Nervous system. How the human nervous system works

The nervous system is the highest integrating and coordinating system of the human body, which ensures the coordinated activity of internal organs and the connection of the body with the external environment.

Anatomically, the nervous system is divided into the central (brain and spinal cord); and peripheral, including 12 pairs of cranial nerves, 31 pairs of spinal nerves and nerve nodes located outside the brain and spinal cord.

The function of the nervous system is divided into:

the somatic nervous system - mainly carries out the connection of the body with the external environment: the perception of irritations, the regulation of movements of the striated muscles, etc.

autonomic (autonomous) nervous system - regulates metabolism and the functioning of internal organs: heartbeat, vascular tone, peristaltic contractions of the intestine, secretion of various glands, etc. The autonomic nervous system is divided into parasympathetic and sympathetic nervous systems.

Both of them function in close interaction, however, the autonomic nervous system has some independence, controlling involuntary functions.

The nervous system is made up of nerve cells called neurons. There are 25 billion neurons in the brain, and 25 million cells in the periphery. The bodies of neurons are located mainly in the CNS. Gray matter is a collection of neurons. In the spinal cord, it is located in the center, surrounding the spinal canal. In the brain, on the contrary, the gray matter is located on the surface, forming a cortex and separate clusters - nuclei concentrated in the white matter.

White matter is under gray and is composed of nerve fibers (neuronal processes) covered with sheaths. Nerve ganglions also consist of bodies of neurons. Nerve fibers that extend beyond the CNS and nerve nodes, connecting, compose nerve bundles, and several such bundles form individual nerves.

Centripetal, or sensitive - nerves that conduct excitation from the periphery to the central nervous system. For example, visual, olfactory, auditory.

Centrifugal, or motor - nerves through which excitation is transmitted from the central nervous system to the organs. For example, oculomotor.

Mixed (wandering, spinal), if excitation goes in one direction along one fiber, and in the other direction along the other.

Functions nervous system: regulates the activity of all organs and organ systems, communicates with the external environment through the sense organs; is the material basis for higher nervous activity, thinking, behavior and speech.

The structure and function of the spinal cord.

The spinal cord is located in the spinal canal from the 1st cervical vertebra to the 1st - 2nd lumbar, its length is about 45 cm, thickness is about 1 cm. The anterior and posterior longitudinal grooves divide it into two symmetrical halves. In the center is the spinal canal, which contains the cerebrospinal fluid. In the middle part of the spinal cord, near the spinal canal, there is gray matter, which in cross section resembles the contour of a butterfly. The gray matter is formed by the bodies of neurons, it distinguishes between the anterior and posterior horns. The bodies of intercalary neurons are located in the posterior horns of the spinal cord, and the bodies of motor neurons are located in the anterior horns. In the thoracic region, lateral horns are also distinguished, in which the neurons of the sympathetic part of the autonomic nervous system are located. Surrounding the gray matter is white matter formed by nerve fibers. The spinal cord is covered by three membranes:

hard shell - outer, connective tissue, lining the inner cavity of the skull and spinal canal;

arachnoid - located under the solid. This is a thin shell with a small number of nerves and vessels;

the choroid is fused with the brain, enters the furrows and contains many blood vessels.

Fluid-filled cavities form between the vascular and arachnoid membranes.

31 pairs of mixed spinal nerves leave the spinal cord. Each nerve begins with two roots: the anterior (motor), in which the processes of motor neurons and autonomic fibers are located, and the posterior (sensory), through which excitation is transmitted to the spinal cord. In the posterior roots are the spinal nodes - clusters of sensory neuron bodies.

Transection of the posterior roots leads to a loss of sensation in those areas that are innervated by the corresponding roots, and transection of the anterior roots leads to paralysis of the innervated muscles.

The functions of the spinal cord are reflex and conduction. As a reflex center, the spinal cord takes part in motor (conducts nerve impulses to the skeletal muscles) and autonomic reflexes. The most important autonomic reflexes of the spinal cord are vasomotor, food, respiratory, defecation, urination, sexual. The reflex function of the spinal cord is under the control of the brain.

The reflex functions of the spinal cord can be examined on the spinal preparation of a frog (without a brain), which retains the simplest motor reflexes. She withdraws her paw in response to mechanical and chemical stimuli. In humans, the brain is of decisive importance in the implementation of the coordination of motor reflexes.

The conduction function is carried out due to the ascending and descending paths of the white matter. Along the ascending paths, excitation from the muscles and internal organs is transmitted to the brain, along the descending paths, from the brain to the organs.

The structure and functions of the brain.

There are five sections in the brain: the medulla oblongata; the hindbrain, which includes the bridge and the cerebellum; midbrain; diencephalon and forebrain, represented by the large hemispheres. Up to 80% of the mass of the brain falls on the cerebral hemispheres. The central canal of the spinal cord continues into the brain, where it forms four cavities (ventricles). Two ventricles are located in the hemispheres, the third - in the diencephalon, the fourth - at the level of the medulla oblongata and the bridge. They contain cranial fluid. The brain, as well as the spinal cord, is surrounded by three membranes - connective tissue, arachnoid and vascular.

