Limbic system: concept, functions. How is it related to our emotions?

What is the limbic system of the brain? What does it consist of? Joy, fear, anger, sadness, disgust. Emotions. Despite the fact that we sometimes feel overwhelmed by their intensity, but in fact, life without them is impossible. What would we do, for example, without fear? Perhaps we would turn into reckless suicides. This article explains what the limbic system is, what it is responsible for, what its functions, components and possible states are. What does the limbic system have to do with our emotions?

What is the limbic system? Since the time of Aristotle, scientists have been studying the mysterious world human emotions. Historically, this area of ​​science has always been the subject of much controversy and intense debate; until the scientific world came to recognize that emotions are an integral part of human nature. Indeed, science is now confirming that there is a brain structure, namely the limbic system, that regulates our emotions.

The term "limbic system" was proposed by the American scientist Paul D. McLean in 1952 as a neural substrate for emotions (McLean, 1952). He also proposed the concept of a triune brain, according to which the human brain consists of three parts, planted one on top of the other, like in a nesting doll: ancient brain(or reptilian brain), midbrain (or limbic system) and neocortex (bark hemispheres).

Components of the limbic system

What is the limbic system of the brain made up of? What is its physiology? The limbic system has many centers and components, but we will focus only on those that have the most significant functions: the amygdala (hereinafter referred to as the amygdala), the hippocampus, the hypothalamus, and the cingulate gyrus.

“The hypothalamus, the nucleus of the anterior cingulate gyrus, the cingulate gyrus, the hippocampus and its connections are a well-coordinated mechanism that is responsible for central emotional functions, and also takes part in the expression of emotions.” James Peipets, 1937

Functions of the limbic system

Limbic system and emotions

The limbic system in the human brain next function. When we talk about emotions, automatically we have a feeling of some rejection. It's about about the association that still takes place from the time when the concept of emotions looked like something dark, clouding the mind and intellect. Some groups of researchers have argued that emotions bring us down to the level of animals. But in fact, this is absolutely true, because, as we will see later, emotions (not so much in themselves, but in the system that they activate) help us survive.

Emotions have been defined as interrelated responses evoked by situations of reward and punishment. Rewards, for example, promote responses (satisfaction, comfort, well-being, etc.) that attract animals to adaptive stimuli.

Autonomic responses and emotions depend on the limbic system: the relationship between emotions and autonomic responses (body changes) is important. Emotions are essentially a dialogue between the brain and the body. The brain detects a significant stimulus and sends information to the body so that it can respond to these stimuli in the appropriate way. The last step is that the changes in our body happen consciously, and thus we acknowledge our own emotions. For example, fear and anger responses start in the limbic system, which causes a diffuse effect on the sympathetic nervous system. The bodily response, known as “fight or flight,” prepares a person for threatening situations so that he can defend or flee, depending on the circumstances, by increasing his heart rate, breathing and blood pressure. Fear depends on the limbic system: fear reactions are formed as a result stimulation of the hypothalamus and amygdala. That is why destruction of the amygdala eliminates the fear response and its associated bodily effects. The amygdala is also involved in fear-based learning. Similarly, neuroimaging studies show that fear activates the left amygdala. Anger and calmness are also functions of the limbic system: anger responses to minimal stimuli are observed after removal of the neocortex. Destruction of some areas of the hypothalamus, as well as the ventromedial nucleus and septal nuclei, also causes an anger response in animals. Anger can also be generated through stimulation of wider areas of the midbrain. Conversely, bilateral destruction of the amygdala impairs anger responses and leads to excessive calmness. Pleasure and addiction originate in the limbic system: neural networks, which are responsible for pleasure and addictive behavior, are included in the structure of the amygdala, nucleus accumbens and hippocampus. These circuits are involved in the motivation to use drugs, determine the nature of impulsive consumption and possible relapses. Learn more about the benefits of cognitive rehabilitation for addiction treatment.

Non-Emotional Functions of the Limbic System

The limbic system is involved in the formation of other processes associated with survival. Its neural networks are widely described in the scientific literature, specializing in functions such as sleep, sexual behavior, or memory.

As you might expect, memory is another important function we need to survive. Although there are other types of memory, emotional memory refers to stimuli or situations that are vital. The amygdala, prefrontal cortex, and hippocampus are involved in the acquisition, maintenance, and removal of phobias from our memory. For example, the fear of spiders that people have in order to ultimately make it easier for them to survive.

The limbic system also controls eating behavior, appetite and the functioning of the olfactory system.

Clinical manifestations. Limbic system disorders

1- Dementia

The limbic system is linked to the causes of neurodegenerative diseases, in particular Alzheimer's disease and Pick's disease. These pathologies are accompanied by atrophy in the limbic system, especially in the hippocampus. In Alzheimer's disease, senile plaques and neurofibrillary plexuses (tangles) appear.

2- Anxiety

Anxiety disorders are the result of disturbances in the regulation of amygdala activity. The scientific literature has detailed the fear circuit that involves the amygdala, the prefrontal cortex, and the anterior cingulate cortex of the brain. (Cannistraro, 2003).

3- Epilepsy

Epilepsy can manifest itself as a consequence of changes in the limbic system. Temporal lobe epilepsy is most common in adults and occurs as a result of sclerosis in the hippocampus. It is believed that this type of epilepsy is associated with dysfunction at the level of the limbic system.

4- Mood disorders

There are studies that show a change in the volume of the limbic system in connection with affective disorders, such as bipolar disorder and depression. Functional studies have shown a decrease in activity in the prefrontal cortex and anterior cingulate cortex in affective disorders. The anterior cingulate cortex is the focus of attention and emotional integration, and is also involved in the regulation of emotions.

