The red nucleus of the midbrain is a subcortical center. Midbrain. Structure of the midbrain in sections

The human brain is a complex structure, an organ of the human body that controls all processes in the body. Midbrain included in his middle section, belongs to the oldest visual center, in the process of evolution it acquired new functions and took a significant place in the life of the human body.

The midbrain is a small (only 2 cm) section of the brain, one of the elements of the brain stem. Located between the subcortex and the posterior part of the brain, it is located in the very center of the organ. It is a connecting segment between the upper and lower structures, since the nerve tracts of the brain pass through it. The anatomical structure is not as complex as the other sections, but in order to understand the structure and functions of the midbrain, it is better to view it in cross section. Then 3 parts of it will be clearly visible.

Roof

In the posterior (dorsal) area there is a quadrigeminal plate, consisting of two pairs of hemispherical colliculi. It is a roof, placed above the water supply, and covered by the cerebral hemispheres. At the top there is a pair of visual hillocks. They are larger in size than the lower elevations. Those hills that lie below are called auditory. The system communicates with the geniculate bodies (elements of the diencephalon), the upper ones with the lateral ones, the lower ones with the medial ones.

Tire

The area follows the roof and includes the ascending tracts of nerve fibers, the reticular formation, the nuclei of the cranial nerves, the medial and lateral (auditory) lemniscus and specific formations.

Brain stems

In the ventral region lie the cerebral peduncles, represented by a pair of ridges. Their main part includes the structure of nerve fibers belonging to the pyramidal system, which diverges to the cerebral hemispheres. Legs cross longitudinal medial bundles, they include the roots of the oculomotor nerve. In the depths there is a perforated substance. At the base there is white matter, along which descending pathways stretch. In the space between the legs there is a hole where blood vessels pass.

The midbrain is a continuation of the pons, the fibers of which stretch transversely. This makes it possible to clearly see the boundaries of the sections on the basal (main) surface of the brain. From the dorsal site, the restriction occurs from the auditory hills and the transition of the fourth ventricle into the aqueduct.

Midbrain nuclei

In the midbrain, gray matter is located in the form of a concentration of nerve cells, forming the nerve nuclei of the skull:

1. The nuclei of the oculomotor nerve are located in the tegmentum, closer to the middle, ventral to the aqueduct. They form a layered structure and participate in the occurrence of reflexes and visual reactions in response to signals. Also, during the formation of visual stimuli, the nuclei control the movement of the eyes, body, head and facial expressions. The system complex includes the main nucleus, consisting of large cells, and small cell nuclei (central and outer).
2. The nucleus of the trochlear nerve consists of paired elements and is located in the tegmental segment in the region of the inferior colliculi directly under the aqueduct. It is represented by a homogeneous mass of large isodiametric cells. Neurons are responsible for hearing and complex reflexes; with their help, a person reacts to sound stimuli.
3. The reticular formation is represented by a cluster of reticular nuclei and a network of neurons, located in the thickness of the gray matter. In addition to the middle center, it includes the diencephalon and medulla oblongata; the formation is connected with all parts of the central nervous system. It affects motor activity, endocrine processes, affects behavior, attention, memory, inhibition.

Specific education

The structure of the midbrain includes important structural formations. The centers of the extrapyramidal system of the subcortex (a set of structures responsible for movement, body position and muscle activity) include:

Red kernels

In the tegmentum, ventral to the gray matter and dorsal to the substantia nigra, the red nuclei are located. Their color is provided by iron, which appears in the form of ferritin and hemoglobin. Cone-shaped elements stretch from the level of the inferior colliculi to the hypothalamus. They are connected by nerve fibers to the cerebral cortex, cerebellum, and subcortical nuclei. Having received information from these structures about the position of the body, the cone-shaped elements send a signal to the spinal cord and correct muscle tone, preparing the body for the upcoming movement.

If the connection with the reticular formation is disrupted, decerebrate rigidity develops. It is characterized by strong tension in the extensor muscles of the back, neck and limbs.

Black matter

If we consider the anatomy of the midbrain in section, from the pons to the diencephalon in the peduncle two continuous stripes of the black substance are clearly visible. These are clusters of neurons abundantly supplied with blood. The dark color is provided by the pigment melanin. The degree of pigmentation is directly related to the development of structure functions. It appears in a person by 6 months of life, reaching its maximum concentration by 16 years. The substantia nigra divides the stalk into sections:

• dorsal is the tire;
• the ventral section is the base of the leg.

The substance is divided into 2 parts, one of which, the pars compacta, receives signals in the basal ganglia circuit, delivering the hormone dopamine to the telencephalon to the striatum. The second - pars reticulata - transmits signals to other parts of the brain. The nigrostriatal tract originates in the substantia nigra, which is one of the main neural pathways of the brain that initiates motor activity. This area mainly performs conductive functions.

When the substantia nigra is damaged, a person experiences involuntary movements of the limbs and head and difficulty walking. When dopamine neurons die, the activity of this pathway decreases and Parkinson's disease develops. There is an opinion that with an increase in dopamine production, schizophrenia develops.

