The sympathetic division of the central nervous system is responsible for Features of the sympathetic nervous system. Phylogeny of the autonomic nervous system
Cat. located at a considerable distance from the innervated organs. sympathetic nervous system It is divided into central, located in the spinal cord, and peripheral, including numerous nerve branches and nodes connected to each other. The centers of the sympathetic system are located in the lateral horns of the thoracic and lumbar segments. Sympathetic fibers exit the spinal cord along the I-II thoracic to II-IV lumbar region. In their course, the sympathetic fibers are separated from the somatic motor fibers and then, in the form of white connecting branches, enter the nodes of the border sympathetic trunk.
The peripheral part of the sympathetic nervous system is formed by sensitive neurons with their processes located in the paravertebral nodes.
The sympathetic nervous system is activated during stress reactions. It is characterized by a generalized influence, while sympathetic fibers innervate all organs without exception.
The main mediator secreted by preganglionic fibers is acetylcholine, and by postganglionic fibers - norepinephrine.
^ Own nuclei of the brain stem.
The nucleus of a thin and wedge-shaped tubercle - switch. nuclei, axons cat. form outer arcuate fibers;
The core of the olive is associated with the balance of the body, vestibular and auditory senses.
Dorsal nucleus of the trapezoid body - auditory sense .;
The core of the blue spot is the center of homeostasis. The neurons of this nucleus synthesize norepinephrine;
The raphe nucleus is the synthesis of serotonin.
midbrain:
The red nucleus is a nucleus with a large number of multipolar neurons, cat axons. form the red nuclear-spinal tract;
Black substance - contains the black pigment melanin. Its axons form the tectospinal tract.
^ Specific features of the nuclei of the hypothalamus.
1) front reg. - represented by the preoptic field, optic chiasm and optic tract. Cores:
preoptic;
supraoptic;
Paraventricular.
2) middle reg. - comp. from a gray hillock, funnel, on a cat. the pituitary gland is located. It connects to the hypothalamus by the hypothalamic-pituitary bundle. Cores:
Sulphurous;
Funnel nuclei.
3) back reg. - represented by paired mastoid bodies. Cores:
posterior nuclei;
Nuclei of the mastoid bodies.
Accumulations of nerve cells in these areas form more than 30 pairs of nuclei of the hypothalamus. The cells of these nuclei produce a neurosecretion, a cat. along the processes of the same cells it is transported to the region. neurohypophysis.
Thus, the supraoptic and paraventricular nuclei produce vasopressin and oxytocin. These hormones are transported to the cells of the posterior pituitary along the axons, comp. hypothalamic-pituitary tract. The hormone vasopressin has a vasoconstrictor and antideuretic effect. Oxytocin stimulates the contractility of the muscles of the uterus, enhances lactation, inhibits the development and function of the corpus luteum, affects the change in the tone of the smooth muscles of the gastrointestinal tract.
In the preoptic nucleus arr. releasing hormone that stimulates the production of luteinizing hormone in the adenohypophysis, cat. controls the activity of the sex glands.
The middle group of nuclei controls water, fat and carbohydrate metabolism, affects the level of sugar in the blood, the ionic balance of the body, the permeability of blood vessels and cell membranes. Here the centers of hunger and saturation are localized.
The posterior group of nuclei is involved in thermoregulation, contains centers that coordinate the activity of the sympathetic nervous system.
^ The spinal cord, its structure. Sheaths of the spinal cord.
Each corresponds to a pair of anterior and a pair of posterior roots. There are 31 pairs of neurotomes: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal.
In the upper sections, each neurotome resp. the serial number of the vertebra (sclerotome), in the lower cervical there is an excess of one vertebra, in the upper thoracic - by two, in the lower thoracic - by 3, etc.
In the spinal cord, the anterior median fissure, anterior lateral grooves, from the cat. the anterior motor roots emerge. The posterior surface contains the posterior median sulcus and the posterior lateral sulci. The posterior root, sensitive, approaches the posterior lateral grooves.
The posterior median sulcus forms the dorsal septum, thus the spinal cord consists of two halves connected by a commissure, cat. represented by white and gray spikes. In the spinal cord, a cervical and lumbosacral thickening is distinguished. They acc. discharge of the roots that form the plexus, the cat. innervate the upper and lower limbs. In the center of the spinal cord is the central canal, the cat. represented. a narrow reduced cavity filled with cerebrospinal fluid.
The spinal cord ends with a cerebral cone, a cat. passes into the reduced part - the terminal thread.
Numerous branches depart from the cerebral cone. axons of neurons - cauda equina.
The anterior root, extending from each segment of the spinal cord, is formed by axons, motor neurons. The anterior root approaches the posterior horns of the gray matter, it is formed by the axons of the senses. neurons, cat. lie outside the spinal cord in the spinal nodes or ganglia.
Outside, the spinal cord is covered with three membranes:
External or fibrous (dura mater) - formed by a dense connection. tissue with a large number of collagen and elastic. fibers. Separates the spinal cord from the spinal canal;
The middle or arachnoid membrane forms small depressions - lacures, and forms supracarachnoid and subarachnoid spaces filled with cerebrospinal fluid - cerebrospinal fluid;
The inner (pia mater) contains blood vessels that provide nutrition to the spinal cord.
^ Structural organization of white matter in the CNS.
There are own bundles and conductive paths. Own bundles provide communication between individual neurotomes. There are anterior, posterior and lateral proper bundles. They are formed by commissural fibers.
On the dorsal side there are predominantly ascending fibers, on the ventral side - descending.
Pathways carry information in ascending and descending positions.
In the anterior funiculus, a trace is distinguished. pathways:
The anterior corticospinal tract is descending. From the lower layers of the motor cortex of the telencephalon, it is formed by the axons of the lower layers of the cortex. It ends on the motor nuclei of the anterior horns of the spinal cord. Provide voluntary motor reactions;
The spinal tract is descending. It starts from the substantia nigra of the midbrain and ends at the motor. nuclei of the spinal cord. Provide regulation of skeletal muscle tone, body balance.
Rear cord:
Thin beam;
Wedge bundle.
These are ascending pathways that conduct nerve impulses from the nuclei of the posterior horn of the spinal cord (from the thoracic and proper nucleus of the spinal cord) and end at the nuclei of the thin and sphenoid tubercle of the medulla oblongata.
Formed by axons of neurons of the chest and own. nuclei. Carry out skin (extroceptive) and muscular (propreoceptive) feelings. into the medulla oblongata. A thin beam conducts feelings. from the lower extremities, wedge-shaped - from the upper body and upper extremities.
Lateral cord:
The lateral cortical-spinal tract is an analogue of the anterior cortical-spinal tract;
Krasnonuclear-spinal - descending. It starts from the red nucleus of the midbrain, ends at the motor. nuclei of the spinal cord. Provide involuntary movements. reactions;
The spinal thalamic pathway is ascending. Formed by axons of the chest and own. kernels. It starts from the nuclei of the posterior horn, ends at the nuclei of the thalamus. Conducts pain, temperature and tactile feelings.;
Anterior and posterior spinal tracts - start from the nuclei of the posterior horn (from the thoracic and proper nuclei), are formed by their axons. They terminate at the nuclei of the cerebellum. Ascending path. Provide holding propreceptive senses.;
Medial longitudinal bundle - ascending and descending fibers. Formed by neurons of the nuclei of the lateral horn. Conducts visceral sensitivity (sensitivity of internal organs);
Predverno-spinal - descending. It starts from the nuclei of the vestibule of the bridge, ends on the motor nuclei of the spinal cord. Provides balance to the body.
Olivo-spinal. starts from the nuclei of the olive of the medulla oblongata, ends at the motor. nuclei of the spinal cord. Associated with the balance of the body and the vestibular senses.
Brain
Brain stem - medulla oblongata, pons, cerebellum, midbrain.
1) medulla oblongata
External arcuate fibers - originate from a thin and wedge-shaped bundle, conduct propreceptive sensitivity to the lower cerebellar peduncle;
Internal arcuate fibers - originate from a thin and wedge-shaped bundle, form a medial loop;
Medial loop - passes as part of the tegmentum of the medulla oblongata, bridge, midbrain, and ends at the nuclei of the ventral complex of the thalamus. Delivers propreceptive and extraceptive sensitivity to the thalamus.
The corticonuclear pathway is descending. It starts from the lower layers of the cortex, ends at the nuclei of the base of the bridge. It provides arbitrary movements of the tongue, that is, it is associated with the motor skills of the tongue;
The cortical-bridge-cerebellar pathway is descending. It originates from the lower layers of the cortex. After passing through the internal capsule, it goes into the base of the midbrain, the bridge, then, as part of the middle cerebellar peduncle, it passes into the cerebellum and ends at the nuclei of the cerebellum;
Trinity loop - ascending. It originates from the complex of nuclei of the trigeminal nerve, passes as part of the tegmentum of the bridge and the midbrain, and ends at the ventral complex of the nuclei of the thalamus. Conducts temperature, pain and tactile sensitivity of the head and face;
Trapezoidal body. Formed by axons of the dorsal nucleus of the trapezoid body, transverse bundles of auditory fibers located in the thickness of the bridge;
Lateral loop - ascending. It originates from the auditory nuclei of the bridge - this is the nucleus of the cochlea, the nucleus of the trapezoid body. Passes as part of the pontine tegmentum and midbrain and ends at the nuclei of the medial geniculate body of the thalamus.
telencephalon:
1) projection fibers - cortical-spinal (motor nuclei of the spinal cord), cortical-nuclear (basic stem structures), cortical-bridge-cerebellar (cerebellar nuclei), extrapyramidal system. (main brainstem, cords of the spinal cord);
2) commissural fibers - the corpus callosum (connection between the hemispheres), anterior and posterior cerebral commissures (connection between the left and right temporal lobes, between the halves of the spinal cord); 3) associative fibers - arcuate fibers (between areas in the cerebral cortex and in the cerebellum), bundles (between the lobes of the brain), own. bundles of the spinal cord (between segments of the spinal cord).
^ Structural organization of the cerebral cortex (cytoarchitectonics).
Molecular - contains few cells and many fibers, providing protective functions of the cortex;
Outer granular layer - many small cells-grains;
Outer pyramidal layer - contains pyramidal neurons;
Inner granular layer;
Inner pyramidal layer - giant pyramidal cells (Betz cells);
Two polyform layers - different cells, the basis of the cat. are spindle-shaped cells.
Neurons of the inner pyramidal and polymorphic layers of forms. descending syst. fibers of the pyramidal bundle. The outer pyramidal layer is its axons of forms. associative systems. fibers. The outer and inner granular layer - perceiving nerve impulses, distributes them throughout the entire diameter of the cortex.
^ Structural organization of the cerebellar cortex.
The outer molecular layer - few nerve cells, mainly comp. from white matter; processes of pear-shaped neurons and glial cells;
Ganglionic layer - comp. of the pear-shaped neurons located in one row (Purkinje cells) - the largest neurons of the cerebellar cortex. Each cell forms a dendritic tree lying in the molecular layer, where the axons of granular cells continue. Axons provide efferent output from the cerebellar cortex to its nuclei;
The inner granular layer is a large number of densely spaced small granular neurons. These cells are permeated with transverse fibers, the cat. provide a connection of the cerebellar cortex along the diameter.
^ Structural organization of the bridge.
V pair - trigeminal nerve - providing. innervation of the mimic muscles of the face;
VI pair - abducens nerve - providing. innervation of the skeletal muscles of the eyeball;
VII pair - facial nerve - innervation of the masticatory muscles;
VIII pair - the vestibulocochlear nerve - brings auditory and vestibular sensitivity to the brain.
On the dorsal surface of the medulla oblongata and the bridge, a rhomboid fossa is distinguished. This is the bottom of the 4th ventricle. Here a trace is distinguished. structures:
Posterior median sulcus;
Posterior lateral groove;
Lateral pockets containing the vestibular field;
Medial eminence, which contains the facial tubercle;
The core of the blue spot.
In the region The medulla oblongata contains the triangle of the hypoglossal nerve and the triangle of the vagus nerve.
The roof of the 4th ventricle forms. a pair of upper and a pair of lower medullary sails. The cavity of the 4th ventricle is filled with CSF.
^ Structural organization of the neuron.
The precursor of the nerve cell yavl. neuroblasts. Neurons comp. from the body and processes, there are short, strongly branching processes - dendrites, and long, weakly branching - axons.
Comp. The nerve cell includes organelles of the general plan:
Eps - syst. channels, cisterns, tubules penetrating the entire cytoplasm. There are smooth and rough eps. Smooth col. transport of fats and carbohydrates, rough - transport of proteins;
Golgi apparatus - syst. canals with ampullar extensions at the ends, in the region. cat. bubbles filled with various secrets are located. He takes part in the synthesis, accumulation and transport decomp. substances, carries out the excretion of substances outside the cell, takes part in the formation of lysosomes;
Mitochondria are two-membrane, ext. the membrane forms invaginations - cristae. they contain their own DNA and ribosomes, provide the synthesis of ATP molecules;
Protein synthesizing apparatus – incl. granular eps, golgi complex, ribosomes, nucleus and nucleolus. They are forms. Nissl body or tigroid.
Nervous cell. yavl. factory for the production of protein. Many neurohormones and neurotransmitters are of a protein nature.
Dendrites are short, numerous, strongly branching, contain neurofibrils (organelles of a special plan, which carry out the transport of substances). Dendrites provide retrograde transport of substances.
Axons are long, weakly branching, there is one axon in the nerve cell. They also contain neurofibrils. It carries out axonal transport in the direction away from the cell body. Axons contain Schwann cells, cat. provide a supporting function. These are glial cells. do not adhere tightly to each other, between them there are spaces - the intercepts of Ranvier.
^ Structural organization of the medulla oblongata.
Anterior cords include the following. structures: pyramids, anterior median sulcus, anterior lateral sulcus. In the lower part of the medulla oblongata, the pyramids form a cross. As part of the pyramids, a pyramidal bundle passes into the cat. contains the cortico-spinal tract.
