Extrapyramidal motor system. Extrapyramidal system and syndromes of its defeat. extrapyramidal system. Basic principles of the structure. Violation of movements in the defeat of different levels of the extrapyramidal system. Basic structure of the cerebellum and its

Each person performs conscious actions, the pyramidal system of the brain is directly responsible for these processes. How are involuntary reactions triggered? These processes occur due to the functioning of the extrapyramidal system. This article will discuss its structure, main functions and possible complications in case of serious violations.

General concept of ES

So, for all conscious movements (walking, speech, hand movements, etc.) the pyramidal system is responsible. However, deep in the human brain is a special extrapyramidal system, which is responsible for all our new skills and abilities.

Scientists divided its formation (evolution) into two separate periods:

neostrianar;
paleostrionic.

The first arose much earlier than the paleostrionic one; in the aggregate, they complement each other. Due to it, processes of slowing down motor activity occur, which in turn are triggered by the second system.

ES originates in the brain (at the site of the pons varolii and the prolongation of the brain) and goes to the sections of the spinal cord. It is considered one of the first who are responsible for human motor activity.

ES functions

The pyramidal system is responsible for conscious movements in the human body. For example, in order for a person to be able to bring a spoon or fork to his mouth while eating, he needs to think about it in advance. What processes are considered unconscious and do not require the participation of the cerebral cortex to run? You can get an answer only by studying in detail the functions of the extrapyramidal structure. So, she is responsible for:

regulatory processes of tone in muscle muscles. There is a group of muscles that does not relax even during the rest period. However, a person never thinks before “preparing” them for motor activity, this is done by ES;
protective reflexes of the body. For example, with a loud pop or sound, a person involuntarily closes his eyes or shudders;
maintaining balance. AT this case when a person slips on ice: the slope of the body changes, hands are connected. All this is done at an unconscious level with the participation of ES;
skills that are acquired during the life cycle and are reinforced. In this case, they talk about the "Caesar" syndrome, which performed several actions at the same time. A person can work quietly and at the same time talk on the phone. All this became possible with the help of a unique extrapyramidal complex.

If one of the sections of this structure is affected, a person develops serious impairments in coordination, etc. To understand these processes in more detail, let us consider its structure in detail.

It is a separate area that is found deep in the cerebral cortex. Since this structure is considered one of the oldest, it is characterized by the formation of a nucleus. A detailed study of ES began in the second half of the 19th century. Then scientists found that the nucleus consists of three components:

striatum (stiatrum), which is divided into two separate sections: caudate and lenticular. The latter consists of a pale layer and a shell;
fence, which is located between the layers of gray matter. There is little information about it, the functions have not been fully studied by scientists;
almond-shaped area, which is directly connected with the subcortical system of the olfactory organs and the limbic system;
red nuclei, which have a paired nature. It is from this area that unconscious impulses originate, they are directed to the muscular muscles of the skeleton. There is the concept of the Trout cross, thanks to which all processes are launched from two sides. The red hue is due to the presence of blood capillaries and a high content of ferrum;
the cerebellum does not belong to the extrapyramidal system, but it is fully involved in all unconscious processes of the human body;
black content, which is characterized by pairing. It got its name from high content melanin pigment. Anatomical location - between the leg and the tire of the brain. It is supplied with a large number of blood vessels, is directly connected with the parts of the brain.

Relationships between the structures of the extrapyramidal system

Until now, the processes of interaction remain not fully understood. ES is directly connected with the thalamus, reticulative nuclei, pons, cerebellum, etc. For full functioning, gamma-motor neutrons of the spinal cord sections are added to all of the above structures.

This system is closely related to the pyramidal structure. Thanks to this interaction, all movements that are provoked by sections of the pyramidal system are ordered in a person. The processes of the red nucleus of the extrapyramidal system form the so-called rubrospinal tract. It is responsible for the motor processes of the upper limbs of a person.

The vestibular region of the ES is closely related to the region of the inner ear, cerebellum, and some parts of the spinal cord. Thanks to this, a person makes movements with his neck, torso, head and limbs. In addition, the relationship with various structures of the brain provides the functions of blinking, turning the head and controlling muscle contractions. If one of the processes is violated, a person experiences various complications.

ES malfunctions

When a number of negative factors or diseases affect the human body, the extrapyramidal system malfunctions. This is accompanied by increased or decreased muscle tone, posture curvature, and reflex disorders. Such disorders were recorded during long-term use of drugs of the antipsychotic group (they have a direct effect on parts of the brain).

Among the most famous disorders of the extrapyramidal system, dyskinesia, dystonia, etc. can be distinguished. For example, with prolonged use of neuroleptic drugs, the patient is diagnosed with "rabbit syndrome". This is a condition that is accompanied by involuntary contractions of the perioral muscle muscles. Treatment of this pathology is very complex and lengthy. A person may also experience involuntary muscle contractions in the face or neck.

It is important to note that violations of the extrapyramidal system are associated with the presence of traumatic brain injuries in humans, brain diseases (, menningitis, etc.), problems with blood vessels in the brain, genetic diseases, trauma to the child during childbirth, the presence of neoplasms in the brain and etc. Parkinson's disease is the result of a violation of the ES. The patient has a strong tremor of the limbs, speech becomes monotonous, facial expressions are disturbed.

In the case of damage to the substantia nigra of the ES, the patient's reflex functions significantly increase from the time of taking the primary specific posture. With the defeat of palladium, the patient is diagnosed with muscle hypertension, which is also called wax. In this case, when making movements, the posture of a person remains unchanged. For such patients, stiffness in movements is characteristic, facial expressions are completely absent (the expression resembles a mask). To make this or that movement (for example, to straighten the arm) requires a lot of effort.

Treatment of problems associated with ES disorders is long and complicated. Elderly people are susceptible to such pathologies, they are prescribed maintenance drug therapy.