The medulla oblongata is a continuation of the spinal cord, performs reflex and conduction functions. Reflex functions are associated with the regulation of the work of the respiratory, digestive, and circulatory organs. Here are the centers of protective reflexes - coughing, sneezing, vomiting.

The bridge connects the cerebral cortex with the spinal cord and cerebellum, performing mainly a conductive function.

The cerebellum is formed by two hemispheres, externally covered with a bark of gray matter, under which is white matter. The white matter contains nuclei. The middle part of the cerebellum - the worm - connects its hemispheres. The cerebellum is responsible for coordination, balance and influences muscle tone. When the cerebellum is damaged, there is a decrease in muscle tone and a disorder in the coordination of movements, but after a while other parts of the nervous system begin to perform the functions of the cerebellum, and the lost functions are partially restored. Together with the bridge, the cerebellum is part of the hindbrain.

The midbrain connects all parts of the brain. Here are the centers of skeletal muscle tone, the primary centers of visual and auditory orienting reflexes, which are manifested in the movements of the eyes and head towards stimuli.

In the diencephalon, three parts are distinguished: the visual tubercles (thalamus), the epithalamic region (epithalamus), which includes the pineal gland, and the hypothalamic region (hypothalamus). The subcortical centers of all types of sensitivity are located in the thalamus, excitation from the sense organs comes here, and from here it is transmitted to various parts of the cerebral cortex. The hypothalamus contains the highest regulatory centers of the autonomic nervous system. It controls the constancy of the internal environment of the body. Here are the centers of appetite, thirst, sleep, thermoregulation, i.e. regulation of all types of metabolism. Neurons of the hypothalamus produce neurohormones that regulate the functioning of the endocrine system. In the diencephalon there are also emotional centers: centers of pleasure, fear, aggression. Together with the hindbrain and medulla, the diencephalon is part of the brainstem.

The forebrain is represented by the cerebral hemispheres connected by the corpus callosum. The surface of the forebrain is formed by the cortex, the area of ​​which is about 2200 cm 2. Numerous folds, convolutions and furrows significantly increase the surface of the cortex. The surface of the convolutions is more than two times smaller than the surface of the furrows. The human cortex has from 14 to 17 billion nerve cells arranged in 6 layers, the thickness of the cortex is 2-4 mm. Accumulations of neurons in the depths of the hemispheres form subcortical nuclei. The cerebral cortex consists of 4 lobes: frontal, parietal, temporal and occipital, separated by furrows. In the cortex of each hemisphere, the central sulcus separates the frontal lobe from the parietal, the lateral sulcus separates the temporal lobe, and the parietal-occipital sulcus separates the occipital lobe from the parietal.

In the cortex, sensory, motor and associative zones are distinguished. Sensitive zones are responsible for the analysis of information coming from the sense organs: occipital - for vision, temporal - for hearing, smell and taste; parietal - for skin and joint-muscular sensitivity. Moreover, each hemisphere receives impulses from the opposite side of the body. The motor zones are located in the posterior regions of the frontal lobes, from here come the commands for contraction of the skeletal muscles, their defeat leads to muscle paralysis. Associative zones are located in the frontal lobes of the brain and are responsible for the development of programs for behavior and management of human labor activity; their mass in humans is more than 50% of the total mass of the brain.

A person is characterized by a functional asymmetry of the hemispheres: the left hemisphere is responsible for abstract-logical thinking, speech centers are also located there (Brock's center is responsible for pronunciation, Wernicke's center for understanding speech), the right hemisphere is for figurative thinking, musical and artistic creativity.

Due to the strong development of the cerebral hemispheres, the average mass of the human brain is 1400 g on average.

The structure and functions of the human nervous system are so complex that a separate section of anatomy called neuroanatomy is devoted to their study. The central nervous system is responsible for everything, for the very life of a person - and this is not an exaggeration. If there is a deviation in the functional activity of one of the departments, the integrity of the system is violated, and human health is endangered.

The nervous system is a collection of anatomically and functionally interconnected nerve cells with their processes. Distinguish between the central and peripheral nervous systems. The central nervous system includes the brain and spinal cord, and the peripheral nervous system includes cranial and spinal nerves and related roots, spinal nodes and plexuses.

The main function of the nervous system is the regulation of the vital activity of the body, maintaining the constancy of the internal environment, metabolic processes in it, as well as the implementation of communication with the outside world.

The nervous system consists of nerve cells, nerve fibers and neuroglial cells.

You will learn more about the structure and functions of the nervous system from this article.

Neuron as a structural and functional unit of the human nervous system

A nerve cell - a neuron - is a structural and functional unit of the nervous system. A neuron is a cell capable of perceiving irritation, becoming excited, generating nerve impulses and transmitting them to other cells.

