only motivations arise, and to fulfill them you need to turn on the cortex.

One of the important formations of the central nervous system involved in the implementation of 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 different sensitive 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.