There are the following methods for studying the functions of the central nervous system:

1. method cutting brain stem at various levels. For example, between the medulla oblongata and the spinal cord;

2. method extirpation(deletion) or destruction areas of the brain;

3. method irritation various parts and centers of the brain;

4. anatomical-clinical method. Clinical observations of changes in the functions of the central nervous system when any of its parts are damaged, followed by a pathological examination;

5. electrophysiological methods:

A. electroencephalography– registration of brain biopotentials from the surface of the scalp. The technique was developed and introduced into the clinic by G. Berger;

b. registration biopotentials various nerve centers; used in conjunction with the stereotactic technique, in which electrodes are inserted into a strictly defined nucleus using micromanipulators;

V. method evoked potentials, recording the electrical activity of areas of the brain during electrical stimulation of peripheral receptors or other areas.

6. method of intracerebral administration of substances using microinophoresis;

7. chronoreflexometry– determination of reflex time.

Properties of nerve centers

Nerve center(NC) is a collection of neurons in various parts of the central nervous system that provide regulation of any function of the body. For example, the bulbar respiratory center.

The following features are characteristic for the conduction of excitation through nerve centers:

1. Unilateral conduction. It goes from the afferent, through the intercalary, to the efferent neuron. This is due to the presence of interneuron synapses.

2. Central delay carrying out excitation. Those. Excitation along the NC is much slower than along the nerve fiber. This is explained by synaptic delay. Since there are most synapses in the central link of the reflex arc, the conduction speed there is the lowest. Based on this, reflex time – This is the time from the onset of exposure to a stimulus to the appearance of a response. The longer the central delay, the longer the reflex time. However, it depends on the strength of the stimulus. The larger it is, the shorter the reflex time and vice versa. This is explained by the phenomenon of summation of excitations in synapses. In addition, it is determined by the functional state of the central nervous system. For example, when the NC is tired, the duration of the reflex reaction increases.

3. Spatial and temporal summation. Time summation arises, as in synapses, due to the fact that the more nerve impulses are received, the more neurotransmitter is released in them, the higher the amplitude of excitation of postsynaptic potentials (EPSP). Therefore, a reflex reaction can occur to several successive subthreshold stimuli. Spatial summation observed when impulses from several receptor neurons go to the nerve center. When subthreshold stimuli act on them, the resulting postsynaptic potentials are summed up and a propagating AP is generated in the neuron membrane.

4. Rhythm transformation excitation - a change in the frequency of nerve impulses as they pass through the nerve center. The frequency may decrease or increase. For example, enhancing transformation(increase in frequency) due to dispersion And animation excitations in neurons. The first phenomenon occurs as a result of the division of nerve impulses into several neurons, the axons of which then form synapses on one neuron. The second is the generation of several nerve impulses during the development of an excitatory postsynaptic potential on the membrane of one neuron. Downward Transformation is explained by the summation of several EPSPs and the occurrence of one AP in the neuron.

5. Postetanic potentiation– this is an increase in the reflex reaction as a result of prolonged excitation of the neurons of the center. Under the influence of many series of nerve impulses passing at high frequency through synapses, a large amount of neurotransmitter is released at interneuron synapses. This leads to a progressive increase in the amplitude of the excitatory postsynaptic potential and long-term (several hours) excitation of neurons.

6. Aftereffect- this is a delay in the end of the reflex response after the cessation of the stimulus. Associated with the circulation of nerve impulses along closed circuits of neurons.

7. Tone of nerve centers– a state of constant increased activity. It is caused by the constant supply of nerve impulses to the NC from peripheral receptors, the stimulating influence of metabolic products and other humoral factors on neurons. For example, the manifestation of the tone of the corresponding centers is the tone of a certain muscle group.

8. Automatic(spontaneous activity) of nerve centers. Periodic or constant generation of nerve impulses by neurons that arise spontaneously in them, i.e. in the absence of signals from other neurons or receptors. It is caused by fluctuations in metabolic processes in neurons and the effect of humoral factors on them.

9. Plastic nerve centers. This is their ability to change functional properties. In this case, the center acquires the ability to perform new functions or restore old ones after damage. The plasticity of NCs is based on the plasticity of synapses and membranes of neurons, which can change their molecular structure.

10. Low physiological lability And fast fatiguability. NCs can conduct pulses of only a limited frequency. Their fatigue is explained by fatigue of synapses and deterioration of neuronal metabolism.

Inhibition in the central nervous system

Phenomenon central braking discovered by I.M. Sechenov in 1862. He removed the frog's brain hemispheres and determined the time of the spinal reflex to irritation of the paw with sulfuric acid. Then a crystal of table salt was placed on the thalamus (visual tubercles) and found that the reflex time increased significantly. This indicated inhibition of the reflex. Sechenov concluded that the overlying NCs, when excited, inhibit the underlying ones. Inhibition in the central nervous system prevents the development of excitation or weakens ongoing excitation. An example of inhibition could be the cessation of a reflex reaction against the background of the action of another, stronger stimulus.

Was originally proposed unitary chemical theory of inhibition. It was based on Dale's principle: one neuron - one transmitter. According to it, inhibition is provided by the same neurons and synapses as excitation. It was subsequently proven correct binary chemical theory. In accordance with the latter, inhibition is provided by special inhibitory neurons, which are intercalary. These are Renshaw cells of the spinal cord and Purkinje neurons. Inhibition in the central nervous system is necessary for the integration of neurons into a single nerve center.

The following are distinguished in the central nervous system: braking mechanisms:

1. Postsynaptic. It occurs in the postsynaptic membrane of the soma and dendrites of neurons, i.e. after the transmitting synapse. In these areas, specialized inhibitory neurons form axo-dendritic or axo-somatic synapses. These synapses are glycinergic. As a result of the effect of glycine on glycine chemoreceptors of the postsynaptic membrane, its potassium and chloride channels open. Potassium and chloride ions enter the neuron, and inhibition of postsynaptic potentials (IPSPs) develops. The role of chlorine ions in the development of IPSP is small. As a result of the resulting hyperpolarization, the excitability of the neuron decreases. The conduction of nerve impulses through it stops. Alkaloid strychnine can bind to glycine receptors on the postsynaptic membrane and turn off inhibitory synapses. This is used to demonstrate the role of inhibition. After the administration of strychnine, the animal develops cramps in all muscles.

2. Presynaptic braking. In this case, the inhibitory neuron forms a synapse on the axon of the neuron that approaches the transmitting synapse. Those. such a synapse is axo-axonal. The mediator of these synapses is GABA. Under the influence of GABA, chloride channels of the postsynaptic membrane are activated. But in this case, chlorine ions begin to leave the axon. This leads to a small local but long-lasting depolarization of its membrane. A significant part of the sodium channels of the membrane is inactivated, which blocks the conduction of nerve impulses along the axon, and consequently the release of the neurotransmitter at the transmitting synapse. The closer the inhibitory synapse is located to the axon hillock, the stronger its inhibitory effect. Presynaptic inhibition is most effective in information processing, since the conduction of excitation is not blocked in the entire neuron, but only at its one input. Other synapses located on the neuron continue to function.

3. Pessimal braking. Discovered by N.E. Vvedensky. Occurs at a very high frequency of nerve impulses. A persistent, long-term depolarization of the entire neuron membrane and inactivation of its sodium channels develops. The neuron becomes unexcitable.

