Modern methods of studying the nervous system. Experimental methods can in turn be divided into

BIP - INSTITUTE OF LAW

M. V. PIVOVARCHIK

ANATOMY AND PHYSIOLOGY

CENTRAL NERVOUS SYSTEM

Minsk

BIP - INSTITUTE OF LAW

M. V. PIVOVARCHIK

ANATOMY AND PHYSIOLOGY

CENTRAL NERVOUS SYSTEM

Educational and methodological manual

Belarusian Institute of Law

Reviewers: Ph.D. biol. Sciences Associate Professor Ledneva I. V.,

Ph.D. honey. Sciences, Associate Professor Avdey G. M.

Pivovarchik M. V.

Anatomy and physiology of the central nervous system: Educational method. allowance / M. V. Pivovarchik. Mn.: BIP-S Plus LLC, 2005. – 88 p.

The manual corresponds to the structure of the course “Anatomy and Physiology of the Central Nervous System”, it discusses the main topics that make up the content of the course. The general structure of the nervous system, spinal cord and brain is described in detail, the features of the structure and functioning of the autonomic and somatic parts of the human nervous system, and the general principles of its functioning are described. At the end of each of the nine topics in the manual there are questions for self-control. Intended for full-time and part-time students majoring in psychology.

TOPIC 1. Methods for studying the nervous system.. 4

TOPIC 2. Structure and functions of nervous tissue. 7

TOPIC 3. Physiology of synaptic transmission. 19

TOPIC 4. General structure of the nervous system.. 26

TOPIC 5. Structure and functions of the spinal cord. 31

TOPIC 6. Structure and functions of the brain. 35

Topic 7. Motor function of the central nervous system... 57

TOPIC 8. Autonomic nervous system. 70

Topic 9. General principles of the functioning of the nervous system.. 78

BASIC LITERATURE... 87

ADDITIONAL READING... 87

TOPIC 1. Methods for studying the nervous system

Neurobiological methods.

Magnetic resonance imaging method.

Neuropsychological methods.

Neurobiological methods. In theoretical studies of the physiology of the human nervous system, the study of the central nervous system of animals plays an important role. This field of knowledge is called neurobiology. The structure of nerve cells, as well as the processes occurring in them, remain unchanged both in primitive animals and in humans. The exception is the cerebral hemispheres. Therefore, a neuroscientist can always study this or that issue of the physiology of the human brain using simpler, cheaper and more accessible objects. Such objects can be invertebrate animals. In recent years, intravital sections of the brain of newborn rats and guinea pigs and even a culture of nervous tissue grown in the laboratory have been increasingly used for these purposes. Such material can be used to study the mechanisms of functioning of individual nerve cells and their processes. For example, cephalopods (squid, cuttlefish) have very thick, giant axons (500–1000 µm in diameter), through which excitation is transmitted from the cephalic ganglion to the muscles of the mantle. The molecular mechanisms of excitation are being studied in this facility. Many mollusks have very large neurons in their nerve ganglia, which replace the brain - up to 1000 microns in diameter. These neurons are used to study the functioning of ion channels, the opening and closing of which is controlled by chemicals.

To record the bioelectrical activity of neurons and their processes, microelectrode technology is used, which, depending on the objectives of the study, has many features. Typically, two types of microelectrodes are used: metal and glass. To record the activity of single neurons, the microelectrode is fixed in a special manipulator, which allows it to be moved through the animal’s brain with high precision. Depending on the research objectives, the manipulator can be mounted on the animal’s skull or separately. The nature of the recorded bioelectrical activity is determined by the diameter of the microelectrode tip. For example, with a microelectrode tip diameter of no more than 5 μm, action potentials of single neurons can be recorded. When the diameter of the microelectrode tip is more than 10 microns, the activity of tens and sometimes hundreds of neurons is simultaneously recorded.

Magnetic resonance imaging method. Modern methods make it possible to see the structure of the human brain without damaging it. The magnetic resonance imaging method makes it possible to observe a series of successive “slices” of the brain on a monitor screen without causing any harm to it. This method makes it possible to study, for example, malignant brain tumors. The brain is irradiated with an electromagnetic field using a special magnet. Under the influence of a magnetic field, the dipoles of brain fluids (for example, water molecules) take its direction. After removing the external magnetic field, the dipoles return to their original state, and a magnetic signal appears, which is detected by special sensors. This echo is then processed using a powerful computer and displayed on a monitor screen using computer graphics methods.

