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Physiology of the cerebral cortex of the cerebral hemisphere

The large, or terminal, brain is one of the complex organs of man. The functions of this part of the central nervous system are significantly different from the functions of the stem and spinal cord. They form the basis of the physiology of higher nervous activity. Under the higher nervous activity I.P. Pavlov meant behavior, activity aimed at the adaptability of the body to changing environmental conditions, at equilibrium with the environment. I.P. Pavlov with his studies proved not only the reflex activity of the cerebral cortex, but also discovered a qualitatively new higher type of reflexes - conditioned reflexes. It was further found that conditioned reflexes are elementary acts that form the behavior of humans and animals. At the same time, it was found that damage to the cortex of the hemispheres in the experiment leads to an irrevocable loss of the acquired reactions developed in the process of individual life - conditioned reflexes. The morphological confirmation of the physiology and clinic data was the doctrine of the different-quality structure of the cerebral cortex of the cerebral hemispheres in different parts of it - cyto and myeloarchitectonics of the cortex. As a result of a detailed study, special maps of the cerebral cortex were created, reflecting the totality of the cortical ends and analyzers.

The analyzer is a nerve mechanism consisting of a receptor receptor apparatus, nerve impulse conductors and a brain center, where all those irritations that come from the environment and the human body are analyzed. Various analyzers are closely interconnected, in connection with this, analysis and synthesis take place in the cortex, development of responsible reactions that regulate all types of human activity. It is known that in the cerebral cortex there is a core and scattered elements occupying a certain area. The cerebral cortex is a collection of cores of various analyzers, between which are scattered elements of different adjacent analyzers.

So, in accordance with the cytoarchitectonic maps of the cerebral hemispheres in humans, it is possible to determine the cortical ends of various analyzers (nuclei) relative to the convolutions and lobes of the hemispheres (Fig. 141).

Fig. 141.

Cytoarchitectonic fields of the cerebral cortex



(according to Broadman, 1925):

A is the lateral surface; B - medial surface; numbers - cortical fields

In the cortex of the postcentral gyrus and the superior parietal lobe there are nerve cells that form the core of the cortical analyzer of general sensitivity (temperature, pain, sensory) and proprioceptive. Sensitive pathways leading from the cerebral cortex have a cross at the level of the spinal cord and medulla oblongata. As a result, the postcentral gyrus of each hemisphere is associated with the opposite half of the field. In the postcentral gyrus, all receptor fields of different parts of the body have their own projection onto the region of the cortical end of the analyzer of general sensitivity. The core of the motor analyzer is located mainly in the motor region of the cortex and is localized in the precentral gyrus, which lies in front of the central (Roland) groove. It is known that in the upper parts of the precentral gyrus and in the paracentral lobe there is a nucleus, the impulses from which go to the muscles of the lower parts of the trunk and limbs.

In the lower part of the precentral gyrus is the core of the motor analyzer, which regulates the activity of the facial muscles.

In the posterior sections of the middle frontal gyrus there is the analyzer core, which provides the function of the conjugate rotation of the head and eyes in the opposite direction.

In the region of the inferior parietal lobe, there is the core of the motor analyzer, the function of which is the implementation of all targeted complex movements.

In the cortex of the superior parietal lobule is the core of the skin analyzer, one of the types of sensitivity that has the function of knowing the subject by touch.
The cortical ends of this analyzer are located in the right and left hemispheres. Damage to these areas of the cortex leads to loss of recognition of objects when feeling.

The core of the visual analyzer is located on the medial surface of the occipital lobe. Receptors of the lateral half of the retina of the left eye and the medial half of the retina of the right eye are projected respectively in the cortex of the occipital lobe of the left hemisphere. The defeat of the visual analyzer leads to complete loss of vision or visual memory with impaired ability to navigate in an unfamiliar space.

The core of the auditory analyzer is located in the upper edge of the temporal lobe. The pathways from the receptors of both the left and right sides go to it. In this case, a unilateral damage to the nucleus does not cause a complete loss of the ability to perceive sounds. In case of bilateral lesion, “cortical deafness” is observed. On the lower surface of the temporal lobe of the cerebral hemispheres, in the area of ​​the hook (end of the parahippocampal gyrus) is the core of the odor analyzer.

Senses of smell and taste are closely interconnected, which is explained by the close location of their analyzers. The nuclei of the hemisphere analyzers are associated with receptors on both the left and right sides of the body.

In the back section of the middle frontal gyrus is the core of the motor writing analyzer. Damage to this area leads to the loss of precise movements when writing letters and numbers.

