The limbic system is also called. Emotional Brain: Limbic System

- a set of nerve structures and their connections located in the mediobasal part cerebral hemispheres, involved in the control of autonomic functions and emotional, instinctive behavior, as well as influencing the change in phases of sleep and wakefulness.

The limbic system includes the most ancient part of the cerebral cortex, located on the inner side of the cerebral hemispheres. It includes: hippocampus, cingulate gyrus, amygdala nuclei, piriform gyrus. Limbic formations belong to the highest integrative centers for the regulation of the vegetative functions of the body. Neurons of the limbic system receive impulses from the cortex, subcortical nuclei, thalamus, hypothalamus, reticular formation and all internal organs. Characteristic property The limbic system is the presence of well-defined circular neural connections that unite its various structures. Among the structures responsible for memory and learning, the main role is played by the hippocampus and the associated posterior zones of the frontal cortex. Their activity is important for the transition of short-term memory to long-term memory. The limbic system is involved in afferent synthesis, in the control of electrical activity of the brain, regulates metabolic processes and provides a number of autonomic reactions. Irritation of various parts of this system in an animal is accompanied by manifestations of defensive behavior and changes in the activity of internal organs. The limbic system is also involved in the formation of behavioral reactions in animals. It contains the cortical section of the olfactory analyzer.

Great Peipes circle:

• hippocampus;
• vault;
• mamillary bodies;
• mamillary-thalamic bundle of Vikd Azir;
• thalamus;
• cingulate gyrus.

Small circle of Nauta:

• amygdala;
• end strip;
• partition.

Limbic system and its functions

Consists of phylogenetically old parts of the forebrain. In the name (limbus- edge) reflects the peculiarity of its location in the form of a ring between the neocortex and the terminal part of the brain stem. The limbic system includes a number of functionally combined structures of the midbrain, diencephalon and telencephalon. These are the cingulate, parahippocampal and dentate gyri, hippocampus, olfactory bulb, olfactory tract and adjacent areas of the cortex. In addition, the limbic system includes the amygdala, anterior and septal thalamic nuclei, hypothalamus and mamillary bodies (Fig. 1).

The limbic system has multiple afferent and efferent connections with other brain structures. Its structures interact with each other. The functions of the limbic system are realized on the basis of integrative processes occurring in it. At the same time, individual structures of the limbic system have more or less defined functions.

Rice. 1. The most important connections between the structures of the limbic system and the brain stem: a - circle of Pipetz, b - circle through the amygdala; MT - mamillary bodies

Main functions of the limbic system:

• Emotional and motivational behavior (with fear, aggression, hunger, thirst), which can be accompanied by emotionally charged motor reactions
• Participation in the organization complex shapes behavior such as instincts (food, sexual, defensive)
• Participation in orientation reflexes: reaction of alertness, attention
• Participation in the formation of memory and the dynamics of learning (development of individual behavioral experience)
• Regulation of biological rhythms, in particular changes in the phases of sleep and wakefulness
• Participation in maintaining homeostasis by regulating autonomic functions

Cingulate gyrus

Neurons cingulate cortex receive afferent signals from the association areas of the frontal, parietal and temporal cortex. The axons of its efferent neurons follow to the neurons of the associative cortex of the frontal lobe, hipiocampus, septal nuclei, and amygdala, which are connected to the hypothalamus.

One of the functions of the cingulate cortex is its participation in the formation of behavioral reactions. Thus, when its anterior part is stimulated, aggressive behavior occurs in animals, and after bilateral removal, the animals become quiet, submissive, asocial - they lose interest in other individuals of the group, without trying to establish contact with them.

The cingulate gyrus can have regulatory effects on the functions of internal organs and striated muscles. Its electrical stimulation is accompanied by a decrease in breathing rate, heart contractions, a decrease in blood pressure, increased motility and secretion of the gastrointestinal tract, pupil dilation, and decreased muscle tone.

It is possible that the influence of the cingulate gyrus on animal behavior and the functions of internal organs is indirect and mediated by connections of the cingulate gyrus through the frontal lobe cortex, hippocampus, amygdala and septal nuclei with the hypothalamus and brain stem structures.

It is possible that the cingulate gyrus is related to the formation of pain. In people who had a cingulate gyrus dissection for medical reasons, the feeling of pain decreased.

Determined that neural networks The anterior cingulate cortex is involved in the brain's error detector. Its function is to identify erroneous actions, the progress of which deviates from the program of their execution and actions, upon completion of which the parameters were not achieved final results. Error detector signals are used to trigger error correction mechanisms.

Amygdala

Amygdala located in the temporal lobe of the brain, and its neurons form several subgroups of nuclei, the neurons of which interact with each other and other brain structures. Among these nuclear groups are the corticomedial and basolateral nuclear subgroups.

Neurons of the corticomedial nuclei of the amygdala receive afferent signals from neurons of the olfactory bulb, hypothalamus, thalamic nuclei, septal nuclei, taste nuclei of the diencephalon and pain pathways of the bridge, through which signals from large receptive fields of the skin and internal organs arrive to the neurons of the amygdala. Taking into account these connections, it is assumed that the corticomedial group of tonsil nuclei is involved in the control of the autonomic functions of the body.

Neurons of the basolateral nuclei of the amygdala receive sensory signals from neurons of the thalamus, afferent signals about the semantic (conscious) content of signals from the prefrontal cortex of the frontal lobe, the temporal lobe of the brain and the cingulate gyrus.

Neurons of the basolateral nuclei are connected with the thalamus, the prefrontal part of the cerebral cortex and the ventral part of the striatum of the basal ganglia, therefore it is assumed that the nuclei of the basolateral group of the tonsils are involved in the functions of the frontal and temporal lobes of the brain.

Amygdala neurons send efferent signals along axons predominantly to the same brain structures from which they received afferent connections. Among them are the hypothalamus, the mediodorsal nucleus of the thalamus, the prefrontal cortex, the visual areas of the temporal cortex, the hippocampus, and the ventral part of the striatum.

The nature of the functions performed by the amygdala is judged by the consequences of its destruction or by the effects of its irritation in higher animals. Thus, bilateral destruction of the tonsils in monkeys causes a loss of aggressiveness, a decrease in emotions and defensive reactions. Monkeys with their tonsils removed stay alone and do not seek to come into contact with other animals. In diseases of the tonsils, there is a disconnect between emotions and emotional reactions. Patients may experience and express great concern about any matter, but at this time their heart rate, blood pressure and other autonomic reactions are not changed. It is assumed that the removal of the tonsils, accompanied by a severance of its connections with the cortex, leads to a disruption in the cortex of the processes of normal integration of the semantic and emotional components of efferent signals.

