Topic 18. NERVOUS SYSTEM
With anatomical point of view The nervous system is divided into central (brain and spinal cord) and peripheral (peripheral nerve nodes, trunks and endings).
The morphological substrate of the reflex activity of the nervous system is reflex arcs, which are a chain of neurons of various functional significance, the bodies of which are located in different parts of the nervous system - both in the peripheral nodes and in the gray matter of the central nervous system.
With physiological point of view the nervous system is divided into somatic (or cerebrospinal), which innervates the entire human body, except for internal organs, vessels and glands, and autonomous (or autonomic), which regulates the activity of these organs.
Spinal nodes
The first neuron of each reflex arc is receptor nerve cell. Most of these cells are concentrated in the spinal nodes located along the posterior roots of the spinal cord. The spinal ganglion is surrounded by a connective tissue capsule. Thin layers of connective tissue penetrate from the capsule into the parenchyma of the node, which forms its skeleton, and blood vessels pass through it in the node.
The dendrites of the nerve cell of the spinal ganglion go as part of the sensitive part of the mixed spinal nerves to the periphery and end there with receptors. Neurites together form the posterior roots of the spinal cord, carrying nerve impulses either to the gray matter of the spinal cord, or along its posterior funiculus to the medulla oblongata.
The dendrites and neurites of the cells in the node and outside it are covered with membranes of lemmocytes. The nerve cells of the spinal ganglions are surrounded by a layer of glial cells, which are here called mantle gliocytes. They can be recognized by the round nuclei surrounding the body of the neuron. Outside, the glial sheath of the body of the neuron is covered with a delicate, fine-fibred connective tissue sheath. The cells of this membrane are characterized by an oval-shaped nucleus.
The structure of the peripheral nerves is described in the general histology section.
Spinal cord
It consists of two symmetrical halves, delimited from each other in front by a deep median fissure, and behind by a connective tissue septum.
The inner part of the spinal cord is darker - this is his Gray matter. On its periphery there is a lighter white matter. The gray matter on the cross section of the brain is seen in the form of a butterfly. The protrusions of the gray matter are called horns. Distinguish front, or ventral, rear, or dorsal, and lateral, or lateral, horns.
The gray matter of the spinal cord consists of multipolar neurons, non-myelinated and thin myelinated fibers, and neuroglia.
The white matter of the spinal cord is formed by a set of longitudinally oriented predominantly myelinated fibers of nerve cells.
The bundles of nerve fibers that communicate between different parts of the nervous system are called the pathways of the spinal cord.
In the middle part of the posterior horn of the spinal cord is the own nucleus of the posterior horn. It consists of bundle cells, the axons of which, passing through the anterior white commissure to the opposite side of the spinal cord into the lateral funiculus of the white matter, form the ventral spinocerebellar and spinothalamic pathways and go to the cerebellum and optic tubercle.
Interneurons are diffusely located in the posterior horns. These are small cells whose axons terminate within the gray matter of the spinal cord of the same (associative cells) or opposite (commissural cells) side.
The dorsal nucleus, or Clark's nucleus, consists of large cells with branched dendrites. Their axons cross the gray matter, enter the lateral funiculus of the white matter of the same side, and ascend to the cerebellum as part of the dorsal spinocerebellar tract.
The medial intermediate nucleus is located in the intermediate zone, the neurites of its cells join the ventral spinocerebellar tract of the same side, the lateral intermediate nucleus is located in the lateral horns and is a group of associative cells of the sympathetic reflex arc. The axons of these cells leave the spinal cord together with the somatic motor fibers as part of the anterior roots and separate from them in the form of white connecting branches of the sympathetic trunk.
The largest neurons of the spinal cord are located in the anterior horns, they also form nuclei from the bodies of nerve cells, the roots of which form the bulk of the fibers of the anterior roots.
As part of the mixed spinal nerves, they enter the periphery and end with motor endings in the skeletal muscles.
The white matter of the spinal cord is composed of myelin fibers running longitudinally. The bundles of nerve fibers that communicate between different parts of the nervous system are called the pathways of the spinal cord.
Brain
In the brain, gray and white matter are also distinguished, but the distribution of these two components is more complicated here than in the spinal cord. The main part of the gray matter of the brain is located on the surface of the cerebrum and cerebellum, forming their cortex. The other (smaller) part forms numerous nuclei of the brain stem.
brain stem. All nuclei of the gray matter of the brainstem are composed of multipolar nerve cells. They have endings of neurite cells of the spinal ganglia. Also in the brain stem there are a large number of nuclei designed to switch nerve impulses from the spinal cord and brain stem to the cortex and from the cortex to the spinal cord's own apparatus.
in the medulla oblongata there are a large number of nuclei of the own apparatus of cranial nerves, which are mainly located in the bottom of the IV ventricle. In addition to these nuclei, there are nuclei in the medulla oblongata that switch impulses entering it to other parts of the brain. These kernels include the lower olives.
In the central region of the medulla oblongata is located the reticular substance, in which there are numerous nerve fibers running in different directions and together forming a network. This network contains small groups of multipolar neurons with long few dendrites. Their axons spread in ascending (to the cerebral cortex and cerebellum) and descending directions.
The reticular substance is a complex reflex center associated with the spinal cord, cerebellum, cerebral cortex and hypothalamic region.
The main bundles of myelinated nerve fibers of the white matter of the medulla oblongata are represented by cortico-spinal bundles - pyramids of the medulla oblongata, lying in its ventral part.
