Name
Spinal ganglion (spinal ganglion, spinal ganglion) - in vertebrates: common name for nerve nodes (ganglia) of spinal nerves. Spinal ganglia, together with ganglia cranial nerves, refer to sensitive nerve nodes. Another group of nerve ganglia in the body are the autonomic ganglia.
It has a spindle shape. The outside is surrounded by a capsule, which consists of dense fibrous connective tissue.
The spinal ganglia contain the bodies of sensory (afferent) pseudounipolar neurons, which are located in groups at the periphery. The central part is occupied by the processes of these neurons (meat nerve fibers) and thin layers of endoneurium located between them, bearing vessels.
The nerve cells of the spinal ganglia are surrounded by a layer of glial cells called mantle gliocytes .
From that day, during the entire further journey of the Rostovs, at all rests and overnight stays, Natasha did not leave the wounded Bolkonsky, and the doctor had to admit that he did not expect from the girl either such firmness or such skill in caring for the wounded.
No matter how terrible the thought seemed to the countess that Prince Andrei could (very likely, according to the doctor) die during the journey in the arms of her daughter, she could not resist Natasha. Although, as a result of the now established rapprochement between the wounded Prince Andrei and Natasha, it occurred to him that in the event of recovery, the previous relationship of the bride and groom would be resumed, no one, least of all Natasha and Prince Andrei, spoke about this: the unresolved, hanging question of life or death is not only over Bolkonsky, but over Russia, overshadowed all other assumptions.
Pierre woke up late on September 3rd. His head ached, the dress in which he slept without undressing weighed down his body, and in his soul there was a vague consciousness of something shameful that had been committed the day before; This was a shameful conversation yesterday with Captain Rambal.
Department of Histology, Cytology and Embryology of SSMU Lecture topic: “Nervous system. Spinal ganglia. Spinal cord" Purpose of the lecture. Study the general plan of the structure of the nervous system, features of embryonic development, tissue composition, functional significance of various departments nervous system, give the concept of nerve centers of nuclear and screen type. Content. Tissue composition and development of nervous system organs. Somatic and autonomic parts of the nervous system. Organs of the central nervous system, their functional significance. Structure and localization of the spinal ganglia, cellular composition. Development, localization and structure spinal cord, structure of gray and white matter, gray matter nuclei, types of neurons in them, functional purpose. Structure and functions of the nervous system. The nervous system has integrating, coordinating, adaptive, regulating and other functions that ensure the interaction of a living organism with external environment and production adequate reaction to changing conditions. Anatomically, the nervous system is divided into central (brain and spinal cord) and peripheral (nerve ganglia, nerve trunks and endings). According to the functions performed in the nervous system, they are divided into: 1. the autonomic department, which provides communication between the central nervous system and the vessels, internal organs and glands, 2. the somatic department, which innervates all other parts of the body (for example, skeletal muscle tissue). The source of development of the nervous system is the neuroectoderm. At the 3rd week of embryogenesis, in the central part of the neroectodera, differentiation of cells occurs, from which the neural tube is formed by neurulation and the neural crest, which is divided into 2 ganglion plates. The brain and sensory organs are formed from the cranial part of the neural tube. The spinal cord, spinal and autonomic ganglia, as well as the chromaffin tissue of the body are formed from the trunk region and the ganglion plate. Connective tissue layers and membranes develop from mesenchyme. Sources of development of the nervous system Sources of development of the spinal cord Structure of the spinal ganglion 1. Dorsal root; 2. pseudounipolar neurons; 2a. mantle gliocytes; 3. anterior root; 4. nerve fibers; 5. layers of connective tissue Spinal ganglion Axons of pseudounipolar neurons contact the cell bodies of neurons in the medulla oblongata or dorsal horns of the spinal cord. Dendrites go as part of sensory nerves to the periphery and end with receptors. Pseudounipolar neurons of the spinal ganglion 1. The dendrite goes as part of the sensitive part of the mixed spinal nerves to the periphery and ends with receptors. 