Electrical stimulation of the tonsils is accompanied by the development of anxiety, hallucinations, experiences of previously occurring events, as well as reactions of the SNS and ANS. The nature of these reactions depends on the location of the irritation. When irritating the nuclei of the corticomedial group, reactions from the digestive organs prevail: salivation, chewing movements, bowel movements, urination, and when irritating the nuclei of the basolateral group, reactions of alertness, raising the head, dilating the pupil, and searching. With severe irritation, animals may develop states of rage or, conversely, fear.

In the formation of emotions, an important role is played by the presence of closed circles of circulation of nerve impulses between the formations of the limbic system. A special role in this is played by the so-called limbic circle of Peipetz (hippocampus - fornix - hypothalamus - mamillary bodies - thalamus - cingulate gyrus - parahippocampal gyrus - hippocampus). The streams of nerve impulses circulating along this circular neural circuit are sometimes called the “stream of emotions.”

Another circle (amygdala - hypothalamus - midbrain - amygdala) is important in the regulation of aggressive-defensive, sexual and eating behavioral reactions and emotions.

The tonsils are one of the structures of the central nervous system, the neurons of which have the highest density of sex hormone receptors, which explains one of the changes in the behavior of animals after bilateral destruction of the tonsils - the development of hypersexuality.

Experimental data obtained on animals indicate that one of the important functions of the tonsils is their participation in establishing associative connections between the nature of the stimulus and its significance: the expectation of pleasure (reward) or punishment for actions performed. The neural networks of the tonsils, ventral striatum, thalamus and prefrontal cortex are involved in the implementation of this function.

Hippocampal structures

Hippocampus together with the dentate gyrus ( subiculun) and the olfactory cortex forms a single functional hippocampal structure of the limbic system, located in the medial part of the temporal lobe of the brain. There are numerous two-way connections between the components of this structure.

The dentate gyrus receives its main afferent signals from the olfactory cortex and sends them to the hippocampus. In turn, the olfactory cortex, as the main gate for receiving afferent signals, receives them from various associative areas of the cerebral cortex, hippocampal and cingulate gyri. The hippocampus receives already processed visual signals from the extrastriate areas of the cortex, auditory signals from the temporal lobe, somatosensory signals from the postcentral gyrus, and information from the polysensory association areas of the cortex.

The hippocampal structures also receive signals from other areas of the brain - the brainstem nuclei, raphe nucleus, and locus coeruleus. These signals perform a predominantly modulatory function in relation to the activity of hippocampal neurons, adapting it to the degree of attention and motivation, which are critical to the processes of memorization and learning.

The efferent connections of the hippocampus are organized in such a way that they go mainly to those areas of the brain with which the hippocampus is connected by afferent connections. Thus, efferent signals from the hippocampus follow mainly to the association areas of the temporal and frontal lobes of the brain. To perform their functions, hippocampal structures require constant exchange of information with the cortex and other brain structures.

One of the consequences of bilateral disease of the medial temporal lobe is the development of amnesia - memory loss with a subsequent decrease in intelligence. In this case, the most severe memory impairments are observed when all hippocampal structures are damaged, and less pronounced when only the hippocampus is damaged. From these observations, it was concluded that the hippocampal structures are part of the brain structures, including the medial galamus, cholinergic neuron groups of the base of the frontal lobes, and the amygdala, which play a key role in the mechanisms of memory and learning.

A special role in the implementation of memory mechanisms by the hippocampus is played by the unique property of its neurons to maintain a state of excitation and synaptic signal transmission for a long time after their activation by any influence (this property is called post-tetanic potentiation). Post-tetanic potentiation, which ensures long-term circulation of information signals in closed neural circles of the limbic system, is one of the key processes in the mechanisms of long-term memory formation.

Hippocampal structures play an important role in learning new information and storing it in memory. Information about earlier events is retained in memory after damage to this structure. In this case, hippocampal structures play a role in the mechanisms of declarative or specific memory for events and facts. The mechanisms of non-declarative memory (memory for skills and faces) are largely involved in the basal ganglia, cerebellum, motor areas of the cortex, and temporal cortex.

Thus, the structures of the limbic system take part in the implementation of such complex brain functions as behavior, emotions, learning, and memory. The functions of the brain are organized in such a way that the more complex the function, the more extensive the neural networks involved in its organization. From this it is obvious that the limbic system is only part of the structures of the central nervous system important in the mechanisms of complex brain functions and contributes to their implementation.

Thus, in the formation of emotions as states that reflect our subjective attitude to current or past events, we can distinguish mental (experience), somatic (gestures, facial expressions) and vegetative (vegetative reactions) components. The degree of manifestation of these components of emotions depends on the greater or lesser involvement in emotional reactions of the brain structures with the participation of which they are realized. This is largely determined by which group of nuclei and structures of the limbic system is activated to the greatest extent. The limbic system acts in the organization of emotions as a kind of conductor, enhancing or weakening the severity of one or another component of the emotional reaction.

The involvement of limbic system structures associated with the cerebral cortex in responses enhances the mental component of emotion, and the involvement of structures associated with the hypothalamus and the hypothalamus itself as part of the limbic system enhances the autonomic component of the emotional response. At the same time, the function of the limbic system in organizing emotions in humans is under the influence of the frontal lobe of the brain, which has a corrective effect on the functions of the limbic system. It restrains the manifestation of excessive emotional reactions associated with the satisfaction of simple biological needs and, apparently, contributes to the emergence of emotions associated with the implementation of social relationships and creativity.

The structures of the limbic system, built between the parts of the brain that are directly involved in the formation of higher mental, somatic and autonomic functions, ensure their coordinated implementation, maintenance of homeostasis and behavioral reactions aimed at preserving the life of the individual and the species.

Limbic system (limbicus - border) - a complex of brain structures (Fig. 11) related to emotions, sleep, wakefulness, attention, memory, autonomic regulation, motivation, internal drives; motivation includes complex instinctive and emotional reactions, for example food, defensive And etc. The term “limbic system” was introduced by Mac Lean in 1952.

This system surrounds the brainstem like a membrane. It is commonly called the “olfactory brain” because it is directly connected to the senses of smell and touch. Mood-altering medications specifically target the limbic system, which is why people who take them feel either uplifted or depressed.