5- Autism

Autism and Asperger's syndrome lead to changes in social aspects. Some structures of the limbic system, such as the cingulate gyrus and the amygdala, undergo negative changes in these diseases.

Translation by Alexandra Dyuzheva

Notes:

Cannistraro, P.A., and Rauch, S.L. (2003). Neural circuitry of anxiety: Evidence from structural and functional neuroimaging studies. Psychopharmacol Bull, 37, 8–25

Rajmohan, V., y Mohandas, E. (2007). The limbic system. Indian Journal of Psychiatry 49(2):132-139

Maclean PD. The triune brain in evolution: Role in paleocerebral functions. New York: Plenum Press; 1990

Roxo, M.; Franceschini, P.R.; Zubaran, C.; Kleber, F.; and Sander, J. (2011). The Limbic System Conception and Its Historical Evolution. TheScientificWorldJOURNAL, 11, 2427–2440

Morgane, P.J., y Mokler, D.J. (2006). The limbic system: contiuing resolution. Neuroscience and Biobehavioral Reviews, 30: 119–125

In this article, we will talk about the limbic system, the neocortex, their history of origin and main functions.

limbic system

The limbic system of the brain is a collection of complex neuroregulatory structures of the brain. This system is not limited to just a few functions - it performs a huge number of the most important tasks for a person. The purpose of the limbus is the regulation of higher mental functions and special processes of higher nervous activity ranging from simple charm and wakefulness to cultural emotions, memory and sleep.

History of occurrence

The limbic system of the brain formed long before the neocortex began to form. This is ancient hormonal-instinctive structure of the brain, which is responsible for the survival of the subject. For a long evolution, 3 main goals of the system for survival can be formed:

• Dominance - a manifestation of superiority in a variety of ways
• Food - subject nutrition
• Reproduction is the transfer of one's genome to the next generation.

Because a person has animal roots, a limbic system is present in the human brain. Initially, Homo sapiens had only affects that affect the physiological state of the body. Over time, communication was formed by the type of cry (vocalization). Individuals who knew how to convey their state with the help of emotions survived. Over time, an emotional perception of reality has been formed more and more. Such evolutionary stratification allowed people to unite into groups, groups into tribes, tribes into settlements, and the latter into entire peoples. The limbic system was first discovered by American researcher Paul McLean back in 1952.

System structure

Anatomically, the limbus includes areas of the paleocortex (ancient cortex), archicortex (old cortex), part of the neocortex (new cortex), and some structures of the subcortex (caudate nucleus, amygdala, globus pallidus). The listed names of various types of bark indicate their formation at the indicated time of evolution.

Weight specialists in the field of neuroscience, they dealt with the question of which structures belong to the limbic system. The latter includes many structures:

In addition, the system is closely related to the system reticular formation(structure responsible for brain activation and wakefulness). The scheme of the anatomy of the limbic complex rests on the gradual layering of one part on another. So, on top lies the cingulate gyrus, and then descending:

• corpus callosum;
• vault;
• mamillary body;
• amygdala;
• hippocampus.

A distinctive feature of the visceral brain is its rich connection with other structures, consisting of complex pathways and two-way connections. Such a branched system of branches forms a complex of vicious circles, which creates conditions for a long-term circulation of excitation in the limbus.

Functionality of the limbic system

The visceral brain actively receives and processes information from the outside world. What is the limbic system responsible for? Limbus- one of those structures that works in real time, allowing the body to effectively adapt to conditions external environment.

The human limbic system in the brain performs the following functions:

• Formation of emotions, feelings and experiences. Through the prism of emotions, a person subjectively evaluates objects and the phenomenon of the environment.
• Memory. This function is carried out by the hypocampus, located in the structure of the limbic system. Mnestic processes are provided by reverberation processes - roundabout excitations in the closed neural circuits of the sea horse.
• Selection and correction of a model of suitable behavior.
• Training, retraining, fear and aggression;
• Development of spatial skills.
• Defensive and foraging behavior.
• Expressiveness of speech.
• Acquisition and maintenance of various phobias.
• The work of the olfactory system.
• Reaction of caution, preparation for action.
• Regulation of sexual and social behavior. There is a concept of emotional intelligence - the ability to recognize the emotions of those around you.

At expression of emotions a reaction occurs, which manifests itself in the form of: changes in blood pressure, skin temperature, respiratory rate, pupil reaction, sweating, reaction of hormonal mechanisms, and much more.

Perhaps there is a question among women about how to turn on the limbic system in men. However answer simple: none. In all men, the limbus works to the full (with the exception of patients). This is justified by evolutionary processes, when a woman in almost all time periods of history was engaged in raising a child, which includes a deep emotional return, and, consequently, a deep development of the emotional brain. Unfortunately, men can no longer reach the level of development of a woman's limbus.

The development of the limbic system in infants largely depends on the type of upbringing and, in general, attitudes towards it. A stern look and a cold smile do not contribute to the development of the limbic complex, unlike a strong hug and a sincere smile.

Interaction with the neocortex

The neocortex and the limbic system are tightly connected by many pathways. Thanks to this combination, these two structures form one whole. mental sphere human: they connect the mental component with the emotional. The neocortex acts as a regulator of animal instincts: human thought usually goes through a series of cultural and moral inspections before taking any action spontaneously evoked by emotions. In addition to controlling emotions, the neocortex has an auxiliary effect. The feeling of hunger arises in the depths of the limbic system, and already the higher cortical centers that regulate behavior search for food.