Positron emission tomography. Positron emission tomography (PET) has an even higher resolution. The study is based on the introduction of a positron-emitting short-lived isotope into the cerebral bloodstream. Data about the distribution of radioactivity in the brain is collected by a computer over a specific scanning time and then reconstructed into a three-dimensional image.

Electrophysiological methods. Back in the 18th century. Italian doctor Luigi Galvani noticed that prepared frog legs contracted when they came into contact with metal. He concluded that the muscles and nerve cells of animals produce electricity. In Russia, similar studies were carried out by I.M. Sechenov: he was the first to record bioelectrical oscillations from the medulla oblongata of a frog. At the beginning of the 20th century, using much more advanced instruments, the Swedish researcher G. Berger recorded the bioelectric potentials of the human brain, which are now called electroencephalogram(EEG). In these studies, the basic rhythm of human brain biocurrents was recorded for the first time - sinusoidal oscillations with a frequency of 8 - 12 Hz, which was called the alpha rhythm. Modern methods of clinical and experimental electroencephalography have made a significant step forward thanks to the use of computers. Typically, several dozen cup electrodes are applied to the surface of the scalp during a clinical examination of a patient. Next, these electrodes are connected to a multi-channel amplifier. Modern amplifiers are very sensitive and make it possible to record electrical oscillations from the brain with an amplitude of only a few microvolts, then a computer processes the EEG for each channel.

When studying the background EEG, the leading indicator is the alpha rhythm, which is recorded mainly in the posterior parts of the cortex in a state of quiet wakefulness. When sensory stimuli are presented, suppression, or “blockade,” of the alpha rhythm occurs, the duration of which is longer, the more complex the image. An important direction in the use of EEG is the study of spatio-temporal relationships of brain potentials during the perception of sensory information, i.e., taking into account the time of perception and its cerebral organization. For these purposes, synchronous multichannel EEG recording is performed during the perception process. In addition to recording background EEG, methods are used to study brain function registration of evoked (EP) or event-related (ERP) brain potentials. These methods are based on the idea that an evoked or event-related potential is a brain response to sensory stimulation, comparable in duration to the processing time of the stimulus. Event-related brain potentials represent a broad class of electrophysiological phenomena that are isolated from the “background” or “raw” electroencephalogram using special methods. The popularity of the EP and ERP methods is explained by the ease of recording and the ability to observe the activity of many areas of the brain in dynamics over a long period of time when performing tasks of any complexity.

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).

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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 detected 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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The study of the central nervous system includes a group of experimental and clinical methods. Experimental methods include cutting, extirpation, destruction of brain structures, as well as electrical stimulation and electrical coagulation. Clinical methods include electroencephalography, evoked potentials, tomography, etc.

Experimental methods

1. Cut and cut method. The method of cutting and switching off various parts of the central nervous system is done in various ways. Using this method, you can observe changes in conditioned reflex behavior.

2. Methods of cold switching off brain structures make it possible to visualize the spatio-temporal mosaic of electrical processes in the brain during the formation of a conditioned reflex in different functional states.

3. Methods of molecular biology are aimed at studying the role of DNA, RNA molecules and other biologically active substances in the formation of a conditioned reflex.

4. The stereotactic method consists in introducing an electrode into the animal’s subcortical structures, with which one can irritate, destroy, or inject chemicals. Thus, the animal is prepared for a chronic experiment. After the animal recovers, the conditioned reflex method is used.

Clinical methods

Clinical methods make it possible to objectively assess the sensory functions of the brain, the state of the pathways, the brain’s ability to perceive and analyze stimuli, as well as identify pathological signs of disruption of the higher functions of the cerebral cortex.

Electroencephalography

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 electrocorticogram. When analyzing EEG, the frequency, amplitude, shape of individual waves and the repeatability of certain groups of waves are taken into account.

Amplitude 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.

Under 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 period waves. The EEG records 4 main physiological rhythms: ά -, β -, θ -. and δ – rhythms.

α – 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 as synchronized.

