Nervous system. Brain and nerves. Wireless technology has made it possible to reconnect the broken parts of the nervous system

PATHWAYS OF THE BRAIN AND SPINAL CORD

Conductive pathways called bundles of functionally homogeneous nerve fibers that connect various centers in the central nervous system, occupy a certain place in the white matter of the brain and spinal cord and conduct identical impulses.

Impulses that occur when exposed to receptors are transmitted through the processes of neurons to their bodies. Due to numerous synapses, neurons contact each other, forming chains along which nerve impulses propagate only in a certain direction - from receptor neurons through intercalary neurons to effector neurons. This is due to the morphofunctional features of synapses that conduct excitation (nerve impulses) in only one direction - from the presynaptic membrane to the postsynaptic one.

In one chain of neurons, the impulse propagates centripetally- from the place of origin in the skin, mucous membranes, organs of movement, vessels to the spinal cord or brain. In other circuits of neurons, the impulse is conducted centrifugally from the brain to the periphery to the working organs - muscles and glands. The processes of neurons are sent from the spinal cord to various structures of the brain, and from them in the opposite direction.

Rice. 44. Location of bundles of associative fibers of the white matter of the right hemisphere of the brain, medial surface (scheme): 1 - cingulate gyrus; 2 - upper longitudinal bundle; 3 - arcuate fibers of the large brain; 4 - lower longitudinal beam

direction - to the spinal cord and form bundles connecting the nerve centers. These bundles make up the pathways.

Three groups of nerve fibers (conducting pathways) are distinguished in the spinal cord and brain: associative, commissural, and projection.

Associative nerve fibers(short and long) connect groups of neurons (nerve centers) located in one half of the brain (Fig. 44). Short (intralobar) association pathways connect nearby areas of gray matter and are located, as a rule, within the same lobe of the brain. Among them are arcuate fibers of the cerebrum (fibrae arcuatae), which bend in an arcuate manner and connect the gray matter of adjacent gyri without going beyond the cortex (intracortical) or passing through the white matter of the hemisphere (extracortical). Long (interlobar) associative bundles connect areas of gray matter located at a considerable distance from each other, usually in different lobes. These include superior longitudinal bundle (fasciculus longitudinalis superior), passing in the upper layers of the white matter of the hemisphere and connecting the cortex of the frontal lobe with the parietal and occipital;

lower longitudinal bundle (fasciculus longitudinalis inferior), lying in the lower layers of the white matter of the hemisphere and connecting the gray matter of the temporal lobe with the occipital, and hook-shaped bundle (fasciculus uncipatus), connecting the cortex in the region of the frontal pole with the anterior part of the temporal lobe. The fibers of the uncinate bundle curve in an arcuate fashion around the islet.

In the spinal cord, association fibers connect neurons located in different segments to each other and form own bundles of the spinal cord(intersegmental bundles), which are located near the gray matter. Short bundles are thrown over 2-3 segments, long bundles connect segments of the spinal cord that are far apart from each other.

Commissural (commissural) nerve fibers connect the same centers (gray matter) of the right and left hemispheres of the large brain, forming the corpus callosum, the commissure of the fornix and the anterior commissure (Fig. 45). corpus callosum connects the new sections of the cerebral cortex of the right and left hemispheres. In each hemisphere, the fibers diverge fan-shaped, forming radiance of the corpus callosum (radiatio corporis callori). The anterior bundles of fibers, passing in the knee and beak of the corpus callosum, connect the cortex of the anterior sections of the frontal lobes, forming frontal forceps (forceps frontalis). These fibers, as it were, cover the anterior part of the longitudinal fissure of the brain on both sides. The cortex of the occipital and posterior sections of the parietal lobes of the large brain is connected by bundles of fibers passing in the ridge of the corpus callosum. They form the so-called occipital forceps (forceps occipitalis). Curving backwards, the bundles of these fibers, as it were, cover the posterior sections of the longitudinal fissure of the large brain. Fibers passing in the central parts of the corpus callosum connect the cortex of the central gyrus, parietal and temporal lobes of the cerebral hemispheres.

AT anterior commissure fibers pass that connect the sections of the cortex of the temporal lobes of both hemispheres, belonging to the olfactory brain. fibers adhesions of the fornix connect the gray matter of the hippocampus and temporal lobes of both hemispheres.

Projection nerve fibers(conducting paths) are divided into ascending and descending. Ascending connect the spinal cord with the brain, as well as the nuclei of the brain stem with the basal nuclei and the cortex of the cerebral hemispheres. Descending ones go in the opposite direction (Table 1).

Rice. 45. Commissural fibers (radiation) of the corpus callosum, dorsal view. The upper sections of the frontal, parietal and occipital lobes of the large brain are removed: 1 - frontal forceps (large forceps); 2 - corpus callosum; 3 - medial longitudinal strip; 4 - lateral longitudinal strip; 5 - occipital forceps

(small tongs)

Ascending projection pathways are afferent, sensitive. Nerve impulses that have arisen as a result of exposure to the body of various environmental factors, including impulses coming from the sense organs, the musculoskeletal system, internal organs and blood vessels, come through them to the cerebral cortex. Depending on this, the ascending projection pathways are divided into three groups: exteroceptive, proprioceptive and interoceptive pathways.

exteroceptive pathways carry impulses from the skin (pain, temperature, touch and pressure), from the senses (sight, hearing, taste, smell). Conducting path of pain and temperature sensitivity (lateral spinothalamic path, tractus spinothalamicus lateralis) consists of three neurons (Fig. 46). The receptors of the first (sensitive) neurons that perceive these stimuli are located in the skin and mucous membranes, and the cell bodies lie in the spinal nodes. The central processes in the composition of the posterior root are sent to the posterior horn of the spinal cord and end in synapses on the cells of the second neurons. All axons of the second neurons, whose bodies lie in the posterior horn, pass through the anterior gray commissure to the opposite side of the spinal cord, enter the lateral funiculus, are included in the lateral spinothalamic pathway, which rises to the medulla oblongata (behind the nucleus of the olive), passes in the tire bridge and in the tire of the midbrain, passing at the outer edge of the medial loop. Axons terminate, forming synapses on cells located in the posterolateral nucleus of the thalamus (the third neuron). The axons of these cells pass through the posterior leg of the internal capsule and as part of fan-shaped divergent bundles of fibers forming l clean crown (corona radiata), sent to the neurons of the internal granular plate of the cortex (layer IV) of the postcentral gyrus, where the cortical end of the general sensitivity analyzer is located. The fibers of the third neuron of the sensitive (ascending) pathway connecting the thalamus with the cortex form thalamocortical bundles (fasciculi thalamocorticales)- thalamoparietal fibers (fibrae thalamoparietales). The lateral spinothalamic pathway is a completely crossed pathway (all fibers of the second neuron pass to the opposite side), therefore, if one half of the spinal cord is damaged, pain and temperature sensitivity on the opposite side of the injury completely disappear.

The conductive path of touch and pressure (anterior spinothalamic path, tractus spinothalamicus anterior) carries impulses from the skin where they lie

Table 1. Pathways of the brain and spinal cord

Continuation of table 1.

Table 1 continued

End of table 1.