Bridge of the brain consists of a large number of transversely running nerve fibers and nuclei lying between them. In the basal part of the bridge, the transverse fibers are separated by pyramidal pathways into two groups - posterior and anterior.
midbrain consists of the gray matter of the quadrigemina and the legs of the brain, which are formed by a mass of myelinated nerve fibers coming from the cerebral cortex. The tegmentum contains a central gray matter composed of large multipolar and smaller spindle-shaped cells and fibers.
diencephalon mainly represents the visual tubercle. Ventral to it is a hypothalamic (hypothalamic) region rich in small nuclei. The visual hillock contains many nuclei delimited from each other by layers of white matter, they are interconnected by associative fibers. In the ventral nuclei of the thalamic region, ascending sensory pathways end, from which nerve impulses are transmitted to the cortex. Nerve impulses to the visual hillock from the brain go along the extrapyramidal motor pathway.
In the caudal group of nuclei (in the pillow of the thalamus), the fibers of the optic pathway end.
hypothalamic region is a vegetative center of the brain that regulates the main metabolic processes: body temperature, blood pressure, water, fat metabolism, etc.
Cerebellum
The main function of the cerebellum is to ensure balance and coordination of movements. It has a connection with the brain stem through afferent and efferent pathways, which together form three pairs of cerebellar peduncles. On the surface of the cerebellum there are many convolutions and grooves.
Gray matter forms the cerebellar cortex, a smaller part of it lies deep in the white matter in the form of central nuclei. In the center of each gyrus there is a thin layer of white matter, covered with a layer of gray matter - the bark.
There are three layers in the cerebellar cortex: outer (molecular), middle (ganglionic) and inner (granular).
Efferent neurons of the cerebellar cortex pear-shaped cells(or Purkinje cells) make up the ganglion layer. Only their neurites, leaving the cerebellar cortex, form the initial link of its efferent inhibitory pathways.
All other nerve cells of the cerebellar cortex are intercalated associative neurons that transmit nerve impulses to pear-shaped cells. In the ganglionic layer, the cells are arranged strictly in one row, their cords, branching abundantly, penetrate the entire thickness of the molecular layer. All branches of the dendrites are located only in one plane perpendicular to the direction of the convolutions, therefore, with a transverse and longitudinal section of the convolutions, the dendrites of the pear-shaped cells look different.
The molecular layer consists of two main types of nerve cells: basket and stellate.
basket cells located in the lower third of the molecular layer. They have thin long dendrites, which branch mainly in a plane located transversely to the gyrus. The long neurites of the cells always run across the gyrus and parallel to the surface above the piriform cells.
stellate cells are above the basket. There are two forms of stellate cells: small stellate cells, which are equipped with thin short dendrites and weakly branched neurites (they form synapses on the dendrites of pear-shaped cells), and large stellate cells, which have long and highly branched dendrites and neurites (their branches connect with the dendrites of pear-shaped cells). cells, but some of them reach the bodies of pear-shaped cells and are part of the so-called baskets). Together, the described cells of the molecular layer represent a single system.
The granular layer is represented by special cellular forms in the form grains. These cells are small in size, have 3 - 4 short dendrites, ending in the same layer with terminal branches in the form of a bird's foot. Entering into a synaptic connection with the endings of excitatory afferent (mossy) fibers entering the cerebellum, the dendrites of the granule cells form characteristic structures called cerebellar glomeruli.
The processes of granule cells, reaching the molecular layer, form in it T-shaped divisions into two branches, oriented parallel to the surface of the cortex along the gyri of the cerebellum. These fibers, running in parallel, cross the branching of the dendrites of many pear-shaped cells and form synapses with them and the dendrites of basket cells and stellate cells. Thus, the neurites of the granule cells transmit the excitation they receive from mossy fibers over a considerable distance to many pear-shaped cells.
The next type of cells are spindle-shaped horizontal cells. They are located mainly between the granular and ganglionic layers, from their elongated bodies long, horizontally extending dendrites extend in both directions, ending in the ganglionic and granular layers. Afferent fibers entering the cerebellar cortex are represented by two types: mossy and so-called climbing fibers. Mossy fibers go as part of the olive-cerebellar and cerebellopontine pathways and have a stimulating effect on the pear-shaped cells. They end in the glomeruli of the granular layer of the cerebellum, where they come into contact with the dendrites of the granule cells.
climbing fibers enter the cerebellar cortex through the spinocerebellar and vestibulocerebellar pathways. They cross the granular layer, adjoin pear-shaped cells and spread along their dendrites, ending on their surface with synapses. These fibers transmit excitation to pear-shaped cells. When various pathological processes occur in pear-shaped cells, it leads to a disorder in the coordination of movement.
cerebral cortex
It is represented by a layer of gray matter about 3 mm thick. It is very well represented (developed) in the anterior central gyrus, where the thickness of the cortex reaches 5 mm. A large number of furrows and convolutions increases the area of the gray matter of the brain.
There are about 10-14 billion nerve cells in the cortex.
Different parts of the cortex differ from each other in the location and structure of the cells.
Cytoarchitectonics of the cerebral cortex. The neurons of the cortex are very diverse in form, they are multipolar cells. They are divided into pyramidal, stellate, fusiform, arachnid and horizontal neurons.
Pyramidal neurons make up the bulk of the cerebral cortex. Their bodies have the shape of a triangle, the apex of which faces the surface of the cortex. From the top and side surfaces of the body depart dendrites, ending in different layers of gray matter. Neurites originate from the base of the pyramidal cells, in some cells they are short, forming branches within a given area of the cortex, in others they are long, entering the white matter.
Pyramidal cells of different layers of the cortex are different. Small cells are intercalary neurons, the neurites of which connect separate parts of the cortex of one hemisphere (associative neurons) or two hemispheres (commissural neurons).
Large pyramids and their processes form pyramidal pathways that project impulses to the corresponding centers of the trunk and spinal cord.
In each layer of cells of the cerebral cortex there is a predominance of some types of cells. There are several layers:
1) molecular;
2) external granular;
3) pyramidal;
4) internal granular;
5) ganglionic;
6) a layer of polymorphic cells.
