Activity of the cerebral cortex
The activity of the cerebral cortex is carried out through the interaction of two main nervous processes - excitation and inhibition, which underlie the formation and assimilation of conditioned reflexes. These processes, under the influence of external or internal influences, can be strengthened or weakened, covering larger or smaller areas of the cerebral cortex.
The spread of excitation or inhibition processes in the cerebral cortex is called irradiation.
The coverage of an ever smaller number of nerve centers in the cortex by these processes is called concentration.
Excitation or inhibition in one area of the cortex is accompanied by the appearance reverse process in another area, what is called negative induction.
The excitability of the same area of the cerebral cortex decreases after excitation and increases after inhibition processes. This phenomenon is called by sequential induction.
The teachings of I. P. Pavlov about the reflex nature of the activity of the central nervous system there are three main principles: the principle of determinism, the principle of unity of analysis and synthesis And principle of structure.
The principle of determinism. In nature, including in a living organism, nothing happens without a reason. Any reflex act has a reason. This is one of the main provisions of dialectical materialism.
The principle of unity of analysis and synthesis. Nervous system in process? throughout all activities, it continuously breaks down complex stimuli acting on the human senses into simpler component elements (analysis) and immediately combines them into systems appropriate to the situation (synthesis).
The principle of structure. Any reflex act is associated with a specific area of the cerebral cortex. All processes occurring in the brain, as in the entire body, are material; they are based on material processes occurring in certain parts of the nervous system.
He receives all the information that the driver needs to reliably drive a car using analyzers. Each analyzer consists of three sections. First department- external, perceiving apparatus in which the energy of the influencing stimulus is converted into a nervous process. These are external anatomical formations, or sensory organs (eye, ear, nose, etc.). Second from affairs - These are sensory nerves through which the acting irritation is transmitted to the corresponding center of the brain. Third department and there is such a center, which is a specialized area of the cerebral cortex that converts nerve stimulation into the corresponding sensation (visual, sound, gustatory, thermal, etc.). So, for example, in the visual analyzer, the first, outer section is the inner shell of the eyeball (retina), consisting of light-sensitive cells - cones and rods. The stimulation of these cells, transmitted along the optic nerve to the center of the visual analyzer, gives the sensation of light, color and visual perception of objects in the outside world. Other analyzers are arranged similarly: auditory, cutaneous, olfactory, vestibular and motor. The central sections of the analyzers are located in different areas of the cerebral cortex. So, for example, the center of the visual analyzer is in the occipital region, the auditory one - in the temporal region, the motor one - in the central gyrus of the brain, etc.
In addition to specific properties, analyzers also have general properties. A common property of analyzers is their high excitability, which is expressed in the appearance of a focus of excitation in the cerebral cortex even with a small stimulus strength. All analyzers are characterized by irradiation of excitation, when excitation from the center of the analyzer spreads to neighboring areas of the cerebral cortex. The next common feature of analyzers is adaptation, i.e. the ability to perceive stimuli of varying strength over a wide range. For example, when entering a dark hall, a person initially sees nothing, and then quite well distinguishes not only the outlines of objects, but also faces. The water seems hot only at the first moment of immersion in the bath, bad smell quickly ceases to be felt, etc. Adaptation of analyzers to stimuli is expressed both in an increase in sensitivity (dark adaptation) and in a decrease (light adaptation). Analyzers have the ability to maintain the process of excitation and perception for some time after the cessation of the stimulus. If you quickly move a glowing coal in the dark, then instead of a moving point you will see a continuous luminous stripe. In addition, all analyzers have their own specific memory.
Analyzers
Distinguish external And internal analyzers. External analyzers perceive information from environment. These include: visual, auditory, olfactory, gustatory, tactile, or tactile, responsive to touch or pressure. Internal analyzers perceive irritation from the internal environment of the body. These include: musculomotor, assessing the position of the body in space, mutual arrangement parts of the body that perceive muscle tension and contraction; barosthetic, responding to changes in blood pressure, etc. Temperature, pain And vestibular analyzers can be excited by the action of stimuli from the external and internal environment.
Highest value in the driver's activity they have visual, auditory, vestibular, musculomotor and skin analyzers.
It has been established that from 80 to 90% of information from the outside world enters the brain through visual analyzer. The wall of the eye consists of three membranes. The outer shell is called the protein, or sclera. In the front part of the eyeball, it turns into a transparent cornea, through which rays of light penetrate the eye. Behind the cornea is the iris, which acts as a diaphragm. In the center of the iris there is a hole - the pupil. Behind the pupil is a lens shaped like a biconvex lens. Behind the lens is a jelly-like vitreous body that fills the entire cavity of the eye.