Rice. 46. Pathways of pain and temperature sensitivity,

touch and pressure (outline): 1- lateral spinothalamic pathway; 2 - anterior spinothalamic pathway; 3 - thalamus; 4 - medial loop; 5 - cross section of the midbrain; 6 - cross section of the bridge; 7 - cross section of the medulla oblongata; 8 - spinal node; 9 - cross section of the spinal cord. Arrows show the direction of movement of nerve impulses

receptors, to the cells of the cortex of the postcentral gyrus. The bodies of the first neurons (pseudo-unipolar cells) lie in the spinal nodes. The central processes of these cells, as part of the posterior roots of the spinal nerves, are sent to the posterior horn of the spinal cord. The axons of the neurons of the spinal nodes form synapses with the neurons of the posterior horn of the spinal cord (second neurons). Most of the axons of the second neuron also pass to the opposite side of the spinal cord through the anterior commissure, enter the anterior funiculus, and in its composition follow up to the thalamus. Part of the fibers of the second neuron go in the posterior funiculus of the spinal cord and in the medulla oblongata join the fibers of the medial loop. The axons of the second neuron form synapses with the neurons of the posterolateral nucleus of the thalamus (the third neuron). The processes of the cells of the third neuron pass through the posterior leg of the internal capsule, then, as part of the radiant crown, they are sent to the neurons of the IV layer of the cortex of the postcentral gyrus (internal granular plate). Not all fibers that carry impulses of touch and pressure pass to the opposite side in the spinal cord. Part of the fibers of the pathway of touch and pressure goes as part of the posterior cation of the spinal cord (its side) together with the axons of the pathway of the proprioceptive sensitivity of the cortical direction. In this regard, when one half of the spinal cord is affected, the skin sense of touch and pressure on the opposite side does not disappear completely, like pain sensitivity, but only decreases. This transition to the opposite side is partially carried out in the medulla oblongata.

proprioceptive pathways conduct impulses from muscles, tendons, joint capsules, ligaments. They carry information about the position of body parts in space, the volume of movements. Proprioceptive sensitivity allows a person to analyze their own complex movements and carry out their purposeful correction. Proprioceptive pathways of the cortical direction and proprioceptive pathways of the cerebellar direction are distinguished. Conducting pathway of proprioceptive sensitivity of the cortical direction carries impulses of muscular-articular feeling to the cortex of the postcentral gyrus of the brain (Fig. 47). Receptors of the first neurons located in muscles, tendons, articular capsules, ligaments, perceive signals about the state of the musculoskeletal system as a whole, muscle tone, the degree of stretching of the tendons, and send these signals along the spinal nerves to the bodies of the first neurons of this path, which lie in the spinal cord. nodes. body

Rice. 47. Pathway of proprioceptive sensation

cortical direction (scheme): 1 - spinal node; 2 - cross section of the spinal cord;

3 - posterior funiculus of the spinal cord;

4 - front outer arcuate fibers; 5 - medial loop; 6 - thalamus; 7 - cross section of the midbrain; 8 - cross section of the bridge; 9 - cross section of the medulla oblongata; 10 - rear outer arcuate fibers. The arrows show the direction of movement

nerve impulses

the first neuron of this pathway also lie in the spinal nodes. The axons of the first neurons in the posterior root, without entering the posterior horn, go to the posterior funiculus, where they form thin and wedge-shaped bundles.

Axons carrying proprioceptive impulses enter the posterior funiculus, starting from the lower segments of the spinal cord. Each next bundle of axons is adjacent from the lateral side to the existing bundles. Thus, the outer sections of the posterior cord (wedge-shaped bundle, Burdach's bundle) are occupied by axons of cells that carry out proprioceptive innervation in the upper thoracic, cervical sections of the body and upper limbs. Axons occupying the inner part of the posterior cord (thin bundle, Gaulle's bundle) conduct proprioceptive impulses from the lower extremities and the lower half of the trunk.

The fibers in the thin and wedge-shaped bundles go up to the medulla oblongata to the thin and wedge-shaped nuclei, where they end in synapses on the bodies of the second neurons. The axons of the second neurons emerging from these nuclei arcuately bend forward and medially, and at the level of the lower angle of the rhomboid fossa pass to the opposite side in the interstitial layer of the medulla oblongata, forming decussation of the medial loop (decussatio lemniscorum medialium). it internal arcuate fibers (fibrae arcuatae internae), which form the initial sections of the medial loop. Then the fibers of the medial loop pass upward through the tegmentum of the pons and the tegmentum of the midbrain, where they are located dorsal-lateral to the red nucleus. These fibers terminate in the dorsal lateral nucleus of the thalamus with synapses on the bodies of third neurons. The axons of the thalamus cells are directed through the posterior pedicle of the internal capsule as part of the radiant crown in cortex of the postcentral gyrus where they form synapses with neurons of the IV layer of the cortex (inner granular plate).

Another part of the fibers of the second neurons (posterior external arcuate fibers, efibrae arcueatae exteernae posteriores) upon exiting the thin and wedge-shaped nuclei, it goes to the lower cerebellar peduncle of its side and ends with synapses in the cortex of the worm. The third part of the axons of the second neurons (anterior external arcuate fibers, fibrae arcudtae extdrnae anterieores) passes to the opposite side and also through the lower cerebellar peduncle of the opposite side goes to the cortex of the worm. Proprioceptive impulses along these fibers go to the cerebellum to correct subconscious movements of the musculoskeletal system.

So, proprioceptive pathway the cortical direction is also crossed. The axons of the second neuron pass to the opposite side not in the spinal cord, but in the medulla oblongata. When damaged

of the spinal cord on the side of the occurrence of proprioceptive impulses (in case of brain stem injury - on the opposite side), the idea of ​​the state of the musculoskeletal system, the position of body parts in space is lost, and coordination of movements is disturbed.

There are proprioceptive pathways of the cerebellar direction - front and posterior spinal tracts, which carry information about the state of the musculoskeletal system and motor centers of the spinal cord to the cerebellum.

Posterior spinal tract(Flexig bundle) (tractus spinocerebellaris posterior)(Fig. 48) carries impulses from receptors located in muscles, tendons, joint capsules, ligaments to the cerebellum. body first neurons(pseudo-unipolar cells) are located in the spinal nodes. The central processes of these cells, as part of the posterior roots of the spinal nerves, are sent to the posterior horn of the spinal cord, where they form synapses with the neurons of the thoracic nucleus (Clark's column), which lies in the medial part of the base of the posterior horn. (second neurons). The axons of the second neurons pass in the back of the lateral

Rice. 48. Posterior spinocerebellar pathway:

1 - cross section of the spinal cord; 2 - cross section of the medulla oblongata; 3 - cerebellar cortex; 4 - dentate nucleus; 5 - spherical nucleus; 6 - synapse in the cortex of the cerebellar vermis; 7 - lower cerebellar peduncle; 8 - dorsal (posterior) spinal tract; 9 - spinal node

the funiculus of the spinal cord of its side, rise up and through the lower cerebellar peduncle go to the cerebellum, where they form synapses with the cells of the cortex of the cerebellar vermis (posterior-lower sections).