Both inhibitory and excitatory postsynaptic potentials can simultaneously arise in a neuron. Due to this, the necessary signals are isolated.

Methods for studying the nervous system

The main methods for studying the central nervous system and the neuromuscular system are electroencephalography (EEG), rheoencephalography (REG), electromyography (EMG), which determine static stability, muscle tone, tendon reflexes, etc.

Electroencephalography (EEG) - a method for recording electrical activity (biocurrents) of brain tissue for the purpose of objective assessment of the functional state of the brain. It is of great importance for diagnosing brain injury, vascular and inflammatory diseases of the brain, as well as for monitoring the functional state of an athlete, identifying early forms of neuroses, for treatment and for selection into sports sections (especially boxing, karate and other sports related with blows to the head).
When analyzing data obtained both at rest and under functional loads, various external influences in the form of light, sound, etc.), the amplitude of the waves, their frequency and rhythm are taken into account. In a healthy person, alpha waves predominate (oscillation frequency 8-12 per 1 s), recorded only when the subject’s eyes are closed. In the presence of afferent light impulses with open eyes, the alpha rhythm completely disappears and is restored again when the eyes are closed. This phenomenon is called the fundamental rhythm activation reaction. Normally it should be registered.
In 35-40% of people in the right hemisphere, the amplitude of alpha waves is slightly higher than in the left, and there is also some difference in the frequency of oscillations - by 0.5-1 oscillations per second.
With head injuries, the alpha rhythm is absent, but oscillations of high frequency and amplitude and slow waves appear.
In addition, the EEG method can diagnose early signs of neuroses (overwork, overtraining) in athletes.

Rheoencephalography (REG) - a method for studying cerebral blood flow, based on recording rhythmic changes in the electrical resistance of brain tissue due to pulse fluctuations in the blood supply of blood vessels.
The rheoencephalogram consists of repeating waves and teeth. When assessing it, the characteristics of the teeth, the amplitude of the rheographic (systolic) waves, etc. are taken into account.
The state of vascular tone can also be judged by the steepness of the ascending phase. Pathological indicators are deepening of the incisura and an increase in the dicrotic tooth with a shift downward along the descending part of the curve, which characterizes a decrease in the tone of the vessel wall.
The REG method is used in the diagnosis of chronic disorders of cerebral circulation, vegetative-vascular dystonia, headaches and other changes in the blood vessels of the brain, as well as in the diagnosis of pathological processes resulting from injuries, concussions and diseases that secondary affect blood circulation in the cerebral vessels (cervical osteochondrosis , aneurysms, etc.).

Electromyography (EMG) - a method for studying the functioning of skeletal muscles by recording their electrical activity - biocurrents, biopotentials. Electromyographs are used to record EMG. The removal of muscle biopotentials is carried out using surface (overhead) or needle-shaped (injected) electrodes. When studying the muscles of the limbs, electromyograms are most often recorded from the muscles of the same name on both sides. First, resting EM is recorded with the entire muscle in the most relaxed state, and then with its tonic tension.
Using EMG, it is possible to determine at an early stage (and prevent the occurrence of muscle and tendon injuries) changes in muscle biopotentials, to judge the functional capacity of the neuromuscular system, especially the muscles most loaded in training. Using EMG, in combination with biochemical studies (determination of histamine, urea in the blood), early signs of neuroses (overfatigue, overtraining) can be determined. In addition, multiple myography determines the work of muscles in the motor cycle (for example, in rowers, boxers during testing). EMG characterizes muscle activity, the state of the peripheral and central motor neuron.
EMG analysis is given by amplitude, shape, rhythm, frequency of potential oscillations and other parameters. In addition, when analyzing EMG, the latent period between the signal for muscle contraction and the appearance of the first oscillations on the EMG and the latent period for the disappearance of oscillations after the command to stop contractions are determined.

Chronaximetry - a method for studying the excitability of nerves depending on the time of action of the stimulus. First, the rheobase is determined - the current strength that causes the threshold contraction, and then the chronaxy. Chronancy is the minimum time for a current of two rheobases to pass, which gives the minimum reduction. Chronaxy is calculated in sigmas (thousandths of a second).
Normally, the chronaxy of various muscles is 0.0001-0.001 s. It has been established that proximal muscles have less chronaxy than distal ones. The muscle and the nerve that innervates it have the same chronaxy (isochronism). Synergistic muscles also have the same chronaxy. On the upper limbs, the chronaxy of the flexor muscles is two times less than the chronaxy of the extensor muscles; on the lower limbs, the opposite ratio is observed.
In athletes, muscle chronaxy sharply decreases and the difference in chronaxy (anisochronaxy) of flexors and extensors may increase due to overtraining (overfatigue), myositis, paratenonitis of the gastrocnemius muscle, etc.

Stability in static position can be studied using stabilography, tremorography, Romberg test, etc.
Romberg test reveals imbalance in a standing position. Maintaining normal coordination of movements occurs due to the joint activity of several parts of the central nervous system. These include the cerebellum, vestibular apparatus, conductors of deep muscle sensitivity, and the cortex of the frontal and temporal regions. The central organ for coordinating movements is the cerebellum. The Romberg test is carried out in four modes with a gradual decrease in the support area. In all cases, the subject's hands are raised forward, fingers spread and eyes closed. “Very good” if in each pose the athlete maintains balance for 15 seconds and there is no body swaying, trembling of the hands or eyelids (tremor). For tremor, a “satisfactory” rating is given. If the balance is disturbed within 15 s, the test is assessed as “unsatisfactory”. This test is of practical use in acrobatics, gymnastics, trampolining, figure skating and other sports where coordination is important.

Determination of balance in static poses
Regular training helps improve coordination of movements. In a number of sports (acrobatics, artistic gymnastics, diving, figure skating, etc.) this method is an informative indicator in assessing the functional state of the central nervous system and neuromuscular system. With overwork, head injury and other conditions, these indicators change significantly.
Yarotsky test allows you to determine the sensitivity threshold of the vestibular analyzer. The test is performed in the initial standing position with eyes closed, while the athlete, on command, begins rotational movements of the head at a fast pace. The time of head rotation until the athlete loses balance is recorded. In healthy individuals, the time to maintain balance is on average 28 s, in trained athletes - 90 s or more. The sensitivity level threshold of the vestibular analyzer mainly depends on heredity, but under the influence of training it can be increased.
Finger-nose test. The subject is asked to touch the tip of his nose with his index finger with his eyes open and then with his eyes closed. Normally, there is a hit, touching the tip of the nose. In case of brain injuries, neuroses (overwork, overtraining) and other functional conditions, there is a miss (miss), trembling (tremor) of the index finger or hand.
Tapping test determines the maximum frequency of hand movements.
To carry out the test, you must have a stopwatch, a pencil and a sheet of paper, which is divided into four equal parts by two lines. Dots are placed in the first square for 10 seconds at maximum speed, then a 10-second rest period and the procedure is repeated again from the second square to the third and fourth. The total duration of the test is 40 s. To evaluate the test, count the number of dots in each square. Trained athletes have a maximum frequency of wrist movements of more than 70 in 10 seconds. A decrease in the number of points from square to square indicates insufficient stability of the motor sphere and nervous system. The decrease in the lability of nervous processes occurs in steps (with an increase in the frequency of movements in the 2nd or 3rd squares) - indicating a slowdown in the processes of processing. This test is used in acrobatics, fencing, gaming and other sports.