The cavity of the midbrain is the aqueduct of Salvia, the length of which is approximately one and a half centimeters. A narrow canal runs ventral to the quadrigeminalis and is surrounded by gray matter. This remnant of the primary brain bladder connects the cavities of the third and fourth ventricles. It contains cerebrospinal fluid.

Functions

All areas of the brain work interconnectedly, together creating a unique system for supporting human life. The main functions of the midbrain are designed to perform the following role:

• Sensory functions. The load for sensory sensations is carried by the neurons of the quadrigeminal nuclei. Signals from the organs of vision and hearing, the cerebral cortex, the thalamus and other brain structures. They provide accommodation of vision to the degree of illumination by changing the size of the pupil; his movement and turns of his head towards the irritating factor.
• Conductor. The midbrain plays the role of a conductor. The base of the legs, nuclei and substantia nigra are mainly responsible for this function. Their nerve fibers are connected to the cortex and underlying brain regions.
• Integrative and motor. Receiving commands from sensory systems, the nuclei convert the signals into active actions. Motor commands are given by the stem generator. They enter the spinal cord, making possible not only muscle contraction, but also the formation of body posture. A person is able to maintain balance in various positions. Reflexive movements are also made when moving the body in space, helping to adapt so as not to lose orientation.

In the midbrain there is a center that regulates the degree of pain. Receiving a signal from the cerebral cortex and nerve fibers, the gray matter begins to produce endogenous opiates, which determine the pain threshold, increasing or decreasing it.

Reflex functions

The midbrain carries out its functions through reflexes. By using medulla oblongata complex movements of the eyes, head, torso, and fingers are performed. Reflexes are divided into:

• visual;
• auditory;
• sentinel (indicative, answering the question “what is it?”).

They also provide redistribution of skeletal muscle tone. The following types of reactions are distinguished:

• Static ones include two groups - postural reflexes, which are responsible for maintaining a person’s posture, and rectifying ones, which help to return to the normal position if it has been disturbed. This type of reflexes regulates the medulla oblongata and spinal cord, reading data from the vestibular apparatus, with tension in the neck muscles, organs of vision, and skin receptors.
• Statokinetic. Their goal is to maintain balance and orientation in space while moving. A striking example: a cat falling from a height will in any case land on its paws.

The statokinetic group of reflexes is also divided into types.

• With linear acceleration, a lift reflex appears. When a person quickly rises up, the flexor muscles tense; when lowered, the tone of the extensor muscles increases.
• During angular acceleration, for example, during rotation, to maintain visual orientation, nystagmus of the eyes and head occurs: they are turned in the opposite direction.

All reflexes of the midbrain are classified as innate, that is, unconditioned types. An important role in integration processes is assigned to the red core. Its nerve cells activate the skeletal muscles, help maintain the usual body position and take a pose to perform any manipulations.

The substantia nigra is involved in controlling muscle tone and restoring normal posture. The structure is responsible for the sequence of acts of chewing and swallowing; the work of fine motor skills of the hands and eye movements depend on it. The substance is involved in the work of the autonomic system: regulates tone blood vessels, heart rate, breathing.

Age characteristics and prevention

The brain is a complex structure. It operates with close interaction between all segments. The center that controls the middle section is the cerebral cortex. With age, connections become weaker, and reflex activity weakens. Since the area is responsible for motor function, even minor disruptions in this tiny segment lead to the loss of this important ability. It is more difficult for a person to move, and serious violations lead to diseases nervous system and complete paralysis. How to prevent disorders in the functioning of the brain in order to remain healthy until old age?

First of all, you should avoid hitting your head. If this happens, it is necessary to begin treatment immediately after the injury. It is possible to preserve the functions of the midbrain and the entire organ until old age if you train it with regular exercises:

1. The lifestyle a person leads is important for physical and mental health. Drinking alcohol and smoking destroy neurons, which gradually leads to a decrease in mental and reflex activity. Therefore from bad habits should be abandoned, and the sooner this is done, the better.
2. Moderate physical exercise, walks in nature supply the brain with oxygen, which has a beneficial effect on its activity.
3. You shouldn’t give up reading, solving charades and puzzles: intellectual activity keeps the brain active.
4. An important aspect of the functioning of brain structures is nutrition: fiber, protein, and greens must be present in the diet. The midbrain responds positively to intake of antioxidants and vitamin C.
5. Needs to be controlled arterial pressure: health vascular system affects general state person.

The brain is a flexible system that can be successfully developed. Therefore, by constantly improving your mind and body, you can maintain clarity of thoughts and motor activity until old age.

The midbrain, its structure and functions are determined by the location of the structure, providing movement, auditory and visual reactions. If you have difficulty maintaining balance or lethargy, you should consult a doctor and undergo an examination to find the cause of the disturbances and eliminate the problem.