The limbic system consists of the thalamus opticus, hypothalamus, pituitary gland, hippocampus, pineal gland, amygdala and reticular formation. The presence of functional connections between limbic structures and the reticular formation allows us to talk about the so-called limbic-reticular axis, which is one of the most important integrative systems of the body.

Optic thalamus(thalamus) - paired formation of the diencephalon. The thalamus of the right hemisphere is separated from the thalamus of the left by the third ventricle. The visual thalamus is a switching “station” of all sensory pathways (pain, temperature, tactile, gustatory, visceral). Each nucleus of the thalamus receives impulses from the opposite side of the body, only the face area has bilateral representations in the visual thalamus. The visual thalamus is also involved in affective-emotional activity. Damage to individual nuclei of the thalamus leads to a decrease in feelings of fear, anxiety and tension, as well as a decrease in intellectual abilities, up to the development of dementia and disruption of the processes of sleep and wakefulness. Clinical symptoms with complete damage to the thalamus are characterized by the development of the so-called “thalamic syndrome”. This syndrome was first described in detail by J. Dejerine and G. Roussy in 1906 and is manifested by a decrease in all types of sensitivity, severe pain on the opposite half of the body and disruption of cognitive processes (attention, memory, thinking, etc.)

Hypothalamus(hypothalamic region) - a section of the diencephalon located downward from the thalamus. The hypothalamus is the highest vegetative center, regulating the functioning of internal organs, many body systems and ensuring the constancy of the internal environment of the body (homeostasis). Homeostasis - maintaining an optimal level of metabolism (protein, carbohydrate, fat, mineral, water), temperature balance of the body, normal functioning of the cardiovascular, respiratory, digestive, excretory and endocrine systems. All endocrine glands, in particular the pituitary gland, are under the control of the hypothalamus. The close relationship between the hypothalamus and the pituitary gland forms a single functional complex - the hypothalamic-pituitary system. The hypothalamus is one of the main structures involved in regulating the cycle of sleep and wakefulness. Clinical studies have shown that damage to the hypothalamus leads to lethargic sleep. From a physiological point of view, the hypothalamus is involved in the formation of behavioral reactions of the body. The hypothalamus plays a major role in the formation of the body’s basic drives (eating, drinking, sexual, aggressive, etc.), motivational and emotional spheres. The hypothalamus is also involved in the formation of such states of the body as hunger, fear, thirst, etc. Thus, the hypothalamus carries out autonomic regulation of internal organs, maintains the constancy of the internal environment of the body, body temperature, controls blood pressure, gives signals about hunger, thirst, fear and is a source of sexual feelings.

Damage to the hypothalamic region and the hypothalamic-pituitary system, as a rule, leads primarily to a violation of the constancy of the internal environment of the body, which is accompanied by a variety of clinical symptoms (increased blood pressure, palpitations, increased sweating and urination, the appearance of a feeling of fear of death, pain in the heart area , disruption of the digestive tract), as well as a number of endocrine syndromes (Itsenko-Cushing, pituitary cachexia, diabetes insipidus, etc.).

Pituitary. It is otherwise called - the brain appendage, the pituitary gland - an endocrine gland that produces a number of peptide hormones that regulate the function of the endocrine glands (genital, thyroid gland, adrenal cortex). A number of hormones of the anterior lobe of the pituitary gland are called triple (somatotropic hormone, etc.). They have to do with growth. Thus, damage to this area (in particular with a tumor - acidophilic adenoma) leads to gigantism or acromegaly. The deficiency of these hormones is accompanied by pituitary dwarfism. Violation of the production of follicle-stimulating and luteinizing hormones is the cause of sexual failure or disorders of sexual function.

Sometimes, after damage to the pituitary gland, disorder of the regulation of sexual functions is combined with disorders of fat metabolism (adipose-genital dystrophy, in which a decrease in sexual function is accompanied by obesity in the pelvic region, thighs and abdomen). In other cases, on the contrary, premature puberty develops. With lesions of the lower parts of the pituitary gland, dysfunction of the adrenal cortex develops, which leads to obesity, increased hair growth, changes in voice, etc. The pituitary gland, closely connected through the hypothalamus with the entire nervous system, unites the endocrine system into a functional whole, which is involved in ensuring the constancy of the internal environment body (homeostasis), in particular the constancy of hormones in the blood and their concentrations.

Since the pituitary gland is the most important link in the system of internal organs, disruption of its function leads to disturbances in the autonomic nervous system, which regulates the functioning of internal organs. The main causes of pituitary gland pathology are tumors, infectious diseases, vascular pathology, skull injuries, sexually transmitted diseases, radiation, pregnancy pathology, congenital insufficiency, etc. Damage to various parts of the pituitary gland leads to a variety of clinical syndromes. Thus, excess production of somatotropic hormone (growth hormone) leads to gigantism or acromegaly, and its deficiency is accompanied by pituitary dwarfism. Violation of the production of follicle-stimulating and luteinizing hormones (sex hormones) is the cause of sexual failure or disorders of sexual function. Sometimes dysregulation of the gonads is combined with a disorder of fat metabolism, which leads to adipose-genital dystrophy. In other cases, premature puberty occurs. Often, pathology of the pituitary gland leads to increased functions of the adrenal cortex, which is characterized by overproduction of adrenocorticotropic hormone and the development of Itsenko-Cushing syndrome. Extensive destruction of the anterior lobe of the pituitary gland leads to pituitary cachexia, in which the functional activity of the thyroid gland and the function of the adrenal cortex decreases. This leads to metabolic disorders and the development of progressive emaciation, bone atrophy, loss of sexual function and atrophy of the genital organs.

Destruction of the posterior lobe of the pituitary gland leads to the development of diabetes insipidus (diabetes insipidus).

Hypoplasia and atrophy - a decrease in the size and weight of the pituitary gland - develop in old age, which leads to arterial hypertension (increased blood pressure) in older people. The literature describes cases of congenital hypoplasia of the pituitary gland with clinical manifestations of pituitary insufficiency (hypopituitarism). People exposed to radiation often develop hyzocorticism (Addisson's disease). Changes in the functioning of the pituitary gland can also be temporary, functional in nature, in particular during pregnancy, when there is hyperplasia of the pituitary gland (increase in its size and weight).

The main clinical symptoms of diseases arising from lesions of the hypothalamic-pituitary complex are described in the section “Clinical features of individual nosological forms”.