Anterior spinocerebellar pathway (Govers bundle) (tractus spinocerebellaris anterior)(Fig. 49) also carries impulses from receptors located in muscles, tendons, joint capsules to the cerebellum. These impulses along the fibers of the spinal nerves, which are peripheral processes of pseudo-unipolar cells of the spinal nodes (first neurons), are sent to the posterior horn, where they form synapses with neurons of the central intermediate (gray) substance of the spinal cord (second neurons). The axons of these fibers pass through the anterior gray commissure to the opposite side into the anterior part of the lateral funiculus of the spinal cord and rise upward. At the level of the isthmus of the rhomboid brain, these fibers form a second decussation, return to their side and through the superior cerebellar peduncle enter the cerebellum to the cells of the anterior-superior cortex of the worm

Rice. 49. Anterior spinal cerebellar pathway: 1 - transverse section of the spinal cord; 2 - anterior spinal tract; 3 - cross section of the medulla oblongata; 4 - synapse in the cortex of the cerebellar vermis; 5 - spherical nucleus; 6 - cerebellar cortex; 7 - dentate nucleus; 8 - spinal node

cerebellum. Thus, the anterior spinal cerebellar tract, complex and doubly crossed, returns to the same side on which the proprioceptive impulses arose. Proprioceptive impulses that have entered the cortex of the worm along the spinal-cerebellar proprioceptive pathways are transmitted to the red nuclei and through the dentate nucleus to the cerebral cortex (into the postcentral gyrus) along the cerebellar-thalamic and cerebellar-tegmental pathways (Fig. 50).

It is possible to trace the fiber systems along which the impulse from the cortex of the worm reaches the red nucleus, the cerebellar hemisphere, and even the overlying parts of the brain - the cerebral cortex. From the cortex of the worm, through the corky and spherical nuclei, the impulse through the superior cerebellar peduncle is directed to the red nucleus of the opposite side (cerebellar-tegmental path). The cortex of the worm is connected by associative fibers with the cortex of the cerebellar hemisphere, from where impulses enter the dentate nucleus of the cerebellum.

With the development of higher centers of sensitivity and voluntary movements in the cortex of the cerebral hemispheres, connections between the cerebellum and the cortex also arose, through the thalamus. Thus, from the dentate nucleus, the axons of its cells through the superior cerebellar peduncle exit into the tegmentum pons, pass to the opposite side and go to the thalamus. Switching in the thalamus to the next neuron, the impulse follows in the cerebral cortex, in the postcentral gyrus.

Interoceptive pathways conduct impulses from internal organs, vessels, body tissues. Their mechano-, baro-, chemoreceptors perceive information about the state of homeostasis (the intensity of metabolic processes, the chemical composition of tissue fluid and blood, pressure in the vessels, etc.).

Impulses enter the cortex of the cerebral hemispheres along direct ascending sensory pathways and from the subcortical centers.

From the cortex of the cerebral hemispheres and subcortical centers (from the nuclei of the brain stem), descending paths originate that control the motor functions of the body (voluntary movements).

Descending motor pathways conduct impulses to the underlying parts of the central nervous system - to the nuclei of the brain stem and to the motor nuclei of the anterior horns of the spinal cord. These paths are divided into pyramidal and extrapyramidal. Pyramidal pathways are the main avenues.

Rice. fifty. Cerebellar-thalamic and cerebellar-tegmental conduction

1 - cerebral cortex; 2 - thalamus; 3 - cross section of the midbrain; 4 - red core; 5 - cerebellar-thalamic path; 6 - cerebellar-cover path; 7 - globular nucleus of the cerebellum; 8 - cerebellar cortex; 9 - dentate nucleus; 10 - cork nucleus

Through the consciously controlled motor nuclei of the brain and spinal cord, they carry impulses from the cerebral cortex to the skeletal muscles of the head, neck, trunk, and limbs. carry impulses from the subcortical centers and various parts of the cortex also to the motor and other nuclei of the cranial and spinal nerves.

main motor, or pyramidal pathway is a system of nerve fibers through which arbitrary motor impulses from the pyramidal form of neurocytes (Betz pyramidal cells) located in the cortex of the precentral gyrus (layer V) are sent to the motor nuclei of the cranial nerves and to the anterior horns of the spinal cord, and from them to the skeletal muscles . Depending on the direction and location of the fibers, the pyramidal tract is divided into the cortical-nuclear tract, which goes to the nuclei of the cranial nerves, and the cortical-spinal tract. In the latter, the lateral and anterior cortical-spinal (pyramidal) pathways leading to the nuclei of the anterior horns of the spinal cord are distinguished (Fig. 51).

Corticonuclear pathway(tractus corticonuclearis) is a bundle of axons of giant pyramidal cells located in the lower third precentral gyrus. The axons of these cells (first neuron) pass through the knee of the internal capsule, the base of the brain stem. Then the fibers of the cortical-nuclear pathway pass to the opposite side to motor nuclei of the cranial nerves: III and IV - in the midbrain; V, VI, VII - in the bridge; IX, X, XI and XII - in the medulla oblongata, where they end with synapses on their neurons (second neurons). The axons of the motor neurons of the cranial nerve nuclei leave the brain as part of the corresponding cranial nerves and are sent to the skeletal muscles of the head and neck. They control the conscious movements of the muscles of the head and neck.

Lateral and anterior corticospinal (pyramidal) pathways (tractus corticospinales (pyramidales) anterior et lateralis) control the conscious movements of the muscles of the trunk and limbs. They start from the pyramidal form of neurocytes (Betz cells) located in the V layer of the cortex of the middle and upper thirds of the precentral gyrus. (first neurons). The axons of these cells are sent to the internal capsule, pass through the anterior part of its posterior pedicle, behind the fibers of the cortical-nuclear pathway. Then the fibers through the base of the brain stem (lateral to the fibers of the cortical-nuclear pathway) pass

Rice. 51. Scheme of the pyramidal pathways:

1 - precentral gyrus; 2 - thalamus; 3 - cortical-nuclear pathway; 4 - cross section of the midbrain; 5 - cross section of the bridge; 6 - cross section of the medulla oblongata; 7 - cross of pyramids; 8 - lateral cortical-spinal tract; 9 - cross section of the spinal cord; 10 - anterior cortical-spinal path. Arrows show the direction of movement of nerve impulses

across the bridge to the pyramid of the medulla oblongata. At the border of the medulla oblongata with the spinal cord, part of the fibers of the corticospinal tract passes to the opposite side at the border of the medulla oblongata with the spinal cord. The fibers then continue into the lateral funiculus of the spinal cord. (lateral corticospinal pathway) and gradually end in the anterior horns of the spinal cord with synapses on the motor cells (radicular neurocytes) of the anterior horns (second neuron).

The fibers of the cortical-spinal pathway, which do not cross to the opposite side at the border of the medulla oblongata with the spinal cord, descend down as part of the anterior funiculus of the spinal cord, forming anterior cortico-spinal tract. These fibers pass segmentally to the opposite side through the white commissure of the spinal cord and end in synapses on the motor (radicular) neurocytes of the anterior horn of the opposite side of the spinal cord. (second neurons). The axons of the cells of the anterior horns exit the spinal cord as part of the anterior roots and, being part of the spinal nerves, innervate the skeletal muscles. So, all pyramidal pathways are crossed. Therefore, with unilateral damage to the spinal cord or brain, paralysis of the muscles of the opposite side develops, which are innervated from the segments located below the damage zone.