2. The axon passes as part of the dorsal roots into the medulla oblongata. 3. Perikaryon. 4. Nucleus with nucleolus. 5. Nerve fibers. Simple reflex arc Transverse section of the spinal cord Structure of the spinal cord. The gray matter of the spinal cord is formed by clusters of neurons called nuclei, neuroglial cells, unmyelinated and thin myelinated nerve fibers. The projections of gray matter are called horns or columns, among them there are: 1. anterior (ventral), 2. lateral (lateral), 3. posterior (dorsal) large cells r e f e r d o r d i s l o r e m o r e sh o k z i g a i - Anterior and lateral horns INTERMEDIATE ZONE AND LATERAL HORNS Here the neurons are grouped into two or one nucleus (depending on the level of the spinal cord). Medial intermediate nucleus (located in the intermediate zone). As in the case of the thoracic core. the axons of the neurons enter the lateral funiculus on the same side and ascend to the cerebellum. Lateral intermediate nucleus (located in the lateral horns and is an element of the sympathetic nervous system; axons of neurons leave the spinal cord through the anterior roots, separate from them in the form of white connecting branches and go to the sympathetic ganglia. B. ANTERIOR HORNS Several somatomotor nuclei; contain the largest cells of the spinal cord - motor neurons. Axons of motor neurons also leave the spinal cord through the anterior roots and then, as part of the mixed nerves, go to the skeletal muscles. POSSIBLE HORNS The posterior horns contain intercalary (associative) neurons that receive signals from the sensory neurons of the spinal ganglia. form the following structures: 1. Spongy layer and gelatinous substance: located in the posterior part and on the periphery of the posterior horns; they contain small neurons in the glial skeleton. The axons of these neurons go to the motor neurons of the anterior horns of the same segment of the spinal cord - the same side or the opposite (in. In the latter case, the cells are called commissural, because their axons form a commissure, or commissure, lying in front of the spinal canal). Diffuse interneurons. 2. Own kernel posterior horn(located in the center of the horn) The axons of the neurons move to the opposite side into the lateral funiculus and go to the cerebellum or to the thalamus optica. 3. Thoracic nucleus (at the base of the horn) Neuron axons enter the lateral funiculus on the same side and ascend to the cerebellum. White matter of the spinal cord White matter of the spinal cord White matter consists of nerve fibers and neuroglial cells. Gray matter horns separate white matter into three cords: 1. the posterior cords are located between the posterior septum and the posterior roots, 2. the lateral cords lie between the anterior and posterior roots, 3. the anterior cords are delimited by the anterior fissure and the anterior roots. Anterior to the gray commissure there is a section of white matter connecting the anterior cords - the white commissure. The pathways are formed by a chain of neurons connected in series by their processes; ensure the conduction of excitation from neuron to neuron (from nucleus to nucleus). Anterior horn of the spinal cord 1. Multipolar motor neuron of gray matter. 2. White matter. 3. Myelinated nerve fibers. 4. Connective tissue layers Based on the nature of the relationship, neurons are divided into: 1 – internal cells, the processes of which end at synapses within the gray matter of the spinal cord; 2 – tuft cells, their axons pass through the white matter in separate bundles and connect neurons of various segments of the spinal cord, as well as with the brain, forming pathways; 3 – root neurons, the axons of which extend beyond the boundaries of the spinal cord and form the anterior roots of the spinal nerves (in the skin, on the muscles). Simple reflex arc In the anterior horns there are motor neurons, in their interconnection they are radicular, forming 2 groups of motor nuclei: medial (muscles of the trunk) and lateral (muscles of the lower and upper extremities). In the lateral horns there are associative neurons, by interconnection they are fascicular, forming 2 intermediate nuclei: medial and lateral. Axons of lateral neurons leave the spinal cord as part of the anterior roots and go to the peripheral sympathetic ganglia. In the dorsal horns, associative neurons (internal and fasciculate) form 4 nuclei: spongiosa, gelatinous, nucleus of the dorsal horn proper and Clarke’s thoracic nucleus. Thank you for your attention!
Private histology.
Private histology– the science of the microscopic structure and origin of organs. Each organ consists of 4 tissues.
Organs of the nervous system.
