Lability is a concept used to describe mobility. The area of application may slightly change the semantic characteristics, indicating both the number of nerve impulses transmitted per unit of time by the cell, and the speed of starting and stopping mental processes.
Lability characterizes the rate of occurrence (from the onset of reaction to inhibition) of elementary processes, and is measured by the highest frequency of impulse reproduction without changes in tissue function and the time of functional recovery. This indicator is not considered a constant value, since it can change from external factors (heat, time of day, force), the effects of chemicals (produced by the body or consumed) and emotional states, so it is only possible to observe the dynamics and predisposition of the body, the prevailing level. It is the change in lability indicators that is key in the diagnosis of various diseases and norms.
What is lability
In scientific applications, lability is used synonymously with mobility (normally), instability (in pathology) and variability (as a characteristic of the dynamics of a state and processes). To understand the breadth of use of this term, we can consider examples of the fact that there is lability of mood in body temperature, psyche and physiology, and accordingly applies to all processes that have speed, constancy, rhythm, amplitude and other dynamic characteristics in their indicators.
The course of any body processes is regulated by the nervous system, therefore, even when talking about indicators of pulse or mood lability, we are still talking about the degree of lability of the nervous system (central or autonomic, depending on the location of instability). The autonomic nervous system regulates internal organs and systems; accordingly, the general condition of the body depends on its work, the ability to maintain rhythm and stability of processes.
Autonomic lability brings disturbances in the functioning of the heart (manifestations are in the form of arrhythmia, problems with blood pressure and quality), the functioning of the glands (problems with sweating or the production of substances necessary for the quality functioning of the body may begin). Many seemingly psychological problems or those related to the central nervous system are actually solved at the level of reducing autonomic lability, which ensures productive sleep and the absorption of beneficial microelements. At the same time, it is worth remembering that signaling about the level of stress or a critical emotional situation is primarily not the central system, but the autonomic system, by increasing its lability. Mechanisms that activate the work of all organ systems to overcome difficult or extreme situations use the body’s internal reserves, forcing the heart to speed up the rhythm, the lungs to absorb more air, the iron to remove excess adrenaline through sweat, and only then the central nervous system reactions are activated.
Lability of the nervous system or mental lability is characterized by a pathological state of mood disturbance, expressed in its swings and inconstancy. The condition may be normal for adolescence, but is classified as a spectrum of pathological conditions for adults and requires medical care, as well as the work of a psychologist, even without prescribing medications.
Lability in psychology
Mental lability, considered in psychology, implies its mobility, and in some cases instability, while science itself studies only this aspect of lability, without going into physiology. In most sources, mental lability is viewed as a negative quality that requires correction, but it does not give due credit to the fact that this is the main adaptive mechanism of the psyche. It was the speed of reaction and switching between quickly and often unexpectedly changing events in external life that helped humanity survive. The opposite is the psyche, when a person remains constant for a long time, and any changes knock him out of his normal state. Any of these characteristics in its extreme manifestation is negative, but at moderate levels it has its advantages.
Problems with lability, when a person comes to a psychologist, are associated with frequent changes in mood, while all spectrums are experienced not superficially, but really deeply (i.e., if you feel sad, then you think about opening your veins, and if you are happy, then you want to dance on workplace and give candy to passers-by - and all this within one hour). It is precisely the difficulties in coping with one’s own and the lack of understanding of how this can be corrected that brings many not only mental suffering, but the subsequent changes in health, since the autonomic system, being subordinate to emotional states, also increases the level of its lability.
Such phenomena can be justified by the type of organization of the nervous system, so in people with the speed of reactions is already determined by nature, and accordingly, an increase in lability to a pathological state is more likely. Mood swings can also be triggered by frequent exposure to traumatic situations at an early age. But we should not exclude physiological reasons that affect a person’s psychological state: brain tumors, TBI, vascular diseases.
Correction of such unpleasant conditions begins with diagnosis and exclusion of physiological causes, then, if necessary, correction is possible with mood-stabilizing drugs (antidepressants and tranquilizers), accompanied by a course of psychotherapy. In severe cases, treatment in a hospital may be appropriate; in the mildest cases, you can cope by visiting a psychologist, without interrupting your usual life.
Lability in physiology
In physiology, lability is considered as a property of tissue that characterizes its change during prolonged excitation. Reactions to prolonged excitation can be expressed in three types of response: a response to each impulse, transformation of the original rhythm into a rarer one (for example, a response to every third impulse) or cessation of the response. For each cell of the body, this rhythm is different, and it may differ from the rhythm of the organ consisting of these cells, as well as from the rhythm of the entire organ system. The faster the tissue reacts to irritation, the higher its lability is considered, but there are few indicators of only this time; it is also necessary to take into account the time required for recovery. Thus, the reaction can be quite fast, but due to the long recovery time, the overall lability will be quite low.
