Posterior funiculi (synonyms: fasciculus gracilis, fasciculus cuneatus, thin and wedge-shaped bundles, Gaulle and Burdach bundles, dorsolemniscal system, loop system, medial lemniscus). Conducting pathways of proprioceptive sensitivity Gaulle and Burdach fascicles

Receptors are located in the subcutaneous tissue (exteroceptors), muscles, tendons, articular surfaces,

ligaments, fascia, periosteum (proprioceptors). Impulses are transmitted along sensitive fibers

spinal nerves to the cells of the spinal ganglia, representing

is the 1st neuron. The central processes of the axons of these cells enter the spinal cord as part of the posterior

roots and enter the posterior cord, forming

thin bunch (Gaull)(fasciculus gracilis) And wedge-shaped bundle (Burdacha)(fasciculus cuneatus). Axons

enter the posterior cord, starting from the lower segments spinal cord. Each subsequent bundle of axons

adjacent to the existing ones on the lateral side. Thus, the outer parts of the posterior funiculus

(wedge-shaped fasciculus) are occupied by axons of cells that carry out proprioceptive innervation of the chest,

neck and upper limbs. Axons occupying the inner part of the posterior funiculus (thin bundle),

carry proprioceptive impulses from

lower extremities and lower half of the torso. Bundles of axons ascend into the medulla oblongata and

end in the gracilis and cuneate nuclei (nucleus gracilis et nucleus cuneatus), where the 2nd neuron is located

conductive path. The axons of the cells of the thin and wedge-shaped nuclei arcuately bend forward and

medially at the level of the lower angle of the rhomboid fossa and in the interolive layer they pass to the opposite

side, forming a cross of the medial loops (decussatio lemniscorum medialium). Bunch of fibers

facing in the medial direction is called internal arcuate fibers

(fibrae arcuatae internae), which are the beginning of the medial loop (lemniscus medialis). They

rise through the tegmentum of the pons and midbrain to the thalamus, ending in its dorsolateral

kernels. The 3rd neuron of the pathway is localized in the nuclei of the thalamus; the processes of the neurons of these nuclei pass

as part of the thalamo-cortical pathway (fibrae thalamocorticales) through the posterior third of the posterior leg of the inner

capsules and end in the internal granular layer of the cortex of the postcentral gyrus (primary

cortical fields 1, 2, 3 - the core of the analyzer of general sensitivity) and the superior parietal lobule (secondary

cortical field 5). The described path is associated with the so-called epicritic sensitivity, that is

the ability to accurately localize irritations and their qualitative and quantitative assessment.

Part of the fibers of the 2nd neuron, upon exiting the gracilis and wedge-shaped nuclei, bends outward and divides

for two bundles. One bundle - posterior outer arcuate fibers (fibrae arcuatae externae posteriores)

It goes to the inferior cerebellar peduncle of its side and ends in the cortex of the cerebellar vermis.

The fibers of the other bundle are the anterior outer arcuate fibers (fibrae arcuatae externae anteriores)–

go ahead

pass to the opposite side, bend around the olive nucleus from the lateral side and also through

the inferior cerebellar peduncle are directed to the cortex of the cerebellar vermis. Front and rear external

arcuate fibers carry proprioceptive impulses to the cerebellum.

Transfer of irritations coming through the conductors of proprioceptive and cutaneous sensitivity to

efferent pathways occur at the spinal and cortical levels. Impulses in the spinal cord

switch from afferent fibers of the dorsal roots to motor cells of the anterior horn

directly or through interneurons located in the central intermediate substance and

in the anterior horn. Along the fibers of their own bundles (fasciculi propria) spread occurs

irritation to the gray matter of other segments, due to which the response can involve

many muscles.

In the cerebral cortex, incoming signals are analyzed and synthesized and programs are formed

actions that are transmitted from the posterior part of the hemisphere (parietal lobes) to the anterior part (frontal

lobe), where the motor pyramidal and extrapyramidal tracts originate.

Page 2

Anterior spinothalamic tract (tr. spinothalamicus anterior)

– slow-conducting tract of discrete tactile sensitivity (sense of touch, touch, pressure).

