The cerebellum is best developed in birds. cerebellum - comparative anatomy and evolution

The cerebellum is a part of the vertebrate brain responsible for coordination of movements, regulation of balance and muscle tone. In humans, it is located behind the medulla oblongata and the pons, under the occipital lobes of the cerebral hemispheres. Through three pairs of legs, the cerebellum receives information from the cerebral cortex, the basal ganglia of the extrapyramidal system, the brain stem and spinal cord. Relationships with other parts of the brain may vary in different taxa of vertebrates.

In vertebrates with cerebral cortex, the cerebellum is a functional offshoot of the main cortex-spinal cord axis. The cerebellum receives a copy of the afferent information transmitted from the spinal cord to the cerebral cortex, as well as efferent information from the motor centers of the cerebral cortex to the spinal cord. The first signals the current state of the controlled variable, while the second gives an idea of the required final state. By comparing the first and second, the cerebellar cortex can calculate the error, which is reported to the motor centers. So the cerebellum continuously corrects both voluntary and automatic movements.

Although the cerebellum is connected to the cerebral cortex, its activity is not controlled by consciousness..

Cerebellum - Comparative anatomy and evolution

The cerebellum phylogenetically developed in multicellular organisms due to the improvement of voluntary movements and the complication of the body control structure. The interaction of the cerebellum with other parts of the central nervous system allows this part of the brain to provide accurate and coordinated body movements in various external conditions.

In different groups of animals, the cerebellum varies greatly in size and shape. The degree of its development correlates with the degree of complexity of body movements.

The cerebellum is present in representatives of all classes of vertebrates, including cyclostomes, in which it has the form of a transverse plate that spreads over the anterior part of the rhomboid fossa.

The functions of the cerebellum are similar in all classes of vertebrates, including fish, reptiles, birds, and mammals. Even cephalopods have a similar brain formation.

There are significant differences in shape and size in different biological species. For example, the cerebellum of lower vertebrates is connected to the hindbrain by a continuous plate in which fiber bundles are not anatomically distinguished. In mammals, these bundles form three pairs of structures called the cerebellar peduncles. Through the legs of the cerebellum, the connections of the cerebellum with other parts of the central nervous system are carried out.

Cyclostomes and fish

The cerebellum has the largest range of variability among the sensorimotor centers of the brain. It is located at the anterior edge of the hindbrain and can reach enormous sizes, covering the entire brain. Its development depends on several factors. The most obvious is associated with pelagic lifestyle, predation or the ability to swim efficiently in the water column. The cerebellum reaches its greatest development in pelagic sharks. Real furrows and convolutions are formed in it, which are absent in most bony fish. In this case, the development of the cerebellum is caused by the complex movement of sharks in the three-dimensional environment of the world's oceans. The requirements for spatial orientation are too great for it not to affect the neuromorphological provision of the vestibular apparatus and the sensorimotor system. This conclusion is confirmed by the study of the brain of sharks that live near the bottom. The nurse shark does not have a developed cerebellum, and the cavity of the IV ventricle is completely open. Its habitat and way of life does not impose such stringent requirements on spatial orientation as those of the long-winged shark. The result was a relatively modest size of the cerebellum.

The internal structure of the cerebellum in fish differs from that of humans. The cerebellum of fish does not contain deep nuclei, there are no Purkinje cells.

The size and shape of the cerebellum in primary aquatic vertebrates can change not only in connection with a pelagic or relatively sedentary lifestyle. Since the cerebellum is the center of somatic sensitivity analysis, it takes an active part in the processing of electroreceptor signals. Very many primary aquatic vertebrates possess electroreception. In all fish with electroreception, the cerebellum is extremely well developed. If the electroreception of one's own electromagnetic field or external electromagnetic fields becomes the main afferent system, then the cerebellum begins to play the role of a sensory and motor center. Their cerebellum is often so large that it covers the entire brain from the dorsal surface.

Many vertebrate species have areas of the brain that are similar to the cerebellum in terms of cellular cytoarchitectonics and neurochemistry. Most fish and amphibian species have a lateral line organ that senses changes in water pressure. The part of the brain that receives information from this organ, the so-called octavolateral nucleus, has a structure similar to the cerebellum.

Amphibians and reptiles

In amphibians, the cerebellum is very poorly developed and consists of a narrow transverse plate above the rhomboid fossa. In reptiles, an increase in the size of the cerebellum is noted, which has an evolutionary justification. A suitable environment for the formation of the nervous system in reptiles could be giant coal blockages, consisting mainly of club mosses, horsetails and ferns. In such multi-meter blockages from rotten or hollow tree trunks, ideal conditions could have developed for the evolution of reptiles. Modern deposits of coal directly indicate that such blockages from tree trunks were very widespread and could become a large-scale transitional environment for amphibians to reptiles. In order to take advantage of the biological benefits of tree blockages, it was necessary to acquire several specific qualities. First, it was necessary to learn how to navigate well in a three-dimensional environment. For amphibians, this is not an easy task, since their cerebellum is very small. Even specialized tree frogs, which are a dead-end evolutionary branch, have a much smaller cerebellum than reptiles. In reptiles, neuronal interconnections are formed between the cerebellum and the cerebral cortex.

The cerebellum in snakes and lizards, as well as in amphibians, is located in the form of a narrow vertical plate above the anterior edge of the rhomboid fossa; in turtles and crocodiles it is much wider. At the same time, in crocodiles, its middle part differs in size and bulge.

Birds

The cerebellum of birds consists of a larger middle part and two small lateral appendages. It completely covers the rhomboid fossa. The middle part of the cerebellum is divided by transverse grooves into numerous leaflets. The ratio of the mass of the cerebellum to the mass of the entire brain is the highest in birds. This is due to the need for fast and accurate coordination of movements in flight.

In birds, the cerebellum consists of a massive middle part, usually crossed by 9 convolutions, and two small lobes, which are homologous to a piece of the cerebellum of mammals, including humans. Birds are characterized by a high perfection of the vestibular apparatus and the system of coordination of movements. The result of the intensive development of the coordination sensorimotor centers was the appearance of a large cerebellum with real folds - furrows and convolutions. The avian cerebellum was the first vertebrate brain structure to have a cortex and a folded structure. Complex movements in a three-dimensional environment became the reason for the development of the cerebellum of birds as a sensorimotor center for coordinating movements.

mammals

A distinctive feature of the mammalian cerebellum is the enlargement of the lateral parts of the cerebellum, which mainly interact with the cerebral cortex. In the context of evolution, the enlargement of the lateral parts of the cerebellum occurs together with the enlargement of the frontal lobes of the cerebral cortex.

In mammals, the cerebellum consists of a vermis and paired hemispheres. Mammals are also characterized by an increase in the surface area of the cerebellum due to the formation of furrows and folds.

In monotremes, as in birds, the middle section of the cerebellum predominates over the lateral ones, which are located in the form of insignificant appendages. In marsupials, edentulous, bats and rodents, the middle section is not inferior to the lateral ones. Only in carnivores and ungulates do the lateral parts become larger than the middle section, forming the cerebellar hemispheres. In primates, the middle section, in comparison with the hemispheres, is already very undeveloped.

The predecessors of man and lat. Homo sapiens of the Pleistocene time, the increase in the frontal lobes occurred at a faster rate compared to the cerebellum.

Cerebellum - Human Cerebellum Anatomy

A feature of the human cerebellum is that it, like the brain, consists of the right and left hemispheres and the unpaired structure connecting them - the "worm". The cerebellum occupies almost the entire posterior cranial fossa. The diameter of the cerebellum is much larger than its anteroposterior size.

The mass of the cerebellum in an adult ranges from 120 to 160 g. By the time of birth, the cerebellum is less developed than the cerebral hemispheres, but in the first year of life it develops faster than other parts of the brain. A pronounced increase in the cerebellum is noted between the 5th and 11th months of life, when the child learns to sit and walk. The mass of the cerebellum of a newborn is about 20 g, at 3 months it doubles, at 5 months it increases 3 times, at the end of the 9th month - 4 times. Then the cerebellum grows more slowly, and by the age of 6 its mass reaches the lower limit of the norm for an adult - 120 g.

Above the cerebellum lie the occipital lobes of the cerebral hemispheres. The cerebellum is separated from the cerebrum by a deep fissure, into which a process of the dura mater of the brain is wedged - the cerebellum, stretched over the posterior cranial fossa. Anterior to the cerebellum is the pons and medulla oblongata.

The cerebellar vermis is shorter than the hemispheres, therefore notches are formed on the corresponding edges of the cerebellum: on the anterior edge - anterior, on the posterior edge - posterior. The most protruding sections of the anterior and posterior edges form the corresponding anterior and posterior angles, and the most prominent lateral sections form the lateral angles.

