Motor functions of the cerebral cortex. Physiology of the cerebral cortex

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 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 reflexes brain stem.

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 nuclei (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 of the body’s emotional states; 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 of complex forms of 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 depends 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 of the 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).

Modern scientists know for certain that thanks to the functioning of the brain, such abilities as awareness of signals received from the external environment, mental activity, and memorization of thoughts are possible.

The ability of an individual to realize his own relationships with other people is directly related to the process of excitation of neural networks. Moreover, we are talking specifically about those neural networks that are located in the cortex. It represents the structural basis of consciousness and intelligence.

In this article we will look at how the cerebral cortex is structured; the areas of the cerebral cortex will be described in detail.

Neocortex

The cortex contains about fourteen billion neurons. It is thanks to them that the main zones function. The vast majority of neurons, up to ninety percent, form the neocortex. It is part of the somatic NS and its highest integrative department. The most important functions of the cerebral cortex are the perception, processing, and interpretation of information that a person receives with the help of various senses.

In addition, the neocortex controls the complex movements of the human body's muscle system. It contains centers that take part in the process of speech, memory storage, and abstract thinking. Most of the processes that occur in it form the neurophysical basis of human consciousness.

What other parts does the cerebral cortex consist of? We will consider the areas of the cerebral cortex below.

Paleocortex

It is another large and important section of the cortex. Compared to the neocortex, the paleocortex has a simpler structure. The processes that take place here are rarely reflected in consciousness. The higher vegetative centers are localized in this section of the cortex.

Connection of the cortex with other parts of the brain

It is important to consider the connection that exists between the underlying parts of the brain and the cerebral cortex, for example, with the thalamus, pons, medial pons, and basal ganglia. This connection is carried out using large bundles of fibers that form the internal capsule. Bundles of fibers are represented by wide layers, which are composed of white matter. They contain a huge number of nerve fibers. Some of these fibers provide transmission of nerve signals to the cortex. The rest of the bundles transmit nerve impulses to the nerve centers located below.

How is the cerebral cortex structured? The areas of the cerebral cortex will be presented below.

Structure of the cortex

The largest part of the brain is its cortex. Moreover, cortical zones are only one type of parts distinguished in the cortex. In addition, the cortex is divided into two hemispheres - right and left. The hemispheres are connected to each other by bundles of white matter that form the corpus callosum. Its function is to ensure coordination of the activities of both hemispheres.

Classification of cerebral cortex zones by their location

Despite the fact that the cortex has a huge number of folds, in general the location of its individual convolutions and grooves is constant. The main ones are a guideline for identifying areas of the cortex. Such zones (lobes) include occipital, temporal, frontal, parietal. Although they are classified by location, each has its own specific functions.

Auditory cortex

For example, the temporal zone is the center in which the cortical section of the hearing analyzer is located. If damage to this part of the cortex occurs, deafness may occur. In addition, Wernicke's speech center is located in the auditory zone. If it is damaged, then the person loses the ability to perceive oral speech. A person perceives it as simple noise. Also in the temporal lobe there are neural centers that belong to the vestibular apparatus. If they are damaged, the sense of balance is disrupted.

Speech areas of the cerebral cortex

Speech areas are concentrated in the frontal lobe of the cortex. The speech motor center is also located here. If damage occurs in the right hemisphere, then the person loses the ability to change the timbre and intonation of his own speech, which becomes monotonous. If damage to the speech center occurs in the left hemisphere, then articulation and the ability to articulate speech and singing disappear. What else does the cerebral cortex consist of? The areas of the cerebral cortex have different functions.

Visual zones

In the occipital lobe there is a visual zone, in which there is a center that responds to our vision as such. The perception of the world around us occurs precisely with this part of the brain, and not with the eyes. It is the occipital cortex that is responsible for vision, and damage to it can lead to partial or complete loss of vision. The visual area of the cerebral cortex is examined. What's next?

The parietal lobe also has its own specific functions. It is this zone that is responsible for the ability to analyze information that relates to tactile, temperature and pain sensitivity. If damage occurs to the parietal region, the brain's reflexes are disrupted. A person cannot recognize objects by touch.

Motor zone

Let's talk about the motor zone separately. It should be noted that this zone of the cortex does not correlate in any way with the lobes discussed above. It is part of the cortex containing direct connections to motor neurons in the spinal cord. This name is given to neurons that directly control the activity of the muscles of the body.

The main motor area of the cerebral cortex is located in a gyrus called the precentral gyrus. This gyrus is a mirror image of the sensory area in many aspects. Between them there is contralateral innervation. To put it another way, the innervation is directed to the muscles that are located on the other side of the body. The exception is the facial area, which is characterized by bilateral control of the muscles located on the jaw and lower part of the face.

