❖ The human nervous system is represented by:
■ the brain and spinal cord (together they form central nervous system
);
■ nerves, ganglions and nerve endings (form peripheral part of the nervous system
).
Functions of the human nervous system:
■ unites all parts of the body into a single whole ( integration );
■ regulates and coordinates the work of various organs and systems ( agreement );
■ carries out the connection of the organism with the external environment, its adaptation to environmental conditions and survival in these conditions ( reflection and adaptation );
■ provides (in interaction with the endocrine system) the constancy of the internal environment of the body at a relatively stable level ( correction );
■ determines the consciousness, thinking and speech of a person, his purposeful behavioral, mental and creative activity (activity ).
❖ Division of the nervous system according to functional characteristics:
■ somatic (innervates the skin and muscles; perceives the effects of the external environment and causes contractions of the skeletal muscles); obeys the will of man;
■ autonomous , or vegetative (regulates metabolic processes, growth and reproduction, the work of the heart and blood vessels, internal organs and endocrine glands).
Spinal cord
Spinal cord located in the spinal canal of the spine, starts from the medulla oblongata (above) and ends at the level of the second lumbar vertebra. It is a white cylindrical cord (cord) with a diameter of about 1 cm and a length of 42-45 cm. The spinal cord has two deep grooves in front and behind, dividing it into the right and left halves.
In the longitudinal direction of the spinal cord, one can distinguish 31 segment , each of which has two front and two back spine formed by axons of neurons; while all segments form a single whole.
Inside spinal cord is located Gray matter having (in section) characteristic shape a flying butterfly whose "wings" form front, rear and (in the thoracic region) lateral horns .
Gray matter consists of bodies of intercalary and motor neurons. Along the axis of gray matter along the spinal cord runs a narrow spinal drip , filled cerebrospinal fluid (see below).
On the periphery spinal cord (around gray matter) white matter .
white matter located in the form of 6 columns around the gray matter (two anterior, lateral and posterior).
It is made up of axons assembled in ascending (located in the back and side columns; transmit excitation to the brain) and descending (located in the anterior and lateral columns; transmit excitation from the brain to the working organs) pathways spinal cord.
The spinal cord is protected by rattling sheaths: solid (from the connective tissue that lines the spinal canal) gossamer (in the form of a thin network; contains nerves and vessels) and soft , or vascular (contains many vessels; grows together with the surface of the brain). The space between the arachnoid and pia mater is filled with cerebrospinal fluid, which provides optimal conditions for the vital activity of nerve cells and protects the spinal cord from shocks and concussions.
IN anterior horns segments of the spinal cord (they are located closer to the abdominal surface of the body) are the body motor neurons , from which their axons depart, forming the anterior motor roots , through which excitation is transmitted from the brain to the working organ (these are the longest human cells, their length can reach 1.3 m).
IN posterior horns segments are bodies intercalary neurons ; rear fit them sensitive roots , formed by the axons of sensory neurons that transmit excitation to the spinal cord. The cell bodies of these neurons are located in spinal nodes (ganglia) located outside the spinal cord along the sensory neurons.
In the thoracic region there are lateral horns Where are the bodies of neurons located? sympathetic parts autonomous nervous system.
Outside the spinal canal, the sensory and motor roots extending from the posterior and anterior horns of one "wing" of the segment unite, forming (together with the nerve fibers of the autonomic nervous system) a mixed spinal nerve , which contains both centripetal (sensory) and centrifugal (motor) fibers (see below).
❖ Spinal Cord Functions carried out under the control of the brain.
■ Reflex function:
pass through the gray matter of the spinal cord arcs of unconditioned reflexes
(they do not affect human consciousness), governing
visceral function, vascular lumen, urination, sexual function, diaphragmatic contraction, defecation, sweating, and managers
skeletal muscles; (examples, knee jerk:
lifting the leg when hitting the tendon attached to kneecap; limb withdrawal reflex: under the action of a painful stimulus, reflex muscle contraction and limb withdrawal occur; urination reflex: filling Bladder causes excitation of stretch receptors in its wall, which leads to relaxation of the sphincter, contraction of the walls of the bladder and urination). 
When the spinal cord is ruptured above the arc of the unconditioned reflex, this reflex does not experience the regulatory action of the brain and is perverted (deviates from the norm, i.e. becomes pathological).
■ Conductor function; pathways of the white matter of the spinal cord are conductors of nerve impulses: ascending pathways nerve impulses from the gray matter of the spinal cord go into the brain (nerve impulses coming from sensitive neurons first enter the gray matter of certain segments of the spinal cord, where they undergo preliminary processing), and descending the paths they go from the brain to different segments of the spinal cord and from there along the spinal nerves to the organs.
In humans, the spinal cord controls only simple motor acts; complex movements (walking, writing, labor skills) are carried out with the obligatory participation of the brain.
Paralysis- loss of the ability to voluntary movements of the body's organs, resulting from damage cervical spinal cord, resulting in a violation of the connection of the brain with the organs of the body located below the site of injury.
spinal shock- this is the disappearance of all reflexes and voluntary movements of the body's organs, the nerve centers of which lie below the site of injury, arising from injuries of the spine and disruption of communication between the brain and the underlying (in relation to the site of injury) sections of the spinal cord.
Nerves. Propagation of a nerve impulse
Nerves- these are strands of nervous tissue that connect the brain and nerve nodes with other organs and tissues of the body through nerve impulses transmitted through them.
Nerves are formed from several bundles nerve fibers (up to 106 fibers in total) and a small number of thin blood vessels enclosed in a common connective tissue sheath. For each nerve fiber, the nerve impulse propagates in isolation, without passing to other fibers.
■ Most nerves mixed ; they include fibers of both sensory and motor neurons.
nerve fiber- a long (may be more than 1 m long) thin process of a nerve cell ( axon), strongly branching at the very end; serves to transmit nerve impulses.
❖ Classification of nerve fibers depending on the structure: myelinated and unmyelinated .
Myelinated nerve fibers are covered with a myelin sheath. myelin sheath performs the functions of protecting, nourishing and isolating nerve fibers. It has a protein-lipid nature and is a plasmalemma Schwann cell (named after its discoverer T. Schwann, 1810-1882), which repeatedly (up to 100 times) wraps around the axon; while the cytoplasm, all organelles and the shell of the Schwann cell are concentrated on the periphery of the shell above the last turn of the plasmalemma. Between adjacent Schwann cells are open sections of the axon - interceptions of Ranvier . A nerve impulse along such a fiber propagates in jumps from one interception to another at a high speed - up to 120 m / s.
Unmyelinated nerve fibers are covered only by a thin insulating and myelin-free sheath. The speed of propagation of a nerve impulse along an unmyelinated nerve fiber is 0.2–2 m/s.
nerve impulse- This is a wave of excitation that propagates along the nerve fiber in response to irritation of the nerve cell.