Functionally
1. Somatic nervous system– participates in the innervation of the human body and higher nervous activity.
a. Central department :
i. Spinal cord - nuclei of the posterior and anterior horns
ii. Brain - cerebellar cortex and cerebral hemispheres
i. Spinal ganglia
ii. Cranial ganglia
iii. Nerve trunks
2. Autonomic nervous system– provides work internal organs, innervates smooth myocytes and represents secretory nerves.
1) Sympathetic:
a. Central department:
i. Spinal cord - nuclei of the lateral horns of the thoracolumbar region
ii. Brain - hypothalamus
b. Peripheral department:
i. Sympathetic ganglia
ii. Nerve trunks
2) Parasympathetic:
a. Central department:
i. Spinal cord - nuclei of the lateral horns of the sacral region
ii. Brain - brainstem nuclei, hypothalamus
b. Peripheral department:
i. Parasympathetic ganglia
ii. Nerve trunks
iii. Spinal and cranial ganglia
Anatomically The organs of the nervous system are divided into:
1. Peripheral nervous system.
2. Central nervous system.
Embryonic sources of development:
1. Neuroectoderm(gives rise to organ parenchyma).
2. Mesenchyme(gives rise to the stroma of organs, a set of auxiliary structures that ensure the functioning of the parenchyma).
The organs of the nervous system function in relative isolation from environment, separating from her biological barriers. Types of biological barriers:
1. Hematoneural (separates blood from neurons).
2. Liquoroneural (separates cerebrospinal fluid from neurons).
3. Hematocerebrospinal fluid (separates the cerebrospinal fluid from the blood).
Functions of the nervous system:
1. Regulation of the functions of individual internal organs.
2. Integration of internal organs into organ systems.
3. Ensuring the relationship of the body with the external environment.
4. Ensuring higher nervous activity.
All functions are based on the principle reflex. The material basis is reflex arc, consisting of 3 links: afferent, associative And efferent. They are distributed among individual organs of the nervous system.
Organs of the peripheral nervous system:
1. Nerve trunks (nerves).
2. Nerve nodes (ganglia).
3. Nerve endings.
Nerve trunks - these are bundles of nerve fibers united by a system of connective tissue membranes. The nerve trunks are mixed, i.e. each contains myelin and amyelin fibers, resulting in servicing of the somatic and autonomic nervous systems.
Structure of the nerve trunk:
1. Parenchyma: unmyelinated and myelinated nerve fibers + microganglia.
2. Stroma: connective tissue membranes:
1) Perineurium(perineural sheaths: RVNST + blood vessels + ependymogliocytes + cerebrospinal fluid).
2) Epineurium(PVNST + blood vessels).
3) Perineurium(splitting off from the epineurium into the trunk).
4) Endoneurium(RVNST + blood vessels).
In the perineurium there is a slit-like space - slit-like perineural vagina, which is filled cerebrospinal fluid(circulating biological fluid). Structural components of the walls of the perineural vagina:
1. Low prismatic ependymogliocytes.
2. Basement membrane.
3. Subependymal plate.
4. Blood vessels.
There may be no cerebrospinal fluid in the perineural sheath. Anesthetics and antibiotics are sometimes injected into them (since the disease spreads through them).
Functions of nerve trunks:
1. Conducting (conducting a nerve impulse).
2. Trophic (nutritional).
4. They are the initial link in the secretion and circulation of cerebrospinal fluid.
Regeneration of nerve trunks:
1. Physiological regeneration(very active restoration of membranes due to fibroblasts).
2. Reparative regeneration(that section of the nerve trunk is restored, the nerve fibers of which have not lost connection with the perikaryon - they are capable of growing by 1 mm/day; peripheral segments of nerve fibers are not restored).
Nerve nodes (ganglia) – groups or cooperation of neurons located outside the brain. The nerve nodes are “dressed” in capsules.
Types of ganglia:
1. Spinal.
2. Cranial.
3. Vegetative.
Spinal ganglia – thickenings on primary departments dorsal roots of the spinal cord; this is a collection of afferent (sensitive) neurons (they are the first neurons in the chain reflex arc).