That is, the neuron of the nervous system performs two functions:

1. Processes incoming information and transmits a nerve impulse
2. Maintains its vitality

A neuron as a structural unit of the nervous system consists of a body and processes - short, branching (dendrites) and one long (axon), which can give numerous branches. The point of contact between neurons is called a synapse. Synapses can be between an axon and the body of a nerve cell, an axon and a dendrite, two axons, and less often between two Dendrites. In synapses, impulses are transmitted bioelectrically or through chemically active substances of mediators (acetylcholine, norepinephrine, dopamine, serotonin, etc.). Numerous neuropeptides (enkephalins, endorphins, etc.) also participate in synaptic transmission.

Transportation of biologically active substances along the axon from the body of a neuron in the central nervous system to the synapse and back (axonal transport) ensures the supply and renewal of mediators, as well as the formation of new processes - axons and dendrites. Thus, two interconnected processes are constantly going on in the brain - the appearance of new processes and synapses and the partial disintegration of those that already existed. And this underlies learning, adaptation, as well as restoration and compensation of impaired functions.

The cell membrane (cell membrane) is a thin lipoprotein plate penetrated by channels through which K, Na, Ca, C1 ions selectively flow. The functions of the cell membrane of the human nervous system are the creation of an electric charge of the cell, due to which excitation and impulse arise.

Neuroglia is a connective tissue supporting structure of the nervous system (stroma) that performs a protective function.

Interlacing of axons, dendrites and processes of glial cells create a picture of a neuropil.

The nerve fiber in the structure of the nervous system is a process of the nerve cell (axial cylinder), covered to a greater or lesser extent by myelin and surrounded by the Schwann sheath, which performs protective and trophic functions. In myelin fibers, the impulse moves at a speed of up to 100 m/sec.

The accumulation of bodies of neurons in the human nervous system forms the gray matter of the brain, and their processes form the white matter. The collection of neurons located outside the central nervous system is called the ganglion. A nerve is a trunk of combined nerve fibers. Depending on the function, motor, sensory, autonomic and mixed nerves are distinguished.

Speaking about the structure of the human nervous system, a set of neurons that regulate any function is called the nerve center. The complex of physiological mechanisms associated with the performance of a particular function is called a functional system.

It includes cortical and subcortical nerve centers, pathways, peripheral nerves, and executive organs.

The basis of the functional activity of the nervous system is a reflex. A reflex is the body's response to a stimulus. A reflex is carried out through a chain of neurons (at least two), called a reflex arc. The neuron that perceives irritation is the afferent part of the arc; the neuron that carries out the response is the efferent part. But the reflex act does not end with a one-time response of the working body. There is a feedback that affects muscle tone - a self-regulatory ring in the form of a gamma loop.

The reflex activity of the nervous system ensures that the body perceives any changes in the external world.

The ability to perceive external phenomena is called reception. Sensitivity is the ability to feel stimuli perceived by the nervous system. The formations of the central and peripheral nervous system that perceive and analyze information about phenomena both inside the body and in the environment are called analyzers. There are visual, auditory, gustatory, olfactory, sensory and motor analyzers. Each analyzer consists of a peripheral (receptor) section, a conductive part and a cortical section, in which the analysis and synthesis of perceived stimuli takes place.

Since the central sections of various analyzers are located in the cerebral cortex, all information coming from the external and internal environment is concentrated in it, which is the basis for mental higher nervous activity. Analysis of the information received by the cortex is recognition, gnosis. The functions of the cerebral cortex also include the development of action plans (programs) and their implementation - praxis.

The following describes how the spinal cord of the human nervous system is arranged.

The human central nervous system: how the spinal cord works (with photo)

The spinal cord as part of the central nervous system is a cylindrical cord 41-45 cm long, located in the spinal canal from the first cervical vertebra to the second lumbar. It has two thickenings - cervical and lumbosacral, providing innervation of the limbs. The lumbosacral thickening passes into the brain cone, ending in a filiform continuation - the terminal thread, reaching the end of the spinal canal. The spinal cord performs conduction and reflex functions.

The spinal cord of the nervous system has a segmental structure. A segment is a section of the spinal cord with two pairs of spinal roots. In total, the spinal cord has 31-32 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1-2 coccygeal (rudimentary). The anterior and posterior horns of the spinal cord, the anterior and posterior spinal roots, spinal nodes and spinal nerves make up the segmental apparatus of the spinal cord. As the spine develops, it becomes longer than the spinal cord, so the roots, lengthening, form a ponytail.

On a section of the spinal cord of the human nervous system, gray and white matter can be seen. The gray matter consists of cells, looks like the letter "H" with anterior - motor horns, posterior - sensitive and lateral - vegetative. The central canal of the spinal cord runs through the center of the gray matter. The median fissure (front) and the median sulcus (rear) divide the spinal cord into left and right halves, interconnected by white and gray patches.

