II. Meters of skin - galvanic response (GSR). Physiological mechanisms and parameters of the galvanic skin response

One of the leading indicators of the state of the central nervous system in assessing emotional tension is the skin reaction (CR). Currently, two types of CR are distinguished: phasic and tonic. Phasic CR (from the word "phase" - a variable) is the response of the central nervous system to some short situational stimulus, which is called a reaction to the novelty of information. But, if the suspect is continuously told: "You raped", then after several repetitions the response will begin to decline and soon stop altogether.

A decrease in performance may occur after the fourth or fifth presentation. This phenomenon is based on "addiction" to a significant signal. It is determined by the level of motivation in hiding information, the type of human nervous system, and its functional state.

Tonic skin reaction is a slow change in skin resistance or skin potential (tension), which characterizes the neuro-emotional state. If a person is suddenly placed in a stressful situation, then the tonic CR will be rebuilt within 2-3 minutes. Two or three minutes is the delay time of the tonic reaction to an emotional stimulus. The value of skin resistance, which was actually observed in stressful situation, changed from 300-600 kOhm to 1-0.1 kOhm. At the first stage of studying skin reactions, the researchers differentiated the methods according to the method of measurement. If a voltage is recorded between two sections of a biological tissue, then it is called the galvanic skin response (GSR) after the scientist L. Galvani, who first observed this phenomenon. Sometimes this procedure is called electrodermography (from Greek word derma - skin).

The issue of studying the skin reaction of CR in the conditions of a laboratory and production experiment is devoted to a significant number of works like ours (I.S. Kondor, 1980, N.A. Leonov, 1980, A.A. Krauklis, A.A. Aldersons, 1982, etc. .), and abroad (Wang 1961, Codor 1963, Edelbery 1964, Hori 1982, etc.). The history of the discovery of this phenomenon dates back to the end of the nineteenth century, when in 1888 C. Feret in 1889 I.R. Tarkhanov for the first time established the relationship between the level of skin resistance (skin potential) and the psychophysiological state of the body.

In his work, presented at the meeting of the St. Petersburg Society of Psychiatrists and Neurologists, I.R. Tarkhanov reported that any irritation inflicted on a person, after some time of the latent period, causes a strong change in the level of recorded indicators. Moreover, the applied irritations are not necessarily associated with the skin itself. Even the mental execution of an arithmetic action causes significant changes in the skin potential. The magnitude of the deviation depends on the state of the subject and the depth of his imagination. With the development of fatigue, the magnitude of the response is significantly reduced. Later, the discovery made by I.R. Tarkhanov was reflected in the world literature as the "Tarkhanov phenomenon", which consists in the fact that using a sensitive galvanometer, the electric potential of the skin surface was measured under various conditions of the organism under study. In parallel with Tarkhanov, almost at the same time, Feret revealed a similar relationship in the change in skin resistance. Such scientists as V.P. Gorev, (1943), S. Duret R. Duret, (1956) et al. conducted a comparative evaluation of two methods for measuring skin resistance and skin potential.

In the subjects, CR and electrical skin resistance were simultaneously recorded under various sound, light, and pain stimuli. They found that the curve shapes are almost identical. Despite the fact that more than 100 years have passed since the first serious study of the skin potential, the question of the mechanism of the galvanic skin reflex remains rather controversial. So, in 1889 I.R. Tarkhanov came to the conclusion that skin potentials arise due to the removal of biocurrent from areas with different amount sweat glands. To implement his idea, I.R. Tarkhanov proposed a special technique for diverting the skin potential. He recommended the palmar and dorsal surfaces of the hand and the forearm of a person as points for applying electrodes. According to I.R. Tarkhanov, there is a change in the intensity of sweat secretion under the influence of the central nervous system. Tarkhanov's theory of the origin of CR was questioned in 1963 (Zyerina, Skoril, Saurek). Studying the speed of propagation of CR, they found that in the upper limbs it is 154.9 cm/sec, and in the lower limbs - 71.6 cm/sec. In connection with these data, the assumption is quite justified that metabolic processes, especially the function of the sweat glands, cannot underlie the occurrence of CR. Since their excretory processes too inert compared to the speed of the CR.