Extrapyramidal pathways have connections with the nuclei of the brain stem and with the cortex of the cerebral hemispheres, which controls the extrapyramidal system. The influence of the cerebral cortex is carried out through the cerebellum, red nuclei, the reticular formation associated with the thalamus and the striatum, through the vestibular nuclei. One of the functions of the red nuclei is to maintain muscle tone, which is necessary to involuntarily keep the body in balance. The red nuclei, in turn, receive impulses from the cerebral cortex, from the cerebellum. From the red nucleus, nerve impulses are sent to the motor nuclei of the anterior horns of the spinal cord (red nuclear spinal cord) (Fig. 52).

Red nuclear-spinal tract (tractus rubrospinalis) maintains skeletal muscle tone and controls automatic habitual movements. First neurons of this path lie in the red nucleus of the midbrain. Their axons cross over to the opposite side in the midbrain (Forel's chiasm), pass through the tegmentum pedunculi,

Rice. 52. Red nuclear-spinal pathway (scheme): 1 - section of the midbrain; 2 - red core; 3 - red nuclear-spinal path; 4 - cerebellar cortex; 5 - dentate nucleus of the cerebellum; 6 - section of the medulla oblongata; 7 - section of the spinal cord. The arrows show the direction of movement

nerve impulses

pontine tegmentum and medulla oblongata. Next, the axons follow as part of the lateral funiculus of the spinal cord of the opposite side. The fibers of the red nuclear-spinal tract form synapses with the motor neurons of the nuclei of the anterior horns of the spinal cord (second neurons). The axons of these cells are involved in the formation of the anterior roots of the spinal nerves.

Predverno-spinal tract (tractus vestibulospinalis, or Leventhal's bundle), maintains the balance of the body and head in space, provides adjusting reactions of the body in case of imbalance. First neurons this path lies in the lateral nucleus (Deiters) and the lower vestibular nucleus of the medulla oblongata and bridge (predvernocochlear nerve). These nuclei are connected to the cerebellum and the posterior longitudinal fasciculus. The axons of the neurons of the vestibular nuclei pass in the medulla oblongata, then as part of the anterior cord of the spinal cord at the border with the lateral cord (of its own side). The fibers of this pathway form synapses with the motor neurons of the nuclei of the anterior horns of the spinal cord (second neurons), the axons of which are involved in the formation of the anterior (motor) roots of the spinal nerves. Posterior longitudinal bundle (fasciculus longitudinalis posterior), in turn, is associated with the nuclei of the cranial nerves. This ensures that the position of the eyeball is maintained during movements of the head and neck.

Reticulo-spinal tract (tractus reticulospinalis) maintains the tone of skeletal muscles, regulates the state of the spinal autonomic centers. First neurons of this path lie in the reticular formation of the brain stem (the intermediate nucleus of Cajal, the nucleus of the epithalamic (posterior) commissure of Darkshevich, etc.). The axons of the neurons of these nuclei pass through the midbrain, bridge, medulla oblongata. The axons of the neurons of the intermediate nucleus (Cajal) do not cross, they pass as part of the anterior funiculus of the spinal cord of their side. The axons of the cells of the nucleus of the epithalamic commissure (Darshkevich) pass to the opposite side through the epithalamic (posterior) commissure and go as part of the anterior funiculus of the opposite side. The fibers form synapses with the motor neurons of the nuclei of the anterior horns of the spinal cord. (second neurons).

Covering-spinal path (tractus tectospinalis) connects the quadrigemina with the spinal cord, transmits the influence of the subcortical centers of vision and hearing on the tone of skeletal muscles, and participates in the formation of protective reflexes. First neurons lie in the nuclei of the upper

and inferior colliculi of the quadrigemina of the midbrain. The axons of these cells pass through the pons, the medulla oblongata, pass to the opposite side under the aqueduct of the brain, forming a fountain-like, or Meynertian, cross. Further, the nerve fibers pass as part of the anterior funiculus of the spinal cord of the opposite side. The fibers form synapses with the motor neurons of the nuclei of the anterior horns of the spinal cord. (second neurons). Their axons are involved in the formation of the anterior (motor) roots of the spinal nerves.

Cortico-cerebellar pathway (tractus corticocerebellaris) controls the functions of the cerebellum, which is involved in the coordination of movements of the head, trunk and limbs. First neurons of this path lie in the cortex of the frontal, temporal, parietal and occipital lobes of the brain. Axons of frontal lobe neurons (frontal bridge fibers- Arnold's bundle) are sent to the internal capsule and pass through its anterior leg. Axons of neurons of the temporal, parietal and occipital lobes (parietal-temporal-occipital-bridge fibers- Türk's bundle) pass as part of the radiant crown, then through the posterior leg of the internal capsule. All fibers follow through the base of the brain stem to the bridge, where they end in synapses on the neurons of the own nuclei of the bridge of their side (second neurons). The axons of these cells pass to the opposite side in the form of transverse fibers of the bridge, then, as part of the middle cerebellar peduncle, they follow into the cerebellar hemisphere of the opposite side.

Thus, the pathways of the brain and spinal cord establish connections between afferent and efferent (effector) centers, close complex reflex arcs in the human body. Some reflex paths close on the nuclei that lie in the brain stem and provide functions with a certain automatism, without the participation of consciousness, although under the control of the cerebral hemispheres. Other reflex pathways are closed with the participation of the functions of the cerebral cortex, the higher parts of the central nervous system and provide arbitrary actions of the organs of the apparatus of movement.

The human spinal cord is the most important organ of the central nervous system, which communicates all organs with the central nervous system and conducts reflexes. It is covered on top with three shells:

• solid, cobweb and soft

Between the arachnoid and soft (vascular) membrane and in its central canal is located cerebrospinal fluid (liquor)

AT epidural space (the gap between the dura mater and the surface of the spine) - blood vessels and adipose tissue

The structure and functions of the human spinal cord

What is the external structure of the spinal cord?

This is a long cord in the spinal canal, in the form of a cylindrical cord, about 45 mm long, about 1 cm wide, flatter in front and behind than on the sides. It has conditional upper and lower bounds. The upper one starts between the line of the foramen magnum and the first cervical vertebra: in this place the spinal cord is connected to the brain through the intermediate oblong. The lower one is at the level of 1-2 lumbar vertebrae, after which the cord takes on a conical shape and then “degenerates” into a thin spinal cord ( terminal) with a diameter of about 1 mm, which stretches to the second vertebra of the coccygeal region. The terminal thread consists of two parts - inner and outer:

• internal - about 15 cm long, consists of nervous tissue, intertwined with lumbar and sacral nerves and is located in the sac of the dura mater
• external - about 8 cm, starts below the 2nd sacral vertebra and stretches in the form of a connection of the hard, arachnoid and soft membranes to the 2nd coccygeal vertebra and fuses with the periosteum

The outer, hanging down to the coccyx terminal thread with nerve fibers intertwining it is very similar in appearance to a ponytail. Therefore, pain and phenomena that occur when the nerves are pinched below the 2nd sacral vertebra are often called cauda equina syndrome.

The spinal cord has thickenings in the cervical and lumbosacral regions. This finds its explanation in the presence of a large number of exiting nerves in these places, going to the upper as well as to the lower extremities:

1. Cervical thickening extends from the 3rd - 4th cervical vertebrae to the 2nd thoracic, reaching a maximum in the 5th - 6th
2. Lumbosacral - from the level of the 9th - 10th thoracic vertebrae to the 1st lumbar with a maximum in the 12th thoracic

Gray and white matter of the spinal cord

If we consider the structure of the spinal cord in cross section, then in the center of it you can see a gray area in the form of a butterfly opening its wings. This is the gray matter of the spinal cord. It is surrounded on the outside by white matter. The cellular structure of gray and white matter differs from each other, as well as their functions.