6. Functions of the nuclei of the inferior and superior colliculus. Functions of the red nucleus and substantia nigra of the midbrain.

The superior colliculi are the primary visual centers. Pathways from retinal neurons approach them. From them, signals go to the thalamus, and along the descending tectospinal tract to the motor neurons spinal cord. The primary analysis of visual information occurs in the superior colliculus. For example, determining the position of a light source and the direction of its movement. They also form visual orientation reflexes (turning the head towards the light source).

The inferior colliculi are the primary auditory centers. Signals from the phonoreceptors of the ear go to them, and from them to the thalamus. From them to motor neurons there are also paths as part of the tectospinal tract. In the lower tuberosities, the primary analysis of auditory signals is carried out, and due to connections with motor neurons, orienting reflexes to sound stimuli are formed.

Functions of the red nucleus and substantia nigra of the midbrain.

Located at the top of the cerebral peduncle. Nerve paths go to it from the cerebral cortex, subcortical nuclei, and cerebellum. From it goes the rubrospinal tract to the motor neurons of the spinal flexors and reticular formation of the medulla oblongata. Due to the different functional significance of the Deiters nucleus and the red nucleus, when the trunk between the midbrain and medulla oblongata is cut in animals, decerebrate rigidity occurs (a sharp increase in the tone of all extensor muscles): the head of the animal

throws back, the back is arched, the limbs are extended (the red nucleus, activating the flexor motor neurons, inhibits the extensor motor neurons through intercalary inhibitory neurons, at the same time the inhibitory effect of the red nucleus on the reticular formation of the medulla oblongata is eliminated, near the Deiters nucleus, in the absence of the influence of the red nucleus, the excitatory effect of the Deiters nucleus on extensor motor neurons).

Located in the cerebral peduncles, it is involved in the regulation of the acts of chewing, swallowing and their sequence, as well as in the coordination of small and precise movements of the fingers. The neurons of this nucleus synthesize dopamine, which is supplied to the basal ganglia of the brain. It plays an important role in the control of complex motor acts. Damage to the substantia nigra leads to degeneration of dopaminergic fibers projecting into the striatum, impairment of fine movements of the fingers, development of muscle rigidity and tremor (Parkinson's disease). Takes part in eating behavior, regulates plastic tone, emotional behavior.

7. Functions of the reticular formation of the brain stem, their characteristics. Ascending and descending influences of the reticular formation on other structures of the brain and spinal cord.

1. Somatomotor control (activation of skeletal muscles), can be direct through the reticulospinal tract and indirect through the cerebellum, olives, colliculus, red nucleus, substantia nigra, striatum, thalamic nuclei and somatomotor areas of the cortex. 2. Somatosensitive control, i.e. reduction in levels of somatosensory information - “slow pain”, modification of perception various types sensory sensitivity (hearing, vision, vestibulation, smell).

3. Visceromotor control of the state of the cardiovascular and respiratory systems, the activity of various smooth muscles internal organs.

4. Neuroendocrine transduction through the influence on neurotransmitters, the centers of the hypothalamus and then the pituitary gland.

5. Biorhythms through connections with the hypothalamus and pineal gland.

6. Various functional states of the body (sleep, awakening, state of consciousness, behavior) are realized through numerous connections of the nuclei of the reticular formation with all parts of the central nervous system.

7. Coordination of the work of different centers of the brain stem, providing complex visceral reflex responses (sneezing, coughing, vomiting, yawning, chewing, sucking, swallowing, etc.).

Ascending and descending influences of the reticular formation on other structures of the brain and spinal cord.

With the ascending influence of the reticular formation, the activity of analytical-synthetic activity increases, the speed of reflexes increases, the body prepares to react to an unexpected situation. Therefore, the reticular formation is involved in the organization of defensive, sexual, and digestive behavior. On the other hand, it can selectively activate or inhibit certain brain systems. In turn, the cerebral cortex, through descending pathways, can have an exciting effect on the reticular formation.

The descending reticulospinal tracts go from the reticular formation to the neurons of the spinal cord. Therefore, it can have descending excitatory and inhibitory effects on its neurons. For example, its hypothalamic and mesencephalic regions increase the activity of alpha motor neurons in the spinal cord. As a result, the tone of skeletal muscles increases and motor reflexes strengthen. The inhibitory effect of the reticular formation on the spinal motor centers is carried out through Renshaw inhibitory neurons. This leads to inhibition of spinal reflexes.

Latin name: nucleus ruber.

In the midbrain, the red nuclei are located in the very center. If we make a horizontal slice through the midbrain, then diagonally between and we will see two pale pink spots. These will be the red kernels. It is believed that they owe their color to iron, which they contain in two different forms - hemoglobin and ferritin.

In the following screenshot you can see a sagittal section of the brain stem. The bottom of the red nucleus lies on the ascending fibers of the superior cerebellar peduncles at the level of the top of the inferior cerebellum. From above - they reach the level of the hypothalamus.

You can learn more about where the red core is located on ours.