The first neurons (receptor) are located in the spinal ganglia and are represented by pseudounipolar cells. Their peripheral dendritic processes run as part of the spinal nerves and begin from specialized receptors - Meissner's bodies, Merkel discs, Vater-Pacini bodies, located in the skin. Afferent fibers of the Ad and Ag types depart from these receptors. The speed of impulse conduction is low - 8–40 m/s. The central processes of the first neurons as part of the dorsal roots enter the spinal cord and are divided in a T-shape into ascending and descending branches, from which many collaterals arise. The terminal branches and collaterals of most of the fibers end at the apex of the dorsal horn of the spinal cord in the cells of the jellylike substance (laminas I–III), which are the second neurons. Most of the axons of the first neurons of tactile sensitivity bypass the gray matter of the spinal cord and are directed to the brain stem as part of the thin and cuneate fasciculi of the spinal cord.

The axons of the second neurons, the bodies of which are located in the substantia pulposum, form a decussation, passing through the anterior white commissure to the opposite side, and the level of the decussion is located 2-3 segments above the entry point of the corresponding dorsal root. They are then sent to the brain as part of the lateral cords, forming the anterior spinothalamic tract. This pathway passes through the medulla oblongata, then through the pontine tegmentum, where it goes along with the fibers of the medial lemniscus through the midbrain tegmentum, and ends in the ventrobasal ganglia of the thalamus.

The axons of the third neurons pass as part of the thalamo-cortical tract through the posterior leg of the internal capsule, and as part of the corona radiata they reach the postcentral gyrus and the superior parietal lobule (somatosensory cortical areas SI and SII).

Thus, the anterior spinothalamic tract is the pathway for tactile sensitivity.

Posterior funiculi (synonyms: fasciculus gracilis, fasciculus cuneatus, thin and wedge-shaped bundles, Gaulle and Burdach bundles, dorsolemniscal system, system

loops, medial lemniscus)

The Gaulle and Burdach bundles are fast-conducting pathways of spatial cutaneous sensitivity (sense of touch, touch, pressure, vibration, body weight) and sense of position and movement (articular-muscular (kinesthetic) sense).

The first neurons of the thin and cuneate fasciculi are represented by pseudounipolar cells, the bodies of which are located in the spinal ganglia. Dendrites pass as part of the spinal nerves, starting with quickly adapting receptors of the scalp (Meissner's corpuscles, Vater-Pacini corpuscles) and receptors of the joint capsules. IN Lately the possibility of the participation of proprioceptors of muscles and tendons in the formation of a conscious proprioceptive sense is shown.

The central processes of pseudounipolar cells as part of the dorsal roots enter the spinal cord segment by segment in the region of the posterior lateral sulcus and, having given off collaterals to plates II–IV, go in an ascending direction as part of the posterior cords of the spinal cord, forming a medially located thin fasciculus of Gaulle and a laterally located wedge-shaped Burdach's bundle (Fig. 5).

Gaulle bun

conducts proprioceptive sensitivity from the lower extremities and the lower half of the body: from 19 lower spinal nodes, including 8 lower thoracic, 5 lumbar, 5 sacral and 1 coccygeal, and Burdach bundle

– from the upper torso, upper limbs and neck, corresponding to the 12 upper spinal nodes (8 cervical and 4 upper thoracic).

The Gaulle and Burdach bundles, without interruption or crossing in the spinal cord, reach the homonymous nuclei (thin and wedge-shaped), located in the dorsal sections medulla oblongata, and here they switch to the second neurons. The axons of the second neurons go to the opposite side, forming internal arcuate fibers (fibrae arcuatae internae) and, crossing the median plane, intersect with the same fibers of the opposite side, forming a decussation in the medulla oblongata between the olives. medial loop (decussatio lemniscorum)

External arcuate fibers (fibrae arcuatae externae) through the inferior cerebellar peduncles connect the loop system with the cerebellar cortex.

Next, the fibers follow through the tegmentum of the bridge, the tegmentum of the cerebral peduncles and reach the lateral nuclei of the thalamus (ventro-basal complex), where they switch to third neurons. In the pons, the spinothalamic tract (cutaneous sensory pathways of the neck, trunk and limbs) and the lemniscus join the medial lemniscus from the outside. trigeminal nerve, conducting cutaneous and proprioceptive sensitivity from the face.