The independence of the origin of CR from the functional state of the sweat glands was demonstrated by Wilcott (1957). Simultaneously examining perspiration, skin electrical resistance, and skin potential from the palms of 35 subjects during tests of oral math problem solving, Wilcott et al. found that changes in electrical skin resistance occur 1.1 seconds earlier than sweating. It was found that the delay time of CR in the same subject is almost constant. Despite a number of conflicting and even often mutually exclusive theories about the origin of the constant potential, no one doubts the participation of the central nervous apparatus in this process. The skin reaction is closely related to both general condition the central nervous system and its various departments.

By recording the area of ​​the described CR curve from both hands, Raevskaya et al. (1985) revealed an asymmetry in the reaction. right hand. This is apparently due to the fact that in this case the left hemisphere is predominantly activated. Studies conducted during the transition from wakefulness to sleep have shown that during falling asleep, the phasic activity of GSR decreases, reaching a minimum during sleep.

An attempt was made to study the daily rhythms of electrocutaneous resistance in order to establish its periodicity. So, Pytenfranz, Hellbrugge, Niggeschmid (1956), examining the daily periodicity for 8 subjects, found that the rhythm of oscillations of this resistance from 8 to 11 hours was significantly higher, and from 12-15 and 18-20 hours below the average level. The daily curves of electrical skin resistance in children, in general, are similar to those of adults, although they were shifted to the left by 1-2 hours (for children, the morning maximum is at 8 am, for adults at 10 am, the daily minimum is at 12 and 2 pm, respectively). The maximum "flattening" of the curve and its greatest stability in children was observed at 20-22 hours, and in adults after 24 hours. The skin reaction is one of those indicators that is a reliable indicator of the organism for the novelty of the stimulus. CR arises only as a result of a mismatch between the received information and the expected one, and is not the result of "irritation" in the usual sense of the word. (E.N. Sokolov, 1960, 1962).

The nature of CR is also significantly influenced by age and individual-sex differences (E.N. Kutchak et al.). Studying the changes in human skin resistance in the process of its development, it was found that the minimum numbers are observed in newborns, and, starting from one year, skin resistance gradually increases. In old age, there is a decrease in CR, reaching a value not much greater in old age than in newborns.

Research V.N. Myasishcheva (1929, 1936) revealed a direct relationship between the magnitude of the stimulus and the amplitude of the CR. At the same time, in the work of A.I. Zingerman (1967) showed an inverse relationship between the probability of a signal and the magnitude of the galvanic skin response. The lower the probability of its occurrence, the greater the CR response. Skin reaction accompanies everything mental processes of a person, especially if they have a clear emotional coloring, being a total biological effect, the nature of which is determined by the functional state a large number organs and tissues of the body and allows, in some cases, quite finely analyzing the psychophysiological reactions of a person (A.K. Podshibyakin, 1949, 1954; I.A. Vetokhin, L.P. Timofeeva, 1957). In 1967, Lakte found that CR can reflect the body's preparation for the upcoming perception of information, taking into account physiological features person and nature of motivations.

The study of CR at various degrees tension made it possible to reveal a direct dependence of the magnitude of the change in skin resistance on the magnitude of emotional tension. The galvanic skin response can be used not only as an indicator emotional state of a person, but also, under appropriate conditions, allows you to determine its value. A stimulus of greater social significance (subject to the same emotional stability of the organism) will correspond to a more pronounced manifestation of the skin reaction.

CR is based on neural mechanisms that ultimately reflect both the magnitude of the stimulus and the probability of its occurrence (entropy). The nature of the CR response is largely determined by the functional level of the regulatory system, whether a person is tired or alert, whether he has a pathology. Various methodological approaches were used to assess the information content of CR. The delay time (Dorrow 1967), the maximum amplitude (A.A. Krauklis, A.A. Aldersons, 1982), the duration and area of ​​waves (P.V. Tarakanov, 1982) were studied. Each of the methods has the right to exist, although, in our opinion, the measurement of the area of ​​Raman waves should be considered the most informative indicator. Analyzing the results of studies by various authors on CI, we see that, in some cases, when relatively identical sources of stress were exposed to a person, researchers came to completely opposite results. To identify the reasons for the inconsistency of the results obtained, a special study was carried out (VA Varlamov, 1974). The experiment involved two groups of subjects: emotionally stable and emotionally unstable, inadequately responding to stress. The tonic and phasic components of CG were recorded against the background of a gradually increasing neuro-emotional load (segment a - m Fig. 2). It was found that the tonic component of CR changed unidirectionally with increasing emotional stress (skin resistance decreased). At the same time, phasic CR had a biphasic dependence on the magnitude of emotional stress (Fig. 2). At the first stage of the task, an increase in the frequency and amplitude of the phase RR oscillations was observed. Further, with the continued increase in emotional stress, there was a decrease in the amplitude of the CR (point M). These studies once again confirmed the need to be attentive to the functional state of a person during the study, to strive to optimize his condition, otherwise the polygraph examination data will be significantly distorted.