From the anterior funiculus, a trail of roots of cranial nerves departs:
IX pair - glossopharyngeal nerve - innervation of the mucous membrane of the tongue, pharynx, lingual tonsils;
X pair - vagus nerve - provides innervation of the posterior third of the tongue, parasympathetic innervation of all organs of the chest cavity and most of the organs abdominal cavity;
XII pair - hypoglossal nerve - providing. own innervation. tongue muscles.
Part lateral funiculus includes olives that contain the dorsal nucleus of the olive - the stem center of body balance. From them originates the olivo-spinal path. The olivo-spinal tract is descending, ending at the motor. nuclei of the spinal cord. The 11th pair of cranial nerves departs from the lateral cord - accessory nerve, cat. provide innervation of the sternocleidomastoid and trapezius muscles of the neck and back.
The posterior funiculus contains a posterior median sulcus, posterior lateral sulci, a thin and wedge-shaped bundle, which end in tubercles of a thin and wedge-shaped nucleus. The back of the medulla oblongata contains the fourth ventricle.
^ Structural organization of the midbrain.
The quadrigemina through the handles of the upper and lower colliculus conn. with the metathalamus. From the upper hillocks inf. enters the lateral geniculate bodies, from the lower - into the medial geniculate bodies. The quadrigemina forms the roof plate of the midbrain.
The midbrain peduncles are paired formations separated by the interpeduncular fossa. The roots of the III and IV pairs of cranial nerves depart from them. III pair - oculomotor nerve - providing. innervation of the skeletal muscles of the eyeball and muscles that expand and narrow the pupil, muscles, provide. eye accommodation. IV pair - trochlear nerve - innervation of the skeletal muscles of the eyeball.
Between the roof of the midbrain and the legs of the brain there is a narrow cavity - the aqueduct of the brain, cat. connects the cavity of the 3rd and 4th ventricles of the brain.
^ Thalamus. Projection, reticular and associative nuclei of the thalamus.
The thalamus are connected by interthalamic adhesions. By origin, the thalamus is a derivative of only the wing plate; therefore, only switching nuclei differ in this composition.
All nuclei of the thalamus can be divided into three groups:
1) sensory (specific) nuclei - all sensory information coming from the periphery is projected onto them. These nuclei are projected into the sensory region. cerebral cortex. They are collectors of all kinds of sensitivities. These include:
Anterior nuclei of the thalamus - receive inf. from the mastoid-thalamic bundle, associated with taste, olfactory and visceral senses. The fibers of these nuclei are projected in the fields of the limbic cortex, the lower part of the precentral gyrus (field-45);
Kernels of a ventral formation - accept inf. from the medial loop, trigeminal loop, spinothalamic pathway and conduct this information to the projection areas. The cortex of the telencephalon as part of the thalamic radiance and is projected in the precentral and superior frontal gyrus of the terminal in fields 3-6 (central sulcus, precentral gyrus, postcentral gyrus);
The nuclei of the medial geniculate body - they conduct auditory sensitivity to the cortex of the telencephalon. Get info. from the lateral loop, projected into fields -41, 42 and 22 (superior temporal gyrus) In these fields, the primary analysis of auditory sensitivity takes place;
Lateral geniculate body - receives inf. from the optic nerve, conducts visual sensitivity as part of visual radiation, is projected in field-16, 17 (spur groove of the occipital lobe).
2) associative nuclei - do not have special. afferents, accept inf. from other nuclei, from specific nuclei of the thalamus. They provide a connection between various thalamic growths and provide a primary integrative analysis of information coming to the thalamus. Associative nuclei are projected in the associative areas of the cortex.
These include:
Medial dorsal nucleus;
The nuclei of the pillow of the thalamus - higher mental. functions.
3) Nonspecific or reticular nuclei - midline nuclei, intralaminar (intralamellar) nuclei. They ensure the transmission of information to the cortex from the reticular formation of the trunk, supporting the regulation of the electrical activity of the cerebral cortex, maintaining the general level of wakefulness and selective excitability of the cortex, which is based on attention.
Functional classification of neurons.
Switching (associative, intercalary, inter-neurons) - Connection between sensory neurons and motor ones;
Motor (efferent, motor, centrifugal) - conduct impulses from the central nervous system to the working organs.
In the human body, the work of all its organs is closely interconnected, and therefore the body functions as a whole. The coordination of the functions of the internal organs is provided by the nervous system. In addition, the nervous system communicates between the external environment and the regulatory body, responding to external stimuli with appropriate reactions.
The perception of changes occurring in the external and internal environment occurs through nerve endings - receptors.
Any irritation (mechanical, light, sound, chemical, electrical, temperature) perceived by the receptor is converted (transformed) into the process of excitation. Excitation is transmitted along sensitive - centripetal nerve fibers to the central nervous system, where an urgent process of processing nerve impulses takes place. From here, impulses are sent along the fibers of centrifugal neurons (motor) to the executive organs that implement the response - the corresponding adaptive act.
This is how a reflex is performed (from the Latin "reflexus" - reflection) - a natural reaction of the body to changes in the external or internal environment, carried out through the central nervous system in response to irritation of the receptors.
Reflex reactions are diverse: this is the narrowing of the pupil in bright light, the release of saliva when food enters the oral cavity, etc.
The path along which nerve impulses (excitation) pass from receptors to the executive organ during the implementation of any reflex is called reflex arc.
The arcs of the reflexes close in the segmental apparatus of the spinal cord and brainstem, but they can also close higher, for example, in the subcortical ganglia or in the cortex.
Based on the foregoing, there are:
- central nervous system (brain and spinal cord) and
- peripheral nervous system, represented by nerves extending from the brain and spinal cord and other elements that lie outside the spinal cord and brain.
The peripheral nervous system is divided into somatic (animal) and autonomic (or autonomic).
- The somatic nervous system mainly carries out the connection of the organism with the external environment: the perception of stimuli, the regulation of movements of the striated muscles of the skeleton, etc.
- vegetative - regulates metabolism and the work of internal organs: heartbeat, peristaltic contractions of the intestine, secretion of various glands, etc.
The autonomic nervous system, in turn, based on the segmental principle of structure, is divided into two levels:
- segmental - includes sympathetic, anatomically associated with the spinal cord, and parasympathetic, formed by accumulations of nerve cells in the midbrain and medulla oblongata, nervous systems
- suprasegmental level - includes the reticular formation of the brain stem, hypothalamus, thalamus, amygdala and hippocampus - limbic-reticular complex
The somatic and autonomic nervous systems function in close interaction, however, the autonomic nervous system has some independence (autonomy), managing many involuntary functions.
CENTRAL NERVOUS SYSTEM
Represented by the brain and spinal cord. The brain is made up of gray and white matter.
Gray matter is a collection of neurons and their short processes. In the spinal cord, it is located in the center, surrounding the spinal canal. In the brain, on the contrary, gray matter is located on its surface, forming a cortex (cloak) and separate clusters, called nuclei, concentrated in white matter.
The white matter is under the gray and is composed of sheathed nerve fibers. Nerve fibers, connecting, compose nerve bundles, and several such bundles form individual nerves.
The nerves through which excitation is transmitted from the central nervous system to the organs are called centrifugal, and the nerves that conduct excitation from the periphery to the central nervous system are called centripetal.
The brain and spinal cord are surrounded by three membranes: hard, arachnoid and vascular.
- Solid - external, connective tissue, lines the internal cavity of the skull and spinal canal.
- The arachnoid is located under the solid - it is a thin shell with a small number of nerves and blood vessels.
- The choroid is fused with the brain, enters the furrows and contains many blood vessels.
Cavities filled with cerebral fluid form between the vascular and arachnoid membranes.
Spinal cord located in the spinal canal and has the appearance of a white cord, stretching from the occipital foramen to the lower back. Longitudinal grooves are located along the anterior and posterior surfaces of the spinal cord, in the center there is a spinal canal, around which gray matter is concentrated - an accumulation of a huge number of nerve cells that form the contour of a butterfly. On the outer surface of the cord of the spinal cord is located white matter- accumulation of bundles of long processes of nerve cells.
The gray matter is divided into anterior, posterior and lateral horns. In the anterior horns lie motor neurons, in the posterior - intercalary, which carry out the connection between sensory and motor neurons. Sensory neurons lie outside the cord, in the spinal nodes along the sensory nerves.
Long processes depart from the motor neurons of the anterior horns - the anterior roots, which form motor nerve fibers. The axons of sensitive neurons approach the posterior horns, forming the posterior roots, which enter the spinal cord and transmit excitation from the periphery to the spinal cord. Here, excitation switches to the intercalary neuron, and from it to short processes of the motor neuron, from which it is then transmitted along the axon to the working organ.
In the intervertebral foramina, the motor and sensory roots join to form mixed nerves, which then split into anterior and posterior branches. Each of them consists of sensory and motor nerve fibers. Thus, at the level of each vertebra, only 31 pairs of spinal nerves of a mixed type depart from the spinal cord in both directions.
The white matter of the spinal cord forms pathways that stretch along the spinal cord, connecting both its individual segments to each other, and the spinal cord to the brain. Some pathways are called ascending or sensitive, transmitting excitation to the brain, others are descending or motor, which conduct impulses from the brain to certain segments of the spinal cord.
The function of the spinal cord. The spinal cord has two functions:
- reflex [show]
.
Each reflex is carried out by a strictly defined part of the central nervous system - the nerve center. The nerve center is a collection of nerve cells located in one of the parts of the brain and regulating the activity of any organ or system. For example, the center of the knee-jerk reflex is located in the lumbar spinal cord, the center of urination is in the sacral, and the center of pupil dilation is in the upper thoracic segment of the spinal cord. The vital motor center of the diaphragm is localized in the III-IV cervical segments. Other centers - respiratory, vasomotor - are located in the medulla oblongata.
The nerve center consists of many intercalary neurons. It processes the information that comes from the corresponding receptors, and generates impulses that are transmitted to the executive organs - the heart, blood vessels, skeletal muscles, glands, etc. As a result, their functional state changes. To regulate the reflex, its accuracy, the participation of the higher parts of the central nervous system, including the cerebral cortex, is also necessary.
The nerve centers of the spinal cord are directly connected with the receptors and executive organs of the body. The motor neurons of the spinal cord provide contraction of the muscles of the trunk and limbs, as well as the respiratory muscles - the diaphragm and intercostals. In addition to the motor centers of skeletal muscles, there are a number of autonomic centers in the spinal cord.
- conductive [show] .
The bundles of nerve fibers that form the white matter connect the various parts of the spinal cord to each other and the brain to the spinal cord. There are ascending pathways, carrying impulses to the brain, and descending, carrying impulses from the brain to the spinal cord. According to the first, excitation that occurs in the receptors of the skin, muscles, and internal organs is carried along the spinal nerves to the posterior roots of the spinal cord, is perceived by the sensitive neurons of the spinal ganglions, and from here it is sent either to the posterior horns of the spinal cord, or as part of the white matter reaches the trunk, and then the cerebral cortex.
Descending pathways conduct excitation from the brain to the motor neurons of the spinal cord. From here, the excitation is transmitted along the spinal nerves to the executive organs. The activity of the spinal cord is under the control of the brain, which regulates spinal reflexes.
Brain located in the medulla of the skull. Its average weight is 1300 - 1400 g. After the birth of a person, brain growth continues up to 20 years. It consists of five sections: the anterior (large hemispheres), intermediate, middle, hindbrain and medulla oblongata. Inside the brain there are four interconnected cavities - cerebral ventricles. They are filled with cerebrospinal fluid. I and II ventricles are located in the cerebral hemispheres, III - in the diencephalon, and IV - in the medulla oblongata.
The hemispheres (the newest part in evolutionary terms) reach high development in humans, accounting for 80% of the mass of the brain. The phylogenetically older part is the brain stem. The trunk includes the medulla oblongata, the medullary (varoli) bridge, the midbrain and the diencephalon.
Numerous nuclei of gray matter lie in the white matter of the trunk. The nuclei of 12 pairs of cranial nerves also lie in the brainstem. The brain stem is covered by the cerebral hemispheres.
Medulla- a continuation of the dorsal and repeats its structure: furrows also lie on the anterior and posterior surfaces. It consists of white matter (conducting bundles), where clusters of gray matter are scattered - the nuclei from which the cranial nerves originate - from the IX to XII pair, including the glossopharyngeal (IX pair), vagus (X pair), innervating organs respiration, circulation, digestion and other systems, sublingual (XII pair). At the top, the medulla oblongata continues into a thickening - the pons varolii, and from the sides the lower legs of the cerebellum depart from it. From above and from the sides, almost the entire medulla oblongata is covered by the cerebral hemispheres and the cerebellum.
In the gray matter of the medulla oblongata lie vital centers that regulate cardiac activity, breathing, swallowing, carrying out protective reflexes (sneezing, coughing, vomiting, tearing), secretion of saliva, gastric and pancreatic juice, etc. Damage to the medulla oblongata can be the cause of death due to the cessation heart activity and respiration.
Hind brain includes the pons and cerebellum. The pons of Varolii is limited from below by the medulla oblongata, from above it passes into the legs of the brain, its lateral sections form the middle legs of the cerebellum. In the substance of the pons, there are nuclei from the V to VIII pair of cranial nerves (trigeminal, abducent, facial, auditory).