Through the lower third of the posterior femur of the internal capsule, the loop system reaches the superior parietal lobule (5th, 7th cytoarchitectonic fields) and the postcentral gyrus of the cerebral cortex (SI).

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The conducting (descending and ascending) pathways are located at various points in the vicinity of the nuclei and roots of the cranial nerves. Knowledge of the spatial relationships between cranial nerves and pathways is of paramount importance for the topical diagnosis of a pathological focus.

Ascending Paths. The path of deep sensitivity. Gaulle and Burdach bundles - conductors of deep sensitivity in the spinal cord, reaching the lower part of the medulla oblongata, are called f. gracilis (delicate tuft) - continuation of Gaulle's tuft and f. cuneatus (wedge-shaped fascicle) is a continuation of the Burdach fascicle. Here they gradually end in the nuclei of these bundles. The axons of the nuclear cells, which are the second neuron of deep sensitivity, tractus bulbo-thalamicus, pass to the opposite side (sensitive chiasm) in the form of a median loop, reach the visual thalamus and from there go to the cerebral cortex. Damage to the area where these pathways cross can cause impairment of deep sensitivity on both sides, and sometimes depending on the involvement of certain fibers in the form of cross anesthesia (arm on one side, leg on the other). Involvement in pathological process loops at any level leads to disruption of deep sensitivity on the opposite half of the body.

The path of cutaneous sensitivity is located deep in the reticular formation. In the more oral parts of the hindbrain, this bundle is close to the medial lemniscus, with which it merges at the level of the midbrain. In practice, this means that damage to these levels already causes a violation of all types of sensitivity in the opposite half of the body.

The posterior direct cerebellar tract of Flegsig at the level of the medulla oblongata as part of the inferior cerebellar peduncle ends in the cerebellar vermis. On the periphery of the medulla oblongata, it stands out in the form of a roller and is located above the inferior olive. At this level, fibers from the posterior columns and vestibular nuclei join it.

In the depths of the reticular formation lies the crossed cerebellar tract of Govers. It is located between the olive and the rope body. Rising upward, the Govers' bundle through the pons reaches the superior cerebellar peduncle, within which it ends in the cerebellar vermis.

Descending Paths. The pyramidal tract in the midbrain is located in a compact bundle in the cerebral peduncle, occupying its middle third. At the base of the pons, pyramidal fibers lie in scattered small bundles, between which are the aforementioned pons own nuclei and corticopontine-cerebellar connections. In the remaining parts of the medulla oblongata, the pyramidal fibers again gather into two compact bundles on either side of the anterior cleft. Finally, at the border with the spinal cord, the pyramidal fibers cross into the spinal cord. Damage to the pyramidal tracts at the level of the entire brain stem above the chiasm causes central paralysis on the opposite half of the body with unilateral lesions and bilateral movement disorders with lesions of the pyramids on both sides. Damage to the brain stem is characterized by early bilateral involvement of the pyramids in the process. Damage to the pyramids at the base of the pons is distinguished by some features arising from what has been said about their location: incomplete hemiparesis, the prevalence of the disorder in one limb, and a combination of pyramidal signs with cerebellar disorders can occur here.

The presence of a pathological process in the area of ​​​​the decussation of the pyramids causes various combinations central paralysis, often bilateral, sometimes arranged in a peculiar way: paralysis of the arm on one side, paralysis of the leg on the other.

Tractus cortico-bulbaris s. cortico-nuclearis - the path from the cerebral cortex (lower parts of the anterior central gyrus) to the nuclei of the motor cranial nerves. Passing through the knee of the internal capsule, the corticobulbar tract is located in the cerebral peduncle medially from the main pyramidal fasciculus and then gradually ends in the nuclei of the motor cranial nerves at different levels of the brain stem.

The corticomontine tract starts from various parts of the cerebral cortex, mainly from the frontal lobe, and passes through the internal capsule and cerebral peduncle. In the latter, the corticomontine tract is located as follows: the frontopontine tract occupies the medial section, and the occipital-parietal-temporopontine tract occupies its lateral sections.