The core of the motor analyzer of articulation of speech is located in the rear sections of the lower frontal gyrus (Brock's center). The defeat of this zone leads to a loss of motor ability of the muscles that are involved in speech formation. In the lower frontal gyrus is the core of the language analyzer, which is associated with singing; its damage causes the loss of memorization of musical phrases. In the upper part of the temporal gyrus lies the core of the cortical analyzer, the defeat of which leads to musical deafness.

The projection zones of the cortex occupy a small portion of the surface of the cortex of the cerebral hemispheres of the human brain in comparison with associative zones, which have no close connection with either the sensory organs or muscles, they communicate between different regions of the cortex; integrate, unite all impulses entering the cortex into integral acts of learning (reading, language, writing), logical thinking, memory and provide the possibility of a targeted reaction of behavior.

In case of violations of associative zones, agnosia appears - the inability to cognize and apraxia - the inability to perform learned movements. For example, if the outer surface of the occipital lobe - the associative zone of vision - is damaged, visual agnosia is observed, the patient is not able to read the text, to recognize a familiar person. In case of violation of the associative zones of speech of the cerebral cortex, aphasia is possible - loss of speech. Aphasia can be sensory and motor.

Sensory aphasia (Wernicke aphasia) is characterized by a violation of the understanding of oral speech while maintaining the possibility of repeating what was said by another person; observed in lesions of the pathways between the back and middle of the superior temporal gyrus (Wernicke area) and other areas of the cerebral cortex. Motor aphasia occurs when the posterior third of the lower frontal gyrus on the left (Brock's center) is affected: the patient understands the speaker’s speech, but cannot speak.
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Physiology of the cerebral cortex of the cerebral hemisphere