Slightly below the main motor zone is an additional zone. Scientists believe that it has independent functions that are associated with the process of outputting motor impulses. The supplementary motor area has also been studied by specialists. Experiments carried out on animals show that stimulation of this zone provokes the occurrence of motor reactions. The peculiarity is that such reactions occur even if the main motor area has been isolated or completely destroyed. It is also involved in motor planning and speech motivation in the dominant hemisphere. Scientists believe that if the accessory motor is damaged, dynamic aphasia can occur. Brain reflexes suffer.

Classification according to the structure and functions of the cerebral cortex

Physiological experiments and clinical trials, which were carried out at the end of the nineteenth century, made it possible to establish the boundaries between the areas to which different receptor surfaces are projected. Among them are sensory organs that are directed to the outside world (skin sensitivity, hearing, vision), receptors embedded directly in the organs of movement (motor or kinetic analyzers).

Cortical areas in which various analyzers are located can be classified according to structure and function. So, there are three of them. These include: primary, secondary, tertiary zones of the cerebral cortex. The development of the embryo involves the formation of only primary zones, characterized by simple cytoarchitecture. Next comes the development of secondary ones, tertiary ones develop last. Tertiary zones are characterized by the most complex structure. Let's look at each of them in a little more detail.

Central fields

Behind long years Clinical studies scientists have managed to accumulate significant experience. Observations made it possible to establish, for example, that damage to various fields, within the cortical sections of different analyzers, can have a far different effect on the overall clinical picture. If we consider all these fields, then among them we can single out one that occupies a central position in the nuclear zone. This field is called central or primary. It is located simultaneously in the visual zone, in the kinesthetic zone, and in the auditory zone. Damage to the primary field entails very serious consequences. A person cannot perceive and carry out the most subtle differentiation of stimuli that affect the corresponding analyzers. How else are areas of the cerebral cortex classified?

Primary zones

In the primary zones there is a complex of neurons that is most predisposed to providing bilateral connections between the cortical and subcortical zones. It is this complex that connects the cerebral cortex with various sensory organs in the most direct and shortest way. In this regard, these zones have the ability to identify stimuli in a very detailed manner.

An important common feature of the functional and structural organization of the primary areas is that they all have a clear somatic projection. This means that individual peripheral points, for example, skin surfaces, retina, skeletal muscles, cochleae of the inner ear, have their own projection into strictly limited, corresponding points, which are located in the primary zones of the cortex of the corresponding analyzers. In this regard, they were given the name projection zones of the cerebral cortex.

Secondary zones

In another way, these zones are called peripheral. This name was not given to them by chance. They are located in the peripheral parts of the cortex. Secondary zones differ from the central (primary) zones in their neural organization, physiological manifestations and architectural features.

Let's try to figure out what effects occur if the secondary zones are affected by an electrical stimulus or if they are damaged. The effects that arise mainly concern the most complex types of processes in the psyche. In the event that damage occurs to the secondary zones, the elementary sensations remain relatively intact. Basically, there are disturbances in the ability to correctly reflect mutual relationships and entire complexes of elements that make up the various objects that we perceive. For example, if the secondary zones of the visual and auditory cortex are damaged, then the emergence of auditory and visual hallucinations can be observed, which unfold in a certain temporal and spatial sequence.

Secondary areas are of significant importance in the implementation of mutual connections between stimuli, which are allocated with the help of primary areas of the cortex. In addition, they play a significant role in the integration of functions that are carried out by the nuclear fields of different analyzers as a result of combining into complex complexes of receptions.

Thus, secondary zones are of particular importance for the implementation mental processes in more complex forms that require coordination and are associated with a detailed analysis of the relationships between objective stimuli. During this process, specific connections are established, which are called associative. Afferent impulses entering the cortex from receptors of various external sensory organs reach secondary fields through many additional switches in the association nucleus of the thalamus, which is also called the thalamus optic. Afferent impulses going to the primary zones, in contrast to impulses going to the secondary zones, reach them via a shorter route. It is implemented through a relay core in the visual thalamus.

We figured out what the cerebral cortex is responsible for.

What is the thalamus?

Fibers from the thalamic nuclei reach each lobe of the cerebral hemispheres. The thalamus is a visual thalamus located in the central part of the forebrain; it consists of a large number of nuclei, each of which transmits impulses to certain areas of the cortex.

All signals that enter the cortex (with the exception of olfactory signals) pass through the relay and integrative nuclei of the visual thalamus. From the nuclei of the thalamus, fibers are directed to sensory areas. The taste and somatosensory zones are located in the parietal lobe, the auditory sensory zone is in the temporal lobe, and the visual zone is in the occipital lobe.