The gray matter is surrounded by nerve fibers - conductors that form the white matter, in which the anterior, lateral and posterior columns are distinguished. The anterior pillars are located between the anterior horns, the posterior ones between the posterior ones, and the lateral ones between the anterior and posterior horns of each side.

These photos show the structure of the spinal cord of the human nervous system:

Spinal nerves in the nervous system

The spinal nerves in the human nervous system are formed by the fusion of the anterior (motor) and posterior (sensory) roots of the spinal cord and exit the spinal canal through the intervertebral foramens. Each pair of these nerves innervates a certain part of the body - the metamere.

Leaving the spinal canal, the spinal nerves of the nervous system are divided into four branches:

1. Front, innervating the skin and muscles of the limbs and the anterior surface of the body;
2. Rear, innervating the skin and muscles of the back surface of the body;
3. Meningeal heading to the hard shell of the spinal cord;
4. connecting, next to the sympathetic nodes.

Front branches spinal nerves form plexuses: cervical, brachial, lumbar, sacral and coccygeal.

cervical plexus formed by the anterior branches of the cervical nerves C:-C4; innervates the skin of the back of the head, the lateral surface of the face, the supra-, subclavian and upper scapular regions, the diaphragm.

Brachial plexus formed by the anterior branches of C4-T1; innervates the skin and muscles of the upper limb.

Front branches T2-T11, without forming a plexus, together with the posterior branches provide innervation of the skin and muscles of the chest, back and abdomen.

Lumbosacral plexus is a combination of the lumbar and sacral.

Lumbar plexus formed by the anterior branches of T12 -L 4; innervates the skin and muscles of the lower abdomen, anterior and lateral thighs.

sacral plexus formed by the anterior branches of the L5-S4 nerves; innervates the skin and muscles of the gluteal region, perineum, back of the thigh, lower leg and foot. From it departs the largest nerve of the body - the sciatic.

coccygeal plexus formed by the anterior branches of S5-C0C2; innervates the perineum.

The next section of the article is devoted to the structure and functions of the main parts of the brain.

The human nervous system: the structure and functions of the main parts of the brain

The brain, which is part of the nervous system, is located in the cranium, covered with the meninges, between which cerebrospinal fluid (CSF) circulates. Through the foramen magnum, the brain is connected to the spinal cord. The mass of the brain of an adult is on average 1300-1500 g. The function of the human brain is to regulate all processes occurring in the body.

The brain as part of the nervous system consists of the following sections: two hemispheres, the cerebellum and the trunk.

In the brain stem, the medulla oblongata, the pons, the legs of the brain (midbrain), as well as the base and the tire are isolated.

The medulla oblongata is like a continuation of the spinal cord. The intersection of the pyramidal tracts serves as a conditional border between the medulla oblongata and the spinal cord. In the medulla oblongata there are vital centers that regulate breathing, blood circulation, swallowing; it contains all the motor and sensory pathways connecting the spinal cord and brain.

The structure of the bridge of the nervous system of the brain includes the nuclei of the V, VI, VII and VIII pairs of cranial nerves, sensory pathways as part of the medial loop, fibers of the auditory pathway in the form of a lateral loop, etc.

The cerebral peduncles are part of the midbrain, they connect the bridge to the hemispheres and include ascending and descending pathways. The roof of the midbrain has a plate on which the quadrigemina is located. In the upper colliculus is the primary subcortical center of vision, in the lower colliculus - the primary subcortical center of hearing. Thanks to the mounds, the orientation and protective reactions of the body are carried out, which occur under the influence of visual and auditory stimuli. Under the roof of the midbrain is the aqueduct of the midbrain, which connects the III and IV ventricles of the cerebral hemispheres.

The diencephalon consists of the thalamus (thalamus), epithalamus, metathalamus, and hypothalamus. The cavity of the diencephalon is the third ventricle. The thalamus is a cluster of nerve cells located on both sides of the third ventricle. The thalamus is one of the subcortical centers of vision and the center of afferent impulses from the whole body, heading to the cerebral cortex. In the thalamus, the formation of sensations and the transmission of impulses to the extra-pyramidal system take place.

The metathalamus in the brain of the human nervous system also contains one of the subcortical centers of vision and the subcortical center of hearing (medial and lateral geniculate body).

The epithalamus includes the pineal gland, which is an endocrine gland that regulates the function of the adrenal cortex and the development of sexual characteristics.

The hypothalamus consists of a gray tubercle, funnel, cerebral appendage (neurohypophysis) and paired mastoid bodies. In the hypothalamus there are accumulations of gray matter in the form of nuclei, which are the centers of the autonomic nervous system that regulate all types of metabolism, respiration, blood circulation, the activity of internal organs and endocrine glands. The hypothalamus maintains a constancy of the internal environment in the body (homeostasis) and, thanks to connections with the limbic system, participates in the formation of emotions, carrying out their vegetative coloring.