Rays of light, penetrating through the transparent, refractive media of the eye (cornea, lens, vitreous body), fall on the inner shell of the eye - the retina, which is the apparatus that perceives light rays. The endings of the optic nerve, which transmits visual impulses to the brain, approach the retina. The retina has two types of cells that perceive light stimulation: rods and cones. Daytime vision is carried out mainly by cells of low sensitivity - cones, while the rods are not excited. IN dark time days, rods begin to function, which provide visual perception in low light conditions.
In diurnal animals, cones predominate in the retina, while in nocturnal animals (owls, the bats) - sticks. The composition of the sticks includes a special Chemical substance- visual purple, or rhodopsin. Weak light causes the breakdown of rhodopsin. The products of this decay excite the rods, and then the excitation is transmitted along the optic nerve to the cerebral cortex. This is how the feeling of light arises. Rhodopsin contains vitamin A. With its deficiency, visual purple is not synthesized, and a person ceases to see at dusk. This condition is called night blindness, which is especially dangerous for the driver when driving at night. Mixing three primary colors in different combinations: Red Green And blue, You can get a variety of colors. This phenomenon formed the basis of the theory of color vision, according to which there are three types of cones in the retina. Some are excited by red, others by green, and others by blue. The combination of varying degrees of excitation in the three types of cones gives all the other colors. When all cones are uniformly stimulated, a sensation of white color occurs.
Hearing analyzer perceives sounds of varying heights, strengths and durations. The hearing organ consists of three parts: external, middle And inner ear. The outer ear is represented by the auricle and the external auditory canal, 2.5 cm long. Between the auditory canal and the middle ear cavity there is an eardrum 0.1 mm thick. Due to its elasticity, the eardrum is capable of repeating air vibrations without distortion. The middle ear cavity contains three auditory ossicles: the malleus, the incus and the stapes. The ossicles transmit vibrations of the eardrum to the cochlea (the so-called narrow curved bone canal). The middle ear cavity is connected to the nasopharynx by a special canal - the Eustachian tube. With the help of the Eustachian tube, pressure equal to atmospheric pressure is maintained in the middle ear, which ensures undistorted vibration of the eardrum. These vibrations are transmitted to the organ of Corti of the inner ear, which is located in the cochlea. The organ of Corti has a main membrane on which the finest fibers are stretched. There are about 24 thousand such fibers. Sound waves cause vibrations in fibers that excite the endings of the auditory nerve. This excitation is transmitted to the temporal region of the cerebral cortex and is perceived as a sensation of sound. According to the theory of hearing, the fibers of the wide part of the cochlea in the apex region are weakly stretched and perceive low tones. Short and highly stretched fibers at the base of the cochlea respond by oscillating to high tones. Vestibular analyzer takes part in the perception of movement and body position. The peripheral part of the vestibular analyzer consists of the vestibule and semicircular canals, which are also located in the inner ear. The vestibule is a small cavity, on both sides of which there is a cochlea and three semicircular canals. The semicircular canals are located in three mutually perpendicular planes and their ends open into the cavity of the vestibule. In this part of each channel there are sensory endings (receptors) of the vestibular nerve. When moving or changing the position of the body, these endings are irritated by the movement of the fluid in the canal, which is called endolymph. Excitation is transmitted to the cerebral cortex and is perceived as movement or a change in the position of the body in space. Significant irritation of the vestibular apparatus occurs when rocking at sea, bumpy in the air and when driving a car. As a result of such motion sickness, seasickness or air sickness develops, which causes headache, dizziness, general weakness, sweating, nausea and vomiting. This condition occurs more often among passengers and very rarely among car drivers.
Musculoskeletal analyzer has exclusively great importance in the activities of the car driver, as he exercises control over the correctness and accuracy of the movements performed. Muscles and joints contain sensitive nerve cells which are called proprioceptors. When muscles contract or change body position, these cells send impulses to the cerebral cortex, signaling muscle contraction or relaxation, or the slightest change in the position of any part of the body in space.
Thanks to such information, you can determine with your eyes closed what position the limbs and body are in. As for the driver, with the help of a motor analyzer he instantly receives information about the slightest deviation of the car, as well as the position of the controls. This information has great value for timely driver control actions in dangerous road situations. The motor analyzer plays a leading role in the formation of new movements, in the formation and improvement of motor driving skills. Under the influence of professional training, the excitability and, consequently, the sensitivity of the motor analyzer increases, which makes it possible to obtain from it more and more accurate information necessary for reliable driving. Automation of motor skills allows you to relieve the driver’s attention, which is very important for road safety.
Skin analyzer responds to pain, temperature and tactile stimuli. Tactile stimuli provide the driver Additional information about changing the speed or direction of the vehicle.
All analyzers play an important role in the driver's performance, and disruption of their functions can dramatically reduce their reliability.