The cerebellum is located posterior to the pons and medulla oblongata. Its surface consists of gray matter (bark). Under the cerebellar cortex is white matter, in which there are accumulations of gray matter - the nucleus. The entire cerebellum is represented by two hemispheres, the middle part is a worm and three pairs of legs formed by nerve fibers, through which it is connected with other parts of the brain. The main function of the cerebellum is the unconditional reflex coordination of movements, which determines their clarity, smoothness and maintaining body balance, as well as maintaining muscle tone. Through the spinal cord along the pathways, impulses from the cerebellum arrive at the muscles. The activity of the cerebellum is controlled by the cerebral cortex.
midbrain located in front of the pons, it is represented by the quadrigemina and the legs of the brain. In the center of it is a narrow canal (aqueduct of the brain), which connects the III and IV ventricles. The cerebral aqueduct is surrounded by gray matter, which contains the nuclei of the III and IV pairs of cranial nerves. In the legs of the brain, pathways continue from the medulla oblongata and the pons to the cerebral hemispheres. The midbrain plays an important role in the regulation of tone and in the implementation of reflexes, due to which standing and walking are possible. The sensitive nuclei of the midbrain are located in the tubercles of the quadrigemina: the nuclei associated with the organs of vision are enclosed in the upper ones, and the nuclei associated with the organs of hearing are in the lower ones. With their participation, orienting reflexes to light and sound are carried out.
diencephalon occupies the highest position in the trunk and lies anterior to the legs of the brain. It consists of two visual hillocks, supratuberous, hypothalamic region and geniculate bodies. On the periphery of the diencephalon is white matter, and in its thickness - the nuclei of gray matter. Visual hillocks are the main subcortical centers of sensitivity: impulses from all receptors of the body arrive here along ascending paths, and from here to the cerebral cortex. In the hypothalamic part (hypothalamus) there are centers, the totality of which is the highest subcortical center of the autonomic nervous system, which regulates the metabolism in the body, heat transfer, and the constancy of the internal environment. Parasympathetic centers are located in the anterior hypothalamus, and sympathetic centers in the posterior. The subcortical visual and auditory centers are concentrated in the nuclei of the geniculate bodies.
The 2nd pair of cranial nerves - optic nerves - goes to the geniculate bodies. The brain stem is connected to the environment and to the organs of the body by cranial nerves. By their nature, they can be sensitive (I, II, VIII pairs), motor (III, IV, VI, XI, XII pairs) and mixed (V, VII, IX, X pairs).
forebrain consists of highly developed hemispheres and the middle part connecting them. The right and left hemispheres are separated from each other by a deep fissure, at the bottom of which lies the corpus callosum. The corpus callosum connects both hemispheres through long processes of neurons that form pathways.
The cavities of the hemispheres are represented by the lateral ventricles (I and II). The surface of the hemispheres is formed by gray matter or the cerebral cortex, represented by neurons and their processes, under the cortex lies white matter - pathways. Pathways connect individual centers within the same hemisphere, or the right and left halves of the brain and spinal cord, or different floors of the central nervous system. In the white matter there are also clusters of nerve cells that form the subcortical nuclei of the gray matter. Part of the cerebral hemispheres is olfactory brain with a pair of olfactory nerves departing from it (I pair).
The total surface of the cerebral cortex is 2000-2500 cm 2, its thickness is 1.5-4 mm. Despite its small thickness, the cerebral cortex has a very complex structure.
The cortex includes more than 14 billion nerve cells, arranged in six layers that differ in shape, size of neurons and connections. The microscopic structure of the cortex was first studied by V. A. Betz. He discovered pyramidal neurons, which were later given his name (Betz cells).
In a three-month-old embryo, the surface of the hemispheres is smooth, but the cortex grows faster than the brain box, so the cortex forms folds - convolutions limited by furrows; they contain about 70% of the surface of the cortex. Furrows divide the surface of the hemispheres into lobes.
There are four lobes in each hemisphere:
- frontal
- parietal
- temporal
- occipital.
The deepest furrows are the central one, which runs across both hemispheres, and the temporal one, which separates the temporal lobe of the brain from the rest; the parieto-occipital sulcus separates the parietal lobe from the occipital lobe.
Anterior to the central sulcus (Roland sulcus) in the frontal lobe is the anterior central gyrus, behind it is the posterior central gyrus. The lower surface of the hemispheres and the brain stem is called the base of the brain.
Based on experiments with partial removal of different parts of the cortex in animals and observations on people with affected cortex, it was possible to establish the functions of different parts of the cortex. So, in the cortex of the occipital lobe of the hemispheres is the visual center, in the upper part of the temporal lobe - the auditory. The musculocutaneous zone, which perceives irritations from the skin of all parts of the body and controls the voluntary movements of the skeletal muscles, occupies a portion of the cortex on both sides of the central sulcus.
Each part of the body corresponds to its own section of the cortex, and the representation of the palms and fingers, lips and tongue, as the most mobile and sensitive parts of the body, occupies in a person almost the same area of the cortex as the representation of all other parts of the body combined.
In the cortex there are centers of all sensitive (receptor) systems, representations of all organs and parts of the body. In this regard, centripetal nerve impulses from all internal organs or parts of the body are suitable for the corresponding sensitive areas of the cerebral cortex, where analysis is carried out and a specific sensation is formed - visual, olfactory, etc., and it can control their work.
A functional system consisting of a receptor, a sensitive pathway and a cortical zone where this type of sensitivity is projected, I. P. Pavlov called the analyzer.
The analysis and synthesis of the received information is carried out in a strictly defined area - the zone of the cerebral cortex. The most important areas of the cortex are motor, sensory, visual, auditory, olfactory. The motor zone is located in the anterior central gyrus in front of the central sulcus of the frontal lobe, the zone of skin-muscular sensitivity is located behind the central sulcus, in the posterior central gyrus of the parietal lobe. The visual zone is concentrated in the occipital lobe, the auditory zone is in the superior temporal gyrus of the temporal lobe, and the olfactory and gustatory zones are in the anterior temporal lobe.
In the cerebral cortex, many nervous processes are carried out. Their purpose is twofold: the interaction of the body with the external environment (behavioral reactions) and the unification of body functions, the nervous regulation of all organs. The activity of the cerebral cortex of humans and higher animals was defined by I.P. Pavlov as the highest nervous activity, which is a conditioned reflex function of the cerebral cortex.
| Nervous system | Central nervous system | |||
| brain | spinal cord | |||
| large hemispheres | cerebellum | trunk | ||
| Composition and structure | Lobes: frontal, parietal, occipital, two temporal. The cortex is formed by gray matter - the bodies of nerve cells. The thickness of the bark is 1.5-3 mm. The area of the cortex is 2-2.5 thousand cm 2, it consists of 14 billion bodies of neurons. White matter is made up of nerve fibers |
The gray matter forms the cortex and nuclei within the cerebellum. Consists of two hemispheres connected by a bridge |
Educated:
It consists of white matter, in the thickness are the nuclei of gray matter. The trunk passes into the spinal cord |
Cylindrical cord 42-45 cm long and about 1 cm in diameter. Passes in the spinal canal. Inside it is the spinal canal filled with fluid. Gray matter is located inside, white - outside. Passes into the brain stem, forming a single system |
| Functions | Carries out higher nervous activity (thinking, speech, second signaling system, memory, imagination, ability to write, read). Communication with the external environment occurs with the help of analyzers located in the occipital lobe (visual zone), in the temporal lobe (auditory zone), along the central sulcus (musculoskeletal zone) and on inner surface cortex (gustatory and olfactory zones). Regulates the work of the whole organism through the peripheral nervous system |
Regulates and coordinates body movements muscle tone. Carries out unconditional reflex activity (centers of innate reflexes) |
Connects the brain with the spinal cord into a single central nervous system. In the medulla oblongata there are centers: respiratory, digestive, cardiovascular. The bridge connects both halves of the cerebellum. The midbrain controls reactions to external stimuli, muscle tone (tension). The diencephalon regulates metabolism, body temperature, connects body receptors with the cerebral cortex |
Operates under the control of the brain. Arcs of unconditioned (innate) reflexes pass through it, excitation and inhibition during movement. Pathways - white matter connecting the brain to the spinal cord; is a conductor of nerve impulses. Regulates the work of internal organs through the peripheral nervous system Spinal nerves control voluntary movements of the body |
PERIPHERAL NERVOUS SYSTEM
The peripheral nervous system is formed by nerves emerging from the central nervous system, and nerve nodes and plexuses located mainly near the brain and spinal cord, as well as next to various internal organs or in the wall of these organs. In the peripheral nervous system, somatic and autonomic divisions are distinguished.
somatic nervous system
This system is formed by sensory nerve fibers that go to the central nervous system from various receptors, and motor nerve fibers that innervate skeletal muscles. The characteristic features of the fibers of the somatic nervous system are that they are not interrupted anywhere along the entire length from the central nervous system to the receptor or skeletal muscle, they have a relatively large diameter and a high speed of excitation conduction. These fibers make up most of the nerves that emerge from the CNS and form the peripheral nervous system.
There are 12 pairs of cranial nerves that emerge from the brain. The characteristics of these nerves are given in Table 1. [show] .
Table 1. Cranial nerves
| Pair | Name and composition of the nerve | The exit point of the nerve from the brain | Function |
| I | Olfactory | Large hemispheres of the forebrain | Transmits excitation (sensory) from the olfactory receptors to the olfactory center |
| II | visual (sensory) | diencephalon | Transmits excitation from retinal receptors to the visual center |
| III | Oculomotor (motor) | midbrain | Innervates the eye muscles, provides eye movements |
| IV | Block (motor) | Same | Same |
| V | Trinity (mixed) | Bridge and medulla oblongata | Transmits excitation from the receptors of the skin of the face, mucous membranes of the lips, mouth and teeth, innervates the masticatory muscles |
| VI | Abductor (motor) | Medulla | Innervates the rectus lateral muscle of the eye, causes eye movement to the side |
| VII | Facial (mixed) | Same | Transmits excitation from the taste buds of the tongue and oral mucosa to the brain, innervates the mimic muscles and salivary glands |
| VIII | auditory (sensitive) | Same | Transmits stimulation from inner ear receptors |
| IX | Glossopharyngeal (mixed) | Same | Transmits excitation from taste buds and pharyngeal receptors, innervates the muscles of the pharynx and salivary glands |
| X | Wandering (mixed) | Same | Innervates the heart, lungs, most of the abdominal organs, transmits excitation from the receptors of these organs to the brain and centrifugal impulses in the opposite direction |
| XI | Additional (motor) | Same | Innervates the muscles of the neck and neck, regulates their contractions |
| XII | Hyoid (motor) | Same | Innervates the muscles of the tongue and neck, causes their contraction |
Each segment of the spinal cord gives off one pair of nerves containing sensory and motor fibers. All sensory, or centripetal, fibers enter the spinal cord through the posterior roots, on which there are thickenings - nerve nodes. In these nodes are the bodies of centripetal neurons.
The fibers of the motor, or centrifugal, neurons exit the spinal cord through the anterior roots. Each segment of the spinal cord corresponds to a certain part of the body - metamere. However, the innervation of the metameres occurs in such a way that each pair of spinal nerves innervates three adjacent metameres, and each metamere is innervated by three adjacent segments of the spinal cord. Therefore, in order to completely denervate any metamere of the body, it is necessary to cut the nerves of three neighboring segments of the spinal cord.
The autonomic nervous system is the part of the peripheral nervous system that innervates internal organs: heart, stomach, intestines, kidneys, liver, etc. Does not have its own special sensitive ways. Sensitive impulses from organs are transmitted through sensory fibers, which also pass through the peripheral nerves, are common to the somatic and autonomic nervous systems, but make up a smaller part of them.
Unlike the somatic nervous system, autonomic nerve fibers are thinner and conduct excitation much more slowly. On the way from the central nervous system to the innervated organ, they are necessarily interrupted with the formation of a synapse.
Thus, the centrifugal pathway in the autonomic nervous system includes two neurons - preganglionic and postganglionic. The body of the first neuron is located in the central nervous system, and the body of the second is outside it, in the nerve nodes (ganglia). There are many more postganglionic neurons than preganglionic ones. As a result, each preganglionic fiber in the ganglion fits and transmits its excitation to many (10 or more) postganglionic neurons. This phenomenon is called animation.
According to a number of signs, the sympathetic and parasympathetic divisions are distinguished in the autonomic nervous system.
Sympathetic department The autonomic nervous system is formed by two sympathetic chains of nerve nodes (paired border trunk - vertebral ganglia), located on both sides of the spine, and nerve branches that depart from these nodes and go to all organs and tissues as part of mixed nerves. The nuclei of the sympathetic nervous system are located in the lateral horns of the spinal cord, from the 1st thoracic to the 3rd lumbar segments.
The impulses coming through the sympathetic fibers to the organs provide reflex regulation of their activity. In addition to the internal organs, sympathetic fibers innervate blood vessels in them, as well as in the skin and skeletal muscles. They increase and speed up heart contractions, cause a rapid redistribution of blood by constricting some vessels and expanding others.
Parasympathetic department represented by a number of nerves, among which the vagus nerve is the largest. It innervates almost all organs of the chest and abdominal cavity.
The nuclei of the parasympathetic nerves lie in the middle, oblong sections of the brain and sacral spinal cord. Unlike the sympathetic nervous system, all parasympathetic nerves reach the peripheral nerve nodes located in the internal organs or on the outskirts of them. The impulses carried out by these nerves cause weakening and slowing of cardiac activity, narrowing of the coronary vessels of the heart and brain vessels, dilation of the vessels of the salivary and other digestive glands, which stimulates the secretion of these glands, and increases the contraction of the muscles of the stomach and intestines.
The main differences between the sympathetic and parasympathetic divisions of the autonomic nervous system are given in Table. 2. [show] .
Table 2. Autonomic nervous system
| Index | Sympathetic nervous system | parasympathetic nervous system |
| Location of the pregangloonic neuron | Thoracic and lumbar spinal cord | Brain stem and sacral spinal cord |
| Location of switch to postganglionic neuron | Nerve nodes of the sympathetic chain | Nerves in internal organs or near organs |
| Postganglionic neuron mediator | Norepinephrine | Acetylcholine |
| Physiological action | Stimulates the work of the heart, constricts blood vessels, enhances the performance of skeletal muscles and metabolism, inhibits the secretory and motor activity of the digestive tract, relaxes the walls Bladder | It slows down the work of the heart, dilates some blood vessels, enhances the secretion of juice and motor activity of the digestive tract, causes contraction of the walls of the bladder |
Most of the internal organs receive a double autonomic innervation, that is, both sympathetic and parasympathetic nerve fibers approach them, which function in close interaction, having the opposite effect on the organs. It has great importance in the adaptation of the body to constantly changing environmental conditions.
A significant contribution to the study of the autonomic nervous system was made by L. A. Orbeli [show] .