Lability increases or decreases depending on the needs of the body (the normal option, without diseases, is considered), and it can increase from the metabolic rate, which forces all systems to speed up the rhythm of work. An increase in lability has been noticed, that when the body is in a working active state, i.e. The lability of your tissues is much higher if you run than if you read while lying down, and the indicators remain at an increased value for some time after the cessation of vigorous activity. Such reactions are associated with the assimilation of a rhythm that meets current environmental conditions and activity needs.
The regulation of physiological lability can also be addressed in case of disorders of the psychological spectrum, since many conditions have as their root cause not mental disorders or emotional experiences, but physiological disorders. For example, a physiological effect can eliminate sleep problems, which will automatically increase the level of attention and reduce sleep, the treatment of which would be ineffective without taking into account physiological indicators.
Intellectual lability
Intellectual lability is one of the components of the lability of the nervous system and is responsible for the processes of switching between the processes of activation and inhibition. In life, this looks like a fairly high level of mental development and the ability to logically analyze incoming information. Since a critically huge number of information blocks requiring information is received every second, there is a need to sort them as quickly as possible (at a subconscious automatic level) into significant and insignificant.
The presence of a large knowledge base becomes irrelevant and testifies not to knowledge, but to erudition; much more significant is the ability to switch between different sources of information, between different information in meaning, and also to move on to solving the next (albeit opposite) problem in the shortest possible time . At this switching speed, the main thing is to maintain the ability to highlight the main thing for the task at a given time. It is precisely this process of intellectual work that ensures high intellectual lability.
Previously, they did not know about this property, then they talked about it, but rarely, and now, when the pace of life is accelerating, the amount of information consumed is growing at such a pace that a person who lived two hundred years ago would have needed a month to realize that we process within an hour , this becomes a determining factor for success. This gives the ability to respond adequately and as usefully as possible in changing conditions, promotes instant analysis of many factors, which allows minimizing the possibility of error.
In addition, quickly switching between different topics and issues provides innovative thinking, new ways to solve old problems, and rapid assimilation of knowledge and skills, and this happens at a deeper level. For example, historical data on the same event, gleaned from different sources (here one cannot do without using the capabilities of the modern world) provides a more objective and comprehensive understanding than citing the point of view of the author of the textbook. The ability to learn quickly is due to the fact that there is no need to tune in to the arrival of material - ten minutes of reading an article in a minibus, accompanied by listening to new music, or writing a thesis with breaks to watch educational videos becomes a familiar way of functioning, providing new opportunities.
Emotional lability
Mood lability, which is the main reflection of emotional lability, is the variability of the mood pole, often without expressed reasons for this. The nervous system is responsible for our emotional state, and when it is weakened, it becomes hypersensitive, which explains the instant and strong reaction to even minor stimuli. The color can be anything - either happiness or sadness; aggressive affects and apathetic sadness arise with equal ease.
Symptoms may include spontaneity of actions, impulsiveness, lack of ability to predict the consequences of one’s own actions. The occurrence of affective outbursts and uncontrollable states for minor or absent reasons was the reason for including emotional lability in the lists of psychiatric disorders requiring stabilization under medical supervision. It may also not be a separate disease, but a symptom of more dangerous and complex ones (severe tumors, problems with blood pressure, hidden consequences of traumatic brain injuries, etc.). It is difficult to diagnose in childhood, since it has been little studied and is often confused with, so diagnosis requires a team of specialists from a psychiatrist, psychologist and neurologist.
Emotional instability manifests itself in restlessness, lack of patience and acute reaction to criticism or obstacles, difficulties in establishing logical chains, as well as mood swings. These swings are different from manic-depressive disorder and are characterized by a rapid change of states with the same deep experience of the emotional spectrum.
Any overload of the nervous system contributes to this development of the emotional sphere: emotional stress, psychotraumas or their actualization, hyper- or hypoattention from society, hormonal changes (adolescence and menopause, pregnancy). Physiological reasons: somatic diseases, deficiency of vitamins (especially group B, necessary to maintain the functioning of the nervous system), as well as difficult physical conditions.
If emotional lability is diagnosed, then a psychiatrist should correct it; if the condition is not so dire, then a course of prevention is prescribed by a psychologist. In any case, you should not treat such manifestations with disdain, explaining them as bad character. 
Physiology of excitable tissues studies the basic patterns of interaction between the organism, its components and existing environmental factors.
Excitable tissues- nervous tissue, glandular tissue and muscle tissue specially adapted to carry out rapid responses to the action of a stimulus.