AT molecular layer of the cortex contains a small number of small spindle-shaped cells. Their processes run parallel to the surface of the brain as part of the tangential plexus of nerve fibers of the molecular layer. In this case, the bulk of the fibers of this plexus is represented by branching of the dendrites of the underlying layers.
Outer granular layer is a cluster of small neurons that have a different shape (mostly rounded) and stellate cells. The dendrites of these cells rise into the molecular layer, and the axons go into the white matter or, forming arcs, go to the tangential plexus of fibers of the molecular layer.
pyramid layer- the largest in thickness, very well developed in the precentral gyrus. The sizes of pyramidal cells are different (within 10 - 40 microns). From the top of the pyramidal cell, the main dendrite departs, which is located in the molecular layer. The dendrites coming from the lateral surfaces of the pyramid and its base are of insignificant length and form synapses with adjacent cells of this layer. In this case, you need to know that the axon of the pyramidal cell always departs from its base. The inner granular layer in some areas of the cortex is very strongly developed (for example, in the visual cortex), but in some areas of the cortex it may be absent (in the precentral gyrus). This layer is formed by small stellate cells, it also includes a large number of horizontal fibers.
The ganglionic layer of the cortex consists of large pyramidal cells, and the region of the precentral gyrus contains giant pyramids, described for the first time by the Kiev anatomist V. Ya. Bets in 1874 (Bets cells). Giant pyramids are characterized by the presence of large lumps of basophilic substance. The neurites of the cells of this layer form the main part of the cortico-spinal tracts of the spinal cord and terminate in synapses on the cells of its motor nuclei.
Layer of polymorphic cells formed by spindle-shaped neurons. The neurons of the inner zone are smaller and lie at a great distance from each other, while the neurons of the outer zone are larger. The neurites of the cells of the polymorphic layer go into the white matter as part of the efferent pathways of the brain. Dendrites reach the molecular layer of the cortex.
It must be borne in mind that in different parts of the cerebral cortex, its different layers are represented differently. So, in the motor centers of the cortex, for example, in the anterior central gyrus, layers 3, 5 and 6 are highly developed and layers 2 and 4 are underdeveloped. This is the so-called agranular type of cortex. Descending pathways of the central nervous system originate from these areas. In the sensitive cortical centers, where the afferent conductors coming from the organs of smell, hearing and vision end, the layers containing large and medium pyramids are poorly developed, while the granular layers (2nd and 4th) reach their maximum development. This type is called the granular type of the cortex.
Myeloarchitectonics of the cortex. In the cerebral hemispheres, the following types of fibers can be distinguished: associative fibers (connect individual parts of the cortex of one hemisphere), commissural (connect the cortex of different hemispheres) and projection fibers, both afferent and efferent (connect the cortex with the nuclei of the lower parts of the central nervous system).
The autonomic (or autonomic) nervous system, according to various properties, is divided into sympathetic and parasympathetic. In most cases, both of these species simultaneously take part in the innervation of organs and have an opposite effect on them. So, for example, if irritation of the sympathetic nerves delays intestinal motility, then irritation of the parasympathetic nerves excites it. The autonomic nervous system also consists of central sections, represented by the nuclei of the gray matter of the brain and spinal cord, and peripheral sections - nerve nodes and plexuses. The nuclei of the central division of the autonomic nervous system are located in the middle and medulla oblongata, as well as in the lateral horns of the thoracic, lumbar and sacral segments of the spinal cord. The nuclei of the craniobulbar and sacral divisions belong to the parasympathetic, and the nuclei of the thoracolumbar division belong to the sympathetic nervous system. The multipolar nerve cells of these nuclei are associative neurons of the reflex arcs of the autonomic nervous system. Their processes leave the central nervous system through the anterior roots or cranial nerves and end in synapses on the neurons of one of the peripheral ganglia. These are the preganglionic fibers of the autonomic nervous system. The preganglionic fibers of the sympathetic and parasympathetic autonomic nervous systems are cholinergic. The axons of the nerve cells of the peripheral ganglions emerge from the ganglia in the form of postganglionic fibers and form terminal apparatuses in the tissues of the working organs. Thus, morphologically, the autonomic nervous system differs from the somatic one in that the efferent link of its reflex arcs is always binomial. It consists of central neurons with their axons in the form of preganglionic fibers and peripheral neurons located in peripheral nodes. Only the axons of the latter - postganglionic fibers - reach the tissues of the organs and enter into a synaptic connection with them. Preganglionic fibers in most cases are covered with a myelin sheath, which explains the white color of the connecting branches that carry sympathetic preganglionic fibers from the anterior roots to the ganglia of the sympathetic border column. Postganglionic fibers are thinner and in most cases do not have a myelin sheath: these are fibers of gray connecting branches that run from the nodes of the sympathetic border trunk to the peripheral spinal nerves. The peripheral nodes of the autonomic nervous system lie both outside the organs (sympathetic prevertebral and paravertebral ganglia, parasympathetic nodes of the head), and in the wall of organs as part of the intramural nerve plexuses that occur in the digestive tract, heart, uterus, bladder, etc.
Sheaths of the brain and spinal cord
The brain and spinal cord are covered with three types of membranes: soft (directly adjacent to the tissues of the brain), arachnoid and hard (bordering on the bone tissue of the skull and spine). The pia mater covers the brain tissue, it is delimited from it only by the marginal glial membrane. In this shell there are a large number of blood vessels that feed the brain, and numerous nerve fibers, terminal apparatus and single nerve cells. The arachnoid is a very delicate, loose layer of fibrous connective tissue. Between it and the pia mater lies the subarachnoid space, which communicates with the ventricles of the brain and contains cerebrospinal fluid. The dura mater is formed by dense fibrous connective tissue, it consists of a large number of elastic fibers. In the cranial cavity, it is tightly fused with the periosteum. In the spinal canal, the dura mater is delimited from the vertebral periosteum by an epidural space filled with a layer of loose fibrous unformed connective tissue, which provides it with some mobility. The subdural space contains a small amount of fluid.