Control questions
1. Tell us about the role of human anatomy and physiology in engineering psychology.
2. What types is the human nervous system divided into?
3. What is called a reflex?
4. What is irradiation?
5.Tell us about the importance of visual, auditory, vestibular, musculo-motor and skin analyzers in a driver’s activity
Feeling and perception of the car driver
The goal is to give the concept of sensation and perception.
1. Mental processes of obtaining information.
2. Visual perception of the driver.
3. Perception of time.
4. Motor perception.
5. Perception of sounds.
6. Illusions and hallucinations.
1. The cerebral cortex performs the function of higher analysis of signals coming from all receptors of the body and the organ of higher synthesis of responses into a biologically appropriate act.
2. The cerebral cortex is the highest organ of coordination of reflex activity. She is able to start and slow down. coordinate the work of underlying departments and floors of the central nervous system.
3. The cerebral cortex, as the highest organ of coordination of reflex activity, forms biologically appropriate reactions that ensure the body’s adaptation to the external environment, reactions that balance the body with the external environment.
4. At the highest stage of its development, the central nervous system, the cortex of the large hemispheres, acquires another function; it becomes an organ of mental activity. Based on physiological processes, sensations and perceptions arise in it, and thinking appears. The cerebral cortex is the organ of thinking. The human brain, its highest part of the cerebral cortex, provides the opportunity social life, provides the opportunity for communication, knowledge of the surrounding world, knowledge of nature.
Anatomy and histology of the cortex
The cerebral cortex is the most advanced apparatus of the central nervous system. It got its name because it covers the brain on all sides, like the bark of a tree surrounds its trunk. It is cut with many grooves and convolutions. On top it is covered with a layer of neurons, the thickness of which varies between 2-4 mm, averaging 2.5 mm. The cortex contains about 49 billion cells, i.e. 14/15 of all neurons. (Starting from the age of 20, about 100 thousand cortical neurons die every day). The main part of the cortex consists of white matter. The white matter of the forebrain is formed by the axons of these cells, as well as the axons of various ascending pathways. As in any nerve center, the cortex has sensory neurons that perceive information from the afferent pathways, efferent neurons that send orders along the descending pathways, and intercalary or associative neurons that make up the bulk. Due to the processes of associative neurons, the cortex is united into a single whole: excitation that arises in one area can cover the entire cortex.
Depending on the phylogeny, in accordance with the history of the development of the cerebral cortex, 3 parts are distinguished.
1. Ancient cortex - archicortix. The ancient cortex includes the olfactory bulbs (afferent fibers from the olfactory epithelium of the nasal mucosa come here), olfactory tracts (located on the lower surface of the frontal lobe) and olfactory tubercles (secondary olfactory centers are located here).
2. Old cortex - paleocortex. The old cortex includes the cingulate gyrus, hippocampus, and amygdala. All these formations are part of the limbic system, which is the highest division of the autonomic nervous system.
3. New cortex - neocortex. The neocortex includes all other areas of the cerebral cortex: frontal, temporal, occipital, parietal lobes.
In the process of phylogenesis, the new cortex first appears in mammals and reaches its highest development in humans, i.e., it is the youngest nervous structure, and in humans it carries out the highest regulation of body functions and psychophysiological processes that provide various forms of behavior.
Cytoarchitecture of the cortex(location and interconnection of neurons in the cortex). If the ancient bark has 3 layers, then the new bark has a 6-layer structure.
1.The most superficial layer is molecular. In this layer there are very few nerve cells, but there are many branching fibers of the underlying cells, which form a dense network of plexuses.
2. The second layer is the outer granular layer, represented mainly by stellate cells and partially by small pyramidal cells. The fibers of the cells of the second layer are located mainly along the surface of the cortex, forming cortico-cortical connections.
3. The third layer is the outer pyramidal layer, consists mainly of pyramidal cells average size. The axons of these cells, like granule cells of layer II, form cortico-cortical associative connections.
4 The inner granular layer is similar in the nature of the cells (stellate cells) and the arrangement of their fibers to the outer granular layer. In this layer, afferent fibers coming from neurons of specific nuclei of the thalamus have synaptic endings; The highest capillarization density is noted here.
5. Inner pyramidal layer or layer of Betz cells. This layer consists mainly of medium and large pyramidal cells. But in this layer in the precentral gyrus there are large, giant pyramidal cells, Betz cells. The long dendrites of these cells go upward and reach the surface layer - these are the so-called apical dendrites. The axons of Betz cells go to various nuclei of the brain and spinal cord, forming efferent corticospinal and corticobulbar motor tracts. The longest axons are part of the pyramidal tract and reach the lower segments of the spinal cord, ending on intercalary cells and a-motoneurons of the spinal cord.
6. The layer of polymorphic cells is formed mainly by spindle-shaped cells, the axons of which form the corticothalamic tracts.
Input afferent impulses enter the cortex from below, rise to the cells of Ⅲ - Ⅴ layers of the cortex, here the perception and processing of signals entering the cortex occurs.