■ The speed of propagation of a nerve impulse along a fiber is directly proportional to the square root of the fiber's diameter.
Mechanism of nerve impulse propagation. Simplified, a nerve fiber (axon) can be represented as a long cylindrical tube with a surface membrane separating two aqueous solutions of different chemical composition and concentration. The membrane has numerous valves that close when the electric field increases (i.e., with an increase in its potential difference) and open when it is weakened. In the open state, some of these valves pass Na + ions, other valves pass K + ions, but all of them do not pass large ions of organic molecules.
Each axon is a microscopic powerhouse, dividing (through chemical reactions) electric charges. When the axon not excited , inside it there is an excess (compared to the environment surrounding the axon) of potassium cations (K +), as well as negative ions (anions) of a number of organic molecules. Outside the axon there are sodium cations (Na +) and chloride anions (C1 -), which are formed due to the dissociation of NaCl molecules. Anions of organic molecules are concentrated on internal membrane surface, charging it negative , and sodium cations - on its external surface, charging it positively . As a result, an electric field arises between the inner and outer surfaces of the membrane, the potential difference (0.05 V) of which ( resting potential) is large enough to keep the diaphragm valves closed. The resting potential was first described and measured in 1848-1851. German physiologist E.G. Dubois-Reymond in experiments on frog muscles.
When an axon is stimulated, the density of electric charges on its surface decreases, the electric field weakens, and the membrane valves open slightly, allowing the sodium cation Na + into the axon. These cations partially compensate for the negative electric charge the inner surface of the membrane, as a result of which, at the site of irritation, the direction of the field changes to the opposite. The process involves neighboring sections of the membrane, which gives rise to the spread of a nerve impulse. At this moment, the valves open, letting potassium cations K + out, due to which the negative charge inside the axon is gradually restored again, and the potential difference between the inner and outer surfaces of the membrane reaches a value of 0.05 V, characteristic of an unexcited axon. Thus, it is actually not an electric current that propagates along the axon, but a wave of an electrochemical reaction.
■ The shape and speed of propagation of the nerve impulse does not depend on the degree of irritation of the nerve fiber. If it is very strong, there is a whole series of identical impulses; if it is very weak, the impulse does not appear at all. Those. exists some minimum "threshold" degree of stimulation, below which the impulse is not excited.
Impulses entering the neuron along the nerve fiber from any receptor differ only in the number of signals in the series. This means that the neuron only needs to count the number of such signals in one series and, in accordance with the “rules”, how to respond to a given number of consecutive signals, send the necessary command to one or another organ.
spinal nerves
Every spinal nerve formed from two roots , extending from the spinal cord: front (efferent) root and rear (afferent) root, which are connected in the intervertebral foramen, forming mixed nerves (contain motor, sensory and sympathetic nerve fibers).
■ A person has 31 pairs of spinal nerves (according to the number of segments of the spinal cord) extending to the right and left of each segment.
Functions of the spinal nerves:
■ they cause sensitivity of the skin of the upper and lower extremities, chest, abdomen;
■ carry out the transmission of nerve impulses that ensure the movement of all parts of the body and limbs;
■ innervate skeletal muscles (diaphragm, intercostal muscles, muscles of the walls of the chest and abdominal cavity), causing their involuntary movements; at the same time, each segment innervates strictly defined areas of the skin and skeletal muscles.
Voluntary movements are carried out under the control of the cerebral cortex.
❖ Innervation by segments of the spinal cord:
■ segments of the cervical and upper thoracic parts of the spinal cord innervate the organs of the chest cavity, heart, lungs, muscles of the head and upper limbs;
■ the remaining segments of the thoracic and lumbar parts of the spinal cord innervate the organs of the upper and middle parts of the abdominal cavity and the muscles of the body;
■ The lower lumbar and sacral segments of the spinal cord innervate the organs of the lower part of the abdominal cavity and the muscles of the lower extremities.
cerebrospinal fluid
cerebrospinal fluid- a transparent, almost colorless liquid containing 89% water. Changes 5 times a day.
❖ Functions of cerebrospinal fluid:
■ creates a mechanical protective "cushion" for the brain;
■ is the internal environment from which the nerve cells of the brain receive nutrients;
■ participates in the removal of exchange products;
■ participates in the maintenance of intracranial pressure.
Brain. General characteristics of the structure
Brain located in the cranial cavity and covered with three meninges, equipped with vessels; its mass in an adult is 1100-1700 g.
❖Structure: the brain is made up of 5 departments:
■ medulla oblongata,
■ hindbrain,
■ midbrain,
■ diencephalon,
■ forebrain. 
brain stem - it is a system formed by the medulla oblongata, hindbrain pons, midbrain and diencephalon
In some textbooks and manuals, not only the pons of the hindbrain, but the entire hindbrain, including both the pons varolii and the cerebellum, are referred to the trunk of the brain bridge.
In the brainstem are the nuclei of the cranial nerves that connect the brain with the sense organs, muscles and some glands; gray the substance in it is inside in the form of nuclei, white - outside . White matter consists of processes of neurons that connect parts of the brain to each other.
Bark the cerebral hemispheres and the cerebellum is formed by gray matter, consisting of the bodies of neurons.
Inside the brain are communicating cavities ( cerebral ventricles ), which are a continuation of the central canal of the spinal cord and filled cerebrospinal fluid: I and II lateral ventricles - in the hemispheres of the forebrain, III - in the diencephalon, IV - in the medulla oblongata.
The channel connecting the IV and III ventricles and passing through midbrain, is called aqueduct of the brain.
12 pairs depart from the nuclei of the brain cranial nerves , innervating the sense organs, tissues of the head, neck, organs of the chest and abdominal cavities.
The brain (like the spinal cord) is covered with three shells: solid (from dense connective tissue; performs a protective function), gossamer (contains nerves and vessels) and vascular (contains many vessels). The space between the arachnoid and choroid is filled cerebral fluid .
The existence, location and function of the various centers of the brain are determined by stimulation various structures of the brain electric shock .
Medulla
Medulla is a direct continuation of the spinal cord (after it passes through the foramen magnum) and has a structure similar to it; at the top it borders on the bridge; it contains the fourth ventricle. White matter is located mainly on the outside and forms 2 protrusions - pyramids , the gray matter is located inside the white matter, forming in it numerous nuclei .
■ The nuclei of the medulla oblongata control many vital functions; that's why they are called centers .
❖ Functions of the medulla oblongata:
■ conductive: sensory and motor pathways pass through it, along which impulses are transmitted from the spinal cord to the overlying parts of the brain and back;
■ reflex(carried out together with the pons varolii): in centers the medulla oblongata closes the arcs of many important unconditioned reflexes: respiration and circulation , as well as sucking, salivation, swallowing, gastric secretion (responsible for digestive reflexes ), coughing, sneezing, vomiting, blinking (responsible for defensive reflexes ), etc. Damage to the medulla oblongata leads to cardiac and respiratory arrest and instant death.