Impulses to them come, respectively, from the ventro-basal complexes, medial and lateral nuclei. Motor areas are connected to the ventral and ventrolateral nuclei of the thalamus.

EEG desynchronization

What happens if a person who is in a state of complete rest is exposed to a very strong stimulus? Naturally, a person will fully concentrate on this stimulus. The transition of mental activity, which occurs from a state of rest to a state of activity, is reflected on the EEG by the beta rhythm, which replaces the alpha rhythm. Fluctuations become more frequent. This transition is called EEG desynchronization; it appears as a result of sensory stimulation entering the cortex from nonspecific nuclei located in the thalamus.

Activating reticular system

The diffuse nervous system consists of nonspecific nuclei. This system is located in the medial sections of the thalamus. It is the anterior part of the activating reticular system, which regulates the excitability of the cortex. A variety of sensory signals can activate this system. Sensory signals can be both visual and olfactory, somatosensory, vestibular, auditory. The activating reticular system is a channel that transmits signal data to the superficial layer of the cortex through nonspecific nuclei located in the thalamus. Excitation of the ARS is necessary for a person to be able to maintain a state of wakefulness. If disturbances occur in this system, comatose sleep-like states may occur.

Tertiary zones

There are functional relationships between the analyzers of the cerebral cortex, which have an even more complex structure than that described above. During the growth process, the fields of the analyzers overlap each other. Such overlap zones that form at the ends of the analyzers are called tertiary zones. They are the most complex types combining the activities of the auditory, visual, skin-kinesthetic analyzers. Tertiary zones are located outside the boundaries of the analyzers’ own zones. In this regard, their damage does not have a pronounced effect.

Tertiary zones are special cortical areas in which scattered elements of different analyzers are collected. They occupy a very vast territory, which is divided into regions.

The upper parietal region integrates the movements of the whole body with the visual analyzer and forms a body diagram. The inferior parietal region combines generalized forms of signaling that are associated with differentiated object and speech actions.

No less important is the temporo-parietal-occipital region. She is responsible for the complex integration of auditory and visual analyzers with oral and written speech.

It is worth noting that, compared to the first two zones, the tertiary zones are characterized by the most complex interaction chains.

If we rely on all the material presented above, we can conclude that the primary, secondary, and tertiary zones of the human cortex are highly specialized. Separately, it is worth emphasizing the fact that all three cortical zones that we considered, in a normally functioning brain, together with systems of connections and subcortical formations, function as a single differentiated whole.

We examined in detail the zones and sections of the cerebral cortex.

The cerebral cortex is senior department of the central nervous system, which appears later in the process of phylogenetic development and is formed during individual (ontogenetic) development later than other parts of the brain. The cortex is a layer of gray matter 2-3 mm thick, containing on average about 14 billion (from 10 to 18 billion) nerve cells, nerve fibers and interstitial tissue (neuroglia). In its cross section, based on the location of neurons and their connections, 6 horizontal layers are distinguished. Thanks to numerous convolutions and grooves, the surface area of the cortex reaches 0.2 m2. Directly below the cortex is white matter, consisting of nerve fibers that transmit excitation to and from the cortex, as well as from one area of the cortex to another.
Cortical neurons and their connections. Despite the huge number of neurons in the cortex, very few of their varieties are known. Their main types are pyramidal and stellate neurons.
...
In the afferent function of the cortex and in the processes of switching excitation to neighboring neurons, the main role belongs to stellate neurons. They make up more than half of all cortical cells in humans. These cells have short branching axons that do not extend beyond the gray matter of the cortex, and short branching dendrites. Stellate neurons are involved in the processes of perception of irritation and combining the activities of various pyramidal neurons.

Pyramidal neurons carry out the efferent function of the cortex and intracortical processes of interaction between neurons remote from each other. They are divided into large pyramids, from which projection, or efferent, paths to subcortical formations begin, and small pyramids, forming associative paths to other parts of the cortex. The largest pyramidal cells - the giant pyramids of Betz - are located in the anterior central gyrus, in the so-called motor zone of the cortex. Feature large pyramids - their vertical orientation in the thickness of the crust. From the cell body, the thickest (apical) dendrite is directed vertically upward to the surface of the cortex, through which various afferent influences from other neurons enter the cell, and an efferent process, the axon, extends vertically downward.

The large number of contacts (for example, on the dendrites of a large pyramid alone there are from 2 to 5 thousand) provides the possibility of broad regulation of the activity of pyramidal cells by many other neurons. This makes it possible to coordinate the responses of the cortex (primarily its motor function) with various influences from the external environment and the internal environment of the body.