Orbeli Leon Abgarovich (1882-1958) - Soviet physiologist, student of I.P. Pavlov. Acad. Academy of Sciences of the USSR, Academy of Sciences of the ArmSSR and the Academy of Medical Sciences of the USSR. Head of the Military Medical Academy, Institute of Physiology. I, P. Pavlov of the USSR Academy of Sciences, Institute of Evolutionary Physiology, Vice-President of the USSR Academy of Sciences.
The main direction of research is the physiology of the autonomic nervous system.
L. A. Orbeli created and developed the doctrine of the adaptive-trophic function of the sympathetic nervous system. He also carried out research on the coordination of the activity of the spinal cord, on the physiology of the cerebellum, and on higher nervous activity.
| Nervous system | Peripheral nervous system | |||
| somatic (nerve fibers are not interrupted; impulse conduction speed is 30-120 m/s) | vegetative (nerve fibers are interrupted by nodes: the speed of the impulse is 1-3 m / s) | |||
| cranial nerves (12 pairs) | spinal nerves (31 pairs) | sympathetic nerves | parasympathetic nerves | |
| Composition and structure | Depart from various parts of the brain in the form of nerve fibers. Subdivided into centripetal, centrifugal. Innervate the sense organs, internal organs, skeletal muscles |
They depart in symmetrical pairs on both sides of the spinal cord. The processes of centripetal neurons enter through the posterior roots; processes of centrifugal neurons exit through the anterior roots. The processes join to form a nerve |
They depart in symmetrical pairs on both sides of the spinal cord in the thoracic and lumbar regions. The prenodal fiber is short, as the nodes lie along the spinal cord; the post-nodal fiber is long, as it goes from the node to the innervated organ |
Depart from the brain stem and sacral spinal cord. Nerve nodes lie in the walls of or near the innervated organs. The prenodal fiber is long, as it passes from the brain to the organ, the postnodal fiber is short, as it is located in the innervated organ |
| Functions | They provide communication of the body with the external environment, quick reactions to its change, orientation in space, body movements (purposeful), sensitivity, vision, hearing, smell, touch, taste, facial expressions, speech. Activities are controlled by the brain |
Carry out movements of all parts of the body, limbs, determine the sensitivity of the skin. They innervate skeletal muscles, causing voluntary and involuntary movements. Voluntary movements are carried out under the control of the brain, involuntary under the control of the spinal cord (spinal reflexes) |
Innervate internal organs. Post-nodal fibers leave the spinal cord as part of the mixed nerve and pass to the internal organs. Nerves form plexuses - solar, pulmonary, cardiac. Stimulate the work of the heart, sweat glands, metabolism. They hinder the activity of the digestive tract, constrict blood vessels, relax the walls of the bladder, dilate the pupils, etc. |
They innervate the internal organs, exerting an influence on them opposite to the action of the sympathetic nervous system. The largest nerve is the vagus. Its branches are located in many internal organs - the heart, blood vessels, stomach, since the nodes of this nerve are located there. |
| The activity of the autonomic nervous system regulates the work of all internal organs, adapting them to the needs of the whole organism. | ||||
8.1. Reticular formation of the brain stem
In the medulla oblongata and other brain stem regions (pons and midbrain) there is a special cellular structure - the reticular formation. In functional terms, the reticular formation of the trunk is a single structure. The name of this structure reflects early ideas that individual neurons of the reticular formation have extensive connections with each other and form something similar to a neuropil, in which excitation spreads diffusely, similar to how it occurs in the nervous system of coelenterates. However, these ideas were not confirmed later.
Clear boundaries between individual reticular and non-reticular cell groups have not been established, however, up to 98 nuclear groups related to the reticular formation have been identified. The main nuclei are: the nuclei of the suture and the giant cell nucleus of the medulla oblongata, the central and reticular nuclei of the bridge.
The cells of the reticular formation are very diverse in shape and size. They are characterized by the presence of a significantly branched dendritic tree and long axons. The reticular formation receives afferent inputs both along the collaterals of the ascending (sensory) pathways and from overlying structures, including the cerebral cortex and the cerebellum. Thus, the reticular formation integrates the influence of a large number of brain structures. In turn, it itself has an impact on both overlying and underlying structures.
The descending and ascending fibers of the reticular formation leave the nuclei throughout its entire length, without clear spatial distinctions. In addition, there are axons that branch in a T-shape. One of the branches goes down, and the other - to the upper parts of the brain.
Descending fibers form the reticulospinal tract. Through the reticulospinal tract, the reticular formation affects both the motor activity of the spinal cord (implementation of spinal reflexes) and autonomic regulation (vasomotor, respiratory, digestive functions). The reticular formation affects the somatic and vegetative centers in two opposite directions: inhibition and excitation.
The ascending influences of the reticular formation are aimed at regulating the activity of the cerebral cortex. Most reticular fibers reach the cortex through switching in the nonspecific nuclei of the thalamus. The action of ascending reticular influences consists in a wide activation of cortical structures. Inhibition of the activity of the reticular formation leads to the onset of sleep, its activation leads to an awakening reaction.
A characteristic feature of the neurons of the reticular formation is their high sensitivity to chemical factors. Factors such as the level of carbon dioxide and oxygen, the content of adrenaline, acetylcholine and serotonin, relatively small concentrations of pharmacological substances change the activity of neurons of the reticular formation, and with it its effect on the cerebral cortex, somatic and vegetative reflexes.
8.2. autonomic nervous system
The autonomic, or autonomic, nervous system is that part of the unified nervous system that regulates internal systems homeostasis. The autonomic nervous system consists of three sections: sympathetic, parasympathetic and diffuse nervous system of the intestine. All three departments have sensory and motor components. While the former register indicators of the internal environment, the latter enhance or inhibit the activity of those structures that carry out the process of regulation itself.
Receptors involved in homeostasis perceive changes in chemical composition blood or pressure fluctuations in the vascular system and in hollow internal organs such as the digestive tract and bladder. These sensory systems that collect information about the internal environment are very similar to systems that perceive signals from the surface of the body. Their receptor neurons form neural synaptic switches within the brain. Along the motor pathways of the vegetative system, commands go to the organs that directly regulate the internal environment. These pathways start from specialized preganglionic neurons in the spinal cord. This organization is somewhat reminiscent of the organization of the spinal level of the motor system.
The autonomic nervous system is less specialized and more primitive organization. Evolutionary transformations have affected it to a lesser extent than somatic (animal). The influence of the autonomic nervous system is more generated: it performs an adaptive-trophic function in relation to all organs and tissues, while the animal one extends its action only to the skeletal muscles. The neurons of the animal nervous system are more closely packed and compact. There are no (with the exception of the spinal nodes) ganglia brought to the periphery. Feature autonomic nervous system - the presence of peripheral ganglia. The neurons of the animal nervous system are distinguished by a variety of sizes and structures (giant pyramids of Betz and small granule cells in the cerebral cortex, Purkinje cells in the cerebellum, etc.). The neurons of the autonomic ganglia vary in size to a lesser extent, but morphologically they are also heterogeneous. At the end of the 19th - beginning of the 20th century, A.S. Dogel described several types of autonomic neurons in the nerve plexuses of the digestive tract, which are called Type I, II, III Dogel cells. They are multipolar. Note the size and nature of the branching of the dendrites. Type I neurons have the shortest dendrites and often branch within the capsule. Type III neurons have dendrites of medium length, but do not extend beyond the ganglion. Type II neurons have long dendrites ending in receptors in the periphery, such as in smooth muscle. According to A.S. Dogel, confirmed by modern histologists, neurons of type I are efferent, type II are afferent, and type III are intercalary.
The caliber of the fibers of the autonomic nervous system is smaller than that of the animal: 1.0–4.5 µm, compared to 8–18 µm. Functional differences between the two systems are manifested, firstly, in the different speed of nerve impulses: in the fibers of the autonomous system it is less and equal to 0.3 - 10 m/s, in the animal nervous system - from 12 to 100 m/s, and secondly neurons of the autonomic nervous system are less excitable.
The simplest reflex arc in the animal and autonomic nervous system has a three-neuron structure: neuron I (afferent) is located in the spinal ganglion; II neuron (associative) in the animal nervous system belongs to the posterior horn of the spinal cord, its axon goes to the motor neurons of the anterior horns (III neuron); in the autonomic nervous system II, the neuron lies in the lateral horn of the gray matter (intermediolateral nucleus), and its axon goes to the periphery to one of the autonomic ganglia; III neuron (efferent) in the autonomous system is brought to the periphery into the autonomic ganglion. The last two autonomic neurons are called preganglionic and postganglionic, respectively. The axons of the first are surrounded by a myelin sheath, the axon of the second is devoid of it. In the ganglion, a synaptic connection of these neurons is carried out. If the vegetative node is exposed to a 0.2–0.5% nicotine solution, the transmission of excitation in the ganglion will stop. If the spinal node is subjected to the same effect, this will not affect the transmission of impulses. The difference in effect is explained by the fact that nicotine stops the transmission of excitation in the synapse.
According to modern neurohistological and physiological data, the ganglia of the autonomic nervous system have their own sensory neurons in the form of type II Dogel cells and false polar neurons (in the nerve plexuses of the digestive tract and intramural ganglia of internal organs). In addition, autonomic neurons have their own afferent innervation; there is a direct afferent pathway from the peripheral autonomic neuron to the CNS.
The neurons of the autonomic ganglia are distinguished by the morphological variety of synaptic connections formed according to the type of axon-some, axon-dendrite, dendrite-dendrite, axon-axon. The dendrites of several postganglionic neurons (Dogel's type I) intertwine to form baskets on which the pericellular synapses of the preganglionic fibers of the central neurons are located. One preganglionic neuron contacts many postganglionic ones (for example, there are 196 of them in the superior cervical sympathetic ganglion), and several preganglionic synapses form on the postganglionic neuron. This is the anatomical prerequisite for the phenomena of multiplication (generalization of excitation) and convergence. Impulses acquire a certain direction only in the postganglionic neuron.
8.2.1. Sympathetic nervous system
The sympathetic part of the autonomic nervous system has a central and peripheral divisions. The central section is represented by a lateral intermediate substance (substantia intermedia lateralis), which forms the lateral column of the gray matter of the spinal cord, between the VIII cervical and II-III lumbar segments. Cell processes in the form of preganglionic fibers covered with myelin sheaths leave the spinal cord as part of the anterior motor root and dentate ligaments of the spinal cord membranes, forming a white connecting branch (r. communicans albus), which goes to the nodes of the sympathetic trunk.
The peripheral part of the sympathetic part of the nervous system is formed by: 1) numerous nodes located in the form of a paired sympathetic trunk; 2) prevertebral nodes located in the autonomic plexuses of the abdominal cavity; 3) autonomic nerves. The nerves include: a) internodal sympathetic branches (r.r. interganglionares), connecting the nodes of the sympathetic trunk with each other; b) gray connecting branches (r.r. communicantes grisei), consisting of postganglionic fibers devoid of myelin sheath. They are sent from the sympathetic nodes to the spinal nerves and in their composition reach the skin, blood vessels of the muscles and glands of the body; c) sympathetic fibers to the internal organs involved in the formation of extraorganic and intraorganic autonomic plexuses.
sympathetic trunk(truncus sympathicus) - paired, formed by nodes interconnected by sympathetic fibers. The sympathetic trunk is located on the lateral surface of the spine throughout its entire length. Every node(ganglion) of the sympathetic trunk is a cluster of autonomic neurons, with the help of which most of the preganglionic fibers that exit the spinal cord and form white connecting branches switch. preganglionic fibers contact with vegetative cells in the corresponding node or are sent as part of internodal branches to higher or lower nodes of the sympathetic trunk. White connecting branches are located in the thoracic and upper lumbar regions. There are no such connecting branches in the cervical, sacral, and lower lumbar nodes.
The nodes of the sympathetic trunk are also connected by special fibers to the spinal nerves - gray connecting branches(r.r.communicantes grisei), consisting mainly of postganglionic sympathetic fibers. Gray connecting branches depart from each node of the sympathetic trunk to each spinal nerve, in which they are sent to the periphery, reaching the innervated organs - striated muscles, smooth muscles and glands.
8.2.2. parasympathetic nervous system
The nuclei of the parasympathetic part of the autonomic nervous system are located in the brain stem and in the lateral columns of the sacral spinal cord S II-IV.
The nuclei of the brainstem are as follows:
- accessory nucleus of the oculomotor nerve(nucl. accessorius n. oculomotorii) is located on the ventral surface of the cerebral aqueduct in the midbrain. Preganglionic fibers from the brain come out as part of the oculomotor nerve and leave it in the orbit, heading to the ciliary ganglion (gangl. ciliare). The ciliary ganglion is located in the back of the orbit on the outer surface of the optic nerve. Sympathetic sensory nerves pass through the node. After switching of parasympathetic fibers in this node (II neuron), postganglionic fibers leave the node together with sympathetic ones, forming short ciliary nerves. These nerves enter the posterior pole of the eyeball to innervate the muscle that narrows the pupil, and the ciliary muscle that causes accommodation of the eye (parasympathetic nerve), the muscle that dilates the pupil (sympathetic nerve);
- superior salivary nucleus(nucl. salivatorius superior), its fibers leave the core of the bridge along with the motor part of the facial nerve. In one portion, separated in the facial canal of the temporal bone near the opening of the canal of the large stony nerve, after which the nerve receives the same name. Then it passes through the connective tissue of the torn opening of the skull and connects with the deep stony nerve (sympathetic), forming the pterygoid nerve (n. pterygoideus). The pterygoid nerve passes through the canal of the same name into the pterygoid fossa. Its preganglionic parasympathetic fibers switch in the pterygopalatine ganglion. Postganglionic fibers as part of the branches of the maxillary nerve reach the mucous membranes of the nasal cavity, cells of the ethmoid bone, the mucous membrane of the airways, cheeks, lips, oral cavity and nasopharynx, as well as the lacrimal gland, to which they pass along the zygomatic nerve, then through the anastomosis into the lacrimal nerve. The second portion of parasympathetic fibers in the lingual nerve reaches the submandibular salivary gland, after switching in the submandibular and sublingual ganglia. Postganglionic fibers (axons of the II neuron) provide secretory innervation to the sublingual, submandibular salivary glands and mucous glands of the tongue;
- inferior salivary nucleus(nucl. salivatorius inferior) is the core of the IX pair of cranial nerves, located in the medulla oblongata. Its parasympathetic preganglionic fibers leave the nerve in the region of the inferior node of the glossopharyngeal nerve, which lies in a petrous fossa on the inferior surface of the temporal bone pyramid, and enter the tympanic canal of the same name. The tympanic nerve enters the anterior surface of the pyramid of the temporal bone through the opening of the canal, passes to the outer base of the skull, where it switches near the foramen ovale in the parotid node. At the node, preganglionic fibers switch to postganglionic fibers that reach the parotid salivary gland, providing it with secretory innervation;
- dorsal nucleus of the vagus nerve(nucl. dorsalis n. vagi) is located in the dorsal part of the medulla oblongata. It is the most important source of parasympathetic innervation of internal organs. Switching of preganglionic fibers occurs in numerous, but very small intraorganic parasympathetic nodes, in the upper and lower nodes of the vagus nerve, throughout the entire trunk of this nerve, in the autonomic plexuses of internal organs (except for the pelvic organs);
- dorsal intermediate nucleus(nucl. intermedius spinalis) is located in the side columns S II-IV. Its preganglionic fibers exit through the anterior roots into the abdominal branches of the spinal nerves and form the pelvic splanchnic nerves (n.n. splanchnici pelvini), which enter the inferior hypogastric plexus. Their switching to postganglionic fibers occurs in the intraorganic (intramural) nodes of the intraorganic plexuses of the pelvic organs.