  1. BRAIN ARCHITECTONICS OF THE BRAIN HEMISPHERE
    The doctrine of the structural features of the structure of the cortex is called architectonics. The cells of the cerebral cortex are less specialized. than neurons of other parts of the brain; nevertheless, certain groups of them are anatomically and physiologically closely related to certain specialized parts of the brain. The microscopic structure of the cerebral cortex is not the same in different departments. These are morphological
  2. BRAIN HEMISPHERE
    The cerebrum (cerebrum) is the most massive part of the brain and occupies most of the cavity of the cerebral cranium. The longitudinal fissure of the cerebrum (fissura top gitudinahs cerebn) divides the cerebrum into two hemispheres (hemisphenum cerebn dextrum et sinistrum). The surface of the hemispheres is covered with a layer of gray matter - the cerebral cortex - the latest in development and most
  3. BRAIN HEMISPHERE
    The cerebral hemispheres are the most massive part of the brain. They cover the cerebellum and brain stem. The cerebral hemispheres make up approximately 78% of the total brain mass. In the process of ontogenetic development of the body, the cerebral hemispheres develop from the final cerebral bladder of the neural tube, therefore this part of the brain is also called the final
  4. Cerebral hemispheres
    The cerebral hemispheres are the most massive part of the brain. They cover the cerebellum and brain stem. The cerebral hemispheres make up approximately 78% of the total brain mass. In the process of ontogenetic development of the body, the cerebral hemispheres develop from the final cerebral bladder of the neural tube, therefore this part of the brain is also called the final
  5. Tumors of the cerebral hemispheres
    With tumors of the cerebral hemispheres, a variety of symptoms are noted, due to the specifics of the areas in which they are located. Before proceeding to the description of individual tumors of the cerebral hemispheres, let us dwell on the syndromes of damage to its lobes. Tumors of the frontal lobes. The main symptoms are mental disorders, epileptic seizures, aphasia (with left-sided
  6. Method of transcranial magnetic stimulation of the motor zones of the cerebral cortex
    Magnetic stimulation of the brain - a non-invasive method for assessing the functional state of the pyramidal path - is carried out using a magnetic stimulator with a magnetic field intensity of 30–40 to 70–80% of the maximum possible for this device. The magnetic coil is placed in the area of ​​the projection of the motor zones of the cortex and spinous processes of the VI – VII cervical and 1–11 lumbar vertebrae. registration
  7. The concept of functional asymmetry of the cerebral hemispheres
    Interhemispheric asymmetry (dr. Greek? - “without” and ????????? - “proportionality”) is one of the fundamental laws of the organization of the brain of not only humans, but also animals. It manifests itself not only in brain morphology, but also in interhemispheric asymmetry and mental processes. As part of the research, the focus is on the relationship of interhemispheric asymmetry with mental
  8. Hemisphere Syndromes
    Frontal lobe: when it is affected, general convulsive or reverse seizures occur (starting with a convulsive turn of the eyes and head to the opposite side of the affected hemisphere), paresis or paralysis of the gaze, grasping reflexes, symptoms of oral automatism, motor aphasia, motor apraxia, frontal psyche - sloppy, untidiness, a tendency to flat jokes and witticisms (moria), euphoria,
  9. Cerebral hemispheres
    In the late 1960s, University of California professor Roger Sperry, subsequently a Nobel Prize laureate, announced the results of his work on the study of the most evolutionarily developed part of the human brain - the cerebral cortex. Discovered by Sperry indicated that the two halves, or hemispheres, of the brain are in relation to the "division of labor", dividing among themselves
  10. Cerebral hemisphere model
    In parallel with the work of Tony Buchan, neurophysiology in the 60s of the last century was replenished with new discoveries that influenced the development of thinking mapping. Later awarded the Nobel Prize Roger Sperry found that the hemispheres of the human brain perform different functions. Based on the figure, it is easy to conclude that the left hemisphere is responsible for maintaining classical records
  11. Functional asymmetry of the cerebral hemispheres
    The discovery of interhemispheric functional asymmetry of the brain was the same revolution in physiology and psychology as the discovery of nuclear fission in physics. It began with a bold operation by American researcher R. Sperry. During the operation, now the Nobel laureate R. Sperry, to relieve the patient from suffering, to prevent the spread of convulsive activity throughout the brain in
  12. Cerebral cortex
    The cerebral hemispheres are separated by a deep groove that reaches the corpus callosum - a massive layer of fibers connecting both hemispheres. Each hemisphere has three poles: frontal, occipital and temporal. Macroscopically, in each hemisphere, lobes are distinguished: frontal, parietal, occipital, temporal and islet. The surface of the large brain is formed by a cortex consisting of nerve cells. Under the bark
  13. Characteristic symptoms of damage to certain parts of the cerebral cortex
    Symptoms of damage to individual sections of the cerebral cortex depend on the location of the pathological process. Not symptoms of damage may be noted, but symptoms of irritation of individual cortical areas. Frontal lobe. Damage to the region of the anterior central gyrus leads to the development of monoplegia, hemiplegia, and insufficiency of the facial and sublingual nerves of the central type. If
  14. Puncture of the ventricles of the brain with an open large fontanel
    INDICATIONS 5. In case of obvious internal hydrocephalus, ventricular puncture can be performed according to vital indications for relief of the hypertensive hydrocephalic crisis. 6. If it is impossible to conduct a sonography of the skull, a puncture is performed to measure pressure in the ventricular system and to determine the degree of connectivity between the ventricles. 7. For ventriculography. 8. Study of the composition
  15. The role of IM. Sechenova and I.P. Pavlova in creating modern physiology of the brain
    THEM. Sechenov (Fig. 54) was a broad-range physiologist. His research concerned many aspects of physiological science. However, he showed particular interest in the physiology of muscles and nerves. At the end of St. Petersburg University I.M. Sechenov finally chooses physiology as his specialty and goes to improve abroad. There he works with famous physiologists of that time - I. Müller,
  16. Zdenek M. Development of the right hemisphere, 2012

  17. Adrenal cortex insufficiency
    1. Define adrenal insufficiency. Adrenal cortex insufficiency, or Addison's disease, is characterized by reduced production of glucocorticoids and mineralocorticoids by the adrenal glands. The cause of the disease is a pathological process that directly affects the adrenal glands (primary hypoadrenocorticism) or the formation and secretion
  18. Cerebellum. Hemisphere structure
    The cerebellum (lat. Cerebellum - literally. "Small brain") - part of the hindbrain of vertebrates, which plays an important role in the coordination of movements. The cerebellum is located above the medulla oblongata and the bridge, just like the large brain, is covered with membranes. The connection of the cerebellum with other structures of the brain is through the legs of the cerebellum. The mammalian cerebellum, like the brain, consists of the right and left
  19. SYMPTOMOCOMPLEX OF DEFEAT OF INDIVIDUAL BAR ZONES
    Frontal lobe. The defeat of the precentral gyrus. Irritation of the precentral gyrus by the pathological process is accompanied by attacks of Jacksonian epilepsy, expressed in clonic or tonic-clonic seizures of limited muscle groups corresponding to the irritated part of the cortex: seizures occur on the side opposite to the pathological focus in the brain and are not accompanied
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