Along the entire length of the brain stem, a phylogenetically ancient formation of gray matter is located and occupies a central position in the form of a dense network of nerve cells with many processes - the reticular formation. Branches from all types of sensitive systems are sent to the reticular formation, so any irritation coming from the periphery is transmitted by it along ascending paths to the cerebral cortex, activating its activity. Thus, the reticular formation is involved in the implementation of normal biological rhythms of wakefulness and sleep, is an ascending, activating system of the brain - an "energy generator".

Together with the limbic structures, the reticular formation provides normal cortical-subcortical relationships and behavioral responses. It is also involved in the regulation of muscle tone, and its descending pathways provide reflex activity of the spinal cord.

The cerebellum is located under the occipital lobes of the brain and is separated from them by the dura mater - cerebellar tenon. It distinguishes the central part - the cerebellar vermis and the lateral sections - the hemispheres. In the depths of the white matter of the cerebellar hemispheres are the dentate nucleus and smaller nuclei - corky and spherical. The nucleus of the roof is located in the middle part of the cerebellum. The cerebellar nuclei are involved in the coordination of movements and balance, as well as in the regulation of muscle tone. Three pairs of legs connect the cerebellum with all parts of the brain stem, providing its connection with the extrapyramidal system, the cerebral cortex and the spinal cord.

The structure and main functions of the cerebral hemispheres

The structure of the cerebrum includes two hemispheres, interconnected by a large white commissure - the corpus callosum, consisting of fibers that connect the lobes of the brain of the same name. The surface of each hemisphere is covered with a bark consisting of cells and separated by many furrows. The areas of the cortex located between the furrows are called convolutions. The deepest furrows divide each hemisphere into lobes: frontal, parietal, occipital and temporal. The central (Roland) sulcus separates the parietal lobe from the frontal; in front of it is the precentral gyrus. The frontal lobe is divided by horizontal grooves into the superior, middle, and inferior gyrus.

Behind the central sulcus in the structure of the cerebral hemispheres is the postcentral gyrus. The parietal lobe is divided by a transverse intraparietal sulcus into superior and inferior parietal lobules.

A deep lateral (Sylvian) furrow separates the temporal lobe from the frontal and parietal. On the lateral surface of the temporal lobe, the superior, middle, and inferior temporal gyri are located longitudinally. On the inner surface of the temporal lobe is a gyrus called the hippocampus.

On the inner surface of the hemispheres, the parietal-occipital sulcus separates the parietal lobe from the occipital one, and the spur sulcus divides the occipital lobe into two gyri - the precuneus and the wedge.

On the medial surface of the hemispheres above the corpus callosum, the cingulate gyrus is located arcuately, passing into the parahippocampal gyrus.

The cerebral cortex is the youngest evolutionary part of the central nervous system, consisting of neurons. It is most developed in humans. The cortex is a layer of gray matter 1.3-4 mm thick, covering the white matter of the hemispheres, consisting of axons, dendrites of nerve cells and neuroglia.

The cortex plays a very important role in the regulation of vital processes in the body, the implementation of behavioral acts and mental activity.

The function of the cortex of the frontal lobe is the organization of movements, motor skills of speech, complex forms of behavior and thinking. In the precentral gyrus is the center of voluntary movements, from here the pyramidal path begins.

The parietal lobe contains the centers of the analyzer of general sensitivity, gnosis, praxis, writing, counting.

The functions of the temporal lobe of the large brain are the perception and processing of auditory, gustatory and olfactory sensations, the analysis and synthesis of speech sounds, and memory mechanisms. The basal parts of the cerebral hemispheres are connected with the higher autonomic centers.

In the occipital lobe are the cortical centers of vision.

Not all functions of the cerebral hemispheres are represented symmetrically in the cortex. For example, speech, reading and writing in most people are functionally related to the left hemisphere.

The right hemisphere provides orientation in time, place, connected with the emotional sphere.

The axons and dendrites of the nerve cells of the cortex make up the pathways that connect the various sections of the cortex, the cortex and other sections of the brain and spinal cord. The pathways form a radiant crown, consisting of fan-shaped diverging fibers, and an internal capsule located between the basal (subcortical) nuclei.

Subcortical nuclei (caudate, lenticular, amygdala, fence) are located deep in the white matter around the ventricles of the brain. Morphologically and functionally, the caudate nucleus and the shell are combined into the striatum (striatum). The pale ball, the red nucleus, the black substance and the reticular formation of the midbrain are combined into a pale body (pallidum). The striatum and pallidum form a very important functional system - striopallidar or extrapyramidal. The extrapyramidal system provides training for various muscle groups to perform a holistic movement, also provides mimic, auxiliary and friendly movements, gestures, automated motor acts (grimaces, whistles, etc.).

A special role is played by the most evolutionarily ancient sections of the cerebral cortex, located on the inner surface of the hemispheres - the cingulate and parahippocampal gyrus. Together with the amygdala, olfactory bulb and olfactory tract, they form the limbic system, which is closely related to the reticular formation of the brain stem and constitutes a single functional system - the limbic-reticular complex (LRK). Speaking about the structure and functions of the large brain, it should be noted that the limbic-reticular complex is involved in the formation of instinctive and emotional reactions (food, sexual, defensive instincts, anger, rage, pleasure) of human behavior. LRK also takes part in the regulation of the tone of the cerebral cortex, the processes of sleep, wakefulness, and adaptation.