Hind brain
Hind brain consists of two departments - pons and cerebellum .
Bridge (Varolian bridge) located between the medulla oblongata and midbrain; Nerve pathways pass through it, connecting the forebrain and midbrain with the medulla oblongata and spinal cord. The facial and auditory cranial nerves depart from the bridge.
❖ Functions of the hindbrain: together with the medulla oblongata, the bridge performs conductive And reflex functions as well governs digestion, respiration, cardiac activity, movement of the eyeballs, contraction of facial muscles that provide facial expressions, etc.
Cerebellum located above the medulla oblongata and consists of two small lateral hemispheres , the middle (most ancient, stem) part, connecting the hemispheres and called cerebellar worm , and three pairs of legs connecting the cerebellum with the midbrain, pons varolii and medulla oblongata.
The cerebellum is covered bark from the gray matter, under which is the white matter; the vermis and cerebellar peduncles also consist of white matter. Within the white matter of the cerebellum are nuclei made up of gray matter. The cerebellar cortex has numerous elevations (gyrus) and depressions (sulci). Most cortical neurons are inhibitory.
❖ Functions of the cerebellum:
■ the cerebellum receives information from the muscles, tendons, joints and motor centers of the brain;
■ it ensures the maintenance of muscle tone and body posture,
■ coordinates body movements (makes them precise and coordinated);
■ manages balance.
With the destruction of the cerebellar vermis, a person cannot walk and stand, with damage to the hemispheres of the cerebellum, speech and writing are disturbed, severe trembling of the limbs appears, movements of the arms and legs become sharp.
Reticular Formation
Reticular (mesh) formation- This is a dense network formed by a cluster of neurons of different sizes and shapes, with well-developed processes that run in different directions and many synaptic contacts.
■ The reticular formation is located in the middle part of the medulla oblongata, in the pons and midbrain.
❖ Functions of the reticular formation:
■ its neurons sort (pass, delay or supply additional energy) incoming nerve impulses;
■ it regulates the excitability of all parts of the nervous system located above it ( ascending influences ) and below ( downward influences ), and is a center that stimulates the centers of the cerebral cortex;
■ the state of wakefulness and sleep is associated with its activity;
■ it ensures the formation of sustainable attention, emotions, thinking and consciousness;
■ with its participation, the regulation of digestion, respiration, heart activity, etc. is carried out.
midbrain
midbrain- the smallest part of the brain located above the bridge between the diencephalon and the cerebellum. Introduced quadrigemina (2 upper and 2 lower tubercles) and legs of the brain . There is a canal in its center water pipes ), connecting the III and IV ventricles and filled with cerebrospinal fluid.
❖ Midbrain functions:
■conductive: in its legs there are ascending nerve pathways to the cerebral cortex and cerebellum and descending nerve pathways along which impulses go from the cerebral hemispheres and cerebellum to the medulla oblongata and spinal cord;
■ reflex: associated with it are reflexes of body posture, its rectilinear motion, rotation, ascent, descent and landing, arising with the participation of the sensory system of balance and providing coordination of movement in space;
■ in the quadrigemina there are subcortical centers of visual and auditory reflexes that provide orientation towards sound and light. The neurons of the superior colliculus of the quadrigemina receive impulses from the eyes and muscles of the head and respond to objects moving rapidly in the field of view; neurons of the inferior colliculus respond to strong, sharp sounds, putting the auditory system on high alert;
■ it regulates muscle tone , provides fine finger movements, chewing.
diencephalon
❖ diencephalon- this is the final section of the brain stem; it is located under large hemispheres forebrain over midbrain. It contains centers that process nerve impulses entering the cerebral hemispheres, as well as centers that control the activity of internal organs.
The structure of the diencephalon: it consists of the central part - thalamus (visual tubercles), hypothalamus (subtuberous area) and cranked bodies ; it also contains the third ventricle of the brain. Located at the base of the hypothalamus pituitary.
■ thalamus- this is a kind of "control room", through which all information about external environment and state of the body. The thalamus controls the rhythmic activity of the cerebral hemispheres, is the subcortical center for analysis of all types sensations , except for olfactory; it houses the centers that regulate sleep and wakefulness, emotional reactions(feelings of aggression, pleasure and fear) and mental activity person. IN ventral nuclei thalamus is formed sensation pain and maybe feeling time .
If the thalamus is damaged, the nature of sensations can change: for example, even slight touches on the skin, sound or light can cause severe attacks of pain in a person; on the contrary, sensitivity may decrease so much that a person will not respond to any irritation.
■ Hypothalamus- the highest center of vegetative regulation. He perceives changes in the internal environment organism and regulates metabolism, body temperature, blood pressure, homeostasis, the work of endocrine glands. It has centers hunger, satiety, thirst, regulation body temperature etc. It releases biologically active substances ( neurohormones ) and substances necessary for the synthesis of neurohormones pituitary gland , carrying out neurohumoral regulation the vital activity of the organism. The anterior nuclei of the hypothalamus are the center of parasympathetic autonomic regulation, the posterior nuclei are sympathetic.
■ Pituitary- lower appendage of the hypothalamus; is an endocrine gland (for details, see "").
Forebrain. The cerebral cortex
❖ forebrain represented by two large hemispheres And corpus callosum connecting the hemispheres. The large hemispheres control the work of all organ systems and provide the relationship of the body with the external environment. The corpus callosum plays an important role in the processing of information in the learning process.
big hemispheres two - solder and left ; they cover the midbrain and diencephalon. In an adult, the cerebral hemispheres account for up to 80% of the mass of the brain.
On the surface of each hemisphere there are many furrows (recesses) and convolutions (folds).
Main furrows; central, lateral and parietal-occipital. Furrows divide each hemisphere into 4 shares (see below); which, in turn, are divided by furrows into a series convolutions .
Inside the cerebral hemispheres are the 1st and 2nd ventricles of the brain.
The major hemispheres are covered gray matter - bark , consisting of several layers of neurons that differ from each other in shape, size and function. In total, there are 12-18 billion bodies of neurons in the cerebral cortex. The thickness of the bark is 1.5-4.5 mm, the area is 1.7-2.5 thousand cm2. Furrows and convolutions significantly increase the surface area and volume of the cortex (2/3 of the cortical area is hidden in the furrows).
The right and left hemispheres are functionally different from each other ( functional asymmetry of the hemispheres ). The presence of functional asymmetry of the hemispheres was established in experiments on people with a "split brain".
■ Operation " brain splitting a" consists in the surgical cutting (for medical reasons) of all direct connections between the hemispheres, as a result of which they begin to function independently of each other.
At right-handers the leading (dominant) hemisphere is left , and at left-handed - right .
■ Right hemisphere responsible for creative thinking , forms the basis creativity , acceptance non-standard solutions . Damage to the visual zone of the right hemisphere leads to impaired face recognition.