Rice. 2. Measuring the frequency and amplitude of CR with a smoothly increasing and gradually decreasing emotional stress:

a - background,
b - maximum response at the stage of increasing emotional stress,
c - minimum reaction at the moment of maximum stress,
e ~ maximum response at the stage of reducing emotional stress,
e - termination of the emotional stimulus,
M - maximum emotional stress

Analysis of data on the mechanism of occurrence and regulation of skin reaction, its informative signs showed that:
-tonic skin reaction is a reflection of the deep processes of functional restructuring in the central nervous system;
- the magnitude of the "response" of the galvanic skin reflex is directly dependent on the novelty of the stimulus, the typological features of the higher nervous activity, the level of motivation of the subject and his functional state;
- the dynamics of the indicators of phasic CR can be a criterion for the degree of emotional overstrain of the human functional system. If a further increase in emotional stress leads to a decrease in phasic CR, then this indicates the limit of the subject's functional capabilities;
- methods of registration, measurement of the dynamics of skin resistance, or skin potential, in terms of informativeness, do not differ;
- informative features of the RC curve are common to any periodic curves.

When analyzing CR, it is necessary to take into account the characteristics of the mobility of the nervous system of people, taking into account regional and national characteristics. It is impossible to determine from the CR curve whether a representative of what nationality is being tested, a Georgian or a Chechen, but it is possible to determine that they are representatives of the "southern" peoples, both temperamental, with a mobile nervous system. Indicators that can be used for further analysis are presented in fig. 3. These include the reaction delay time ( segment a-b). From the moment the stimulating information is presented to the subject, the reaction delay time is normally 1.2-3 seconds. The length of the ascending curve (segment b-c) characterizes the power of the activating excitation processes. Downward curve ( segment c-g) - the intensity of the inclusion of inhibitory processes. The time during which the reaction reached its maximum (1D determines the mobility of excitation processes.

In almost all cases, when analyzing CR curves, the maximum height of the curve (h) is measured, which reflects the strength of the emotional response of the central nervous system of the subject to the presented stimulus. The area measured under the curve (S,) is highly informative. It is an integral indicator that combines the amplitude (N) and the total duration of the curve t 1 . Carries information and the negative phase of the main curve (p). The negative phase is the part of the curve that

Rice. 3. Indicators characterizing the CR curve:

A is the amplitude of the reaction,
B - time
C - stimulus
a, b - reaction delay time,
b, c - the length of the "ascending" curve,
c, d - the length of the "descending" curve,
t is the time it takes for the reaction to reach its maximum,
tg is the time it takes for the reaction to return to its original state,
h is the amplitude of the curve,
S- area under the curve,
D - top of the negative phase of the curve,
h is the amplitude of the negative phase of the curve,
f, h - "decaying" curves.

It is below the zero line and characterizes the degree of inhibitory reactions of the central nervous system, designed to correct excitation reactions. The curve of the negative phase (top "D") is analyzed according to the same indicators as the main one (by the duration of the amplitude, etc.), with the only difference that it characterizes inhibitory processes. The greater the amplitude h in the curve of the negative phase, the more actively the system was connected, counteracting, that is, inhibiting the excitation processes after their manifestation. The state of excitation caused by the presented stimulus cannot be constant, endless.

The inclusion of braking mechanisms carries protective function, since a long stay of the human body in a state of excitation is undesirable, it adversely affects the system as a whole. If the inhibitory mechanism is very powerful, then the curve "overshoots" the zero level and passes into the "negative phase" (Fig. 4 - curve 1B). his condition in extreme conditions.