See how the large brain of the human nervous system works in these photos:

12 pairs of cranial nerves of the nervous system and their functions (with video)

At the base of the brain, 12 pairs of cranial nerves emerge from the medulla. By function, they are divided into sensitive, motor and mixed. In the proximal direction, the cranial nerves are associated with the nuclei of the brainstem, subcortical nuclei, the cerebral cortex and the cerebellum. In the distal direction, cranial nerves are associated with various functional structures (eyes, ears, muscles of the face, tongue, glands, etc.).

I pair - olfactory nerve ( n. olfactorius) . The receptors are located in the mucous membrane of the turbinates, connected to the sensory neurons of the olfactory bulb. Along the olfactory tract, signals enter the primary olfactory centers (the nuclei of the olfactory triangle) and further to the internal parts of the temporal lobe (hippocampus), where the cortical centers of smell are located.

II pair - optic nerves ( n. opticus) . The receptors of this pair of craniocerebral nerves are the cells of the retina, from the ganglionic layer of which the nerves themselves begin. Passing on the basis of the frontal lobes in front of the Turkish saddle, the optic nerves partially cross, forming a chiasma, and are sent as part of the visual tracts to the subcortical visual centers, and from them to the occipital lobes.

III pair - oculomotor nerves ( n. oculomotorius) . They contain motor and parasympathetic fibers that innervate the muscles that lift the upper eyelids, constrict the pupil, and the muscles of the eyeball, with the exception of the superior oblique and abductor.

IV pair - trochlear nerves ( n. trochlearis) . This pair of cranial nerves innervates the superior oblique muscles of the eyes.

V pair - trigeminal nerves ( n. trigeminus) . They are mixed nerves. The sensory neurons of the trigeminal (Gasser) node form three large branches: the ophthalmic, maxillary and mandibular nerves, which emerge from the cranial cavity and innervate the fronto-parietal part of the scalp, facial skin, eyeballs, mucous membranes of the nasal cavities, mouth, anterior two-thirds of the tongue, teeth, dura mater. The central processes of the cells of the Gasser ganglion go deep into the brain stem and connect with the second sensitive neurons, forming a chain of nuclei. Signals from the stem nuclei through the thalamus go to the postcentral gyrus (fourth neuron) of the opposite hemisphere. Peripheral innervation corresponds to the branches of the nerve, segmental - has the form of ring zones. The motor fibers of the trigeminal nerve regulate the masticatory muscles.

VI pair - abducens nerves ( n. abducens) . Innervates the abductor muscles of the eye.

VII pair - facial nerves ( n. facialis) . They innervate the mimic muscles of the face. When leaving the bridge, the intermediate nerve joins the facial nerve, providing taste innervation of the anterior two-thirds of the tongue, parasympathetic innervation of the submandibular and sublingual glands, and lacrimal glands.

VIII pair - cochleovestibular (auditory, vestibulocochlear) nerve ( n. vestibulo-cochlearis) . This pair of cranial nerves provides the function of hearing and balance, has extensive connections with the structures of the extrapyramidal system, cerebellum, spinal cord, and cortex.

IX pair - glossopharyngeal nerves ( n. glossopharyngeus).

They function in close connection with the X-pair - vagus nerves ( n. vagus) . These nerves have a number of common nuclei in the medulla oblongata, performing sensory, motor and secretory functions. They innervate the soft palate, pharynx, upper esophagus, parotid salivary gland, posterior third of the tongue. The vagus nerve carries out parasympathetic innervation of all internal organs up to the level of the pelvis.

XI pair - accessory nerves ( n. accessorius) . Innervate the sternocleidomastoid and trapezius muscles.

XII pair - hypoglossal nerves ( n. hypoglossus) . Innervate the muscles of the tongue.

Vegetative department of the human nervous system: structure and main functions

Autonomic nervous system (ANS) It is the part of the nervous system that keeps the body alive. It innervates the heart, blood vessels, internal organs, and also provides tissue trophism, ensures the constancy of the internal environment of the body. In the autonomic nervous system, there are sympathetic and parasympathetic parts. They interact as antagonists and synergists. Thus, the sympathetic nervous system dilates the pupil, increases the heart rate, constricts blood vessels, increases blood pressure, reduces the secretion of glands, slows down the peristalsis of the stomach and intestines, and reduces sphincters. Parasympathetic, on the contrary, constricts the pupil, slows down the heartbeat, dilates blood vessels, lowers blood pressure, increases the secretion of glands and intestinal motility, and relaxes the sphincters.

The sympathetic autonomic nervous system performs a trophic function, enhances oxidative processes, nutrient intake, respiratory and cardiovascular activity, and changes the permeability of the cell membrane. The role of the parasympathetic system is protective. At rest, the vital activity of the body is provided by the parasympathetic system, while under tension - by the sympathetic system.