A horizontal fissure running from the middle cerebellar peduncles to the posterior notch of the cerebellum divides each hemisphere of the cerebellum into two surfaces: an upper one, relatively flat and obliquely descending to the edges, and a convex lower one. With its lower surface, the cerebellum is adjacent to the medulla oblongata, so that the latter is pressed into the cerebellum, forming an invagination - the valley of the cerebellum, at the bottom of which the worm is located.

On the cerebellar vermis, the upper and lower surfaces are distinguished. Grooves running longitudinally along the sides of the worm: on the anterior surface - smaller, on the back - deeper - separate it from the cerebellar hemispheres.

The cerebellum consists of gray and white matter. The gray matter of the hemispheres and the cerebellar vermis, located in the surface layer, forms the cerebellar cortex, and the accumulation of gray matter in the depths of the cerebellum forms the cerebellar nucleus. White matter - the brain body of the cerebellum, lies in the thickness of the cerebellum and, through three pairs of cerebellar peduncles, connects the gray matter of the cerebellum with the brain stem and spinal cord.

Worm

The cerebellar vermis governs posture, tone, supportive movement, and body balance. Worm dysfunction in humans manifests itself in the form of static-locomotor ataxia.

Slices

The surfaces of the hemispheres and the cerebellar vermis are divided by more or less deep cerebellar fissures into numerous arcuately curved cerebellar sheets of various sizes, most of which are located almost parallel to one another. The depth of these furrows does not exceed 2.5 cm. If it were possible to straighten the leaves of the cerebellum, then the area of its cortex would be 17 x 120 cm. Groups of convolutions form separate lobules of the cerebellum. The lobules of the same name in both hemispheres are delimited by the same groove, which passes through the worm from one hemisphere to the other, as a result of which two - right and left - lobules of the same name in both hemispheres correspond to a certain lobule of the worm.

Individual lobules form the lobes of the cerebellum. There are three such shares: anterior, posterior and flocculent-nodular.

The worm and hemispheres are covered with gray matter, inside of which is white matter. The white matter, branching, penetrates into each gyrus in the form of white stripes. On sagittal sections of the cerebellum, a peculiar pattern is visible, called the "tree of life". The subcortical nuclei of the cerebellum lie within the white matter.

10. tree of life cerebellum
11. brain body of the cerebellum
12. white stripes
13. cerebellar cortex
18. dentate nucleus
19. gate of the dentate nucleus
20. corky nucleus
21. globular nucleus
22. tent core

The cerebellum is connected to neighboring brain structures by means of three pairs of legs. The cerebellar peduncles are a system of pathways, the fibers of which follow to and from the cerebellum:

The inferior cerebellar peduncles run from the medulla oblongata to the cerebellum.
Middle cerebellar peduncles - from the pons to the cerebellum.
The superior cerebellar peduncles lead to the midbrain.

Nuclei

The nuclei of the cerebellum are paired accumulations of gray matter, which lie in the thickness of the white, closer to the middle, that is, the cerebellar vermis. There are the following cores:

the dentate lies in the medial-lower areas of the white matter. This nucleus is a wave-like curving plate of gray matter with a small break in the medial section, which is called the gate of the dentate nucleus. The jagged kernel is similar to the kernel of an olive. This similarity is not accidental, since both nuclei are connected by conductive pathways, olive-cerebellar fibers, and each gyrus of one nucleus is similar to the gyrus of the other.
cork is located medially and parallel to the dentate nucleus.
the spherical lies somewhat medially to the cork-like nucleus and can be presented in the form of several small balls on the cut.
the core of the tent is localized in the white matter of the worm, on both sides of its median plane, under the uvula lobule and the central lobule, in the roof of the fourth ventricle.

The nucleus of the tent, being the most medial, is located on the sides of the midline in the area where the tent protrudes into the cerebellum. Lateral to it are the spherical, corky, and dentate nuclei, respectively. These nuclei have different phylogenetic ages: nucleus fastigii belongs to the most ancient part of the cerebellum, associated with the vestibular apparatus; nuclei emboliformis et globosus - to the old part, which arose in connection with the movements of the body, and the nucleus dentatus - to the youngest, which developed in connection with movement with the help of the limbs. Therefore, with the defeat of each of these parts, various aspects of the motor function are disturbed, corresponding to different stages of phylogenesis, namely: with damage to the archicerebellum, the balance of the body is disturbed;

The nucleus of the tent is located in the white matter of the "worm", the remaining nuclei lie in the hemispheres of the cerebellum. Almost all information leaving the cerebellum is switched to its nuclei.

blood supply

arteries

Three large paired arteries originate from the vertebral and basilar arteries, delivering blood to the cerebellum:

superior cerebellar artery;
anterior inferior cerebellar artery;
posterior inferior cerebellar artery.

The cerebellar arteries pass along the crests of the gyri of the cerebellum without forming a loop in its grooves, as do the arteries of the cerebral hemispheres. Instead, small vascular branches extend from them into almost every groove.

Superior cerebellar artery

It arises from the upper part of the basilar artery at the border of the bridge and the brain stem before its division into the posterior cerebral arteries. The artery goes below the trunk of the oculomotor nerve, bends around the anterior cerebellar peduncle from above and, at the level of the quadrigemina, under the notch, makes a right angle turn back, branching on the upper surface of the cerebellum. Branches branch off from the artery and supply blood to:

lower colliculi of the quadrigemina;
superior cerebellar peduncles;
dentate nucleus of the cerebellum;
upper sections of the vermis and cerebellar hemispheres.

The initial parts of the branches that supply blood to the upper parts of the worm and its surrounding areas can be located within the posterior part of the notch of the cerebellum, depending on the individual size of the tentorial foramen and the degree of physiological protrusion of the worm into it. Then they cross the edge of the cerebellum and go to the dorsal and lateral parts of the upper hemispheres. This topographic feature makes the vessels vulnerable to possible compression by the most eminent part of the vermis when the cerebellum is wedged into the posterior part of the tentorial foramen. The result of such compression is partial and even complete heart attacks of the cortex of the upper hemispheres and the cerebellar vermis.

The branches of the superior cerebellar artery anastomose widely with the branches of both inferior cerebellar arteries.

Anterior inferior cerebellar artery

Departs from the initial part of the basilar artery. In most cases, the artery runs along the lower edge of the pons in an arc, convex downwards. The main trunk of the artery is most often located anterior to the root of the abducens nerve, goes outward and passes between the roots of the facial and vestibulocochlear nerves. Further, the artery goes around the top of the patch and branches on the anteroinferior surface of the cerebellum. In the region of the shred, two loops formed by the cerebellar arteries can often be located: one is the posterior lower, the other is the anterior lower.

The anterior inferior cerebellar artery, passing between the roots of the facial and vestibulocochlear nerves, gives off the labyrinth artery, which goes to the internal auditory meatus and, together with the auditory nerve, enters the inner ear. In other cases, the labyrinth artery departs from the basilar artery. The terminal branches of the anterior inferior cerebellar artery feed the roots of the VII-VIII nerves, the middle cerebellar peduncle, the tuft, the anteroinferior sections of the cerebellar cortex, and the choroid plexus of the IV ventricle.

The anterior villous branch of the IV ventricle departs from the artery at the level of the flocculus and enters the plexus through the lateral aperture.

Thus, the anterior inferior cerebellar artery supplies blood to:

inner ear;
roots of the facial and vestibulocochlear nerves;
middle cerebellar peduncle;
shred-nodular lobule;
choroid plexus of the IV ventricle.

The zone of their blood supply in comparison with the rest of the cerebellar arteries is the smallest.

Posterior inferior cerebellar artery

Departs from the vertebral artery at the level of the chiasm of the pyramids or at the lower edge of the olive. The diameter of the main trunk of the posterior inferior cerebellar artery is 1.5–2 mm. The artery bends around the olive, rises, makes a turn and passes between the roots of the glossopharyngeal and vagus nerves, forming loops, then descends down between the inferior cerebellar peduncle and the inner surface of the tonsil. Then the artery turns outward and passes to the cerebellum, where it diverges into internal and external branches, the first of which rises along the worm, and the second goes to the lower surface of the cerebellar hemisphere.

An artery can form up to three loops. The first loop, directed downwards with a bulge, is formed in the region of the groove between the pons and the pyramid, the second loop with a bulge upwards is on the lower cerebellar peduncle, the third loop, directed downwards, lies on the inner surface of the tonsil. Branches from the trunk of the posterior inferior cerebellar artery to:

ventrolateral surface of the medulla oblongata. The defeat of these branches causes the development of the Wallenberg-Zakharchenko syndrome;
tonsil;
lower surface of the cerebellum and its nuclei;
roots of the glossopharyngeal and vagus nerves;
choroid plexus of the IV ventricle through its median aperture in the form of the posterior villous branch of the IV ventricle).