The main efferent connections of the cerebral cortex are the efferent pathways leaving the cortex, which are formed mainly in layers V-VI.
A more detailed division of the cortex into various fields was carried out on the basis of cytoarchitectonic characteristics by K. Brodman (1909), who identified 52 fields; many of them are characterized by functional and neurochemical features.
Histological evidence shows that the elementary neural circuits involved in information processing are located perpendicular to the surface of the cortex. In the cerebral cortex there are functional associations neurons located in a cylinder with a diameter of 0.5-1.0 mm. These associations were called neural columns . They are found in the motor cortex, in different zones sensory cortex. Adjacent neural columns can interact with each other.
Thus, different areas of the neocortex have a clear, stereotypical structure.
But despite the commonality of the neural organization of the entire cortex, different sections of the cortex differ from each other. The differences lie in the number and size of neurons, the course of fibers, the branching of axons and dendrites. These differences are due to the different functions of different areas of the cortex. Each section, area of the cortex performs a specific function; there is a functional specialization of different areas of the cortex.
Brain located in the brain part of the skull. Its average weight is 1360 g. There are three large sections of the brain: the brainstem, the subcortical section and the cerebral hemisphere. 12 pairs of cranial nerves emerge from the base of the brain.
1 - upper section spinal cord; 2 - medulla oblongata, 3 - pons, 4 - cerebellum; 5 - midbrain; 6 - quadrigeminal; 7 - diencephalon; 8 - cerebral cortex; 9 - corpus callosum, connecting the right hemisphere to the new one; 10 - optic chiasm; 11 - olfactory bulbs.
Sections of the brain and their functions
|
Brain parts |
Department structures |
Functions |
|
|
BRAINSTEM |
hindbrain |
Medulla Here are the nuclei with departing pairs of cranial nerves: XII - sublingual; XI - additional; X - wandering; IX - glossopharyngeal nerves |
Conductor - connection between the spinal and overlying parts of the brain. Reflex: 1) regulation of the activity of the respiratory, cardiovascular and digestive systems; 2) food reflexes of salivation, chewing, swallowing; 3) protective reflexes: sneezing, blinking, coughing, vomiting; |
|
Pons contains nuclei: VIII - auditory; VII - facial; VI - outlet; V - trigeminal nerves. |
Conductor - contains ascending and descending nerve pathways and nerve fibers connecting the cerebellar hemispheres to each other and to the cerebral cortex. Reflex - responsible for vestibular and cervical reflexes that regulate muscle tone, incl. facial muscles. |
||
|
Cerebellum The cerebellar hemispheres are connected to each other and are formed by gray and white matter. |
Coordination of voluntary movements and maintaining body position in space. Regulation of muscle tone and balance. |
||
|
Reticular formation- a network of nerve fibers intertwining the brain stem and diencephalon. Provides interaction between the ascending and descending pathways of the brain, coordination of various body functions and regulation of the excitability of all parts of the central nervous system. |
|||
|
Midbrain |
Four Hills With the nuclei of the primary visual and auditory centers. Brain stems With nuclei IV - oculomotor III - trochlear nerves. |
Conductor. Reflexive: 1) indicative reflexes to visual and sound stimuli, which manifest themselves in turning the head and body; 2) regulation of muscle tone and body posture. |
|
|
SUBCORTEX |
Forebrain |
Diencephalon: a) thalamus (optic thalamus) with nuclei ll th pair of optic nerves; |
Collection and evaluation of all incoming information from the senses. Isolation and transmission to the cerebral cortex most important information. Regulation of emotional behavior. |
|
b) hypothalamus. |
The highest subcortical center of the autonomic nervous system and all vital functions of the body. Ensuring the constancy of the internal environment and metabolic processes of the body. Regulation of motivated behavior and provision defensive reactions(thirst, hunger, satiety, fear, rage, pleasure and displeasure). Participation in the transition between sleep and wakefulness. |
||
|
Basal ganglia (subcortical nuclei) |
Role in the regulation and coordination of motor activity (together with the thalamus and cerebellum). Participation in the creation and memorization of programs for purposeful movements, learning and memory. |
||
|
CORTEX OF THE LARGE HEMISPHERES |
Ancient and old bark (olfactory and visceral brain)Contains the nuclei of the 1st pair of olfactory nerves. |
The ancient and old cortex, together with some subcortical structures, formslimbic system, which: 1) is responsible for innate behavioral acts and the formation of emotions; 2) provides homeostasis and control of reactions aimed at self-preservation and preservation of the species: 3 affects the regulation of autonomic functions. |
|
|
New crust |
1) Carries out the highest nervous activity, is responsible for complex conscious behavior and thinking. The development of morality, will, and intelligence are associated with the activity of the cortex. 2) Performs perception, evaluation and processing of all incoming information from the senses. 3) Coordinates the activities of all body systems. 4) Provides interaction of the body with the external environment. |
||
Cerebral cortex
Cerebral cortex- phylogenetically the youngest brain formation. Due to the furrows total area the surface area of the adult human cortex is 1700–2000 cm2. The cortex contains from 12 to 18 billion nerve cells, which are located in several layers. The cortex is a layer of gray matter 1.5-4 mm thick.