Hippocampus translated from Greek - a sea monster with the body of a horse and a fish tail. It is otherwise called the Horn of Ammon. It is a paired formation and is located on the wall of the lateral ventricles. The hippocampus is involved in the organization of the orientation reflex and attention, the regulation of autonomic reactions, motivations and emotions, and in the mechanisms of memory and learning. When the hippocampus is damaged, a person’s behavior changes, it becomes less flexible, difficult to adapt in accordance with changing environmental conditions, and short-term memory is sharply impaired. At the same time, the ability to remember any new information disappears (anterograde amnesia). Thus, the so-called common factor memory - the ability to transition short-term memory into long-term memory.

Pineal body(epiphysis, pineal gland) - an endocrine gland, is an unpaired round formation weighing 170 mg. It is located deep in the brain under the cerebral hemispheres and is adjacent to the back of the third ventricle. The pineal body takes part in the processes of homeostasis, puberty, growth, as well as in the relationship of the internal environment of the body with environment. Hormones of the pineal gland inhibit neuropsychic activity, providing a hypnotic, analgesic and sedative effect. Thus, a decrease in the production of melatonin (the main hormone of the gland) leads to persistent insomnia and the development of a depressive state. Disturbances in the hormonal function of the pineal gland also manifest themselves in increased intracranial pressure, and often in manic-depressive syndrome with severe intellectual disorders.

Amygdala(amygdaloid region) is a complex complex of brain nuclei located deep in the temporal lobe and is the center of “aggression”. Thus, irritation of this area leads to a typical awakening reaction with elements of restlessness, anxiety (the pupils dilate, the heart rate, breathing increases, etc.), and symptoms of the oral complex of movements are also observed - salivation, sniffing, licking, chewing, swallowing. The amygdala also has a significant influence on sexual behavior, leading to hypersexuality. The amygdaloid region also has a certain influence on the higher nervous activity, memory and sensory perception, as well as on the emotional and motivational environment.

Clinical observations show that in patients with epilepsy, convulsive syndrome is often combined with fear, melancholy or severe unmotivated depression. Damage to this area leads to so-called temporal lobe epilepsy, in which symptoms of a psychomotor, autonomic and emotional nature are expressed. In such patients, many basic motivations are disrupted (increased or decreased appetite, hyper- or hyposexuality, attacks of displeasure, unmotivated fear, embitterment, rage, and sometimes aggressiveness).

The limbic system (from the Latin limbus - edge, border) is a collection of a number of nerve formations of the brain located on the border of the new cortex in the form of a ring separating the cortex from the brain stem (Fig. 97). The limbic system is functional association various structures of the telencephalon, diencephalon and midbrain, providing emotional and motivational components of behavior and integration of the visceral functions of the body. The main cortical areas of the limbic system include the hippocampus, parahippocampal gyrus, uncus, cingulate gyrus, and olfactory bulbs. From the subcortical nuclei, the limbic system includes the amygdala (amygdala, amygdala). In addition, the limbic system currently includes a number of nuclei of the thalamus, hypothalamus, and the reticular formation of the midbrain.

A characteristic feature of the limbic system is the presence of well-defined circular nerve connections, uniting its various structures. These connections enable long-term circulation (reverberation) of excitation, increased conductivity of synapses and memory formation. Reverberation of excitation creates conditions for maintaining a single functional state of closed circle structures and imposing this state on other brain structures.

There are several limbic circles. The most important thing is big hippocampal circle of Papez(Papez J. W. 1937), playing a large role in the formation emotions, learning And memory. Another limbic circle is important in the formation of aggressive-defensive, food and sexual reactions (Fig. 98).

The limbic system receives information about the external and internal environment of the body through various areas of the brain, through the hypothalamus from the reticular formation, as well as from almost all sense organs. In the structures of the limbic system (in the hook) there is the cortical section of the olfactory analyzer. Because of this, the limbic system was previously called the “olfactory brain.”

The limbic system ensures the interaction of exteroceptive influences received from the external environment and interoceptive influences. After comparing and processing the received information, the limbic system sends nerve impulses to the underlying nerve centers and triggers autonomic, somatic and behavioral reactions that provide adaptation of the body to the external environment And maintaining homeostasis.

The body’s adaptation to the external environment is carried out thanks to the regulation of visceral functions by the limbic system, and therefore the limbic system is sometimes called the “visceral brain”. This regulation is carried out mainly through the activity of the hypothalamus. In this case, the effects can manifest themselves in the form of both activation and inhibition of visceral functions: there is an increase or decrease in heart rate, peristalsis and secretion of the stomach and intestines, secretion of various hormones by the adenohypophysis, etc.

The most important function of the limbic system is formation of emotions, which reflect a person’s subjective attitude to the objects of the surrounding world and the results of his own activities. Emotions are closely related to motivations that trigger and implement behavior aimed at satisfying emerging needs.

In the structure of emotions, emotional experiences themselves are distinguished and peripheral ones, i.e. vegetative and somatic manifestations. The structure responsible primarily for vegetative manifestations of emotions is hypothalamus. In addition to the hypothalamus, the structures of the limbic system most closely associated with emotions include amygdala And cingulate gyrus.

Electrical stimulation of the amygdala in humans most often causes negative emotions - fear, anger, rage. Along with this, the amygdala is involved in the process of identifying the dominant emotion, as well as motivation, thus influencing the choice of behavior. The functions of the cingulate cortex are less studied. It is assumed that the cingulate gyrus, which has numerous connections both with the neocortex and with the centers of the brain stem, plays the role of the main integrator of various brain systems that form emotions.

Another important function of the limbic system is its participation in memory processes And implementation of training. This function is predominantly associated with the greater hippocampal circle of Papez. Main role play a role in memory and learning hippocampus and associated posterior areas of the frontal cortex. They carry out memory consolidation, i.e. transition of short-term memory to long-term memory. Damage to the hippocampus in humans leads to a sharp disruption in the assimilation of new information, the formation of intermediate and long-term memory, and the formation of skills. In addition, old skills are lost, and recall of previously learned information becomes difficult.

Electrophysiological studies of the hippocampus have revealed two characteristics. Firstly, in response to sensory stimulation, stimulation of the reticular formation and the posterior nuclei of the hypothalamus, synchronization of electrical activity develops in the hippocampus in the form of low-frequency theta rhythm(θ rhythm) with a frequency of 4–7 Hz. It is assumed that this rhythm is evidence of the participation of the hippocampus in orientation reflexes, reactions of attention, alertness, and the development of emotional stress.