Humans and animals live in a world of light, sounds, smells, gravitational forces, mechanical pressure, variable temperature and other signals from the external or internal environment. Everyone knows from their own experience that we are not only able to instantly perceive these signals (also called stimuli), but also respond to them. This perception is carried out by the structures of nervous tissue, and one of the forms of response to perceived signals is motor reactions carried out by muscle tissue. This chapter will examine the physiological basis of the processes and mechanisms that ensure the body’s perception and response to various signals from the external and internal environment.
The most important specialized tissues of the body, providing the perception of signals and responses to the action of various stimuli, are nervous and muscle tissues, which are traditionally called excitable tissues. However, it is the muscle cells and neurons that are truly excitable in them. Neuroglial cells, of which there are approximately 10 times more in the brain than , do not have excitability.
Excitability- the ability of cells to react in a certain way to the action of a stimulus.
Excitation- an active physiological process, a response of excitable cells, manifested by the generation of an action potential, its conduction and contraction for muscle cells.
Excitability in the evolution of cells developed from the property of irritability inherent in all living cells, and is a special case of irritability.
Irritability- this is a universal property of cells to respond to the action of a stimulus by changing vital processes. For example, neutrophils, having perceived the action of a specific signal - an antigen, with their receptors, stop moving in the blood flow, attach to the capillary wall and migrate in the direction of the inflammatory process in the tissue. The epithelium of the oral mucosa responds to the action of irritating substances by increasing the production and secretion of mucus, and the skin epithelium, when exposed to ultraviolet rays, accumulates a protective pigment.
Excitation is manifested by specific and nonspecific changes recorded in the cell.
Specific manifestation excitation for nerve cells is the generation and conduction of an action potential (nerve impulse) over relatively long distances without reducing its amplitude, and for muscle cells - the generation, conduction of an action potential and contraction. Thus, the key indicator of the occurrence of excitation is the generation of an action potential. A sign of the presence of an action potential is recharging (inversion of the charge sign). In this case, for a short time, the surface of the membrane, instead of the positive one present at rest, acquires a negative charge. In cells that do not have excitability, when exposed to a stimulus, the potential difference on the cell membrane can only change, but this is not accompanied by recharging of the membrane.
To nonspecific manifestations excitations of nerve and muscle cells include changes in the permeability of cell membranes to various substances, acceleration of metabolism and, accordingly, an increase in the absorption of oxygen by cells and the release of carbon dioxide, a decrease in pH, an increase in cell temperature, etc. These manifestations are in many ways similar to the components of the response to the action of a stimulus of non-excitable cells.
Excitation can occur under the influence of signals coming from the external environment, from the cell microenvironment, and spontaneously (automatically) due to changes in the permeability of the cell membrane and metabolic processes in the cell. Such cells are said to have automaticity. Automaticity is inherent in the pacemaker cells of the heart, smooth myocytes of the walls of blood vessels and intestines.
In the experiment, one can observe the development of excitation under the direct influence of stimuli on nervous and muscle tissue. There are irritants (signals) of physical (temperature, electric current, mechanical effects), chemical (neurotransmitters, cytokines, growth factors, taste, odorants) and physicochemical nature (osmotic pressure, pH).
Based on the biological correspondence of stimuli to the specialization of sensory receptors that perceive the effects of these stimuli in the body, the latter are divided into adequate and inadequate.
Adequate stimuli - irritants, to the perception of which the receptors are adapted and react to a low force of influence. For example, light quanta are adequate for photoreceptors and other cells of the retina, the response to which is registered in the photoreceptors of the retina when only 1-4 quanta are absorbed.
Inappropriate stimuli do not cause excitement even with significant force. Only with excessive forces bordering on damage can they cause excitation. Thus, the sensation of sparks of light may occur when struck in the eye area. In this case, the energy of the mechanical, inadequate stimulus is billions of times greater than the energy of the light stimulus that causes the sensation of light.
Conditions of excitable tissue cells
All living cells have irritability, i.e. the ability to respond to various stimuli and move from a state of physiological rest to a state of activity. This process is accompanied by a change in metabolism, and differentiated tissues (nervous, muscle, glandular) that perform specific functions (conducting a nerve impulse, contraction or secretion) are also accompanied by a change in electrical potential.
Excitable tissue cells can be in three different states(Fig. 1). In this case, cells from a state of physiological rest can move into active states of excitation or inhibition, and vice versa. Cells that are in a state of excitation can move into a state of inhibition, and from a state of inhibition - into a state of excitation. The rate at which different cells or tissues transition from one state to another varies greatly. Thus, motor neurons of the spinal cord can move from a resting state to a state of excitation from 200 to 300 times per second, while interneurons can move up to 1000 times.
Rice. 1. The relationship between the basic physiological states of excitable tissue cells
Physiological rest- a condition characterized by:
- relatively constant level of process exchange;
- lack of functional manifestations of the tissue.
