The brain is the main regulator of all the functions of a living organism. It is one of the elements of the central nervous system. The structure and functions of the brain are still the subject of medical study.
general description
The human brain consists of 25 billion neurons. These cells are the gray matter. The brain is covered with shells:
The hypothalamus performs the following functions: it controls and integrates the autonomic nervous system, being the main regulator of visceral activity. Reception and integration of sensory impulses that come from the visceral organs. It is the main mediator between the nervous system and the endocrine system, in addition to the direct production of two hormones. It is the regulatory center of the organic response to powerful emotions. It is associated with feelings of aggression and anger. Controls normal body temperature.
Regulates food intake through two centers: appetite and satiety. It contains the center of thirst. It is one of the centers that maintains the state of wakefulness and sleep pattern has the properties of being a self-regulating generator, since actions such as a pacemaker to regulate biological rhythms.
- solid;
- soft;
- arachnoid (the so-called cerebrospinal fluid, which is cerebrospinal fluid, circulates through its channels). Liquor is a shock absorber that protects the brain from shock.
Despite the fact that the brain of women and men is equally developed, it has a different mass. So for the representatives of the stronger sex, its average weight is 1375 g, and for the ladies - 1245 g. The weight of the brain is about 2% of the weight of a person of normal physique. It has been established that the level of mental development of a person is in no way related to his weight. It depends on the number of connections created by the brain.
Deep grooves located between the folds are called cracks. The most noticeable fissure is the longitudinal one, which divides the brain into two halves, the right and left hemisphere, however, in its inner part are connected a large bundle of fibers, the callus of the body. Lobes: Each hemisphere of the brain is later divided into four lobes: frontal, parietal, temporal and occipital, separated by furrows. The precentral gyrus is an area of the primary motor cortex, and the postcentral, are the general sensory areas of the cerebral cortex.
Brain cells are neurons that generate and transmit impulses and glia that perform additional functions. Inside the brain there are cavities called ventricles. Paired cranial nerves (12 pairs) depart from it in different parts of the body. The functions of the parts of the brain are very different. The vital activity of the organism completely depends on them.
The figure shows the Brodmann map, which studied and characterized the functional areas of the cerebral cortex. Broca's area and other areas of language are located in the left hemisphere of the brain, regardless of whether people are left or right. Damage to the sensory or motor areas of speech causes an inability to speak or write.
In the deep part of the brain, nuclei of gray matter called the basal ganglia are paired and located in each hemisphere, and have a relationship with each other and with the cerebral cortex and have control of subconscious movements skeletal muscle, and regulate muscle tone necessary for certain body movements. Limbic system, a group of bony structures chicken breast, which spans the brainstem and functions in the emotional aspects of survival behavior, consists of some areas of the cortex, and some nuclei and bodies within the brain, and together with the hippocampus store memory.
Structure
The structure of the brain, the pictures of which are presented below, can be considered in several aspects. So it distinguishes 5 main parts of the brain:
- final (80% of the total mass);
- intermediate;
- posterior (cerebellum and bridge);
- average;
- oblong.
Also, the brain is divided into 3 parts:
Although behavior is a function of the entire nervous system, limbic system controls most involuntary aspects. It is associated with pleasure and pain. It suggests a primary function in emotion, pleasure, anger, anger, fear, sadness, sexual feelings, obedience, and affection. That's why it's called the "visceral" or "emotional" brain.
Areas of the cerebral cortex. The primary sensory areas corresponding to the zone located behind the central sulcus were assigned the numbers 1, 2, and its main function is to pinpoint the points of the body where sensations occur. The competitive area of the association corresponds to numbers 5 and 7 in the figure. Its function is to integrate and interpret sensations and to store the memory of previous sensory experiences. For each sense organ, there are specific areas of the cortex, some of which have primary zones and other associations.
- large hemispheres;
- brain stem;
- cerebellum.