The cerebral cortex is characterized by an abundance of interneuron connections. As the human brain develops after birth, the number of intercentral connections increases, especially intensely until the age of 18.

...
Primary, secondary and tertiary cortical fields. The structural features and functional significance of individual areas of the cortex make it possible to distinguish individual cortical fields.

There are three main groups of fields in the cortex: primary, secondary and tertiary fields.

Primary fields are associated with sensory organs and organs of movement on the periphery; they mature earlier than others in ontogenesis and have the largest cells. These are the so-called nuclear zones of the analyzers, according to I. P. Pavlov (for example, the field of pain, temperature, tactile and muscle-articular sensitivity in the posterior central gyrus of the cortex, the visual field in the occipital region, the auditory field in the temporal region and the motor field in the anterior central gyrus of the cortex) (Fig. 54). These fields analyze individual stimuli entering the cortex from the corresponding receptors. When primary fields are destroyed, so-called cortical blindness, cortical deafness, etc. occur. Nearby are secondary fields, or peripheral zones of analyzers, which are connected to individual organs only through primary fields. They serve to summarize and further process incoming information. Individual sensations are synthesized in them into complexes that determine the processes of perception. When secondary fields are damaged, the ability to see objects and hear sounds is retained, but the person does not recognize them and does not remember their meaning. Both humans and animals have primary and secondary fields.

The furthest from direct connections with the periphery are the tertiary fields, or the overlap zones of the analyzers. Only humans have these fields. They occupy almost half of the cortex and have extensive connections with other parts of the cortex and with nonspecific brain systems. These fields are dominated by the smallest and most diverse cells. The main cellular element here are stellate neurons. Tertiary fields are located in the posterior half of the cortex - at the boundaries of the parietal, temporal and occipital regions and in the anterior half - in the anterior parts of the frontal regions. In these zones it ends greatest number nerve fibers connecting the left and right hemispheres, therefore their role is especially great in organizing the coordinated work of both hemispheres. Tertiary fields mature in humans later than other cortical fields; they carry out the most complex functions of the cortex. Processes of higher analysis and synthesis take place here. In tertiary fields, based on the synthesis of all afferent stimulation and taking into account traces of previous stimulation, goals and objectives of behavior are developed. According to them, motor activity is programmed. The development of tertiary fields in humans is associated with the function of speech. Thinking (inner speech) is possible only with the joint activity of analyzers, the integration of information from which occurs in tertiary fields.

With congenital underdevelopment of the tertiary fields, a person is not able to master speech (pronounces only meaningless sounds) and even the simplest motor skills (cannot dress, use tools, etc.).

Perceiving and evaluating all signals from the internal and external environment, the cerebral cortex carries out the highest regulation of all motor and emotional-vegetative reactions.

Functions of the cerebral cortex. The cerebral cortex performs the most complex functions of organizing the adaptive behavior of the organism in the external environment. This is primarily a function of higher analysis and synthesis of all afferent stimulation.

Afferent signals enter the cortex through different channels, into different nuclear zones of the analyzers (primary fields), and then are synthesized in the secondary and tertiary fields, thanks to the activity of which a holistic perception of the external world is created. This synthesis underlies the complex mental processes of perception, representation, and thinking. The cerebral cortex is an organ closely associated with the emergence of consciousness in humans and the regulation of their social behavior. An important aspect of the activity of the cerebral cortex is the closure function - the formation of new reflexes and their systems (conditioned reflexes, dynamic stereotypes - see Chapter XV).

Due to the unusually long duration of preservation of traces of previous irritations (memories) in the cortex, a huge amount of information accumulates in it. This goes a long way to maintaining a personalized experience that is used as needed.
...
It has been experimentally shown that in the highest representatives of the animal world, after complete surgical removal cortex, higher nervous activity deteriorates sharply. They lose the ability to subtly adapt to the external environment and exist independently in it.

The cerebral cortex is the youngest formation of the central nervous system. The activity of the cerebral cortex is based on the principle of a conditioned reflex, which is why it is called conditioned reflex. It provides rapid communication with the external environment and adaptation of the body to changing environmental conditions.

Deep grooves divide each cerebral hemisphere into frontal, temporal, parietal, occipital lobes and insula. The insula is located deep in the Sylvian fissure and is covered from above by parts of the frontal and parietal lobes of the brain.