Nervous system research, analyzers.
Kinesthetic sensitivity is examined with a hand dynamometer. First, the maximum force is determined. Then the athlete, looking at the dynamometer, squeezes it 3-4 times with a force equal to, for example, 50% of the maximum. Then this effort is repeated 3-5 times (pauses between repetitions are 30 s), without visual control. Kinesthetic sensitivity is measured by the deviation from the obtained value (in percent). If the difference between the given and actual effort does not exceed 20%, kinesthetic sensitivity is assessed as normal.

Muscle tone study.
Muscle tone is a certain degree of normally observed muscle tension, which is maintained reflexively. The afferent part of the reflex arc is formed by conductors of muscle-articular sensitivity, carrying impulses from proprioceptors of muscles, joints and tendons to the spinal cord. The efferent part is the peripheral motor neuron. In addition, the cerebellum and extrapyramidal system are involved in the regulation of muscle tone. Muscle tone is determined by V.I. tonometer. Dubrovsky and E.I. Deryabina (1973) in a calm state (plastic tone) and tension (contractile tone).
An increase in muscle tone is called muscle hypertension (hypertonicity), no change is called atony, a decrease is called hypotension.
An increase in muscle tone is observed with fatigue (especially chronic), with injuries and diseases of the musculoskeletal system (MSA) and other functional disorders. A decrease in tone is observed with prolonged rest, lack of training in athletes, after removal of plaster casts, etc.

Reflex Research .
Reflex is the basis of the activity of the entire nervous system. Reflexes are divided into unconditioned (innate reactions of the body to various exteroceptive and interoceptive stimuli) and conditioned (new temporary connections developed on the basis of unconditioned reflexes as a result of the individual experience of each person).
Depending on the site of evocation of the reflex (reflexogenic zone), all unconditioned reflexes can be divided into superficial, deep, distant and reflexes of internal organs. In turn, superficial reflexes are divided into cutaneous and mucous membranes; deep - tendon, periosteal and articular; distant - for light, auditory and olfactory.
When examining abdominal reflexes, to completely relax the abdominal wall, the athlete needs to bend his legs at the knee joints. Using a blunt needle or goose feather, the doctor makes a line irritation 3-4 fingers above the navel parallel to the costal arch. Normally, contraction of the abdominal muscles on the corresponding side is observed.
When examining the plantar reflex, the doctor stimulates along the inner or outer edge of the sole. Normally, there is flexion of the toes.
Deep reflexes (knee, Achilles tendon, biceps, triceps) are among the most constant. The knee reflex is caused by striking the quadriceps tendon below the kneecap with a hammer; Achilles reflex - hitting the Achilles tendon with a hammer; the triceps reflex is caused by a blow to the triceps tendon above the olecranon; biceps reflex - with a blow to the tendon in the elbow bend. The blow with a hammer is applied abruptly, evenly, precisely on a given tendon.
With chronic fatigue, athletes experience a decrease in tendon reflexes, and with neuroses - an increase. With osteochondrosis, lumbosacral radiculitis, neuritis and other diseases, a decrease or disappearance of reflexes is observed.

Studies of visual acuity, color perception, visual field.
Visual acuity is examined using tables located at a distance of 5 m from the subject. If he distinguishes 10 rows of letters on the table, then visual acuity is equal to one, but if only large letters, the 1st row, are distinguished, then visual acuity is 0.1, etc. d. Visual acuity is of great importance when selecting for sports.
So, for example, for divers, weightlifters, boxers, wrestlers with vision of -5 and below, sports are contraindicated!
Color perception is studied using a set of colored strips of paper. With injuries (lesions) to the subcortical visual centers and partially or completely to the cortical zone, color recognition is impaired, most often red and green. If color vision is impaired, auto and cycling and many other sports are contraindicated.
The field of view is determined by the perimeter. This is a metal arc attached to a stand and rotating around a horizontal axis. The inner surface of the arc is divided into degrees (from zero at the center to 90°). The number of degrees marked on the arc shows the boundary of the field of view. The boundaries of the normal field of vision for white color: internal - 60°; lower - 70°; upper - 60°. 90° indicates deviations from the norm.
Evaluation of the visual analyzer is important in team sports, acrobatics, artistic gymnastics, trampolining, fencing, etc.
Hearing examination. Hearing acuity is examined at a distance of 5 m. The doctor pronounces the words in a whisper and offers to repeat them. In case of injury or illness, hearing loss is observed (auditory neuritis). Most often observed in boxers, water polo players, shooters, etc.
Research of analyzers. A complex functional system consisting of a receptor, an afferent pathway and a zone of the cerebral cortex where this type of sensitivity is projected is referred to as an analyzer.
The central nervous system (CNS) receives information about the external world and the internal state of the body from reception organs specialized in the perception of irritations. Many reception organs are called sense organs, because as a result of their irritation and the receipt of impulses from them in the cerebral hemispheres, sensations, perceptions, ideas arise, that is, various forms of sensory reflection of the external world.
As a result of information from receptors entering the central nervous system, various acts of behavior arise and general mental activity is built.

The basic principle of the functioning of the central nervous system is the process of regulation, control of physiological functions, which are aimed at maintaining the constancy of the properties and composition of the internal environment of the body. The central nervous system ensures optimal relationships between the body and the environment, stability, integrity, and the optimal level of vital activity of the body.

There are two main types of regulation: humoral and nervous.

The humoral control process involves changing the physiological activity of the body under the influence of chemicals that are delivered by body fluids. The source of information transfer is chemicals - utilizons, metabolic products (carbon dioxide, glucose, fatty acids), informons, hormones of the endocrine glands, local or tissue hormones.

The nervous process of regulation involves controlling changes in physiological functions along nerve fibers using excitation potential under the influence of information transfer.

Characteristics:

1) is a later product of evolution;

2) provides quick regulation;

3) has an exact target of impact;

4) implements an economical method of regulation;

5) ensures high reliability of information transmission.

In the body, the nervous and humoral mechanisms work as a single system of neurohumoral control. This is a combined form, where two control mechanisms are used simultaneously; they are interconnected and interdependent.

The nervous system is a collection of nerve cells, or neurons.

According to localization they distinguish:

1) central section – brain and spinal cord;

2) peripheral - processes of nerve cells of the brain and spinal cord.

According to functional features they are distinguished:

1) somatic department, regulating motor activity;

2) vegetative, regulating the activity of internal organs, endocrine glands, blood vessels, trophic innervation of muscles and the central nervous system itself.

Functions of the nervous system:

1) integrative-coordination function. Provides the functions of various organs and physiological systems, coordinates their activities with each other;

2) ensuring close connections between the human body and the environment at the biological and social levels;

3) regulation of the level of metabolic processes in various organs and tissues, as well as in oneself;

4) ensuring mental activity by the higher departments of the central nervous system.

2. Neuron. Structural features, meaning, types

The structural and functional unit of nervous tissue is the nerve cell - neuron.

A neuron is a specialized cell that is capable of receiving, encoding, transmitting and storing information, establishing contacts with other neurons, and organizing the body’s response to irritation.

Functionally, a neuron is divided into:

1) the receptive part (dendrites and membrane of the soma of the neuron);

2) integrative part (soma with axon hillock);

3) transmitting part (axon hillock with axon).

Perceiving part.

Dendrites– the main receptive field of the neuron. The dendrite membrane is capable of responding to mediators. A neuron has several branching dendrites. This is explained by the fact that a neuron as an information formation must have a large number of inputs. Through specialized contacts, information flows from one neuron to another. These contacts are called "spines".