Structure of the spinal ganglion:
1. Stroma:
1) outer connective tissue capsule, consisting of 2 sheets:
a. outer layer (dense connective tissue - continuation of the epineurium spinal nerve)
b. internal layer (multi-tissue: RVNST, gliocytes; analogue of the perineurium of the spinal nerve; there are splits that extend to the intraorgan septa, filled with cerebrospinal fluid).
2) intraorgan septa extending from the capsule into the node
b. blood and lymphatic vessels
c. nerve fibers
3) own connective tissue capsules of pseudounipolar neurons
a. fibrous connective tissue
b. single-layer squamous ependymoglial epithelium
c. perineuronal space with cerebrospinal fluid
2. Parenchyma:
1) central part (myelinated nerve fibers - processes of pseudounipolar neurons)
2) peripheral part (pseudounipolar neurons + mantle gliocytes (oligodendrogliocytes)).
Functions of the spinal ganglion:
1. Participation in reflex activity(the first neurons in the reflex arc circuit).
2. They are the initial link in the processing of afferent information.
3. Barrier function (blood-neural barrier).
4. They are a link in the circulation of cerebrospinal fluid.
Sources embryonic development dorsal ganglion:
1. Ganglion plate (gives rise to elements of the organ parenchyma).
2. Mesenchyme (gives rise to elements of the organ stroma).
Ganglia of the autonomic nervous system – located after the spinal cord, participate in the creation of autonomic arches.
Types of ganglia of the autonomic nervous system:
1. Sympathetic:
1) Paravertebral;
2) Prevertebral;
2. Parasympathetic:
1) Intraorgan (intramural);
2) Periorgan (paraorgan);
3) Vegetative nodes head (along the cranial nerves).
The structure of the ganglia of the autonomic nervous system:
1. Stroma: structure similar to the stroma of the spinal ganglion.
2.1. Parenchyma of the sympathetic ganglia: neurons located randomly throughout the ganglion + satellite cells + connective tissue capsule.
1) large long-axonal multipolar efferent adrenergic neurons
2) small equal-processed multipolar associative adrenergic intensely fluorescent (MIF) neurons
3) preganglionic myelin cholinergic fibers (axons of neurons of the lateral horns of the spinal cord)
4) postganglionic non-myelinated adrenergic nerve fibers (axons of large ganglion neurons)
5) intraganglionic unmyelinated associative nerve fibers (axons of MIF neurons).
2.2. Parenchyma of the parasympathetic ganglia:
1) long-axonal multipolar efferent cholinergic neurons (Dogel type I).
2) long-dendritic multipolar afferent cholinergic neurons (Dogel type II): dendrite - to the receptor, axon - to types 1 and 3.
3) equilateral multipolar associative cholinergic neurons (Dogel type III).
4) preganglionic myelinated cholinergic nerve fibers (axons of the lateral horns of the spinal cord).
5) postganglionic non-myelinated cholinergic nerve fibers (axons of Dogel type I neurons).
Functions of the ganglia of the autonomic nervous system:
1. sympathetic:
1) Conducting impulses to the working bodies (2.1.1)
2) Propagation of the impulse within the ganglion (inhibitory effect) (2.1.2)
2. Parasympathetic:
1) Conducting an impulse to the working bodies (2.2.1)
2) Conduction of impulses from interoreceptors within local reflex arcs (2.2.2)
3) propagation of the impulse within or between ganglia (2.2.3).
Sources of embryonic development of ganglia of the autonomic nervous system:
1. Ganglion plate (neurons and neuroglia).
2. Mesenchyme (connective tissue, blood vessels).
Located along the way spinal column. Covered with a connective tissue capsule. Partitions go inward from it. Vessels penetrate through them into the spinal node. Nerve fibers are located in the middle part of the node. Myelin fibers predominate.
In the peripheral part of the node, as a rule, pseudounipolar sensory nerve cells are located in groups. They constitute 1 sensitive link of the somatic reflex arc. They have a round body, a large nucleus, wide cytoplasm, and well-developed organelles. Around the body there is a layer of glial cells - mantle gliocytes. They constantly support the vital activity of cells. Around them there is a thin connective tissue membrane, which contains blood and lymphatic capillaries. This shell performs protective and trophic functions.