The cerebral cortex is divided into ancient ( archiocortex), old (paleocortex) and new (neocortex). The ancient cortex, along with other functions, is related to smell and the interaction of brain systems. The old cortex includes the cingulate gyrus and hippocampus. In the neocortex, the greatest development of size and differentiation of functions is observed in humans. The thickness of the new bark is 3-4 mm. The total area of the adult human cortex is 1700-2000 cm 2, and the number of neurons - 14 billion (if they are arranged in a row, a chain of 1000 km is formed) - is gradually depleted and by old age it is 10 billion (more than 700 km). The cortex contains pyramidal, stellate and fusiform neurons.

Pyramidal neurons have different sizes, their dendrites bear a large number of spines: the axon of a pyramidal neuron goes through the white matter to other areas of the cortex or structures of the central nervous system.

Stellate neurons have short, well-branched dendrites and a short axon that provides connections between neurons within the cerebral cortex itself.

Fusiform neurons provide vertical or horizontal connections between neurons of different layers of the cortex.

The structure of the cerebral cortex

The cortex contains a large number of glial cells that perform supporting, metabolic, secretory, and trophic functions.

The outer surface of the cortex is divided into four lobes: frontal, parietal, occipital and temporal. Each lobe has its own projection and associative areas.

The cerebral cortex has a six-layer structure (Fig. 1-1):

molecular layer(1) light, consists of nerve fibers and has a small number of nerve cells;
outer granular layer(2) consists of stellate cells that determine the duration of circulation of excitation in the cerebral cortex, i.e. related to memory;
pyramid mark layer(3) is formed from small pyramidal cells and, together with layer 2, provides cortico-cortical connections of various convolutions of the brain;
inner granular layer(4) consists of stellate cells, specific thalamocortical pathways end here, i.e. pathways starting from analyzer receptors.
inner pyramidal layer(5) consists of giant pyramidal cells, which are output neurons, their axons go to the brain stem and spinal cord;
layer of polymorphic cells(6) consists of heterogeneous triangular and spindle-shaped cells that form the corticothalamic tract.

I - afferent pathways from the thalamus: STA - specific thalamic afferents; NTA - nonspecific thalamic afferents; EMV - efferent motor fibers. The numbers indicate the layers of the cortex; II - pyramidal neuron and distribution of endings on it: A - nonspecific afferent fibers from the reticular formation and; B — return collaterals from axons of pyramidal neurons; B - commissural fibers from mirror cells of the opposite hemisphere; G - specific afferent fibers from the sensory nuclei of the thalamus

Rice. 1-1. Connections of the cerebral cortex.

The cellular composition of the cortex in terms of diversity of morphology, functions, and forms of communication has no equal in other parts of the central nervous system. The neuronal composition and distribution among layers in different areas of the cortex are different. This made it possible to identify 53 cytoarchitectonic fields in the human brain. The division of the cerebral cortex into cytoarchitectonic fields is more clearly formed as its function improves in phylogenesis.

The functional unit of the cortex is a vertical column with a diameter of about 500 µm. Column - zone of distribution of branches of one ascending (afferent) thalamocortical fiber. Each column contains up to 1000 neural ensembles. Excitation of one column inhibits neighboring speakers.

The ascending pathway passes through all cortical layers (specific pathway). The nonspecific pathway also passes through all cortical layers. The white matter of the hemispheres is located between the cortex and the basal ganglia. It consists of a large number of fibers running in different directions. These are the pathways of the telencephalon. There are three types of paths.

projection- connects the cortex with the diencephalon and other parts of the central nervous system. These are the ascending and descending paths;
commissural - its fibers are part of the cerebral commissures, which connect the corresponding areas of the left and right hemispheres. They are part of the corpus callosum;
associative - connects parts of the cortex of the same hemisphere.

Cortical areas of the cerebral hemispheres

Based on the characteristics of the cellular composition, the surface of the cortex is divided into structural units the following order: zones, regions, subregions, fields.

The areas of the cerebral cortex are divided into primary, secondary and tertiary projection zones. They contain specialized nerve cells that receive impulses from certain receptors (auditory, visual, etc.). Secondary zones are the peripheral sections of the analyzer nuclei. Tertiary zones receive processed information from the primary and secondary zones of the cerebral cortex and play an important role in the regulation of conditioned reflexes.

In the gray matter of the cerebral cortex, sensory, motor and associative zones are distinguished:

sensory areas of the cerebral cortex - areas of the cortex in which the central sections of the analyzers are located:
visual zone - occipital lobe of the cerebral cortex;
auditory zone - temporal lobe of the cerebral cortex;
zone of taste sensations - parietal lobe of the cerebral cortex;
the zone of olfactory sensations is the hippocampus and the temporal lobe of the cerebral cortex.