The neuron soma membrane is 6 nm thick and consists of two layers of lipid molecules. The hydrophilic ends of these molecules face the water phase: one layer of molecules faces inward, the other outward. The hydrophilic ends are turned towards each other - inside the membrane. The lipid bilayer of the membrane contains proteins that perform several functions:

1) pump proteins - move ions and molecules in the cell against a concentration gradient;

2) proteins embedded in the channels provide selective membrane permeability;

3) receptor proteins recognize the necessary molecules and fix them on the membrane;

4) enzymes facilitate the occurrence of a chemical reaction on the surface of the neuron.

In some cases, the same protein can serve as both a receptor, an enzyme, and a pump.

Integrative part.

Axon hillock– the point where the axon exits the neuron.

The neuron soma (neuron body) performs, along with an informational and trophic function, relative to its processes and synapses. The soma ensures the growth of dendrites and axons. The neuron soma is enclosed in a multilayer membrane, which ensures the formation and propagation of electrotonic potential to the axon hillock.

Transmitting part.

Axon- an outgrowth of the cytoplasm, adapted to carry information that is collected by dendrites and processed in the neuron. The axon of a dendritic cell has a constant diameter and is covered with a myelin sheath, which is formed from glia; the axon has branched endings containing mitochondria and secretory formations.

Functions of neurons:

1) generalization of the nerve impulse;

2) receiving, storing and transmitting information;

3) the ability to summarize excitatory and inhibitory signals (integrative function).

Types of neurons:

1) by localization:

a) central (brain and spinal cord);

b) peripheral (cerebral ganglia, cranial nerves);

2) depending on the function:

a) afferent (sensitive), carrying information from receptors to the central nervous system;

b) intercalary (connector), in the elementary case providing communication between afferent and efferent neurons;

c) efferent:

– motor – anterior horns of the spinal cord;

– secretory – lateral horns of the spinal cord;

3) depending on the functions:

a) stimulating;

b) inhibitory;

4) depending on the biochemical characteristics, on the nature of the mediator;

5) depending on the quality of the stimulus that is perceived by the neuron:

a) monomodal;

b) multimodal.

3. Reflex arc, its components, types, functions

The activity of the body is a natural reflex reaction to a stimulus. Reflex– the body’s reaction to irritation of receptors, which is carried out with the participation of the central nervous system. The structural basis of the reflex is the reflex arc.

Reflex arc- a series-connected chain of nerve cells that ensures the implementation of a reaction, a response to irritation.

The reflex arc consists of six components: receptors, afferent (sensitive) path, reflex center, efferent (motor, secretory) path, effector (working organ), feedback.

Reflex arcs can be of two types:

1) simple - monosynaptic reflex arcs (reflex arc of the tendon reflex), consisting of 2 neurons (receptor (afferent) and effector), there is 1 synapse between them;

2) complex – polysynaptic reflex arcs. They consist of 3 neurons (there may be more) - a receptor, one or more intercalary and an effector.

The idea of ​​the reflex arc as an expedient response of the body dictates the need to supplement the reflex arc with another link - a feedback loop. This component establishes a connection between the realized result of the reflex reaction and the nerve center that issues executive commands. With the help of this component, the open reflex arc is transformed into a closed one.

Features of a simple monosynaptic reflex arc:

1) geographically close receptor and effector;

2) reflex arc two-neuron, monosynaptic;

3) nerve fibers of group A? (70-120 m/s);

4) short reflex time;

5) muscles contracting according to the type of single muscle contraction.

Features of a complex monosynaptic reflex arc:

1) territorially separated receptor and effector;

2) three-neuron receptor arch (there may be more neurons);

3) the presence of nerve fibers of groups C and B;

4) muscle contraction according to the tetanus type.

Features of the autonomic reflex:

1) the interneuron is located in the lateral horns;

2) the preganglionic nerve pathway begins from the lateral horns, after the ganglion - the postganglionic;

3) the efferent path of the autonomic nervous arch reflex is interrupted by the autonomic ganglion, in which the efferent neuron lies.

The difference between the sympathetic nervous arch and the parasympathetic: the sympathetic nervous arch has a short preganglionic pathway, since the autonomic ganglion lies closer to the spinal cord, and the postganglionic pathway is long.

In the parasympathetic arc, the opposite is true: the preganglionic pathway is long, since the ganglion lies close to the organ or in the organ itself, and the postganglionic pathway is short.

4. Functional systems of the body

Functional system– temporary functional unification of the nerve centers of various organs and systems of the body to achieve a final beneficial result.

The beneficial result is a self-forming factor of the nervous system. The result of an action is a vital adaptive indicator that is necessary for the normal functioning of the body.

There are several groups of final useful results:

1) metabolic – a consequence of metabolic processes at the molecular level that create substances and end products necessary for life;

2) homeostatic – constancy of indicators of the state and composition of the body’s media;

3) behavioral – the result of biological needs (sexual, food, drinking);

4) social – satisfaction of social and spiritual needs.

The functional system includes various organs and systems, each of which takes an active part in achieving a useful result.

The functional system, according to P.K. Anokhin, includes five main components:

1) a useful adaptive result - that for which a functional system is created;

2) control apparatus (result acceptor) – a group of nerve cells in which a model of the future result is formed;

3) reverse afferentation (supplies information from the receptor to the central link of the functional system) - secondary afferent nerve impulses that go to the acceptor of the result of the action to evaluate the final result;

4) control apparatus (central link) – functional association of nerve centers with the endocrine system;

5) executive components (reaction apparatus) - these are the organs and physiological systems of the body (vegetative, endocrine, somatic). Consists of four components:

a) internal organs;

b) endocrine glands;

c) skeletal muscles;

d) behavioral reactions.

Properties of a functional system:

1) dynamism. The functional system may include additional organs and systems, which depends on the complexity of the current situation;

2) the ability to self-regulate. When the controlled value or the final useful result deviates from the optimal value, a series of reactions of a spontaneous complex occur, which returns the indicators to the optimal level. Self-regulation occurs in the presence of feedback.

Several functional systems operate simultaneously in the body. They are in continuous interaction, which is subject to certain principles:

1) the principle of the system of genesis. Selective maturation and evolution of functional systems occur (functional circulatory, respiratory, nutritional systems mature and develop earlier than others);

2) the principle of multiply connected interaction. There is a generalization of the activities of various functional systems aimed at achieving a multicomponent result (homeostasis parameters);

3) the principle of hierarchy. Functional systems are arranged in a certain row in accordance with their significance (functional system of tissue integrity, functional nutrition system, functional reproduction system, etc.);

4) the principle of sequential dynamic interaction. There is a clear sequence of changing the activities of one functional system to another.

5. Coordination activities of the central nervous system

Coordination activity (CA) of the CNS is the coordinated work of CNS neurons, based on the interaction of neurons with each other.

CD functions:

1) ensures clear performance of certain functions and reflexes;

2) ensures the consistent inclusion of various nerve centers in the work to ensure complex forms of activity;

3) ensures the coordinated work of various nerve centers (during the act of swallowing, the breath is held at the moment of swallowing; when the swallowing center is excited, the breathing center is inhibited).

Basic principles of CNS CD and their neural mechanisms.