■ Left hemisphere provides logical reasoning And abstract thinking (the ability to operate with mathematical formulas, etc.), it contains centers oral and written speeches , formation decisions . Damage to the visual zone of the left hemisphere leads to impaired recognition of letters and numbers.
Despite its functional asymmetry, the brain functions as whole , providing consciousness, memory, thinking, adequate behavior, various types of conscious human activity.
❖ Functions of the cortex cerebral hemispheres:
■ carries out higher nervous activity (consciousness, thinking, speech, memory, imagination, the ability to write, read, count);
■ provides the relationship of the body with the external environment, is the central department of all analyzers; various sensations are formed in its zones (the zones of hearing and taste are located in the temporal lobe; vision - in the occipital; speech - in the parietal and temporal; skin-muscle sense - in the parietal; movement - in the frontal);
■ provides mental activity;
■ arcs of conditioned reflexes are closed in it (ie it is an organ for acquiring and accumulating life experience).
❖Lobes of the bark- subdivision of the surface of the cortex according to the anatomical principle: in each hemisphere, the frontal, temporal, parietal and occipital lobes are distinguished. 
❖ Cortex zone- a section of the cerebral cortex, characterized by the uniformity of the structure and functions performed.
❖ Types of cortical zones: sensory (or projection), associative, motor.
Sensory or projection zones are the higher centers various kinds sensitivity; when they are irritated, the simplest sensations arise, and when damaged, a violation of sensory functions occurs (blindness, deafness, etc.). These zones are located in the areas of the cortex, where the ascending pathways end, along which nerve impulses from the receptors of the sense organs (visual zone, auditory zone, etc.) are conducted.
■ visual area located in the occipital region of the cortex;
■olfactory, gustatory and auditory areas - in the temporal region and next to it;
■ skin and muscle sensation zones - in the posterior central gyrus.
Association zones- areas of the cortex responsible for generalized information processing; processes that ensure the mental functions of a person take place in them - thinking, speech, emotions, etc.
In associative zones, excitation occurs when impulses arrive not only in these, but also in sensory zones, and not only from one, but also simultaneously from several sense organs (for example, excitation in the visual zone can appear in response not only to visual, but also to auditory stimuli).
■ Frontal associative areas of the cortex provide the production of sensory information and form the goal and program of action, consisting of commands sent to executive bodies. From these organs, the frontal associative zones receive feedback about the implementation of actions and their direct consequences. In the frontal associative zones, this information is analyzed, it is determined whether the goal has been achieved, and if it is not achieved, the commands to the organs are corrected.
■ The development of the frontal lobes of the cortex largely determined high level mental abilities of humans compared to primates.
Motor (motor) zones- areas of the cortex, irritation of which causes muscle contraction. These zones control voluntary movements; they originate descending conducting paths along which nerve impulses go to the intercalary and executive neurons.
■ The motor function of various parts of the body is represented in the anterior central gyrus. The largest space is occupied by the motor zones of the hands, fingers and muscles of the face, the smallest - by the zones of the muscles of the body.
Electroencephalogram
Electroencephalogram (EEG)- this is a graphical record of the total electrical activity of the cerebral cortex - nerve impulses generated by a combination of its (cortex) neurons.
■ In the human EEG, waves of electrical activity of different frequencies are observed - from 0.5 to 30 oscillations per second.
Basic rhythms of electrical activity cerebral cortex: alpha rhythm, beta rhythm, delta rhythm and theta rhythm.
alpha rhythm- oscillations with a frequency of 8-13 hertz; this rhythm prevails over others during sleep.
beta rhythm has an oscillation frequency of more than 13 hertz; it is characteristic of active wakefulness.
Theta rhythm- oscillations with a frequency of 4-8 hertz.
delta rhythm has a frequency of 0.5-3.5 hertz.
■ Theta and delta rhythms are observed during very deep sleep or anesthesia .
cranial nerves
cranial nerves a person has 12 pairs; they depart from different parts of the brain and are divided by function into sensory, motor and mixed.
❖ Sensitive nerves-1, II, VIII couples:
■ I couple — olfactory nerves that depart from the forebrain and innervate the olfactory region of the nasal cavity;
■ And couple — visual nerves that depart from the diencephalon and innervate the retina of the eye;
■ VIII pair - auditory (or vestibulocochlear e) nerves; depart from the bridge, innervate the membranous labyrinth and the Cor-ti's organ of the inner ear.
❖ Motor nerves- III, IV, VI, X, XII pairs:
■ III pair — oculomotor nerves arising from the midbrain;
■ IV pair - blocky nerves also arise from the midbrain;
■ VI - diverting nerves that depart from the bridge (III, IV and VI pairs of nerves innervate the muscles of the eyeball and eyelids);
■ XI - additional nerves, depart from the medulla oblongata;
■XII— sublingual nerves also depart from the medulla oblongata (XI and XII pairs of nerves innervate the muscles of the pharynx, tongue, middle ear, parotid salivary gland).
❖ mixed nerves-V, VII, IX, X pairs:
■ V pair — trigeminal nerves that depart from the bridge, innervate the scalp, eye membranes, masticatory muscles, etc .;
■ VII pair - facial nerves also depart from the bridge, innervate the facial muscles, the lacrimal gland, etc .;
■ IX couple — glossopharyngeal nerves that depart from the diencephalon, innervate the muscles of the pharynx, middle ear, parotid salivary gland;
■ X pair — wandering nerves also depart from the diencephalon, innervate the muscles of the soft palate and larynx, the organs of the chest (trachea, bronchi, heart, slowing down its work) and abdominal cavities (stomach, liver, pancreas).
Features of the autonomic nervous system
Unlike the somatic nervous system, whose nerve fibers are thick, covered with a myelin sheath and are characterized by a high speed of propagation of nerve impulses, autonomic nerve fibers are usually thin, do not have a myelin sheath and are characterized by a low speed of propagation of nerve impulses (see table). 
❖ Functions of the autonomic nervous system:
■ maintaining the constancy of the internal environment of the body through the neuroregulation of tissue metabolism ("start", correction or suspension of certain metabolic processes) and the work of internal organs, the heart and blood vessels;
■ adaptation of the activities of these organs to the changed environmental conditions and the needs of the body.
The autonomic nervous system is made up of sympathetic And parasympathetic parts , which have the opposite effect on the physiological functions of organs.
sympathetic part The autonomic nervous system creates conditions for intensive activity of the body, especially in extreme conditions, when it is necessary to demonstrate all the capabilities of the body.
parasympathetic part(the "retreat" system) of the autonomic nervous system reduces the level of activity, which contributes to the restoration of resources spent by the body.
■ Both parts (sections) of the autonomic nervous system are subordinate to higher nerve centers located in hypothalamus , and complement each other.
■ The hypothalamus coordinates the work of the autonomic nervous system with the activity of the endocrine and somatic systems.
■ Examples of the influence of the sympathetic and parasympathetic parts of the ANS on the organs are given in the table on p. 520.