The father of psychoanalysis, Sigmund Freud, did not bypass such brain structures in his time. The psychologist argued that every neurosis is formed under the yoke of the suppression of sexual and aggressive instincts. Of course, at the time of his work, there were no data on the limbus yet, but the great scientist guessed about such brain devices. So, the more cultural and moral layers (super ego - neocortex) an individual had, the more his primary animal instincts (Id - limbic system) are suppressed.

Violations and their consequences

Based on the fact that the limbic system is responsible for many functions, this very set can be susceptible to various damages. The limbus, like other structures of the brain, can be subject to injuries and other harmful factors, which include tumors with hemorrhages.

Syndromes of lesions of the limbic system are rich in number, the main ones are as follows:

Dementia- dementia. The development of diseases such as Alzheimer's and Pick's syndrome is associated with atrophy of the systems of the limbic complex, and especially in the localization of the hippocampus.

Epilepsy. Organic disorders of the hippocampus lead to the development of epilepsy.

pathological anxiety and phobias. Violation of the activity of the amygdala leads to a mediator imbalance, which, in turn, is accompanied by a disorder of emotions, including anxiety. A phobia is an irrational fear of a harmless object. In addition, an imbalance of neurotransmitters provokes depression and mania.

Autism. At its core, autism is a deep and serious maladjustment in society. The inability of the limbic system to recognize the emotions of other people leads to dire consequences.

Reticular formation(or mesh formation) is a non-specific formation of the limbic system responsible for the activation of consciousness. After deep sleep, people wake up thanks to the work of this structure. In cases of its damage, the human brain is subjected to various disorders of turning off consciousness, including absence and syncope.

neocortex

The neocortex is the part of the brain found in higher mammals. The rudiments of the neocortex are also observed in lower animals that suckle milk, but they do not reach a high development. In humans, the isocortex is the lion's share of the common cerebral cortex, which has an average thickness of up to 4 millimeters. The area of ​​the neocortex reaches 220 thousand square meters. mm.

History of occurrence

At the moment, the neocortex is the highest stage of human evolution. Scientists managed to study the first manifestations of the new bark in representatives of reptiles. The last animals that do not have a new bark in the chain of development were birds. And only a developed person has.

Evolution is a complex and long process. Every kind of creature goes through a harsh evolutionary process. If an animal species could not adapt to a changing environment, the species would lose its existence. Why is a person was able to adapt and survive to this day?

Being in favorable conditions living (warm climate and protein food), the descendants of man (before the Neanderthals) had no choice but to eat and reproduce (thanks to the developed limbic system). Because of this, the mass of the brain, by the standards of the duration of evolution, gained a critical mass in a short period of time (several million years). By the way, the mass of the brain in those days was 20% more than that of a modern person.

However, all good things come to an end sooner or later. With climate change, the descendants had to change their place of residence, and with it, start looking for food. Having a huge brain, the descendants began to use it for searching for food, and then for social involvement, because. It turned out that by uniting in groups according to certain criteria of behavior, it was easier to survive. For example, in a group where everyone shared food with other members of the group, they were more likely to survive (Someone picked berries well, and someone hunted, etc.).

From that moment began separate evolution in the brain, separate from the evolution of the whole body. Since those times appearance man has not changed much, but the composition of the brain differs dramatically.

What does it consist of

The new cerebral cortex is an accumulation of nerve cells that form a complex. Anatomically, 4 types of cortex are divided, depending on its localization -, occipital,. Histologically, the cortex consists of six balls of cells:

• Molecular ball;
• external granular;
• pyramidal neurons;
• internal granular;
• ganglionic layer;
• multiform cells.

What functions does

The human neocortex is classified into three functional areas:

• touch. This zone is responsible for the highest processing of stimuli received from the external environment. So, ice becomes cold when information about the temperature enters the parietal region - there is no cold on the finger, but there is only an electrical impulse.
• association zone. This area of ​​the cortex is responsible for the information connection between the motor and sensory cortex.
• motor zone. All conscious movements are formed in this part of the brain.
  In addition to such functions, the neocortex provides higher mental activity: intellect, speech, memory and behavior.

Conclusion

Summing up, we can highlight the following:

• Due to two main, fundamentally different, structures of the brain, a person has a duality of consciousness. For every action, two different thoughts are formed in the brain:
  • "I want" - the limbic system (instinctive behavior). The limbic system occupies 10% of the total mass of the brain, low energy consumption
  • "Need" - neocortex (social behavior). Neocortex occupies up to 80% of the total brain mass, high energy consumption and limited metabolic rate

the pressor zone leads to vasoconstriction, and the excitation of the depressor zone leads to their expansion. Vasomotor center and nuclei vagus nerve they constantly send impulses, thanks to which a constant tone is maintained: arteries and arterioles are constantly somewhat narrowed, and cardiac activity is slowed down.

AT medulla oblongata is locatedrespiratory center, which, in turn, consists of centers of inhalation and exhalation. At the level of the bridge is the center of respiration (pneumotaxic center) more high level, which adjusts breathing to changes in physical activity. Breathing in a person can also be controlled voluntarily from the side of the cerebral cortex, for example, during speech.

AT the medulla oblongata contains centers that stimulate the secretion of the salivary, lacrimal and gastric glands, the secretion of bile from the gallbladder, and the secretion of the pancreas. In the midbrain, under the anterior tubercles of the quadrigemina, there are parasympathetic centers of accommodation of the eye and pupillary reflex. All the centers of the sympathetic and nervous parasympathetic system listed above are subordinate to the higher autonomic center - hypothalamus. The hypothalamus, in turn, is influenced by a number of other centers

brain. All these centers form the limbic system.