The structure of the brain: a drawing with the name of the departments.
telencephalon
The structure of the brain cannot be briefly described, since without studying its structure it is impossible to understand its functions. telencephalon stretched from the occipital to the frontal bone. It has 2 large hemispheres: left and right. It differs from other parts of the brain in having a large number convolutions and furrows. The structure and development of the brain are closely interrelated. Specialists distinguish 3 types of the cerebral cortex:
The motor area is located in the precentral gyrus of the frontal lobe, controls the movement of striated or voluntary muscles, the premotor area, area 6 is in front of the primary motor area, is associated with the study of motor activity of a complex nature and sequential, generates nerve impulses that cause specific group muscles contract sequentially, such as writing, control movement skills.
Where the functions of different parts of the brain are summed up. Taken from: Principles of Anatomy and Physiology. Summary Prepared by Elvira Neira. Responsible for most control functions in the body, coordinating and regulating bodily actions. The neuron is the functional unit of this system.
- ancient, which includes the olfactory tubercle; perforated anterior substance; semilunar, subcallosal and lateral subcallosal gyrus;
- the old one, which includes the hippocampus and the dentate gyrus (fascia);
- new, represented by the rest of the cortex.
The structure of the cerebral hemispheres: they are separated by a longitudinal groove, in the depths of which the fornix and corpus callosum are located. They connect the hemispheres of the brain. The corpus callosum is a new cortex made up of nerve fibers. Under it is a vault.
Neurons communicate through synapses; nerve impulses travel through them. Anatomically, a neuron is formed by: a dendrite, a cell body and an axon. Transmission occurs only in the direction of the dendrite towards the axon. The main components of the central nervous system.
The spinal cord is the center. It is organized into segments. This is a structure subordinate to the brain, but can act independently of it. The brain is involved with most bodily functions, such as receiving visual information in vertebrates, body movements that require the coordination of a large number of body parts.
Structure hemispheres the brain appears as multilevel system. So they distinguish between lobes (parietal, frontal, occipital, temporal), cortex and subcortex. The cerebral hemispheres perform many functions. Right hemisphere governs the left half of the body, and the left - the right. They complement each other.
The mammal is divided into: medulla, medulla, mesencephalin, mycelenphalon. The lamp has a function associated with it and is considered a vital center. It is also associated with cardiovascular reflexes and the transmission of sensory and motor information.
The cerebellum is responsible for motor control. The basic organization of the cerebellum is almost the same in all vertebrates, differing only in the number of cells and the degree of wrinkles. Recent studies show that the primary function of the cerebellum is sensory coordination, not just motor control.
Bark
The hypothalamus is a subcortical center in which the regulation of vegetative functions takes place. Its influence occurs through the endocrine glands and the nervous system. It is involved in the regulation of some endocrine glands and metabolism. Under it is the pituitary gland. Thanks to him, the regulation of body temperature, digestive and cardiovascular systems occurs. The hypothalamus regulates wakefulness and sleep, forms drinking and eating behavior.
The function of the bridge is to transmit information from the medulla and bulb to the cerebral cortex. Connects to hierarchically higher centers. sensory cortex coordinates stimuli emanating from different parts of the nervous system. The motor cortex is responsible for voluntary action, and the association braid is associated with memory storage.
Main divisions of the peripheral nervous system
It has to do with voluntary movements. There may be involuntary movements. It is associated with involuntary muscle movements such as the leafless and striated cardiac, endocrine and respiratory systems. It is divided into sympathetic and parasympathetic. They have an antagonistic function over each other.
Hind brain
This department consists of the bridge located in front and the cerebellum located behind it. The structure of the bridge of the brain: its dorsal surface is covered by the cerebellum, and the ventral one has a fibrous structure. These fibers are directed transversely. On each side of the bridge they pass into the cerebellar middle peduncle. The bridge itself looks like a thick white roller. It is located above the medulla oblongata. Nerve roots come out in the bulbar-pontine groove. The hindbrain: structure and functions - on the frontal section of the bridge, it is noticeable that it consists of a large ventral (front) and a small dorsal (back) part. The border between them is a trapezoid body. Its thick transverse fibers are referred to as the auditory pathway. The hindbrain provides a conductive function.