Conclusion

Until recently, problems with disorders of the extrapyramidal system remain not fully understood. They are varied: from increased flexibility to complete stupor, the disappearance of necessary functions and the appearance of new ones, the development of tremors or nervous tics, chorea or hyperkinesis of a different nature.

These pathologies develop in a person, both throughout life and have a one-time character, they are the result of poor heredity. At the first unpleasant symptoms, it is recommended to immediately undergo a diagnosis. Treatment stretches for a lifetime, and a person is not a full-fledged member of society. However, scientists manage to create new modern drugs that help eliminate these problems.

In these structures, impulses are transmitted to the intercalary nerve cells and then descend as tegmental, red nuclear-spinal, reticular and vestibulo-spinal and other pathways to the motor neurons of the anterior horns of the spinal cord. Through these pathways, the extrapyramidal system influences spinal motor activity. The extrapyramidal system, consisting of projection efferent nerve pathways starting in the cerebral cortex, including the nuclei of the striatum, some nuclei of the brain stem and the cerebellum, regulates movements and muscle tone. It complements the cortical system of voluntary movements, voluntary movement becomes prepared, finely "tuned" for execution.

The pyramidal pathway (through the interneurons) and fibers of the extrapyramidal system ultimately occur on the anterior horn motor neurons, alpha and gamma cells, and influence them by both activation and inhibition.

The extrapyramidal system is phylogenetically older (especially its pallidar part) than the pyramidal system. With the development of the pyramidal system, the extrapyramidal system moves into a subordinate position.

The extrapyramidal system consists of the following main structures: the caudate nucleus, the shell of the lenticular nucleus, the pale ball, the subthalamic nucleus, the black substance and the red nucleus. The level of the lower order of this system is the reticular formation of the tegmentum of the brainstem and the spinal cord. FROM further development of the animal world, the paleostriatum (pale ball) began to dominate these structures. Then, in higher mammals, the neostriatum (caudate nucleus and shell) acquires a leading role. As a rule, phylogenetically later centers dominate over earlier ones. This means that in lower animals the supply of innervation of movements belongs to the extrapyramidal system. Fish are a classic example of "pallidar" creatures. In birds, a fairly developed neostriatum appears. In higher animals, the role of the extrapyramidal system remains very important, despite the fact that, as the cerebral cortex develops, phylogenetically older motor centers (paleostriatum and neostriatum) are increasingly controlled by a new motor system, the pyramidal system.

The striatum is the leading center among the structures that make up the extrapyramidal system. It receives impulses from various areas of the cerebral cortex, especially from the frontal motor area of the cortex, which includes fields 4 and 6. These afferent fibers are organized in a somatotopic projection, go ipsilaterally and are inhibitory (braking) in their action. Reaches the striatum and another system of afferent fibers coming from the thalamus. From the caudate nucleus and the shell of the lenticular nucleus, the main afferent fibers are directed to the lateral and medial segments of the globus pallidus, which are separated from each other by the internal medullary plate. There are connections from the ipsilateral cerebral cortex to the substantia nigra, the red nucleus, the subthalamic nucleus, and the reticular formation.

The caudate nucleus and the shell of the lenticular nucleus have two "channels" of connections with the substantia nigra. On the one hand, afferent nigrostriatal fibers are described as dopaminergic and reduce the inhibitory function of the striatum. On the other hand, the strionigral pathway is GABAergic and has an inhibitory effect on dopaminergic nigrostriatal neurons. These are closed rings. feedback. GABAergic neurons, through the gamma neurons of the spinal cord, control muscle tone.

All other efferent fibers of the striatum pass through the medial segment of the globus pallidus. They form rather thick bundles of fibers. One of these bundles is called the lenticular loop. Its fibers originate in the ventral part of the medial segment of the pale nucleus and run ventromedially around the posterior crus of the internal capsule to the thalamus and hypothalamus, as well as reciprocally to the subthalamic nucleus. After crossing, they connect with the reticular formation of the midbrain, from which a chain of neurons forms the reticular-spinal tract (descending reticular system), ending in the cells of the anterior horns of the spinal cord.

The main part of the efferent fibers of the pale ball goes to the thalamus. This is the pallidothalamic bundle, or Trout field H1. Most of its fibers end in the anterior thalamic nuclei, which project to cortical area 6. The fibers that start in the dentate nucleus of the cerebellum end in the posterior thalamic nucleus, which projects to cortical area 4. All these thalamocortical connections transmit impulses in both directions. In the cortex, thalamocortical pathways synapse with corticostriatal neurons and form feedback loops. Reciprocal (coupled) thalamocortical junctions facilitate or inhibit the activity of cortical motor fields.

The fibers of the basal nuclei that descend to the spinal cord are relatively few and reach the spinal cord only through a chain of neurons. This nature of the connections suggests that the main function of the basal ganglia is to control and regulate the activity of the motor and premotor cortical fields, so voluntary movements can be performed smoothly, continuously.

The pyramidal path begins in the sensorimotor region of the cerebral cortex (fields 4, 1,2, 3). These are at the same time the fields in which the extrapyramidal motor pathways begin, which include corticostriatal, corticorubral, corticonigral and corticoreticular fibers going to the motor nuclei of the cranial nerves and to the spinal motor nerve cells through descending chains of neurons.

Most of these cortical connections pass through the internal capsule. Consequently, damage to the internal capsule interrupts not only the fibers of the pyramidal pathway, but also the extrapyramidal fibers. This break is the cause of muscle spasticity.

Semiotics of extrapyramidal disorders. The main signs of extrapyramidal disorders are disorders of muscle tone (dystonia) and involuntary movements (hyperkinesis, hypokinesis, akinesis), which are absent during sleep. Two can be distinguished clinical syndrome. One of them is characterized by a combination of hyperkinesis (automatic violent movements due to involuntary muscle contractions) and muscle hypotension and is caused by damage to the neostriatum. The other is a combination of hypokinesis and muscle hypertension or rigidity, and is seen with involvement of the medial globus pallidus and substantia nigra.