However, it should be remembered that there may be exceptions related to the individual characteristics of the subject, or the technique of counteraction used by him. The descending part of the curve is a reflection of the inclusion of inhibitory processes. The more powerful this process, the faster the excitation is compensated and the steeper the curve tends to the isoline (Fig. 4 - curve 1B). If the CR reaction is positive, i.e. Since the curve is at the top of the isoline, its ascending part and amplitude are determined by excitation processes. Normally, the balance of excitatory-inhibitory processes is expressed by the ratio as 1.0: 1.2. Inhibitory processes should slightly predominate over excitatory processes by about 5-10%. The presence of a powerful inhibitory process is of great importance for the normal functioning of the nervous system. However, an important role in responding to stimulating information is also played by the presence of consistency, balance, and the interaction of the processes of excitation and inhibition.

In the absence of balance and coherence, once inhibition is switched on, it will affect the human body for a very long time, which can also lead to difficulties in interpreting the results obtained. This phenomenon can be traced on curve no. 2B (Fig. 4). The resulting excitation (top "A") was compensated by inhibition (B), which did not "switch off" almost until the end of the registration of the reaction. Opposite reactions also occur in practice (curve 3). Curve from peak "A", caused by increased excitation to stimulus (N), very slowly

Rice. 4. Some types of CR form in the background and after the stimulus was given:

N - stimulus,

A, B, C, D - vertices of the curve,

Isoline.

returns to the original level. This phenomenon is possible if the response, inhibitory process turns on slowly, sluggishly, inadequately to the strength of the excitation process. The lack of balance between activating and depressing processes can also be seen in Fig. AL- After a standard response to a stimulus, the curve does not decay and does not return to the baseline. Several small bursts appear on it, lasting almost the entire measurement period. It should be borne in mind that the greater the coordination of the processes of excitation and inhibition, the less additional vertices are traced on the curve.

The regulatory system in the body is designed in such a way that there is always a certain imbalance of corrective processes. This is due to the fact that commands from the "center" about the inclusion of certain reactions are received with a delay, and, consequently, they are somewhat over-regulated. In our example (curve 4), this phenomenon is clearly visible. After an increase in the process of excitation, which led to the appearance of the peak "A", inhibitory reactions are switched on. The curve sharply decreases, reaching the isoline. By the time the command arrives at the "center" that the process of bringing the excitation reaction to the initial base level is over, the opposite command will arrive - to weaken the inhibitory processes.

Time will pass, the curve will "overshoot" the baseline ( points B, C, G). And the system that increases excitation will be “connected”, and the curve will go up, trying to reach the initial level. And again, due to the delay of commands, there will be a "overshoot" of the isoline, etc.

In this case, we are dealing with a system that is constantly in motion, never stopping. The amplitude of these "swings" is closely related to the magnitude of emotional stress and is determined by the general functional state of the subject. This explains the appearance of additional vertices on the curve or an increase in the amplitude of the previously existing ones. In practice, one can encounter an increase in both the number of vertices and their amplitude, although this phenomenon is not necessary.

There are cases when additional curve vertices are more clearly expressed in the background before testing (Fig. 4 - curve 5 vertices C and B). At the beginning of testing, they sharply decrease or disappear altogether. This is due to waiting stress, which is based on a lack of information about the verification procedure. This type of reaction is observed in people for whom the lack (deficit) of information, its uncertainty cause greater emotional stress than the information itself (curve 5).

Fig.5 Various forms CR reactions in response to a presented stimulus:
N-stimulus
A, B-curve vertices