These are involuntary reactions involving nerve impulses moving along a path called a reflex arc. Good famous example reflex arc is the patellar reflex. The knee is the organ that receives the stimulus. When it receives a stimulus, the dendrites of the neurons fire. Momentum is transmitted association neurons with the help of synapses, which, in turn, transmit impulses to motor neurons.
Organization of nervous tissue in the central nervous system
Associative neurons carry information to the brain, and motor neurons excite the thigh muscles, causing the leg to move. It begins at that time in the first cervical vertebra and ends at the height of the first lumbar vertebrae. The top shows the spinal canal, where the bone marrow is located in a very protected manner.
Often called the small brain, it is located behind the bridge. It covers the rhomboid fossa and occupies almost the entire posterior fossa of the skull. Its mass is 120-150 g. Above the cerebellum, the large hemispheres hang from above, separated from it by the transverse fissure of the brain. The lower surface of the cerebellum is adjacent to the medulla oblongata. It distinguishes 2 hemispheres, as well as the upper and lower surfaces and the worm. The boundary between them is called a deep horizontal slit. The surface of the cerebellum is indented with many slits, between which are located thin ridges (gyrus) of the medulla. Groups of convolutions located between deep grooves are lobules, which, in turn, make up the lobes of the cerebellum (anterior, flocculent-nodular, posterior).
In the spinal cord, the distribution of white and gray matter is inverse to the distribution in the brain and cerebellum previously studied. White matter lies at the periphery and gray matter lies at the center. Cross sections spinal cord show that the details of their anatomy change depending on the height at which they are carved. However, in general, the gray matter looks like a butterfly with open wings.
The spinal cord is an important organ of communication between the body and the encephalon. Through the white matter of the medulla pass important sets of bundles of axons that transmit. These motor neurons control important bodily functions such as muscle contraction and gland secretion. They receive information from higher centers through axons that enter through the white matter of the bone marrow.
There are 2 types of substance in the cerebellum. Gray is on the periphery. It forms a cortex in which there is a molecular, pear-shaped neuron and a granular layer. The white matter of the brain is always under the cortex. So in the cerebellum it forms the brain body. It penetrates into all convolutions in the form of white stripes covered with gray matter. In the whitest matter of the cerebellum there are blotches of gray matter (nucleus). On the cut, their ratio resembles a tree. Our coordination of movement depends on the functioning of the cerebellum.
Many of these motor neurons are located in the ventral portion of the spinal cord - it looks like an average figure and controls muscle contraction in different segments of the body. The axons of these neurons leave the brain in their ventral part, which contributes to the constitution of the spinal nerves, which are directed to the skeletal muscles.
Motor neurons in the brain can also control the activity of glands, smooth muscles, and heart muscle. These actions are performed after their axons establish synapses in the ganglion neurons of the autonomic nervous system. These neurons emit axons that will innervate the structures mentioned above.
midbrain
This department is located from the anterior edge of the bridge to the papillary bodies and optic tracts. In it, a cluster of nuclei is isolated, which are called tubercles of the quadrigemina. The midbrain is responsible for latent vision. It also contains the center of the orienting reflex, which ensures that the body turns in the direction of sharp noise.
These axons point to sensory ganglia lateral to the bone marrow, forming two chains of ganglia throughout the brain. These ganglia contain pseudo-polar neurons from which axons emerge that ultimately carry sensory information out of the body. There they establish synapses with other neurons, and the information is sent to higher centers or to nearby motor neurons, forming a reflex arc.
It has the shape of a slightly flattened cone. Picture 1: General form brain. Inside, in the lower part, the flask has gray and white matter distributed like a brain, while in the upper part it does not. In the lower half are the same bundles of white matter and the same axis of the gray matter of the bone marrow. In its upper half, the structure changes. The bundles that form the position of the change in white matter, and the gray matter axis terminates in a series of gray nuclei.
Medulla. The medulla oblongata is a direct continuation of the spinal cord. Its lower border is at the level of the large occipital foramen. At the top, the medulla oblongata borders on the hindbrain - the lower edge of the bridge.