The second electrophysiological feature of the hippocampus is its ability to respond to stimulation for a long time (for hours, days and even weeks) post-tetanic potentiation, which leads to facilitation of synaptic transmission and is the basis for memory formation. The participation of the hippocampus in memory processes is also confirmed by electron microscopic studies. It has been established that in the process of memorizing information there is an increase in the number of spines on the dendrites of hippocampal pyramidal neurons, which indicates an expansion of synaptic connections.

Thus, the limbic system is involved in the regulation of vegetative-visceral-hormonal functions aimed at ensuring various forms activities (eating and sexual behavior, species preservation processes), in the regulation of systems that ensure sleep and wakefulness, attention, emotional sphere, memory processes, carrying out somatovegetative integration.

5.20. Autonomic nervous system

5.20.1. Structural functional features autonomic nervous system, its sympathetic and parasympathetic divisions

The autonomic nervous system is the part of the nervous system that regulates and coordinates the activity of internal organs, metabolism, smooth muscles, endocrine glands, the constancy of the internal environment of the body and the functional activity of tissues. The ANS innervates the entire body, all organs and tissues. The structural and functional features of the ANS gave certain grounds to consider it as “autonomous”, i.e. independent in its functions from the activity of the central nervous system and from the will of a person. However, the idea of ​​the autonomy of the autonomic nervous system is very conditional. At present, there is no doubt that through the ANS, the central nervous system performs the most important functions: 1) regulates the functions of internal organs, as well as the blood supply and trophism of all tissues of the body; 2) provides the energy needs of various forms of mental and physical activity (changes in the intensity of metabolic processes, the functioning of the cardiovascular and respiratory systems, etc.).

Autonomic reflex arcs are built according to the same plan as somatic ones, and contain sensory, intercalary and efferent links. At the same time, the reflex arcs of the ANS have a number of differences from the arcs of somatic reflexes. 1. The cell bodies of ANS effector neurons lie in ganglia outside the central nervous system. 2. The reflex arc of the ANS can close outside the central nervous system in extra- and intraorgan (intramural) ganglia. 3. The arc of the central autonomic reflex, i.e. closing in the spinal cord or brain includes at least four neurons: sensory, intercalary, preganglionic and postganglionic. The arc of the peripheral autonomic reflex, i.e. closing in the ganglion, can consist of two neurons: afferent and efferent. 4. The afferent part of the autonomic reflex arc can be formed by both its own autonomic and somatic sensory nerve fibers.

In the autonomic nervous system there are sympathetic division, or sympathetic nervous system, and parasympathetic division, or parasympathetic nervous system (Fig. 99). Sometimes the metasympathetic part of the ANS is also isolated. The sphere of innervation of the metasympathetic part of the ANS covers only those internal organs that have their own motor rhythm, for example, the stomach and intestines.

The sympathetic and parasympathetic sections of the ANS differ from each other: 1) in the location of the centers in the brain from which nerve fibers go to the organs; 2) according to the proximity of the ganglia to the target organs; 3) by the transmitter, which is used by postganglionic neurons at synapses on the cells of target organs to regulate their functions; 4) by the nature of the effects on internal organs.

The peripheral part of the ANS is characterized by diffuse distribution of excitation. This is due to the phenomenon animations in the autonomic ganglia, mainly in the sympathetic ones, as well as multiple branching in the organs of the endings of the postganglionic nerves. The number of efferent (postganglionic) neurons in the sympathetic ganglia is 10–30 times greater than the number of preganglionic fibers entering the nodes. Therefore, each preganglionic fiber forms synapses on several ganglionic neurons, which ensures divergence of excitation and a generalized effect on the innervated organs.

Due to the long synaptic delay (about 10 ms) and prolonged trace depolarization, autonomic ganglion neurons have low lability. They are capable of reproducing only 10–15 impulses per second, while in motor neurons of the somatic nervous system this value can reach 200 impulses/s.

Preganglionic fibers of the ANS are type B, have a diameter of 2–3.5 μm, are covered with a thin myelin sheath and conduct impulses at a speed of 3 to 18 m per second. Postganglionic fibers belong to type C, have a diameter of up to 2 µm, most of them are not covered with a myelin sheath. The speed of propagation of nerve impulses through them is from 1 to 3 m per second.

The sympathetic and parasympathetic divisions of the ANS interact with each other at different levels: at the effector cell, at the level of nerve endings, in the autonomic ganglia and at the central level. Thus, the presence of sympathetic and parasympathetic innervation in the effector cell provides the opportunity for this cell to carry out opposite reactions. In the heart, gastrointestinal tract, and bronchial muscles, reciprocal inhibition of mediator release from adrenergic and cholinergic nerve endings can be observed. The sympathetic ganglia contain M-cholinergic receptors, the excitation of which inhibits transmission from preganglionic sympathetic fibers to ganglionic neurons. At the level of autonomic centers, the interaction is manifested in the fact that excitation of the sympathetic nervous system during emotional and physical stress simultaneously leads to a decrease in the tone of the parasympathetic nervous system. In other cases, for example in the regulation of heart function, the increased tone of the parasympathetic department is replaced by increased activity of the sympathetic department of the ANS.

The sympathetic nervous system innervates all organs and tissues of the body, including skeletal muscles and the central nervous system. The sympathetic and parasympathetic divisions of the ANS, as a rule, have opposite effects on organs. For example, when the sympathetic nerves are excited, the heart rate accelerates, and under the influence of the parasympathetic (vagus) nerves it slows down. Due to the multidirectional influence of the two sections of the ANS on the activity of organs, a better adaptation of the body to living conditions is ensured.

With the participation of the sympathetic department of the ANS, reflex reactions occur aimed at ensuring active state of the body, including motor activity. There is an expansion of the bronchi, heart vessels and skeletal muscles, heartbeats intensify and become more frequent, blood is expelled from the depot, the glucose content in the blood increases, the work of the endocrine and sweat glands intensifies, etc. At the same time, the processes of urination and digestion decrease, acts of urination, defecation, etc. are prevented. The body's reserves are mobilized, thermoregulation processes are activated, blood clotting mechanisms, immune defense reactions. In this regard, the sympathetic nervous system is figuratively called the “fight or flight system.”

The sympathetic nervous system has a diffuse and generalized effect on the functions of the body due to the intensive branching of sympathetic fibers. For example, in various emotional states of the body (fear, anger, malice), when the sympathetic nervous system is excited, an increase in heart contractions, dry mouth, dilated pupils, etc. are simultaneously observed. A generalized effect on almost all structures of the body also occurs when adrenaline is released into the blood from the adrenal medulla, which is innervated by sympathetic nerves.