In the tegmentum of the midbrain, the fascicle of Monaco begins in the red nuclei. Upon exiting them, it makes a cross (Trout) and goes through the brain stem to the spinal cord. In the trunk it is located deep in the reticular formation. Along this path, impulses from the cerebellum and subcortical nodes are carried to the spinal cord.

The posterior longitudinal fasciculus begins in Darkshevich's nucleus and passes through the entire brain stem to the spinal cord. It contains ascending and descending fibers, connects different levels trunk with individual segments of the spinal cord. Through the posterior longitudinal fasciculus, communication is carried out between the nuclei of all oculomotor nerves, between them, the vestibular apparatus and the spinal cord. Involvement of the posterior system in the pathological process longitudinal beam in the brainstem causes a number of vestibular disorders.

Nystagmus. Depending on the level of damage to this system, the nature of nystagmus changes. When the caudal parts of the trunk are affected, the nystagmus is often rotatory in nature; when its middle parts are affected, it is horizontal; in the upper parts, it is vertical. There is often a violation of the act of convergence (insufficiency, and sometimes absence of convergence), varying degrees gaze paralysis. When the oral parts of the posterior longitudinal fasciculus system are involved in the process, vertical strabismus and upward gaze paresis are sometimes observed.

Dizziness occurs mainly when moving the eyes. IN clinical practice Of interest is a symptom known as the static phenomenon. If you put the patient in a position with his legs together and, gradually bringing the researcher’s finger closer to the eyes of the subject, force him to convert in this way eyeballs, then in the presence of this symptom the patient experiences dizziness, staggering, often backwards, sometimes combined with a feeling of Fear and paleness of the face.

Central bundle of ankylosing spondylitis. This path begins in the diencephalon, passes through the tegmentum of the entire brain stem and ends in the inferior olive of the hindbrain. The axons of the cells of the inferior olive pass to the opposite side and, as part of the inferior cerebellar peduncle, end in the cerebellar hemisphere.

The central tegmental bundle is therefore one of the most important connections of the extrapyramidal system with the cerebellum. When the central tegmental bundle is damaged in combination with damage to the inferior olive and the dentate nucleus of the cerebellum, in some cases myoclonic twitching of the soft palate, tongue, pharynx, and larynx are observed. Sometimes these myoclonic twitches, which are rhythmic in nature, also affect other muscles (intercostal muscles, neck muscles, etc.).

Conductor function The spinal cord is that ascending and descending tracts pass through it.

TO upward paths relate:

• the system of posterior cords (tender and wedge-shaped bundles), which are conductors of skin-mechanical sensitivity in;
• spinothalamic pathways along which impulses from receptors arrive to;
• spinocerebellar tracts (dorsal and ventral) are involved in conducting impulses coming from skin receptors and proprioceptors in.

TO descending paths relate:

• pyramidal, or corticospinal, tract;
• extrapyramidal tracts, including rubrospinal, reticulospinal, vestibulospinal tracts. These descending pathways provide the influence of the higher parts of the central nervous system on skeletal muscle function.

Signal functions

Nerve fibers of the spinal cord form its white matter and are used to conduct many signals from sensory receptors in the central nervous system, signals between neurons of the spinal cord itself and between neurons of the spinal and other parts of the central nervous system, as well as from neurons of the spinal cord to effector organs. A significant part of the spinal cord pathways consists of axons of so-called propriospinal neurons. The fibers of these neurons create connections between spinal segments and do not extend beyond the spinal cord.

The most well-known examples of the simplest neural networks conducting signals in the spinal cord and their use to control the work of effector organs are neural networks of somatic and autonomic reflexes. In the conduction of a signal (nerve impulse) initially arising in the receptor nerve ending, the sensory neuron and its fibers, intercalary and motor neurons take part.

The signal is not only carried by neurons within the segment in which they are located, but is processed and used to carry out a reflex response to receptor stimulation.

Signals arising in the receptors of the body surface, muscles, tendons, and internal organs are also transmitted to the overlying structures of the central nervous system but to the fibers of the cords (columns) of the spinal cord, called ascending (sensitive) pathways(Table 1). These pathways are formed by fibers (axons) of sensory neurons, the bodies of which are located in the spinal ganglia, and interneurons, the bodies of which are located in the dorsal horns of the spinal cord.