LIMBIC SYSTEM OF THE BRAIN

The limbic system in the human brain performs a very important function called motivational-emotional. To make it clear what this function is, remember that every organism, including the human body, has a whole set of biological needs. These include, for example, the need for food, water, warmth, reproduction, and much more. In order to achieve some specific biological need develops in the body functional system(Fig. 4.3). The leading system-forming factor is the achievement of a certain result that meets the needs of the body at the moment. The initial nodal mechanism of a functional system is afferent synthesis (the left side of the diagram in Fig. 4.3). Afferent synthesis includes dominant motivation (for example, food-search for food and its consumption), situational afferentation (events of external and internal environment), trigger afferentation, and memory. Memory is necessary for the realization of a biological need. For example, a puppy that has just been weaned from the nipple cannot be fed meat because he does not perceive it as food. Only after a certain number of trials (the type of food, its smell and taste, environment, and much more is remembered) does the puppy begin to eat meat. The integration of these components leads to a decision. The latter, in turn, is associated with a specific program of action; in parallel with it, an acceptor of the results of the action is also formed, i.e. neural model of future outcomes. Information about the parameters of the result through the feedback enters the action acceptor for comparison with the previously formed model. If the parameters of the result do not correspond to the model, then excitation occurs here, which activates the orienting reaction through the reticular formation of the brain stem, and the action program is corrected. Examples of some biological motivations will be given below.

The organism also has a special mechanism for evaluating the biological significance of biological motivation. This is emotion. "Emotions are a special class mental processes and states associated with instincts, needs and motives. Emotions perform the function of regulating the activity of the subject by reflecting the significance of external and internal situations for the implementation of his life” (Leontiev, 1970). The biological substrate for the implementation of these most important functions of the body is a group of brain structures, united by close ties and components. limbic system of the brain.

A general diagram of the limbic brain structures is shown in Appendix 4. All these brain structures are involved in the organization of motivational-emotional behavior. One of the main structures of the limbic system is the hypothalamus. It is through the hypothalamus that most of the limbic structures are united into an integral system that regulates the motivational and emotional reactions of humans and animals to external stimuli and forms adaptive behavior based on the dominant biological motivation. Currently, the limbic system includes three groups of brain structures. The first group includes phylogenetically older cortical structures: the hippocampus (old cortex), the olfactory bulbs, and the olfactory tubercle (ancient cortex). The second group is represented by areas of the neocortex: the limbic cortex on the medial surface of the hemisphere, as well as the orbitofrontal cortex on the basal part of the frontal lobe of the brain. The third group includes the structures of the terminal, diencephalon and midbrain: amygdala, septum, hypothalamus, anterior group of thalamic nuclei, central gray matter of the midbrain.

Back in the middle of the last century, it was known that damage to the structures of the hippocampus, the mamillary body, and some others (now we know that these structures are part of the limbic system of the brain) causes profound disorders of emotions and memory. Currently, profound memory impairments for recent events in the hippocampal injury clinic are called Korsakoff syndrome.

Numerous clinical observations, as well as animal studies, have shown that the structures of the Paipetz circle play a leading role in the manifestation of emotions (Fig. 4.4). The American neuroanatomist Peipetz (1937) described a chain of interconnected nerve structures in the limbic system. These structures provide the emergence and flow of emotions. He drew Special attention on the existence of numerous connections between the structures of the limbic system and the hypothalamus. Damage to one of the structures of this "circle" leads to profound changes in emotional sphere psyche.

It is now known that the function of the limbic system of the brain is not limited to emotional reactions, but also takes part in maintaining the constancy of the internal environment (homeostasis), regulation of the sleep-wake cycle, learning and memory processes, regulation of autonomic and endocrine functions.

functions. Below is a description of some of these functions of the limbic system.

PHYSIOLOGY OF THE HYPOTHALAMUS

The hypothalamus is located at the base of the human brain and makes up the walls of the third cerebral ventricle. The walls to the base pass into a funnel, which ends with the pituitary gland (lower brain gland). The hypothalamus is the central structure of the limbic system of the brain and performs a variety of functions. Some of these functions relate to hormonal regulation, which are carried out through the pituitary gland. Other functions are associated with the regulation of biological motivations. These include food intake and maintenance of body weight, water intake and water-salt balance in the body, temperature regulation depending on the external temperature, emotional experiences, muscle work and other factors, the function of reproduction. It includes regulation in women menstrual cycle, bearing and giving birth to a child, feeding and much more. In men - spermatogenesis, sexual behavior. These are just some of the main features that will be covered in the tutorial. The hypothalamus also plays a central role in the body's response to stress.

Despite the fact that the hypothalamus does not occupy a very large place in the brain (its area, if you look at the brain from the base, does not exceed the area of ​​the nail in the adult brain). thumb hands), it has about four dozen nuclei. On fig. 4.5 shows only some of them. The hypothalamus contains neurons that produce hormones or special substances, which later, acting on the cells of the corresponding endocrine glands, lead to the release or cessation of the release of hormones (the so-called releasing factors from the English release - release). All these substances are produced in the neurons of the hypothalamus, then transported along their axons to the pituitary gland. The nuclei of the hypothalamus are connected to the pituitary gland by the hypothalamic-pituitary tract, which consists of approximately 200,000 fibers. The property of neurons to produce special protein secrets and then transport them for release into the bloodstream is called neurocrinia.

The hypothalamus is part diencephalon and at the same time an endocrine organ. In certain parts of it, the transformation of nerve impulses into the endocrine process is carried out. Large neurons of the anterior hypothalamus produce vasopressin (supraoptic nucleus) and oxytocin (paraventricular nucleus). In other areas of the hypothalamus, releasing factors. Some of these factors play the role of pituitary stimulants (libirins), others - inhibitors (statins). In addition to those neurons whose axons project to the pituitary gland or the pituitary portal system, other neurons in the same nucleus give off axons to many parts of the brain. Thus, the same hypothalamic neuropeptide can play the role of a neurohormone and a mediator or modulator of synaptic transmission.