The sympathetic nervous system not only regulates the functioning of internal organs, but also influences metabolic processes occurring in skeletal muscles and the nervous system. This was first established by L.A. Orbeli and got the name adaptive-trophic function sympathetic nervous system. The adaptation-trophic influence of sympathetic nerves on skeletal muscles is of great importance for the motor activity of the body. Thus, small contractions of a tired muscle can increase again when the sympathetic nervous system is excited - Orbeli-Ginetzinsky effect. It was also found that stimulation of sympathetic fibers can significantly change receptor excitability and even the functional properties of the central nervous system. Consequently, due to the trophic influence of the sympathetic nervous system, the specific functions of organs and tissues are carried out better and more fully, and the performance of the body increases.

Removal of the sympathetic nervous system in animals or drug shutdown in humans in some forms of persistent hypertension is not accompanied by significant functional disorders. However, in extreme conditions that require strain on the body, after removal of the sympathetic nervous system, significantly less endurance and often death of animals are found.

The function of the parasympathetic nervous system is Active participation V body recovery processes after the active state, ensuring processes, stabilizing the internal environment of the body over a long period of time. The influences of parasympathetic nerves can affect either directly the innervated organs, as in the circular muscles of the iris or in the salivary glands, or through the neurons of the intramural ganglia, including the metasympathetic part of the ANS. In the first case, postganglionic parasympathetic fibers themselves are in direct contact with the cells of the working organ and the action they cause, as a rule, opposite to the influence of the sympathetic nerves. For example, irritation of the parasympathetic vagus nerve causes a decrease in the frequency and strength of the heartbeat, narrowing of the bronchi, increased motility of the stomach and intestines, and other effects.

On organs that contain intramural ganglia of the metasympathetic part of the ANS, the parasympathetic nervous system can have (depending on the functional state of the innervated organ) both excitatory and inhibitory effects.

Due to the parasympathetic nervous system, reflex reactions of a protective nature are carried out, for example, constriction of the pupil during a flash of bright light. Reflex reactions occur aimed at preserving the composition and properties of the internal environment of the body (excitation of the vagus nerve stimulates the digestive processes and thereby ensures the restoration of the level of nutrients in the body). The parasympathetic nervous system has triggering effects on the activity of organs, promoting the emptying of the gallbladder, urination, defecation, etc.

Limbic system (synonym: limbic complex, brain, rhinencephalon, thymencephalon)

a complex of structures of the midbrain, diencephalon and telencephalon involved in the organization of visceral, motivational and emotional reactions of the body.

The main part of the structures of HP. consist of brain formations related to the ancient, old and new cortex, located mainly on the medial surface of the cerebral hemispheres, as well as numerous subcortical structures closely associated with them.

On initial stage development of vertebrate animals HP provided all the most important reactions of the body (food, orientation, sexual, etc.), formed on the basis of the most ancient distant sense - smell (Oolfaction) . It acted as an integrating factor for many integral functions of the body and united the structures of the telencephalon, diencephalon and midbrain into a single morphofunctional complex. A number of structures of L.S. forms closed systems based on ascending and descending pathways.

Morphologically L.s. in higher mammals includes ( rice. 1 ) areas of the old cortex (cingulate, or limbic, gyrus), some formations of the new cortex (temporal and frontal regions, intermediate frontotemporal zone), subcortical structures (caudate, putamen, septum, reticular formation of the midbrain, nonspecific nuclei of the thalamus) .

Structures HP participate in the regulation of the most important biological needs related to the production of energy and plastic materials, maintaining water and salt balance, optimizing body temperature, etc.

It has been experimentally proven that the emotional state of an animal when certain areas of the HP are stimulated. manifested primarily by reactions of aggression (anger), flight (fear) or observed mixed forms behavior such as defensiveness. Emotions, unlike motivations, arise in response to sudden changes in the environment and serve as a tactical task of behavior. Therefore, they are fleeting and optional. Long-term unmotivated changes in emotional behavior may be a consequence of organic pathology or the action of certain neuroleptics. In different departments of L.S. centers of “pleasure” and “displeasure” have been opened, combined into systems of “reward” and “punishment”. When stimulated, the “punishment” system behaves in the same way as in case of fear or pain, and when stimulated, the “reward” system tends to resume and carries it out independently if such an opportunity arises. Reward effects are not directly related to the regulation of biological motivations or inhibition of negative emotions and most likely represent a nonspecific mechanism of positive reinforcement, the activity of which is perceived as pleasure or reward. This general nonspecific positive reinforcement is connected to various motivational mechanisms and ensures the direction of behavior based on the “better - worse” principle.

Visceral reactions when exposed to HP are, as a rule, a specific component of the corresponding type of behavior. Thus, when the hunger center is stimulated in the lateral parts of the hypothalamus, abundant, increased motility and secretory activity of the gastrointestinal tract are observed; when provoking sexual reactions - ejaculation, etc., and against the background of different types of motivational and emotional behavior, changes in breathing, heart rate and the magnitude, secretion, catecholamines, other hormones and mediators are recorded,

To explain the principles of integrative activity L.s. put forward the cyclical nature of excitation processes in a closed network of structures, including the hippocampus, mammillary bodies, brain, anterior nuclei of the thalamus, cingulate gyrus - the so-called Papes circle ( rice. 2 ). Then it resumes. This “transit” principle of organizing the functions of HP. is confirmed by a number of facts. For example, food reactions can be evoked by stimulating the lateral nucleus of the hypothalamus, the lateral preoptic area and some other structures. Nevertheless, despite the multiplicity of localization of functions, it was possible to identify key, or pacemaker, mechanisms, the shutdown of which leads to a complete loss of function.

Currently, the problem of consolidating structures into a specific functional system is being solved from the perspective of neurochemistry. It has been shown that many formations of H.S. contain cells and terminals that secrete several types of biologically active substances. Among them, the most studied are monoaminergic neurons, forming three systems: dopaminergic, noradrenergic and serotonergic (see Mediators) . Neurochemical affinity of individual structures of HP. largely determines the degree of their participation in a particular type of behavior. The activity of the reward system is ensured by noradrenergic and dopaminergic mechanisms; the corresponding cellular receptors with drugs from a number of phenothiazines or bugarophenones is accompanied by emotional and motor retardation, and with excessive dosages - depression and motor disorders close to parkinsonism syndrome. In the regulation of sleep and wakefulness, along with monoaminergic mechanisms, GABAergic and neuromodulatory mechanisms that specifically respond to gamma-aminobutyric acid () and delta sleep peptide are involved. The endogenous opiate system and morphine-like substances - and enkephalins - play a key role in pain mechanisms (see Regulatory peptides) .