The gray matter of the spinal cord is composed of motor and interneurons.:

• motor neurons transmit motor reflexes
• intercalary - provide a connection between the neurons themselves

White matter is made up of so-called axons- nerve processes from which the fibers of the descending and ascending pathways are created.

Butterfly wings are narrower anterior horns gray matter, wider - rear. In the anterior horns are motor neurons, in the rear intercalary. Between the symmetrical side parts there is a transverse bridge made of brain tissue, in the center of which there is a canal that communicates with the upper part of the ventricle of the brain and is filled with cerebrospinal fluid. In some departments or even along the entire length in adults, the central canal may become overgrown.

Relative to this canal, to the left and to the right of it, the gray matter of the spinal cord looks like columns of a symmetrical shape, interconnected by anterior and posterior commissures:

• the anterior and posterior pillars correspond to the anterior and posterior horns in cross section
• side protrusions form a side pillar

Lateral protrusions are not present throughout their entire length, but only between the 8th cervical and 2nd lumbar segments. Therefore, the cross section in segments where there are no lateral protrusions has an oval or round shape.

The connection of symmetrical pillars in the anterior and posterior parts forms two furrows on the surface of the brain: the anterior, deeper, and the posterior. The anterior fissure ends with a septum adjoining the posterior border of the gray matter.

Spinal nerves and segments

To the left and right of these central furrows are located respectively anterolateral and posterolateral furrows through which the anterior and posterior filaments exit ( axons) that form the nerve roots. The anterior spine in its structure is motor neurons anterior horn. Rear, responsible for sensitivity, consists of intercalary neurons back horn. Immediately at the exit from the brain segment, both the anterior and posterior roots unite into one nerve or ganglion ( ganglion). Since there are two anterior and two posterior roots in each segment, in total they form two spinal nerve(one on each side). Now it is easy to calculate how many nerves the human spinal cord has.

To do this, consider its segmental structure. There are 31 segments in total:

• 8 - in the cervical region
• 12 - in the chest
• 5 - lumbar
• 5 - in the sacral
• 1 - in the coccygeal

This means that the spinal cord has a total of 62 nerves - 31 on each side.

The sections and segments of the spinal cord and the spine are not at the same level, due to the difference in length (the spinal cord is shorter than the spine). This should be taken into account when comparing the brain segment and the number of the vertebra during radiology and tomography: if at the beginning of the cervical region this level corresponds to the number of the vertebra, and in its lower part it lies one vertebra higher, then in the sacral and coccygeal regions this difference is already several vertebrae.

Two Important Functions of the Spinal Cord

The spinal cord performs two important functions − reflex and conductive. Each of its segments is associated with specific organs, ensuring their functionality. For example:

• Cervical and thoracic - communicates with the head, arms, chest organs, chest muscles
• Lumbar - organs of the gastrointestinal tract, kidneys, muscular system of the trunk
• Sacral region - pelvic organs, legs

Reflex functions are simple reflexes laid down by nature. For example:

• pain reaction - pull your hand away if it hurts.
• knee jerk

Reflexes can be carried out without the participation of the brain

This is proven by simple experiments on animals. Biologists conducted experiments with frogs, checking how they react to pain in the absence of a head: a reaction was noted to both weak and strong pain stimuli.

The conductive functions of the spinal cord consist in conducting an impulse along the ascending path to the brain, and from there - along the descending path in the form of a return command to some organ

Thanks to this conductive connection, any mental action is carried out:
get up, go, take, throw, pick up, run, cut off, draw- and many others that a person, without noticing, commits in his daily life at home and at work.

Such a unique connection between the central brain, the spinal cord, the entire CNS and all the organs of the body and its limbs, as before, remains a dream of robotics. Not a single, even the most modern robot is yet able to carry out even a thousandth of those various movements and actions that are subject to a bioorganism. As a rule, such robots are programmed for highly specialized activities and are mainly used in conveyor automatic production.

Functions of gray and white matter. To understand how these magnificent functions of the spinal cord are carried out, consider the structure of the gray and white matter of the brain at the cellular level.

The gray matter of the spinal cord in the anterior horns contains large nerve cells called efferent(motor) and are combined into five nuclei:

• central
• anterolateral
• posterolateral
• anteromedial and posterior medial

The sensory roots of the small cells of the posterior horns are specific cell processes from the sensory nodes of the spinal cord. In the posterior horns, the structure of the gray matter is heterogeneous. Most of the cells form their own nuclei (central and thoracic). The border zone of the white matter, located near the posterior horns, is adjacent to the spongy and gelatinous zones of the gray matter, the processes of the cells of which, together with the processes of small diffusely scattered cells of the posterior horns, form synapses (contacts) with the neurons of the anterior horns and between adjacent segments. These neurites are called anterior, lateral, and posterior proper bundles. Their connection with the brain is carried out with the help of white matter pathways. Along the edge of the horns, these bundles form a white border.

The lateral horns of the gray matter perform the following important functions:

• In the intermediate zone of gray matter (lateral horns) are sympathetic cells vegetative nervous system, it is through them that communication with internal organs is carried out. The processes of these cells are connected to the anterior roots
• Here is formed spinocerebellar path:
  At the level of the cervical and upper thoracic segments is reticular zone - a bundle of a large number of nerves associated with zones of activation of the cerebral cortex and reflex activity.

The segmental activity of the gray matter of the brain, the posterior and anterior roots of the nerves, the own bundles of white matter, bordering the gray, is called the reflex function of the spinal cord. The reflexes themselves are called unconditional, according to the definition of Academician Pavlov.

The conductive functions of the white matter are carried out by means of three cords - its outer sections, limited by furrows:

• Anterior funiculus - the area between the anterior median and lateral grooves
• Posterior funiculus - between the posterior median and lateral grooves
• Lateral funiculus - between the anterolateral and posterolateral grooves

White matter axons form three conduction systems:

• short bundles called associative fibers that connect different segments of the spinal cord
• ascending sensitive (afferent) bundles directed to the parts of the brain
• descending motor (efferent) beams directed from the brain to the neurons of the gray matter of the anterior horns

Ascending and descending conduction pathways. Consider, for example, some functions of the paths of the cords of the white matter:

Anterior cords:

• Anterior pyramidal (cortical-spinal) tract- transmission of motor impulses from the cerebral cortex to the spinal cord (anterior horns)
• Spinothalamic anterior pathway- transmission of impulses of touch impact on the surface of the skin (tactile sensitivity)
• Covering-spinal tract-connecting the visual centers under the cerebral cortex with the nuclei of the anterior horns, creates a protective reflex caused by sound or visual stimuli
• Bundle of Geld and Leventhal (pre-door-spinal path)- fibers of the white matter connect the vestibular nuclei of eight pairs of cranial nerves with the motor neurons of the anterior horns
• Longitudinal posterior beam- connecting the upper segments of the spinal cord with the brain stem, coordinates the work of the eye muscles with the cervical, etc.

The ascending paths of the lateral cords conduct impulses of deep sensitivity (sensation of one's body) along the cortical-spinal, spinothalamic and tectospinal tracts.