Table 1. Main ascending sensory pathways of the central nervous system

The course of fibers conducting signals from receptors of different sensitivity (modality) is not the same. For example, pathways from proprioceptors carry signals about the condition of muscles, tendons, and joints to the cerebellum and cerebral cortex. The fibers of this pathway are axons of sensory neurons of the spinal ganglia. Having entered the spinal cord through the dorsal roots, they, along the same side of the spinal cord (without crossing), as part of the thin and wedge-shaped fasciculi, ascend to the neurons of the medulla oblongata, where they end in the formation of a synapse and transmit information to the second afferent neuron of the pathway (Fig. 1 ).

This neuron carries the processed information along the axon passing to the opposite side to the neurons of the thalamic nuclei. After switching on the neurons of the thalamus, information about the state of the motor apparatus is transmitted to the neurons of the postcentral region of the cerebral cortex and is used to form sensations about the degree of muscle tension, the position of the limbs, the angle of flexion in the joints, passive movement, and vibration.

The thin bundle also contains some fibers from skin receptors that conduct information used to form conscious tactile sensitivity in the form of touch, pressure, and vibration.

Other spinal sensory pathways are formed by the axons of second afferent (intercalary) neurons, the bodies of which are located in the dorsal horns of the spinal cord. The axons of these neurons within their segment make a cross and by opposite side the spinal cord as part of the lateral spinothalamic tract go to the neurons of the thalamus.

Rice. 1. Diagram of the pathways from proprioceptors, tactile, temperature and pain receptors to the brain stem and cortex

This pathway contains fibers that conduct signals of pain and temperature sensitivity, as well as part of the fibers that conduct signals of tactile sensitivity (see Fig. 1).

The anterior and posterior spinocerebellar tracts also pass through the lateral funiculi. They conduct signals from proprioceptors to the cerebellum.

Signals along the ascending sensory pathways are also carried to the centers of the ANS, the reticular formation of the brain stem and other structures of the central nervous system.

The spinal cord neurons receive signals from neurons in higher brain structures. They follow the axons of nerve cells that form descending(mainly motor) pathways, used to control muscle tone, form posture and organize movements. The most important among them are the corticospinal (pyramidal), rubrospinal, reticulospinal, vestibulospinal and tectospinal tracts (Table 2).

Table 2. Main descending efferent pathways of the central nervous system

The corticospinal tract is divided into the lateral one, whose fibers run in the lateral cords of the white matter of the spinal cord, and the anterior one, in the anterior cords. The corticospinal tract is formed by the axons of pyramidal neurons of the motor areas of the cerebral cortex, which end with synapses mainly on interneurons of the spinal cord. A small part of the fibers of the lateral corticospinal tract ends in synapses directly on the a-motoneurons of the spinal cord, innervating the muscles of the hand and distal muscles of the limbs.

The rubrospinal, reticulospinal, vestibulospinal and tectospinal tracts are formed by the axons of neurons of the corresponding nuclei of the brain stem and are also called extrapyramidal. Along these pathways, efferent nerve impulses are carried primarily to interneurons and γ-motoneurons of the spinal cord, used to maintain muscle tone, posture and involuntary movements, performed due to congenital or acquired reflexes. Through these pathways, conditions are formed for the effective execution of voluntary movements initiated by the cerebral cortex.

Through the spinal cord, signals are carried from the higher centers of the ANS to the preganglionic neurons of the sympathetic nervous system, located in the lateral horns of its thoracolumbar region, and to the neurons of the parasympathetic nervous system, located in the sacral part of the spinal cord. Through these pathways of the spinal cord, the tone of the sympathetic nervous system and its influence on the functioning of the heart, the state of the lumen of blood vessels, and the work of gastrointestinal tract and others internal organs, as well as the parasympathetic nervous system and its effect on the functions of the pelvic organs.