CONTROL OF THE FUNCTIONS OF THE ENDOCRINE SYSTEM

The endocrine system occupies one of the central places in the management of various life processes at the level of the whole organism. This system, with the help of produced hormones, is directly involved in controlling the metabolism, physiology and morphology of various cells, tissues and organs (see Appendix 5).

Hormones are highly active biological substances that are formed in the endocrine glands, enter the blood and have a regulatory effect on the functions of organs and body systems remote from their place of secretion.

Hormones determine the intensity of protein synthesis, the size of cells, their ability to divide, the growth of the whole organism and its individual parts, the formation of sex and reproduction; various forms of adaptation and maintenance of homeostasis; nervous higher activity.

The principle of the physiological action of hormones is that they, getting into the bloodstream, are carried throughout the body. Hormones exert their physiological effects in minimal doses. For example, 1 g of adrenaline can activate 100 million isolated hearts. Cell membranes have receptors for many hormones. A molecule of each type of hormone can only connect to "its" receptor on the cell membrane (principle: a hormone molecule fits the receptor like a "key to a lock"). Such cells are called target cells. For example, for sex hormones, the target cells will be the cells of the gonads, and for adrenocorticotropic hormone (ACTH), which is released during stress, the target cells will be the cells of the adrenal cortex.

Several examples of the relationship between pituitary hormones and target organs are shown in Fig. 4.6. Violation of one or another link endocrine systems s can significantly change the normal course of physiological processes, leading to a deep pathology, often incompatible with life.

There is a functional close interdependence between the nervous and endocrine systems, which is provided by various types of connections (Fig. 4.7).

The CNS affects the endocrine system in two ways: through autonomic (sympathetic and parasympathetic) innervation and changes in the activity of specialized neuroendocrine centers. Let us illustrate this important point by the example of maintaining the level of glucose in the blood during sharp decline blood glucose levels (hypoglycemia). Because glucose is absolutely essential for brain function, hypoglycemia cannot last long. The endocrine cells of the pancreas respond to hypoglycemia by secreting the hormone glucagon, which stimulates the release of glucose from the liver. Other endocrine cells of the pancreas respond to hypoglycemia, on the contrary, by reducing the secretion of another hormone, insulin, which leads to a decrease in glucose utilization by all tissues, with the exception of the brain. Glucoreceptors of the hypothalamus respond to hypoglycemia by increasing the release of glucose from the liver through the activation of the nervous sympathetic system. In addition, the adrenal medulla is activated and adrenaline is released, which reduces the utilization of glucose by body tissues, and also promotes the release of glucose from the liver. Other neurons in the hypothalamus respond to hypoglycemia by stimulating the release of the hormone cortisol from the adrenal cortex, which increases hepatic glucose synthesis when this depot is depleted. Cortisol also inhibits insulin-activated glucose utilization in all tissues except the brain. The result of the joint reactions of the nervous and endocrine systems is the return to normal of the concentration of glucose in the blood plasma within 60 - 90 minutes.

Under certain conditions, the same substance can play the role of a hormone and a mediator, and the mechanism in both cases is reduced to a specific interaction of the molecule with the receptor of the target cell. Signals from the endocrine glands, whose role is played by hormones, are perceived by specialized nervous structures and ultimately transformed into a change in the behavior of the body and into responses of the endocrine system. The latter become part of the regulatory reactions that form neuroendocrine integration. On fig. 4.7 shows the possible types of relationships between the nervous and endocrine systems. In any given case, only a few of these paths are actually used.

The pituitary gland, the lower brain gland, is a complex endocrine organ located at the base of the skull in the Turkish saddle of the main bone, anatomically connected by a leg to the hypothalamus. It consists of three lobes: anterior, middle and posterior. The anterior and middle lobes unite under the name adenohypophysis, and the posterior lobe is called the neurohypophysis. The neurohypophysis is divided into two sections: the anterior neurohypophysis, or the median eminence, and the posterior neurohypophysis, or the posterior lobe of the pituitary gland.

The pituitary gland contains a very developed network of capillaries, the walls of which have a special structure, the so-called fenestrated (perforated) epithelium. This network of capillaries is called the "wonderful capillary network" (Fig. 4.8). Axons of neurons of the hypothalamus terminate in synapses on the walls of capillaries. Due to this, neurons eject synthesized protein molecules from synapses on the walls of these vessels directly into the bloodstream. All neurohormones are hydrophilic compounds, for which there are corresponding receptors on the membrane surface of target cells. At the first stage, the neurohormone interacts with the corresponding membrane receptor. Further signal transmission is carried out by intracellular second messengers. A diagram of the neuroendocrine system of the human body is presented in Appendix 5.

Control of posterior pituitary secretion. The posterior lobe, or neurohypophysis, is an endocrine organ that accumulates and secretes two hormones synthesized in the large cell nuclei of the anterior hypothalamus (paraventricular and supraoptic), which are then transported along the axons to the posterior lobe. Mammalian neurohypophyseal hormones include vasopressin, or antidiuretic hormone, which regulates water metabolism, and oxytocin, a hormone involved in childbirth.