Descending tracts of the lateral cords:

• Lateral corticospinal (pyramidal)- transmits the impulse of movement from the cerebral cortex to the gray matter of the anterior horns
• Red nuclear-spinal tract(located in front of the lateral pyramidal), the spinal cerebellar posterior and spinothalamic lateral pathways adjoin to it on the side.
  The red nuclear-spinal path carries out automatic control of movements and muscle tone at a subconscious level.

In different parts of the spinal cord, there is a different ratio of gray and white medulla. This is due to the different number of ascending and descending paths. There is more gray matter in the lower spinal segments. As you move up, it becomes less, and the white matter, on the contrary, is added, as new ascending paths are added, and at the level of the upper cervical segments and the middle part of the chest white - most of all. But in the area of ​​​​both cervical and lumbar thickenings, gray matter predominates.

As you can see, the spinal cord has a very complex structure. The connection of nerve bundles and fibers is vulnerable, and a serious injury or illness can disrupt this structure and lead to disruption of the conduction pathways, due to which there may be complete paralysis and loss of sensitivity below the “break” point of conduction. Therefore, at the slightest dangerous signs, the spinal cord must be examined and treated in time.

Puncture of the spinal cord

For the diagnosis of infectious diseases (encephalitis, meningitis, and other diseases), a puncture of the spinal cord (lumbar puncture) is used - leading a needle into the spinal canal. It is carried out in this way:
AT subarachnoid the space of the spinal cord at a level below the second lumbar vertebra, a needle is inserted and a fence is taken cerebrospinal fluid (liquor).
This procedure is safe, since the spinal cord is absent below the second vertebra in an adult, and therefore there is no threat of damage to it.

However, it requires special care not to bring infection or epithelial cells under the membrane of the spinal cord.

Spinal cord puncture is performed not only for diagnosis, but also for treatment, in such cases:

• injection of chemotherapy drugs or antibiotics under the lining of the brain
• for epidural anesthesia during operations
• for the treatment of hydrocephalus and reduction of intracranial pressure (removal of excess cerebrospinal fluid)

Spinal puncture has the following contraindications:

• spinal stenosis
• displacement (dislocation) of the brain
• dehydration (dehydration)

Take care of this important organ, do elementary prevention:

1. Take Antivirals During a Viral Meningitis Epidemic
2. Try not to have picnics in the forested area in May-early June (the period of activity of the encephalitis tick)

Spinal cord and spinal ganglion. Own apparatus of the spinal cord

Spinal cord(lat. Medulla spinalis) is an organ of the central nervous system of vertebrates located in the spinal canal. The spinal cord is protected soft, gossamer and dura mater. The spaces between the membranes and the spinal canal are filled with cerebrospinal fluid.

The spinal cord is located in the spinal canal and has the form of a rounded cord, expanded in the cervical and lumbar regions and penetrated by the central canal. It consists of two symmetrical halves, separated anteriorly by a median fissure, posteriorly by a median sulcus, and is characterized by a segmental structure; each segment is associated with a pair of anterior (ventral) and a pair of posterior (dorsal) roots. In the spinal cord, gray matter is located in its central part, and white matter lies along the periphery.

The gray matter is butterfly-shaped in cross section and includes paired anterior (ventral), posterior (dorsal), and lateral (lateral) horns (actually continuous columns running along the spinal cord). The horns of the gray matter of both symmetrical parts of the spinal cord are connected to each other in the region of the central gray commissure (commissure). The gray matter contains the bodies, dendrites and (partly) axons of neurons, as well as glial cells. Between the bodies of neurons there is a neuropil - a network formed by nerve fibers and processes of glial cells.

ganglion- an accumulation of nerve cells, consisting of bodies, dendrites and axons of nerve cells and glial cells. Usually the ganglion also has a sheath of connective tissue.

The spinal ganglia contain the bodies of sensory (afferent) neurons.

own apparatus spinal cord- this is the gray matter of the spinal cord with the posterior and anterior roots of the spinal nerves and with its own bundles of white matter bordering the gray matter, composed of associative fibers of the spinal cord. The main purpose of the segmental apparatus, as the phylogenetically oldest part of the spinal cord, is the implementation of innate reactions (reflexes).

The cerebral cortex or cortex(lat. cortex cerebri) - the structure of the brain, a layer of gray matter 1.3-4.5 mm thick, located along the periphery of the cerebral hemispheres, and covering them.

the molecular layer

outer granular layer

layer of pyramidal neurons

inner granular layer

ganglionic layer (inner pyramidal layer; Betz cells)

a layer of polymorphic cells

· The cerebral cortex also contains a powerful neuroglial apparatus that performs trophic, protective, supporting and delimiting functions.

The cerebellum is a part of the hindbrain, a brain structure that is one of the main regulators in controlling posture, body balance, in coordinating muscle tone and movements of the body and its parts.

The cerebellum is located in the posterior cranial fossa posterior (dorsal) to the pons and superior (dorsal) of the medulla oblongata. Above the cerebellum are the occipital lobes of the cerebral hemispheres. They are separated from the cerebellum by the transverse fissure of the cerebrum. The upper and lower surfaces of the cerebellum are convex. Its lower surface has a wide depression (valley of the cerebellum). The dorsal surface of the medulla oblongata is adjacent to this depression. In the cerebellum, two hemispheres and an unpaired middle part - the cerebellar vermis are distinguished. The upper and lower surfaces of the hemispheres and the vermis are indented by many transverse parallel fissures of the cerebellum. Between the fissures are long and narrow sheets (gyrus) of the cerebellum. Groups of convolutions, separated by deeper grooves, form the lobules of the cerebellum. The furrows of the cerebellum go, without interruption, through the hemispheres and through the vermis. In this case, each lobule of the worm corresponds to two (right and left) lobes of the hemispheres. A more isolated and phylogenetically old lobule of each of the hemispheres is a piece. It is adjacent to the ventral surface of the middle cerebellar peduncle. With the help of a long stem, the piece is connected to the cerebellar vermis, with its nodule.

The cerebellum is connected to neighboring parts of the brain by three pairs of legs. The inferior cerebellar peduncles (rope bodies) run downward and connect the cerebellum to the medulla oblongata. The middle peduncles of the cerebellum, the thickest, go anteriorly and pass into the bridge. The superior cerebellar peduncles connect the cerebellum to the midbrain. The cerebellar peduncles are made up of fibers of pathways that connect the cerebellum with other parts of the brain and with the spinal cord.

The hemispheres of the cerebellum and the vermis consist of white matter located inside and a thin plate of gray matter covering the white matter along the periphery - the cerebellar cortex. In the thickness of the leaves of the cerebellum, the white matter looks like thin white stripes (plates). Paired nuclei of the cerebellum lie in the white matter of the cerebellum.

The white matter of the worm, bordered by the bark and divided along the periphery by numerous deep and shallow grooves, on the sagittal section has a bizarre pattern resembling a tree branch, hence its name "tree of life".

The gray matter of the pons varolii, located next to the cerebellum, is represented by the nuclei of the V, VI, VII, VIII pairs of cranial nerves that provide eye movements, facial expressions, and the activity of the auditory and vestibular apparatus. In addition, the nuclei of the reticular formation and the proper nuclei of the bridge are located in the gray matter of the bridge. They form connections between the cerebral cortex and the cerebellum and transmit information from one part of the brain to another. In the dorsal parts of the bridge there are ascending sensitive pathways. In the ventral parts of the bridge - descending pyramidal and extrapyramidal paths. There are also fiber systems that provide two-way communication between the cerebral cortex and the cerebellum.