The dendrite is part of the peripheral nerve. At the periphery it forms a sensitive nerve fiber where the receptor begins. Another neuritic axon extends towards the spinal cord, forming the dorsal root, which enters the spinal cord and ends in the gray matter of the spinal cord. If you delete a node. Sensitivity will suffer if the posterior root is crossed - the same result.
Meninges of the brain and spinal cord. The brain and spinal cord are covered by three membranes: soft, directly adjacent to the brain tissue, arachnoid and hard, which borders bone tissue skull and spine.
Soft meninges directly adjacent to the brain tissue and delimited from it by the marginal glial membrane. The loose fibrous connective tissue contains membranes large number blood vessels, feeding the brain, numerous nerve fibers, terminal apparatus and single nerve cells.
Arachnoid presented thin layer loose fibrous connective tissue. Between it and the pia mater lies a network of crossbars consisting of thin bundles of collagen and thin elastic fibers. This network connects the shells with each other. Between the pia mater, which follows the relief of brain tissue, and the arachnoid, which runs along elevated areas without going into the recesses, there is a subarachnoid (subarachnoid) space, permeated with thin collagen and elastic fibers that connect the membranes to each other. The subarachnoid space communicates with the ventricles of the brain and contains cerebrospinal fluid.
Dura mater formed by dense fibrous connective tissue containing many 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 the epidural space, filled with a layer of loose fibrous connective tissue, which provides it with some mobility. Between the dura mater and the arachnoid membrane is the subdural space. The subdural space contains a small amount of fluid. The membranes on the side of the subdural and subarachnoid space are covered with a layer of flat cells of glial nature.
In the anterior part of the spinal cord, white matter is located and contains nerve fibers that form the spinal cord pathways. The middle part contains gray matter. The halves of the spinal cord are separated in front the median anterior fissure, and behind the posterior connective tissue septum.
In the center of the gray matter is the central canal of the spinal cord. It connects to the ventricles of the brain, is lined with ependyma and is filled cerebrospinal fluid, which constantly circulates and is formed.
In gray matter contains nerve cells and their processes (myelinated and unmyelinated nerve fibers) and glial cells. Most nerve cells are located diffusely in the gray matter. They are intercalary and can be associative, commissural, or projection. Some nerve cells are grouped into clusters that are similar in origin and function. They are designated cores gray matter. In the dorsal horns, intermediate zone, medial horns, the neurons of these nuclei are intercalary.
Neurocytes. Cells similar in size, fine structure and functional significance lie in the gray matter in groups called nuclei. Among the neurons of the spinal cord, the following types of cells can be distinguished: radicular cells(neurocytus radiculatus), the neurites of which leave the spinal cord as part of its anterior roots, internal cells(neurocytus interims), the processes of which end in synapses within the gray matter of the spinal cord, and tuft cells(neurocytus funicularis), the axons of which pass through the white matter in separate bundles of fibers carrying nerve impulses from certain nuclei of the spinal cord to its other segments or to the corresponding parts of the brain, forming pathways. Individual areas of the gray matter of the spinal cord differ significantly from each other in the composition of neurons, nerve fibers and neuroglia.
There are anterior horns, posterior horns, an intermediate zone, and lateral horns.
In the hind horns allocate spongy layer. It contains a large number of small interneurons. Gelatinous layer(substance) contains glial cells and a small number of interneurons. In the middle part of the posterior horns is located dorsal horn nucleus, which contains tufted neurons (multipolar). Tufted neurons are cells whose axons extend into the gray matter of the opposite half, penetrate it and enter the lateral cords of the white matter of the spinal cord. They form ascending sensory pathways. At the base of the posterior horn in the inner part is located dorsal or thoracic nucleus (Clark's nucleus). Contains tufted neurons, the axons of which extend into the white matter of the same half of the spinal cord.
In the intermediate zone allocate medial nucleus. Contains fascicle neurons, the axons of which also extend into the lateral cords of the white matter, the same halves of the spinal cord, and form ascending pathways that carry afferent information from the periphery to the center. Lateral nucleus contains radicular neurons. These nuclei are the spinal centers of autonomic reflex arcs, mainly sympathetic. The axons of these cells emerge from the gray matter of the spinal cord and participate in the formation of the anterior roots of the spinal cord.