In the structure of the autonomic nervous system, segmental and suprasegmental sections are distinguished.

The segmental part of the ANS is represented by sympathetic and parasympathetic formations at the spinal and stem levels.

The centers of the human sympathetic autonomic nervous system are located in the lateral columns of the spinal cord at the C8-L3 level. Sympathetic fibers exit the spinal cord with anterior roots, interrupt at the nodes of the paired sympathetic trunk, which is located on the anterior surface of the spinal column and consists of 20-25 pairs of nodes, containing sympathetic cells. Fibers depart from the nodes of the sympathetic trunk, forming sympathetic plexuses and nerves, which are directed to organs and vessels.

The centers of the parasympathetic nervous system are located in the brainstem and in the sacral segments S2-S4 of the spinal cord. The processes of the cells of the parasympathetic nuclei of the brain stem as part of the oculomotor, facial, glossopharyngeal and vagus nerves provide innervation of the glands and smooth muscles of all internal organs, with the exception of the pelvic organs. The fibers of the cells of the parasympathetic nuclei of the sacral segments form the pelvic splanchnic nerves leading to the bladder, rectum, and genitals.

Both sympathetic and parasympathetic fibers are interrupted in the peripheral vegetative nodes located near the innervated organs or in their walls.

The fibers of the autonomic nervous system form a number of plexuses: solar, pericardial, mesenteric, pelvic, which innervate the internal organs and regulate their function.

The higher suprasegmental division of the autonomic nervous system includes the nuclei of the hypothalamus, the limbic-reticular complex, the basal structures of the temporal lobe, and some sections of the associative zone of the cerebral cortex. The role of these formations is to integrate the basic mental and somatic functions.

At rest, the vital activity of the body is provided by the parasympathetic system, while under tension, the sympathetic system.

The centers of the sympathetic nervous system are located in the lateral columns of the spinal cord at the level of C8-L3; sympathetic fibers exit the spinal cord with anterior roots, interrupted at the nodes of the paired sympathetic trunk.

Here you can watch the video "Human Nervous System" to better understand how it works:

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The nervous system controls the activity of all systems and organs and ensures the connection of the body with the external environment.

The structure of the nervous system

The structural unit of the nervous system is the neuron - a nerve cell with processes. In general, the structure of the nervous system is a collection of neurons that are constantly in contact with each other using special mechanisms - synapses. The following types of neurons differ in function and structure:

• Sensitive or receptor;
• Effector - motor neurons that send an impulse to the executive organs (effectors);
• Closing or plug-in (conductor).

Conventionally, the structure of the nervous system can be divided into two large sections - somatic (or animal) and vegetative (or autonomous). The somatic system is primarily responsible for the connection of the body with the external environment, providing movement, sensitivity and contraction of skeletal muscles. The vegetative system affects the growth processes (respiration, metabolism, excretion, etc.). Both systems have a very close relationship, only the autonomic nervous system is more independent and does not depend on the will of a person. That is why it is also called autonomous. The autonomous system is divided into sympathetic and parasympathetic.

The entire nervous system consists of the central and peripheral. The central part includes the spinal cord and brain, and the peripheral system represents the outgoing nerve fibers from the brain and spinal cord. If you look at the brain in section, you can see that it consists of white and gray matter.

Gray matter is an accumulation of nerve cells (with the initial sections of processes extending from their bodies). Separate groups of gray matter are also called nuclei.

White matter consists of nerve fibers covered with myelin sheath (processes of nerve cells from which gray matter is formed). In the spinal cord and brain, nerve fibers form pathways.

Peripheral nerves are divided into motor, sensory and mixed, depending on what fibers they consist of (motor or sensory). The bodies of neurons, whose processes are made up of sensory nerves, are located in ganglions outside the brain. The bodies of motor neurons are located in the motor nuclei of the brain and the anterior horns of the spinal cord.

Functions of the nervous system

The nervous system has different effects on the organs. The three main functions of the nervous system are:

• Starting, causing or stopping the function of an organ (secretion of the gland, muscle contraction, etc.);
• Vasomotor, which allows you to change the width of the lumen of the vessels, thereby regulating the flow of blood to the organ;
• Trophic, lowering or increasing metabolism, and, consequently, the consumption of oxygen and nutrients. This allows you to constantly coordinate the functional state of the body and its need for oxygen and nutrients. When impulses are sent along the motor fibers to the working skeletal muscle, causing its contraction, then impulses are simultaneously received that increase metabolism and dilate blood vessels, which makes it possible to provide the energy for performing muscle work.

Diseases of the nervous system

Together with the endocrine glands, the nervous system plays a crucial role in the functioning of the body. It is responsible for the coordinated work of all systems and organs of the human body and unites the spinal cord, brain and peripheral system. Motor activity and sensitivity of the body is supported by nerve endings. And thanks to the autonomic system, the cardiovascular system and other organs are inverted.