Synchronization reaction called an increase in amplitude and a decrease in frequency of the EEG. The EEG synchronization mechanism is associated with the activity of the output nuclei of the thalamus. A variant of the ά-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 ά-rhythm. Rhythms of the same frequency are:

μ – 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;

κ - rhythm, noted when applying electrodes in the temporal lead, having a frequency of 8-12 Hz and an amplitude of about 45 μV.

β - rhythm has a frequency from 14 to 30 Hz and a low amplitude - from 25 to 30 μV. It replaces the ά rhythm during sensory stimulation and emotional arousal. The β rhythm is most pronounced in the precentral and frontal areas and reflects a high level of functional activity of the brain. The change from ά - rhythm (slow activity) to β - rhythm (fast low-amplitude activity) is called desynchronization EEG is explained by the activating influence on the cerebral cortex of the reticular formation of the brainstem and the limbic system.

θ – rhythm has a frequency from 3.5 to 7.5 Hz, amplitude from 5 to 200 μV. In a waking person, the θ 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 θ rhythm is associated with the activity of the bridge synchronizing system.

δ – rhythm has a frequency of 0.5-3.5 Hz, 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 δ - EEG rhythm is associated with the activity of the bulbar synchronizing system.

γ – 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 ά-rhythm and the blockade of the ά-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, λ - waves, μ - rhythm, spike, sharp wave.

K - complex- This 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.

Λ – 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 arc-shaped 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– a wave clearly different 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.

sharp wave– a wave that differs from background activity with an emphasized peak lasting 70-200 ms.

At the slightest attraction of attention to a stimulus, desynchronization of the EEG develops, that is, a reaction of ά-rhythm blockade develops. A well-defined ά-rhythm is an indicator of the body’s rest. A stronger activation reaction is expressed not only in the blockade of the ά - rhythm, but also in the strengthening of high-frequency components of the EEG: β - and γ - activity. A decrease 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 - θ- and δ-oscillations.

Method for recording impulse activity of nerve cells

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 primary response. They are registered in the cortical projection zones of certain peripheral receptor zones. Later components that enter the cortex through the reticular formation of the brainstem, nonspecific nuclei of the thalamus and limbic system and have a longer latent 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.

Tomographic methods

Tomography– is based on obtaining images of brain slices using special techniques. The idea of this method was proposed by J. Rawdon in 1927, who showed that the structure of an object can be reconstructed from the totality of its projections, and the object itself can be described by many of its projections.

CT scan 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– a method that allows you to assess metabolic activity in different 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 γ-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(NMR imaging) 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.

Rheoencephalography

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.

Study of the functional state of the human autonomic nervous system

The study of the functional state of the ANS is of great diagnostic importance in clinical practice. The tone of the ANS is judged by the state of reflexes, as well as by the results of a number of special functional tests. Methods for clinical research of VNS are conditionally divided into the following groups:

Patient interview;
Study of dermographism (white, red, elevated, reflex);
Study of vegetative pain points;
Cardiovascular tests (capillaroscopy, adrenaline and histamine skin tests, oscillography, plethysmography, determination of skin temperature, etc.);
Electrophysiological tests – study of electro-skin resistance using a direct current device;
Determination of the content of biologically active substances, for example catecholamines in urine and blood, determination of blood cholinesterase activity.

Electroencephalography (EEG) is a recording of the total electrical activity of the brain. Electrical vibrations in the cerebral cortex were discovered by R. Keton (1875) and V.Ya. Danilevsky (1876). EEG recording is possible both on the surface of the scalp and from the surface of the cortex in experiments and in the clinic during neurosurgical operations. In this case, it is called an electrocorticogram. EEG is recorded using bipolar (both active) or unipolar (active and indifferent) electrodes applied in pairs and symmetrically in the frontal-polar, frontal, central, parietal, temporal and occipital regions of the brain. In addition to recording background EEG, functional tests are used: exteroceptive (light, auditory, etc.), proprioceptive, vestibular stimuli, hyperventilation, sleep. The EEG records four main physiological rhythms: alpha, beta, gamma and delta rhythms.