Cerebellar ataxia.

Cerebellar ataxia- this type of ataxia is associated with damage to the cerebellar systems. Taking into account that the cerebellar vermis is involved in the regulation of contraction of the muscles of the body, and the cortex of the hemispheres is involved in the distal extremities, two forms of cerebellar ataxia are distinguished:

static locomotor ataxia- damage to the cerebellar vermis (mainly stability and gait are upset) and

dynamic ataxia- primary lesion of the cerebellar hemispheres (the function of performing various voluntary movements of the limbs is impaired.

Damage to the cerebellum, especially its vermis (archi- and paleocerebellum), usually leads to a violation of body statics - 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 (support reaction), 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 (jump reaction). 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 slight push (pushing symptom).

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 person's torso is excessively straightened (Thoma's symptom). 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.

Dynamic cerebellar ataxia is manifested by clumsiness of limb movements, which is especially pronounced with movements that require precision. To identify dynamic ataxia, a number of coordination tests are performed.

When questioning patients, it is important to find out whether ataxia increases in the dark. In contrast to cerebellar ataxia, in sensory and vestibular ataxia, symptoms increase in conditions of poor visibility. However, an increase in the severity of ataxia when closing the eyes, which is characteristic of sensitive ataxia, is also noted in cerebellar lesions, although to a much lesser extent. Visual information affects the accuracy and timing of fine movements performed by patients with cerebellar disorders.

To control the work of the whole organism or each individual organ, the motor apparatus, the pathways of the spinal cord are required. Their main task is to deliver impulses sent by the human "computer" to the body and limbs. Any failure in the process of sending or receiving impulses of a reflex or sympathetic nature is fraught with serious pathologies of health and all life activity.

What are pathways in the spinal cord and brain?

The pathways of the brain and spinal cord act as a complex of neural structures. In the course of their work, impulse impulses are sent to specific areas of gray matter. In essence, impulses are signals that prompt the body to act on the call of the brain. Several groups, different in accordance with functional characteristics, represent the pathways of the spinal cord. These include:

• projection nerve endings;
• associative paths;
• commissural connecting roots.

In addition, the performance of the spinal conductors necessitates the selection of the following classification, according to which they can be:

• motor;
• sensory.

Sensitive perception and human motor activity

Sensory or sensory pathways of the spinal cord and brain serve as an indispensable element of contact between these two most complex systems in the body. They also send an impulsive message to every organ, muscle fiber, arms and legs. The instantaneous sending of an impulse signal is a fundamental moment in the implementation by a person of coordinated coordinated body movements performed without the application of any conscious effort. Impulses sent by the brain can be recognized by nerve fibers through touch, pain, body temperature, and joint-muscular motility.

The motor pathways of the spinal cord predetermine the quality of a person's reflex reaction. Providing the sending of impulse signals from the head to the reflex endings of the ridge and the muscular apparatus, they endow a person with the ability to self-control motor skills - coordination. Also, these pathways are responsible for the transmission of stimulating impulses towards the visual and auditory organs.

Where are the pathways located?

Having become acquainted with the anatomical distinguishing features of the spinal cord, it is necessary to figure out where the very pathways of the spinal cord are located, because this term implies a lot of nerve matter and fibers. They are located in specific vital substances: gray and white. Connecting the spinal horns and the cortex of the left and right hemispheres, the pathways through neural connections provide contact between these two departments.

The functions of conductors of the main human organs are to implement the intended tasks with the help of specific departments. In particular, the pathways of the spinal cord are located within the upper vertebrae and head, which can be described in more detail as follows:

1. Associative connections are a kind of "bridges" that connect the areas between the cortex of the hemispheres and the nuclei of the spinal substance. In their structure there are fibers of various sizes. Relatively short ones do not go beyond the hemisphere or its brain lobe. Longer neurons transmit impulses that travel some distance to the gray matter.
2. The commissural tracts are a body with a calloused structure and perform the task of connecting the newly formed sections in the head and spinal cord. The fibers from the main lobe bloom in a ray-like manner, they are placed in the white spinal substance.
3. Projection nerve fibers are located directly in the spinal cord. Their performance makes it possible for impulses to arise in the hemispheres in a short time and establish communication with internal organs. The division into ascending and descending pathways of the spinal cord concerns precisely fibers of this type.

System of ascending and descending conductors

The ascending pathways of the spinal cord fill the human need for vision, hearing, motor functions and their contact with important body systems. The receptors for these connections are located in the space between the hypothalamus and the first segments of the spinal column. The ascending pathways of the spinal cord are able to receive and send further impulses coming from the surface of the upper layers of the epidermis and mucous membranes, life-support organs.

In turn, the descending pathways of the spinal cord include the following elements in their system:

• The neuron is pyramidal (originates in the cortex of the hemispheres, then rushes down, bypassing the brain stem; each of its bundles is located on the spinal horns).
• The neuron is central (it is motor, connecting the anterior horns and the cortex of the hemispheres with the reflex roots; together with the axons, elements of the peripheral nervous system also enter the chain).
• Spinocerebellar fibers (conductors of the lower extremities and spinal column, including wedge-shaped and thin ligaments).

It is rather difficult for an ordinary person who does not specialize in the field of neurosurgery to understand the system represented by the complex pathways of the spinal cord. The anatomy of this department is indeed an intricate structure consisting of neural impulse transmissions. But it is thanks to her that the human body exists as a whole. Due to the double direction in which the conductive pathways of the spinal cord operate, instantaneous transmission of impulses is ensured, which carry information from the controlled organs.

Deep sensory conductors

The structure of the nerve cords, acting in an upward direction, is multi-component. These pathways of the spinal cord are formed by several elements:

• Burdach's bundle and Gaull's bundle (they are paths of deep sensitivity located on the back of the spinal column);
• spinothalamic bundle (located on the side of the spinal column);
• Govers' bundle and Flexig's bundle (cerebellar pathways located on the sides of the column).

Inside the intervertebral nodes are located a deep degree of sensitivity. The processes localized in the peripheral areas terminate in the most suitable muscle tissues, tendons, bone and cartilage fibers and their receptors.

In turn, the central processes of the cells, located behind, keep the direction towards the spinal cord. Conducting deep sensitivity, the posterior nerve roots do not go deep into the gray matter, forming only the posterior spinal columns.

Where such fibers enter the spinal cord, they are divided into short and long. Further, the pathways of the spinal cord and brain are sent to the hemispheres, where their cardinal redistribution takes place. Their main part remains in the zones of the anterior and posterior central gyri, as well as in the region of the crown.

It follows that these paths conduct sensitivity, thanks to which a person can feel how his muscular-articular apparatus works, feel any vibrational movement or tactile touch. Gaulle's bundle, located right in the center of the spinal cord, distributes sensation from the lower torso. Burdach's bundle is located above and serves as a conductor of the sensitivity of the upper limbs and the corresponding part of the trunk.

How to find out about the degree of sensory?

To determine the degree of deep sensitivity, you can use a few simple tests. For their implementation, the patient's eyes are closed. Its task is to determine the specific direction in which the doctor or researcher makes movements of a passive nature in the joints of the fingers, hands or feet. It is also desirable to describe in detail the posture of the body or the position that its limbs have assumed.