From the book The Secret Wisdom of the Human Body author Alexander Solomonovich Zalmanov From the book The Great Guide to Massage author Vladimir Ivanovich Vasichkin From the book Massage. Great Master's Lessons author Vladimir Ivanovich Vasichkin From the book Diseases of Nervous People, or Where Does the Wind Blow? author Svetlana Choyzhinimaeva From the book The Body as a Phenomenon. Talking to a Therapist author Yuri Iosifovich Chernyakov by Shin Soo From the book How to Stay Young and Live Long author Yuri Viktorovich Shcherbatykh From the book Bath and Sauna for Health and Beauty author Vera Andreevna SolovievaIn the spinal cord distinguish between gray and white matter. On a transverse section of the spinal cord, the gray matter looks like the letter H. There are anterior (ventral), lateral, or lateral (lower cervical, thoracic, two lumbar), and posterior (dorsal) horns of the gray matter of the spinal cord.
Gray matter represented by the bodies of neurons and their processes, nerve endings with a synaptic apparatus, macro- and microglia and blood vessels.
white matter surrounds the gray matter outside and is formed by bundles of pulpy nerve fibers that form pathways throughout the entire spinal cord. These paths are directed towards the brain or descend from it. This also includes fibers that go to the higher or lower segments of the spinal cord. In addition, white matter contains astrocytes, individual neurons, and hemocapillaries.
in white matter each half of the spinal cord (on a transverse section) there are three pairs of columns (cords): posterior (between the posterior median septum and the medial surface of the posterior horn), lateral (between the anterior and posterior horns) and anterior (between the medial surface of the anterior horn and the anterior median fissure ).
In the center of the spinal cord passes through a canal lined with ependymocytes, among which there are poorly differentiated forms capable, according to some authors, of migration and differentiation into neurons. In the lower segments of the spinal cord (lumbar and sacral), after puberty, proliferation of gliocytes and overgrowth of the canal, the formation of an intraspinal organ occurs. The latter contains gliocytes and secretory cells that produce a vasoactive neuropeptide. The organ undergoes involution after 36 years.
gray matter neurons spinal cord are multipolar. Among them, neurons with a few weakly branching dendrites, neurons with branching dendrites, as well as transitional forms are distinguished.
Depending on where the shoots go neurons, emit: internal neurons, the processes of which end in synapses within the spinal cord; bundle neurons, the neurite of which goes as part of bundles (conducting pathways) to other parts of the spinal cord or to the brain; radicular neurons, the axons of which leave the spinal cord as part of the anterior roots.
In cross section, neurons are grouped into nuclei, which contain neurons similar in structure and function. On a longitudinal section, these neurons are arranged in layers in the form of a column, which is clearly visible in the region of the posterior horn. The neurons of each column innervate strictly defined areas of the body. The regularities of the grouping of neurons and their functions can be judged by the Rexed plates (1-X). In the center of the posterior horn is its own nucleus of the posterior horn, at the base of the posterior horn is the thoracic nucleus (Clark), lateral and somewhat deeper are the basilar nuclei, in the intermediate zone is the medial intermediate nucleus. In the dorsal part of the posterior horn, small neurons of the gelatinous substance (Roland's) are successively located from the depth to the outside, then small neurons of the spongy zone and, finally, the border zone containing small neurons.
Axons of sensory neurons from the spinal ganglia enter the spinal cord through the posterior roots and further into the marginal zone, where they are divided into two branches: a short descending and a long ascending. Along the lateral branches from these branches of the axon, impulses are transmitted to the associative neurons of the gray matter. Pain, temperature and tactile sensitivity is projected onto the neurons of the gelatinous substance and the own nucleus of the posterior horn. The gelatinous substance contains interneurons that produce opioid peptides that affect pain sensations (the so-called "pain gates"). Impulses from the internal organs are transmitted to the neurons of the nuclei of the intermediate zone. Signals from muscles, tendons, joint capsules, etc. (proprioception) are directed to Clark's nucleus and other nuclei. The axons of the neurons of these nuclei form ascending pathways.
In the posterior horns of the spinal cord many diffusely located neurons whose axons terminate within the spinal cord on the same or opposite side of the gray matter. The axons of these neurons enter the white matter and immediately divide into descending and ascending branches. Spreading at the level of 4-5 spinal segments, these branches together form their own bundles of white matter, directly adjacent to the gray matter. At the same time, the posterior, lateral and anterior proper bundles are distinguished. All these bundles of white matter belong to the own apparatus of the spinal cord. From the axons that are part of their own bundles, collaterals depart, ending in synapses on motor neurons. Due to this, conditions are created for an avalanche-like increase in the number of neurons that transmit impulses along the reflex arcs of the spinal cord's own apparatus.
Spinal cord- medulla spinalis - lies in the spinal canal, occupying approximately 2/3 of its volume. In cattle and horses, its length is 1.8-2.3 m, weight 250-300 g, in pigs - 45-70 g. It looks like a cylindrical cord, somewhat flattened dorsoventrally. There is no clear boundary between the brain and spinal cord. It is believed that it runs along the anterior margin of the atlas. In the spinal cord, cervical, thoracic, lumbar, sacral and caudal parts are distinguished according to their location. In the embryonic period of development, the spinal cord fills the entire spinal canal, but due to the high growth rate of the skeleton, the difference in their length becomes larger. As a result, the brain in cattle ends at the level of the 4th, in the pig - in the region of the 6th lumbar vertebra, and in the horse - in the region of the 1st segment of the sacral bone. Along the entire spinal cord along its dorsal surface passes median dorsal groove. Connective tissue departs from it deep into dorsal septum. On the sides of the median sulcus are smaller dorsal lateral grooves. On the ventral surface there is a deep median ventral fissure, and on the sides of it - ventral lateral grooves. At the end, the spinal cord sharply narrows, forming cerebral cone, which goes into terminal thread. It is formed by connective tissue and ends at the level of the first tail vertebrae.