Evoked potential method (EP) is a measurement of the electrical activity of the brain that occurs in response to stimulation of receptors, afferent pathways and switching centers of afferent impulses. In clinical practice, EPs are usually obtained in response to stimulation of receptors, mainly visual, auditory or somatosensory. EPs are recorded when recording EEG, usually from the surface of the head, although they can also be recorded from the surface of the cortex, as well as in deep structures of the brain, for example, in the thalamus. VP technique used for an objective study of sensory functions, the process of perception, and brain pathways under physiological and pathological conditions (for example, with brain tumors, the shape of the EP is distorted, the amplitude decreases, and some components disappear).

Functional computed tomography:

Positron emission tomography is an intravital method of functional isotope mapping of the brain. The technique is based on the introduction of isotopes (O 15, N 13, F 18, etc.) into the bloodstream in combination with deoxyglucose. The more active an area of the brain, the more it absorbs labeled glucose, the radioactive radiation of which is recorded by detectors located around the head. Information from the detectors is sent to a computer, which creates “slices” of the brain at the recorded level, reflecting the uneven distribution of the isotope due to the metabolic activity of brain structures.

Functional magnetic resonance imaging is based on the fact that with the loss of oxygen, hemoglobin acquires paramagnetic properties. The higher the metabolic activity of the brain, the greater the volumetric and linear blood flow in a given region of the brain and the lower the ratio of paramagnetic deoxyhemoglobin to oxyhemoglobin. There are many foci of activation in the brain, which is reflected in the heterogeneity of the magnetic field. This method allows us to identify actively working areas of the brain.

Rheoencephalography is based on recording changes in tissue resistance to high-frequency alternating current depending on their blood supply. Rheoencephalography makes it possible to indirectly judge the amount of general blood supply to the brain and its asymmetry in various vascular zones, the elasticity tone of brain vessels, and the state of sudden outflow.

Echoencephalography is based on the property of ultrasound to be reflected to varying degrees from the structures of the head - brain tissue and its pathological formations, cerebrospinal fluid, skull bones, etc. In addition to determining the localization of certain brain structures (especially the median ones), echoencephalography, through the use of the Doppler effect, allows one to obtain information about the speed and direction of blood movement in the vessels involved in the blood supply to the brain ( Doppler effect- a change in the frequency and length of waves recorded by the receiver, caused by the movement of their source or the movement of the receiver.).

Chronaximetry allows you to determine the excitability of nervous and muscle tissue by measuring the minimum time (chronaxy) under the action of a stimulus of double threshold strength. Chronaxy of the motor system is often determined. Chronaxia increases with damage to spinal motor neurons and decreases with damage to cortical motor neurons. Its value is influenced by the condition of the trunk structures. For example, the thalamus and the red nucleus. You can also determine the chronaxy of sensory systems - cutaneous, visual, vestibular (by the time of occurrence of sensations), which allows us to judge the function of the analyzers.

Stereotactic method allows, using a device for precise movement of electrodes in the frontal, sagittal and vertical directions, to insert an electrode (or micropipette, thermocouple) into various structures of the brain. Through the inserted electrodes, it is possible to record the bioelectrical activity of a given structure, irritate or destroy it, and introduce chemicals through microcannulas into the nerve centers or ventricles of the brain.

Irritation method various structures of the central nervous system with a weak electric current using electrodes or chemicals (solutions of salts, mediators, hormones) supplied using micropipettes mechanically or using electrophoresis.

Shutdown method different parts of the central nervous system can be produced mechanically, electrolytically, using freezing or electrocoagulation, as well as with a narrow beam or by injecting hypnotics into the carotid artery, you can reversibly turn off some parts of the brain, for example the cerebral hemisphere.

Cutting method at different levels of the central nervous system in an experiment it is possible to obtain spinal, bulbar, mesocephalic, diencephalic, decorticated organisms, split brain (commissurotomy operation); disrupt the connection between the cortical region and underlying structures (lobotomy operation), between the cortex and subcortical structures (neuronally isolated cortex). This method allows us to better understand the functional role of both the centers located below the transection and the higher centers that are switched off.

Pathoanatomical method– intravital observation of dysfunction and post-mortem examination of the brain.

Modern methods of studying the nervous system. Experimental methods can in turn be divided into

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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:

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.

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

Evoked potential method

Method for recording impulse activity of nerve cells

Rheoencephalography

Echoencephalography

CT scan

Positron emission tomography

Nuclear magnetic resonance method

Transcranial magnetic stimulation

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.

Ultrasound Dopplerography (USDG)

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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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).