Akinetic-rigid syndrome (syn.: amyostatic, hypokinetic-hypertonic, pallidonigral). This syndrome in its classical form is found in tremor paralysis, or Parkinson's disease. The pathological process in this disease is degenerative, leading to the loss of melanin-containing neurons of the substantia nigra. The lesion in Parkinson's disease is usually bilateral. With unilateral cell loss, clinical signs are observed on the opposite side of the body. In Parkinson's disease, the degenerative process is hereditary. This loss of substantia nigra neurons may be due to other causes. In such cases, trembling paralysis is referred to as Parkinson's syndrome or parkinsonism. If it is a consequence of lethargic encephalitis, it is called postencephalitic parkinsonism. Other conditions (cerebral atherosclerosis, typhoid, cerebral syphilis, primary or secondary involvement of the midbrain in a tumor or injury, intoxication with carbon monoxide, manganese and other substances, long-term use of phenothiazine or reserpine) can also cause parkinsonism.

The clinical manifestations of the akinetic-rigid syndrome are characterized by three main features: hypokinesia (akinesis), rigidity and tremor. With hypokinesia, the patient's mobility slowly decreases. All mimic and expressive movements gradually drop out or slow down sharply. Starting a movement, such as walking, is very difficult. The patient first takes a few short steps. Having started the movement, he cannot suddenly stop and takes a few extra steps. This continued activity is called propulsion. Facial expression becomes mask-like (hypomimia, amimia). Speech becomes monotonous and dysarthric, partly caused by rigidity and tremor of the tongue. The body is in a fixed flexion position of anteflexion, all movements are exceptionally slow and unfinished.

Hands do not participate in the act of walking (acheirokinesis). All mimic and friendly expressive movements characteristic of the individual are absent.

In contrast to the spastic increase in muscle tone, rigidity can be felt in the extensors as a "wax" resistance to all passive movements. Muscles cannot be relaxed. With passive movements, one can feel that the tone of the antagonist muscles decreases stepwise, inconsistently (a symptom of a cogwheel). The raised head of a lying patient does not fall when suddenly released, but gradually falls back onto the pillow (head drop test). In contrast to the spastic state, proprioceptive reflexes are not increased, and pathological reflexes and paresis are absent. It is difficult to evoke reflexes and it is impossible to increase the knee jerk with the Jendraszyk maneuver.

In most patients, a passive tremor is detected, which has a low frequency (4–8 movements per second). Passive tremor is rhythmic and is the result of the interaction of agonists and antagonists (antagonistic tremor). In contrast to intentional tremor, antagonistic tremor stops during purposeful movements. Rolling pills or counting coins are signs of Parkinson's tremor.

The mechanism that causes the appearance of the three listed signs has not been fully elucidated. Akinesis is possibly related to the loss of dopaminergic transmission of impulses to the striatum. Akinesis can be explained as follows: damage to the neurons of the substantia nigra causes the loss of the influence of inhibitory descending nigroreticulospinal impulses on Renshaw cells. Renshaw cells, which have a connection with large?-motor neurons, reduce the activity of the latter by their inhibitory effect, which makes the initiation of voluntary movement more difficult.

Rigidity can also be explained by the loss of substantia nigra neurons. Normally, these neurons have an inhibitory effect on striatal impulses, which in turn inhibit the globus pallidus. Their loss means that efferent pallidar impulses are not inhibited. The descending path of the pale ball forms synapses with reticulospinal neurons; which facilitate the action of intercalary neurons in the circuit of the tonic stretch reflex. In addition, impulses emanating from the medial part of the globus pallidus reach area 6a through the thalamic nuclei and, through the corticospinal fibers, also have a facilitating effect on the intercalary neurons in the tonic stretch reflex circuit. There is a violation of muscle tone, called rigidity.

If the efferent cells and fibers of the globus pallidus are destroyed by stereotaxic surgery in its medial part or in the region of the lenticular loop, or the thalamic nucleus, rigidity decreases.

Stereotactic operations of coagulation of the medial part of the pale ball, pallidothalamic fibers or dentatothalamic fibers and their terminal thalamic nucleus are shown in some patients.

Hyperkinetic-hypotonic syndrome. Develops with damage to the striatum. Hyperkinesias are caused by damage to the inhibitory neurons of the neostriatum, the fibers of which lead to the globus pallidus and substantia nigra. In other words, there is a violation of neuronal systems of a higher order, which leads to excessive excitation of neurons of the underlying systems. The result is hyperkinesia. various types: athetosis, chorea, spastic torticollis, torsion dystonia, ballism, etc.

Athetosis is usually caused by perinatal damage to the striatum. It is characterized by involuntary slow and worm-like movements with a tendency to hyperextension of the distal parts of the limbs. In addition, there is an irregular, spastic increase muscle tension in agonists and antagonists. As a result, postures and movements are rather eccentric. Voluntary movements are significantly impaired due to the spontaneous onset of hyperkinetic movements, which can involve the face, tongue and thus cause grimaces with abnormal tongue movements. Spasmodic bursts of laughter or crying are possible. Athetosis can be combined with contralateral paresis. It can also be bilateral.

Facial paraspasm - tonic symmetrical contractions of the facial muscles of the mouth, cheeks, neck, tongue, eyes. Sometimes blepharospasm is observed - an isolated contraction of the circular muscles of the eyes, which can be combined with clonic convulsions of the muscles of the tongue and mouth. Paraspasm occurs sometimes during a conversation, eating, smiling. Increases with excitement, bright lighting. Disappears in a dream.

Choreic hyperkinesis is characterized by short, rapid, involuntary twitchings that develop randomly in the muscles and cause various kinds of movements, sometimes resembling arbitrary ones. First, the distal parts of the limbs are involved, then the proximal ones. Involuntary twitches of the facial muscles cause grimaces. In addition to hyperkinesis, a decrease in muscle tone is characteristic. Choreic movements with slow development can be a pathognomonic sign in Huntington's chorea and chorea minor, secondary to other brain diseases (encephalitis, carbon monoxide poisoning, vascular diseases). The striatum is affected.