Expectation stress can also manifest itself in the reappearance of peaks on the curve (curve 6B). This false signal, which does not carry information on the presented stimulus (question), is easily determined if it was preceded by a relatively flat section of the polygram for a long time. The specialist must remember that the "delay" in the appearance of a response to the question is within 1.2-3 seconds from the moment the subject becomes aware of the information presented to him, if the recording of the results begins after question asked. Therefore, the "key" word in the question should be at the end of the phrase. For example, you can construct the phrase: "Did you kill a woman with a child?". The CR reaction can be received after the words "killed". IN this example it is the main (key) in the formation of emotional tension. The same information could be presented to the subject in a different sequence: "Did you kill a woman with a child?" In this question, the keyword is at the end of the phrase. The response to it will appear in 1.2-3 seconds. If the "response" reaction on the CR curve is observed after 4-6 seconds or more, then it is caused not by the presented stimulus, but by the associative memory of events related to his past, including the criminal one. If the main information embedded in the presented question and the associative one is recognized by the subject with small time delays, then the curve may have several peaks (Fig. 5-2 A, B). For example, this reaction may occur if citizen "M", previously convicted of rape, upon presentation of a significant question, begins a normal reaction after 1.2-2 seconds. after the "key" word, and at that moment he will remember the place of deprivation of liberty, where, by coincidence, he miraculously managed to stay alive. This information is the stimulus that causes additional emotional stress. It is possible that these memories may be somewhat delayed in time. In this case, a second, rather powerful peak is observed (Fig. 5 - curve 3 B). In this example with citizen "M", there may be cases when, after the "key" word, he first remembers the events in the zone (Fig. 5 - curve 4 A), and then the next crime he committed (4 B).

In 1888 Dr. Feret described the following case. A patient with hysterical anorexia, whom he tactfully refers to as "Madame X," complained of electrical tingling sensations in her hands and feet. Feret noticed that these sensations intensified when the patient inhaled some smell, looked at a piece of colored glass, or listened to the sound of a tuning fork. We do not know whether the patient's tingling in the extremities ceased, but during the course of the examination Feret found that when a weak current was passed through the forearm, there were systematic changes in the electrical resistance of the skin. Two years later, Tarkhanov independently showed that similar electrical shifts can be observed without the application of an external current. Thus, he discovered the skin potential and, in addition, established that this potential changes both during internal experiences and in response to sensory stimulation.

Later, this electrical activity of the skin was called the "galvanic skin response" (CSR). This term has survived to this day. Although it was difficult to measure such subtle shifts with primitive instruments used at the beginning of the century, the predictability and drama of GSR has attracted the attention of many researchers. If you have never observed this simple phenomenon, it will be difficult for you to imagine the excitement of the early explorers who saw endless possibilities in this field. Imagine that your fingers are connected to a huge machine with the help of an intricate tangle of wires and that you are in an old laboratory of the beginning of our century. Now imagine that every time you visualize your friend's face, the arrow measuring instrument moving out of place!

One of the first researchers of the GSR was Carl Jung. He viewed GSR as an objective physiological "window" into unconscious processes, which was postulated by his mentor Freud. It was in Jung's work that it was first shown that the magnitude of the electrical reaction of the skin reflects, apparently, the degree of emotional experience. The more you are affected by what you imagine, the more the arrow deviates.

In this atmosphere of enthusiasm, hundreds of scientists began to use their cumbersome equipment to determine in which situations GSR arises. In one study of fear, Nancy Bailey tested her fellow students with the following stimuli: they listened to a story about cattle drowning in the sea; they held a burning match in their hand until it began to burn their fingers; then, four feet away, a revolver was fired, loaded with a blank cartridge which made a particularly loud sound; and some were given this revolver to shoot themselves. Based on the subjective report of the subjects and the analysis of physiological reactions, Bailey came to the conclusion that there are two types of fear: fear of surprise and fear due to understanding of the situation. Waller studied GSR in subjects who mentally imagined a German air raid on London, and Linde (1928) found that more funny jokes naturally caused a more pronounced GSR (to the delight of psychophysicists, this dependence turned out to be a Weber-Fechner logarithmic curve).

The electrical changes in the skin are so striking and so easy to measure that where psychophysiologists were looking for the basic laws of behavior, other people saw practical possibilities. At one time, advertising agencies were looking at whether the GSR in response to an advertisement could predict how effectively the advertisement would influence the sale of a product. In one preliminary study, a group of housewives had the highest GSR for pancake flour ads that were actually more effective than other ads. However, the same experiment, carried out on the same group of subjects with advertising baby food, was less successful. This is not surprising. This and many other similar studies were based on the assumption that the advertising that causes the most emotional reaction in people should have the greatest effect on the sale of the product; but this is an assumption different occasions could be both true and false. Be that as it may, the use of GSR in advertising turned out to be another short-lived fad.