Under the influence of vasopressin, the permeability of the collecting ducts of the kidney and the tone of the arterioles increase. Vasopressin in some synapses of neurons of the hypothalamus performs a mediator function. Its entry into the general circulation occurs in the case of an increase in the osmotic pressure of the blood plasma, as a result, osmoreceptors are activated - neurons of the supraoptic nucleus and the perinuclear zone of the hypothalamus. With a decrease in the osmolarity of blood plasma, the activity of osmoreceptors is inhibited and the secretion of vasopressin decreases. With the help of the described neuroendocrine interaction, which includes a sensitive feedback mechanism, the constancy of the osmotic pressure of blood plasma is regulated. In violation of the synthesis, transport, excretion or action of vasopressin develops diabetes insipidus. The leading symptoms of this disease are excretion a large number urine with a low relative density (polyuria) and a constant feeling of thirst. In patients, diuresis reaches 15-20 liters per day, which is at least 10 times higher than normal. With limited water intake, patients become dehydrated. The secretion of vasopressin is stimulated by a decrease in the volume of extracellular fluid, pain, some emotions, stress, as well as a number of drugs - caffeine, morphine, barbiturates, etc. Alcohol and an increase in the volume of extracellular fluid reduce the release of the hormone. The action of vasopressin is short-lived, as it is rapidly destroyed in the liver and kidneys.

Oxytocin is a hormone that regulates the birth act and the secretion of milk by the mammary glands. Sensitivity to oxytocin increases with the introduction of female sex hormones. The maximum sensitivity of the uterus to oxytocin is noted during ovulation and on the eve of childbirth. During these periods, the greatest release of the hormone occurs. The descent of the fetus through the birth canal stimulates the corresponding receptors, and afferentation enters

paraventricular nuclei of the hypothalamus, which increase the secretion of oxytocin. During intercourse, the secretion of the hormone increases the frequency and amplitude of uterine contractions, facilitating the transport of sperm into the oviducts. Oxytocin stimulates milk flow by causing contraction of the myoepithelial cells lining the breast ducts. As a result of the increase in pressure in the alveoli, milk is squeezed into large ducts and is easily excreted through the nipples. When the tactile receptors of the mammary glands are stimulated, impulses are sent to the neurons of the paraventricular nucleus of the hypothalamus and cause the release of oxytocin from the neurohypophysis. The effect of oxytocin on milk flow appears 30-90 seconds after the start of nipple stimulation.

Control of the secretion of the anterior pituitary gland. Most of the hormones of the anterior pituitary gland act as specific regulators of other endocrine glands, these are the so-called "tropic" hormones of the pituitary gland.

adrenocorticotropic hormone(ACTH) - the main stimulator of the adrenal cortex. This hormone is released during stress, spreads through the bloodstream and reaches the target cells of the adrenal cortex. Under its action, catecholamines (adrenaline and noradrenaline) are released from the adrenal cortex into the blood, which have a sympathetic effect on the body (this effect was described in more detail above). luteinizing hormone is the main regulator of the biosynthesis of sex hormones in male and female gonads, as well as a stimulator of growth and maturation of follicles, ovulation, formation and functioning corpus luteum in the ovaries. Follicle stimulating hormone increases the sensitivity of the follicle to the action of luteinizing hormone, and also stimulates spermatogenesis. Thyrotropic hormone is the main regulator of the biosynthesis and secretion of thyroid hormones. The group of tropic hormones includes growth hormone, or somatotropin, the most important regulator of body growth and protein synthesis in cells; also participates in the formation of glucose and the breakdown of fats; part of the hormonal effects is mediated through increased liver secretion of somatomedin (growth factor I).

In addition to tropic hormones, hormones are formed in the anterior lobe that perform an independent function, similar to the functions of hormones in other glands. These hormones include: prolactin, or lactogenic hormone, regulating lactation (milk formation) in a woman, differentiation of various tissues, growth and metabolic processes, instincts for nursing offspring in representatives of various classes of vertebrates. Lipotropins are regulators of fat metabolism.

The functioning of all parts of the pituitary gland is closely related to the hypothalamus. The hypothalamus and pituitary gland form a single structural and functional complex, which is often called the "endocrine brain".

The epiphysis, or superior pineal gland, is part of the epithalamus. Hormone melatonin is formed in the pineal gland, which regulates the body's pigment metabolism and has an antigonadotropic effect. The blood supply of the epiphysis is carried out through the circulatory network formed by the secondary branches of the middle and posterior cerebral arteries. Entering the connective tissue capsule of the organ, the vessels break up into many capillaries of the organ with the formation of a network characterized by a large number of anastomoses. Blood from the pineal gland is partially diverted to the system of the great cerebral vein of Galen, some of it enters the veins of the choroid plexus III ventricle. The neurosecretion of the pineal gland depends on the illumination. The main link in this chain is the anterior hypothalamus (suprachiasmatic nucleus), which receives direct input from the fibers of the optic nerve. Further, a descending path is formed from the neurons of this nucleus to the superior sympathetic ganglion and then, as part of a special (pineal) nerve, enters the epiphysis.

In the light, the production of neurohormones in the pineal gland is inhibited, while during the dark phase of the day it increases. Melatonin affects the functions of many parts of the central nervous system and some behavioral responses. For example, in humans, an injection of melatonin induces sleep.

Other physiologically active substance pineal gland, claiming to be a neurohormone, is serotonin, a precursor of melatonin. Animal studies have shown that the content of serotonin in the pineal gland is higher than in other organs, and depends on the species, age of the animals, as well as the light regime; it is subject to diurnal fluctuations with a maximum level in daytime. Daily rhythm of serotonin content in the pineal gland

In 1878, Paul Broca introduced the concept Limbus(border) - this is how the scientist called the lobes of the brain that lie on the border of the brain stem and the cerebral cortex. Term "limbic system" used in relation to the ancient and old cortex together with the hypothalamus, pituitary gland, limbic region of the midbrain and elements of the reticular formation (Fig. 11.9).