There are thickenings in the cervical and lumbar parts of the spinal cord. In connection with the development of the limbs, the number of neurons and nerve fibers in these areas increases. At the pig cervical thickening formed by 5–8 neurosegments. Its maximum width at the level of the 6th cervical vertebra is 10 mm. Lumbar thickening falls on the 5th-7th lumbar neurosegments. In each segment, a pair of spinal nerves departs from the spinal cord with two roots - on the right and on the left. The dorsal root arises from the dorsal lateral groove, the ventral root from the ventral lateral groove. The spinal nerves leave the spinal canal through the intervertebral foramen. The area of the spinal cord between two adjacent spinal nerves is called neurosegment.
Neurosegments are of different lengths and often do not correspond in size to the length of the bone segment. As a result, the spinal nerves depart at different angles. Many of them travel some distance inside the spinal canal before leaving the intervertebral foramen of their segment. In the caudal direction, this distance increases and from the nerves running inside the spinal canal, behind the cerebral cone, a kind of brush is formed, which is called the "ponytail".
Histological structure. On a transverse section of the spinal cord with the naked eye, its division into white and gray matter is visible.
Gray matter is in the middle and looks like the letter H or a flying butterfly. A small hole is visible in its center - a cross section central spinal canal. The area of gray matter around the central canal is called gray commissure. Directed upwards from her dorsal pillars(on a cross section - horns), down - ventral columns (horns) gray matter. In the thoracic and lumbar parts of the spinal cord, there are thickenings on the sides of the ventral columns - lateral pillars, or horns gray matter. The composition of the gray matter includes multipolar neurons and their processes that are not covered with a myelin sheath, as well as neuroglia.
Fig.142. Spinal cord (according to I.V. Almazov, L.S. Sutulov, 1978)
1 - dorsal median septum; 2 - ventral median fissure; 3 - ventral root; 4 - ventral gray commissure; 5 - dorsal gray commissure; 6 - spongy layer; 7 - gelatinous substance; 8 - dorsal horn; 9 - mesh reticular formation; 10 - lateral horn; 11 - ventral horn; 12 - own nucleus of the posterior horn; 13 - dorsal nucleus; 14 - cores of the intermediate zone; 15 - lateral core; 16 - nuclei of the ventral horn; 17 - shell of the brain.
Neurons in different parts of the brain differ in structure and function. In this regard, various zones, layers and cores are distinguished in it. The bulk of the neurons of the dorsal horns are associative, intercalary neurons that transmit the nerve impulses that come to them either to motor neurons, or to the lower and upper parts of the spinal cord, and then to the brain. The axons of sensory neurons of the spinal ganglia approach the dorsal columns. The latter enter the spinal cord in the region of the dorsal lateral grooves in the form of dorsal roots. The degree of development of the dorsal lateral columns (horns) is directly dependent on the degree of sensitivity.
The ventral horns contain motor neurons. These are the largest multipolar nerve cells in the spinal cord. Their axons form the ventral roots of the spinal nerves, extending from the spinal cord in the region of the ventral lateral sulcus. The development of the ventral horns depends on the development of the locomotor apparatus. The lateral horns contain neurons belonging to the sympathetic nervous system. Their axons leave the spinal cord as part of the ventral roots and form the white connecting branches of the borderline sympathetic trunk.
white matter forms the periphery of the spinal cord. In the area of thickening of the brain, it prevails over the gray matter. Consists of myelinated nerve fibers and neuroglia. The myelin sheath of the fibers gives them a whitish-yellowish color. The dorsal septum, ventral fissure and pillars (horns) of the gray matter divide the white matter into cords: dorsal, ventral and lateral. Dorsal cords do not connect with each other, since the dorsal septum reaches the gray commissure. Lateral cords separated by a mass of gray matter. Ventral cords communicate with each other in the area white spike- an area of white matter lying between the ventral fissure and the gray commissure.
Complexes of nerve fibers passing in the cords form pathways. More deeply lying complexes of fibers form conducting paths connecting different segments of the spinal cord. Together they amount to own apparatus spinal cord. More superficially located complexes of nerve fibers form afferent (sensory, or ascending) and efferent (motor, or descending) projection pathways connecting the spinal cord to the brain. Sensory pathways from the spinal cord to the brain run in the dorsal cords and in the superficial layers of the lateral cords. The motor pathways from the brain to the spinal cord run in the ventral cords and in the middle sections of the lateral cords.
F KSMU 4/3-05/03
Karaganda State Medical University
Department of Histology
Subject:"Histology of the spinal cord, ganglion, nerve."
Discipline: histology-2
Module: nervous system
Speciality: 5B130100 - "General Medicine" (bachelor's degree)
Well: 3
Time (duration):4 hours
Compiled by: Professor Kurkin A.V.
Karaganda 2014
Discussed and approved
at a meeting of the Department of Histology
Protocol No. __ "___" _________ 2014
Head departmentEsimova R.Zh.
Subject: Histology of the spinal cord, ganglion, nerve
Target: To study the histophysiology of the peripheral nerve, spinal ganglion and spinal cord.
Learning objectives
1. Determine the structure of the peripheral nerve in preparations.
2. Identify the structures of the spinal ganglion in the preparation
3. Determine the gray and white matter of the spinal cord in preparations.
Main intopic polls:
1. The function of the nervous system.
2. Structural organization of the nervous system.
3. Development of the nervous system in phylo- and ontogenesis.
4. The structure of the spinal node.
5. The structure of the peripheral nerve.
6. Spinal cord.
6.1. Functions and development of the spinal cord.
6.2. The structure of the spinal cord.
Methods of learning and teaching:
1. Work in small groups;
2. Microscopy and sketching of histological preparations;
3. Situational tasks;
Literature
Histology, embryology, cytology: Textbook / ed.: Yu. I. Afanasiev; Kuznetsov S.L.; Yurina N.A., / -M.: Medicine, 2004.-768 p.