Vienna

Cerebellar veins form a wide network on its surface. They anastomose with the veins of the cerebrum, brainstem, spinal cord and flow into the nearby sinuses.

The superior vein of the cerebellar vermis collects blood from the superior vermis and adjacent sections of the cortex of the upper surface of the cerebellum and flows above the quadrigemina into the great cerebral vein from below.

The inferior vein of the cerebellar vermis receives blood from the inferior vermis, the inferior surface of the cerebellum, and the tonsil. The vein goes backwards and up along the groove between the hemispheres of the cerebellum and flows into the direct sinus, less often into the transverse sinus or into the sinus drain.

The superior cerebellar veins run along the upper lateral surface of the brain and empty into the transverse sinus.

The inferior cerebellar veins, which collect blood from the inferior lateral surface of the cerebellar hemispheres, drain into the sigmoid sinus and superior petrosal vein.

Cerebellum - Neurophysiology

The cerebellum is a functional offshoot of the main cortex-spinal cord axis. On the one hand, sensory feedback closes in it, that is, it receives a copy of the afferentation, on the other hand, a copy of the efferentation from the motor centers also comes here. Technically speaking, the first signalizes the current state of the controlled variable, while the second gives an idea of the required final state. By comparing the first and second, the cerebellar cortex can calculate the error, which is reported to the motor centers. So the cerebellum continuously corrects both intentional and automatic movements. In lower vertebrates, information also enters the cerebellum from the acoustic region, in which sensations related to balance are recorded, supplied by the ear and the lateral line, and in some even from the organ of smell.

Phylogenetically, the most ancient part of the cerebellum consists of a tuft and a nodule. Vestibular inputs predominate here. In evolutionary terms, the structures of the archcerebellum arise in the class of cyclostomes in lampreys, in the form of a transverse plate that spreads over the anterior part of the rhomboid fossa. In lower vertebrates, the archicerebellum is represented by paired ear-shaped parts. In the process of evolution, a decrease in the size of the structures of the ancient part of the cerebellum is noted. Archicerebellum is the most important component of the vestibular apparatus.

The "old" structures in humans also include the region of the vermis in the anterior lobe of the cerebellum, the pyramid, the uvula of the worm, and the peritoneum. The paleocerebellum receives signals mainly from the spinal cord. Paleocerebellum structures appear in fish and are present in other vertebrates.

The medial elements of the cerebellum project to the nucleus of the tent, as well as to the spherical and corky nuclei, which in turn form connections mainly with the stem motor centers. Deiters' nucleus, the vestibular motor center, also receives signals directly from the vermis and from the flocculonodular lobe.

Damage to the archi- and paleocerebellum lead primarily to imbalances, as in the pathology of the vestibular apparatus. A person is manifested by dizziness, nausea and vomiting. Oculomotor disorders in the form of nystagmus are also typical. It is difficult for patients to stand and walk, especially in the dark, for this they have to grab onto something with their hands; gait becomes staggering, as if in a state of intoxication.

Signals go to the lateral elements of the cerebellum mainly from the cortex of the cerebral hemispheres through the nuclei of the pons and inferior olive. The Purkinje cells of the cerebellar hemispheres project through the lateral dentate nuclei to the motor nuclei of the thalamus and further to the motor areas of the cerebral cortex. Through these two inputs, the cerebellar hemisphere receives information from the cortical areas that are activated in the phase of preparation for movement, that is, participating in its “programming”. Neocerebellum structures are found only in mammals. At the same time, in humans, in connection with upright walking, improvement of hand movements, they have reached the greatest development in comparison with other animals.

Thus, part of the impulses that have arisen in the cerebral cortex reaches the opposite hemisphere of the cerebellum, bringing information not about the produced, but only about the active movement planned for execution. Having received such information, the cerebellum immediately sends out impulses that correct voluntary movement, mainly by extinguishing inertia and the most rational regulation of the muscle tone of agonists and antagonists. As a result, the clarity and refinement of voluntary movements are ensured, and any inappropriate components are eliminated.

Functional plasticity, motor adaptation and motor learning

The role of the cerebellum in motor adaptation has been demonstrated experimentally. If vision is impaired, the vestibulo-ocular reflex of compensatory eye movement when turning the head will no longer correspond to the visual information received by the brain. A subject wearing prism glasses initially finds it very difficult to move correctly in the environment, but after a few days he adjusts to the anomalous visual information. At the same time, clear quantitative changes in the vestibulo-ocular reflex and its long-term adaptation were noted. Experiments with the destruction of nervous structures have shown that such motor adaptation is impossible without the participation of the cerebellum. The plasticity of cerebellar function and motor learning and the determination of their neuronal mechanisms have been described by David Marr and James Albus.

The plasticity of the function of the cerebellum is also responsible for motor learning and the development of stereotyped movements, such as writing, typing on the keyboard, etc.

Although the cerebellum is connected to the cerebral cortex, its activity is not controlled by consciousness.

Functions

The functions of the cerebellum are similar in various species, including humans. This is confirmed by their disturbance in case of damage to the cerebellum in the experiment in animals and the results of clinical observations in diseases affecting the cerebellum in humans. The cerebellum is a brain center that is extremely important for coordinating and regulating motor activity and maintaining posture. The cerebellum works mainly reflexively, maintaining the balance of the body and its orientation in space. It also plays an important role in locomotion.

Accordingly, the main functions of the cerebellum are:

movement coordination
balance regulation
regulation of muscle tone

Conducting paths

The cerebellum is connected to other parts of the nervous system by numerous pathways that run in the cerebellar peduncles. Distinguish between afferent and efferent pathways. Efferent pathways are present only in the upper legs.

Cerebellar pathways do not cross at all or cross twice. Therefore, with a half lesion of the cerebellum itself or a unilateral lesion of the cerebellar peduncles, the symptoms of the lesion develop on the sides of the lesion.

upper legs

Efferent pathways pass through the superior cerebellar peduncles, with the exception of Govers's afferent pathway.

Anterior spinal-cerebellar tract - the first neuron of this path starts from the proprioreceptors of the muscles, joints, tendons and periosteum and is located in the spinal ganglion. The second neuron is the cells of the posterior horn of the spinal cord, the axon of which passes to the opposite side and rises up in the anterior part of the lateral column, passes the medulla oblongata, the pons, then crosses again and through the upper legs enter the cortex of the cerebellar hemispheres, and then into the dentate nucleus .
The dentate-red path starts from the dentate nucleus and passes through the superior cerebellar peduncles. These paths double-cross and end at red nuclei. The axons of the neurons of the red nuclei form the rubrospinal pathway. After exiting the red nucleus, this path crosses again, descends in the brainstem, as part of the lateral column of the spinal cord, and reaches the α- and γ-motor neurons of the spinal cord.
Cerebellar-thalamic path - goes to the nuclei of the thalamus. Through them, it connects the cerebellum with the extrapyramidal system and the cerebral cortex.
Cerebellar-reticular path - connects the cerebellum with the reticular formation, from which, in turn, the reticular-spinal path begins.
The cerebellar-vestibular path is a special path, since, unlike other pathways that begin in the nuclei of the cerebellum, it is the axons of Purkinje cells heading to the lateral vestibular nucleus of Deiters.

Medium legs

Through the middle cerebellar peduncle are afferent pathways that connect the cerebellum to the cerebral cortex.

The fronto-bridge-cerebellar path starts from the anterior and middle frontal gyri, passes through the anterior thigh of the internal capsule to the opposite side and switches on the cells of the pons varolii, which are the second neuron of this path. From them, it enters the contralateral middle cerebellar peduncle and ends on the Purkinje cells of its hemispheres.
The temporal-bridge-cerebellar path - starts from the cells of the cortex of the temporal lobes of the brain. Otherwise, its course is similar to that of the fronto-bridge-cerebellar path.
Occipital-bridge-cerebellar path - starts from the cells of the cortex of the occipital lobe of the brain. Transmits visual information to the cerebellum.

lower legs

In the lower legs of the cerebellum, afferent pathways run from the spinal cord and brain stem to the cerebellar cortex.