Spasmodic torticollis and torsion dystonia are the most important dystonic syndromes. In both diseases, the putamen and centromedial nucleus of the thalamus are usually affected, as well as other extrapyramidal nuclei (globus pallidus, substantia nigra, etc.). Spasmodic torticollis is a tonic disorder that is expressed in spastic contractions of the muscles of the cervical region, leading to slow, involuntary turns and tilts of the head. Patients often use compensatory techniques to reduce hyperkinesis, in particular, they support their heads with their hands. In addition to other muscles of the neck, the sternocleidomastoid and trapezius muscles are especially often involved in the process.

Spasmodic torticollis may be an abortive form of torsion dystonia or an early symptom of another extrapyramidal disease (encephalitis, Huntington's chorea, hepatocerebral dystrophy).

Torsion dystonia is characterized by passive rotational movements of the trunk and proximal limb segments. They can be so pronounced that without support the patient can neither stand nor walk. The disease can be symptomatic or idiopathic. In the first case, birth trauma, jaundice, encephalitis, early Huntington's chorea, Hallervorden-Spatz disease, hepatocerebral dystrophy (Wilson-Westphal-Strumpel disease) are possible.

Ballistic syndrome usually occurs in the form of hemiballismus. It is manifested by rapid contractions of the proximal muscles of the limbs of a rotating nature. With hemiballismus, the movement is very powerful, strong (“throwing”, sweeping), since very large muscles contract. Arises as a result of damage to the subthalamic nucleus of Lewis and its connections with the lateral segment of the pale ball. Hemiballismus develops on the side contralateral to the lesion.

Myoclonic twitches usually indicate a lesion in the area of the Guillien-Mollare triangle: the red nucleus, the inferior olive, the dentate nucleus of the cerebellum. These are fast, usually erratic contractions of various muscle groups.

Tics are rapid involuntary muscle contractions (most commonly the orbicularis oculi and other facial muscles).

The extrapyramidal system is a set of structures (formations) of the brain involved in the control of movements, maintaining muscle tone and posture, bypassing the corticospinal (pyramidal) system. The structure is located in the cerebral hemispheres and the brain stem.

Extrapyramidal pathways are formed by descending projection nerve fibers, which by origin are not related to the giant pyramidal cells (Betz cells) of the cerebral cortex. These nerve fibers provide connections between motor neurons of subcortical structures (cerebellum, basal ganglia, brain stem) of the brain with all departments nervous system located more distally.

The extrapyramidal system carries out involuntary regulation and coordination of movements, regulation of muscle tone, maintenance of posture, organization of motor manifestations of emotions (laughter, crying). Provides smooth movements, sets the initial posture for their implementation.

When the extrapyramidal system is damaged, motor functions are impaired (for example, hyperkinesis, parkinsonism may occur), muscle tone decreases.

Functionally, the extrapyramidal system is inseparable from the pyramidal system. It provides an orderly course of arbitrary movements, regulated by the pyramidal system; regulates congenital and acquired automatic motor acts, ensures the establishment of muscle tone and maintaining body balance; regulates accompanying movements (for example, hand movements when walking) and expressive movements (facial expressions).

pyramid system , this is a system of nervous structures that supports complex and fine coordination of movements. The pyramidal system is one of the late acquisitions of evolution. The lower vertebrates do not have this system, it appears only in mammals, and reaches its greatest development in monkeys and especially in humans. The pyramidal system plays a special role in bipedal locomotion. It begins in the cerebral cortex, on pyramidal cells (Betz), innervates small muscles responsible for fine differentiated hand movements, facial expressions and speech act. A significantly smaller number innervates the muscles of the trunk and lower extremities, organizing voluntary movements.

16. Areas of the BP cortex. There are three projection zones in the cerebral cortex:

Primary projection area occupies the central part of the core of the brain analyzer. This is a set of the most differentiated neurons, in which the highest analysis and synthesis of information takes place, clear and complex sensations arise. Impulses approach these neurons along a specific pathway for transmitting impulses to the cerebral cortex (the spinothalamic pathway).

Secondary located around the primary, is part of the brain section of the analyzer. Provides complex perception. With the defeat of this zone, a complex dysfunction occurs. Sensitivity to stimuli is usually not impaired, but the ability to interpret the meaning of the stimulus is impaired.

Tertiary projection zone- associative - these are polymodal neurons scattered throughout the cerebral cortex. They receive impulses from the associative nuclei of the thalamus and converge impulses of various modalities. Provides communication between various analyzers and participates in the formation of conditioned reflexes.

GBOU VPO Nizhny State Medical Academy of the Ministry of Health of the Russian Federation

Department: normal anatomy

"Extrapyramidal system"

The work was done by a 2nd year student

medical faculty

Sharova Ludmila Yurievna

Group: 242

Checked by: Bezdenezhnykh Andrey Vyacheslavovich

Nizhny Novgorod,

Definition of "extrapyramidal system"

History of study

Description

Classification according to topographic and functional criteria

Conducting paths

Bibliography

Extrapyramidal system (lat.: extra - outside, outside, aside + pyramis, Greek: πϋραμίς - pyramid) - a set of subcortical and stem formations, motor pathways that do not pass through the pyramids of the medulla oblongata. This system, along with the cortical one, is involved in the control of movements, and, being the most phylogenetically ancient, plays a significant role in the construction and control of movements that do not require activation of attention.

History of study.

For the first time, the idea that the state of motor functions is influenced not only by the formations that make up the pyramidal system was expressed by the English neurologist S. Wilson in 1908. in the process of studying the disease now known as Wilson-Konovalov disease. Since then, all brain structures that affect the state of striated muscles and are involved in providing movements have been called extrapyramidal.

At the suggestion of R. Granit (Granit R., 1973), the structures of the pyramidal pathways, on which the active movements of the body and its parts depend, were called phasic. Extrapyramidal structures that affect motor acts, position, maintaining the balance of the body and its posture are tonic.