1. The principle of irradiation (propagation). When small groups of neurons are excited, the excitation spreads to a significant number of neurons. Irradiation is explained:

1) the presence of branched endings of axons and dendrites, due to branching, impulses spread to a large number of neurons;

2) the presence of interneurons in the central nervous system, which ensure the transmission of impulses from cell to cell. Irradiation has boundaries, which are provided by the inhibitory neuron.

2. The principle of convergence. When a large number of neurons are excited, the excitation can converge to one group of nerve cells.

3. The principle of reciprocity - coordinated work of nerve centers, especially in opposite reflexes (flexion, extension, etc.).

4. The principle of dominance. Dominant– the dominant focus of excitation in the central nervous system at the moment. This is the center of persistent, unwavering, non-spreading excitation. It has certain properties: it suppresses the activity of other nerve centers, has increased excitability, attracts nerve impulses from other foci, sums up nerve impulses. Foci of dominance are of two types: exogenous (caused by environmental factors) and endogenous (caused by internal environmental factors). The dominant underlies the formation of a conditioned reflex.

5. Feedback principle. Feedback is a flow of impulses into the nervous system that informs the central nervous system about how the response is carried out, whether it is sufficient or not. There are two types of feedback:

1) positive feedback, causing an increase in the response from the nervous system. Underlies the vicious circle that leads to the development of diseases;

2) negative feedback, reducing the activity of CNS neurons and response. Underlies self-regulation.

6. The principle of subordination. In the central nervous system there is a certain subordination of departments to each other, the highest department being the cerebral cortex.

7. The principle of interaction between the processes of excitation and inhibition. The central nervous system coordinates the processes of excitation and inhibition:

both processes are capable of convergence; the process of excitation and, to a lesser extent, inhibition are capable of irradiation. Inhibition and excitation are connected by inductive relationships. The process of excitation induces inhibition, and vice versa. There are two types of induction:

1) consistent. The process of excitation and inhibition alternates in time;

2) mutual. There are two processes at the same time - excitation and inhibition. Mutual induction is carried out through positive and negative mutual induction: if inhibition occurs in a group of neurons, then foci of excitation arise around it (positive mutual induction), and vice versa.

According to I.P. Pavlov’s definition, excitation and inhibition are two sides of the same process. The coordination activity of the central nervous system ensures clear interaction between individual nerve cells and individual groups of nerve cells. There are three levels of integration.

The first level is ensured due to the fact that impulses from different neurons can converge on the body of one neuron, resulting in either summation or a decrease in excitation.

The second level provides interactions between individual groups of cells.

The third level is provided by cells of the cerebral cortex, which contribute to a more advanced level of adaptation of the activity of the central nervous system to the needs of the body.

6. Types of inhibition, interaction of excitation and inhibition processes in the central nervous system. Experience of I. M. Sechenov

Braking– an active process that occurs when stimuli act on tissue, manifests itself in the suppression of other excitation, there is no functional function of the tissue.

Inhibition can develop only in the form of a local response.

There are two types of braking:

1) primary. For its occurrence, the presence of special inhibitory neurons is necessary. Inhibition occurs primarily without prior excitation under the influence of an inhibitory transmitter. There are two types of primary inhibition:

a) presynaptic in the axo-axonal synapse;

b) postsynaptic in the axodendritic synapse.

2) secondary. It does not require special inhibitory structures, occurs as a result of changes in the functional activity of ordinary excitable structures, and is always associated with the process of excitation. Types of secondary braking:

a) transcendental, which occurs when there is a large flow of information entering the cell. The flow of information lies beyond the functionality of the neuron;

b) pessimal, which occurs with a high frequency of irritation;

c) parabiotic, which occurs during strong and long-term irritation;

d) inhibition following excitation, resulting from a decrease in the functional state of neurons after excitation;

e) inhibition according to the principle of negative induction;

e) inhibition of conditioned reflexes.

The processes of excitation and inhibition are closely related to each other, occur simultaneously and are different manifestations of a single process. Foci of excitation and inhibition are mobile, cover larger or smaller areas of neuronal populations and can be more or less pronounced. Excitation is certainly replaced by inhibition, and vice versa, that is, there is an inductive relationship between inhibition and excitation.

Inhibition underlies the coordination of movements and protects central neurons from overexcitation. Inhibition in the central nervous system can occur when nerve impulses of varying strength from several stimuli simultaneously enter the spinal cord. Stronger stimulation inhibits reflexes that should have occurred in response to weaker ones.

In 1862, I.M. Sechenov discovered the phenomenon of central inhibition. He proved in his experiment that irritation with a sodium chloride crystal of the visual thalamus of a frog (the cerebral hemispheres have been removed) causes inhibition of spinal cord reflexes. After the stimulus was removed, the reflex activity of the spinal cord was restored. The result of this experiment allowed I.M. Secheny to conclude that in the central nervous system, along with the process of excitation, a process of inhibition develops, which is capable of inhibiting the reflex acts of the body. N. E. Vvedensky suggested that the phenomenon of inhibition is based on the principle of negative induction: a more excitable area in the central nervous system inhibits the activity of less excitable areas.

Modern interpretation of the experiment of I.M. Sechenov (I.M. Sechenov irritated the reticular formation of the brain stem): excitation of the reticular formation increases the activity of inhibitory neurons of the spinal cord - Renshaw cells, which leads to inhibition of the spinal cord motor neurons and inhibits the reflex activity of the spinal cord.

7. Methods for studying the central nervous system

There are two large groups of methods for studying the central nervous system:

1) experimental method, which is carried out on animals;

2) a clinical method that is applicable to humans.

To the number experimental methods classical physiology includes methods aimed at activating or suppressing the nerve formation being studied. These include:

1) method of transverse section of the central nervous system at various levels;

2) method of extirpation (removal of various parts, denervation of the organ);

3) method of irritation by activation (adequate irritation - irritation with an electrical impulse similar to a nervous one; inadequate irritation - irritation with chemical compounds, graded irritation with electric current) or suppression (blocking the transmission of excitation under the influence of cold, chemical agents, direct current);

4) observation (one of the oldest methods of studying the functioning of the central nervous system that has not lost its significance. It can be used independently, and is often used in combination with other methods).

Experimental methods are often combined with each other when conducting experiments.

Clinical method aimed at studying the physiological state of the central nervous system in humans. It includes the following methods:

1) observation;

2) method of recording and analyzing electrical potentials of the brain (electro-, pneumo-, magnetoencephalography);

3) radioisotope method (investigates neurohumoral regulatory systems);

4) conditioned reflex method (studies the functions of the cerebral cortex in the mechanism of learning and the development of adaptive behavior);

5) questionnaire method (assesses the integrative functions of the cerebral cortex);

6) modeling method (mathematical modeling, physical modeling, etc.). A model is an artificially created mechanism that has a certain functional similarity with the mechanism of the human body being studied;

7) cybernetic method (studies control and communication processes in the nervous system). Aimed at studying organization (systemic properties of the nervous system at various levels), management (selection and implementation of influences necessary to ensure the functioning of an organ or system), information activity (the ability to perceive and process information - an impulse in order to adapt the body to environmental changes).

There are the following methods for studying the functions of the central nervous system:

1. Method of cutting the brain stem at various levels. For example, between the medulla oblongata and the spinal cord.

2. Method of extirpation (removal) or destruction of parts of the brain.

3. Method of irritating various parts and centers of the brain.

4. Anatomical and clinical method. Clinical observations of changes in the functions of the central nervous system when any of its parts are affected, followed by a pathological examination.