The length of the medulla oblongata is about 25mm . It is shaped like a truncated cone. The anterior surface of the medulla oblongata is divided anterior median fissure. On the sides of this gap are longitudinal elevations - pyramids, formed by bundles of nerve fibers of the descending pathways. On the side of the pyramids on each side, exit the brain hypoglossal nerve roots(XII pair of cranial nerves).
Figure 2: Diagram showing the gray columns that form in the flask. In addition, there are white and gray formations characteristic of the flask, which means that they do not originate from any other nerve organ. The structural conformation of the bulb, similar to the structure of the spinal cord, is a decisive factor in the equality of the functions performed by both organs. In fact, the flask does not differ from the bone marrow in its functions: it conducts sensory and motor nerve impulses and is the center of reflex actions.
The bulb has centers of reflex actions of vegetative life and relationship life. That is, it controls important organs to keep the body alive. Among these centers we will explain the function of the respiratory, cardiac, vasomotor and swallowing centers.
The posterior surface of the medulla oblongata is divided posterior median sulcus. On the sides of it are suitable here posterior funiculi of the spinal cord. On the sides of the posterior cords, they exit the brain roots of the glossopharyngeal, vagus and accessory nerves (IX, X, XI pairs of cranial nerves). The cavity of the medulla oblongata (common with the hindbrain) is the IV ventricle.
Respiratory Center: This center has neurons that control inspiration and expiration. Damage to this site results in death by asphyxiation. This center is activated mainly when it detects high concentrations in the blood carbon dioxide, as well as changes in oxygen concentration, temperature and emotional states. In relation to this center are in the center of sneezing, coughing and yawning.
Heart Center: This center acts by decreasing the heart rate and is cardioinhibitory. Vasomotor center: Its constrictive action is important for maintaining blood pressure. As in the respiratory center, they act on these high concentrations of carbon dioxide.
Internal structure. The medulla oblongata is made up of gray and white matter bases and covers. The white matter of the base of the medulla oblongata consists of long nerve fibers, descending pathways. Descending pathways run from the cerebral cortex and nuclei of the brain stem to the motor nerve cells of the spinal cord. The white matter of the tegmentum oblongata consists of ascending and descending pathways. The ascending pathways are the continuation of the pathways of the spinal cord leading to the nuclei (gray matter) of the brain.
The gray matter of the tegmentum oblongata consists of separate groups of nerve cells located inside the white matter. it cranial nerve nuclei from IX to XII pair and clusters of neurons of the reticular formation. Reticular formation(net substance) is formed by individual nerve cells and their small clusters (nuclei), connected to each other by numerous processes (nerve fibers).
Functional significance of the medulla oblongata. Nuclei of the medulla oblongata provide sensory, motor and autonomic innervation of many organs of the head, neck, chest and abdomen. Thus, the axons of the motor nerve cells of the hypoglossal nerve, forming hypoglossal nerve, innervates all the muscles of the tongue. Nerve fibers accessory nerve(XI pair) are sent to some muscles of the neck. vagus nerve(X pair) innervates the organs of the chest and abdominal cavities of the body (heart, lungs, organs of the digestive system, etc.). I hypopharyngeal nerve(IX pair), together with the vagus, innervates the muscles of the pharynx, and the sensory fibers of these nerves - the mucous membrane of the tongue, pharynx, larynx.
Cells and cell clusters reticular formation participate in the formation of ascending and descending pathways, affect the nerve impulses passing through them (strengthen or weaken them). The nuclei of the reticular formation regulate the rhythmic contractions of the diaphragm (inhale - exhale) - the respiratory center, the level of blood pressure in the vessels (vasomotor center).
Bridge of the brain (Varoli's bridge)
The bridge of the brain is located in front of the medulla oblongata in the form of a thickened roller. The transverse fibers of the bridge form right and left middle leg cerebellum that connect the pons to the cerebellum. The posterior surface of the bridge, covered by the cerebellum, participates together with the medulla oblongata in the formation of the bottom of the IV ventricle - the so-called rhomboid fossa. Cranial nerves emerge from the bridge (from V to VII pair): this trigeminal nerve(V) abducens nerve(VI) facial nerve (VII) and vestibulocochlear nerve (VII).