Histology, embryology, cytology, textbook for universities. - / Afanasiev Yu.I., Yurina N.A. / M .: GEOTAR-Media, 2012 - 800 p.
Histology, cytology and embryology.: Textbook for medical. universities. / Kuznetsov S.L., Mushkambarov N.N. / M .: Medical Information Agency, 2007. - 600 p. /
Histology, cytology and embryology.: Textbook for medical. universities. / Kuznetsov S.L., Mushkambarov N.N. / M.: Medical Information Agency, 2013. - 640 p.
Histology, embryology, cytology: Textbook / ed.: E. G. Ulumbekov, Yu. A. Chelyshev. - M. : GEOTAR-Media, 2009. - 408 p.
Histology. Embryology. Cytology: Textbook for medical students. universities / Danilov, R.K. - M.: Med. inform. agency, 2006. - 456 p.
Histology, cytology and embryology: atlas for students. medical universities. /R.B. Abildinov, Zh.O. Ayapova, R.I. Yu. - Almaty, 2006. - 416 p.
Atlas of microphotographs on histology, cytology and embryology for practical exercises / Yui R.I., Abildinov R.B. /.-Almaty, - 2010.-232 p.
Nervous system Integrated textbook / ed. R. S. Dosmagambetova / M.: Litterra, 2014.-264p.
Additional literature:
Age histology: textbook. Allowance / ed. Pulikov A.S. Publishing house "Phoenix", 2006. - 173 p.
Visual histology (general and private): Proc. allowance for medical students. universities / Garstukova, L.G., Kuznetsov S.L., Derevianko V.G. - M.: Med. inform. agency, 2008. - 200 p.
Histology: Textbook: Comprehensive tests: answers and explanations / ed. prof. S.L. Kuznetsova, prof. Yu.A. Chelysheva. - M.: GEOTAR-Media, 2007. - 288 p.
Histology: Atlas for practical exercises / N. V. Boichuk [and others]. - M. : GEOTAR-Media, 2008. - 160 p.
Human histology in multimedia. Danilov R.K., Klishov A.A., Borovaya T.G. Textbook for medical students. ELBI-SPb, 2004. - 362 p.
Atlas of histology, cytology and embryology. Samusev R.P., Pupysheva G.I., Smirnov A.V. M.. ONIX, XXI century, World and Education, 2004, 400s.
Guide to histology: in 2 volumes: textbook. allowance / ed. R. K. Danilov. - 2nd ed., corrected. and additional - St. Petersburg. : SpecLit T. 1. - 2011. - 831 p.
Atlas of histology: trans. with him. / ed. W. Velsha. - M.: GEOTAR-Media, 2011. - 264 p.
Guide to histology: in 2 volumes: textbook. allowance / ed. R. K. Danilov. - 2nd ed., corrected. and additional - St. Petersburg. : Special Lit. T. 2. - 2011. - 511 p.
Histology: Schemes, tables and situational tasks for private human histology: textbook. allowance / Vinogradov S.Yu. [and etc.]. - M. : GEOTAR-Media, 2012. - 184 p.
Histology of the regulatory systems of the body (development of features in children): textbook / D. Kh. Rybalkina; KSMU. - Karaganda, 2013. - 104 p.
The control
Test questions.
How is the connection between the organs of the central and peripheral parts of the nervous system?
How is the peripheral nerve built?
What types of nerve fibers are included in the peripheral nerve?
How is the spinal ganglion built?
What is the role and place in the reflex arc of neurocytes of the spinal ganglion?
Where are the autonomic ganglia located and how are they arranged?
What is the structure of the spinal cord?
What place do gray matter neurons of the spinal cord occupy in simple and complex reflex arcs?
What neurocytes are part of the somatic reflex arc? What are their locations?
What neurocytes are part of the autonomic reflex arc? What are their locations?
Tests
1. In the anterior horns of the spinal cord, there are:
spongy layer
gelatinous substance
Medial and lateral group of motor cells
thoracic nucleus
Medial and lateral intermediate nucleus
2. With the help of own pathways of the spinal cord are connected:
Spinal cord and cerebral cortex
Spinal cord and brainstem nuclei
4-5 adjacent segments of the spinal cord
spinal cord and medulla oblongata
spinal cord and cerebellum
3. The nuclei of the gray matter of the spinal cord are formed by:
protoplasmic astrocytes
Fibrous astrocytes
microglia
Fibroblasts of varying degrees of differentiation
Nerve cells similar in size, structure and function
4. Neurites of radicular cells of the spinal cord:
Leave the spinal cord as part of the anterior roots
Pass through the white matter, forming descending pathways
Leave the spinal cord as part of its posterior roots
Terminate in synapses within the gray matter of the spinal cord
Pass through the white matter, forming ascending pathways
5. Associative sympathetic neurocytes of the spinal cord form nuclei in:
Anterior horns
Anterior cords
back horns
Lateral horns
Lateral cords
6. Nerve fibers of the spinal nerve form ...
ascending tracts of the spinal cord
motor roots of the spinal cord
mixed nerve
sensory roots of the spinal cord
ascending and descending tracts of the spinal cord
7. In the spinal ganglion, the capsule is represented by ...
false unipolar neurocytes
oligodendrogliocytes
connective tissue
myelinated nerve fibers
multipolar neurocytes
8. Choose the correct answers: The posterior roots of the spinal cord are formed by:
Axons of neurons of motor nuclei
Dendrites of neurocytes of the spinal ganglia
Axons of neurocytes of the lateral horns
Axons of neurons of the spinal nodes
9. Choose the correct answers: The following types of gliocytes are found in the white matter of the spinal cord:
microgliocytes
Fibrous astrocytes
Oligodendrogliocytes
Plasma astrocytes
10. Are the statements true and the relationship between them: The afferent link of the somatic reflex arc includes a spinal ganglion neurocyte, because its dendrite forms a sensitive nerve ending.
situational tasks.