The red nucleus is motor, responsible for muscle tone and reflexes.

There are two parts:

• posterior large cell (magnocellular) - less developed in humans than in other vertebrates, because In humans, the cerebral cortex is much more developed, which takes away some of the functions from the magnocellular part.
• anterior parvocellular (parvocellular) - transmits information from the motor cortex to the cerebellum through the olives.

Some researchers isolate the posteromedial part separately.

Tracts

Movement control is possible thanks to the rubrospinal tract. Its fibers begin in the red nuclei, namely in the posterior, magnocellular part, and immediately cross the middle (the cross is located at the level of the ventral part of the median suture). Then they pass through the cerebral peduncles, pons and medulla oblongata, reaching the spinal cord. there its fibers lie in the lateral funiculi, eventually connecting with the anterior horns.

Part of the fibers of the rubrospinal tract, originating in the red nuclei and going to the motor nuclei of the bridge, is called the red nucleus-pontine tract.

It is also possible to distinguish rubroolive fibers, which connect the small-celled part of the red nucleus with the lower olive on its side. Not everything is clear about these fibers - they are classified as rubro- and corticospinal tracts, although some authors consider them fibers of the central tegmental tract.

in the red nuclei most of the fibers of the superior cerebellar peduncles end after decussation in the midbrain. The fibers of the dentate-thalamic tract pass through them in transit (without interactions).

Functions

In humans, the rubrospinal tract coming from the red nucleus partly controls gait and movements of the shoulder girdle. "Partially" means that it only controls large movements. The corticospinal tract is responsible for fine motor skills. If you “turn it off” and leave only the rubrospinal one, then the movements of such a person will become sharp and sweeping.

I also note that the rubrospinal tract is responsible for reflex movements.

Animal experiments show that electrical stimulation of the rubrospinal tract leads to excitation of flexor motor neurons and inhibition of extensor motor neurons. Thus, when the tract is cut at the level of the midbrain, the limbs are straightened and remain tense in this position. the head is thrown back.

Defeats

Exists a large number of syndromes associated with damage to the red nuclei, their tracts and nearby structures. But this is not a medical article, so we will focus only on a few especially interesting ones.

If the rostral part of the red nucleus is damaged, the patient experiences severe tremor and the sensitivity of the contralateral half of the body decreases.

If the same tremor occurs in combination with a “frozen hand,” then we can talk about rubrothalamic syndrome.

Often, along with the red nucleus, the oculomotor system also suffers. In such cases, muscle weakness or tremors and divergent strabismus, drooping eyelids and other symptoms associated with the eyes are simultaneously observed.

Control questions:

• where is the red nucleus located and why is it called that?
• what is its main role?

Midbrain enters part of the brain stem. Adjacent to it on the ventral side back surface mastoid bodies and the anterior edge of the bridge behind (Atl., Fig. 23, p. 133). It has a roof and legs. The cavity of the midbrain is brain plumbing- a narrow canal, about 1.5 cm long, which communicates below with the fourth ventricle, and above with the third.

Roof of the midbrain It is a quadrigeminal plate and is located above the cerebral aqueduct. The roof of the midbrain consists of four elevations - mounds, which are separated from each other by two grooves - longitudinal and transverse.

In a flat groove between the upper tubercles lies pineal gland. Each hillock passes into the so-called handle of the hillock, which goes laterally, anteriorly and upward, to the diencephalon. The handle of the superior colliculus is directed towards the lateral geniculate body; the handle of the inferior colliculus - to the medial geniculate body.

The upper two colliculi of the midbrain roof and the lateral geniculate body are the subcortical centers of vision. Both inferior colliculus and medial geniculate bodies are subcortical hearing centers.

Originates from the roof of the midbrain tectospinal tract. Its fibers, after crossing in the tegmentum of the midbrain, go to the motor nuclei of the brain and the cells of the anterior horns of the spinal cord. The pathway carries efferent impulses in response to visual and auditory stimuli.

Brain stems occupy the anterior part of the midbrain, are located under the bridge and are directed to the right and left hemispheres of the forebrain. The recesses between the right and left legs are called interpeduncular fossa. The legs consist of a base and a tegmentum, which are separated by pigmented cells of the substantia nigra.

Passes at the base of the legs pyramid path, traveling through the pons to the spinal cord and corticonuclear, the fibers of which reach the neurons of the motor nuclei of the cranial nerves located in the area of ​​the fourth ventricle and aqueduct, as well as corticopontine tract ending on the cells of the base of the bridge. Consequently, the bases of the cerebral peduncles consist entirely of white matter, and descending pathways pass here. The tegmentum of the pedicles continues the tegmentum of the pons and medulla oblongata. Its upper surface serves as the bottom of the brain's aqueduct. The nuclei of the trochlear (IV) and oculomotor (III) nerves are located in the tegmentum, and ascending pathways pass.