The posterior spinal cord connects the cerebellum with the spinal cord. Conducts impulses from proprioceptors of muscles, joints, tendons and periosteum, which reach the posterior horns of the spinal cord as part of sensory fibers and posterior roots of the spinal nerves. In the posterior horns of the spinal cord, they switch to the so-called. Clark cells, which are the second neuron of deep sensitivity. The axons of Clark cells form the Flexig pathway. They pass in the back of the lateral column on their side and, as part of the lower legs of the cerebellum, reach its cortex.
Olive-cerebellar path - begins in the nucleus of the inferior olive on the opposite side and ends on the Purkinje cells of the cerebellar cortex. The olive-cerebellar path is represented by climbing fibers. The nucleus of the inferior olive receives information directly from the cerebral cortex and thus conducts information from its premotor areas, that is, areas responsible for planning movements.
Vestibulo-cerebellar path - starts from the upper vestibular nucleus of Bekhterev and through the lower legs reaches the cerebellar cortex of the flocculo-nodular region. The information of the vestibulo-cerebellar pathway, having switched on the Purkinje cells, reaches the nucleus of the tent.
Reticulo-cerebellar path - starts from the reticular formation of the brain stem, reaches the cortex of the cerebellar vermis. Connects the cerebellum and the basal ganglia of the extrapyramidal system.

Cerebellum - Symptoms of lesions

Damage to the cerebellum is characterized by disorders of statics and coordination of movements, as well as muscle hypotension. This triad is characteristic of both humans and other vertebrates. At the same time, the symptoms of cerebellar damage are described in most detail for humans, since they are of direct applied importance in medicine.

Damage to the cerebellum, especially its worm, usually leads to a violation of the statics of the body - the ability to maintain a stable position of its center of gravity, which ensures stability. When this function is disturbed, static ataxia occurs. The patient becomes unstable, therefore, in a standing position, he seeks to spread his legs wide, balance with his hands. Especially clearly static ataxia is manifested in the Romberg position. The patient is invited to stand up, tightly moving his feet, slightly raise his head and stretch his arms forward. In the presence of cerebellar disorders, the patient in this position is unstable, his body sways. The patient may fall. In the case of damage to the cerebellar vermis, the patient usually sways from side to side and often falls back, with a pathology of the cerebellar hemisphere, he tends mainly towards the pathological focus. If the static disorder is moderately expressed, it is easier to identify it in a patient in the so-called complicated or sensitized Romberg position. In this case, the patient is invited to put his feet on the same line so that the toe of one foot rests on the heel of the other. The assessment of stability is the same as in the usual Romberg position.

Normally, when a person is standing, the muscles of his legs are tense, with the threat of falling to the side, his leg on this side moves in the same direction, and the other leg comes off the floor. With the defeat of the cerebellum, mainly its worm, the patient's support and jump reactions are disturbed. Violation of the support reaction is manifested by the instability of the patient in a standing position, especially if his legs are closely shifted at the same time. Violation of the jump reaction leads to the fact that if the doctor, standing behind the patient and insuring him, pushes the patient in one direction or another, then the latter falls with a small push.

The gait of a patient with cerebellar pathology is very characteristic and is called "cerebellar". The patient, due to the instability of the body, walks uncertainly, spreading his legs wide, while he is “thrown” from side to side, and if the hemisphere of the cerebellum is damaged, it deviates when walking from a given direction towards the pathological focus. The instability is especially pronounced when cornering. During walking, the human torso is excessively straightened. The gait of a patient with a cerebellar lesion is in many ways reminiscent of the gait of a drunk person.

If static ataxia is pronounced, then patients completely lose the ability to control their body and cannot not only walk and stand, but even sit.

Predominant lesion of the cerebellar hemispheres leads to a breakdown of its counter-inertial influences and, in particular, to the occurrence of dynamic ataxia. It is manifested by the awkwardness of the movements of the limbs, which is especially pronounced with movements that require precision. To identify dynamic ataxia, a number of coordination tests are performed.

Muscular hypotension is detected with passive movements made by the examiner in various joints of the patient's limbs. Damage to the cerebellar vermis usually leads to diffuse muscle hypotension, while with damage to the cerebellar hemisphere, a decrease in muscle tone is noted on the side of the pathological focus.

Pendulum reflexes are also due to hypotension. When examining the knee reflex in a sitting position with legs hanging freely from the couch after a blow with a hammer, several “swinging” movements of the lower leg are observed.

Asynergia is the loss of physiological synergistic movements during complex motor acts.

The most common asynergy tests are:

The patient, standing with shifted legs, is offered to bend over backwards. Normally, simultaneously with the tilting of the head, the legs synergistically bend at the knee joints, which allows maintaining the stability of the body. With cerebellar pathology, there is no friendly movement in the knee joints and, throwing his head back, the patient immediately loses his balance and falls in the same direction.
The patient, standing with his legs shifted, is invited to lean on the palms of the doctor, who then suddenly removes them. If the patient has cerebellar asynergy, he falls forward. Normally, there is a slight deviation of the body back or the person remains motionless.
The patient, lying on his back on a hard bed without a pillow, with his legs spread apart to the width of the shoulder girdle, is offered to cross his arms over his chest and then sit down. Due to the absence of friendly contractions of the gluteal muscles, a patient with cerebellar pathology cannot fix the legs and pelvis to the support area, as a result, he cannot sit down, while the patient's legs, breaking away from the bed, rise up.

Cerebellum - Pathology

Cerebellar lesions occur in a wide range of diseases. Based on the ICD-10 data, the cerebellum is directly affected in the following pathologies:

Neoplasms

Cerebellar neoplasms are most commonly represented by medulloblastomas, astrocytomas, and hemangioblastomas.

Abscess

Cerebellar abscesses account for 29% of all brain abscesses. They are localized more often in the cerebellar hemispheres at a depth of 1-2 cm. They are small in size, round or oval in shape.

There are metastatic and contact abscesses of the cerebellum. Metastatic abscesses are rare; develop as a result of purulent diseases of distant parts of the body. Sometimes the source of the infection cannot be identified.

Contact abscesses of otogenic origin are more common. The ways of infection in them are either the bone canals of the temporal bone or the vessels that drain blood from the middle and inner ear.

hereditary diseases

A group of hereditary diseases is accompanied by the development of ataxia.

In some of them, a predominant lesion of the cerebellum is noted.

Hereditary cerebellar ataxia of Pierre Marie

Hereditary degenerative disease with a primary lesion of the cerebellum and its pathways. The mode of inheritance is autosomal dominant.

With this disease, a degenerative lesion of the cells of the cortex and nuclei of the cerebellum, spinocerebellar tracts in the lateral cords of the spinal cord, in the nuclei of the bridge and the medulla oblongata is determined.

Olivopontocerebellar degenerations

A group of hereditary diseases of the nervous system characterized by degenerative changes in the cerebellum, the nuclei of the inferior olives and the pons of the brain, in rare cases - the nuclei of the cranial nerves of the caudal group, to a lesser extent - damage to the pathways and cells of the anterior horns of the spinal cord, basal ganglia. Diseases differ in the type of inheritance and a different combination of clinical symptoms.

Alcoholic cerebellar degeneration

Alcoholic cerebellar degeneration is one of the most common complications of alcohol abuse. It develops more often in the 5th decade of life after many years of ethanol abuse. It is caused both by the direct toxic effect of alcohol, and by electrolyte disturbances caused by alcoholism. Severe atrophy of the anterior lobes and the upper part of the cerebellar vermis develops. In the affected areas, an almost complete loss of neurons is revealed in both the granular and molecular layers of the cerebellar cortex. In advanced cases, the dentate nuclei may also be involved.

Multiple sclerosis

Multiple sclerosis is a chronic demyelinating disease. With it, there is a multifocal lesion of the white matter of the central nervous system.

Morphologically, the pathological process in multiple sclerosis is characterized by numerous changes in the brain and spinal cord. The favorite localization of the foci is the periventricular white matter, the lateral and posterior cords of the cervical and thoracic spinal cord, the cerebellum and the brain stem.

Cerebral circulation disorders

Hemorrhage in the cerebellum

Cerebral cerebrovascular accidents can be either ischemic or hemorrhagic.

Cerebellar infarction occurs when blockage of the vertebral, basilar or cerebellar arteries and, with extensive damage, is accompanied by severe cerebral symptoms, impaired consciousness. Blockage of the anterior inferior cerebellar artery leads to a heart attack in the cerebellum and pons, which can cause dizziness, tinnitus, nausea on the side of the lesion - paresis of facial muscles, cerebellar ataxia, Horner's syndrome. When blockage of the superior cerebellar artery often occurs dizziness, cerebellar ataxia on the side of the focus.

Hemorrhage in the cerebellum is usually manifested by dizziness, nausea and repeated vomiting while maintaining consciousness. Patients often suffer from headache in the occipital region, they usually have nystagmus and ataxia in the extremities. In the event of a cerebellar-tentorial displacement or wedging of the cerebellar tonsils into the foramen magnum, a disturbance of consciousness develops up to coma, hemi- or tetraparesis, lesions of the facial and abducens nerves.

Traumatic brain injury

Cerebellar contusions dominate among lesions of the formations of the posterior cranial fossa. Focal lesions of the cerebellum are usually caused by an impact mechanism of injury, as evidenced by frequent fractures of the occipital bone below the transverse sinus.