Therefore, a violation of the functions of the nervous system affects the work of all systems and organs.

All diseases of the nervous system can be divided into infectious, hereditary, vascular, traumatic and chronically progressive.

Hereditary diseases are genomic and chromosomal. The most famous and common chromosomal disease is Down's disease. This disease is characterized by the following symptoms: a violation of the musculoskeletal system, the endocrine system, lack of mental abilities.

Traumatic lesions of the nervous system occur due to bruises and injuries, or when squeezing the brain or spinal cord. Such diseases are usually accompanied by vomiting, nausea, memory loss, disorders of consciousness, loss of sensitivity.

Vascular diseases mainly develop against the background of atherosclerosis or hypertension. This category includes chronic cerebrovascular insufficiency, cerebrovascular accident. Characterized by the following symptoms: attacks of vomiting and nausea, headache, impaired motor activity, decreased sensitivity.

Chronically progressive diseases, as a rule, develop as a result of metabolic disorders, exposure to infection, intoxication of the body, or due to abnormalities in the structure of the nervous system. Such diseases include sclerosis, myasthenia, etc. These diseases usually progress gradually, reducing the efficiency of some systems and organs.

Causes of diseases of the nervous system:

The placental route of transmission of diseases of the nervous system during pregnancy (cytomegalovirus, rubella), as well as through the peripheral system (poliomyelitis, rabies, herpes, meningoencephalitis) is also possible.

In addition, the nervous system is negatively affected by endocrine, heart, kidney diseases, malnutrition, chemicals and drugs, heavy metals.

All organs and systems of the human body are closely interconnected, they interact with the help of the nervous system, which regulates all the mechanisms of life, from digestion to the process of reproduction. It is known that a person (NS) provides a connection between the human body and the external environment. The unit of the NS is the neuron, which is a nerve cell that conducts impulses to other cells of the body. Connecting into neural circuits, they form a whole system, both somatic and vegetative.

It can be said that the NS is plastic, as it is able to restructure its work in the event that changes occur in the needs of the human body. This mechanism is especially relevant when one of the parts of the brain is damaged.

Since the human nervous system coordinates the work of all organs, its damage affects the activity of both nearby and distant structures, and is accompanied by the failure of the functions of organs, tissues and body systems. The causes of disruption of the nervous system may lie in the presence of infections or poisoning of the body, in the occurrence of a tumor or injury, in diseases of the National Assembly and metabolic disorders.

Thus, the human NS plays a conducting role in the formation and development of the human body. Thanks to the evolutionary improvement of the nervous system, the human psyche and consciousness developed. The nervous system is a vital mechanism for regulating the processes that occur in the human body.

This section will describe common diseases of the human nervous system. But, first, let us briefly recall the composition and functions of the human nervous system.

The human nervous system is a collection of receptors, nerves, ganglia, brain. The nervous system perceives stimuli acting on the body, conducts and processes the resulting excitation, and forms adaptive responses. The nervous system also regulates and coordinates all the functions of the body in its interaction with the external environment.

The functional unit of the human nervous system is neuron is the longest cell in our body. The length of a neuron reaches one and a half meters, and the life expectancy can be the same as the life of the whole organism. The human nervous system has up to 15 billion neurons - this is a huge figure. The total length of all the neurons of one person is approximately equal to the distance from the Earth to the Moon.

A neuron consists of a body and processes:

• axon- a non-branching process that conducts nerve impulses from the cell body to the muscles and glands;
• dendrites- branching processes that transmit nerve impulses to other neurons.

The central organ of the nervous system is brain- the most "gluttonous" organ of the human body, since with a weight of about 1.5 kg it consumes up to 20% of all oxygen circulating in the blood.

The brain consists of two hemispheres - left and right. Moreover, the left hemisphere is responsible for the work of the organs of the right half of our body, and the right - for the work of the left half.

The surface area of ​​the cerebral cortex is covered with multiple furrows and convolutions, which greatly increase its surface area. Certain areas of the brain are responsible for certain abilities: to speak, see, hear ... 12 pairs of cranial nerves and many nerve conductors depart from the brain, which carry out a "dialogue" of the brain with tissues and muscles of the whole organism.

With the help of the brain stem, the brain connects to the spinal cord, from which 31 pairs of spinal nerves depart, covering our entire body.

Some muscles of our body work outside of our consciousness, as if "by themselves" - this is the heart muscle, pulmonary muscles. The work of these muscles is regulated autonomic nervous system which is part of the sympathetic and parasympathetic nervous systems.

Sympathetic nervous system consists of two chains of nerve nodes (ganglia), which are located along the spine and regulate the functioning of internal organs: stomach, heart, intestines.

Center parasympathetic system located in the upper part of the spinal cord, and the nerve nodes - directly in the internal organs.

ATTENTION! The information provided on this site is for reference only. Only a specialist in a particular field can make a diagnosis and prescribe treatment.