In the region of the third pair of nerves lies the parasympathetic nucleus; it consists of interneurons of the autonomic nervous system. In the upper part of the tegmentum of the midbrain there passes the dorsal longitudinal fasciculus, connecting the thalamus and hypothalamus with the nuclei of the brain stem.

Among the nuclei of gray matter there are substantia nigra And red core. Black substance separates the base and tegmentum of the cerebral peduncles. Its cells contain the pigment melanin. This pigment exists only in humans and appears at the age of 3-4 years. The substantia nigra receives impulses from the cerebral cortex, striatum and cerebellum and transmits them to the neurons of the superior colliculus and brainstem nuclei, and then to the motor neurons of the spinal cord. The substantia nigra plays an essential role in the integration of all movements and in the regulation of the plastic tone of the muscular system.

Red core is the largest nucleus of the tegmentum and is located slightly above (dorsally) the substantia nigra. It has an elongated shape and extends from the level of the inferior colliculus to the thalamus. At the level of the inferior colliculus it occurs cross superior cerebellar peduncles. Most of them end in the red nucleus, and a smaller part passes through the red nucleus and continues to the thalamus. The red nucleus contains fibers from the cerebral hemispheres. From its neurons there are ascending pathways, in particular to the thalamus. The main descending path of the red nuclei is rubrospinal(rednuclear spinal cord). Immediately upon leaving the nucleus, its fibers cross and are directed along the tegmentum of the brain stem and the lateral cord of the spinal cord to the motor neurons of the anterior horns of the spinal cord.

Lateral to the red nucleus in the tegmentum is located medial loop. Between it and the gray matter surrounding the aqueduct lie nerve cells and fibers reticular formation(continuation of the reticular formation of the pons and medulla oblongata) and pass through ascending and descending pathways.

Functions of the midbrain. The midbrain performs sensory, conductive, motor and reflex functions.

Touch functions are carried out due to the entry of visual and auditory information into the midbrain. The superior colliculi of the quadrigeminal are the primary subcortical centers of the visual analyzer (together with the lateral geniculate bodies of the diencephalon), the lower colliculi are the auditory centers (together with the medial geniculate bodies of the diencephalon). They are where the primary switching of visual and auditory information occurs.

Conductor function is that all ascending pathways to the overlying parts of the central nervous system pass through the midbrain: the thalamus (medial lemniscus, spinothalamic tract), forebrain and cerebellum. Descending tracts pass through the midbrain to the medulla oblongata and spinal cord. These include the pyramidal tract, corticopontine fibers, and ruboreticulospinal tract.

Motor function is realized through the trochlear nerve, nuclei of the oculomotor nerve, red nucleus, and substantia nigra. The red nucleus and the surrounding motor nuclei are important for the implementation of all movements, as they reflexively regulate muscle tone. The basal ganglia of the brain and the cerebellum have their endings in the red nuclei. Disruption of connections between the red nuclei and the reticular formation of the medulla oblongata leads to decerebral rigidity. This condition is characterized by severe tension in the extensor muscles of the limbs, neck, and back. The main cause of decerebral rigidity is the pronounced activating influence of the lateral vestibular nucleus (Deiters nucleus) on extensor motor neurons. When the brain is transected below the nucleus of the lateral vestibular nerve, decerebral rigidity disappears.

The red nuclei, receiving information from the motor zone of the cerebral cortex, subcortical nuclei and cerebellum about the impending movement, send corrective impulses to the motor neurons of the spinal cord along the rubrospinal tract and thereby regulate muscle tone, preparing its level for voluntary movement.

The substantia nigra regulates the acts of chewing and swallowing (their sequence), and ensures precise movements of the fingers, for example, when writing. The neurons of this nucleus are capable of synthesizing the neurotransmitter dopamine, which travels along axons to the basal ganglia of the brain. Damage to the substantia nigra leads to disruption of plastic muscle tone and is associated with the neuralgic disease Parkinson's disease. Parkinsonism manifests itself in a violation of fine friendly movements, the function of facial muscles and the manifestation of involuntary muscle contractions, or tremor.

Fine regulation of plastic tone when playing the violin, writing, and doing graphic work is ensured by the substantia nigra. At the same time, when holding a certain position for a long time, plastic changes occur in the muscles, which ensures the least energy expenditure. Regulation of this process is ensured by the cells of the substantia nigra.

Neurons of the oculomotor and trochlear nerve nuclei regulate eye movements up, down, toward the nose, and down toward the corner of the nose. Neurons of the accessory nucleus of the oculomotor nerve (Yakubovich's nucleus) regulate the lumen of the pupil and the curvature of the lens.

Reflex functions. Functionally independent structures of the midbrain are the quadrigeminal tuberosities. Their main function is to organize alert reactions and the so-called start reflexes to sudden, not yet recognized visual or sound signals. Activation of the midbrain in these cases through the hypothalamus leads to increased muscle tone and increased heart contractions; preparation for avoidance and a defensive reaction occurs.