Cerebral symptoms in cerebellar injuries often have an occlusive color due to the proximity to the CSF outflow pathways from the brain.

Among the focal symptoms of cerebellar contusion, unilateral or bilateral muscular hypotension, coordination disorders, and large tonic spontaneous nystagmus dominate. Characterized by localization of pain in the occipital region with irradiation to other areas of the head. Often, one or another symptomatology from the side of the brain stem and cranial nerves manifests itself simultaneously. With severe damage to the cerebellum, respiratory disorders, hormetonia, and other life-threatening conditions occur.

Due to the limited subtentorial space, even with a relatively small amount of damage to the cerebellum, dislocation syndromes often unfold with infringement of the medulla oblongata by the cerebellar tonsils at the level of the occipital-cervical dural funnel or infringement of the midbrain at the level of the tenon due to the upper parts of the cerebellum being displaced from bottom to top.

Malformations

MRI. Arnold's syndrome - Chiari I. The arrow indicates the protrusion of the tonsils of the cerebellum into the lumen of the spinal canal

Cerebellar malformations include several diseases.

Allocate total and subtotal agenesis of the cerebellum. Total agenesis of the cerebellum is rare, combined with other severe anomalies in the development of the nervous system. Most often, subtotal agenesis is observed, combined with malformations of other parts of the brain. Hypoplasia of the cerebellum occurs, as a rule, in two variants: a decrease in the entire cerebellum and hypoplasia of individual parts while maintaining the normal structure of its remaining departments. They can be unilateral or bilateral, as well as lobar, lobular and intracortical. There are various changes in the configuration of the sheets - allogyria, polygyria, agyria.

Dandy-Walker Syndrome

Dandy-Walker syndrome is characterized by a combination of cystic enlargement of the fourth ventricle, total or partial aplasia of the cerebellar vermis, and supratentorial hydrocephalus.

Arnold-Chiari Syndrome

Arnold-Chiari syndrome includes 4 types of diseases, designated Arnold-Chiari syndrome I, II, III and IV, respectively.

Arnold-Chiari I syndrome - descent of the cerebellar tonsils more than 5 mm beyond the foramen magnum into the spinal canal.

Arnold-Chiari II syndrome - descent into the spinal canal of the structures of the cerebellum and brain stem, myelomeningocele and hydrocephalus.

Arnold-Chiari III syndrome - occipital encephalocele in combination with signs of Arnold-Chiari II syndrome.

Arnold-Chiari IV syndrome - aplasia or hypoplasia of the cerebellum.

Goals:

reveal the features of the nervous system of vertebrates, its role in the regulation of vital processes and their relationship with the environment;
to develop the ability of students to distinguish classes of animals, arrange them in order of complexity in the process of evolution.

Equipment and equipment of the lesson:

Program and textbook by N.I. Sonin “Biology. Living organism". 6th grade.
Handout - a table-grid "Departments of the brain of vertebrates."
Vertebrate brain models.
Inscriptions (names of classes of animals).
Drawings depicting representatives of these classes.

During the classes.

I. Organizational moment.

II. Repetition of homework (frontal survey):

What systems regulate the activity of the animal organism?
What is irritability or sensitivity?
What is a reflex?
What are reflexes?
What are these reflexes?
a) saliva is produced by the smell of food?
b) does the person turn on the light despite the absence of a light bulb?
c) Does the cat run to the sound of the refrigerator door opening?
d) does the dog yawn?
What is the nervous system of a hydra?
How is the nervous system of an earthworm arranged?

III. New material:

(? - questions asked to the class during the explanation)

We are studying now Section 17, what is it called?
Coordination and regulation of what?
What animals did we talk about in class?
Are they invertebrates or vertebrates?
What groups of animals do you see on the board?

Today in the lesson we will study the regulation of the life processes of vertebrates.

Topic:“Regulation in vertebrates(write in notebook).

Our goal will be to consider the structure of the nervous system of different vertebrates. At the end of the lesson, we will be able to answer the following questions:

How is the behavior of animals related to the structure of the nervous system?
Why is it easier to train a dog than a bird or a lizard?
Why do doves in the air can roll over during the flight?

During the lesson, we will fill in the table, so everyone has a piece of paper with a table on their desk.

Where is the nervous system located in annelids and insects?

In vertebrates, the nervous system is located on the dorsal side of the body. It consists of the brain, spinal cord and nerves.

? 1) Where is the spinal cord located?

2) Where is the brain located?

It distinguishes between the anterior, middle, hindbrain and some other departments. In different animals, these departments are developed in different ways. This is due to their lifestyle and the level of their organization.

Now we will listen to reports on the structure of the nervous system of different classes of vertebrates. And you make notes in the table: does this group of animals have this part of the brain or not, how developed is it compared to other animals? After filling out the table remains with you.

(The table must be printed in advance according to the number of students in the class)

Animal classes	Sections of the brain
Animal classes	Front	Average	Intermediate	Cerebellum	Oblong
Fish (bone, cartilage)
Amphibians
reptiles
Birds
mammals

Table. Parts of the brain of vertebrates.

Before the lesson, inscriptions and drawings are attached to the board. During the answers, students hold models of the brain of vertebrates in their hands and show the departments they are talking about. After each answer, the model is placed on a demonstration table near the board under the inscription and drawing of the corresponding group of animals. It turns out something like this scheme ...

Scheme:

1. Fish.

Spinal cord. The central nervous system of fish, like that of the lancelet, has the form of a tube. Its posterior section - the spinal cord - is located in the spinal canal, formed by the upper bodies and arches of the vertebrae. From the spinal cord, between each pair of vertebrae, nerves depart to the right and left, which control the work of the muscles of the body and the fins and organs located in the body cavity.

The nerves from the sensory cells on the body of the fish send signals of irritation to the spinal cord.

Brain. The anterior part of the neural tube of fish and other vertebrates is modified into a brain, protected by the bones of the cranium. In the brain of vertebrates, departments are distinguished: forebrain, diencephalon, midbrain, cerebellum and medulla oblongata. All these parts of the brain are of great importance in the life of the fish. For example, the cerebellum controls the coordination of movement and balance of the animal. The medulla oblongata gradually passes into the spinal cord. It plays a large role in controlling respiration, circulation, digestion and other essential bodily functions.

! Let's see what you wrote down?

2. Amphibians and reptiles.

The central nervous system and sense organs of amphibians consist of the same departments as those of fish. The forebrain is more developed than in fish, and two swellings can be distinguished in it - large hemispheres. The body of amphibians is close to the ground, and they do not have to maintain balance. In connection with this, the cerebellum, which controls the coordination of movements, is less developed in them than in fish. The nervous system of the lizard is similar in structure to the corresponding systems of amphibians. In the brain, the cerebellum, which is in charge of balance and coordination of movements, is more developed than in amphibians, which is associated with greater mobility of the lizard and a significant variety of its movements.

3. Birds.

Nervous system. The optic tubercles of the midbrain are well developed in the brain. The cerebellum is much larger than in other vertebrates, as it is the center of coordination and coordination of movements, and birds in flight make very complex movements.

Compared with fish, amphibians and reptiles, birds have enlarged forebrain hemispheres.

4. Mammals.

The mammalian brain consists of the same sections as those of other vertebrates. However, the large hemispheres of the forebrain have a more complex structure. The outer layer of the cerebral hemispheres consists of nerve cells that form the cerebral cortex. In many mammals, including the dog, the cerebral cortex is so enlarged that it does not lie in an even layer, but forms folds - convolutions. The more nerve cells in the cerebral cortex, the more it is developed, the more convolutions in it. If the cerebral cortex is removed from the experimental dog, then the animal retains its innate instincts, but conditioned reflexes are never formed.

The cerebellum is well developed and, like the cerebral hemispheres, has many convolutions. The development of the cerebellum is associated with the coordination of complex movements in mammals.

Conclusion on the table (questions to the class):

What parts of the brain do all classes of animals have?
Which animals will have the most developed cerebellum?
Forebrain?
Which have a cortex on the hemispheres?
Why is the cerebellum less developed in frogs than in fish?

Now consider the structure of the sense organs of these animals, their behavior, in connection with such a structure of the nervous system (tell the same students who talked about the structure of the brain):

1. Fish.

The sense organs allow fish to navigate well in the environment. The eyes play an important role in this. The perch sees only at a relatively close distance, but distinguishes the shape and color of objects.

In front of each eye of a perch, two nostril openings are placed, leading to a blind sac with sensitive cells. This is the organ of smell.

The organs of hearing are not visible from the outside, they are placed on the right and left of the skull, in the bones of its back. Due to the density of water, sound waves are well transmitted through the bones of the skull and are perceived by the fish's hearing organs. Experiments have shown that fish can hear the steps of a person walking along the shore, the ringing of a bell, a shot.