The effective performance of the functions of both parts of the autonomic nervous system is ensured double innervation internal organs and heart.
double innervation internal organs and the heart means that nerve fibers from both the sympathetic and parasympathetic parts of the autonomic nervous system approach each of these organs. 
Neurons of the autonomic nervous system synthesize various mediators (acetylcholine, norepinephrine, serotonin, etc.) involved in the transmission of nerve impulses.
main feature autonomic nervous system - bineuronality of the efferent pathway
. This means that in the autonomic nervous system efferent
, or centrifugal
(i.e. coming from the head and spinal brain to organs
), nerve impulses sequentially pass through the bodies of two neurons. The two-neuronality of the efferent pathway makes it possible to distinguish in the sympathetic and parasympathetic parts of the autonomic nervous system central and peripheral parts
.
central part (nerve centers ) autonomic nervous system located in the central nervous system (in the lateral horns of the gray matter of the spinal cord, as well as in the medulla oblongata and midbrain) and contains the first motor neurons of the reflex arc . The autonomic nerve fibers going from these centers to the working organs switch in the autonomic ganglia of the peripheral part of the autonomic nervous system.
peripheral part The autonomic nervous system is located outside the central nervous system and consists of ganglion (nerve ganglions) formed by the bodies second motor neurons of the reflex arc as well as nerves and nerve plexuses.
■ At sympathetic department, these ganglia form a pair sympathetic chains (trunks) located near the spine on both sides of it, in the parasympathetic department they lie near or inside the innervated organs.
■ Postganglionic parasympathetic fibers approach the eye muscles, larynx, trachea, lungs, heart, lacrimal and salivary glands, muscles and glands of the digestive tract, excretory and genital organs. 
Causes of disruption of the nervous system
❖ Overwork of the nervous system weakens its regulatory function and can provoke the occurrence of a number of mental, cardiovascular, gastrointestinal, skin and other diseases.
❖ hereditary diseases can lead to changes in the activity of some enzymes. As a result, toxic substances accumulate in the body, the impact of which leads to impaired brain development and mental retardation.
Negative environmental factors:
■bacterial infections lead to the accumulation of toxins in the blood, poisoning the nervous tissue (meningitis, tetanus);
■ viral infections can affect the spinal cord (poliomyelitis) or the brain (encephalitis, rabies);
■ alcohol and its metabolic products excite various nerve cells (inhibitory or excitatory neurons), disorganizing the work of the nervous system; the systematic use of alcohol causes chronic depression of the nervous system, changes in skin sensitivity, muscle pain, weakening and even disappearance of many reflexes; irreversible changes occur in the central nervous system, forming personality changes and leading to the development of severe mental illness and dementia;
■ influence nicotine and drugs much like the effect of alcohol;
■salt heavy metals bind to enzymes, disrupting their work, which leads to disruption of the nervous system;
■ when bites of poisonous animals biologically active substances (poisons) that disrupt the functioning of neuronal membranes enter the bloodstream;
■ when head injuries, bleeding and severe pain possible loss of consciousness, which is preceded by: blackout, tinnitus, pallor, temperature drop, profuse sweat, weak pulse, shallow breathing.
Violation of cerebral circulation. To disruption of the normal functioning of the brain and, as a result, to diseases various bodies leads to narrowing of the lumen of cerebral vessels. Injuries and high blood pressure can cause rupture of cerebral vessels, which usually leads to paralysis, disorders of the higher nervous activity or death.
Clamping of the nerve trunks of the brain causes severe pain. Infringement of the roots of the spinal cord by spasmodic back muscles or as a result of inflammation causes paroxysmal pain (typical for sciatica ), sensory disturbance ( numbness ) and etc.
❖ When metabolic disorders in the brain mental illness occurs
■neurosis - emotional, motor and behavioral disorders, accompanied by deviations from the autonomic nervous system and the work of internal organs (example: fear of the dark in children);
■ affective insanity - a more serious illness in which periods of extreme excitement alternate with apathy (paranoia, megalomania or persecution);
■ schizophrenia - splitting of consciousness;
■ hallucinations (may also occur with poisoning, high fever, acute alcoholic psychosis).
Nerve endings are located throughout human body. They carry the most important function and are an integral part of the entire system. The structure of the human nervous system is a complex branched structure that runs through the entire body.
The physiology of the nervous system is a complex composite structure.
The neuron is considered the basic structural and functional unit of the nervous system. Its processes form fibers that are excited when exposed and transmit an impulse. The impulses reach the centers where they are analyzed. After analyzing the received signal, the brain transmits the necessary reaction to the stimulus to the appropriate organs or parts of the body. The human nervous system is briefly described by the following functions:
- providing reflexes;
- regulation of internal organs;
- ensuring the interaction of the organism with the external environment, by adapting the body to changing external conditions and stimuli;
- interaction of all organs.
The value of the nervous system is to ensure the vital activity of all parts of the body, as well as the interaction of a person with the outside world. The structure and functions of the nervous system are studied by neurology.
Structure of the CNS
Anatomy of the central nervous system (CNS) is a collection of neuronal cells and neuronal processes of the spinal cord and brain. A neuron is a unit of the nervous system.
The function of the CNS is to provide reflex activity and processing of impulses coming from the PNS.
The anatomy of the central nervous system, the main node of which is the brain, is a complex structure of branched fibers.
The higher nerve centers are concentrated in the cerebral hemispheres. This is the consciousness of a person, his personality, his intellectual abilities and speech. The main function of the cerebellum is to ensure coordination of movements. The brain stem is inextricably linked to the hemispheres and the cerebellum. This section contains the main nodes of the motor and sensory pathways, which ensures such vital body functions as the regulation of blood circulation and breathing. The spinal cord is the distribution structure of the CNS, it provides branching of the fibers that form the PNS.
The spinal ganglion (ganglion) is the site of concentration of sensitive cells. With the help of the spinal ganglion, the activity of the autonomic division of the peripheral nervous system is carried out. Ganglia or nerve nodes in the human nervous system are classified as PNS, they perform the function of analyzers. The ganglia do not belong to the human central nervous system.
Structural features of the PNS
Thanks to the PNS, the activity of the entire human body is regulated. The PNS is made up of cranial and spinal neurons and fibers that form ganglia.
The structure and functions of the human peripheral nervous system are very complex, so any slightest damage, for example, damage to the vessels in the legs, can cause serious disruption of its work. Thanks to the PNS, control is exercised over all parts of the body and the vital activity of all organs is ensured. The importance of this nervous system for the body cannot be overestimated.
The PNS is divided into two divisions - the somatic and autonomic systems of the PNS.
The somatic nervous system performs a double job - collecting information from the sense organs, and further transferring this data to the central nervous system, as well as ensuring the motor activity of the body, by transmitting impulses from the central nervous system to the muscles. Thus, it is the somatic nervous system that is the instrument of human interaction with the outside world, since it processes the signals received from the organs of vision, hearing and taste buds.