Internal structure. The white matter of the bridge is formed by ascending and descending pathways. In the white matter of the bridge, there are pathways for hearing and balance, as well as sensory pathways that conduct nerve impulses from the skin of the face and other organs of the head. The gray matter of the pons consists of the motor, sensory, and autonomic nuclei of the cranial nerves and neurons of the reticular formation, which continues into the pons from the medulla oblongata.
Functional value of the bridge. From the nuclei of the bridge, sensitive, motor and autonomic innervation of the organs of the head, including some sense organs, is carried out. So, trigeminal nerve(V pair) innervates the masticatory muscles with motor fibers, and its sensory fibers, forming three branches, conduct sensory impulses from the skin of the face and other organs of the head to the bridge. Abducens nerve(VI pair) carries motor impulses to one of the oculomotor muscles (abductor). Axons of nerve cells of the motor nucleus facial nerve(VII pair) innervate the mimic muscles of the face, and its sensory fibers conduct taste sensitivity from the receptors of the tongue to the bridge. To the cores vestibulocochlear nerve nerve impulses come from the organs of hearing and balance (inner ear).
Cerebellum. The cerebellum (small brain) is located behind the pons of the medulla oblongata. It consists of a middle unpaired part - worm and paired right and left hemispheres. The surface of the hemispheres and the worm is separated by numerous transverse grooves, between which there are narrow strips - leaves of the cerebellum. Pathways connect the cerebellum with other parts of the central nervous system. They form three pairs of cerebellar peduncles - inferior, superior and medium. The lower ones connect the cerebellum with the medulla oblongata, the upper ones with the midbrain, and the middle ones with the pons.
Internal structure. The cerebellum is divided into gray and white matter. The gray matter is located superficially and forms cerebellar cortex thickness 1 - 2.5mm. Nerve cells in the cortex form three layers. The outer molecular and inner granular layers are composed of small nerve cells. The middle layer is formed by large pear-shaped cells. The white matter of the cerebellum is represented by nerve fibers and lies under the cortex. In the thickness of the white matter there are groups of neurons that form paired cerebellar nuclei. Outgrowths of one of the largest of them (dentate nucleus) are part of the superior cerebellar peduncle. Other cores (corky, spherical and the so-called tent cores) lie between the dentate nuclei.
The functional significance of the cerebellum. The cerebellum influences various motor functions. It provides accuracy, agility and coordination of movements. The cerebellum is involved in the regulation of autonomic functions, affects the cardiovascular, respiratory and digestive systems.
Under the cerebellum is IV ventricle, which is the cavity of the hindbrain and medulla oblongata. At the bottom, the central canal of the spinal cord opens into the IV ventricle, and at the top, the IV ventricle passes into a narrow canal - brain plumbing, which is the cavity of the midbrain. The bottom of the IV ventricle, formed by the posterior surface of the medulla oblongata and the bridge, has the shape of a rhombus, so it is called rhomboid fossa. The roof of the IV ventricle has the appearance of a tent, which is formed by a thin plate of the medulla (the upper legs of the cerebellum, the upper and lower cerebral sails). The lower part of the tent from the side of the IV ventricle is covered vascular plexus, whose cells produce cerebrospinal fluid.
Midbrain. The midbrain is located between the pons below and the diencephalon above. The midbrain includes the peduncles of the brain and the roof of the midbrain. The midbrain has a cavity, the so-called aqueduct of the brain - a narrow canal that connects the III and IV ventricles of the brain.
The roof of the midbrain, or plate of the quadrigemina, is divided by transverse and longitudinal furrows into two upper and two lower hillocks. The nuclei formed by the nerve cells of the superior colliculi are subcortical centers of vision, and the lower hillocks - subcortical centers of hearing.
The legs of the brain are white rounded strands emerging from the bridge and heading forward and upward to the diencephalon and to the hemispheres big brain.III and IV pairs of cranial nerves depart from the midbrain - oculomotor and block nerve.