Taste organs are sensitive cells. They are located in the perch, like other fish, not only in the oral cavity, but are also scattered over the entire surface of the body. There are also tactile cells. Some fish (for example, catfish, carp, cod) have tactile antennae on their heads.

Fish have a special sense organ - lateral line. A series of holes are visible outside the body. These holes are connected to a channel located in the skin. The canal contains sensory cells connected to a nerve running under the skin.

The lateral line senses the direction and strength of the water current. Thanks to the lateral line, even a blinded fish does not run into obstacles and is able to catch moving prey.

? Why can't you talk loudly while fishing?

2. Amphibians.

The structure of the sense organs corresponds to the terrestrial environment. For example, by blinking its eyelids, the frog removes dust particles adhering to the eye and moistens the surface of the eye. Like fish, frogs have an inner ear. However, sound waves travel much worse in air than in water. Therefore, for better hearing, the frog has also developed middle ear. It begins with the sound-perceiving eardrum - a thin round film behind the eye. From her sound vibrations through auditory ossicle transmitted to the inner ear.

When hunting, sight plays a major role. Noticing any insect or other small animal, the frog throws out a wide sticky tongue from its mouth, to which the victim sticks. Frogs grab only moving prey.

The hind legs are much longer and stronger than the front legs, they play a major role in movement. The sitting frog rests on slightly bent forelimbs, while the hind limbs are folded and located on the sides of the body. Quickly straightening them, the frog makes a jump. The front legs at the same time protect the animal from hitting the ground. The frog swims, pulling and straightening the hind limbs, while pressing the front to the body.

? How do frogs move in water and on land?

3. Birds.

Sense organs. Vision is best developed - when moving quickly in the air, only with the help of the eyes can one assess the situation from a distance. The sensitivity of the eyes is very high. In some birds, it is 100 times greater than in humans. In addition, birds can clearly see objects that are far away, and distinguish details that are only a few centimeters from the eye. Birds have color vision, better developed than other animals. They distinguish not only primary colors, but also their shades, combinations.

Birds hear well, but their sense of smell is weak.

The behavior of birds is very complex. True, many of their actions are innate, instinctive. Such, for example, are the behavioral features associated with reproduction: pair formation, nest building, incubation. However, during the life of birds, more and more conditioned reflexes appear. For example, young chicks are often not afraid of humans at all, and with age they begin to treat people with caution. Moreover, many learn to determine the degree of danger: they are little afraid of the unarmed, and they fly away from a man with a gun. Domestic and tame birds quickly get used to recognizing the person who feeds them. Trained birds are able to perform various tricks at the direction of the trainer, and some (for example, parrots, lanes, crows) learn to repeat various words of human speech quite clearly.

4. Mammals.

Sense organs. Mammals have a developed sense of smell, hearing, sight, touch and taste, but the degree of development of each of these senses in different species is not the same and depends on the lifestyle and habitat. So, a mole living in the complete darkness of underground passages has underdeveloped eyes. Dolphins and whales almost do not distinguish smells. Most land mammals have a very sensitive sense of smell. Predators, including the dog, it helps to find prey on the trail; herbivores at a great distance can smell a creeping enemy; Animals smell each other. Hearing in most mammals is also well developed. This is facilitated by sound-catching auricles, which are mobile in many animals. Those animals that are active at night have especially delicate hearing. Vision is less important for mammals than for birds. Not all animals distinguish colors. The same gamut of colors that a person sees only monkeys.

The organs of touch are special long and stiff hair (the so-called "whiskers"). Most of them are located near the nose and eyes. Bringing their head closer to the object under study, mammals simultaneously sniff, examine and touch it. In monkeys, like in humans, the main organs of touch are the fingertips. The taste is especially developed in herbivores, which, thanks to this, easily distinguish edible plants from poisonous ones.
The behavior of mammals is no less complex than that of birds. Along with complex instincts, it is largely determined by higher nervous activity, based on the formation of conditioned reflexes during life. Conditioned reflexes are developed especially easily and quickly in species with a well-developed cerebral cortex.

From the first days of life, young mammals recognize their mother. As they grow, their personal experience in dealing with the environment is continuously enriched. The games of young animals (fighting, mutual pursuit, jumping, running) serve as good training for them and contribute to the development of individual methods of attack and defense. Such games are typical only for mammals.

Due to the fact that the environment is extremely changeable, new conditioned reflexes are constantly developed in mammals, and those that are not reinforced by conditioned stimuli are lost. This feature allows mammals to quickly and very well adapt to environmental conditions.

?What animals are the easiest to train? Why?

Cerebellum(lat. cerebellum- literally "small brain") - the part of the brain of vertebrates responsible for the coordination of movements, the regulation of balance and muscle tone. In humans, it is located behind the pons, under the occipital lobes of the brain. Through three pairs of legs, the cerebellum receives information from the cerebral cortex, basal ganglia, brain stem and. Relationships with other parts of the brain may vary in different taxa of vertebrates.

In vertebrates that possess a cortex, the cerebellum is a functional offshoot of the main "cortex-spinal cord" axis. The cerebellum receives a copy of the afferent information transmitted from the cortex of the cerebral hemispheres, as well as efferent - from the motor centers of the cerebral cortex to. The first one signals the current state of the regulated variable (muscle tone, position of the body and limbs in space), and the second one gives an idea of the required final state. Comparing the first and second, the cerebellar cortex can calculate, which reports to the motor centers. So the cerebellum continuously corrects both voluntary and automatic movements.

In different groups of animals, the cerebellum varies greatly in size and shape. The degree of its development correlates with the degree of complexity of body movements.

Representatives of all classes of vertebrates have a cerebellum, including cyclostomes (in lampreys), in which it has the form of a transverse plate that spreads over the anterior section.

The functions of the cerebellum are similar in all classes of vertebrates, including fish, reptiles, birds, and mammals. Even cephalopods (in particular octopuses) have a similar brain formation.

There are significant differences in shape and size in different biological species. For example, the cerebellum of lower vertebrates is connected to a continuous lamina in which fiber bundles are not anatomically distinguished. In mammals, these bundles form three pairs of structures called the cerebellar peduncles. Through the legs of the cerebellum, the connections of the cerebellum with other parts of the central nervous system are carried out.

Cyclostomes and fish

The internal structure of the cerebellum in fish differs from that of humans. The cerebellum of fish does not contain deep nuclei, there are no Purkinje cells.

The size and shape of the cerebellum in primary aquatic vertebrates can change not only in connection with a pelagic or relatively sedentary lifestyle. Since the cerebellum is the center of somatic sensitivity analysis, it takes an active part in the processing of electroreceptor signals. Very many primary aquatic vertebrates have electroreception (70 species of fish have developed electroreceptors, 500 can generate electrical discharges of various powers, 20 are able to both generate and recieve electric fields). In all fish with electroreception, the cerebellum is extremely well developed. If the main system of afferentation becomes the electroreception of its own electromagnetic field or external electromagnetic fields, then the cerebellum begins to play the role of a sensory (sensitive) and motor center. Often, their cerebellum is so large that it covers the entire brain from the dorsal (posterior) surface.

Amphibians and reptiles

Birds

In birds, the cerebellum consists of a massive middle part (worm), usually crossed by 9 convolutions, and two small lobes, which are homologous to a piece of the cerebellum of mammals, including humans. Birds are characterized by a high perfection of the vestibular apparatus and the system of coordination of movements. The result of the intensive development of the coordination sensorimotor centers was the appearance of a large cerebellum with real folds - furrows and convolutions. The avian cerebellum was the first vertebrate brain structure to have a cortex and a folded structure. Complex movements in a three-dimensional environment became the reason for the development of the cerebellum of birds as a sensorimotor center for coordinating movements.

mammals

A distinctive feature of the mammalian cerebellum is the enlargement of the lateral parts of the cerebellum, which mainly interact with the cerebral cortex. In the context of evolution, the enlargement of the lateral portions of the cerebellum (neocerebellum) occurs along with the enlargement of the frontal lobes of the cerebral cortex.

In mammals, the cerebellum consists of a vermis and paired hemispheres. Mammals are also characterized by an increase in the surface area of the cerebellum due to the formation of furrows and folds.

The predecessors of man and lat. homo sapiens During the Pleistocene, the increase in the frontal lobes occurred at a faster rate than in the cerebellum.

Shark brain. The cerebellum is highlighted in blue

In different groups of animals, the cerebellum varies greatly in size and shape. The degree of its development correlates with the degree of complexity of body movements.

The functions of the cerebellum are similar in all classes of vertebrates, including fish, reptiles, birds, and mammals. Even cephalopods have a similar brain formation.