The quadrigeminal region organizes indicative visual and auditory reflexes. In humans, this reflex is a guard reflex. In cases of increased excitability of the quadrigeminals, with sudden sound or light stimulation, a person begins to flinch, sometimes jump to his feet, scream, move away from the stimulus as quickly as possible, and sometimes run away uncontrollably.

If the quadrigeminal reflex is impaired, a person cannot quickly switch from one type of movement to another. Consequently, the quadrigeminal muscles take part in the organization of voluntary movements.

Development of the midbrain. The growth and functional development of the midbrain is associated with the development of other parts of the brain stem and the formation of its pathways to the cerebellum and cerebral cortex.

In a newborn, the mass of the midbrain is 2.5 g. Its shape and structure do not differ from those of an adult. The cerebral aqueduct is wider, the oculomotor nerve has myelinated fibers. The substantia nigra and reticular formation extend along the length of the midbrain to the globus pallidus. Their cells are well differentiated, but do not contain pigment; its appearance occurs in the sixth month of life and sometimes almost at puberty. They reach their maximum development at about 16 years of age. The development of pigmentation is directly related to the improvement of the function of the substantia nigra. The medial part of the substantia nigra begins to myelinate in the first 2-3 months of life.

The red nucleus is well defined, its connections with other parts of the brain are formed earlier than the pyramidal system. In a newborn, the pyramidal fibers are myelinated, and the paths going to the cortex do not have a myelin sheath at this time. They myelinate from the 4th month of life. Medial loop, as well as the fibers connecting the red nucleus and the substantia nigra are myelinated.

Pigmentation of the red nucleus begins at 2 years of age and ends by 4 years.

Functional development of the midbrain. A number of reflexes, carried out with the participation of the midbrain, are formed during intrauterine development. Already at the early stages of embryogenesis, tonic and labyrinthine reflexes, defensive and other motor reactions in response to various irritations are noted.

2-3 months before birth, the fetus exhibits motor reactions in response to sound, temperature, vibration and other stimuli.

In the first days of a child's life, Moro reflex, which is expressed in the fact that in response to a loud sudden sound, the child unbends his arms to the side at right angles to the body, straightens his fingers and torso. This reflex disappears by the 4th year of a child’s life. It persists in mentally retarded children and is thought to be associated with brain immaturity.

The Moro reflex is replaced by the opposite reaction. So, for example, with the same sharp irritation, a child experiences a general motor reaction with a predominance of flexion movements. It is often accompanied by movement of the head and eyes, changes in breathing, or a delayed sucking reflex. This reaction is called startle reaction or flinching and is considered as the first manifestation of the orienting reflex.

With repeated stimulation, this reflex disappears. With age, in response to irritation, it becomes less generalized; from the 2nd week of life, concentration on sound appears, and in the 3rd month, a typical indicative reaction appears, manifested in turning the head towards the irritant. Initial stages this reaction is associated with the early formation of receptors inner ear, conducting pathways and quadrigeminals, its improvement - with the development of the geniculate bodies and the cortical part of the auditory analyzer.

By the time of birth, the fetus has well-developed structures that underlie reflexes that arise in response to visual stimulation. The initial form of responses is defensive reflexes.

For example, in newborn children, touching the eyelashes, conjunctiva, cornea or blowing causes the eyelids to close. The zone of this reflex in a newborn is wider - his eyes close when he touches the tip of his nose and forehead. When a sleeping child is illuminated, his eyelids close more tightly. Reflex blinking (response to the rapid approach of an object to the eyes) appears by 1.6-2 months of life.

The newborn is well developed pupillary reflex. This reflex is present even in premature babies. Pupil dilation to sound and skin stimuli appears later - from the 10th week of a child’s life.

During the first half of the year, most children develop tonic reflex from the eyes to the neck muscles. It manifests itself in the fact that in a vertical position of the child’s body (without supporting the head), when the eyes are illuminated, the head quickly leans back, while the body falls into opisthonus, that is, a condition in which the body bends back due to an increase in the tone of the extensor muscles. The reaction persists as long as the eyes are illuminated. This reflex is especially pronounced in newborns.

Labyrinthine, or righting reflex, as a result of which the correct position in space is occupied first by the head and then by the whole body, is absent in the newborn. This reflex is associated with the formation of the vestibular apparatus and red nuclei. It is well expressed from 2-3 months of a child’s life.

Labyrinth reflexes that occur during rotation (head tilt and eyeballs in the direction opposite to rotation), according to most researchers, take place immediately after birth, they are well expressed from the 7th day of the child’s life. From the first days of life, a lift reaction is also observed, which in a child is expressed in raising his arms up while quickly lowering his body (the “falling” movement).

Reflexes of body position in space depend on the correct distribution of muscle and joint tone. Static, righting and righting reflexes are formed after birth. Their formation is associated with the further development of the brain and cerebral cortex. In this case, there is a change from the simplest reflex acts to more complex ones.