The structures of the limbic system include three complexes:

• lower section - amygdala and hippocampus - centers of emotions and behavior for survival and self-preservation;
• upper section- cingulate gyrus and temporal cortex - centers of sociability and sexuality;
• the middle section - the hypothalamus and the cingulate gyrus - are the centers of biosocial instincts.

The limbic system is characterized by complex bilateral connections between its own structures, the cerebral cortex, the thalamus, hypothalamus, brain stem and other formations of the nervous system in the form of vicious circles, which ensures long-term maintenance of excitation and interaction of all departments of this system. The limbic system is associated with different zones the cerebral cortex and plays a major role in the transmission of various afferent stimuli to the cortex, the implementation of perception, in the change of sleep and wakefulness.

The main purpose of the limbic system is that it provides a purposeful behavior of a person, his emotional

Rice. 11.9.

• 1 - hypothalamus; 2 - mamilary body; 3 - anterior nuclei of the thalamus; 4 - almond-shaped complex of nuclei; 5 - reticular formation; 6 - partition; 7 - pituitary gland;
• 8 - cingulate gyrus; 9 - corpus callosum; 10 - vault; 11 - hippocampus; 12 - hippocampal cortex. The dots indicate the new cerebral cortex; dashes - limbic system; arrows indicate the direction of communication between structures

rational attitude and motivation to action. The limbic system is the center of emotions, instincts, innate reactions, but the cerebral cortex directs emotions, gives them an individual character.

Emotions are a reflection by the brain of the actual needs of the organism and the probability of its satisfaction (see Chapter 13); it is a tool for the regulation of mental activity. Emotions support vitality, interest in life. The amplifying function of emotions is achieved due to the powerful downward influence of brain structures on autonomics. Therefore, the limbic system is called visceral cortex, since it ensures the correspondence of cortical processes to vegetative functions.

So, in most athletes in the pre-start situation, the minute volume of blood circulation increases, and the increase can reach 85%. Simultaneous interpreters during responsible work and in the absence physical activity only due to emotional stress, the heart rate can jump up to 160 bpm. In humans, both positive and negative emotions cause the activation of the sympathetic nervous system, and if the state of sadness is more characterized by shifts from of cardio-vascular system, then for the state of joy - shifts from the side of breathing. However, changes in breathing can also occur with negative emotions, for example, during crying. This stimulates the work of the lacrimal glands. Strong emotional experiences are accompanied by the release of various hormones into the blood, and the reaction can more and more resemble Selye's stress syndrome.

The perception of afferent stimuli and the emergence of sensations and emotions (fear, joy, hunger, satiety, rage, pleasure, etc.) are associated not only with the structures of the limbic system, but also with the formations of the new cortex. After its removal, but with the preservation of limbic structures, the animal becomes apathetic and non-reactive, its emotional manifestations are very poor, and behavioral reactions often do not correspond to the emotional state.

The occurrence of orienting reactions is associated with the hippocampus. Changes found in it electrical activity at the start of production conditioned reflexes. It is believed that the hippocampus and some subcortical structures are involved in the early stages of learning.

Damage to the human hippocampus disrupts the memory of events close to the moment of damage, memory, processing of new information, and the difference in spatial signals are disturbed. Damage to the hippocampus leads to a decrease in emotionality, initiative, and a slowdown in the speed of the main nervous processes that increase the thresholds for triggering emotional reactions.

After bilateral removal of part of the hippocampus for the surgical treatment of severe epilepsy, patients were able to recall previous knowledge, but they lost the ability to learn new information based on word symbols. They couldn't even remember the names of the people they met every day. At the same time, they could recall at some point a specific event that occurred in their current activities. Therefore, they are capable of short term memory from a few seconds to one or two minutes, although the ability to retain short-term or long-term memory for a longer period is completely impaired. This phenomenon is known as anterograde amnesia. These data show that without the hippocampus, the process of consolidating short-term memory into long-term verbal or symbolic signals is impossible.

The limbic system is associated with feelings of pleasure and discomfort. Patients with irritation of the tonsil during the operation had a feeling of joy and pleasure.

Damage to the amygdala in monkeys causes a complex of changes: they show curiosity about everything, immediately forget about everything, try to taste any inedible objects, have sexual intercourse with individuals of other species (hypersexuality), lose their sense of fear, are not capable of rage and aggression, become gullible, calmly approach the viper, which previously caused them horror. Apparently, in the case of damage to the amygdala, some innate unconditioned reflexes that realize the memory of danger disappear.

After damage to the cingulate gyrus, reflexes associated with caring for offspring are disturbed: the mother rat does not build nests for children, does not care for them, and does not save them from danger.

The limbic system is the center of the olfactory sensory system.

An analysis of the functions performed by various parts of the brain indicates that all vital processes that ensure the homeostasis of the body, its ability to adapt to changing external environmental conditions, movement in time and space (i.e. motor acts) occur with the participation of various parts of the spinal cord and brain, under the control of the respective centers. At the same time, the underlying centers perform an executive function, and the overlying centers - regulatory and controlling functions. The highest regulatory and controlling department is the cerebral cortex.

Questions and tasks

• 1. What is the role of different parts of the CNS in the formation of muscle tone?
• 2. What disorders of motor acts can be observed in violation of the cerebellum?
• 3. What centers are located in the hypothalamus, what is their significance?
• 4. What CNS structures are involved in the regulation of sleep? Explain the answer.
• 5. For the implementation of what processes is the cerebral cortex responsible?
• 6. What is the role of the reticular formation in the regulation of CNS functions?

The limbic system is a functionally unified complex of nervous structures responsible for emotional behavior, urges to act (motivations), learning and memory processes, instincts (food, defensive, sexual) and regulation of the sleep-wake cycle. Due to the fact that the limbic system perceives a large amount of information from the internal organs, it received a second name - the "visceral brain".