The picture below shows functional areas and lobes of the cerebral cortex
|
Location of gray and white matter |
Hemisphere shares |
Hemisphere zones |
|
|
The cortex is gray matter, the white matter is located under the cortex, in the white matter there are accumulations of gray matter in the form of nuclei |
Speech centers |
||
|
Parietal |
Skin-muscular zone |
Control of movements, ability to distinguish irritations |
|
|
Temporal |
Auditory zone |
Arcs of reflexes that distinguish between sound stimuli |
|
|
Gustatory and olfactory zones |
Reflexes for distinguishing tastes and smells |
||
|
Occipital |
Visual area |
Discrimination of visual stimuli |
Sensory and motor areas of the cerebral cortex
|
Left hemisphere of the brain |
Right hemisphere of the brain |
|
The left hemisphere (“mental”, logical) is responsible for the regulation of speech activity, oral speech, writing, counting and logical thinking. Dominant in right-handers. |
The right hemisphere (“artistic”, emotional) is involved in the recognition of visual, musical images, the shape and structure of objects, and in conscious orientation in space. |
|
Cross section of the left hemisphere through the sensory centers
Representation of the body in the sensitive zone of the cerebral cortex. The sensitive area of each hemisphere receives information from the muscles, skin and internal organs of the opposite side of the body. |
Cross section of the right hemisphere through the motor centers
Representation of the body in the motor zone of the cerebral cortex. Each region of the motor zone controls the movement of a specific muscle. |
_______________
A source of information:
Biology in tables and diagrams./ Edition 2, - St. Petersburg: 2004.
Rezanova E.A. Human biology. In tables and diagrams./ M.: 2008.
The brain is the main organ of a person, controlling all his life functions, determining his personality, behavior and consciousness. Its structure is extremely complex and is a combination of billions of neurons grouped into sections, each of which performs its own function. Many years of research have revealed a lot about this organ.
What parts does the brain consist of?
The human brain consists of several sections. Each of them performs its function, ensuring the vital functions of the body.
The structure of the brain is divided into 5 main sections.
Among them:
- Oblong. This part is a continuation of the spinal cord. It consists of gray matter nuclei and white matter tracts. It is this part that determines the connection between the brain and the body.
- Average. It consists of 4 tubercles, two of which are responsible for vision and two for hearing.
- Rear. The hindbrain includes the pons and cerebellum. This is a small section in the back of the head, which weighs around 140 grams. Consists of two hemispheres connected to each other.
- Intermediate. Consists of the thalamus, hypothalamus.
- Finite. This section forms both hemispheres of the brain, connected by the corpus callosum. The surface is full of convolutions and grooves covered by the cerebral cortex. The hemispheres are divided into lobes: frontal, parietal, temporal and occipital.
The last section occupies more than 80% of the total mass of the organ. The brain can also be divided into 3 parts: the cerebellum, the brainstem and the cerebral hemispheres.
In this case, the entire brain is covered in the form of a shell, divided into three components:
- Arachnoid (cerebrospinal fluid circulates through it)
- Soft (adjacent to the brain and full of blood vessels)
- Hard (in contact with the skull and protects the brain from damage)
All components of the brain are important in the regulation of life and have a specific function. But the activity regulation centers are located in the cerebral cortex.
The human brain consists of many sections, each of which has a complex structure and performs a specific role. The largest of them is the terminal one, which consists of the cerebral hemispheres. All this is covered with three shells that provide protective and nourishing functions.
Learn about the structure and functions of the brain from the video provided.
What functions does it perform?
The brain and its cortex perform a number of important functions.
Brain
It is difficult to list all the functions of the brain, because it is an extremely complex organ. This includes all aspects of the human body. However, it is possible to identify the main functions performed by the brain.
The functions of the brain include all human senses. These are vision, hearing, taste, smell and touch. All of them are performed in the cerebral cortex. It is also responsible for many other aspects of life, including motor function.
In addition, diseases can occur against the background of external infections. The same meningitis that occurs due to infections of pneumococcus, meningococcus and the like. The development of the disease is characterized by pain in the head, fever, pain in the eyes and many other symptoms such as weakness, nausea and drowsiness.
Many diseases that develop in the brain and its cortex have not yet been studied. Therefore, their treatment is complicated by a lack of information. So it is recommended to consult a doctor at the first non-standard symptoms, which will prevent the disease by diagnosing it at an early stage.