Somatosensory area located in the posterior central gyrus, nerve impulses from proprioceptors of muscles, tendons, joints and impulses from temperature, tactile and other skin receptors come here;

motor areas of the cerebral cortex - areas of the cortex, upon stimulation of which motor reactions appear. Located in the anterior central gyrus. When it is damaged, significant movement disturbances are observed. The paths along which impulses travel from the cerebral hemispheres to the muscles form a crossover, therefore, when the motor zone is irritated right side the cortex causes contraction of the muscles on the left side of the body;
association zones - parts of the cortex located next to the sensory areas. Nerve impulses entering sensory zones lead to excitation of associative zones. Their peculiarity is that excitation can occur when impulses arrive from various receptors. Destruction of associative zones leads to serious impairments in learning and memory.

The speech function is associated with sensory and motor areas. Motor speech center (Broca's center) located in the lower part of the left frontal lobe, when it is destroyed, speech articulation is disrupted; in this case, the patient understands speech, but cannot speak himself.

Auditory speech center (Wernicke's center) located in the left temporal lobe of the cerebral cortex, when it is destroyed, verbal deafness occurs: the patient can speak, express his thoughts orally, but does not understand the speech of others; hearing is preserved, but the patient does not recognize words, written speech is impaired.

Speech functions associated with written speech - reading, writing - are regulated visual center of speech, located on the border of the parietal, temporal and occipital lobes of the cerebral cortex. Its defeat results in the inability to read and write.

In the temporal lobe there is a center responsible for memorization layer. A patient with damage to this area does not remember the names of objects; he needs to be prompted the right words. Having forgotten the name of an object, the patient remembers its purpose and properties, so he describes their qualities for a long time, tells what is being done with this object, but cannot name it. For example, instead of the word “tie,” the patient says: “this is something that is put on the neck and tied with a special knot so that it is beautiful when they go to visit.”

Functions of the frontal lobe:

control of innate behavioral reactions using accumulated experience;
coordination of external and internal motivations of behavior;
development of behavior strategy and action program;
mental characteristics of the individual.

Composition of the cerebral cortex

The cerebral cortex is the highest structure of the central nervous system and consists of nerve cells, their processes and neuroglia. The cortex contains stellate, fusiform and pyramidal neurons. Due to the presence of folds, the bark has a large surface area. There is an ancient cortex (archicortex) and a new cortex (neocortex). The bark consists of six layers (Fig. 2).

Rice. 2. Cerebral cortex

The upper molecular layer is formed mainly by the dendrites of the pyramidal cells of the underlying layers and the axons of the nonspecific nuclei of the thalamus. Afferent fibers coming from the associative and nonspecific nuclei of the thalamus form synapses on these dendrites.

The outer granular layer is formed by small stellate cells and partially by small pyramidal cells. The fibers of the cells of this layer are located mainly along the surface of the cortex, forming corticocortical connections.

A layer of small pyramidal cells.

Inner granular layer formed by stellate cells. It ends with afferent thalamocortical fibers starting from the receptors of the analyzers.

The inner pyramidal layer consists of large pyramidal cells involved in the regulation of complex forms of movement.

The layer multiforme consists of versiform cells that form the corticothalamic tracts.

According to their functional significance, cortical neurons are divided into sensory, receiving afferent impulses from the nuclei of the thalamus and receptors of sensory systems; motor, sending impulses to the subcortical nuclei, intermediate, mesencephalon, medulla oblongata, cerebellum, reticular formation and spinal cord; And intermediate, which communicate between the neurons of the cerebral cortex. The neurons of the cerebral cortex are in a constant state of excitation, which does not disappear during sleep.

In the cerebral cortex, sensory neurons receive impulses from all receptors of the body through the nuclei of the thalamus. And each organ has its own projection or cortical representation, located in certain areas of the cerebral hemispheres.

The cerebral cortex has four sensory and four motor areas.

Neurons of the motor cortex receive afferent impulses through the thalamus from muscle, joint and skin receptors. The main efferent connections of the motor cortex are carried out through the pyramidal and extrapyramidal pathways.

In animals, the frontal cortex is the most developed, and its neurons are involved in goal-directed behavior. If this lobe of the bark is removed, the animal becomes lethargic and drowsy. The area of auditory reception is localized in the temporal region, and nerve impulses from the receptors of the cochlea of the inner ear arrive here. The area of visual reception is located in the occipital lobes of the cerebral cortex.

The parietal region, an extranuclear zone, plays an important role in organizing complex forms of higher nervous activity. Here the scattered elements of the visual and skin analyzers are located, and inter-analyzer synthesis is carried out.