Each leg of the brain is made up of grounds and tires, which are separated by black matter
It is formed by nerve cells, in the cytoplasm of which there is a lot of melanin pigment. The substantia nigra is involved in maintaining the muscle tone of skeletal muscles, as well as in the regulation of the functions of the autonomic nervous system.
At the base of the legs of the brain, there are descending pathways from the cells of the cerebral cortex to the motor neurons of the anterior horns of the spinal cord and to the motor nuclei of the cranial nerves located in the brain stem.
Midbrain tegmentum formed by ascending and descending pathways. The gray matter of the midbrain tegmentum consists of nuclei of cranial nerves III and IV pairs (oculomotor and block). red nuclei and cells reticular formation. The processes of cells of the III and IV nuclei are sent to the muscles of the eyeball. Red nuclei regulate skeletal muscle tone and provide habitual, automatic movements of skeletal muscles.
The functions of the midbrain are also associated with the nuclei of its hillocks - the plates of the quadrigemina. Nerve cells These nuclei, in response to light and sound stimuli, send impulses through motor neurons to the muscles of the head and trunk, which provide fast movements. These reflexes contribute to a quick reaction of the body to unexpected, sudden irritations.
21.diencephalon located above the midbrain, under the cerebral hemispheres. Its structures are mostly hidden by the telencephalon hemispheres. In the diencephalon, there are: a paired thalamus (visual tubercles), a foreign, epithelium, and hypothalamus (hypothalamus). The cavity of the diencephalon is the third ventricle.
Thalamus (optic tubercle) - a paired formation of an ovoid shape. Its lower surface merges with the hypotuberous region, the outer lateral (lateral) - borders on the large hemisphere, the inner lateral (medial) - forms the lateral wall of the third ventricle.
The thalamus is made up of gray and white matter. Gray matter is made up of clusters of nerve cells. cores. There are about 40 nuclei in the visual tubercle. On the cells of some of them, the nerve fibers of the ascending pathways terminate, along which impulses of all types of general sensitivity rise (pain, temperature, touch, pressure, etc.), including sensitive signals from muscles and tendons. The axons of the intercalary neurons of the nuclei of the thalamus form direct connections with the nerve cells of the central (projective) fields of the cerebral cortex. Thus, all sensitive nerve impulses, signals that enter the cortex of the cerebral hemispheres, pass through the thalamus of the diencephalon. Therefore, when the thalamus is damaged, the conscious perception of various types of sensitivity decreases or completely disappears.
Scattered cells and nuclei reticular formation(mesh formation), located in the diencephalon and in the deep (central) parts of the midbrain, pons and medulla oblongata, perform a conductor function, and also activate the activity of the cerebral cortex. Nerve impulses passing through the cells of the reticular formation are amplified or weakened; the reticular formation has an excitatory or inhibitory effect on them. Impulses going through the reticular formation to the cerebral cortex maintain the working tone of the cortex. In connection with these functions, the reticular formation is called the activating system.
The foreign region of the diencephalon consists of two pairs of geniculate bodies. outdoor(lateral) cranked bodies are the subcortical center of vision, medial geniculate bodies subcortical center of hearing. In the external geniculate bodies, part of the fibers of the visual pathway ends, going to the brain from the retina. On the nerve cells of the medial geniculate bodies, fibers terminate, carrying auditory sensitivity from the cells of the inner ear that perceive sound irritations.
The axons of the nerve cells of the geniculate bodies are sent to the corresponding centers (visual, auditory) located in the cerebral cortex. In the white matter of the cerebral hemispheres, these fibers form the so-called visual and auditory radiance.
The epithelium is relatively small. It is located above the back of the thalamus. The epithelium is formed leashes. triangles of leashes and soldering leashes, which are associated with the endocrine gland - the pineal gland, which is involved in the regulation of processes occurring in the body rhythmically (cyclically).