As a result of the injury, the integrity of the anterior root of the spinal cord was disrupted. Determine the processes of which neurons are damaged in this case?
Pathological anatomical examination of the human spinal cord revealed degeneration and a decrease in the number of cells that make up the nuclei of the anterior horns in the cervical and thoracic regions. The function of what tissue was first of all impaired as a result of nuclear damage?
Examination of the patient revealed a lesion of the spinal cord, which is combined with a dysfunction of the motor apparatus. Destruction of what neurons can explain this phenomenon?
A patient with a mechanical injury to the spine has dysfunction of the associative neurons of the sacral part of the parasympathetic nervous system. What structures of the spinal cord are damaged?
In the posterior funiculus of the white matter of the spinal cord during surgical intervention according to clinical indications, the neurites of the bundle cells located near the gray commissure were cut. The function of what pathways is disturbed in this case?
A patient with poliomyelitis with spinal cord injury has impaired skeletal muscle function. Destruction of which neurons can explain this?
A patient with a mechanical injury of the spine has damage to the cells of the thoracic nucleus of the spinal cord. The function of what pathways is disturbed in this case?
A patient has damaged neurocytes of the own nucleus of the dorsal horn of the spinal cord. Which conduction pathways function is impaired?
In an experiment on rats, the cells of the lateral nucleus of the intermediate zone of the gray matter of the sacral spinal cord were damaged. The function of what structures of the nervous system will be impaired?
A well-developed Golgi complex is visible on a micrograph of a cell of the spinal ganglion. What functions does it perform?
When studying the process of formation of nerve fibers in the embryonic period, it was revealed that several structural elements of the nervous tissue take part in this process. Which of the following structural components are involved in the formation of myelin fibers?
Examination of a patient with impaired motor function of skeletal muscles revealed damage to nodal interceptions of myelinated nerve fibers of peripheral nerves. Where is the damage located in the myelin fiber?
After suffering a spinal cord injury, the patient developed paresis of the muscles of the extremities due to damage to myelinated nerve fibers. Morphological examination revealed disturbances at the site of myelin incisions. What are myelin notches?
In some systemic demyelinating diseases of the nervous system, a slow destruction of the myelin sheath of nerve fibers was observed. What components of the nerve fiber are primarily damaged in these diseases?
Anomalies in the development of myelin nerve fibers were found in a newborn child, which is associated with impaired myelin formation due to damage to mesaxons. Which of the following structures could not form in this situation?
The preparation shows a section of a damaged human nerve fiber. The axial cylinder of the peripheral nerve process is fragmented. On what day after cutting the nerve fiber is this phenomenon observed?
Lesson equipment.
Objects of study:
1. Micropreparations:
1. Spinal cord (spinal, sensory) node. Stained with hematoxylin and eosin.
2. Sympathetic knot. solar plexus node. Coloring - silver impregnation.
3. Spinal cord - transverse section of the thoracic segment. Coloring - silver impregnation.
4. Peripheral nerve. Cross section of the sciatic nerve. Stained with hematoxylin and eosin.
5. Parasympathetic nerve ganglia in the musculo-intestinal nerve plexus. Coloring - silver impregnation.
2. Electron micrographs:
1. Nerve and glial cell of an autonomous node. Magnification 8000 times.
2. Non-fleshy nerve. Cross section. Magnification 17000 times.
3. Mixed nerve. Cross section. Magnification 40,000 times.
4. Motor plaque. Magnification 33,000 times.
3. Tables and diagrams:
1. Spinal node.
2. Peripheral nerve in cross section.
3. Scheme of a simple reflex arc.
4. The structure of the spinal cord.
Map of tasks and the basics of action.
Exercise 1. To study the morphology of the spinal cord.
In a transverse, oval-shaped section of the spinal cord, impregnated with silver, visually examine the gray matter located in the middle, in the form of the letter H, and the white matter surrounding it from the outside. At low magnification of the microscope, place the slice with the anterior median fissure down. In the gray matter, find the narrow posterior horns and the posterior roots entering them, and then the wide anterior horns and the anterior roots emerging from them. In the white matter of the brain, identify paired posterior, lateral, and anterior columns. At high magnification in the gray matter, study local clusters of multipolar neurons - the nuclei of the spinal cord. In the initial part of the posterior horns, pay attention to diffusely located small neurocytes that form 3 zones (terminal, gelatinous and spongy). These are Roland's cores; below and laterally - compact proper nuclei of the posterior horns; and even lower and medially - the thoracic nuclei. Around the central canal, the own nuclei of the spinal cord are localized. In the cervical and lumbar sections of the spinal cord, lateral horns with sympathetic nuclei are determined at this level. The motor nuclei are concentrated in the anterior horns. In the columns of white matter, consider cut across the myelinated nerve fibers that make up the pathways of the spinal cord. Draw a section and label: 1 - gray matter, 2 - posterior root and horn, 3 - Roland's nucleus, 4 - nucleus proper of the posterior horn, 5 - thoracic nucleus, 6 - central canal, 7 - own nuclei of the spinal cord, 8 - lateral horn , 9 - sympathetic nucleus, 10 - anterior horn and root, 11 motor nuclei, 12 - anterior median fissure, 13 - white matter, 14 - posterior columns, 15 - lateral columns, 16 - anterior columns.
Task 2. To study the histological structure of the spinal ganglion.