In the dorsal horns and the medial part of the intermediate zone there are intercalary neurons that constitute the second intercalary link of the somatic reflex arc.
Front horns contain large nuclei in which large multipolar root neurons are located. They form medial nuclei, which are equally well developed throughout the spinal cord. These cells and nuclei innervate the skeletal muscle tissue of the body. Lateral nuclei better developed in the cervical and lumbar regions. They innervate the muscles of the limbs. The axons of motor neurons extend from the anterior horns beyond the spinal cord and form the anterior roots of the spinal cord. They are part of a mixed peripheral nerve and end at a neuromuscular synapse on a skeletal muscle fiber. The motor neurons of the anterior horns constitute the third effector link of the somatic reflex arc.
Own apparatus of the spinal cord. In the gray matter, especially in the dorsal horns and intermediate zone, a large number of tufted neurons are located diffusely. The axons of these cells extend into the white matter and immediately at the border with the gray matter they divide into 2 processes in a T-shape. One goes up. And the other one is down. They then return back to the gray matter in the anterior horns and end in the motor neuron nuclei. These cells form their own spinal cord apparatus. They provide communication, the ability to transmit information within the adjacent 4 segments of the spinal cord. This explains the synchronous response of the muscle group.
White matter contains mainly myelinated nerve fibers. They go in bundles and form the pathways of the spinal cord. They provide communication between the spinal cord and parts of the brain. The bundles are separated by glial septa. At the same time, they distinguish ascending paths, which carry afferent information from the spinal cord to the brain. These paths are located in posterior funiculi white matter and peripheral parts of the lateral funiculi. Descending pathways These are effector pathways, they carry information from the brain to the periphery. They are located in the anterior cords of the white matter and in the inner part of the lateral cords.
Regeneration.
Gray matter regenerates very poorly. White matter is capable of regenerating, but this process is very long. If the body is saved nerve cell. Then the fibers regenerate.
DEVELOPMENT.
1. Neural tube – CNS – Gray and white substance Vegetative
2. Neural crest - Peripheral. – Ganglion system
nervous nerves and and
nervous system somatic
graduation nervous s-ma
Table of derivatives and classification of the nervous system
During development, neural crest cells are distributed along the sides of the neural tube and therefore further develop in the lateral sections.
At the same time, neuroglial cells and sensitive pseudounipolar neurons are released from the neural crest cells on the sides of the NT, the axons of which grow into the gray matter of the spinal cord.
Some neural crest cells quickly move deep into the body and penetrate the wall of developing organs, or between them. These are the ganglia of the autonomic nervous system.
STRUCTURE OF GRAY AND WHITE MATTER
SPINAL CORD
The spinal cord consists of symmetrical halves. The gray matter is connected by gray commissures, and the white matter is divided in front by a fissure and in the back by a connective tissue septum.
The gray matter in the middle of the SC resembles the letter “H” and there are: -
Dorsal - posterior
Lateral – lateral
Ventral - anterior horns.
In the center runs the spinal canal, filled with cerebrospinal fluid. Its walls are lined with ependymocytes.
Gray matter consists of neurocyte bodies surrounded by astrocytes and a dense network of their processes. The axons of neurocytes are barely covered with myelin, and the dendrites are without myelin.
Among the cells are:
Radicular - axons are part of the anterior root
Internal - processes located within the spinal cord
Tufted - shaped bundles of white matter and go up or down.
The bodies of these cells lie in groups and are called nuclei.
In the hind horns(from the periphery to the center) distinguish between the spongy layer, gelatinous substance, nucleus proper and thoracic nucleus
All neurocytes of the dorsal horns are associative in function.
The spongy layer contains small neurons and large gliocytes.
Gelatinous substance – neuroglia also predominate.
The nucleus proper lies in the center of the dorsal horn. This is a collection of cell bodies of large neurons, the axons of which pass to the other side and rise up into the brain.
The cells of the thoracic nucleus are also large. Their axons go to the cerebellum in the white matter on the same side of the spinal cord.