The hypothalamus (hypothalamus) is located in front of the legs of the brain. The hypothalamic region includes a number of structures: the optic chiasm, the gray tubercle, the infundibulum, and the mastoid bodies. Mastoid bodies have a spherical shape. On the cells of the mastoid bodies, part of the fibers of the olfactory pathway ends. In front of the mastoid bodies lies gray bump. Tapering down, the gray tubercle turns into funnel, penetrating into the pituitary fossa of the body of the sphenoid bone. On the funnel, as it were, the pituitary gland, the endocrine gland, is suspended. Anterior to the gray tubercle, the optic nerves form visual intersection. The cavity of the diencephalon is III ventricle, looking like narrow gap, limited on the sides by the inner surface of the thalamus, and from below - by the upper part of the hypothalamus (hypothalamus). The upper wall of the third ventricle is formed by the fornix of the brain, to which the choroid plexus of the third ventricle, which produces cerebrospinal fluid, is adjacent from below. In its posterior part, the third ventricle communicates with the fourth ventricle through a narrow cavity of the midbrain - the aqueduct of the brain.
Internal structure of the hypothalamus. The gray matter of the hypothalamus is represented by clusters of nerve cells - nuclei, which are grouped in the anterior, middle and posterior sections of the hypothalamus. Among the nerve cells of the hypothalamus are many secretory neurons, which combine the properties of nerve and endocrine cells, being neurosecretory cells. Secretory neurons of the anterior hypothalamus synthesize biologically active substances that pass along the axons to the posterior pituitary gland. Small neurosecretory cells of the middle section of the hypothalamic region produce substances that control the hormone-forming activity of the anterior pituitary gland (adenohypophysis). At the same time, one part of biologically active substances stimulates the release and production of hormones by the cells of the anterior pituitary gland, and the other inhibits their function. Thus, the hypothalamus is the link between the nervous and endocrine systems.
Cortex
The cerebral cortex is the newest formation in terms of its evolutionary development. The thickness of the cerebral cortex (CBP) is 1.3-4.5 mm. The cortex contains from 10 to 18 billion nerve cells. The surface area of the CBP is 2200 cm2. The main cells of the CPB are pyramidal, stellate, and fusiform.
The main afferents enter the CBP along the fibers of the thalamocortical pathway.
CBP is characterized by numerous interneuronal connections, the number of which increases intensively up to 18 years. The final maturation of the CPB ends by the age of 22-23.
Based on the density and shape of neurons, Brodman divided the CBP into 53 cytoaritectonic fields.
The morpho-functional unit of the CBP is vertical column that performs a specific function. The vertical column is a large pyramidal cells with neurons located above and below them, which form a functional association. All neurons of the column respond to stimulation of the same receptor with the same reaction and jointly form an efferent response. The spread of excitation from one column to a nearby one is limited by lateral inhibition
There are several areas in the cortex:
motor zone. When it is stimulated, various movements appear.
Sensory zone. This area of the cortex receives specific afferent impulses from receptors from the periphery.
Association zones. These areas of the cortex receive information from various receptor fields of the CBP.
In the KBP, areas with less defined functions are distinguished. Yes, a large part frontal lobes, especially on the right side, can be removed without noticeable damage. However, if bilateral removal of the frontal areas is performed, severe mental disorders occur.
The projection zones of the analyzers are located in the cortex. According to their structure and functional significance, they were divided into 3 main groups of fields:
1.Primary fields(nuclear zones of analyzers).
2. Secondary fields
3. Tertiary fields.
Primary fields are associated with the sense organs and movement. They ripen early. I.P. Pavlov called them the nuclear zones of the analyzers. They carry out the primary analysis of individual stimuli that enter the cortex. If there is a violation of the primary fields to which information comes from the organ of vision or hearing, then cortical blindness or deafness occurs.
Secondary fields are the peripheral zones of the analyzers. They are located next to the primary and are connected with the senses through the primary fields. In these fields, generalization and further processing of information takes place. With the defeat of secondary fields, a person sees, hears, but does not recognize and does not understand the meaning of the signals.
Tertiary fields are analyzer overlap zones. They are located on the borders of the parietal, temporal and occipital regions, as well as in the anterior part of the frontal lobes. In the process of ontogenesis, they mature later. These fields ensure the coordinated work of both hemispheres. Here the highest analysis and synthesis takes place, goals and tasks are developed. Tertiary fields have extensive connections.