Functions of the spinal cord
In the white matter of the spinal cord, adjacent to the gray matter between the anterior and posterior horns, there is reticular formation. This formation is formed by clusters of nerve cells that have numerous connections with each other. R eticular formation ensures the activity of other spinal cord neurons due to the property of automaticity (see below).
Autonomic reflexes(vasomotor, sweating, genitourinary, defecatory) are caused by the presence of centers of the autonomic nervous system in the spinal cord (see below).
Conductor functions
They are carried out according to the Bell-Magendie law: afferent information enters the spinal cord through the dorsal roots, efferent impulses are transmitted through the anterior roots.
Ascending (sensitive) pathways spinal cord located in rear pillars white substances and carry information from the external world and the internal environment of the body:
1) from skin receptors (pain, temperature, touch, pressure, vibration);
2) from proprioceptors (muscle spindles, Golgi tendon receptors, periosteum and joint membranes);
3) from receptors of internal organs - visceroreceptors (mechano- and chemoreceptors).
Descending (motor) tracts located in front pillars and transmit impulses to the skeletal muscles about voluntary (conscious) movements, tonic influences on the muscles, impulses that ensure the maintenance of posture and balance. Autonomic influences (on internal organs) are also transmitted through descending pathways.
The conduction functions are similar in other stem structures (medulla oblongata, midbrain and pons): afferent pathways pass through the posterior group of white fibers, and efferent pathways pass through the anterior group.
Functions of the medulla oblongata
Main the function of the pyramids is to carry out signals about voluntary movements.
The functions of the olivary nuclei are related to maintaining balance.
In the medulla oblongata there are nuclei of the VIII-XII cranial nerves, therefore, the medulla oblongata carries out protective reflexes (coughing, sneezing, vomiting, lacrimation, closing the eyelids, constricting the pupil) (see).
The medulla oblongata performs sensory functions: reception of skin sensitivity of the face, primary analysis of taste. The medulla oblongata receives signals from chemoreceptors and baroreceptors of blood vessels, interoreceptors of internal organs and vestibuloreceptors. The influence of these structures determines the functioning at the level of the medulla oblongata respiratory, cardiac and vascular centers. The structures of the reticular formation also perform regulatory functions skeletal muscle tone.
Conducting functions - see spinal cord.
Hindbrain structures
The hindbrain includes the pons and cerebellum.
Bridge facial(VII pair) and vestibulocochlear (VIII pair) nerves.
Responsible for the physiological reaction of stress and anxiety, participates in sleep mechanisms. Many of its neurons noradrenergic.
Bridge functions:
· conductive (prevail);
· ensures maintaining posture and maintaining body balance in space when changing speed;
Provides tone to the neck muscles;
· contains vegetative centers for the regulation of respiration (pneumotoxic center), heart rate, and gastrointestinal tract activity.
· regulates chewing and swallowing (see. Complex brainstem reflexes);
· plays an important role in the activation of the cerebral cortex (including in a state of anxiety);
· limits sensory inflows of nerve impulses to the cerebral hemispheres during sleep.
Cerebellum
The functions of the cerebellum are mainly related to organization of motor acts And regulation of autonomic functions. From the motor cortex and basal ganglia, the cerebellum receives information about the planned movement, as well as afferentation from the somatosensory system. The cerebellum provides mutual coordination of movements, and correction of the performed movement(necessary, because when performing a motor act, moving parts of the body are influenced by inertial forces, which disrupts the smoothness and accuracy of the movement performed).
Functions of the cerebellum:
· maintaining body posture and balance;
· coordination of targeted movements;
· construction of fast ballistic movements;
· regulation of muscle tone;
· regulation of autonomic functions (heartbeat, vascular tone, intestinal motility, etc.);
· conductor.
Functions of the midbrain
In the midbrain there is a dorsally located roof and ventrally extending cerebral peduncles.
reticular formation, kernels oculomotor And bloc cranial nerves (III-IV pair).
The roof of the midbrain consists of four eminences ( quadrigeminal) - hillocks that look like hemispheres.
Brain stemsare represented by two thick, longitudinally striated ridges going to the right and left hemispheres of the cerebrum. In the thickness of the cerebral peduncles there are paired nuclei of substantia nigra. They lie in the tire nuclei of the extrapyramidal motor system (red nuclei, substantia nigra and etc.).
Cranial nerve nuclei (III-V) And reticular formation participate in the implementation complex brain stem reflexes.
Black substance- one of the areas of the brain that produces dopamine. Besides, substantia nigra performs a number of important functions: regulation of muscle tone, especially during sleep, ensuring homeostasis, and is part of the body's anti-pain and sleep-forming systems.