The autonomic nervous system ensures the performance of the functions of all organs. It controls the heartbeat, blood supply, and respiratory activity. It contains only motor nerves that regulate muscle contraction.
To ensure the heartbeat and blood supply, the efforts of the person himself are not required - it is the vegetative part of the PNS that controls this. The principles of the structure and function of the PNS are studied in neurology.
Departments of the PNS
The PNS also consists of an afferent nervous system and an efferent division.
The afferent section is a collection of sensory fibers that process information from receptors and transmit it to the brain. The work of this department begins when the receptor is irritated due to any impact.
The efferent system differs in that it processes impulses transmitted from the brain to effectors, that is, muscles and glands.
One of the important parts of the autonomic division of the PNS is the enteric nervous system. The enteric nervous system is formed from fibers located in the gastrointestinal tract and urinary tract. The enteric nervous system controls the motility of the small and large intestines. This department also regulates the secretion secreted in the gastrointestinal tract and provides local blood supply.
The value of the nervous system is to ensure the work of internal organs, intellectual function, motor skills, sensitivity and reflex activity. The child's CNS develops not only during intrauterine period but also during the first year of life. The ontogenesis of the nervous system begins from the first week after conception.
The basis for the development of the brain is formed already in the third week after conception. The main functional nodes are indicated by the third month of pregnancy. By this time, the hemispheres, trunk and spinal cord have already been formed. By the sixth month, the higher parts of the brain are already better developed than the spinal region.
By the time the baby is born, the brain is the most developed. The size of the brain in a newborn is approximately one eighth of the weight of the child and fluctuates within 400 g.
The activity of the central nervous system and PNS is greatly reduced in the first few days after birth. This may be in the abundance of new irritating factors for the baby. This is how the plasticity of the nervous system is manifested, that is, the ability of this structure to rebuild. As a rule, the increase in excitability occurs gradually, starting from the first seven days of life. The plasticity of the nervous system deteriorates with age.
CNS types
In the centers located in the cerebral cortex, two processes simultaneously interact - inhibition and excitation. The rate at which these states change determines the types of the nervous system. While one section of the CNS center is excited, the other is slowed down. This is the reason for the peculiarities of intellectual activity, such as attention, memory, concentration.
Types of the nervous system describe the differences between the speed of the processes of inhibition and excitation of the central nervous system in different people.
People may differ in character and temperament, depending on the characteristics of the processes in the central nervous system. Its features include the speed of switching neurons from the process of inhibition to the process of excitation, and vice versa.
Types of the nervous system are divided into four types.
- The weak type, or melancholic, is considered the most prone to the occurrence of neurological and psycho-emotional disorders. It is characterized by slow processes of excitation and inhibition. A strong and unbalanced type is a choleric. This type is distinguished by the predominance of excitatory processes over inhibition processes.
- Strong and mobile - this is the type of sanguine. All processes occurring in the cerebral cortex are strong and active. Strong, but inert, or phlegmatic type, characterized by a low rate of switching of nervous processes.
Types of the nervous system are interconnected with temperaments, but these concepts should be distinguished, because temperament characterizes a set of psycho-emotional qualities, and the type of the central nervous system describes the physiological features of the processes occurring in the central nervous system.
CNS protection
The anatomy of the nervous system is very complex. The CNS and PNS suffer from the effects of stress, overexertion, and malnutrition. Vitamins, amino acids and minerals are necessary for the normal functioning of the central nervous system. Amino acids take part in the work of the brain and are the building material for neurons. Having figured out why and what vitamins and amino acids are needed for, it becomes clear how important it is to provide the body with the necessary amount of these substances. Glutamic acid, glycine and tyrosine are especially important for humans. The scheme of taking vitamin-mineral complexes for the prevention of diseases of the central nervous system and PNS is selected individually by the attending physician.
Damage to bundles of nerve fibers, congenital pathologies and anomalies in the development of the brain, as well as the action of infections and viruses - all this leads to disruption of the central nervous system and PNS and the development of various pathological conditions. Such pathologies can cause a number of very dangerous diseases- immobilization, paresis, muscle atrophy, encephalitis and much more.
Malignant neoplasms in the brain or spinal cord lead to a number of neurological disorders. On suspicion of cancer The central nervous system is assigned an analysis - the histology of the affected departments, that is, an examination of the composition of the tissue. A neuron, as part of a cell, can also mutate. Such mutations can be detected by histology. Histological analysis is carried out according to the testimony of a doctor and consists in collecting the affected tissue and its further study. With benign formations, histology is also performed.
There are many nerve endings in the human body, damage to which can cause a number of problems. Damage often leads to a violation of the mobility of a part of the body. For example, an injury to the hand can lead to pain in the fingers and impaired movement. Osteochondrosis of the spine provoke the occurrence of pain in the foot due to the fact that an irritated or transmitted nerve sends pain impulses to receptors. If the foot hurts, people often look for the cause in a long walk or injury, but the pain syndrome can be triggered by damage to the spine.
If you suspect damage to the PNS, as well as any related problems, you should be examined by a specialist.
Neurons – they are the workhorses of the nervous system. They send and receive signals to and from the brain through a network of interconnections so numerous and complex that it is quite impossible to count them or draw a complete diagram of them. At best, you can roughly say that there are hundreds of billions of neurons in the brain and many times more connections between them.
Figure 1. Neurons
Brain tumors that arise from neurons or their precursors include embryonic tumors (previously called primitive neuroectodermal tumors - PNETs), such as medulloblastoma And pineoblastoma.
Type II brain cells are called neuroglia. In the literal sense, this word means “glue that holds the nerves together” - thus, the auxiliary role of these cells is already visible from the name itself. Another part of neuroglia contributes to the work of neurons, surrounding them, nourishing and removing their decay products. There are many more neuroglial cells in the brain than neurons, and more than half of brain tumors develop from neuroglia.
Tumors arising from neuroglial (glial) cells are generally referred to as gliomas. However, depending on the specific type of glial cells involved in the tumor, it may have one or another specific name. The most common glial tumors in children are cerebellar and hemispheric astrocytomas, brainstem gliomas, optic tract gliomas, ependymomas, and gangliogliomas. Types of tumors are described in more detail in this article.
The structure of the brain
The brain has a very complex structure. There are several large sections of it: large hemispheres; brain stem: midbrain, pons, medulla oblongata; cerebellum.
Figure 2. The structure of the brain
If you look at the brain from above and from the side, then we will see the right and left hemispheres, between which there is a large furrow separating them - the interhemispheric, or longitudinal fissure. Deep in the brain is corpus callosum– a bundle of nerve fibers that connects the two halves of the brain and allows information to be transmitted from one hemisphere to the other and vice versa. The surface of the hemispheres is indented by more or less deeply penetrating fissures and furrows, between which convolutions are located.