Starting from the level of the intersection of the motor fibers of the corticospinal tract of the medulla oblongata to the level of the northwestern part of the cervical spinal cord, the spinal nucleus of the trigeminal nerve is located, to the neurons of which the axons of sensory neurons located in the trigeminal ganglion descend through the medulla oblongata. Through them, the nucleus receives signals from pain sensitivity of teeth, other tissues of the jaws and oral mucosa, pain, temperature and touch signals from the surface of the face, tissues of the eye and orbit.

The axons of the neurons of the spinal nucleus of the trigeminal nerve intersect and follow in the form of a diffuse bundle to the neurons of the thalamus and to the neurons of the reticular formation of the brain stem. With damage to the afferent fibers of the trigeminal tract and the spinal nucleus of the trigeminal nerve, a decrease or loss of pain and temperature sensitivity on the ipsilateral side of the face may be observed.

If the integrity of the pathways for conducting afferent and (or) efferent signals at the level of the spinal cord or other levels of the central nervous system is disrupted, a person decreases or loses a certain type of sensitivity and (or) movements. Knowing the morphological features of the structure of the intersection of the fibers of the pathways, it is possible, taking into account the nature of the disturbance of sensitivity and (or) movements, to establish the level of damage to the central nervous system that caused these disturbances.

Signals from the neurons of the locus coeruleus and the raphe nucleus of the brain stem are carried to the intercalary and motor tracts via descending pathways. They are used to control muscle activity associated with sleep and wakefulness states. Signals from neurons of the periaqueductal gray matter are carried to the interneurons of the spinal cord along descending pathways. These signals and the neurotransmitters released from the axons of these neurons are used to control pain sensitivity.

Gaulle and Burdach bundles (fasciculus gracilis, thin tuft; fasciculus cuneatus, wedge-shaped fasciculus) are systems of ascending fibers of the spinal cord, as part of the afferent three-neuron crossed path of conscious proprioceptive (conscious muscle-articular) sensitivity ( tr. gangliobulbothalamocorticalis), which conducts to the cerebral cortex perceptions related to determining the position of the body and its parts in space. This path is also called via columnae posterioris lemniscique medialis (English: posterior column - medial lemniscus pathway; PCML).

General information

The thin fascicle is named after the Swiss neuroanatomist Friedrich Goll (1829-1903), the wedge-shaped fascicle is named after the German physiologist Carl Friedrich Burdach (1776-1847).

Anatomy of Gaulle and Burdach bundles

The central processes of the first neurons - cells of the spinal ganglia, entering through the dorsal roots into the dorsal funiculi, rise higher and are pushed towards the median plane by newly entering fibers from higher lying segments of the body. All these fibers in the posterior cords of the spinal cord form two bundles, divided into cervical spine glial layer ( septum paramedianum): 1) lying more medially - a thin bundle and 2) located laterally - a wedge-shaped bundle.

Functions of Gaulle and Burdach beams

The first conducts sensitivity from 19 lower segments (1 coccygeal, 5 sacral, 5 lumbar and 8 lower thoracic) and consists of longer conductors coming from lower limb and caudal to the part of the body of the corresponding side. The second consists of fibers from 12 upper segments (4 upper thoracic and 8 cervical), that is, from the upper part of the body and the corresponding upper limb. Thus, below the 4th thoracic segment in the posterior funiculi there are only Gaulle's bundles.

The first neurons of this pathway lie in the spinal ganglion, ganglion spinale. Both bundles along their path are connected by collaterals with the gray matter and end in special nuclei of the medulla oblongata - nucll.gracilis et cuneatus. This part of the tract is called tr. gangliobulbaris. The bodies of the second neurons are located in the indicated nuclei of the medulla oblongata. Their axons cross ( decussatio lemniscorum) and included lemniscum medialis pass through the bridge, midbrain and end in the lateral nuclei of the thalamus. This part of the tract is called tr.bulbothalamicus. The bodies of third neurons lie in the lateral nuclei of the thalamus. Their axons pass through the middle third of the posterior femur of the internal capsule and terminate in the somatosensory cortex of the postcentral gyrus. This part of the tract is called tr.thalamocorticalis.

Clinical significance

Damage to the Gaulle and Burdach bundles can lead to permanent loss of sensation in the limbs - Brown-Séquard syndrome.