Violations of HP functions manifest themselves in various diseases (brain trauma, intoxication, neuroinfections, vascular pathology, endogenous psychoses, neuroses) and are extremely diverse in clinical picture. Depending on the location and extent of the lesion, these disorders may be related to motivation, emotions, autonomic functions and can be combined in different proportions. Low thresholds of convulsive activity HP. determine different shapes epilepsy: large and small forms of convulsive seizures, automatisms, changes in consciousness (and derealization), vegetative paroxysms, which are preceded or accompanied by various forms of mood changes in combination with olfactory, gustatory and auditory hallucinations.

olfactory bulb; 3 - ; 4 - front; 5 - ; 6 - waist; 7 - anterior nuclei of the thalamus; 8 - end strip; 9 - cerebral vault; 10 - medullary strip; 11 - nuclei of the habenular complex; 12 - interpeduncular nucleus; 13 - mastoid nucleus; 14 - amygdaloid region">

Rice. 1. Schematic representation of the main structures of the human limbic system and the connections between them (indicated by arrows and dotted lines): 1 - cells of the olfactory epithelium; 2 - olfactory bulb; 3 - olfactory tract; 4 - anterior commissure; 5 - callosum; 6 - cingulate gyrus; 7 - anterior nuclei of the thalamus; 8 - end strip; 9 - cerebral vault; 10 - medullary strip; 11 - nuclei of the habenular complex; 12 - interpeduncular nucleus; 13 - mastoid nucleus; 14 - amygdaloid region.

Rice. 2a). Morphofunctional characteristics of the limbic system - a schematic representation of the structures of the limbic system (indicated in a darker color; in the center - the so-called Peips circle): 1 - cingulate gyrus; 2 - precuneus; 3 - parahippocampal gyrus (arrows show relationships between structures).

bark; blue arrows indicate morphological connections of the Peips circle, purple arrows indicate connections that are not included in it">

Rice. 2b). Morphofunctional characteristics of the limbic system - a diagram of the interaction of the structures of the Papes circle: 1 - amygdaloid region; 2 - olfactory system; 3 - partition; 4 - fornix 5 - cingulate gyrus 6 - hippocampus 7 - anterior nucleus of the thalamus 8 - hypothalamus 9 - entorhinal cortex; blue arrows indicate morphological connections of the Peips circle, purple arrows indicate connections that are not included in it.

1. Small medical encyclopedia. - M.: Medical encyclopedia. 1991-96 2. First health care. - M.: Great Russian Encyclopedia. 1994 3. Encyclopedic Dictionary medical terms. - M.: Soviet Encyclopedia. - 1982-1984.

• Limbic region

See what the “Limbic system” is in other dictionaries:

In the brain. The limbic system (from the Latin limbus border, edge) is a collection of a number of brain structures. Participates in the regulation of the functions of internal organs, smell, instinctive behavior, emotions, memory, sleep, wakefulness and... ... Wikipedia

LIMBIC SYSTEM, a complex of structures within the BRAIN. The limbic system is located in a semicircle around the HYPOTHALAMUS. It is believed to be involved in emotional reactions such as fear, aggression and mood changes, as well as... ... Scientific and technical encyclopedic dictionary

- (from the Latin limbus border), limbic lobe, a set of a number of brain structures (terminal, intermediate and middle sections), united according to anatomical and functional signs. Includes phylogenetically young cortical structures... ... Biological encyclopedic dictionary

A collection of a number of brain structures. Participates in the regulation of the functions of internal organs, smell, instinctive behavior, emotions, memory, sleep, wakefulness, etc... Big Encyclopedic Dictionary

A collection of a number of brain structures. Participates in the regulation of the functions of internal organs, smell, instinctive behavior, emotions, memory, sleep, wakefulness, etc. * * * LIMBIC SYSTEM LIMBIC SYSTEM, a combination of a number of structures... ... encyclopedic Dictionary

Limbic system- a complex of structures of the final, intermediate and middle parts of the brain, constituting the substrate for the manifestation of the most general states of the body (sleep, wakefulness, emotions, motivation, etc.). The term “limbic system” was introduced by P. Mac Lane in... ... Human psychology: dictionary of terms

Limbic system- (lat. limbus edge, border) - a system that is formed by evolutionarily relatively old formations of the forebrain and is located in the depression under the corpus callosum. It includes: 1. hippocampus, 2. amygdala, 3. olfactory... ... Encyclopedic Dictionary of Psychology and Pedagogy

- (from the Latin limbus border) olfactory, or visceral, brain, a set of parts of the brain, united by anatomical (spatial relationship) and functional (physiological) characteristics. The main part of HP... ... Great Soviet Encyclopedia

A collection of a number of brain structures. Participates in the regulation of internal functions. organs, smell, instinctive behavior, emotions, memory, sleep, wakefulness, etc... Natural science. encyclopedic Dictionary

2. Self-regulation of autonomic functions

3. The role of the limbic system in the formation of motivations, emotions, memory organization

Conclusion

References

Introduction

There are six lobes in each of the two hemispheres of the brain: the frontal lobe, the parietal lobe, the temporal lobe, the occipital lobe, the central (or insular) lobe, and the limbic lobe. A set of formations located predominantly on the inferomedial surfaces of the cerebral hemispheres, closely interconnected with the hypothalamus and overlying structures, was first designated as an independent formation (limbic lobe) in 1878 by the French anatomist Paul Broca (1824-1880). Then only the marginal zones of the cortex, located in the form of a bilateral ring on the inner border of the neocortex (Latin: limbus - edge), were classified as the limbic lobe. These are the cingulate and hippocampal gyri, as well as other areas of the cortex located next to the fibers coming from the olfactory bulb. These zones separated the cerebral cortex from the brain stem and hypothalamus.

At first it was believed that the limbic lobe performed only the function of smell and therefore it was also called the olfactory brain. Subsequently, it was found that the limbic lobe, together with a number of other neighboring brain structures, perform many other functions. These include coordination (organization of interaction) of many mental (for example, motivations, emotions) and physical functions, coordination of visceral systems and motor systems. In this regard, this set of formations was designated by the physiological term - limbic system.