Many companies supplying electronic equipment, sell inexpensive devices now that can emit tones of different heights or volumes depending on the resistance in the circuit. A person can become the soul of the evening if, by connecting such a machine to the palms of an unsuspecting friend, he asks him purely personal questions. The machine will probably begin to publish treacherous screams in all cases when he lies. This is, of course, just a harmless toy, but only as long as it is not used to invade the privacy of innocent viewers.

More expensive versions of the same devices are sold in the name of science and religion. It can be said that the less experienced in worldly affairs the consumer, the sooner he will pay money to measure the reaction of his sweat glands.

1. A method for recording galvanic skin reactions, including fixing two electrodes on the human body, applying electrical voltage to them, and registering changes in time electric current, flowing between the electrodes and fixation of current pulses in the frequency band of the physical component of the electrodermal activity, characterized in that the shape of each pulse in the sequence of pulses in the frequency band of the physical component is analyzed, for which the signal is recorded in the form of the time derivative of the logarithm of the numerical value of the electric current, and the the value of the trend due to changes in the signal in the frequency band of the tonic component of the electrodermal activity, and the value of the first derivative is corrected by subtracting the value of the trend from it, the second time derivative of the logarithm of the numerical value of the electric current is recorded, the beginning of the pulse of the said signal is determined by the moment the second derivative of the threshold value is exceeded , and then determine the compliance of the pulse shape with the established criteria, and if there is such a correspondence, the analyzed pulse is attributed to the impulses of the physical component, and in the absence of such a correspondence, they are referred to as artifacts.

2. The method according to claim 1, characterized in that the trend value is determined as the average value of the first derivative over a time interval, preferably from 30 to 120 s.

3. The method according to claim 1, characterized in that the trend value is determined as the average value of the first derivative over a time interval of 1 - 2 s, provided that the values ​​of the first and second derivatives are less than the specified threshold values ​​during this time interval.

4. The method according to any one of claims 1 to 3, characterized in that the arrival time of the pulse of the first derivative is considered the moment when the second derivative exceeds the threshold value by at least 0.2%.

5. The method according to any one of claims 1 to 4, characterized in that when determining the pulse shape, the values ​​​​of the maximum f max and minimum f min of the first derivative are recorded minus the trend value, their ratio r, the time interval tx between the minimum and maximum of the first derivative , while the moments of reaching the maximum and minimum values ​​of the first derivative are determined by the moment of sign change of the second derivative.

6. The method according to claim 5, characterized in that the criteria for belonging of the analyzed pulse to the signal of the physical component of the electrodermal activity are inequalities
0,5 < f max < 10;
-2 < f min < -0,1;
1,8 < t x < 7;
1,5 < r < 10.

7. A device for recording galvanic skin reactions, containing electrodes with means for their fastening connected to the input device, means for suppressing impulse noise, means for isolating a signal in the frequency band of the physical component of electrodermal activity, means for detecting pulses of the physical component, a registration unit, characterized in that the means for separating the signal in the frequency band of the physical component, the means for suppressing impulse noise and the means for detecting pulses of the physical component are made in the form of a low-pass filter connected in series to the input device, a block for converting the input signal into the first and second time derivatives and a block pulse shape analysis, while the output of the latter is connected to the input of the registration unit.

8. The device according to claim 7, characterized in that the input device is a stabilized source of electrical voltage and a resistor connected in series to the electrodes, a logarithmic amplifier with a differential input stage, while the resistor shunts the inputs of the logarithmic amplifier.

9. The device according to claim 7 or 8, characterized in that the unit for converting the input signal into the first and second time derivatives is made in the form of the first and second differentiators and a low-pass filter, while the output of the first differentiator is connected to the inputs of the second differentiator and the low-pass filter frequencies whose outputs are block outputs.

10. The device according to any one of claims 7 to 9, characterized in that the shape analysis unit includes means for determining the maximum rate of change of the signal at the leading and trailing edges of the analyzed pulse, means for determining the asymmetry of its shape, means for determining the pulse width, means for comparing the mentioned values ​​with the established limits for generating a signal that the analyzed pulse belongs to the signal of the physical component of the electrodermal activity.

11. The device according to claim 7, characterized in that the low-pass filter, the block for converting the input signal into the first and second time derivatives, and the block for analyzing the shape of the pulses are made on the basis of a computer connected to the input device via an analog-to-digital converter.