5. Electrophysiological methods:

A. electroencephalography - registration of brain biopotentials from the surface of the scalp. The technique was developed and introduced into the clinic by G. Berger.

b. registration of biopotentials of various nerve centers; used in conjunction with stereotactic technique, in which electrodes are inserted into a strictly defined nucleus using micromanipulators.

V. evoked potential method, recording the electrical activity of brain areas during electrical stimulation of peripheral receptors or other areas;

6. method of intracerebral administration of substances using microinophoresis;

7. chronoreflexometry - determination of reflex time.

Properties of nerve centers

The nerve center (NC) is a collection of neurons in various parts of the central nervous system that provide regulation of any function of the body. For example, the bulbar respiratory center.

The following features are characteristic for the conduction of excitation through nerve centers:

1. Unilateral conduction. It goes from the afferent, through the intercalary to the efferent neuron. This is due to the presence of interneuron synapses.

2. Central delay in the conduction of excitation. Those. Excitation along the NC is much slower than along the nerve fiber. This is explained by synaptic delay. Since there are most synapses in the central link of the reflex arc, the conduction speed there is the lowest. Based on this, reflex time is the time from the onset of exposure to the stimulus to the appearance of the response. The longer the central delay, the longer the reflex time. However, it depends on the strength of the stimulus. The larger it is, the shorter the reflex time and vice versa. This is explained by the phenomenon of summation of excitations in synapses. In addition, it is determined by the functional state of the central nervous system. For example, when the NC is tired, the duration of the reflex reaction increases.

3. Spatial and temporal summation. Temporal summation occurs, as in synapses, due to the fact that the more nerve impulses arrive, the more neurotransmitter is released in them, the higher the EPSP amplitude. Therefore, a reflex reaction can occur to several successive subthreshold stimuli. Spatial summation is observed when impulses from several neuron receptors go to the nerve center. When subthreshold stimuli act on them, the resulting postsynaptic potentials are summed up and a propagating AP is generated in the neuron membrane.

4. Transformation of the rhythm of excitation - a change in the frequency of nerve impulses when passing through the nerve center. The frequency may decrease or increase. For example, increasing transformation (increase in frequency) is due to the dispersion and multiplication of excitation in neurons. The first phenomenon occurs as a result of the division of nerve impulses into several neurons, the axons of which then form synapses on one neuron (Figure). Second, the generation of several nerve impulses during the development of an excitatory postsynaptic potential on the membrane of one neuron. The downward transformation is explained by the summation of several EPSPs and the appearance of one AP in the neuron.

5. Post-tetanic potentiation is an increase in the reflex response as a result of prolonged excitation of the neurons of the center. Under the influence of many series of nerve impulses passing at high frequency through synapses. A large amount of neurotransmitter is released at interneuron synapses. This leads to a progressive increase in the amplitude of the excitatory postsynaptic potential and long-term (several hours) excitation of neurons.

6. Aftereffect is a delay in the end of the reflex response after the cessation of the stimulus. Associated with the circulation of nerve impulses along closed circuits of neurons.

7. The tone of the nerve centers is a state of constant increased activity. It is caused by the constant supply of nerve impulses to the NC from peripheral receptors, the stimulating influence of metabolic products and other humoral factors on neurons. For example, a manifestation of the tone of the corresponding centers is the tone of a certain muscle group.

8. Automaticity or spontaneous activity of nerve centers. Periodic or constant generation of nerve impulses by neurons that arise spontaneously in them, i.e. in the absence of signals from other neurons or receptors. It is caused by fluctuations in metabolic processes in neurons and the effect of humoral factors on them.

9. Plasticity of nerve centers. This is their ability to change functional properties. In this case, the center acquires the ability to perform new functions or restore old ones after damage. The basis of plasticity N.Ts. lies the plasticity of synapses and membranes of neurons, which can change their molecular structure.

10. Low physiological lability and fatigue. N.Ts. can conduct pulses of only a limited frequency. Their fatigue is explained by fatigue of synapses and deterioration of neuronal metabolism.

Inhibition in the central nervous system

The phenomenon of central inhibition was discovered by I.M. Sechenov in 1862. He removed the frog's brain hemispheres and determined the time of the spinal reflex to irritation of the paw with sulfuric acid. Then to the thalamus, i.e. visual tubercles applied a crystal of table salt and found that the reflex time increased significantly. This indicated inhibition of the reflex. Sechenov concluded that the overlying N.Ts. when excited, they inhibit the underlying ones. Inhibition in the central nervous system prevents the development of excitation or weakens ongoing excitation. An example of inhibition could be the cessation of a reflex reaction against the background of the action of another, stronger stimulus.

Initially, a unitary-chemical theory of inhibition was proposed. It was based on Dale's principle: one neuron - one transmitter. According to it, inhibition is provided by the same neurons and synapses as excitation. Subsequently, the correctness of the binary chemical theory was proven. In accordance with the latter, inhibition is provided by special inhibitory neurons, which are intercalary. These are Renshaw cells of the spinal cord and Purkinje neurons. Inhibition in the central nervous system is necessary for the integration of neurons into a single nerve center.

The following inhibitory mechanisms are distinguished in the central nervous system:

1. Postsynaptic. It arises in the postsynaptic membrane of the soma and dendrites of neurons. Those. after the transmitting synapse. In these areas, specialized inhibitory neurons form axo-dendritic or axo-somatic synapses (Fig.). These synapses are glycinergic. As a result of the effect of GLI on glycine chemoreceptors of the postsynaptic membrane, its potassium and chloride channels open. Potassium and chloride ions enter the neuron, and IPSP develops. The role of chlorine ions in the development of IPSP is small. As a result of the resulting hyperpolarization, the excitability of the neuron decreases. The conduction of nerve impulses through it stops. The alkaloid strychnine can bind to glycine receptors on the postsynaptic membrane and turn off inhibitory synapses. This is used to demonstrate the role of inhibition. After the administration of strychnine, the animal develops cramps in all muscles.

2. Presynaptic inhibition. In this case, the inhibitory neuron forms a synapse on the axon of the neuron that approaches the transmitting synapse. Those. such a synapse is axo-axonal (Fig.). The mediator of these synapses is GABA. Under the influence of GABA, chloride channels of the postsynaptic membrane are activated. But in this case, chlorine ions begin to leave the axon. This leads to a small local but long-lasting depolarization of its membrane. A significant part of the sodium channels of the membrane is inactivated, which blocks the conduction of nerve impulses along the axon, and consequently the release of the neurotransmitter at the transmitting synapse. The closer the inhibitory synapse is located to the axon hillock, the stronger its inhibitory effect. Presynaptic inhibition is most effective in information processing, since the conduction of excitation is not blocked in the entire neuron, but only at its one input. Other synapses located on the neuron continue to function.

3. Pessimal inhibition. Discovered by N.E. Vvedensky. Occurs at a very high frequency of nerve impulses. A persistent, long-term depolarization of the entire neuron membrane and inactivation of its sodium channels develops. The neuron becomes unexcitable.

Both inhibitory and excitatory postsynaptic potentials can simultaneously arise in a neuron. Due to this, the necessary signals are isolated.

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Ministry of Health of the Republic of Belarus Vitebsk State Order of Peoples' Friendship Medical University

Department of Normal Physiology

ABSTRACT

ontopic: " Modernmethodsresearchcentral nervous system"

Performer: student of group 30, 2nd year

Faculty of Medicine

Seledtsova A.S.