With the help of a tuning fork for vibration sensitivity, it is possible to examine the pathways of the spinal cord. The functions of this device will help to accurately determine the time during which the patient clearly feels the vibration. To do this, take the device and click on it to make a sound. At this point, it is necessary to put on any bony protrusion on the body. In the case when this sensitivity drops out earlier than in other cases, it can be assumed that the posterior pillars are affected.

The test for the sense of localization implies that the patient, by closing his eyes, accurately points to the place where the researcher touched him a few seconds before. A satisfactory indicator is considered if the patient made an error within one centimeter.

Sensory sensitivity of the skin

The structure of the pathways of the spinal cord allows you to determine the degree of skin sensitivity at the peripheral level. The fact is that the nerve processes of the protoneuron are involved in skin receptors. The processes located in the center as part of the posterior processes rush directly to the spinal cord, as a result of which the Lisauer zone is formed there.

Just like the path of deep sensitivity, the skin one consists of several successively combined nerve cells. In comparison with the spinothalamic bundle of nerve fibers, information impulses transmitted from the lower extremities or lower body are slightly higher and in the middle.

Skin sensitivity varies according to criteria based on the nature of the irritant. She happens:

• temperature;
• thermal;
• painful;
• tactile.

In this case, the last type of skin sensitivity, as a rule, is transmitted by conductors of deep sensitivity.

How to find out about pain threshold and temperature difference?

To determine the level of pain, doctors use the injection method. In the most unexpected places for the patient, the doctor inflicts several light injections with a pin. The patient's eyes should be closed, because. he must not see what is happening.

The temperature sensitivity threshold is easy to determine. In a normal state, a person experiences various sensations at temperatures, the difference of which was about 1-2 °. To detect a pathological defect in the form of a violation of skin sensitivity, doctors use a special apparatus - a thermoesthesiometer. If not, you can test for warm and hot water.

Pathologies associated with impaired conduction pathways

In the ascending direction, the pathways of the spinal cord are formed in a position due to which a person can feel tactile touch. For the study, it is necessary to take something soft, gentle and in a rhythmic manner conduct a subtle examination to identify the degree of sensitivity, as well as check the reaction of hairs, bristles, etc.

Disorders caused by skin sensitivity today are considered to be the following:

1. Anesthesia is the complete loss of sensation of the skin on a specific superficial area of ​​the body. In case of violation of pain sensitivity, analgesia occurs, in case of temperature - termanesthesia.
2. Hyperesthesia is the opposite of anesthesia, a phenomenon that occurs when the threshold of excitation decreases, and when it increases, hypalgesia appears.
3. Misperception of irritants (for example, the patient confuses cold and warm) is called dysesthesia.
4. Paresthesia is a violation, the manifestations of which can be a huge variety, ranging from crawling goosebumps, a feeling of electric shock and its passage through the entire body.
5. Hyperpathy is the most pronounced. It is also characterized by damage to the thalamus, an increase in the threshold of excitability, the inability to locally determine the stimulus, a severe psycho-emotional coloring of everything that happens, and too sharp a motor reaction.

Features of the structure of descending conductors

The descending pathways of the brain and spinal cord include several ligaments, including:

• pyramidal;
• rubro-spinal;
• vestibulo-spinal;
• reticulo-spinal;
• back longitudinal.

All of the above elements are the motor pathways of the spinal cord, which are components of the nerve cords in a downward direction.

The so-called begins from the largest cells of the same name located in the upper layer of the cerebral hemisphere, mainly in the zone of the central gyrus. The pathway of the anterior cord of the spinal cord is also located here - this important element of the system is directed downward and passes through several sections of the posterior femoral capsule. At the point of intersection of the medulla oblongata and spinal cord, an incomplete decussation can be found, forming a straight pyramidal bundle.

In the tegmentum of the midbrain there is a conducting rubro-spinal tract. It starts from the red nuclei. Upon exiting, its fibers cross and pass into the spinal cord through the varoli and medulla oblongata. Rubro-spinal path allows you to conduct impulses from the cerebellum and subcortical nodes.

The pathways of the spinal cord begin in Deiters' nucleus. Located in the brainstem, the vestibulo-spinal path continues in the spinal cord and ends in its anterior horns. The passage of impulses from the vestibular apparatus to the peripheral system depends on this conductor.

In the cells of the reticular formation of the hindbrain, the reticulo-spinal path begins, which is scattered in separate bundles in the white matter of the spinal cord, mainly from the side and front. In fact, this is the main connecting element between the reflex brain center and the musculoskeletal system.

The posterior longitudinal ligament is also involved in connecting motor structures to the brainstem. The work of the oculomotor nuclei and the vestibular apparatus as a whole depends on it. The posterior longitudinal bundle is located in the cervical spine.

Consequences of diseases of the spinal cord

Thus, the pathways of the spinal cord are vital connecting elements that provide a person with the ability to move and feel. The neurophysiology of these pathways is associated with the structural features of the spine. It is known that the structure of the spinal cord, surrounded by muscle fibers, has a cylindrical shape. Within the substances of the spinal cord, associative and motor reflex pathways control the functionality of all body systems.

In the event of a disease of the spinal cord, mechanical damage or malformations, the conductivity between the two main centers can be significantly reduced. Violations of the pathways threaten a person with a complete cessation of motor activity and loss of sensory perception.

The main reason for the lack of impulse conduction is the death of nerve endings. The most difficult degree of conduction disturbance between the brain and spinal cord is paralysis and lack of sensation in the limbs. Then there may be problems in the work of the internal organs associated with the brain with a damaged neural bundle. For example, disorders in the lower part of the spinal cord lead to uncontrolled urination and defecation processes.

Are diseases of the spinal cord and pathways treated?

Only the appeared degenerative changes are almost instantly reflected in the conductive activity of the spinal cord. Inhibition of reflexes leads to pronounced pathological changes due to the death of neuronal fibers. It is impossible to completely restore the disturbed conduction areas. The disease comes on rapidly and progresses at lightning speed, so gross conduction disturbances can be avoided only if medical treatment is started in a timely manner. The sooner this is done, the greater the chances of stopping pathological development.

The impermeability of the passing tracts of the spinal cord needs treatment, the primary task of which will be to stop the processes of the death of nerve endings. This can be achieved only if the factors that influenced the onset of the disease are suppressed. Only after that it is possible to start therapy in order to restore sensitivity and motor functions as much as possible.

Drug treatment is aimed at stopping the process of dying of brain cells. Their task is also to restore the disturbed blood supply to the damaged area of ​​the spinal cord. In the course of treatment, doctors take into account age characteristics, the nature and severity of damage and progression of the disease. In pathway therapy, it is important to maintain constant stimulation of nerve fibers with electrical impulses. This will help maintain satisfactory muscle tone.

Surgical intervention is carried out in order to restore the conductivity of the spinal cord, therefore, it is carried out in two directions:

1. Suppression of the causes of paralysis of the activity of neural connections.
2. Stimulation of the spinal cord for the speedy acquisition of lost functions.

The operation should be preceded by a complete medical examination of the whole body. This will allow to determine the localization of the processes of degeneration of nerve fibers. In the case of severe spinal injuries, the causes of compression must first be eliminated.