N.K. Bogolepov noted that the extrapyramidal system is also involved in the performance of expressive, facial and emotional reactions.

In 1973, the leading American physiologist P. Milner expressed doubts about the existence of separate extrapyramidal and pyramidal systems. However, at the moment, after a thorough study of the functions of both systems, their isolation is undeniable.

Description

The E. system, in comparison with the pyramidal one, is phylogenetically older (especially its pallidar part). With the development of the pyramidal system, the extrapyramidal system moves into a subordinate position.

The extrapyramidal system consists of the following brain structures:

basal ganglia (including the striatum), red nucleus, interstitial nucleus, tectum, substantia nigra, reticular formation of the brainstem, nuclei of the vestibular complex, cerebellum, inferior olive of the medulla oblongata.

Nucleus basales - accumulations of gray matter in the thickness of the cerebral hemispheres.

Corpus striatum (striated body) consists of n.caudatus and n.lentiformis.

Caudate nucleus - has the form of a comma located in the sagittal plane. Consists of three parts: caput, corpus and cauda. The anterior part of the head is fused with the white matter of the frontal lobe, with its free surfaces (upper and medial) the body of the caudate nucleus in the temporal lobe forms the bottom of the central part of the lateral ventricle. The tail is directed to the temporal lobe of the hemisphere, where it reaches the amygdala. Participates in the organization of motor activity, the formation of conditioned reflexes and memory mechanisms.

Lenticular nucleus - lies laterally from the caudate nucleus and the visual mound and consists of two parts - the lateral, larger and medial, shell (putamen) and pale ball (globus pallidus). The function of the lenticular nucleus is the regulation of muscle tone.

Subthalamic nucleus (Lewis) - accumulation of gray matter with fibers penetrating it. Adjacent to the surface of the inner capsule, which separates it from the pale ball, with which the nucleus is connected by a large number of fibers passing as part of the subthalamic bundle.

black matter - the core of the es, which lies at the base of the legs of the brain, is involved in the distribution of muscle tone necessary to set the body in a certain position.

red core - the gray matter of the tegmentum of the midbrain, is the first integrative control center of the limbs.

Intermediate nucleus (Cajal) - is contained in the reticular formation of the midbrain, gives rise to the medial longitudinal bundle, which is an important associative pathway connecting the various nuclei of the nerves of the eye muscles with each other, which determines the combined movements of the eyes when they deviate in one direction or another. Its function is also associated with the movements of the eyes and head that occur when the balance apparatus is stimulated.

Plate of the quadrigemina - part of the midbrain, which is a reflex center of various kinds of movements that occur, g.o. under the influence of visual and auditory stimuli.

lower olive - an oval elevation located on the sides of each pyramid of the medulla oblongata. Separated from the last anterolateral groove. Plays an important role in the gastrocolic reflex, conducts fibers from the medial spinal cerebellar tract

Cerebellum - part of the hindbrain responsible for the regulation of posture and muscle tone, sensorimotor coordination of postural and purposeful movements, coordination of fast purposeful movements.

Part of the structures of the e.s. participates in the formation of its higher department, the so-called striopallidary system, consisting of pallidum (a more phylogenetically ancient formation, consisting of a pale ball, Lewis nucleus, red nucleus, black substance) and striatum (a younger part, consisting of a shell and a fence).

Despite the unification of the striatum and pallidum into a single system, functionally these structures differ from each other. Pallidum is a motor nucleus that has an activating effect on subcortical formations. The pale ball receives afferent impulses along the fibers coming from the striatum and subthalamic nucleus. Part of the fibers follow to the thalamic nuclei, neurons of the red and tegmental nuclei. The pale ball, being effectorally connected with the centers of the middle and hindbrain, regulates and coordinates their work. One of the functions of the pallidum is the inhibition of the underlying nuclei, mainly the red nucleus of the midbrain, therefore, if the pale ball is damaged, there is a strong increase in the tone of the skeletal muscles - hypertonicity due to the release of the red nucleus from the inhibitory influence of the pale ball.

The striatum also has an inhibitory effect on the subcortical structures. The striatum receives afferent impulses mainly from the cerebral hemispheres and the thalamus and sends efferent impulses mainly to the globus pallidus. Part of the efferents without switching goes to the black substance. A small number of fibers go to the subthalamic and red nucleus, lower olive, blue spot, raphe nuclei. The striatum is considered as an effector nucleus that does not have independent motor functions, but controls the functions of the pallidum. The striatum inhibits the activity of the pale ball, that is, it acts on it in the same way as it itself acts on the red nucleus.

Classification


(substantia grisea) Nucleus basales (corpus striatum, n, amygdaloideum)		Activatiopallidum	Akinetic-rigid syndrome (hypomymia, bradykinesia)
Nucleus subthalamicus	Ballism and hemiballism
Substantia grisea, nucleus ruber, n. intersticieles, lamina tecti,	parkinsonism	Reactivatio-striatum	Hypotonic-hyperkinetic syndrome (hyperkinesis, athetosis)
Medulla oblongata Oliva inferior, nucleus vestibularis

Formation reticularis trunci encephali

Functioning of the e.s. carried out using numerous specialized pathways:

Afferent cortical pathways originate from numerous sections of the cerebral cortex, especially from the motor areas of the frontal region (precentral gyrus, paracentral lobule). Most likely, these fibers are inhibitory. Another system of afferent fibers that appears to be activating reaches the striatum from the thalamic centromedian nucleus. In addition, a system of cortical fibers is distinguished, providing bilateral connections between the substantia nigra and the striatum. Dopaminergic (afferent nigrostitial) fibers - reduce the inhibitory function of the striatum (about 80% of dopamine is released by the axons of the neurons of these pathways, (the nigrostriatal system, the axons of which neurons release about 80% of dopamine- neurotransmitter in the endings of some axons of peripheral nerves and many CNS neurons. Dopamine is one of the chemical factors of internal reinforcement (EFF) and serves as an important part of the “reward system” of the brain, since it causes a feeling of pleasure (or satisfaction), which affects the processes of motivation and learning). On the other hand, the strionigral pathway is GABAergic and has an inhibitory effect on dopaminergic neurons.