For example, congenital preliminary locomotor acts disappear at 4-5 months of a child’s life. The reflex from the eyes to the neck disappears first (at 3 months), then the vestibular reaction to the limbs (at 4-5 months). The contraction of the adductor muscles of the opposite leg, which accompanies the knee reflex, fades away by 7 months, the cross flexion reflex of the legs - at 7-12 months, and the hand and foot grasping reflex turns into voluntary grasping by the end of the first year of life. By this time, the Babinski reflex almost completely disappears.

During the first year of life, the child learns to roll over on his stomach, crawl on his stomach and on all fours, sit, stand up, and walk by the end of the year.

Reticular formation of the brainstem and its influence on the activity of various parts of the brain. The reticular formation (RF) is represented by a network of neurons with numerous branches in different directions. Neurons are located either diffusely or form nuclei.

Most RF neurons have long dendrites and short axons. There are giant neurons with long axons that form T-branch: one of the axon branches has a descending direction, and the second has an ascending direction. For example, in the descending direction - the reticulospinal and rubrospinal tracts. The axons of RF neurons form a large number of collaterals and synapses that end on neurons of various parts of the brain. The reticular formation is located in the thickness of the gray matter of the medulla oblongata, midbrain, diencephalon (Atl., Fig. 26, p. 135) and is initially associated with the RF of the spinal cord. In this regard, it is considered as a single system.

The reticular formation has straight and feedbacks with the forebrain cortex, basal ganglia, diencephalon, cerebellum, midbrain, medulla oblongata and spinal cord. According to modern concepts, the transition of the cortex to an active state is associated with fluctuations in the number of ascending signals from the reticular formation of the brain stem. The number of these signals depends on the entry of sensory impulses into the reticular formation along the collaterals of specific afferent ascending pathways. Almost to the reticular formation information comes from all sensory organs along collaterals from the spinal reticular tract, propriospinal tracts, afferent cranial nerves, from the thalamus and hypothalamus, from the motor and sensory areas of the cortex (Fig. 9).

Most neurons of the reticular formation are polysensory, that is, they respond to stimulation of various modalities (light, sound, tactile, etc.). Its neurons have large receptive fields, a long latent period and poor reproducibility of reactions. These properties are opposite to the properties of specific nuclei, and therefore reticular neurons are classified as nonspecific.

Rice. 10. Afferent and efferent connections of the reticular formation of the brainstem (according to: Nozdrachev et al., 2004)

However, studies with brainstem RF stimulation have shown that it can selectively have an activating or inhibitory effect on different shapes behavior, on sensory, motor, visceral systems of the brain.

The activity of RF neurons is different and, in principle, similar to the activity of neurons in other brain structures, but among the RF neurons there are those that have stable rhythmic activity, independent of incoming signals. At the same time, in the RF of the midbrain and pons there are neurons that are “silent” at rest, that is, they do not generate impulses, but are excited when visual or auditory receptors are stimulated. These are the so-called specific neurons, providing a quick response to sudden signals.

In the reticular formation of the medulla oblongata, midbrain and pons, signals of various modalities converge. Signals from the visual and auditory sensory systems mainly arrive at neurons in the midbrain.

The RF controls the transmission of sensory information passing through the nuclei of the thalamus by inhibiting the neurons of the nonspecific nuclei of the thalamus, thereby facilitating the transmission of sensory information to the cerebral cortex. In the reticular formation of the pons, medulla oblongata, and midbrain there are neurons that respond to painful stimuli coming from muscles or internal organs, which creates a general diffuse discomfort that is not always clearly localized, painful sensation("Blunt pain").

The reticular formation of the brainstem is directly related to the regulation of muscle tone, since the RF of the brainstem receives signals from the visual and vestibular analyzers and cerebellum. From the RF to the motor neurons of the spinal cord and the nuclei of the cranial nerves, signals are received that organize the position of the head, torso, etc. The reticular formation of the brain stem is involved in the transmission of information from the cerebral cortex, spinal cord to the cerebellum and, conversely, from the cerebellum to the same systems . The function of these connections is to prepare and implement motor skills associated with habituation, indicative reactions, pain reactions, organization of walking, and eye movements. The reticular formation takes part in regulating the functioning of the respiratory and cardiovascular centers. For example, damage respiratory center, located in the RF of the medulla oblongata, leads to respiratory arrest.

Another vital center of the Russian Federation is the vasomotor center, which regulates changes in the lumen of the vessels of veins and arteries, and blood pressure. In the regulation of autonomic functions great importance have so-called start neurons RF. They give rise to the circulation of excitation within a group of neurons, providing the tone of regulated autonomic systems. The influences of the reticular formation on all parts of the brain can be divided into descending and ascending. In turn, each of these influences has an inhibitory and excitatory effect.

Descending influences RFs of the brain stem on the regulatory activity of the spinal cord were established by I.M. Sechenov (1862). They showed that when the midbrain is irritated by salt crystals, the reflexes of withdrawing the frog's paws arise slowly, require stronger stimulation, or do not appear at all, that is, they are inhibited.