The folded surface of the brain is called the cortex. It is formed by the bodies of billions of nerve cells, because of their dark color, the substance of the cortex was called "gray matter". The cortex can be viewed as a map, where different areas are responsible for different functions of the brain. The cortex covers the right and left hemispheres of the brain.
It is the hemispheres of the brain that are responsible for processing information from the senses, as well as for thinking, logic, learning and memory, that is, for those functions that we call the mind.
Figure 3. The structure of the cerebral hemisphere
Several large depressions (furrows) divide each hemisphere into four lobes:
- frontal (frontal);
- temporal;
- parietal (parietal);
- occipital.
frontal lobes provide "creative", or abstract, thinking, expression of emotions, expressiveness of speech, control arbitrary movements. They are largely responsible for the intellect and social behavior of a person. Their functions include action planning, prioritization, concentration, memory, and behavior control. Damage to the anterior frontal lobe can lead to aggressive antisocial behavior. At the back of the frontal lobes is motor (motor) zone where certain areas govern different types motor activity: swallowing, chewing, articulation, movements of the arms, legs, fingers, etc.
Sometimes, before brain surgery, stimulation of the cortex is done to get an accurate picture of the motor area with an indication of the functions of each area: otherwise there is a danger of damage or removal of tissue fragments important for these functions.
parietal lobes are responsible for the sense of touch, the perception of pressure, pain, heat and cold, as well as for computational and speech skills, and the orientation of the body in space. In front of the parietal lobe is the so-called sensory (sensitive) zone, where information about the influence of the surrounding world on our body converges from pain, temperature and other receptors.
temporal lobes largely responsible for memory, hearing and the ability to perceive oral or written information. They also have additional complex objects. So, amygdala (tonsils) play an important role in the occurrence of such states as excitement, aggression, fear or anger. In turn, the amygdala is connected to the hippocampus, which facilitates the formation of memories from experienced events.
Occipital lobes- the visual center of the brain, analyzing the information that comes from the eyes. The left occipital lobe receives information from the right visual field, while the right lobe receives information from the left. Although all lobes of the cerebral hemispheres are responsible for certain functions, they do not act alone, and no single process is associated with only one particular lobe. Due to the huge network of interconnections in the brain, there is always communication between different hemispheres and lobes, as well as between subcortical structures. The brain functions as a whole.
Cerebellum-a smaller structure located in the lower back of the brain, under the cerebral hemispheres, and separated from them by a process of the dura mater - the so-called cerebellar tenon or tent of the cerebellum (tentorium). In size, it is approximately eight times smaller than the forebrain. The cerebellum continuously and automatically performs fine regulation of the coordination of movements and balance of the body.
If a tumor grows in the cerebellum, the patient may experience gait (atactic gait) or movement problems (sharp jerky movements). There may also be problems with the work of the hands and the eye.
brain stem descends from the center of the brain and passes in front of the cerebellum, after which it merges with the upper part of the spinal cord. The brain stem is responsible for basic bodily functions, many of which are carried out automatically, outside of our conscious control, such as heartbeat and breathing. The trunk includes the following parts:
- Medulla which governs breathing, swallowing, blood pressure and heart rate.
- Pons (or simply bridge), which connects the cerebellum to the cerebrum.
- midbrain, which is involved in the implementation of the functions of vision and hearing.
Runs along the entire brain stem reticular formation (or reticular substance) is a structure that is responsible for awakening from sleep and for arousal reactions, and also plays an important role in the regulation of muscle tone, respiration and heart rate.
diencephalon located above the midbrain. It includes, in particular, the thalamus and hypothalamus. Hypothalamus – it is a regulatory center involved in many important functions of the body: in the regulation of hormone secretion (including hormones from the nearby pituitary gland), in the functioning of the autonomic nervous system, digestion and sleep processes, as well as in the control of body temperature, emotions, sexuality, etc. Located above the hypothalamus thalamus, which processes a significant part of the information coming to and from the brain.
12 pairs of cranial nerves in medical practice, they are numbered in Roman numerals from I to XII, while in each of these pairs one nerve corresponds to the left side of the body, and the other to the right. The cranial nerve originates from the brain stem. They control important functions such as swallowing, muscle movements of the face, shoulders and neck, and sensations (sight, taste, hearing). The main nerves that carry information to the rest of the body run through the brainstem.
Nerve endings cross in the medulla oblongata so that the left side of the brain controls right side bodies and vice versa. Therefore, tumors formed in the left or right side of the brain can affect the mobility and sensation of the opposite side of the body (the exception here is the cerebellum, where the left side sends signals to the left arm and left leg, and the right side to the right limbs).
Meninges nourish and protect the brain and spinal cord. They are located in three layers under each other: immediately under the skull is hard shell(dura mater), which has the largest number of pain receptors in the body (there are none in the brain), under it gossamer(arachnoidea), and below - closest to the brain vascular, or soft shell(pia mater).
Spinal (or cerebrospinal) fluid is a transparent watery liquid that forms another protective layer around the brain and spinal cord, softening shocks and concussions, nourishing the brain and removing unnecessary products of its vital activity. In a normal situation, cerebrospinal fluid is important and useful, but it can also play a role harmful to the body if a brain tumor blocks the outflow of cerebrospinal fluid from the ventricle or if cerebrospinal fluid is produced in excess. Then the fluid accumulates in the brain. Such a state is called hydrocephalus, or dropsy of the brain. Since there is practically no free space for excess fluid inside the skull, increased intracranial pressure (ICP) occurs.
The structure of the spinal cord
Spinal cord- this is actually a continuation of the brain, surrounded by the same membranes and cerebrospinal fluid. It makes up two-thirds of the central nervous system and is a kind of conduction system for nerve impulses.
Figure 4. The structure of the vertebra and the location of the spinal cord in it
The spinal cord makes up two-thirds of the CNS and is a kind of conduction system for nerve impulses. Sensory information (touch sensations, temperature, pressure, pain) goes through it to the brain, and motor commands (motor function) and reflexes go from the brain through the spinal cord to all parts of the body. Flexible, made of bones spinal column protects the spinal cord from external influences. The bones that make up the spine are called vertebrae; their protruding parts can be felt along the back and back of the neck. Different parts of the spine are called departments (levels), there are five in total: cervical ( WITH), chest ( Th), lumbar ( L), sacral ( S) and coccygeal
The human nervous system is an important part of the body, which is responsible for many ongoing processes. Her diseases have a bad effect on the human condition. It regulates the activity and interaction of all systems and organs. With the current environmental background and constant stress, it is necessary to pay serious attention to the daily routine and proper nutrition to avoid potential health problems.
general information
The nervous system affects the functional interaction of all human systems and organs, as well as the connection of the body with the outside world. Its structural unit - a neuron - is a cell with specific processes. Neural circuits are built from these elements. The nervous system is divided into central and peripheral. The first includes the brain and spinal cord, and the second - all the nerves and nerve nodes extending from them.
somatic nervous system
In addition, the nervous system is divided into somatic and autonomic. The somatic system is responsible for the interaction of the body with the outside world, for the ability to move independently and for sensitivity, which is provided with the help of the sense organs and some nerve endings. The ability of a person to move is provided by the control of the skeletal and muscle mass carried out by the nervous system. Scientists also call this system animal, because only animals can move and have sensitivity.
autonomic nervous system
This system is responsible for the internal state of the body, that is, for:
The human autonomic nervous system, in turn, is divided into sympathetic and parasympathetic. The first is responsible for the pulse, blood pressure, bronchi and so on. Its work is controlled by the spinal centers, from which come the sympathetic fibers located in the lateral horns. Parasympathetic is responsible for the work of the bladder, rectum, genital organs and for a number of nerve endings. Such multifunctionality of the system is explained by the fact that its work is carried out both with the help of the sacral part of the brain and through its trunk. The control of these systems is carried out by specific vegetative apparatuses that are located in the brain.