Efferent tractus rubrospinalis, tractus tectospinalis, tractus vestibulospinalis, tractus reticulospinalis, tractus olivispinalis.

Rubro-spinal (Monakov's path) the tract starts from the red nucleus of the midbrain, after exiting this path crosses again (Forel's cross) is located in the lateral cords and ends in the V-VII plates of the spinal cord (intermediate zone). There are no direct connections with motor neurons. Participates in the organization of the movement of the entire muscles of the trunk and limbs (walking, running), controls the tone of the flexors, making these movements plastic, helping to maintain a certain posture for a long time.

Vestibulo-spinal tracts (lateral and ventral) activate motor systems related to body balance and direction of movement. They start from the large vestibular nuclei of the medulla oblongata and the bridge, the olive of the medulla oblongata and ends in the VII - IX plates of the spinal cord (anterior horn area). The lateral tract (passing in the lateral cord) ends in the region of the cervical regions, and the ventral tract (passing in the anterior cord) in the lumbar regions. They control and organize the redistribution of muscle tone with any change in the position of the body and head in space, control the tone of the extensor muscles.

Reticulo-spinal tracts are represented by axons of neurons of the reticular formation of the bridge and the medulla oblongata. They pass in the anterior cord, forming two paths: medial and lateral, and end in the region of the motor nuclei of the IX plate, as well as in the region of the VI-VIII plates. The importance of this tract in the mechanism of maintaining and distributing muscle tone and regulation of postures, participation in diffuse inhibition of the entire musculature is necessary in some behavioral acts, for example, when the body overheats. This pathway mediates the activating influence of the respiratory and vasomotor centers.

Tecto-spinal the tract originates in the deep layers of the tubercles of the quadrigemina of the midbrain, passes as part of the ventral cords and ends on the interneurons of the VII-VIII plates of the spinal cord (anterior horn region). Functionally, the tecto-spinal pathways are associated with the coordination of movements of the head and trunk in response to visual and sound signals and ensure the implementation of the sentinel reflex in humans.

Olivo-spinal the tract originates from the lower nucleus of the olive of the medulla oblongata, it has direct connections with the cortex of the hemispheres of the frontal lobe (cortical-olive path), with the red nucleus (red nuclear-olive path) and the cortex of the cerebellar hemispheres (olive-cerebellar path). The axons of the cells of the lower nucleus are collected in a bundle, which can be traced in the antero-medial section of the lateral funiculus and ends in the motor nuclei of the anterior horns of the spinal cord. Provides unconditioned reflex maintenance of the tone of the muscles of the neck, head and motor acts aimed at maintaining the balance of the body.

Impulses from the extrapyramidal system, as well as from the cerebellum and from the pyramidal system, therefore, flow to the cells of the anterior horn, where all the conductors just listed end. The final path to the muscle passes through the peripheral motor neuron.

Associative (connections of neurons of the extrapyramidal system with each other)

Extrapyramidal disorders can be divided into two clinical syndromes: akinetic-rigid and hyperkinetic-hypotonic

Options for reducing motor activity are: akinesia - lack of movement, bradykinesia - slowness of movement, oligokinesia - poor movement, hypokinesia - lack of motor activity.

Rigidity is the constant presence of muscles in a state of tonic tension, which is characteristic of both agonist muscles and antagonist muscles, in connection with which the plastic nature of the increase in muscle tone is manifested.

In the initial stage of akinetic-rigid syndrome, muscle rigidity in Parkinson's disease is usually asymmetrical, can manifest itself in any one part of the body, but later, as the disease progresses, it becomes more common and generalized over time.

Hypotonic-hyperkinetic syndrome develops with damage to the caudate nucleus and the shell (in these formations there is an excess of excitation mediators - dopamine, etc.). Distinguish:

athetosis - slow artsy tonic nature of movement, mainly in the distal limbs, sometimes in the muscles of the face (protrusion of the lips, etc.)

choreic hyperkinesis (the most common form) - fast non-rhythmic movements in the distal and proximal parts of the limbs, face, torso.

So, functionally, e.s. very closely related to the more phylogenetically young, pyramidal. But at the same time, it has a certain role, which consists in 1. Regulation of muscle tone in combination with other structures.

2. Regulation of tempo, rhythm and plasticity of any arbitrary motor act.

3. Providing a motor component in the regulation of unconditioned reflexes (sexual, defensive, start reflex, etc.).

4. Ensuring the sequence of a motor act.

5. Providing the motor component of the emotional sphere.

6. Regulation of highly specialized human movements that have reached the level of automatisms

Bibliography:

Burd, Gusev, Konovalov - Neurology and Neurosurgery

General neurology A.S. Nikiforov, E.I. Gusev - 2007 - 720 s

Human pneumopsychosomatology, Trifonov E.V. Russian-English Encyclopedia 2013

Normal human anatomy, Gaivoronsky I.V. 2001

"Topical diagnosis of diseases of the nervous system", A.V. Triumfov

Topical diagnosis in neurology, Petter Duus

3.2. Extrapyramidal system

The term "extrapyramidal system" refers to subcortical and stem extrapyramidal formations and motor pathways that do not pass through the pyramids of the medulla oblongata. Part of this system are also those bundles that connect the cerebral cortex with the extrapyramidal gray structures: the striatum, the red nucleus, the substantia nigra, the cerebellum, the reticular formation and the nuclei of the trunk tegmentum. In these structures, impulses are transmitted to intercalary nerve cells and then descend as tegmental, red nuclear-spinal, reticular and vestibulo-spinal and other pathways to the motor neurons of the anterior horns of the spinal cord. Through these pathways, the extrapyramidal system influences spinal motor activity. The extrapyramidal system, consisting of projection efferent nerve pathways starting in the cerebral cortex, including the nuclei of the striatum, some nuclei of the brain stem and the cerebellum, regulates movements and muscle tone. It complements the cortical system of voluntary movements, voluntary movement becomes prepared, finely "tuned" for execution.