Tonic reactions together with postural reflexes of the spinal cord, they ensure redistribution of the tone of various muscle groups when the position of the body or its individual parts (for example, the head) in space changes. They are divided into two groups: static and statokinetic. Static reactions occur when a change in body position is not associated with its movement in space (i.e. postural reflexes). Statokinetic reactions manifest themselves in the redistribution of skeletal muscle tone, which ensures the preservation of balance of the human body during angular and linear accelerations of active or passive movement in space
Diencephalon
Diencephalonthis is the uppermost part of the brain stem, the cavity of which is III ventricle. The diencephalon is located under corpus callosum And vault brain, most of it is surrounded by the hemispheres of the telencephalon. The diencephalon includes the visual thalamus (thalamus), subthalamus (hypothalamus), suprathalamic part (epithalamus) and postthalamic region (metathalamus). The diencephalon also includes two endocrine glands - pituitary And pineal gland(pineal body).
Thalamus
Thalamus (visual thalamus)are a collection of gray matter, ovoid in shape, connected interthalamic commissure. Its nerve cells are grouped into a large number of cores (up to 120). Functionally, the nuclei of the thalamus are divided into specific, nonspecific, associative And motor.
Specific kernels associated with certain sensitive areas of the cortex - auditory, visual, etc. (all except olfactory). Here the convergence of afferent signals occurs with the suppression of biologically insignificant ones. Nonspecific nuclei The thalamus is connected to many areas of the cortex and, together with the structures of the reticular formation, takes part in the formation of ascending activating influences. Associative kernels formed multipolar, the axons of which go to the layers of associative and partially projection areas. Associative nuclei are involved in higher integrative processes (multisensory convergence, etc.), but their functions have not yet been sufficiently studied. TO motor nuclei The thalamus includes the ventral nucleus, which has input from the cerebellum and basal ganglia, and at the same time gives projections to the motor zone of the cerebral cortex. This nucleus is included in the movement regulation system.
Hypothalamus
Hypothalamusforms the walls and bottom of the 3rd ventricle, hangs from it on a thin stalkpituitary . The hypothalamus secretes three areas of accumulation of nuclei: anterior, middle (medial) and posterior. In the anterior area hypothalamus is located supraoptic And paraventricular nuclei. The neurosecretory cells of these nuclei produce hormones that enter the posterior lobe of the pituitary gland (neurohypophysis). In the middle (medial) region neurons where neurohormones are produced liberins And statins, respectively activating or inhibiting the activity of the anterior pituitary gland ( adenohypophysis). To the cores posterior region include scattered large cells, as well as nuclei mastoid body.
The hypothalamus is a structure of the central nervous system that carries out complex integration of the functions of various internal organs to the overall functioning of the body. It changes the activity of the cardiovascular, respiratory and other visceral systems with changes in the external or internal environment (changes in weather conditions, physical activity, infections and other factors that threaten homeostasis). Depending on the performed vegetative functions There are two zones in the hypothalamus. The first zone is dynamogenic occupies the middle and posterior parts of the hypothalamus. When it is excited, “motor reactions” are observed: dilation of the pupil, increased heart rate, increased blood pressure, activation of breathing, increased motor excitability, i.e. manifestations of sympathetic influences autonomic nervous system. The second zone is trophogenic, its arousal manifests itself in constriction of the pupil, decreased blood pressure, decreased breathing, vomiting, defecation, urination, salivation, i.e. symptoms characteristic of influences of the parasympathetic nervous system.
The hypothalamus is located motivational centers: hunger, satiety, thirst, as well as sexual and aggressive-defensive centers. By receiving afferent flows of excitation from interoreceptors (osmoreceptors, chemoreceptors, thermoreceptors, etc.) and integrating them with humoral influences on the nerve cells of the hypothalamus, these centers form the corresponding motivational states of the body.
Limbic system
Limbic system(synonym: limbic complex, visceral brain) - a complex of structures of the midbrain, diencephalon and telencephalon involved in the organization of visceral, motivational and emotional reactions of the body. The limbic system is formed by: the olfactory bulb; olfactory tract; olfactory triangle; anterior perforated substance; cingulate gyrus; parahippocampal gyrus; hippocampus; amygdala; hypothalamus; mastoid body; reticular formation midbrain.
The limbic system has modulating influence on the cerebral cortex and subcortical structures, establishing, together with the reticular formation, the necessary their activity level(ascending: coma→deep sleep→shallow sleep (drowsiness)→quiet wakefulness→active wakefulness→excited state→affect). The limbic system controls emotions, the sleep-wake cycle, sexual behavior, and learning and memory processes. Receiving information about the external and internal environments of the body, the limbic system triggers autonomic and somatic emotional reactions (increased heart rate and breathing, increased blood pressure and sweating, muscle tension). Limbic formations are considered to be the highest integrative centers regulation of the body's vegetative functions. From them, excitation impulses are sent to the autonomic centers of the hypothalamus and through it to the pituitary gland and the stem and spinal nuclei of the autonomic nervous system. Due to their connections with the basal ganglia, the anterior parts of the thalamus and the reticular formation, limbic formations can influence the tone of skeletal muscles.