Cyclostomes and fish

The internal structure of the cerebellum in fish differs from that of humans. The cerebellum of fish does not contain deep nuclei, there are no Purkinje cells.

Amphibians and reptiles

Birds

mammals

A distinctive feature of the mammalian cerebellum is the enlargement of the lateral parts of the cerebellum, which mainly interact with the cerebral cortex. In the context of evolution, the enlargement of the lateral cerebellum occurs along with the enlargement of the frontal lobes of the cerebral cortex.

In mammals, the cerebellum consists of a vermis and paired hemispheres. Mammals are also characterized by an increase in the surface area of the cerebellum due to the formation of furrows and folds.

The predecessors of man and lat. Homo sapiens of the Pleistocene time, the increase in the frontal lobes occurred at a faster rate compared to the cerebellum.

(lat. Cerebellum- literally "small brain") - the part of the brain of vertebrates responsible for the coordination of movements, the regulation of balance and muscle tone. In humans, it is located behind the medulla oblongata and the pons, under the occipital lobe of the cerebral hemispheres. With the help of three pairs of legs, the cerebellum receives information from the cerebral cortex, the basal ganglia of the extrapyramidal system, the brain stem and spinal cord. In different taxa of vertebrates, the relationship with other parts of the brain can vary.

In vertebrates with cerebral cortex, the cerebellum is a functional offshoot of the main cortex-spinal cord axis. The cerebellum receives a copy of the afferent information transmitted from the spinal cord to the cerebral cortex, as well as efferent information from the motor centers of the cerebral cortex to the spinal cord. The first one signals the current state of the regulated variable (muscle tone, position of the body and limbs in space), and the second one gives an idea of the desired final state of the variable. Correlating the first and second, the cerebellar cortex can calculate the error reported by the motor centers. Thus, the cerebellum smoothly corrects both spontaneous and automatic movements.

Although the cerebellum is connected to the cerebral cortex, its activity is not controlled by consciousness.

Comparative anatomy and evolution

The cerebellum phylogenetically developed in multicellular organisms due to the improvement of spontaneous movements and the complication of the body control structure. The interaction of the cerebellum with other parts of the central nervous system allows this part of the brain to provide accurate and coordinated body movements under various external conditions.

In different groups of animals, the cerebellum varies greatly in size and shape. The degree of its development correlates with the degree of complexity of body movements.

The cerebellum is present in representatives of all classes of vertebrates, including cyclostomes, in which it changes the shape of the transverse plate, spreads through the anterior part of the rhomboid fossa.

The functions of the cerebellum are similar in all classes of vertebrates, including fish, reptiles, birds, and mammals. Even cephalopods have similar brain formations.

There is a significant variety of shapes and sizes in different biological species. For example, the cerebellum of lower vertebrates is connected to the hindbrain by a continuous plate, in which fiber bundles are not anatomically distinguished. In mammals, these bundles form three pairs of structures called the cerebellar peduncles. Through the legs of the cerebellum, the connections of the cerebellum with other parts of the central nervous system occur.

Cyclostomes and fish

The cerebellum has the widest range of variability among the sensorimotor centers of the brain. It is located at the anterior edge of the hindbrain and can reach enormous sizes, covering the entire brain. Its development depends on several factors. The most obvious has to do with pelagic lifestyles, predation, or the ability to swim effectively through the water column. The cerebellum reaches its greatest development in pelagic sharks. It forms real furrows and convolutions, which are absent in most bony fish. In this case, the development of the cerebellum is caused by the complex movement of sharks in the three-dimensional environment of the world's oceans. The requirements for spatial orientation are too great for it not to affect the neuromorphological provision of the vestibular apparatus and the sensorimotor system. This conclusion is confirmed by the study of the brain of sharks, lead a benthic lifestyle. The nurse shark does not have a developed cerebellum, and the cavity of the IV ventricle is completely open. Its habitat and way of life does not impose such strict requirements as in long-winged sharks. The result was a relatively modest size of the cerebellum.

The internal structure of the cerebellum in fish differs from that of humans. The cerebellum of fish does not contain deep nuclei, there are no Purkinje cells.

The size and shape of the cerebellum in primordial vertebrates may differ not only in connection with the pelagic or relatively sedentary way of life. Since the cerebellum is the center of somatic sensitivity analysis, it takes the most active part in the processing of electroreceptor signals. A lot of first-water vertebrates have electroreception (70 species of fish have developed electroreceptors, 500 can generate electrical discharges of various powers, 20 are capable of both generating and receptive electric fields). In all fish with electroreception, the cerebellum is extremely well developed. If the main system of afferentation becomes electroreception of its own electromagnetic field or external electromagnetic fields, then the cerebellum begins to play the role of a sensory and motor center. Often the size of their cerebellum is so large that it covers the entire brain from the dorsal (back) surface.

Many vertebrate species have areas of the brain that are similar to the cerebellum in terms of cellular cytoarchitectonics and neurochemistry. Most species of fish and amphibians have a lateral line, an organ that senses changes in water pressure. The part of the brain that receives information from the lateral line, the so-called octavolateral nucleus, has a structure similar to the cerebellum.

Amphibians and reptiles

In amphibians, the cerebellum is poorly developed and consists of a narrow transverse plate above the rhomboid fossa. In reptiles, there is an increase in the size of the cerebellum, which is an evolutionary justification. A suitable environment for the formation of the nervous system in reptiles could be giant coal blockages, consisting mainly of club mosses, horsetails and ferns. In such multi-meter blockages from rotten or hollow tree trunks, ideal conditions could have developed for the evolution of reptiles. Modern deposits of coal directly indicate that such blockages from tree trunks were very widespread and could become a large-scale transitional environment for amphibians to reptiles. In order to take advantage of the biological benefits of tree blockages, several special characteristics had to be acquired. First, it was necessary to learn how to navigate well in three-dimensional space. For amphibians, this is not an easy task, since their cerebellum is quite small. Even in specialized tree frogs, which are a dead end branch of evolution, the cerebellum is much smaller than in reptiles. In reptiles, neuronal interconnections are formed between the cerebellum and the cerebral cortex.

The cerebellum in snakes and lizards, as in amphibians, is in the form of a narrow vertical plate above the anterior edge of the rhomboid fossa; in turtles and crocodiles it is much wider. At the same time, in crocodiles, its middle part differs in size and bulge.

Birds

The cerebellum of birds consists of a large posterior part and two small lateral appendages. It completely covers the rhomboid fossa. The middle part of the cerebellum is divided by transverse grooves into numerous leaflets. The ratio of the mass of the cerebellum to the mass of the entire brain is the largest in birds. This is due to the need for fast and accurate coordination of movements in flight.

In birds, the cerebellum consists of a massive middle part (worm), crossed mainly by 9 convolutions, and two small particles that are homologous to the cerebellar bundle of mammals, including humans. Birds are characterized by the perfection of the vestibular apparatus and the system of coordination of movements. The result of the intensive development of the coordination sensorimotor centers was the appearance of a large cerebellum with real folds - furrows and convolutions. The cerebellum of birds became the first structure of the brain of vertebrates, which was supposed to be measles and a folded structure. Complex movements in three-dimensional space caused the development of the cerebellum of birds as a sensorimotor center for coordinating movements.

mammals

A characteristic feature of the mammalian cerebellum is the enlargement of the lateral parts of the cerebellum, which mainly interact with the cerebral cortex. In the context of evolution, the enlargement of the lateral portions of the cerebellum (neocerebelum) goes hand in hand with the enlargement of the frontal lobes of the cerebral cortex.

In mammals, the cerebellum consists of the vermis and the paired hemispheres. Mammals are also characterized by an increase in the surface area of the cerebellum due to the formation of furrows and folds.

In monotremes, as in birds, the middle section of the cerebellum predominates over the lateral ones, which are located in the form of insignificant appendages. In marsupials, edentulous, bats and rodents, the middle section is not inferior to the lateral ones. Only in carnivores and ungulates are the lateral parts larger than the middle section, forming the cerebellar hemispheres. In primates, the middle section, in comparison with the hemispheres, is rather undeveloped.

The predecessors of man and lat. Homo sapiens time of the Pleistocene, the increase in the frontal lobes took place at a faster pace than in the cerebellum.

Anatomy of the human cerebellum

A feature of the human cerebellum is that, like the brain, it consists of the right and left hemispheres (lat. Hemispheria cerebelli) and an odd structure, they are connected by a “worm” (lat. Vermis cerebelli). The cerebellum occupies almost the entire posterior cranial fossa. The transverse size of the cerebellum (9-10 cm) is much larger than its anterior-posterior size (3-4 cm).