The pyramidal pathway (through the interneurons) and fibers of the extrapyramidal system ultimately occur on the anterior horn motor neurons, alpha and gamma cells, and affect them by both activation and inhibition.

The extrapyramidal system consists of the following main structures: the caudate nucleus, the shell of the lenticular nucleus, the pale ball, the subthalamic nucleus, the black substance and the red nucleus. The level of the lower order of this system is the reticular formation of the tegmentum of the brainstem and the spinal cord. With the further development of the animal world, the paleostriatum (pale ball) began to dominate these structures. Then, in higher mammals, the neostriatum (caudate nucleus and shell) acquires a leading role. As a rule, phylogenetically later centers dominate over earlier ones. This means that in lower animals the supply of innervation of movements belongs to the extrapyramidal system. Fish are a classic example of "pallidar" creatures. In birds, a fairly developed neostriatum appears. In higher animals, the role of the extrapyramidal system remains very important, despite the fact that, as the cerebral cortex develops, phylogenetically older motor centers (paleostriatum and neostriatum) are increasingly controlled by a new motor system, the pyramidal system.

striatum- the leading center among the structures that make up the extrapyramidal system. It receives impulses from various areas of the cerebral cortex, especially from the frontal motor area of the cortex, which includes fields 4 and 6. These afferent fibers are organized in a somatotopic projection, go ipsilaterally and are inhibitory (braking) in their action. Reaches the striatum and another system of afferent fibers coming from the thalamus. From the caudate nucleus and the shell of the lenticular nucleus, the main afferent fibers are directed to the lateral and medial segments of the globus pallidus, which are separated from each other by the internal medullary plate. There are connections from the ipsilateral cerebral cortex to the substantia nigra, the red nucleus, the subthalamic nucleus, and the reticular formation.

Caudate nucleus and shell of the lenticular nucleus have two "channels" of connections with black matter. On the one hand, afferent nigrostriatal fibers are described as dopaminergic and reduce the inhibitory function of the striatum. On the other hand, the strionigral pathway is GABAergic and has an inhibitory effect on dopaminergic nigrostriatal neurons. These are closed feedback loops. GABAergic neurons, through gamma neurons in the spinal cord, control muscle tone.

All other efferent fibers of the striatum pass through the medial segment pale ball. They form rather thick bundles of fibers. One of these bundles is called the lenticular loop. Its fibers originate in the ventral part of the medial segment of the pale nucleus and run ventromedially around the posterior crus of the internal capsule to the thalamus and hypothalamus, as well as reciprocally to the subthalamic nucleus. After crossing, they connect with the reticular formation of the midbrain, from which a chain of neurons forms the reticular-spinal tract (descending reticular system), ending in the cells of the anterior horns of the spinal cord.

The pyramidal path begins in the sensorimotor region of the cerebral cortex (fields 4, 1,2, 3). It is at the same time the fields in which the extrapyramidal motor pathways begin, which include corticostriatal, corticorubral, corticonigral and corticoreticular fibers going to the motor nuclei of the cranial nerves and to the spinal motor nerve cells through the descending chains of neurons.

Semiotics of extrapyramidal disorders. The main signs of extrapyramidal disorders are disorders of muscle tone (dystonia) and involuntary movements (hyperkinesis, hypokinesis, akinesis), which are absent during sleep. Two clinical syndromes can be distinguished. One of them is characterized by a combination of hyperkinesis (automatic violent movements due to involuntary muscle contractions) and muscle hypotension and is caused by damage to the neostriatum. The other is a combination of hypokinesis and muscle hypertension or rigidity, and is seen with involvement of the medial globus pallidus and substantia nigra.

Akinetic-rigid syndrome(syn.: amyostatic, hypokinetic-hypertonic, pallidonigral). This syndrome in its classical form is found in tremor paralysis, or Parkinson's disease. The pathological process in this disease is degenerative, leading to the loss of melanin-containing neurons of the substantia nigra. The lesion in Parkinson's disease is usually bilateral. With unilateral cell loss, clinical signs are observed on the opposite side of the body. In Parkinson's disease, the degenerative process is hereditary. This loss of substantia nigra neurons may be due to other causes. In such cases, trembling paralysis is referred to as Parkinson's syndrome or parkinsonism. If it is a consequence of lethargic encephalitis, it is called postencephalitic parkinsonism. Other conditions (cerebral atherosclerosis, typhoid, cerebral syphilis, primary or secondary involvement of the midbrain in a tumor or injury, intoxication with carbon monoxide, manganese and other substances, long-term use of phenothiazine or reserpine) can also cause parkinsonism.

The clinical manifestations of the akinetic-rigid syndrome are characterized by three main features: hypokinesia (akinesis), rigidity and tremor. At hypokinesia the patient's mobility slowly decreases. All mimic and expressive movements gradually drop out or slow down sharply. Starting a movement, such as walking, is very difficult. The patient first takes a few short steps. Having started the movement, he cannot suddenly stop and takes a few extra steps. This continued activity is called propulsion. Facial expression becomes mask-like (hypomimia, amimia). Speech becomes monotonous and dysarthric, partly caused by rigidity and tremor of the tongue. The body is in a fixed flexion position of anteflexion, all movements are exceptionally slow and unfinished. Hands do not participate in the act of walking (acheirokinesis). All mimic and friendly expressive movements characteristic of the individual are absent.

In contrast to the spastic increase in muscle tone rigidity can be felt in the extensors as a "wax" resistance to all passive movements. Muscles cannot be relaxed. With passive movements, you can feel that the tone of the antagonist muscles decreases stepwise, inconsistently (a symptom of a cogwheel). The raised head of a lying patient does not fall when suddenly released, but gradually falls back onto the pillow (head drop test). In contrast to the spastic state, proprioceptive reflexes are not increased, and pathological reflexes and paresis are absent. It is difficult to evoke reflexes and it is impossible to increase the knee jerk with the Jendraszyk maneuver.