In the area lateral horns There are medial and lateral nuclei involved in the sympathetic division of the autonomic system. These are association neurons of the autonomic nervous system.
Cells of the medial nucleus transmit information to the cerebellum, and the lateral nucleus transmits information to the periphery as part of the anterior roots for innervation of internal organs.
Front horns the widest and contain large cells from 100 to 140 microns, which lie in the form of five cores. These are motor neurons. Their processes form the anterior roots of the spinal cord, which control skeletal muscles. Therefore, the nuclei are called motor.
There are medial and lateral groups of nuclei.
Medial – innervated muscles of the back and torso
Lateral - innervated muscles of the limbs and therefore developed in the cervical and lumbar regions.
White matter– contains fibers and does not contain tet neurocytes at all. Fibers are processes of cells partially covered with a membrane. The processes are grouped into bundles by function and therefore distinguish bundles or pathways that carry information from sensory, motor or interneurons. Sensory pathways are afferent pathways, motor pathways are efferent pathways. Examples: sensitive pathways – tender and wedge-bundle of Flexig-Gowers; pyramidal path - motor - pyramidal path.
On the outside, the white matter of the spinal cord is covered with a layer of collagen and elastic fibers and glychocytes. This is the pia mater. Many vessels from it penetrate into the spinal cord.
SPINAL GANGLION (sensory ganglia)
This is a thickening along the dorsal roots of the spinal cord.
The body is formed by a dense connecting capsule, from which partitions with vessels extend inward.
The ganglion is a cluster of bodies of pseudounisexual senses. neurocytes, which lie more on the periphery, closer to the vessels of the capsule.
The body of each neuron is surrounded by oligodendrocytes, which are called mantle cells. As always their functions:
Nutritious;
Protective
Support
Demarcation.
Neurocytes- these are modified biopolar cells, the axons of which enter the SC, forming its dorsal roots. Their dendrites bring here information from receptors from the periphery.
Note that in supporting and protecting the peripheral nervous system connective tissue plays an active role compared to the central nervous system. This also applies to the connective tissue sheaths of all peripheral nerves, which include:
Epineurium – outer shell;
Perineurium – separates bundles of fibers (pathways);
Endoneurium – isolates individual processes.
The spinal cord and spinal ganglion, forming a chain of neurons, are responsible for congenital unconditioned reflexes body.
Somatic reflex arc
Three-neuron reflex arc-
This is a chain of three neurons:
Sens.pseudo-unit.N.SG
Associate.n.pos.horns SM
Engine n. front horns SM
Receptor – dendrite – body
Two-neuron somatic reflex arc- this is a chain of two neurocytes: sensory.
engine
Remove from the previous description interneuron
Now remember the classic example, when touching a hot object we withdraw our hand - this is an example of a somatic reflex arc, but look at this finger - it turned red, and this is the work of the autonomic nervous system, it turns out that the sensitive neuron transmitted information to both the somatic and autonomic nervous system system.
It can only be like this:
VEGETATIVE REFLECTOR ARC (sympathetic department)
Receptor – dendrite…..etc.
In the autonomic reflex arc, pre- and postganglionic fibers are distinguished. Pre are myelinated (white), and postganglionic are non-myelinated (gray).
AUTONOMIC GANGLION
1) arrangement of cells
2) multipolar cells
3) all 4 types (MYTH) (sympathetic)
This is an accumulation of neurocyte bodies, which, unlike the spinal ganglion, are multipolar and can be different in function - motor, associative, sensory and secretory.
Included autonomic ganglion distinguish:
According to Dogel: 1). double long axon
2). equiprotrusion.sense.
3). equal length ass.
Based on the presence of cells of different functions, the reflex arc can be closed within the ganglia themselves, without going beyond the boundaries of the autonomic nervous system, for which it received the name autonomous, independent.
PRINCIPAL STRUCTURE OF THE VEGETATIVE
NERVOUS SYSTEM.
Associated nuclei of the lateral horns of the SM
Chains of pre- and paravertebral ganglia along the spine
Parasympathetic department:
Center – 3,7,9,10 craniocerebral.
Periphery. – intramural plexuses inside organs – intramural ganglia.