The mass of the cerebellum in an adult ranges from 120 to 160 grams. By the time of birth, the cerebellum is less developed than the cerebral hemispheres, but in the first year of life it develops faster than other parts of the brain. A pronounced increase in the cerebellum is noted between the fifth and eleventh months of life, when the child learns to sit and walk. The mass of the cerebellum of an infant is about 20 grams, at 3 months it doubles, at 5 months it increases 3 times, at the end of the 9th month - 4 times. Then the cerebellum grows more slowly, and up to 6 years of age, its mass reaches the lower limit of the normal adult - 120 grams.

Above the cerebellum lie the occipital lobes of the cerebral hemispheres. The cerebellum is delimited from the cerebrum by a deep fissure into which a process of the dura mater of the brain is wedged - the tent of the cerebellum (lat. Tentorium cerebelli) stretched over the posterior cranial fossa. Anterior to the cerebellum is the pons and medulla oblongata.

The cerebellar vermis is shorter than the hemispheres, therefore notches are formed on the corresponding edges of the cerebellum: on the anterior edge - anterior, on the posterior edge - posterior. The most prominent portions of the anterior and posterior edges form the corresponding anterior and posterior angles, and the most prominent lateral portions form the lateral angles.

Horizontal slot (lat. Fissura horizontalis) that goes from the middle legs of the cerebellum to the posterior notch of the cerebellum, divides each hemisphere of the cerebellum into two surfaces: the upper one, obliquely descending along the edges and a relatively flat and convex lower one. With its lower surface, the cerebellum is adjacent to the medulla oblongata, so that the latter is pressed into the cerebellum, forming an invagination - the valley of the cerebellum (lat. Vallecula cerebelli) at the bottom of which is a worm.

On the cerebellar vermis, the upper and lower surfaces are distinguished. Furrows running along the sides of the worm separate it from the cerebellar hemispheres: on the front surface - the smallest, on the back - deeper.

The cerebellum consists of gray and white matter. The gray matter of the hemispheres and the cerebellar vermis, located in the surface layer, forms the cerebellar cortex (lat. Cortex cerebelli) and the accumulation of gray matter in the depths of the cerebellum - the nucleus of the cerebellum (lat. Nuclei cerebelli). White matter - the brain body of the cerebellum (lat. Corpus medullare cerebelli), lies in the thickness of the cerebellum and, through the mediation of three pairs of cerebellar peduncles (upper, middle and lower), connects the gray matter of the cerebellum with the brain stem and spinal cord.

Worm

The cerebellar vermis governs posture, tone, supportive movement, and body balance. Worm dysfunction in humans manifests itself in the form of static-locomotor ataxia (impaired standing and walking).

The surfaces of the hemispheres and the cerebellar vermis are divided by more or less deep cerebellar fissures (lat. Fissurae cerebelli) on various in size numerous arcuately curved leaves of the cerebellum (lat. Folia cerebelli) most of which are located almost parallel to each other. The depth of these furrows does not exceed 2.5 cm. If it were possible to straighten the leaves of the cerebellum, then the area of its cortex would be 17 x 120 cm. Groups of convolutions form separate lobes of the cerebellum. The lobes of the same name of both hemispheres are delimited by another groove, which passes from the worm from one hemisphere to another, as a result of which two - right and left - lobes of the same name of the hemispheres correspond to a certain share of the worm.

Individual particles form parts of the cerebellum. There are three such parts: anterior, posterior and shred-nodular.

Shares of the worm	Lobes of the hemispheres
tongue (lat. lingula)	frenulum of the tongue (lat. vinculum linguale)
central part (lat. lobulus centralis)	wing of the central part (lat. ala lobuli centralis)
top (lat. culmen)	anterior quadrangular lobe (lat. lobulis quadrangularis anterior)
slope (lat. declive)	posterior quadrangular lobe (lat. lobulis quadrangularis posterior)
worm letter (lat. folium vermis)	upper and lower crescent lobes (lat. lobuli semilunares superior and inferior)
worm's hump (lat. tuber vermis)	thin part (lat. lobulis gracilis)
pyramid (lat. pyramis)	Digastric lobe (lat. lobulus biventer)
tongue (lat. uvula)	tonsil (lat. tonsilla with bilyaklaptev speech (lat. paraflocculus)
knot (lat. nodulus)	flap (lat. flocculus)

The worm and hemispheres are covered with gray matter (cerebellar cortex), inside which is white matter. The white matter, branching, penetrates into each gyrus in the form of white stripes (lat. Laminae albae). Arrow-like sections of the cerebellum show a peculiar pattern, called the "tree of life" (lat. Arbor vitae cerebelli). The subcortical nuclei of the cerebellum lie within the white matter.

The cerebellum is connected to neighboring brain structures through three pairs of legs. Cerebellar peduncles (lat. Pedunculi cerebellares) are systems of driveways, the fibers of which go towards the cerebellum and from it:

Inferior cerebellar peduncles (lat. Pedunculi cerebellares inferiores) go from the medulla oblongata to the cerebellum.
Middle cerebellar peduncles (lat. Pedunculi cerebellares medii)- from the pons to the cerebellum.
Superior cerebellar peduncles (lat. Pedunculi cerebellares superiores)- go to the midbrain.

Nuclei

The nuclei of the cerebellum are paired accumulations of gray matter, which lie in the thickness of the white, closer to the middle, that is, the cerebellar vermis. There are the following cores:

dentate nucleus (lat. Nucleus dentatus) lies in the medial-lower areas of the white matter. This nucleus is a wave-like plate of gray matter with a small break in the middle region, which is called the gate of the dentate nucleus (lat. Hilum nuclei dentait). The jagged core is like a butter core. This similarity is not accidental, since both nuclei are connected by conductive pathways, lead-cerebellar fibers (lat. Fibrae olivocerebellares), and each twist of the oil core is similar to the twist of the other.
Korkopodibne kernel (lat. Nucleus emboliformis) located medially and parallel to the dentate nucleus.
Spherical nucleus (lat. Nucleus globosus) lies somewhat in the middle of the crust-like nucleus and can be presented in the section in the form of several small balls.
The core of the tent (lat. Nucleus fastigii) localized in the white matter of the worm, on both sides of its median plane, under the uvula lobule and the central lobule, in the roof of the IV ventricle.

The nucleus of the tent, being the most medial, is located on the sides of the midline in the area where the tent is pressed into the cerebellum (lat. fastigium). Bichnishe from it is respectively spherical, crust-like and dentate nuclei. These nuclei have different phylogenetic ages: nucleus fastigii refers to the ancient part of the cerebellum (lat. Archicerebellum) connected to the vestibular apparatus; nuclei emboliformis et globosus - up to old part (lat. Paleocerebellum), which arose in connection with the movements of the body, and nucleus dentatus - to the new (lat. neocerebellum), developed in connection with movement with the help of limbs. Therefore, when each of these parts is damaged, various aspects of the motor function are violated, corresponding to different stages of phylogenesis, namely: archicerebellum balance of the body is disturbed, with injuries paleocerebellum the work of the muscles of the neck and trunk is disrupted, if damaged neocerebellum - work of the muscles of the limbs.

The nucleus of the tent is located in the white matter of the worm, the remaining nuclei lie in the hemispheres of the cerebellum. Almost all information coming from the cerebellum is switched to its nuclei (with the exception of the connection of the glomerular-nodular lobule with the vestibular nucleus of Deiters).

The cerebellum is best developed in birds. cerebellum - comparative anatomy and evolution

Cerebellum - Comparative anatomy and evolution

Cyclostomes and fish

Amphibians and reptiles

Birds

mammals

Cerebellum - Human Cerebellum Anatomy

Worm

Slices

Nuclei

blood supply

arteries

Superior cerebellar artery

Anterior inferior cerebellar artery

Posterior inferior cerebellar artery

Vienna

Cerebellum - Neurophysiology

Functional plasticity, motor adaptation and motor learning

Functions

Conducting paths

upper legs

Medium legs

lower legs

Cerebellum - Symptoms of lesions

Cerebellum - Pathology

Neoplasms

Abscess

hereditary diseases

Hereditary cerebellar ataxia of Pierre Marie

Olivopontocerebellar degenerations

Alcoholic cerebellar degeneration

Multiple sclerosis

Cerebral circulation disorders

Traumatic brain injury

Malformations

Dandy-Walker Syndrome

Arnold-Chiari Syndrome

During the classes.

I. Organizational moment.

II. Repetition of homework (frontal survey):

III. New material:

1. Fish.

2. Amphibians and reptiles.

3. Birds.

4. Mammals.

1. Fish.

2. Amphibians.

3. Birds.

4. Mammals.

Cyclostomes and fish

Amphibians and reptiles

Birds

mammals

Comparative anatomy and evolution

Cyclostomes and fish

Amphibians and reptiles

Birds

mammals

Anatomy of the human cerebellum

Worm

Shares

Nuclei