Most patients present with passive tremor having a low frequency (4-8 movements per second). Passive tremor is rhythmic and is the result of the interaction of agonists and antagonists (antagonistic tremor). In contrast to intentional tremor, antagonistic tremor stops during purposeful movements. Rolling pills or counting coins are signs of Parkinson's tremor.

The mechanism that causes the appearance of the three listed signs has not been fully elucidated. Akinesis is possibly related to the loss of dopaminergic transmission of impulses to the striatum. Akinesis can be explained as follows: damage to the neurons of the substantia nigra causes the loss of the influence of inhibitory descending nigroreticulospinal impulses on Renshaw cells. Renshaw cells, which have a connection with large α-motor neurons, reduce the activity of the latter by their inhibitory effect, which makes the initiation of voluntary movement more difficult.

If the efferent cells and fibers of the globus pallidus are destroyed by stereotaxic surgery in its medial part or in the region of the lenticular loop, or the thalamic nucleus, rigidity decreases.

Stereotactic operations of coagulation of the medial part of the pale ball, pallidothalamic fibers or dentatothalamic fibers and their terminal thalamic nucleus are shown in some patients.

Hyperkinetic-hypotonic syndrome. Develops with damage to the striatum. Hyperkinesias are caused by damage to the inhibitory neurons of the neostriatum, the fibers of which lead to the globus pallidus and substantia nigra. In other words, there is a violation of neuronal systems of a higher order, which leads to excessive excitation of neurons of the underlying systems. As a result, hyperkinesis of various types occurs: athetosis, chorea, spastic torticollis, torsion dystonia, ballism, etc.

Athetosis usually caused by perinatal damage to the striatum. It is characterized by involuntary slow and worm-like movements with a tendency to hyperextension of the distal parts of the limbs. In addition, there is an irregular, spastic increase in muscle tension in agonists and antagonists. As a result, postures and movements are rather eccentric. Voluntary movements are significantly impaired due to the spontaneous onset of hyperkinetic movements, which can involve the face, tongue and thus cause grimaces with abnormal tongue movements. Spasmodic bursts of laughter or crying are possible. Athetosis can be combined with contralateral paresis. It can also be bilateral.

Facial paraspasm- tonic symmetrical contractions of the facial muscles of the mouth, cheeks, neck, tongue, eyes. Sometimes blepharospasm is observed - an isolated contraction of the circular muscles of the eyes, which can be combined with clonic convulsions of the muscles of the tongue and mouth. Paraspasm occurs sometimes during a conversation, eating, smiling. Increases with excitement, bright lighting. Disappears in a dream.

Choreic hyperkinesis characterized by short, rapid, involuntary twitches that develop randomly in the muscles and cause various kinds of movements, sometimes resembling arbitrary ones. First, the distal parts of the limbs are involved, then the proximal ones. Involuntary twitches of the facial muscles cause grimaces. In addition to hyperkinesis, a decrease in muscle tone is characteristic. Choreic movements with slow development can be a pathognomonic sign in Huntington's chorea and chorea minor, secondary to other brain diseases (encephalitis, carbon monoxide poisoning, vascular diseases). The striatum is affected.

Spasmodic torticollis and torsion dystonia- the most important syndromes of dystonia. In both diseases, the putamen and centromedial nucleus of the thalamus are usually affected, as well as other extrapyramidal nuclei (globus pallidus, substantia nigra, etc.). Spasmodic torticollis is a tonic disorder that is expressed in spastic contractions of the muscles of the cervical region, leading to slow, involuntary turns and tilts of the head. Patients often use compensatory techniques to reduce hyperkinesis, in particular, they support their heads with their hands. In addition to other muscles of the neck, the sternocleidomastoid and trapezius muscles are especially often involved in the process.

Spasmodic torticollis may be an abortive form of torsion dystonia or an early symptom of another extrapyramidal disease (encephalitis, Huntington's chorea, hepatocerebral dystrophy).

ballistic syndrome usually occurs in the form of hemiballismus. It is manifested by rapid contractions of the proximal muscles of the limbs of a rotating nature. With hemiballismus, the movement is very powerful, strong (“throwing”, sweeping), since very large muscles contract. Arises as a result of damage to the subthalamic nucleus of Lewis and its connections with the lateral segment of the pale ball. Hemiballismus develops on the side contralateral to the lesion.

Myoclonic jerks usually indicate a lesion in the region of the triangle of Guillen - Mollare: the red nucleus, the inferior olive, the dentate nucleus of the cerebellum. These are fast, usually erratic contractions of various muscle groups.

Tiki- rapid involuntary muscle contractions (most often the circular muscle of the eye and other muscles of the face).

Hyperkinesis presumably develops as a result of the loss of the inhibitory effect of the striatum on the underlying neuronal systems (pale ball, substantia nigra).

Pathological impulses go to the thalamus, to the motor cortex, and then along the efferent cortical neurons.

In elderly patients with cerebral atherosclerosis, one can often find signs of Parkinson-like disorders or hyperkinesis, especially tremor, a tendency to repeat words and phrases, final syllables of words (logoclonia) and movements (polykinesia). There may be a tendency to pseudo-spontaneous movements, but true choreiform or athetoid movements are relatively rare. In most cases, the symptoms are due to miliary and somewhat large necrotic lesions of the striatum and globus pallidus, which are found in the form of scars and very small cysts. This condition is known as lacunar status. The tendency to recurrence and logoclonia is considered to be due to similar lesions of the caudate nucleus, and the tremor is due to the putamen.

Automated Actions- complex motor acts and other sequential actions that occur without consciousness control. Arise with hemispheric foci that destroy the connections of the cortex with the basal nuclei while maintaining their connection with the brain stem; appear in the limbs of the same name with the focus.

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General concept of ES

ES functions

Relationships between the structures of the extrapyramidal system

ES malfunctions

Conclusion

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