Vitebsk, 2013

Content

• Methods for studying the central nervous system
• Clinical methods
• Evoked potential method
• Rheoencephalography
• Echoencephalography
• CT scan
• Echoencephaloscopy
• Bibliography

Methods for studying the central nervous system

There are two large groups of methods for studying the central nervous system:

1) experimental method, which is carried out on animals;

2) a clinical method that is applicable to humans.

Experimental methods in turn can be divided into:

behavioral

physiological

· morphological

· methods of chemical analysis

The main behavioral methods include:

observation of animal behavior in natural conditions. Here we should highlight telemetric methods - a variety of technical techniques that make it possible to record the behavior and physiological functions of living organisms at a distance. The successes of telemetry in biological research are associated with the development of radio telemetry;

study of animal behavior in laboratory conditions. These are classical conditioned reflexes, for example, the experiments of I.P. Pavlov on conditioned reflex salivation in dogs; the method of conditioned instrumental reflex in the form of manipulation of levers, introduced in the 30s by Skinner. In the “Skinner chamber” (there are numerous modifications of this chamber), the influence of the experimenter on the behavior of the animal is excluded and, thereby, an objective assessment of the conditioned reflex actions of experimental animals is provided.

Morphological methods include a wide variety of methods for staining neural tissue for light and electron microscopy. The use of modern computer technologies has provided a qualitatively new level of morphological research. Using a confocal laser scanning microscope, a three-dimensional reconstruction of an individual neuron is created on a display screen.

Physiological methods are no less numerous. The main ones include the method of destruction of nervous tissue, electrical stimulation, and the method of electrical recording.

The destruction of nervous tissue, to establish the functions of the structures under study, is carried out using:

neurosurgical transections, by interrupting nerve pathways or individual parts of the brain

electrodes, when passing an electric current through them, either constant, this method is called the method of electrolytic destruction, or high-frequency current - the thermocoagulation method.

surgical removal of tissue with a scalpel - extirpation method or suction - aspiration method

chemical exposure to substances that can cause selective death of nerve cells (kainic or ibotenic acids and other substances)

This group also includes clinical observations of various damage to the nervous system and brain as a result of injuries (military and domestic injuries).

The electrical stimulation method is used to stimulate various parts of the brain with electric current to establish their functions. It was this method that revealed the somatotopy of the cortex and compiled a map of the motor area of ​​the cortex (Penfield's homunculus).

Clinical methods

Electroencephalography.

Electroencephalography is one of the most common electrophysiological methods for studying the central nervous system. Its essence lies in recording rhythmic changes in the potentials of certain areas of the cerebral cortex between two active electrodes (bipolar method) or an active electrode in a certain zone of the cortex and a passive electrode superimposed on an area remote from the brain. An electroencephalogram is a recording curve of the total potential of the constantly changing bioelectrical activity of a significant group of nerve cells. This amount includes synaptic potentials and partly action potentials of neurons and nerve fibers. Total bioelectrical activity is recorded in the range from 1 to 50 Hz from electrodes located on the scalp. The same activity from the electrodes, but on the surface of the cerebral cortex is called an electrocorticogram. When analyzing EEG, the frequency, amplitude, shape of individual waves and the repeatability of certain groups of waves are taken into account. Amplitude is measured as the distance from the baseline to the peak of the wave. In practice, due to the difficulty of determining the baseline, peak-to-peak amplitude measurements are used. Frequency refers to the number of complete cycles completed by a wave in 1 second. This indicator is measured in hertz. The reciprocal of the frequency is called the period of the wave. The EEG records 4 main physiological rhythms: b - , b - , and - . and d - rhythms.

b - the rhythm has a frequency of 8-12 Hz, amplitude from 50 to 70 μV. It predominates in 85-95% of healthy people over nine years of age (except for those born blind) in a state of quiet wakefulness with eyes closed and is observed mainly in the occipital and parietal regions. If it dominates, then the EEG is considered synchronized. The synchronization reaction is an increase in amplitude and a decrease in EEG frequency. The EEG synchronization mechanism is associated with the activity of the output nuclei of the thalamus. A variant of the b-rhythm are “sleep spindles” lasting 2-8 seconds, which are observed when falling asleep and represent regular alternations of increasing and decreasing amplitude of waves in the frequencies of the b-rhythm. Rhythms of the same frequency are: m - rhythm recorded in the Rolandic sulcus, having an arched or comb-shaped waveform with a frequency of 7-11 Hz and an amplitude of less than 50 μV; k - rhythm noted when electrodes are applied in the temporal lead, having a frequency of 8-12 Hz and an amplitude of about 45 μV. c - the rhythm has a frequency from 14 to 30 Hz and a low amplitude - from 25 to 30 μV. It replaces the b rhythm during sensory stimulation and emotional arousal. c - the rhythm is most pronounced in the precentral and frontal areas and reflects a high level of functional activity of the brain. The change from the b-rhythm (slow activity) to the b-rhythm (fast low-amplitude activity) is called EEG desynchronization and is explained by the activating influence of the reticular formation of the brainstem and the limbic system on the cerebral cortex. and - the rhythm has a frequency from 3.5 to 7.5 Hz, an amplitude from 5 to 200 μV. In a waking person, the rhythm is usually recorded in the anterior regions of the brain during prolonged emotional stress and is almost always recorded during the development of the phases of slow-wave sleep. It is clearly registered in children who are in a state of displeasure. The origin of the i-rhythm is associated with the activity of the bridge synchronizing system. d - the rhythm has a frequency of 0.5-3.5 Hz, an amplitude from 20 to 300 μV. Occasionally recorded in all areas of the brain. The appearance of this rhythm in a awake person indicates a decrease in the functional activity of the brain. Stably fixed during deep slow-wave sleep. The origin of the EEG d rhythm is associated with the activity of the bulbar synchronizing system.

d - waves have a frequency of more than 30 Hz and an amplitude of about 2 μV. Localized in the precentral, frontal, temporal, parietal areas of the brain. When visually analyzing the EEG, two indicators are usually determined: the duration of the b-rhythm and the blockade of the b-rhythm, which is recorded when a particular stimulus is presented to the subject.

In addition, the EEG has special waves that differ from the background ones. These include: K-complex, l - waves, m - rhythm, spike, sharp wave.

central nervous tomography echoencephalography

The K complex is a combination of a slow wave with a sharp wave, followed by waves with a frequency of about 14 Hz. The K-complex occurs during sleep or spontaneously in a waking person. The maximum amplitude is observed in the vertex and usually does not exceed 200 μV.

L - waves - monophasic positive sharp waves arising in the occipital area associated with eye movements. Their amplitude is less than 50 μV, frequency is 12-14 Hz.

M - rhythm - a group of arched and comb-shaped waves with a frequency of 7-11 Hz and an amplitude of less than 50 μV. They are registered in the central areas of the cortex (Roland's sulcus) and are blocked by tactile stimulation or motor activity.

Spike is a wave clearly distinguishable from background activity, with a pronounced peak lasting from 20 to 70 ms. Its primary component is usually negative. Spike-slow wave is a sequence of superficially negative slow waves with a frequency of 2.5-3.5 Hz, each of which is associated with a spike.

A sharp wave is a wave that differs from background activity with an accentuated peak lasting 70-200 ms.