A special feature of the limbic system is that between its structures there are simple two-way connections and complex pathways that form many closed circles ( Peipes circle). Such an organization creates conditions for long-term circulation of the same excitation in the system and thus for the preservation of a single state in it and the imposition of this state on other brain systems ( excitation reverberation). This determines not only the tonic activation of the cerebral cortex, but also the strength and severity emotional states body; relates to memory and learning processes and short-term memory, regulates aggressive-defensive, eating and sexual behaviors.
Basal ganglia
In the white matter of the cerebral hemispheres, closer to its base, there is gray matter that forms the subcortical or basal ganglia: striatum, consisting of caudate lentiform nuclei (includes putamen, lateral and medial globus pallidus), velum, amygdala.
The basal ganglia occupy a central place among the structures systems of voluntary movements. (motor nuclei). With the participation of the basal ganglia, the synergism of all elements of such complex motor acts as walking, running, climbing occurs; smooth movements are achieved and the initial position for their implementation is established. The basal ganglia coordinate the tone and phasic motor activity of muscles. Their activity involves performing slow movements, such as walking slowly, stepping over an obstacle, or threading a needle.
The basal ganglia are involved not only in the regulation of motor activity, but also in the analysis of afferent flows, in the regulation of a number of autonomic functions, in the implementation complex shapes innate behavior, in the mechanisms of short-term memory, as well as in the regulation of the sleep-wake cycle.
Functions of the cerebral cortex
The highest department of the central nervous system is cerebral cortex. Different areas of the cerebral cortex have different fields, determined by the nature and number of neurons, the thickness of the layers, etc. The presence of structurally different fields also implies their different functional purposes.
Taking into account the functional characteristics of the fields of the neocortex, they are divided into primary, secondary And tertiary or associative. Primary and secondary fields unite sections of the cortex associated with the functioning of certain sensory systems.
1) Primary (projection) fields receive and process information from any sensory system. Here is carried out primary analysis sensory information within one modality (for example, for visual - color, illumination, shape). Modality - type of sensory sensation - auditory, visual, olfactory, etc.
Primary sensory and motor fields are strictly localized. Below are some of them.
In the cortex of the postcentral gyrus and superior parietal lobule lie nerve cells that form core of proprioceptive and general sensitivity(temperature, pain and tactile). Motor analyzer core located in the motor area of the cortex, which includes the precentral gyrus and the paracentral lobule of the medial surface of the hemisphere. The size and location of the projection zones of various organs in the somatosensitive and motor cortex depend on their functional significance.
In the depths of the lateral sulcus, on the surface of the middle part of the superior temporal gyrus facing the insula, there is auditory analyzer core. Located in the cortex of the middle temporal gyrus nucleus of the vestibular analyzer.
Visual analyzer core located on the medial surface occipital lobe, on both sides of the calcarine groove.
Speech centers are located in the left hemisphere of right-handers, and in the right hemisphere of left-handers. Motor Speech Analyzer Core(speech pronunciation) is located in the posterior parts of the inferior frontal gyrus ( Broca's center). Core of the auditory analyzer of oral speech(speech perception) is closely connected with the cortical auditory center and is located in the posterior parts of the superior temporal gyrus, on its surface facing the lateral sulcus ( Venike zone). Close to the core of the visual analyzer is the core of the visual analyzer of written speech.
Cortical sections taste And olfactory analyzers are located on the inferior surface of the temporal lobe, in the seahorse gyrus and the uncus on the inferior surface of the temporal lobe.
2) Secondary fields are located above the primary ones and occupy a large area. In addition to sensitive ones, they receive fibers from motivational and emotional centers, memory structures, etc. It is typical for them identification sensory images within one modality (for example, recognition of an object - nail, screw, rod, dowel, heel, mushroom, nipple, needle). Damage to secondary fields can lead to sensory agnosia (impaired recognition processes): visual, auditory, olfactory, gustatory, as well as sensory aphasia (impaired speech recognition).
3) Tertiary or associative fields occupy more than 50% of the entire surface of the hemispheres and are the youngest (in evolutionary terms). Tertiary fields have a close connection with the associative nuclei of the thalamus. Association zones provide contacts between the projection zones of individual analyzers and integrate their activities. They take part in multisensory information processing, the formation of responses and the implementation of complex forms of behavior. In addition, there are other types of convergence: sensory-biological (manifested in the convergence of afferent excitations of any sensory modality and motivational excitations associated with various biological states of the body (pain, hunger, etc.) to individual neurons of the cerebral cortex), multibiological and efferent- afferent The main associative areas are parieto-occipital(primarily a perceptual function) and frontal(organization and control of behavioral, mainly motor, reactions). The anterior frontal section are morphological substrate of mental activity (consciousness, thinking, learning, memory, emotions).