8.2.3. Differences between the sympathetic and parasympathetic systems
Relations between the sympathetic and parasympathetic divisions of the autonomic nervous system are considered as competitive, antagonistic. This is related to the distinguishing features morphological and functional plan:
1. The centers of the sympathetic nervous system are more compact. They are located in the lateral horns of the spinal cord in the thoracolumbar region. The centers of the parasympathetic nervous system are more isolated. They are localized in the midbrain (Yakubovich's nucleus), the pons (upper salivary nucleus), in the medulla oblongata (lower salivary and dorsal nuclei of the vagus nerve), and also in the sacral spinal cord.
2. Sympathetic nodes are located closer to the central nervous system (extramural) than parasympathetic, located in the wall of organs (intramural). In this regard, the preganglionic neuron of the sympathetic system has a shorter axon, and the parasympathetic neuron has a longer axon than the postganglionic one. However, on the periphery, sympathetic and parasympathetic neurons often coexist with each other in the intramural ganglia and sympathetic ganglia.
3. Histologically and histochemically, sympathetic and parasympathetic neurons lack clear differences. In their differentiation, a set of features should be taken into account: the length and shape of dendrites, the distribution of organelles and pigments, and the enzyme composition. Thus, a lot of pigment is deposited in sympathetic neurons during aging, while a decrease in enzyme activity prevails in parasympathetic neurons.
4. The parasympathetic department has a smaller zone of innervation than the sympathetic one. The phenomenon of multiplication makes possible, under certain conditions, a generalized effect of the sympathetic department on the organ system as a whole. The nerves of the parasympathetic division have a strictly localized effect on the structure of a particular organ.
5. A specific physiological sign of the sympathetic part of the autonomic nervous system is adrenaline tropism, since it is excited when exposed to adrenaline. The parasympathetic part is excited by exposure to acetylcholine. Ergotoxin is a specific blocker of excitation in sympathetic synapses, and atropine in parasympathetic synapses.
8.2.4. Autonomic innervation of organs
1. Eye:
- parasympathetic preganglionic fibers go from the autonomic nucleus of the midbrain along the nerve of the third pair to the ciliary ganglion; postganglionic - from the cells of the ciliary node to the smooth muscles of the eye; function - constriction of the pupil and accommodation of the eye to far and near vision;
- sympathetic preganglionic fibers from the cells of the lateral sympathetic nuclei of the spinal cord pass through the upper two or three white connecting branches of the thoracic region to the upper cervical ganglion; postganglionic are sent from there through the internal carotid plexus and ciliary nerves to the radial muscle fibers of the iris; function - pupil dilation.
2. Submandibular, sublingual and lacrimal glands:
- parasympathetic preganglionic fibers from the superior salivary nucleus pass in the trunk of the facial nerve, tympanic string and lingual nerve and end in the submandibular node, then go along the trunks of the facial and large superficial stony nerve to the pterygoid node; postganglionic fibers from the submandibular node go to the submandibular and sublingual glands, and from the pterygopalatine node through the zygomatic and maxillary nerves to the lacrimal gland; function - stimulation of secretion of glands;
- sympathetic preganglionic fibers go from the nuclei of the lateral horns of the spinal cord through the upper thoracic white branches and the sympathetic trunk to the upper cervical ganglion, from where through the external and internal carotid plexuses to the submandibular, sublingual and lacrimal glands; functions - some increase in lacrimal secretion and increased secretion of thick viscous saliva.
3. Heart:
- parasympathetic preganglionic fibers from the dorsal motor nucleus of the vagus nerve in the trunk of this nerve and cardiac branches, as well as through the cardiac plexus, approach the internal nodes of the heart; function - inhibition of the heart;
- sympathetic preganglionic fibers from the sympathetic nuclei of the spinal cord through the white branches of the IV-V upper thoracic nerves go to the cervical and upper thoracic nodes, then through the cervical and thoracic cardiac nerves to the heart muscle; function is to stimulate the heart.
4. Lungs and bronchi:
- parasympathetic preganglionic fibers from the dorsal motor nucleus of the vagus nerve along its trunk and pulmonary branches go to the internal nodes of the trachea, bronchi and lungs; postganglionic fibers from the internal nodes to the muscles and glands of the bronchial tree; function - narrowing of the lumen of the bronchi and secretion of mucus;
- sympathetic preganglionic fibers from the lateral sympathetic nuclei through the upper chest white branches go to the stellate ganglion; postganglionic fibers from this node through the pulmonary plexus go to the bronchial muscles and blood vessels; function - expansion of the lumen of the bronchi.
5. Gastrointestinal tract, pancreas, liver:
- parasympathetic preganglionic fibers from the dorsal motor nucleus of the vagus nerve pass along this nerve to the terminal nodes located in the intestinal tube, pancreas and liver; postganglionic fibers go from these nodes to the smooth muscles and glands of these organs; function - an increase in peristalsis of the intestines and gallbladder, an increase in secretion;
- sympathetic preganglionic fibers from the lateral sympathetic nucleus along the white connecting branches from the V to XII thoracic nerve and along the splanchnic nerve go to the celiac and associated nodes, from them postganglionic fibers go to the same organs as the parasympathetic ones; function - slowing down the peristalsis of the intestines and gallbladder, narrowing the lumen of the intestinal blood vessels.
6. Descending colon, rectum, bladder:
- parasympathetic preganglionic fibers go from the centers of the parasympathetic nuclei of the spinal cord as part of the II, III, IV sacral nerves and the pelvic nerve to the terminal nodes of the colon and rectum and bladder; from here postganglionic fibers go to the muscles of the listed organs; function - excitation of peristalsis of the colon and rectum, contraction of the cystic sphincter;
- sympathetic preganglionic fibers from the lateral sympathetic nucleus through the white connecting branches of the lumbar go without interruption through the lumbar node and abdominal aortic plexus to the inferior mesenteric node; postganglionic fibers from this node go to the above organs; function - delay of peristalsis of the colon, excitation of contractions of the anal sphincter and internal sphincter of the bladder.
7. Blood vessels of the skin, sweat glands and pilomotor muscles:
- parasympatheticallye vasomotor fibers leave the spinal cord as part of the dorsal roots and act as vasodilators on skin vessels;
- sympathetic preganglionic fibers go from the lateral sympathetic nucleus along the thoracic and lumbar white connecting branches, along all nodes of the sympathetic trunk; postganglionic fibers from the upper cervical node through the plexus of the external and internal carotid arteries and along the gray connecting branches of the upper cervical nerves to the vessels, sweat glands and muscles of the head and neck; postganglionic fibers from all other trunk nodes along the gray connecting branches and the corresponding spinal nerves to the blood vessels, sweat glands and pilomotors of the trunk and limbs; function - contraction of blood vessels, excitation of the muscles that raise the hair, stimulation of the secretion of sweat glands.
8.2.5. Central regulation
The central nervous system exercises control over the autonomic system to a much lesser extent than over the sensory or skeletal motor system. The areas of the brain that are most associated with autonomic functions are the hypothalamus and the brainstem, especially the medulla oblongata. It is from these structures that the main pathways go to sympathetic and parasympathetic preganglionic autonomic neurons at the spinal level.
It is generally accepted that the hypothalamus is the focus of visceral integrative functions. Signals from the neuronal systems of the hypothalamus directly enter the networks that excite the preganglionic sections of the autonomic nerve pathways. In addition, this region of the brain exercises direct control over the entire endocrine system through sympathetic neurons that regulate the secretion of hormones from the anterior pituitary gland, and the axons of other hypothalamic neurons terminate in the posterior pituitary gland. Here, these endings secrete mediators that circulate in the blood as hormones: 1. vasopressin, which raises blood pressure in an emergency when there is loss of fluid or blood; it also reduces the excretion of water in the urine (which is why vasopressin is called antidiuretic hormone); 2. oxytocin, which stimulates uterine contractions at the final stage of labor.
Although there are several well-defined nuclei among the clusters of hypothalamic neurons, most of the hypothalamus is a collection of zones with blurred boundaries. However, there are quite pronounced nuclei in three zones.
1. Periventricular zone directly adjacent to the third cerebral ventricle, which passes through the center of the hypothalamus. Cells lining the ventricle relay information to neurons in the periventricular zone about important internal parameters that may need to be regulated, such as temperature, salt concentration, and levels of hormones secreted by the thyroid, adrenals, or gonads, as instructed by the pituitary gland.
2. Medial zone contains most of the pathways by which the hypothalamus exercises endocrine control through the pituitary gland. It can be said very approximately that the cells of the periventricular zone control the actual execution of commands given to the pituitary gland by the cells of the medial zone.
3. Through cells lateral zone control over the hypothalamus is carried out by higher instances - the cerebral cortex and the limbic system. It also receives sensory information from the center of the medulla oblongata, which coordinates respiratory and cardiovascular activity. The lateral zone is the place where the higher brain centers make adjustments to the reaction of the hypothalamus to changes in the internal environment. In the cortex, for example, there is a comparison of information coming from two sources - the internal and external environment. If, for example, the cortex judges that the time and circumstances are not suitable for eating, the report of the senses about low blood sugar and an empty stomach will be put aside until a more favorable moment. Ignoring the hypothalamus from the limbic system is less likely. This system can add emotional and motivational coloring to the interpretation of external sensory cues, or compare perceptions of the environment based on these cues with similar situations in the past.
Together with the cortical and limbic components, the hypothalamus also performs many routine integrating actions, and over much longer periods of time than during the implementation of short-term regulatory functions. The hypothalamus “knows” in advance what needs the body has in a normal daily rhythm of life. He, for example, brings the endocrine system into full readiness for action as soon as a person wakes up. It also monitors the hormonal activity of the ovaries throughout menstrual cycle; takes steps to prepare the uterus for the arrival of a fertilized egg. In migratory birds and hibernating mammals, the hypothalamus, with its ability to determine the length of daylight hours, coordinates the body's vital functions during cycles lasting several months.
The hypothalamus makes up less than 5% of the total mass of the brain, but this small amount of tissue contains centers that support all body functions, with the exception of spontaneous respiratory movements, the regulation of blood pressure and heart rhythm. These functions depend on the medulla oblongata. With traumatic brain injuries, the so-called “brain death” occurs when all signs of electrical activity of the cortex disappear and control from the hypothalamus and medulla oblongata is lost, although artificial respiration can still maintain sufficient saturation of the circulating blood with oxygen.
8.2.6. Morphology of the autonomic nervous system
The structure of the autonomic nervous system is characterized by variability in the number, size, shape, and position of the nerve ganglia. The number of nodes in the composition of the boundary shaft is variable. So, for example, the lumbar region may have a dispersion structure, numbering 4 - 5 (up to 7 nodes), or be concentrated when all nodes merge into one. There is also a transitional form with an incomplete concentration of the mass of ganglia, when there are from two to four of them. The frequency of these variants, expressed as a percentage, is not the same in different ethnic groups.
8.2.7. Phylogeny of the autonomic nervous system
In many lower animals, the nervous system is presented as a network, evenly developed in all parts of the body. Separation of the anterior and caudal ends of the body, the formation of body segments led to the concentration of nerve cells in nodes, where the cells have the opportunity to form a large mutual connection.
In connection with the progressive development of the sense organs and other systems in more highly organized animals, such as chordates, the reticular nervous system differentiated into somatic and autonomic. The lancelet already has plexuses with small knots in its internal organs; there are no paravertebral nodes and at the head end of the body.
In cyclostomes, the sympathetic nervous system does not yet form a trunk, but is represented only by a group of scattered cells containing catecholamines. The trunk appears in bony fish and is preserved in higher vertebrates. Interestingly, in lower vertebrates, autonomic preganglionic fibers leave the spinal cord as part of the ventral and dorsal roots. In higher animals, they come out only as part of the ventral roots, but some dorsally exiting fibers remain in amphibians, possibly even in mammals. In fish and amphibians, sympathetic fibers are part of the vagus nerve. A clear division of the autonomic nervous system into sympathetic and parasympathetic is observed only in higher vertebrates. However, in mammals, the vagus nerve also contains noradrenergic (sympathetic) fibers. In the process of evolution, the distribution of peptides in the cells of the sympathetic nervous system changes. In the sympathetic ganglion of the frog, the luteinizing hormone releasing factor contains many terminals of preganglionic fibers and SIF (small intensiv fluorescence) cells (the latter contain enkephalins). In mammals, the sympathetic ganglion does not have this peptide, while enkephalins and substance P are found in preganglionic fibers.
In the gastrointestinal tract, the organization of intramural ganglia becomes more complicated during evolution. For example, the submucosal plexus is absent in more primitive amphibians and reptiles, cyclostomes already have serotonergic neurons but no noradrenergic neurons, while amphibians and reptiles develop noradrenergic neurons.