Next to the projection zones there are association zones that communicate between the sensory and motor zones. The associative cortex takes part in the convergence of various sensory excitations, allowing for complex processing of information about the external and internal environment.

glial cells; it is located in some parts of the deep brain structures; the cerebral cortex (as well as the cerebellum) is formed from this substance.

Each hemisphere is divided into five lobes, four of which (frontal, parietal, occipital and temporal) are adjacent to the corresponding bones of the cranial vault, and one (insular) is located in depth, in the fossa that separates the frontal and temporal lobes.

The cerebral cortex has a thickness of 1.5–4.5 mm, its area increases due to the presence of grooves; it is connected to other parts of the central nervous system, thanks to impulses carried out by neurons.

The hemispheres reach approximately 80% of the total mass of the brain. They regulate higher mental functions, while the brain stem regulates lower ones, which are associated with the activity of internal organs.

Three main areas are distinguished on the hemispheric surface:

convex superolateral, which is adjacent to the inner surface of the cranial vault;
lower, with the anterior and middle sections located on the inner surface of the cranial base and the posterior ones in the area of the tentorium of the cerebellum;
the medial one is located at the longitudinal fissure of the brain.

Features of the device and activity

The cerebral cortex is divided into 4 types:

ancient - occupies slightly more than 0.5% of the entire surface of the hemispheres;
old – 2.2%;
new – more than 95%;
the average is approximately 1.5%.

The phylogenetically ancient cerebral cortex, represented by groups of large neurons, is pushed aside by the new one to the base of the hemispheres, becoming a narrow strip. And the old one, consisting of three cellular layers, moves closer to the middle. The main area of the old cortex is the hippocampus, which is the central part of the limbic system. The middle (intermediate) cortex is a formation of a transitional type, since the transformation of old structures into new ones occurs gradually.

The cerebral cortex in humans, unlike that in mammals, is also responsible for the coordinated functioning of internal organs. This phenomenon, in which the role of the cortex in the implementation of all functional activities of the body increases, is called corticalization of functions.

One of the features of the cortex is its electrical activity, which occurs spontaneously. Nerve cells located in this section have a certain rhythmic activity, reflecting biochemical and biophysical processes. Activity has different amplitudes and frequencies (alpha, beta, delta, theta rhythms), which depends on the influence of numerous factors (meditation, sleep phases, stress, the presence of seizures, neoplasms).

Structure

The cerebral cortex is a multilayered formation: each layer has its own specific composition of neurocytes, a specific orientation, and location of processes.

The systematic position of neurons in the cortex is called “cytoarchitecture”; fibers located in a certain order are called “myeloarchitecture”.

The cerebral cortex consists of six cytoarchitectonic layers.

Surface molecular, in which there are not very many nerve cells. Their processes are located within itself, and they do not go beyond.
The outer granular is formed from pyramidal and stellate neurocytes. The processes emerge from this layer and go to subsequent ones.
Pyramidal consists of pyramidal cells. Their axons go down, where they end or form association fibers, and their dendrites go up into the second layer.
The internal granular cell is formed by stellate cells and small pyramidal cells. Dendrites go to the first layer, lateral processes branch within their layer. Axons extend into the upper layers or into the white matter.
The ganglion is formed by large pyramidal cells. The largest neurocytes of the cortex are located here. Dendrites are directed into the first layer or distributed in its own. Axons emerge from the cortex and begin to become fibers that connect various sections and structures of the central nervous system with each other.
Multiform - consists of different cells. Dendrites go to the molecular layer (some only to the fourth or fifth layers). Axons are directed to overlying layers or exit the cortex as association fibers.

The cerebral cortex is divided into areas - the so-called horizontal organization. There are 11 of them in total, and they include 52 fields, each of which has its own serial number.

Vertical organization

There is also a vertical division - into columns of neurons. In this case, small columns are combined into macrocolumns, which are called a functional module. At the heart of such systems are stellate cells - their axons, as well as their horizontal connections with the lateral axons of pyramidal neurocytes. All nerve cells of the vertical columns respond to the afferent impulse in the same way and together send an efferent signal. Excitation in the horizontal direction is due to the activity of transverse fibers that follow from one column to another.

He first discovered units that unite neurons of different layers vertically in 1943. Lorente de No - using histology. This was subsequently confirmed using electrophysiological methods in animals by V. Mountcastle.

Development of the cortex in intrauterine development begins early: already at 8 weeks the embryo develops a cortical plate. First, the lower layers are differentiated, and at 6 months the unborn child has all the fields that are present in an adult. The cytoarchitectonic features of the cortex are fully formed by the age of 7, but the bodies of neurocytes increase even up to 18. For the formation of the cortex, the coordinated movement and division of precursor cells from which neurons appear is necessary. It has been established that this process is influenced by a special gene.