1. The concept and significance of the limbic system in nervous regulation

The occurrence of emotions is associated with the activity of the limbic system, which includes some subcortical formations and areas of the cortex. The cortical sections of the limbic system, representing its highest section, are located on the lower and inner surfaces of the cerebral hemispheres (cingulate gyrus, hippocampus, etc.). The subcortical structures of the limbic system include the hypothalamus, some nuclei of the thalamus, midbrain and reticular formation. Between all these formations there are close direct and feedback connections that form the “limbic ring”.

The limbic system is involved in a wide variety of activities of the body. It forms positive and negative emotions with all their motor, autonomic and endocrine components (changes in breathing, heart rate, blood pressure, activity of the endocrine glands, skeletal and facial muscles, etc.). Emotional coloring depends on it mental processes and changes in motor activity. It creates motivation for behavior (a certain predisposition). The emergence of emotions has an “evaluative influence” on the activity of specific systems, since, by reinforcing certain methods of action, ways of solving assigned tasks, they ensure the selective nature of behavior in situations with many choices.

The limbic system is involved in the formation of indicative and conditioned reflexes. Thanks to the centers of the limbic system, defensive and food conditioned reflexes can be produced even without the participation of other parts of the cortex. With lesions of this system, strengthening of conditioned reflexes becomes difficult, memory processes are disrupted, selectivity of reactions is lost and their excessive strengthening is noted (excessively increased motor activity, etc.). It is known that the so-called psychotropic substances that change the normal mental activity of a person act specifically on the structures of the limbic system.

Electrical stimulation of various parts of the limbic system through implanted electrodes (in experiments on animals and in the clinic during the treatment of patients) revealed the presence of pleasure centers that form positive emotions, and centers of displeasure that form negative emotions. Isolated irritation of such points in the deep structures of the human brain caused the appearance of feelings of “causeless joy,” “pointless melancholy,” and “unaccountable fear.”

In special experiments with self-irritation on rats, the animal was taught to close a circuit by pressing its paw on a pedal and produce electrical stimulation of its own brain through implanted electrodes. When the electrodes are localized in the centers of negative emotions (some areas of the thalamus), the animal tries to avoid closing the circuit, and when they are located in the centers of positive emotions (hypothalamus, midbrain), the paw presses the pedal almost continuously, reaching up to 8 thousand irritations in 1 hour.

The role of emotional reactions in sports is great (positive emotions when performing physical exercises - “muscular joy”, the joy of victory and negative ones - dissatisfaction with the sports result, etc.). Positive emotions can significantly increase, and negative emotions can significantly decrease, a person’s performance. The great stress that accompanies sports activity, especially during competitions, also creates emotional stress - the so-called emotional stress. The success of an athlete’s motor activity depends on the nature of the reactions of emotional stress in the body.

The regulation of the activity of internal organs is carried out by the nervous system through its special department - the autonomic nervous system.

All functions of the body can be divided into somatic, or animal (from the Latin animal - animal), associated with the activity of skeletal muscles, - organization of posture and movement in space, and vegetative (from the Latin vegetativus - plant), associated with the activity of internal organs, -processes of respiration, blood circulation, digestion, excretion, metabolism, growth and reproduction. This division is arbitrary, since vegetative processes are also inherent in the motor system (for example, metabolism, etc.); motor activity is inextricably linked with changes in breathing, blood circulation, etc.

Stimulation of various body receptors and reflex responses of nerve centers can cause changes in both somatic and autonomic functions, i.e., the afferent and central sections of these reflex arcs are common. Only their efferent sections are different.

The totality of efferent nerve cells of the spinal cord and brain, as well as cells of special nodes (ganglia) innervating internal organs, is called the autonomic nervous system. Consequently, this system is the efferent part of the nervous system, through which the central nervous system controls the activities of the internal organs.

A characteristic feature of the efferent pathways included in the reflex arcs of autonomic reflexes is their two-neuron structure. From the body of the first efferent neuron, which is located in the central nervous system (in the spinal, medulla oblongata or midbrain), a long axon extends, forming a prenodal (or preganglionic) fiber. In the autonomic ganglia - clusters of cell bodies outside the central nervous system - excitation switches to the second efferent neuron, from which a postnodal (or postganglionic) fiber departs to the innervated organ.

The autonomic nervous system is divided into 2 sections - sympathetic and parasympathetic. The efferent pathways of the sympathetic nervous system begin in the thoracic and lumbar parts of the spinal cord from the neurons of its lateral horns. The transfer of excitation from the prenodal sympathetic fibers to the postnodal ones occurs in the ganglia of the border sympathetic trunks with the participation of the mediator acetylcholine, and the transfer of excitation from the postnodal fibers to the innervated organs - with the participation of the mediator adrenaline, or sympathin. The efferent pathways of the parasympathetic nervous system begin in the brain from some nuclei of the midbrain and medulla oblongata and from neurons of the sacral spinal cord. Parasympathetic ganglia are located in close proximity to or within the innervated organs. The conduction of excitation at the synapses of the parasympathetic pathway occurs with the participation of the mediator acetylcholine.

The autonomic nervous system, by regulating the activity of internal organs, increasing the metabolism of skeletal muscles, improving their blood supply, increasing the functional state of nerve centers, etc., contributes to the implementation of the functions of the somatic and nervous system, which ensures the active adaptive activity of the body in the external environment (reception of external signals, their processing, motor activity aimed at protecting the body, searching for food, in humans - motor acts associated with household, work, sports activities, etc.). The transmission of nervous influences in the somatic nervous system occurs at high speed (thick somatic fibers have high excitability and a conduction speed of 50-140 m/sec). Somatic effects on individual parts of the motor system are characterized by high selectivity. The autonomic nervous system is involved in these adaptive reactions of the body, especially under extreme stress (stress).

Another significant aspect of the activity of the autonomic nervous system is its huge role in maintaining the constancy of the internal environment of the body.

The constancy of physiological parameters can be ensured in various ways. For example, the constancy of blood pressure is maintained by changes in the activity of the heart, pro. light of blood vessels, the amount of circulating blood, its redistribution in the body, etc. In homeostatic reactions, along with nervous influences transmitted through vegetative fibers, humoral influences are important. All these influences, unlike somatic ones, are transmitted in the body much more slowly and more diffusely. Thin autonomic nerve fibers are characterized by low excitability and low speed of excitation conduction (in prenodal fibers the conduction speed is 3-20 m/sec, and in postnodal fibers it is 0.5-3 m/sec).