These phylogenetic data indicate that with the complication of the structure of the organism, a functional and corresponding structural reorganization of the vegetative part of the nervous system is observed, and the higher mechanisms of its regulation become more complicated.
8.2.8. Ontogeny of the autonomic nervous system
In the embryonic period, on the 3rd week, sympathetic trunks begin to form. Neuroblasts (sympathoblasts) migrate from the neural tube and form paired neural folds, from which the thoracic and lumbar sympathetic nodes are formed. At the end of the first month, sympathetic nodes form in the cervical and sacral spine. At the same time, sympathoblasts migrate to the internal organs. First of all, they penetrate the wall of the intestine, and then the heart tube. In front of the aorta, multiple sympathetic nodes are also laid. The parasympathetic nodes of the facial part of the head arise as a result of the migration of neuroblasts from the head end of the neural tube and from the cells of the semilunar ganglion of the trigeminal nerve. The movement of neuroblasts occurs along the nerve trunks.
The vegetative centers of the spinal cord arise as follows: in the third week of embryonic development, sympathoblasts form a lateral column in the lateral sections from the I thoracic to the III lumbar segment of the neural tube. Their axons grow to the periphery along with the axons of the neuroblasts of the motor root. Sympathoblasts also grow into the dentate ligaments. Then they leave the anterior root, forming a white connecting branch for connection with the sympathetic nodes.
The highest level of regulatory mechanisms of autonomic functions are the limbic region, the hippocampal cortex, the orbital gyrus, which are connected by projection pathways to the nuclei of the hypothalamus. Their formation is associated with the development of the brain starting from the second month of intrauterine development. Only by eight months of this period is complete unity established between the higher mechanisms of autonomic regulation and the autonomic nuclei of the spinal cord.
Age-related changes in neurons in the autonomic and animal nervous systems proceed in the same way. However, senile atrophic phenomena are less pronounced in the vegetative system, tk. its neurons, which are phylo- and ontogenetically older, are less susceptible to aging processes.
8.3. limbic system
The limbic system includes cingulate gyrus, turning into hippocampal gyrus, actually hippocampus, dentate fascia, vault And almond nucleus.
Code connects hippocampus With mamillary bodies, which in turn are related mamillo-thalamic tract Vic d, Azira With anterior nucleus of the thalamus. The anterior nuclei of the thalamus project to cingulate gyrus. From here there are connections to the hippocampus. The listed structures and connections form a ring, which was originally described by D. Papets and now bears his name. Among the listed links, studied in detail vault system- main projection path hippocampus. The fibers of the fornix in the region of the septum diverge into compact and diffuse precommissural bundles. The fibers of the latter partially terminate in the nuclei of the septum, partially join medial anterior bundle and in its composition go to preoptic area. compact bundle, or pole vault, traceable to mamillary bodies, giving along the way fibers ending in anterior nucleus, intralaminar and median regions of the thalamus. In addition, a small number of fibers pillar ends at lateral region of the hypothalamus.
The interaction of the centers of the limbic system is also provided by a number of other connections:
1. Broca's diagonal ligament, going from the tonsil to the nuclei of the septum;
2. terminal fibers, heading from the amygdala to the septal nuclei, the preoptic region and the paraventricular-brain bundle connecting the nuclei of the septum with the hypothalamic structures - the preoptic nuclei, the lateral hypothalamic nucleus, as well as the midbrain and mamillary bodies;
3. medullary fibers, emerging from the nuclei of the septum and tonsil and going to the leash, which is connected to the interpeduncular nucleus with the help of the habenulo-peduncular tract. From here, the fibers are sent to the dorsal nucleus of the tegmentum of the midbrain;
4. mamillo-tegmental tract, going from the mammillary bodies to the tegmentum of the midbrain.
In addition to the last two pathways connecting the limbic system with the midbrain, it is also necessary to note the already mentioned medial anterior bundle, which links septal nuclei And lateral hypothalamic region With reticular nuclei of the midbrain tegmentum. The end region of these pathways was called the limbic zone of the midbrain. limbic system, interacting with reticular formation, has a regulatory effect on visceral, somatic, endocrine and higher brain functions. Hypothalamus, and especially his preoptic area, represent the main relay station in the circuit "limbic system - midbrain".
It is believed that due to the existence of numerous links with parietal, visual, temporal, auditory and other areas of the cortex limbic system plays an important role in the synthesis of afferent stimuli. A number of experimental data and clinical observations indicate that the limbic system and, in particular, hippocampus take part in emotional reactions by which an animal or a person shows his positive or negative attitude towards a particular stimulus. In these reactions, the most important role belongs to the reticular formation and the amygdala nuclei, with which the hippocampus has numerous bilateral nerve connections. The joint activity of all these formations ensures the regulation of such complex biological reactions as search, sexual, defensive.
After studying the material of the chapter, the student must:
know
Principles of the structure and functioning of the autonomic nervous system;
be able to
- demonstrate on preparations and tables the sympathetic trunk and cranial vegetative nodes;
- schematically depict the structure of the reflex arc of the autonomic nervous system;
own
Skills for predicting functional disorders in case of damage to the structures of the autonomic nervous system.
The autonomic (autonomous) nervous system provides innervation of internal organs, glands, blood vessels, smooth muscles and performs an adaptive-trophic function. Like the somatic nervous system, it carries out its activities through reflexes. For example, when the receptors of the stomach are stimulated through the vagus nerve, impulses are sent to this organ, which increase the secretion of its glands and activate motility. As a rule, vegetative reflexes are not controlled by consciousness, i.e. occur automatically after certain stimulations. A person cannot voluntarily speed up or decrease the heart rate, increase or inhibit the secretion of glands.
As in the simple somatic reflex arc, the autonomic reflex arc contains three neurons. The body of the first of them (sensitive, or receptor) is located in the spinal node or in the corresponding sensory node of the cranial nerve. The second neuron, an associative cell, lies in the autonomic nuclei of the brain or spinal cord. The third neuron - effector, is located outside the central nervous system in the paravertebral and prevertebral - sympathetic or intramural and cranial - parasympathetic nodes (ganglia). Thus, the arcs of somatic and autonomic reflexes differ from each other by the location of the effector neuron. In the first case, it lies within the central nervous system (motor nuclei of the anterior horns of the spinal cord or motor nuclei of the cranial nerves), and in the second, on the periphery (in the autonomic nodes).
The autonomic nervous system is also characterized by a segmental type of innervation. The centers of autonomic reflexes have a certain localization in the central nervous system, and impulses to the organs pass through the corresponding nerves. Complex autonomic reflexes are performed with the participation of the suprasegmental apparatus. Suprasegmental centers are localized in the hypothalamus, limbic system, reticular formation, cerebellum and in the cortex of the cerebral hemispheres.
Functionally, the sympathetic and parasympathetic divisions of the autonomic nervous system are distinguished.
Sympathetic nervous system
As part of the sympathetic part of the autonomic nervous system, the central and peripheral sections are distinguished. The central nucleus is represented by nuclei located in the lateral horns of the spinal cord, extending from the 8th cervical to the 3rd lumbar segment. All fibers leading to the sympathetic ganglia begin from the neurons of these nuclei. They leave the spinal cord as part of the anterior roots of the spinal nerves.
The peripheral part of the sympathetic nervous system includes nodes and fibers located outside the central nervous system.
sympathetic trunk- a paired chain of paravertebral nodes, running parallel to the spinal column (Fig. 9.1). It extends from the base of the skull to the coccyx, where the right and left trunks converge and end in a single coccygeal node. White connecting branches from the spinal nerves containing preganglionic fibers approach the nodes of the sympathetic trunk. Their length, as a rule, does not exceed 1–1.5 cm. These branches are present only in those nodes that correspond to spinal cord segments containing sympathetic nuclei (8th cervical - 3rd lumbar). The fibers of the white connecting branches switch to the neurons of the corresponding ganglia or pass through them in transit to the higher and lower nodes. In this regard, the number of nodes of the sympathetic trunk (25–26) exceeds the number of white connecting branches. Some fibers do not end in the sympathetic trunk, but, bypassing it, go to the abdominal aortic plexus. They form the greater and lesser celiac nerves. Between neighboring nodes of the sympathetic trunk there are internodal branches, ensuring the exchange of information between its structures. Unmyelinated postganglionic fibers emerge from the ganglia. gray connecting branches, which return to the composition of the spinal nerves, and the bulk of the fibers are sent to the organs along the large arteries.
The large and small splanchnic nerves pass through (without switching) through the 6th–9th and 10th–12th thoracic nodes, respectively. They are involved in the formation of the abdominal aortic plexus.
Accordingly, the cervical (3 nodes), thoracic (10-12), lumbar (5) and sacral (5) sections of the sympathetic trunk are distinguished by segments of the spinal cord. A single coccygeal knot is usually rudimentary.
Upper cervical knot - the biggest. Its branches go mainly along the external and internal carotid arteries, forming plexuses around them. They carry out sympathetic innervation of the organs of the head and neck.
middle neck knot, unstable, lies at the level of the VI cervical vertebra. Gives branches to the heart, thyroid and parathyroid glands, to the vessels of the neck.
Lower cervical knot located at the level of the neck of the 1st rib, often merges with the first thoracic and has a stellate shape. In this case it is called cervicothoracic (star-shaped) node. Gives branches for innervation of the anterior mediastinal organs (including the heart), thyroid and parathyroid glands.
From the thoracic region of the sympathetic trunk depart branches involved in the formation of the thoracic aortic plexus. They provide innervation to the organs of the chest cavity. Moreover, it starts big And small visceral (celiac) nerves, which consist of pretanglion fibers and transit through the 6th–12th nodes. They pass through the diaphragm into the abdominal cavity and end at the neurons of the celiac plexus.
Rice. 9.1.
1 - ciliary node; 2 - pterygopalatine node; 3 - sublingual node; 4 - ear node; 5 - nodes of the celiac plexus; 6 - pelvic splanchnic nerves
The lumbar nodes of the sympathetic trunk are connected to each other not only by longitudinal, but also by transverse internodal branches that connect the ganglia of the right and left sides (see Fig. 8.4). Fibers depart from the lumbar ganglia to form the abdominal aortic plexus. Along the vessels, they provide sympathetic innervation to the walls of the abdominal cavity and lower extremities.
The pelvic section of the sympathetic trunk is represented by five sacral and rudimentary coccygeal nodes. The sacral nodes are also interconnected by transverse branches. The nerves extending from them provide sympathetic innervation to the pelvic organs.
Abdominal aortic plexus located in the abdominal cavity on the anterior and lateral surfaces of the abdominal aorta. This is the largest plexus of the autonomic nervous system. It is formed by several large prevertebral sympathetic nodes, branches of the large and small splanchnic nerves approaching them, numerous nerve trunks and branches extending from the nodes. The main nodes of the abdominal aortic plexus are paired celiac And aortorenal and unpaired superior mesenteric nodes. As a rule, postganglionic sympathetic fibers depart from them. Numerous branches extend from the celiac and superior mesenteric nodes in different directions, like the rays of the sun. This explains the old name for the plexus - "solar plexus".
The branches of the plexus continue on the arteries, forming secondary vegetative plexuses of the abdominal cavity around the vessels (vascular vegetative plexus). These include unpaired: celiac (entangles the celiac trunk), splenic (splenic artery) hepatic (own hepatic artery) top And inferior mesenteric (along the same name arteries) plexus. Paired are gastric, adrenal, renal, testicular (ovarian )plexus, located around the vessels of these organs. Along the course of the vessels, postganglionic sympathetic fibers reach the internal organs and innervate them.
Superior and inferior hypogastric plexuses. The superior hypogastric plexus is formed from branches of the abdominal aortic plexus. In shape, it is a triangular plate located on the anterior surface of the V lumbar vertebra, under the aortic bifurcation. Down the plexus gives the fibers that are involved in the formation of the lower hypogastric plexus. The latter is located above the muscle that lifts the anus, at the site of division of the common iliac artery. Branches depart from these plexuses, providing sympathetic innervation of the pelvic organs.
Thus, the autonomic nodes of the sympathetic nervous system (para- and prevertebral) are located near the spinal cord at a certain distance from the innervated organ. Accordingly, the preganglionic sympathetic fiber has a short length, and the postganglionic fiber is more significant. In the neurotissue synapse, transmission nerve impulse from the nerve to the tissue is carried out due to the release of the neurotransmitter norepinephrine.
parasympathetic nervous system
As part of the parasympathetic part of the autonomic nervous system, the central and peripheral sections are distinguished. The central section is represented by the parasympathetic nuclei III, VII, IX and X of the cranial nerves and the parasympathetic sacral nuclei of the spinal cord. The peripheral section includes parasympathetic fibers and nodes. The latter, in contrast to the sympathetic nervous system, are located either in the wall of the organs they innervate or next to them. Accordingly, preganglionic (myelinated) fibers are longer than postganglionic ones. Impulse transmission in the neurotissue synapse in the parasympathetic nervous system is provided mainly by the mediator acetylcholine.
Parasympathetic fibers ( additional ) kernels 3rd pair of cranial nerves(oculomotor nerve) in the eye socket ends on cells eyelash node. Postganglionic parasympathetic fibers begin from it, which penetrate the eyeball and innervate the muscle that narrows the pupil and the ciliary muscle (provides accommodation). Sympathetic fibers extending from the upper cervical ganglion of the sympathetic trunk innervate the muscle that dilates the pupil.
The pons contains the parasympathetic nuclei ( upper salivary And lacrimal ) VII pair of cranial nerves(facial nerve). Their axons branch off from the facial nerve and are composed of greater stony nerve reach pterygopalatine node, located in the hole of the same name (see Fig. 7.1). Postganglionic fibers begin from it, carrying out parasympathetic innervation of the lacrimal gland, glands of the mucous membranes of the nasal cavity and palate. Part of the fibers, not included in the large stony nerve, is sent to drum string. The latter carries preganglionic fibers to submandibular And sublingual nodes. The axons of the neurons of these nodes innervate the salivary glands of the same name.