Diseases
The human nervous system is extremely susceptible to outside influence, there are a variety of reasons that can cause its diseases. Most often, the vegetative system suffers due to the weather, while a person can feel bad both in too hot times and in cold winters. There are a number of characteristic symptoms for such diseases. For example, a person turns red or pale, the pulse speeds up, or excessive sweating begins. In addition, such diseases can be acquired.
How do these diseases appear?
They can develop due to head trauma, or arsenic, or due to a complex and dangerous infectious disease. Such diseases can also develop due to overwork, due to a lack of vitamins, with mental disorders or constant stress.
You have to be careful when hazardous conditions labor, which can also affect the development of diseases of the autonomic nervous system. In addition, such diseases can masquerade as others, some of them resemble heart disease.
central nervous system
It is formed from two elements: the spinal cord and the brain. The first of them looks like a cord, slightly flattened in the middle. In an adult, its size varies from 41 to 45 cm, and the weight reaches only 30 grams. The spinal cord is completely surrounded by membranes that are located in a specific canal. The thickness of the spinal cord does not change along its entire length, except for two places, which are called the cervical and lumbar thickenings. It is here that the nerves of the upper as well as the lower extremities are formed. It is subdivided into such departments as cervical, lumbar, thoracic and sacral.
Brain
It is located in the human cranium and is divided into two components: the left and right hemispheres. In addition to these parts, the trunk and cerebellum are also distinguished. Biologists were able to determine that the brain of an adult male is 100 mg heavier than a female. This is due solely to the fact that all parts of the body of the stronger sex are larger than female in physical parameters due to evolution.
The fetal brain begins to actively grow even before birth, in the womb. It stops its development only when a person reaches 20 years of age. In addition, in old age, towards the end of life, it becomes a little easier.
Sections of the brain
There are five main parts of the brain:
In the event of a traumatic brain injury, the central nervous system of a person can be seriously affected, and this is bad for mental state person. With such disorders, patients may have voices in their heads that are not so easy to get rid of.
Shells of the brain
Three types of membranes cover the brain and spinal cord:
- The hard shell covers the outside of the spinal cord. In shape, it is very similar to a bag. It also functions as the periosteum of the skull.
- The arachnoid is a substance that practically adheres to the solid. Neither the dura mater nor the arachnoid contains blood vessels.
- The pia mater is a collection of nerves and vessels that feed both brains.
Brain Functions
This is very hard part an organism on which the entire human nervous system depends. Even considering that a huge number of scientists are studying the problems of the brain, all its functions have not been fully studied yet. The most difficult puzzle for science is the study of the features of the visual system. It is still unclear how and with what parts of the brain we have the ability to see. People far from science mistakenly believe that this happens solely with the help of the eyes, but this is absolutely not the case.
Scientists involved in the study of this issue believe that the eyes only perceive the signals that the surrounding world sends, and in turn transmit them to the brain. Receiving a signal, it creates a visual picture, that is, in fact, we see what our brain shows. Similarly, it happens with hearing, in fact, the ear only perceives the sound signals received through the brain.
Conclusion
Diseases are currently vegetative system very common in the younger generation. This is due to many factors, such as poor condition environment, improper daily routine or irregular and improper nutrition. To avoid such problems, it is recommended to carefully monitor your schedule, avoid various stresses and overwork. After all, the health of the central nervous system is responsible for the state of the whole organism, otherwise such problems can provoke serious disturbances in the work of other important organs.
The main structural and physiological unit of the NS is the neuron. This is a nerve cell that has a body, processes and an axon (main process). The processes or dendrites are very branched and form a large number of synapses (contacts). A synapse is the space between two neurons in which impulse transmission takes place at the chemical level. One neuron can have up to 1800 synapses. Each neuron has 3 functions:- receives a nerve impulse;
- creates its momentum;
- carries the excitement further.
- sensitive- from receptors transmit signals to the CNS. They are in the nerve nodes outside the CNS.
- Motor- transmit impulses from the central nervous system to muscle tissue and organs.
- mixed- work in two directions.
Important! The unique form of work of the nervous system allows us to adequately interact with the world not only through response actions, but also through personal mental reactions (motivations, emotions).
Structure and functions
The nervous system is divided into 2 major systems:- central (CNS);
- peripheral (PNS).
- CNS includes:
- brain;
- spinal cord.
- PNS is divided into:
- somatic nervous system;
- autonomic (autonomic) nervous system.
- sympathetic;
- parasympathetic.
Department functions
The CNS is the backbone of the entire system. Its task is to implement reflective reactions or “reflexes”. In the central nervous system, three sections are distinguished - the higher (cortex of the hemispheres), the middle and lower (spinal, medulla oblongata, middle, diencephalon and cerebellum). The higher one works on communication with the outside world, while the middle and lower ones are responsible for the harmonious work of the whole organism and the connection within it. The cerebral cortex is the main part of the NS. It processes all incoming information and controls all muscle movements. The spinal cord is securely hidden in the spinal canal. This is a tube about 45 cm long and 1 cm in diameter. PNS is allocated conditionally as a part of the nervous system, located outside the CNS. The PNS exists to connect the brain with the organs. It can be damaged by external influences, since it does not have such reliable protection as the central nervous system. Peripheral NS includes two subsystems:- Somatic- is a complex of nerve fibers, motor and sensory, which are responsible for the excitation of muscle tissue, epidermis and joints. Coordination of movements depends on it, as well as receiving stimuli from the outside. She is responsible for the implementation of conscious actions.
- Vegetative- it provides the transmission of signals from the internal environment of the body, controls the work of the heart and other organs, smooth muscles, glands. It is divided into two systems:
- sympathetic- gives a response to stress, can also cause heart palpitations, increase blood pressure, excite the senses, increasing the level of adrenaline.
- parasympathetic- is responsible for the state of rest, its area of action includes pupil contraction, slowing the rhythm of the heartbeat, stimulation of the digestive and genitourinary systems.
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