Horizontal organization

It is customary to divide the areas of the cerebral cortex into:

associative;
sensory (sensitive);
motor.

Scientists, when studying localized areas and their functional characteristics, used a variety of methods: chemical or physical irritation, partial removal of brain areas, development of conditioned reflexes, registration of brain biocurrents.

Sensitive

These areas occupy approximately 20% of the cortex. Damage to such areas leads to impaired sensitivity (decreased vision, hearing, smell, etc.). The area of the zone directly depends on the number of nerve cells that perceive impulses from certain receptors: the more there are, the higher the sensitivity. Zones are distinguished:

somatosensory (responsible for cutaneous, proprioceptive, vegetative sensitivity) - it is located in the parietal lobe (postcentral gyrus);
visual, bilateral damage that leads to complete blindness, is located in the occipital lobe;
auditory (located in the temporal lobe);
gustatory, located in the parietal lobe (localization - postcentral gyrus);
olfactory, bilateral impairment of which leads to loss of smell (located in the hippocampal gyrus).

Violation auditory zone does not cause deafness, but other symptoms appear. For example, the inability to distinguish short sounds, the meaning of everyday noises (footsteps, pouring water, etc.) while maintaining the differences in sounds in pitch, duration, and timbre. Amusia may also occur, which is the inability to recognize, reproduce melodies, and also distinguish between them. Music can also be accompanied by unpleasant sensations.

Impulses traveling along afferent fibers on the left side of the body are perceived by the right hemisphere, and on the right side - by the left (damage to the left hemisphere will cause a violation of sensitivity on the right side and vice versa). This is due to the fact that each postcentral gyrus is connected to the opposite part of the body.

Motor

Motor areas, the irritation of which causes muscle movement, are located in the anterior central gyrus of the frontal lobe. Motor areas communicate with sensory areas.

The motor tracts in the medulla oblongata (and partly in the spinal cord) form a decussation with a transition to the opposite side. This leads to the fact that irritation that occurs in the left hemisphere enters the right half of the body, and vice versa. Therefore, damage to the cortex of one of the hemispheres leads to disruption of the motor function of muscles on the opposite side of the body.

Motor and sensory areas, which are located in the area central sulcus, are combined into one formation - the sensorimotor zone.

Neurology and neuropsychology have accumulated a lot of information about how damage to these areas leads not only to elementary movement disorders (paralysis, paresis, tremors), but also to disorders of voluntary movements and actions with objects - apraxia. When they appear, movements during writing may be disrupted, spatial representations may be disrupted, and uncontrolled patterned movements may appear.

Associative

These zones are responsible for linking incoming sensory information with that which was previously received and stored in memory. In addition, they allow you to compare information that comes from different receptors. The response to the signal is formed in the associative zone and transmitted to the motor zone. Thus, each associative area is responsible for the processes of memory, learning and thinking. Large association zones are located next to the corresponding functional sensory zones. For example, any associative visual function is controlled by the visual associative area, which is located next to the sensory visual area.

Establishing patterns of brain function, analyzing its local disorders and checking its activity is carried out by the science of neuropsychology, which is at the intersection of neurobiology, psychology, psychiatry and computer science.

Features of localization by fields

The cerebral cortex is plastic, which affects the transition of the functions of one section, if it is disrupted, to another. This is due to the fact that analyzers in the cortex have a core, where higher activity occurs, and a periphery, which is responsible for the processes of analysis and synthesis in a primitive form. Between the analyzer cores there are elements that belong to different analyzers. If damage concerns the nucleus, peripheral components begin to be responsible for its activity.

Thus, the localization of the functions that the cerebral cortex possesses is a relative concept, since there are no definite boundaries. However, cytoarchitectonics suggests the presence of 52 fields that communicate with each other via conductive pathways:

associative (this type of nerve fibers is responsible for the activity of the cortex in one hemisphere);
commissural (connecting symmetrical areas of both hemispheres);
projection (promote communication between the cortex and subcortical structures and other organs).

Table 1

		Relevant fields
Motor
Sensitive
Visual
Olfactory
Flavoring
Speech motor, which includes the centers:	Wernicke, which allows you to perceive spoken language
	Broca - responsible for the movement of the lingual muscles; defeat threatens complete loss of speech
	Perception of speech in writing

So, the structure of the cerebral cortex involves viewing it in horizontal and vertical orientation. Depending on this, vertical columns of neurons and zones located in the horizontal plane are distinguished. The main functions performed by the cortex are the implementation of behavior, regulation of thinking, and consciousness. In addition, it ensures the interaction of the body with the external environment and takes part in controlling the functioning of internal organs.