The limbic system consists of three structural complexes: the ancient cortex (paleocortex), the old cortex (archicortex), and the median cortex (mesocortex). The ancient cortex (paleocortex) includes preperiform, periamygdala, diagonal cortex, olfactory bulbs, olfactory tubercle, and transparent septum. The second complex, the old cortex (archicortex), consists of the hippocampus, dentate fascia, and cingulate gyrus. The structures of the third complex (mesocortex) are the insular cortex and the parahippocampal gyrus.

The limbic system includes such subcortical formations as the tonsils of the brain, the septal nuclei, the anterior thalamic nucleus, the mamillary bodies, and the hypothalamus.

The main difference between the limbic system and other parts of the central nervous system is the presence of bilateral reciprocal connections between its structures, which form closed circles through which impulses circulate, providing functional interaction between various parts of the limbic system.

The so-called Peipes twist includes: the hippocampus - the mamillary bodies - the anterior nuclei of the thalamus - the cortex of the cingulate gyrus - the parahippocampal gyrus - the hippocampus. This circle is responsible for emotions, memory formation and learning.

Another circle: amygdala - hypothalamus - mesencephalic structures - the amygdala regulates aggressive-defensive, food and sexual forms of behavior.

The limbic system forms connections with the neocortex through the frontal and temporal lobes. The latter transmit information from the visual, auditory, and somatosensory cortex to the amygdala and hippocampus. It is believed that the frontal areas of the brain are the main cortical regulator of the activity of the limbic system.

Functions of the limbic system

Numerous connections of the limbic system with the subcortical structures of the brain, the cerebral cortex and internal organs allow it to take part in the implementation of various functions, both somatic and vegetative. It controls emotional behavior and improves the adaptive mechanisms of the body in the new conditions of existence. With the defeat of the limbic system or experimental impact on it, eating, sexual and social behavior is disturbed.

The limbic system, its ancient and old cortex are responsible for olfactory functions, and olfactory analyzer is the oldest. It triggers all kinds of activities of the cerebral cortex. The limbic system includes the highest vegetative center - hypothalamus, creating vegetative support for any behavioral act.

The most studied structures of the limbic system are the amygdala, hippocampus, and hypothalamus. The latter was described earlier (see p. 72).

Amygdala (amygdala, amygdala) is located deep in the temporal lobe of the brain. The neurons of the amygdala are polysensory and ensure its participation in defensive behavior, somatic, vegetative, homeostatic and emotional reactions, and in the motivation of conditioned reflex behavior. Irritation of the amygdala leads to changes in the cardiovascular system: fluctuations in heart rate, the appearance of arrhythmias and extrasystoles, a decrease in blood pressure, as well as reactions from the gastrointestinal tract: chewing, swallowing, salivation, changes in intestinal motility.

After the bilateral removal of the tonsils, the monkeys lose the ability for social intragroup behavior, they avoid the rest of the group members, behave aloofly, seem to be anxious and insecure animals. They do not distinguish edible objects from inedible ones (mental blindness), their oral reflex becomes pronounced (they take all objects in their mouths) and hypersexuality occurs. It is believed that such disorders in amygdalaectomized animals are associated with a violation of bilateral connections between the temporal lobes and the hypothalamus, which are responsible for acquired motivational behavior and emotions. These brain structures compare newly received information with the already accumulated information. life experience, i.e. with memory.

Currently, a fairly common emotional disorder associated with pathological functional changes in the structures of the limbic system is state of anxiety which manifests itself in motor and vegetative disorders, feeling of fear facing real or imagined danger.

hippocampus - one of the main structures of the limbic system is located deep in the temporal lobes of the brain. It forms a complex of stereotypically repeating interconnected micro-networks or modules that allow information to circulate in this structure during learning, i.e. the hippocampus is directly related to memory. Damage to the hippocampus leads to retroanterograde amnesia or impaired memory for events close to the moment of damage, a decrease in emotionality, and initiative.

The hippocampus is involved in the orienting reflex, the reaction of alertness, increasing attention. He is responsible for the emotional accompaniment of fear, aggression, hunger, thirst.

In the general regulation of human and animal behavior, the connection between the limbic and monoaminergic brain systems. The latter include dopaminergic, noradrenergic and serotonergic systems. They begin in the trunk and innervate various parts of the brain, including some structures of the limbic system.

So, noradrenergic neurons send their axons from the locus coeruleus, where they are in large numbers, to the amygdala, hippocampus, cingulate gyrus, entorhinal cortex.

dopaminergic neurons in addition to the substantia nigra and basal nuclei, they innervate the amygdala, septum and olfactory tubercle, frontal lobes, cingulate gyrus and entorhinal cortex.

Serotonergic neurons are located mainly in the median and near-median nuclei (nuclei of the median suture) of the medulla oblongata and, as part of the medial bundle of the forebrain, innervate almost all parts of the diencephalon and forebrain.

Experiments with self-irritation using implanted electrodes or on a person during neurosurgical operations "proved that stimulation of the innervation zones by catecholaminergic neurons located in the limbic system leads to pleasant sensations. These zones are called pleasure centers. Next to them are clusters of neurons, the irritation of which causes an avoidance reaction, they were called "centers of displeasure".

Many mental disorders are associated with monoaminergic systems. Over the past decades, for the treatment of disorders of the limbic system, psitropic drugs have been developed that affect the monoaminergic systems and indirectly on the functions of the limbic system. These include tranquilizers of the benzodiazepine series (seduxen, elenium, etc.), which relieve constipation (imizin), neuroleptics (aminosine, haloperidol, etc.