Inferior salivary nucleus belongs to the glossopharyngeal nerve IX couple). Its preganglionic fibers pass first in the composition drum, and then - small stony nerve To ear node. Branches depart from it, providing parasympathetic innervation of the parotid salivary gland.
From dorsal nucleus of the vagus nerve (X pair), parasympathetic fibers as part of its branches pass to numerous intramural nodes located in the wall of the internal organs of the neck, [ore and abdominal cavities. Postganglionic fibers depart from these nodes, carrying out parasympathetic innervation of the organs of the neck, chest cavity, and most organs of the abdominal cavity.
sacral division of the parasympathetic nervous system represented by the sacral parasympathetic nuclei located at the level of II-IV sacral segments. They originate fibers pelvic splanchnic nerves, which carry impulses to the intramural nodes of the pelvic organs. Postganglionic fibers extending from them provide parasympathetic innervation of the internal genital organs, bladder and rectum.
Under The term sympathetic nervous system means certain segment (department) autonomic nervous system. Its structure is characterized by some segmentation. This department belongs to the trophic. Its tasks are to supply organs with nutrients, if necessary, increase the rate of oxidative processes, improve breathing, and create conditions for the supply of more oxygen to the muscles. In addition, an important task is to accelerate, if necessary, the work of the heart.
Lecture for doctors "Sympathetic nervous system". The autonomic nervous system is divided into sympathetic and parasympathetic parts. The sympathetic part of the nervous system includes:
- lateral intermediate in the lateral columns of the spinal cord;
- sympathetic nerve fibers and nerves running from the cells of the lateral intermediate substance to the nodes of the sympathetic and autonomic plexuses of the abdominal cavity of the pelvis;
- sympathetic trunk, connecting nerves connecting the spinal nerves with the sympathetic trunk;
- knots of autonomic nerve plexuses;
- nerves from these plexuses to the organs;
- sympathetic fibers.
AUTONOMIC SYSTEM
The autonomic (autonomous) nervous system regulates all internal processes of the body: the functions of internal organs and systems, glands, blood and lymph vessels, smooth and partially striated muscles, sensory organs (Fig. 6.1). It provides homeostasis of the body, i.e. the relative dynamic constancy of the internal environment and the stability of its basic physiological functions (blood circulation, respiration, digestion, thermoregulation, metabolism, excretion, reproduction, etc.). In addition, the autonomic nervous system performs an adaptive-trophic function - the regulation of metabolism in relation to environmental conditions.
The term "autonomic nervous system" reflects the control of the involuntary functions of the body. The autonomic nervous system is dependent on the higher centers of the nervous system. There is a close anatomical and functional relationship between the autonomic and somatic parts of the nervous system. Autonomic nerve conductors pass through the cranial and spinal nerves. The main morphological unit of the autonomic nervous system, as well as the somatic one, is the neuron, and the main functional unit is the reflex arc. In the autonomic nervous system, there are central (cells and fibers located in the brain and spinal cord) and peripheral (all its other formations) sections. There are also sympathetic and parasympathetic parts. Their main difference lies in the features of functional innervation and is determined by the attitude to the means that affect the autonomic nervous system. The sympathetic part is excited by adrenaline, and the parasympathetic part by acetylcholine. Ergotamine has an inhibitory effect on the sympathetic part, and atropine on the parasympathetic part.
6.1. Sympathetic division of the autonomic nervous system
Central formations are located in the cerebral cortex, hypothalamic nuclei, brain stem, in the reticular formation, and also in the spinal cord (in the lateral horns). The cortical representation is not sufficiently elucidated. From the cells of the lateral horns of the spinal cord at the level from C VIII to L V, peripheral formations of the sympathetic division begin. The axons of these cells pass as part of the anterior roots and, having separated from them, form a connecting branch that approaches the nodes of the sympathetic trunk. This is where part of the fibers ends. From the cells of the nodes of the sympathetic trunk, the axons of the second neurons begin, which again approach the spinal nerves and end in the corresponding segments. The fibers that pass through the nodes of the sympathetic trunk, without interruption, approach the intermediate nodes located between the innervated organ and the spinal cord. From the intermediate nodes, the axons of the second neurons begin, heading to the innervated organs.
Rice. 6.1.
1 - cortex of the frontal lobe of the brain; 2 - hypothalamus; 3 - ciliary knot; 4 - pterygopalatine node; 5 - submandibular and sublingual nodes; 6 - ear knot; 7 - upper cervical sympathetic node; 8 - large splanchnic nerve; 9 - internal node; 10 - celiac plexus; 11 - celiac nodes; 12 - small splanchnic nerve; 12a - lower splanchnic nerve; 13 - superior mesenteric plexus; 14 - lower mesenteric plexus; 15 - aortic plexus; 16 - sympathetic fibers to the anterior branches of the lumbar and sacral nerves for the vessels of the legs; 17 - pelvic nerve; 18 - hypogastric plexus; 19 - ciliary muscle; 20 - sphincter of the pupil; 21 - pupil dilator; 22 - lacrimal gland; 23 - glands of the mucous membrane of the nasal cavity; 24 - submandibular gland; 25 - sublingual gland; 26 - parotid gland; 27 - heart; 28 - thyroid gland; 29 - larynx; 30 - muscles of the trachea and bronchi; 31 - lung; 32 - stomach; 33 - liver; 34 - pancreas; 35 - adrenal gland; 36 - spleen; 37 - kidney; 38 - large intestine; 39 - small intestine; 40 - bladder detrusor (muscle that ejects urine); 41 - sphincter of the bladder; 42 - gonads; 43 - genitals; III, XIII, IX, X - cranial nerves
The sympathetic trunk is located along the lateral surface of the spine and has 24 pairs of sympathetic nodes: 3 cervical, 12 thoracic, 5 lumbar, 4 sacral. From the axons of the cells of the upper cervical sympathetic ganglion, the sympathetic plexus of the carotid artery is formed, from the lower - the upper cardiac nerve, which forms the sympathetic plexus in the heart. The aorta, lungs, bronchi, abdominal organs are innervated from the thoracic nodes, and the pelvic organs are innervated from the lumbar nodes.
6.2. Parasympathetic division of the autonomic nervous system
Its formations start from the cerebral cortex, although the cortical representation, as well as the sympathetic part, has not been sufficiently elucidated (mainly it is the limbic-reticular complex). There are mesencephalic and bulbar sections in the brain and sacral - in the spinal cord. The mesencephalic section includes the nuclei of the cranial nerves: the third pair is the accessory nucleus of Yakubovich (paired, small cell), which innervates the muscle that narrows the pupil; Perlia's nucleus (unpaired small cell) innervates the ciliary muscle involved in accommodation. The bulbar section consists of the upper and lower salivary nuclei (VII and IX pairs); X pair - the vegetative nucleus that innervates the heart, bronchi, gastrointestinal tract,
his digestive glands, other internal organs. The sacral section is represented by cells in segments S II -S IV, the axons of which form the pelvic nerve that innervates the urogenital organs and the rectum (Fig. 6.1).
Under the influence of both the sympathetic and parasympathetic divisions of the autonomic nervous system are all organs, with the exception of blood vessels, sweat glands and the adrenal medulla, which have only sympathetic innervation. The parasympathetic department is more ancient. As a result of its activity, stable states of organs and conditions for creating reserves of energy substrates are created. The sympathetic part changes these states (i.e., the functional abilities of organs) in relation to the function being performed. Both parts work in close cooperation. Under certain conditions, the functional predominance of one part over the other is possible. In the case of the predominance of the tone of the parasympathetic part, a state of parasympathotonia develops, the sympathetic part - sympathotonia. Parasympathotonia is characteristic of the state of sleep, sympathotonia is characteristic of affective states (fear, anger, etc.).
In clinical conditions, conditions are possible in which the activity of individual organs or body systems is disrupted as a result of the predominance of the tone of one of the parts of the autonomic nervous system. Parasympathotonic manifestations accompany bronchial asthma, urticaria, angioedema, vasomotor rhinitis, motion sickness; sympathotonic - vasospasm in the form of Raynaud's syndrome, migraine, transient form of hypertension, vascular crises in hypothalamic syndrome, ganglionic lesions, panic attacks. The integration of vegetative and somatic functions is carried out by the cerebral cortex, the hypothalamus and the reticular formation.
6.3. Limbico-reticular complex
All activity of the autonomic nervous system is controlled and regulated by the cortical parts of the nervous system (frontal cortex, parahippocampal and cingulate gyrus). The limbic system is the center of emotion regulation and the neural substrate of long-term memory. The rhythm of sleep and wakefulness is also regulated by the limbic system.
The limbic system (Fig. 6.2) is understood as a number of closely interconnected cortical and subcortical structures that have common development and functions. It also includes the formation of the olfactory pathways located at the base of the brain, the transparent septum, the vaulted gyrus, the cortex of the posterior orbital surface of the frontal lobe, the hippocampus, and the dentate gyrus. The subcortical structures of the limbic system include the caudate nucleus, the putamen, the amygdala, the anterior tubercle of the thalamus, the hypothalamus, and the nucleus of the frenulum. The limbic system includes a complex interweaving of ascending and descending pathways, closely associated with the reticular formation.
Irritation of the limbic system leads to the mobilization of both sympathetic and parasympathetic mechanisms, which has corresponding vegetative manifestations. A pronounced vegetative effect occurs when the anterior parts of the limbic system are irritated, in particular the orbital cortex, amygdala and cingulate gyrus. At the same time, there are changes in salivation, respiratory rate, increased intestinal motility, urination, defecation, etc.
Of particular importance in the functioning of the autonomic nervous system is the hypothalamus, which regulates the functions of the sympathetic and parasympathetic systems. In addition, the hypothalamus implements the interaction of nervous and endocrine, the integration of somatic and autonomic activity. The hypothalamus contains specific and nonspecific nuclei. Specific nuclei produce hormones (vasopressin, oxytocin) and releasing factors that regulate the secretion of hormones from the anterior pituitary gland.
Sympathetic fibers that innervate the face, head and neck originate from cells located in the lateral horns of the spinal cord (C VIII -Th III). Most of the fibers are interrupted in the superior cervical sympathetic ganglion, and a smaller part goes to the external and internal carotid arteries and forms periarterial sympathetic plexuses on them. They are joined by postganglionic fibers coming from the middle and lower cervical sympathetic nodes. In small nodules (cell clusters) located in the periarterial plexuses of the branches of the external carotid artery, fibers terminate that are not interrupted at the nodes of the sympathetic trunk. The remaining fibers are interrupted in the facial ganglia: ciliary, pterygopalatine, sublingual, submandibular and auricular. Postganglionic fibers from these nodes, as well as fibers from cells of the upper and other cervical sympathetic nodes, go to the tissues of the face and head, partly as part of the cranial nerves (Fig. 6.3).
Afferent sympathetic fibers from the head and neck are sent to the periarterial plexuses of the branches of the common carotid artery, pass through the cervical nodes of the sympathetic trunk, partially contacting their cells, and through the connecting branches they approach the spinal nodes, closing the arc of the reflex.
Parasympathetic fibers are formed by axons of the stem parasympathetic nuclei, they are directed mainly to the five autonomic ganglia of the face, in which they are interrupted. A smaller part of the fibers goes to the parasympathetic clusters of cells of the periarterial plexuses, where it is also interrupted, and the postganglionic fibers go as part of the cranial nerves or periarterial plexuses. In the parasympathetic part there are also afferent fibers that go in the vagus nerve system and are sent to the sensory nuclei of the brainstem. The anterior and middle sections of the hypothalamic region through the sympathetic and parasympathetic conductors affect the function of the predominantly ipsilateral salivary glands.
6.5. Autonomic innervation of the eye
sympathetic innervation. Sympathetic neurons are located in the lateral horns of segments C VIII -Th III of the spinal cord. (centrun ciliospinale).
Rice. 6.3.
1 - posterior central nucleus of the oculomotor nerve; 2 - accessory nucleus of the oculomotor nerve (nucleus of Yakubovich-Edinger-Westphal); 3 - oculomotor nerve; 4 - nasociliary branch from the optic nerve; 5 - ciliary knot; 6 - short ciliary nerves; 7 - sphincter of the pupil; 8 - pupil dilator; 9 - ciliary muscle; 10 - internal carotid artery; 11 - carotid plexus; 12 - deep stony nerve; 13 - upper salivary nucleus; 14 - intermediate nerve; 15 - knee assembly; 16 - large stony nerve; 17 - pterygopalatine node; 18 - maxillary nerve (II branch of the trigeminal nerve); 19 - zygomatic nerve; 20 - lacrimal gland; 21 - mucous membranes of the nose and palate; 22 - knee-tympanic nerve; 23 - ear-temporal nerve; 24 - middle meningeal artery; 25 - parotid gland; 26 - ear knot; 27 - small stony nerve; 28 - tympanic plexus; 29 - auditory tube; 30 - single way; 31 - lower salivary nucleus; 32 - drum string; 33 - tympanic nerve; 34 - lingual nerve (from the mandibular nerve - III branch of the trigeminal nerve); 35 - taste fibers to the anterior 2/3 of the tongue; 36 - sublingual gland; 37 - submandibular gland; 38 - submandibular node; 39 - facial artery; 40 - upper cervical sympathetic node; 41 - cells of the lateral horn ThI-ThII; 42 - the lower node of the glossopharyngeal nerve; 43 - sympathetic fibers to the plexuses of the internal carotid and middle meningeal arteries; 44 - innervation of the face and scalp. III, VII, IX - cranial nerves. in green parasympathetic fibers are marked, red - sympathetic, blue - sensitive
The processes of these neurons, forming preganglionic fibers, exit the spinal cord together with the anterior roots, enter the sympathetic trunk as part of the white connecting branches and, without interruption, pass through the overlying nodes, ending at the cells of the superior cervical sympathetic plexus. The postganglionic fibers of this node accompany the internal carotid artery, braiding its wall, penetrate into the cranial cavity, where they connect with the I branch of the trigeminal nerve, penetrate the orbital cavity and end at the muscle that dilates the pupil (m. dilatator pupillae).