The presence of structurally different fields in the CBP also implies their different functional significance. In the CBP, sensory, motor and associative areas are distinguished.
Sensory zones. Each hemisphere has two sensory areas:
Somatic(skin, muscle, joint sensitivity).
Visceral, this zone of the cortex receives impulses from the internal organs.
The somatic zone is located in the region of the postcentral gyrus. This zone receives information from the skin and the motor apparatus from the specific nuclei of the thalamus. The skin receptor system is projected onto the posterior central gyrus. A large surface is occupied by the representation of the receptors of the hands, mimic muscles of the face, the vocal apparatus, and much less from the thigh, lower leg and torso, since fewer receptors are localized in these areas.
The second somatosensory zone is localized in the region of the Sylvian furrow. In this zone, integration and critical evaluation of information from specific nuclei of the thalamus takes place. For example, the visual zone is localized in the occipital lobe in the region of the spur groove. The auditory system is projected into the temporal lobe (Geshl's gyrus).
All sensory and motor areas occupy less than 20% of the CBP surface. The rest of the bark is association area. Each association area of the CPB is associated with several projection areas. The association areas of the cortex include parts of the parietal, frontal, and temporal lobes. The boundaries of associative fields are fuzzy. The neurons of the association areas are involved in the integration of various information. Here comes the highest analysis and synthesis of stimuli. As a result, complex elements of consciousness are formed. The parietal cortex is involved in assessing the biological significance of information and spatial perception. The frontal lobes (fields 9-14) together with the limbic system controls motivational behavior and carry out the programming of behavioral acts. If areas of the frontal lobes are destroyed, memory impairment occurs.
EEG rhythms
Alpha - rhythm 8 -13 pulses / sec,
amplitude 50 µV
Beta - rhythm 14-30 pulses / sec,
amplitude 25 µV
Theta - rhythm 4-8 pulses/sec
delta - rhythm 0.5-3.5 pulses/sec
amplitude 100 - 300 µV
Electrical activity of the cortex
Changes in the functional state of the cortex are reflected in its biopotentials. Spontaneous electrical oscillations with a certain periodicity are called electroencephalography (EEG).
EEG is widely used in the clinic, as it allows you to assess the state of the cortex, obtain information about the depth of anesthesia, the localization of the pathological process.
The following EEG rhythms are distinguished:
α-rhythm- frequency 8-13 per second, amplitude - 50 μV. This rhythm is recorded at rest, in the absence of external stimuli, when the person is in a comfortable position with his eyes closed.
beta rhythm- frequency 14-30 per second, amplitude - 25 μV. This rhythm is recorded when a person enters an active state and indicates desynchronization of the cortex.
Theta rhythm- frequency 4-7 Hz, amplitude - 100-300 μV. It is registered during the transition from a state of rest to a state of concentration of attention or to sleep.
delta rhythm- frequency 3-5 Hz, amplitude - 100-300 μV.
Registered during deep sleep, with loss of consciousness, during anesthesia. In awake people, the delta rhythm is not fixed, but it is characteristic of the hippocampus even in an active state.
Interhemispheric asymmetry of the brain
Left hemisphere
Verbal, forms temporal relationships, performs analysis, sequence of perceptions, abstract perception
Right hemisphere
Non-verbal, forms spatial relationships, carries out synthesis, simultaneous and concrete perception
Functional asymmetry of the brain.
There are 3 types of asymmetry:
Motor- uneven motor activity of the muscles of the right and left halves of the body.
touch- unequal perception of information by the right and left hemispheres.
mental. People who are dominant left hemisphere, prone to theories, have a large vocabulary, talk a lot, are mobile, purposeful and able to make predictions.
People who are dominant right hemisphere, prefer specific activities, slow, talk little, very sentimental, prone to memories.
Recently, the concept of the complementary influence of both hemispheres of the CBP has been adopted. This means that the advantage of one hemisphere can only be expressed in one kind of activity.
Asymmetry
Motor - uneven motor activity of the muscles of the arms, legs, face.
touch - unequal perception of objects by each of the hemispheres of objects on the left and on the right
Mental: "left-brained person", "right-brained person".