However, modern psychophysiology was born when the French physician Feret first noticed that the electrical properties of the skin change in emotional situations. We now know that Feret indirectly observed the activity of the sweat glands.

A person has 2 - 3 million sweat glands, but their number in different parts of the body varies greatly. For example, on the palms and soles there are about 400 sweat glands per 1 cm of the skin surface, on the forehead - about 200, on the back - about 60. The secretion of sweat glands occurs constantly, even when not a drop appears on the skin. During the day, about half a liter of fluid is released. In extreme heat, fluid loss can reach 3.5 l / h.
There are two types of sweat glands: apocrine and eccrine.

Apocrine Sweat glands, located in the armpits and groin, detect body odor and respond to stressful stimuli. They do not affect the regulation of body temperature.

eccrine sweat glands are located all over the surface of the body and secrete ordinary sweat, the main components of which are water and sodium chloride. Them main function- thermoregulation, i.e. maintaining constant temperature body. Heat is generated during muscle contraction and metabolism. Our body strives to maintain the internal temperature at a constant level of about 36-37 ° C by giving off heat with the exhaled air and through the skin. One of the means of increasing skin heat transfer is thermoregulatory sweating.

All these reactions are controlled by the reflex center, which is located in the hypothalamus and responds to blood temperature. Reflex sweating occurs automatically before the body is at risk of overheating.

Other eccrine glands respond less to changes in temperature than to external stimuli and stress. These sweat glands are concentrated on the palms and soles and, to a lesser extent, on the forehead and under the armpits. The division of the glands is not absolute, but relative. In conditions of intense heat, the "emotional" glands can respond to it, and in conditions of extreme stress, the thermoregulatory glands can also respond to it.

Background

In 1888, Dr. Feret described the following case. A patient with hysterical anorexia, whom he tactfully refers to as "Madame X," complained of electrical tingling sensations in her hands and feet. Feret noticed that these sensations intensified when the patient inhaled some smell, looked at a piece of colored glass, or listened to the sound of a tuning fork. We do not know whether the patient's tingling in the extremities ceased, but during the course of the examination Feret found that when a weak current was passed through the forearm, there were systematic changes in the electrical resistance of the skin. Two years later, Tarkhanov independently showed that similar electrical shifts can be observed without the application of an external current. Thus, he discovered the skin potential and, in addition, established that this potential changes both during internal experiences and in response to sensory stimulation.

Currently, EAK combines a number of indicators: skin potential level, skin potential response, spontaneous skin potential response, skin resistance level, skin resistance response, spontaneous skin resistance response. Skin conductivity characteristics have also been used as indicators: level, response, and spontaneous response. In all three cases, "level" means the tonic component of the EAA, i.e. long-term changes in indicators; "reaction" - the phasic component of the EAC, i.e. fast, situational changes in EAK indicators; spontaneous reactions - short-term changes that do not have a visible connection with external factors.
Origin and meaning of EAK. The electrical activity of the skin is mainly due to the activity of the sweat glands in the human skin, which in turn are under the control of the sympathetic nervous system.

In psychophysiology, the electrical activity of the skin is used as an indicator of "emotional" sweating. As a rule, it is recorded from the tips of the fingers or palm, although it can be measured from the soles of the feet, and from the forehead.

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• - "... - connection electrical circuits by means of an electric field in a conducting medium..." Source: "ELECTROTECHNIKA. TERMS AND DEFINITIONS OF BASIC CONCEPTS ...

  Official terminology

• - Electric, or galvanic P., otherwise - P. of electrodes, is called that special resistance, which, in addition to resistance, electric current undergoes when it passes through the one in the circuit ...
• - Electric, or galvanic P., otherwise - P. of electrodes, that special resistance is called, which, in addition to resistance, electric current undergoes when it passes through the one in the circuit of this ...

  encyclopedic Dictionary Brockhaus and Euphron

• - an apparatus for applying galvanic coatings to the surface of a product, as well as for manufacturing products by a galvanoplastic method. See Electroplating...

  Great Soviet Encyclopedia

• - A device used to excite an electric current, consisting of copper and zinc plates immersed in weak solution vitriol oil and interconnected over the liquid with copper wire ...

  Dictionary of foreign words of the Russian language

"galvanic reaction" in books

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