Sympathetic fibers also innervate other structures of the eye: tarsal muscles, which expand the palpebral fissure, the orbital muscle of the eye, as well as some structures of the face - sweat glands of the face, smooth muscles of the face and blood vessels.
parasympathetic innervation. The preganglionic parasympathetic neuron lies in the accessory nucleus of the oculomotor nerve. As part of the latter, it leaves the brain stem and reaches the ciliary ganglion (ganglion ciliare), where it switches to postganglionic cells. From there, part of the fibers goes to the muscle that narrows the pupil (m. sphincter pupillae), and the other part is involved in providing accommodation.
Violation of the autonomic innervation of the eye. The defeat of sympathetic formations causes the Bernard-Horner syndrome (Fig. 6.4) with pupil constriction (miosis), narrowing of the palpebral fissure (ptosis), retraction of the eyeball (enophthalmos). It is also possible to develop homolateral anhidrosis, conjunctival hyperemia, depigmentation of the iris.
The development of the Bernard-Horner syndrome is possible with the localization of the lesion at a different level - the involvement of the posterior longitudinal bundle, the paths to the muscle that dilates the pupil. The congenital variant of the syndrome is more often associated with birth trauma with damage to the brachial plexus.
When the sympathetic fibers are irritated, a syndrome occurs that is the opposite of the Bernard-Horner syndrome (Pourfour du Petit) - expansion of the palpebral fissure and pupil (mydriasis), exophthalmos.
6.6. Vegetative innervation of the bladder
The regulation of the activity of the bladder is carried out by the sympathetic and parasympathetic divisions of the autonomic nervous system (Fig. 6.5) and includes retention of urine and emptying of the bladder. Normally, retention mechanisms are more activated, which
Rice. 6.4. Right-sided Bernard-Horner syndrome. Ptosis, miosis, enophthalmos
is carried out as a result of activation of sympathetic innervation and blockade of the parasympathetic signal at the level of segments L I -L II of the spinal cord, while detrusor activity is suppressed and the tone of the muscles of the internal sphincter of the bladder increases.
Regulation of the act of urination occurs when activated
parasympathetic center at the level of S II -S IV and the center of urination in the bridge of the brain (Fig. 6.6). Descending efferent signals send signals that provide relaxation of the external sphincter, suppress sympathetic activity, remove the block of conduction along parasympathetic fibers, and stimulate the parasympathetic center. This results in contraction of the detrusor and relaxation of the sphincters. This mechanism is under the control of the cerebral cortex; the reticular formation, the limbic system, and the frontal lobes of the cerebral hemispheres take part in the regulation.
Arbitrary stop of urination occurs when a command is received from the cerebral cortex to the centers of urination in the brain stem and sacral spinal cord, which leads to a contraction of the external and internal sphincters of the pelvic floor muscles and periurethral striated muscles.
The defeat of the parasympathetic centers of the sacral region, the autonomic nerves emanating from it is accompanied by the development of urinary retention. It can also occur when the spinal cord is damaged (trauma, tumor, etc.) at a level above the sympathetic centers (Th XI -L II). Partial damage to the spinal cord above the level of the location of the autonomic centers can lead to the development of an imperative urge to urinate. When the spinal sympathetic center (Th XI - L II) is affected, true urinary incontinence occurs.
Research methodology. There are numerous clinical and laboratory methods for studying the autonomic nervous system, their choice is determined by the task and conditions of the study. However, in all cases, it is necessary to take into account the initial vegetative tone and the level of fluctuations relative to the background value. The higher the baseline, the lower will be the response in functional tests. In some cases, even a paradoxical reaction is possible. Beam study
Rice. 6.5.
1 - cerebral cortex; 2 - fibers that provide arbitrary control over the emptying of the bladder; 3 - fibers of pain and temperature sensitivity; 4 - cross section of the spinal cord (Th IX -L II for sensory fibers, Th XI -L II for motor); 5 - sympathetic chain (Th XI -L II); 6 - sympathetic chain (Th IX -L II); 7 - cross section of the spinal cord (segments S II -S IV); 8 - sacral (unpaired) node; 9 - genital plexus; 10 - pelvic splanchnic nerves;
11 - hypogastric nerve; 12 - lower hypogastric plexus; 13 - sexual nerve; 14 - external sphincter of the bladder; 15 - bladder detrusor; 16 - internal sphincter of the bladder
Rice. 6.6.
it is better to do it in the morning on an empty stomach or 2 hours after eating, at the same time, at least 3 times. The minimum value of the received data is taken as the initial value.
The main clinical manifestations of the predominance of the sympathetic and parasympathetic systems are presented in Table. 6.1.
To assess the autonomic tone, it is possible to conduct tests with exposure to pharmacological agents or physical factors. As pharmacological agents, solutions of adrenaline, insulin, mezaton, pilocarpine, atropine, histamine, etc. are used.
Cold test. In the supine position, the heart rate is calculated and blood pressure is measured. After that, the brush of the other hand is lowered for 1 min. cold water(4 °C), then the hand is taken out of the water and the blood pressure and pulse are recorded every minute until returning to the initial level. Normally, this happens after 2-3 minutes. With an increase in blood pressure by more than 20 mm Hg. Art. the reaction is considered pronounced sympathetic, less than 10 mm Hg. Art. - moderate sympathetic, and with a decrease in blood pressure - parasympathetic.
Oculocardial reflex (Dagnini-Ashner). When pressing on the eyeballs in healthy people, the heart rate slows down by 6-12 per minute. If the number of heart rate decreases by 12-16 per minute, this is regarded as a sharp increase in the tone of the parasympathetic part. The absence of a decrease or increase in heart rate by 2-4 per minute indicates an increase in the excitability of the sympathetic department.
solar reflex. The patient lies on his back, and the examiner presses his hand on the upper abdomen until a pulsation of the abdominal aorta is felt. After 20-30 seconds, the heart rate slows down in healthy people by 4-12 per minute. Changes in cardiac activity are assessed in the same way as when evoking an oculocardial reflex.
orthoclinostatic reflex. In a patient lying on his back, the heart rate is calculated, and then they are asked to stand up quickly (orthostatic test). When moving from a horizontal to a vertical position, the heart rate increases by 12 per minute with an increase in blood pressure by 20 mm Hg. Art. When the patient moves to a horizontal position, the pulse and blood pressure return to their original values within 3 minutes (clinostatic test). The degree of pulse acceleration during an orthostatic test is an indicator of the excitability of the sympathetic division of the autonomic nervous system. A significant slowing of the pulse during the clinostatic test indicates an increase in the excitability of the parasympathetic department.
Table 6.1.
Adrenaline test. In a healthy person, subcutaneous injection of 1 ml of a 0.1% solution of adrenaline after 10 minutes causes blanching of the skin, increased blood pressure, increased heart rate and increased blood glucose levels. If such changes occur faster and are more pronounced, then the tone of sympathetic innervation is increased.
Skin test with adrenaline. A drop of 0.1% adrenaline solution is applied to the skin injection site with a needle. In a healthy person, blanching with a pink corolla around occurs in such an area.
Atropine test. Subcutaneous injection of 1 ml of a 0.1% solution of atropine in a healthy person causes dry mouth, decreased sweating, increased heart rate and dilated pupils. With an increase in the tone of the parasympathetic part, all reactions to the introduction of atropine are weakened, so the test can be one of the indicators of the state of the parasympathetic part.
To assess the state of the functions of segmental vegetative formations, the following tests can be used.
Dermographism. Mechanical irritation is applied to the skin (with the handle of a hammer, with the blunt end of a pin). The local reaction occurs as an axon reflex. At the site of irritation, a red band appears, the width of which depends on the state of the autonomic nervous system. With an increase in sympathetic tone, the band is white (white dermographism). Wide stripes of red dermographism, a stripe rising above the skin (sublime dermographism), indicate an increase in the tone of the parasympathetic nervous system.
For topical diagnosis, reflex dermographism is used, which is irritated with a sharp object (swiped across the skin with the tip of a needle). There is a strip with uneven scalloped edges. Reflex dermographism is a spinal reflex. It disappears in the corresponding zones of innervation when the posterior roots, segments of the spinal cord, anterior roots and spinal nerves are affected at the level of the lesion, but remains above and below the affected zone.
Pupillary reflexes. Determine the direct and friendly reaction of the pupils to light, the reaction to convergence, accommodation and pain (dilation of the pupils with a prick, pinch and other irritations of any part of the body).
Pilomotor reflex caused by a pinch or by applying a cold object (a test tube with cold water) or a coolant (a cotton wool moistened with ether) to the skin of the shoulder girdle or the back of the head. On the same half of the chest, "goosebumps" appear as a result of contraction of smooth hair muscles. The arc of the reflex closes in the lateral horns of the spinal cord, passes through the anterior roots and the sympathetic trunk.
Test with acetylsalicylic acid. After taking 1 g of acetylsalicylic acid, diffuse sweating appears. With the defeat of the hypothalamic region, its asymmetry is possible. With damage to the lateral horns or anterior roots of the spinal cord, sweating is disturbed in the zone of innervation of the affected segments. With damage to the diameter of the spinal cord, taking acetylsalicylic acid causes sweating only above the site of the lesion.
Trial with pilocarpine. The patient is injected subcutaneously with 1 ml of a 1% solution of pilocarpine hydrochloride. As a result of irritation of the postganglionic fibers going to the sweat glands, sweating increases.
It should be borne in mind that pilocarpine excites peripheral M-cholinergic receptors, which cause increased secretion of the digestive and bronchial glands, constriction of the pupils, an increase in the tone of the smooth muscles of the bronchi, intestines, gall and bladder, uterus, but pilocarpine has the strongest effect on sweating. With damage to the lateral horns of the spinal cord or its anterior roots in the corresponding area of the skin, after taking acetylsalicylic acid, sweating does not occur, and the introduction of pilocarpine causes sweating, since the postganglionic fibers that respond to this drug remain intact.
Light bath. Warming the patient causes sweating. This is a spinal reflex similar to the pilomotor reflex. The defeat of the sympathetic trunk completely eliminates sweating after the use of pilocarpine, acetylsalicylic acid and warming the body.
Skin thermometry. Skin temperature is examined using electrothermometers. Skin temperature reflects the state of skin blood supply, which is an important indicator of autonomic innervation. Areas of hyper-, normo- and hypothermia are determined. The difference in skin temperature of 0.5 °C in symmetrical areas indicates a violation of autonomic innervation.
Electroencephalography is used to study the autonomic nervous system. The method makes it possible to judge the functional state of the synchronizing and desynchronizing systems of the brain during the transition from wakefulness to sleep.
There is a close relationship between the autonomic nervous system and the emotional state of a person, therefore, the psychological status of the subject is studied. To do this, use special sets of psychological tests, the method of experimental psychological testing.
6.7. Clinical manifestations of lesions of the autonomic nervous system
With dysfunction of the autonomic nervous system, various disorders occur. Violations of its regulatory functions are periodic and paroxysmal. Most pathological processes do not lead to the loss of certain functions, but to irritation, i.e. to increased excitability of central and peripheral structures. On the-
disruption in some parts of the autonomic nervous system can spread to others (repercussion). The nature and severity of symptoms are largely determined by the level of damage to the autonomic nervous system.
Damage to the cerebral cortex, especially the limbic-reticular complex, can lead to the development of vegetative, trophic, and emotional disorders. They may be due infectious diseases, injuries of the nervous system, intoxication. Patients become irritable, quick-tempered, quickly exhausted, they have hyperhidrosis, instability of vascular reactions, fluctuations in blood pressure, pulse. Irritation of the limbic system leads to the development of paroxysms of pronounced vegetative-visceral disorders (cardiac, gastrointestinal, etc.). Psychovegetative disorders are observed, including emotional disorders (anxiety, anxiety, depression, asthenia) and generalized autonomic reactions.
With damage to the hypothalamic region (Fig. 6.7) (tumor, inflammatory processes, circulatory disorders, intoxication, trauma), vegetative-trophic disorders may occur: sleep and wakefulness rhythm disturbances, thermoregulation disorder (hyper- and hypothermia), ulceration in the gastric mucosa, lower part of the esophagus, acute perforation of the esophagus, duodenum and stomach, as well as endocrine disorders: diabetes insipidus, adiposogenital obesity, impotence.
Damage to the vegetative formations of the spinal cord with segmental disorders and disorders localized below the level of the pathological process
Patients may have vasomotor disorders (hypotension), sweating disorders and pelvic functions. With segmental disorders in the respective areas, there are trophic changes: increased dryness of the skin, local hypertrichosis or local hair loss, trophic ulcers and osteoarthropathy.
With the defeat of the nodes of the sympathetic trunk, similar clinical manifestations occur, especially pronounced with the involvement of the cervical nodes. There is a violation of sweating and a disorder of pilomotor reactions, hyperemia and an increase in the temperature of the skin of the face and neck; due to a decrease in the tone of the muscles of the larynx, hoarseness of the voice and even complete aphonia may occur; Bernard-Horner syndrome.
Rice. 6.7.
1 - damage to the lateral zone (increased drowsiness, chills, increased pilomotor reflexes, pupillary constriction, hypothermia, low arterial pressure); 2 - damage to the central zone (violation of thermoregulation, hyperthermia); 3 - damage to the supraoptic nucleus (impaired secretion of antidiuretic hormone, diabetes insipidus); 4 - damage to the central nuclei (pulmonary edema and erosion of the stomach); 5 - damage to the paraventricular nucleus (adipsia); 6 - damage to the anteromedial zone (increased appetite and impaired behavioral responses)
The defeat of the peripheral parts of the autonomic nervous system is accompanied by a number of characteristic symptoms. Most often there is a kind of pain syndrome - sympathalgia. The pains are burning, pressing, bursting, tend to gradually spread beyond the area of primary localization. Pain is provoked and aggravated by changes in barometric pressure and ambient temperature. Changes in the color of the skin due to spasm or expansion of peripheral vessels are possible: blanching, redness or cyanosis, changes in sweating and skin temperature.
Autonomic disorders can occur with damage to the cranial nerves (especially the trigeminal), as well as median, sciatic, etc. The defeat of the autonomic ganglia of the face and oral cavity causes burning pain in the area of innervation related to this ganglion, paroxysm, hyperemia, increased sweating, in case lesions of the submandibular and sublingual nodes - an increase in salivation.