G. Magun (1945-1950), applying local irritations to the RF of the medulla oblongata, found that when certain points are irritated, the flexion reflexes of the forepaw, knee, and cornea are inhibited and become sluggish. When the RF was stimulated at other points of the medulla oblongata, these same reflexes were evoked more easily and were stronger, that is, their implementation was facilitated. According to Magun, only the RF of the medulla oblongata can exert inhibitory influences on the reflexes of the spinal cord, while facilitating influences are regulated by the entire RF of the brainstem and spinal cord.

Rising influences RF to the cerebral cortex increases its tone, regulates the excitability of its neurons, without changing the specificity of responses to adequate stimulation. RF affects the functional state of all sensory areas of the brain, therefore, it is important in the integration of sensory information from different analyzers.

The reticular formation is directly related to the regulation of the wakefulness-sleep cycle. Stimulation of some RF structures leads to the development of sleep, stimulation of others causes awakening. G. Magun and J. Moruzzi put forward the concept according to which all types of signals coming from peripheral receptors reach the RF collaterals of the medulla oblongata and the pons, where they switch to neurons that give ascending pathways to the thalamus and then to the cerebral cortex.

Excitation of the RF of the medulla oblongata or pons causes synchronization of the activity of the cerebral cortex, the appearance of slow rhythms in the electroencephalogram, and sleep inhibition. The same state of the brain (sleeping brain) is observed when the ascending pathways of the reticular formation are damaged.

Excitation of the midbrain RF causes the opposite effect of awakening; desynchronization of the electrical activity of the cortex, the appearance of fast low-amplitude (b-rhythm) in the electroencephalogram. Hence, the most important function ascending RF is the regulation of the sleep-wake cycle.

The activation reaction of the cerebral cortex is observed upon stimulation of the RF of the medulla oblongata, midbrain, and diencephalon. At the same time, irritation of some nuclei of the thalamus leads to the emergence of limited local areas of excitation, and not to its general excitation, as happens with irritation of other parts of the Russian Federation.

Material from Wikipedia - the free encyclopedia

Anatomy

This elongated sausage-shaped formation extends in the tegmentum of the cerebral peduncle from the hypothalamus of the diencephalon to the inferior colliculus, where it begins an important descending tract, tractus rubrospinal, connecting the red nucleus with the anterior horns of the spinal cord. This bundle, after leaving the red nucleus, intersects with a similar bundle of the opposite side in the ventral part of the median suture - the ventral decussation of the tegmentum. The red core contains a pigment that includes iron, which gives it a specific color.

Physiology

Nucleus ruber is a very important coordination center of the extrapyramidal system, connected with its other parts. Fibers from the cerebellum pass to it as part of the upper peduncles of the latter after their decussation under the roof of the midbrain, ventral from aqueductus cerebri, as well as from pallidum- the lowest and most ancient of the subcortical nodes of the brain that are part of the extrapyramidal system. Thanks to these connections, the cerebellum and the extrapyramidal system, through the red nucleus and the tractus rubrospinal extending from it, influence the entire skeletal muscle in the sense of regulating unconscious automatic movements. The red nucleus has projections to the motor nuclei of the spinal cord, which controls the movement of the fore and hind limbs and is under the control of the cerebral cortex. Nucleus ruber- an important intermediate authority for integrating the influences of the forebrain and cerebellum in the formation of motor commands to spinal cord neurons.

Participation in the corticorubral tract

The red nucleus receives a large number of nerve fibers directly from the primary motor cortex through the corticorubral tract, as well as many collaterals from the corticospinal tract as it passes through the midbrain. These fibers form synapses in the lower, magnocellular (magnocellular) part of the red nucleus, where large neurons are located, similar in size to Betz cells in the motor cortex. These neurons give rise to the rubrospinal tract, which crosses the opposite side in the lower part of the brainstem and descends into the lateral columns of the spinal cord, following in close proximity to and anterior to the corticospinal tract.

Pathophysiology

When the red nucleus and its pathways are damaged, the animal develops so-called decerebrate rigidity. When the red nucleus is damaged, various types of syndromes occur:

Claude's syndrome is an alternating syndrome with localization of a pathological focus in the tegmentum of the midbrain, caused by damage to the lower part of the red nucleus, through which the root passes III nerve, as well as dento-rubral connections passing through the superior cerebellar peduncle. On the side pathological process– signs of damage to the oculomotor nerve (ptosis upper eyelid, pupil dilation, divergent strabismus), and on opposite side– intention tremor, hemiataxia, muscle hypotonia. Described in 1912 by the French neurologist N. Claude.

Benedict's syndrome - (M. Benedict, 1835-1920, Austrian neurologist) alternating syndrome occurs when the midbrain is damaged at the level of the red nucleus and the cerebellar-rednuclear tract: a combination of oculomotor nerve palsy on the affected side with choreoathetosis and intentional tremors on the opposite side.

Write a review about the article "Red Core"

Notes

see also

Excerpt characterizing the Red Core