At the slightest attraction of attention to a stimulus, desynchronization of the EEG develops, that is, the reaction of blocking the b rhythm develops. A well-defined b-rhythm is an indicator of the body’s rest. A stronger activation reaction is expressed not only in the blockade of the b-rhythm, but also in the strengthening of high-frequency components of the EEG: b- and d-activity. A drop in the level of functional state is expressed in a decrease in the proportion of high-frequency components and an increase in the amplitude of slower rhythms - i - and d - oscillations.

Evoked potential method

The specific activity associated with a stimulus is called an evoked potential. In humans, this is the registration of fluctuations in electrical activity that appear on the EEG with a single stimulation of peripheral receptors (visual, auditory, tactile). In animals, afferent pathways and switching centers of afferent impulses are also irritated. Their amplitude is usually small, therefore, to effectively isolate evoked potentials, the technique of computer summation and averaging of EEG sections that was recorded during repeated presentation of the stimulus is used. The evoked potential consists of a sequence of negative and positive deviations from the baseline and lasts about 300 ms after the end of the stimulus. The amplitude and latency period of the evoked potential are determined. Some of the components of the evoked potential, which reflect the entry of afferent excitations into the cortex through specific nuclei of the thalamus, and have a short latent period, are called the primary response. They are registered in the cortical projection zones of certain peripheral receptor zones. Later components that enter the cortex through the brainstem reticular formation, nonspecific nuclei of the thalamus and limbic system and have a longer latency period are called secondary responses. Secondary responses, unlike primary ones, are recorded not only in the primary projection zones, but also in other areas of the brain, connected by horizontal and vertical nerve pathways. The same evoked potential can be caused by many psychological processes, and the same mental processes can be associated with different evoked potentials.

Method for recording impulse activity of nerve cells

The impulse activity of individual neurons or a group of neurons can be assessed only in animals and, in some cases, in humans during brain surgery. To record neural impulse activity of the human brain, microelectrodes with tip diameters of 0.5-10 microns are used. They can be made of stainless steel, tungsten, platinum-iridium alloys or gold. The electrodes are inserted into the brain using special micromanipulators, which allow the electrode to be precisely positioned to the desired location. The electrical activity of an individual neuron has a certain rhythm, which naturally changes under different functional states. The electrical activity of a group of neurons has a complex structure and on a neurogram looks like the total activity of many neurons, excited at different times, differing in amplitude, frequency and phase. The received data is processed automatically using special programs.

Rheoencephalography

Rheoencephalography is a method for studying the blood circulation of the human brain, based on recording changes in the resistance of brain tissue to high-frequency alternating current depending on the blood supply and allows one to indirectly judge the amount of total blood supply to the brain, the tone, elasticity of its vessels and the state of venous outflow.

Echoencephalography

The method is based on the property of ultrasound to be reflected differently from brain structures, cerebrospinal fluid, skull bones, and pathological formations. In addition to determining the size of the localization of certain brain formations, this method allows you to estimate the speed and direction of blood flow.

CT scan

Computed tomography is a modern method that allows you to visualize the structural features of the human brain using a computer and an X-ray machine. In a CT scan, a thin beam of X-rays is passed through the brain, the source of which rotates around the head in a given plane; The radiation passing through the skull is measured by a scintillation counter. In this way, X-ray images of each part of the brain are obtained from different points. Then, using a computer program, these data are used to calculate the radiation density of the tissue at each point of the plane under study. The result is a high-contrast image of a brain slice in a given plane.

Positron emission tomography

Positron emission tomography is a method that allows you to evaluate metabolic activity in various parts of the brain. The test subject ingests a radioactive compound, which makes it possible to trace changes in blood flow in a particular part of the brain, which indirectly indicates the level of metabolic activity in it. The essence of the method is that each positron emitted by a radioactive compound collides with an electron; in this case, both particles mutually annihilate with the emission of two g-rays at an angle of 180°. These are detected by photodetectors located around the head, and their registration occurs only when two detectors located opposite each other are excited simultaneously. Based on the data obtained, an image is constructed in the appropriate plane, which reflects the radioactivity of different parts of the studied volume of brain tissue.

Nuclear magnetic resonance method

The nuclear magnetic resonance (NMR) method allows you to visualize the structure of the brain without the use of X-rays and radioactive compounds. A very strong magnetic field is created around the subject's head, which affects the nuclei of hydrogen atoms, which have internal rotation. Under normal conditions, the rotation axes of each core have a random direction. In a magnetic field, they change orientation in accordance with the lines of force of this field. Turning off the field leads to the fact that the atoms lose the uniform direction of the axes of rotation and, as a result, emit energy. This energy is recorded by a sensor, and the information is transmitted to a computer. The cycle of exposure to the magnetic field is repeated many times and as a result, a layer-by-layer image of the subject’s brain is created on the computer.

Transcranial magnetic stimulation

The transcranial magnetic stimulation (TCMS) method is based on stimulation of nervous tissue using an alternating magnetic field. TCMS allows you to assess the state of the conductive motor systems of the brain, corticospinal motor tracts and proximal segments of nerves, the excitability of the corresponding nerve structures based on the threshold value of the magnetic stimulus required to obtain muscle contraction. The method includes analysis of the motor response and determination of the difference in conduction time between stimulated areas: from the cortex to the lumbar or cervical roots (central conduction time).

Echoencephaloscopy

Echoencephaloscopy (EchoES, synonym - M - method) is a method for identifying intracranial pathology based on echolocation of the so-called sagittal structures of the brain, which normally occupy a midline position in relation to the temporal bones of the skull.

When reflected signals are graphically recorded, the study is called echoencephalography.

From the ultrasonic sensor in pulse mode, the echo signal penetrates through the bone into the brain. In this case, the three most typical and repeating reflected signals are recorded. The first signal is from the bone plate of the skull on which the ultrasound sensor is installed, the so-called initial complex (IC). The second signal is formed due to the reflection of the ultrasound beam from the midline structures of the brain. These include the interhemispheric fissure, the transparent septum, the third ventricle and the pineal gland. It is generally accepted to designate all of these formations as the middle echo (M-echo). The third recorded signal is caused by the reflection of ultrasound from the inner surface of the temporal bone, opposite to the location of the emitter - the terminal complex (CC). In addition to these most powerful, constant and typical signals for a healthy brain, in most cases it is possible to register small-amplitude signals located on both sides of the M - echo. They are caused by the reflection of ultrasound from the temporal horns of the lateral ventricles of the brain and are called lateral signals. Normally, lateral signals have less power compared to the M-echo and are located symmetrically with respect to the median structures.

Ultrasound Dopplerography (USDG)

The main task of ultrasound scanning in angioneurology is to detect disturbances in blood flow in the main arteries and veins of the head. Confirmation of subclinical narrowing of the carotid or vertebral arteries identified by ultrasound examination using duplex examination, MRI or cerebral angiography allows the use of active conservative or surgical treatment that prevents stroke. Thus, the purpose of ultrasound examination is primarily to identify asymmetry and/or direction of blood flow along the precerebral segments of the carotid and vertebral arteries and the ophthalmic arteries and veins.

Bibliography

1. http://www.medsecret.net/nevrologiya/instr-diagnostika

2. http://www.libma.ru/medicina/normalnaja_fiziologija_konspekt_lekcii/p7.

3. http://biofile.ru/bio/2484.html

4. http://www.fiziolive.ru/html/fiz/statii/nervous_system. htm

5. http://www.bibliotekar.ru/447/39. htm

6. http://human-physiology.ru/metody-issledovaniya-funkcij-cns/

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