In a longitudinal section of the spinal ganglion, stained with hematoxylin and eosin, at low magnification of the microscope, determine the connective tissue capsule and located under it, groups of rounded (with and without nuclei) pseudo-unipolar neurons, the processes of which in the middle part of the ganglion form a longitudinal bundle of nerve fibers, continuing into, emerging from the node - the posterior root of the spinal cord. Pay attention to the ganglion that joins the capsule from below - the anterior root of the spinal cord, which, together with the median bundle of nerve fibers behind the node, unites into a mixed nerve. At a high magnification of the microscope, examine pseudo-unipolar neurons and the surrounding oligodendrogliocytes - satellite cells. Draw a section and label: 1 - spinal ganglion, 2 - capsule, 3 - pseudounipolar neurocytes, 4 - satellite cells, 5 - bundle of nerve fibers, 6 - posterior root, 7 - anterior root, 8 - mixed nerve.
Task 3. To study the structure of the peripheral nerve.
In the transverse section of the nerve impregnated with osmic acid, at low magnification of the microscope, determine the outer connective tissue sheath - epineurium and interfascicular septa - perineurium. At a high magnification of the microscope, consider the constituent nerve bundles - myelinated nerve fibers, in the transverse sections of which black rings of the myelin layer are determined. Loose connective tissue, endoneurium, is recorded around the fibers. Draw a section and label: 1 - nerve trunk, 2 - epineurium, 3 - nerve bundles, 4 - perineurium, 5 - nerve fibers, 6 - endoneurium.
The spinal cord (SM) consists of 2 symmetrical halves, separated in front by a deep fissure and behind by a commissure. The transverse section clearly shows the gray and white matter. The gray matter of the SM on the cut has the shape of a butterfly or the letter "H" and has horns - anterior, posterior and lateral horns. The gray matter of the SM consists of bodies of neurocytes, nerve fibers and neuroglia.
The abundance of neurocytes determines the gray color of the gray matter of the SM. Morphologically, SM neurocytes are predominantly multipolar. Neurocytes in the gray matter are surrounded by nerve fibers tangled like felt - neuropil. The axons in the neuropil are weakly myelinated, while the dendrites are not at all myelinated. Similar in size, fine structure, and functions, SC neurocytes are arranged in groups and form nuclei.
Among SM neurocytes, the following types are distinguished:
1. Radicular neurocytes - located in the nuclei of the anterior horns, they are motor in function; axons of radicular neurocytes as part of the anterior roots leave the spinal cord and conduct motor impulses to the skeletal muscles.
2. Internal cells - the processes of these cells do not leave the limits of the gray matter of the SM, end within the given segment or the neighboring segment, i.e. are associative in function.
3. Beam cells - the processes of these cells form the nerve bundles of the white matter and are sent to neighboring segments or overlying sections of the NS, i.e. are also associative in function.
The posterior horns of the SM are shorter, narrower and contain the following types of neurocytes:
a) beam neurocytes - located diffusely, receive sensitive impulses from the neurocytes of the spinal ganglia and transmit along the ascending paths of the white matter to the overlying sections of the NS (to the cerebellum, to the cerebral cortex);
b) internal neurocytes - transmit sensitive impulses from the spinal ganglia to the motor neurocytes of the anterior horns and to neighboring segments.
There are 3 zones in the posterior horns of the CM:
1. Spongy substance - consists of small bundled neurocytes and gliocytes.
2. Gelatinous substance - contains a large number of gliocytes, has practically no neurocytes.
3. Proprietary SM nucleus - consists of bundled neurocytes that transmit impulses to the cerebellum and thalamus.
4. Clark's nucleus (Thoracic nucleus) - consists of bundled neurocytes, the axons of which, as part of the lateral cords, are sent to the cerebellum.
In the lateral horns (intermediate zone) there are 2 medial intermediate nuclei and a lateral nucleus. The axons of the bundle associative neurocytes of the medial intermediate nuclei transmit impulses to the cerebellum. The lateral nucleus of the lateral horns in the thoracic and lumbar SM is the central nucleus of the sympathetic division of the autonomic NS. The axons of the neurocytes of these nuclei go as part of the anterior roots of the spinal cord as preganglionic fibers and terminate on the neurocytes of the sympathetic trunk (prevertebral and paravertebral sympathetic ganglia). The lateral nucleus in the sacral SM is the central nucleus of the parasympathetic division of the autonomic NS.
The anterior horns of the SM contain a large number of motor neurons (motor neurons) that form 2 groups of nuclei:
1. Medial group of nuclei - innervates the muscles of the body.
2. The lateral group of nuclei is well expressed in the region of the cervical and lumbar thickening - it innervates the muscles of the extremities.
According to their function, among the motoneurons of the anterior horns of the SM are distinguished:
1. - motor neurons are large - have a diameter of up to 140 microns, transmit impulses to extrafusal muscle fibers and provide rapid muscle contraction.
2. -small motor neurons - maintain the tone of skeletal muscles.
3. -motoneurons - transmit impulses to intrafusal muscle fibers (as part of the neuromuscular spindle).
Motoneurons are an integrative unit of the SM; they are influenced by both excitatory and inhibitory impulses. Up to 50% of the body surface and motor neuron dendrites are covered with synapses. The average number of synapses per 1 human SC motor neuron is 25-35 thousand. At the same time, 1 motor neuron can transmit impulses from thousands of synapses coming from neurons of the spinal and supraspinal levels.
Reverse inhibition of motor neurons is also possible due to the fact that the axon branch of the motor neuron transmits an impulse to inhibitory Renshaw cells, and the axons of Renshaw cells terminate on the body of the motor neuron with inhibitory synapses.
Axons of motor neurons leave the spinal cord as part of the anterior roots, reach the skeletal muscles, and end on each muscle fiber with a motor plaque.
The white matter of the spinal cord consists of longitudinally oriented predominantly myelinated nerve fibers that form the posterior (ascending), anterior (descending), and lateral (both ascending and descending) cords, as well as glial elements.