Active state occurs under the influence of a stimulus and is characterized by:
- a pronounced change in the level of metabolic processes;
- manifestations of functional tissue functions.
Excitation- an active physiological process that occurs under the influence of a stimulus, facilitating the transition of tissue from a state of physiological rest to specific activity (generation of a nerve impulse, contraction, secretion). Nonspecific signs of excitement:
- change in membrane charge;
- increased metabolic processes;
- increase in energy costs.
Braking- an active physiological process that occurs under the influence of a certain stimulus and is characterized by inhibition or cessation of the functional activity of the tissue. Nonspecific signs of inhibition:
- change in cell membrane permeability;
- change in the movement of ions through it;
- change in membrane charge;
- decrease in the level of metabolic processes;
- reduction in energy costs.
Basic properties of excitable tissues
Any living tissue has the following properties: excitability, conductivity and lability.
Excitability- the ability of tissue to respond to stimuli by transitioning to an active state. Excitability is characteristic of nervous, muscle and glandular tissues. Excitability is inversely proportional to the strength of the current stimulus: B = 1/S. The greater the strength of the current stimulus, the less excitability, and vice versa. Excitability depends on the state of metabolic processes and the charge of the cell membrane. Inexcitability = refractoriness. Nervous tissue has the greatest excitability, followed by striated skeletal and cardiac muscle tissue, and glandular tissue.
Conductivity- the ability of tissue to conduct excitation in two or one direction. An indicator of conductivity is the speed of excitation (from 0.5 to 120 m/s depending on the tissue and fiber structure). Excitation is transmitted most quickly along the myelinated nerve fiber, then through the unmyelinated fiber, and the synapse has the lowest conductivity.
Functional lability- the ability of tissue to reproduce without distortion the frequency of rhythmically applied impulses. An indicator of functional lability is the number of impulses that a given structure can transmit without distortion per unit of time. For example, a nerve - 500-1000 impulses/s, a muscle - 200-250 impulses/s, a synapse - 100-120 impulses/s.
The role of the force of irritation and the time of its action. Chronaxia - this is a temporary characteristic of excitability. The relationship between the threshold intensity of stimulation and duration is called duration force curve or Goorweg-Weiss curve(Fig. 2). It has the shape of an equilateral hyperbola. Time is plotted on the abscissa axis, and the threshold intensity of stimulation is plotted on the ordinate axis.
Rice. 2. Duration force curve (Goorweg - Weiss)
The abscissa axis represents time (t); along the ordinate - threshold intensity of stimulation (i); 0A - rheobase: 0B - double rheobase: OD - chropaxy; 0J - useful time
From Fig. 2 it can be seen that if the intensity of stimulation is too low (less than OA), the response does not occur at any duration. There is no reaction even if the duration of the stimulus is too short (less than OG). When the intensity of stimulation corresponds to the segment OA, excitation occurs under the condition of a longer duration of action of the irritating impulse. Within the time period determined by the OB segment, there is a relationship between the threshold intensity and the duration of stimulation: a shorter duration of the irritating impulse corresponds to a greater threshold intensity (the OD segment corresponds to OB, and OE corresponds to the OB segment). Beyond this time (TO), changing the duration of the stimulus no longer affects the value of the irritation threshold. The shortest time during which the relationship between the threshold intensity of stimulation and its duration appears is called useful time(coolant segment). Useful time is a temporary measure of arousal. By its value one can judge the functional state of various excitable formations. However, to determine the useful time, it is necessary to find several points on the curve, which requires applying a lot of irritations. Therefore, the definition of another time indicator, which was introduced into the practice of physiological research by L. Lap i k (1907), has become widespread. He proposed the following parameters to characterize the rate of occurrence of the excitation process: rheobase And chronaxia.
Rheobase— this is the threshold intensity of irritation for a long duration of its action (segment OA); chronaxia - the time during which a current equal to double rheobase (RB) must operate to obtain a threshold response (segment RD). During this time, the membrane potential decreases to a value corresponding to the critical level of depolarization. For different excitable formations, the magnitude of chronaxy is not the same. Thus, the chronaxy of the human ulnar nerve is 0.36 ms, the median nerve is 0.26 ms, the common digital flexor is 0.22 ms, and the common extensor is 0.58 ms.
M. Weiss formula
where I is the threshold current; t is the duration of the stimulus (s); a is a constant characterizing the constant time of stimulation from the moment when the curve turns into a straight line running parallel to the ordinate axis; b is a constant corresponding to the strength of stimulation at a constant duration, when the curve crosses a line running parallel to the abscissa axis.
Excitability indicators
To assess the state of excitability in humans and animals, a number of its indicators are studied in an experiment, which indicate, on the one hand, what stimuli the excitable tissue reacts to, and on the other, how it reacts to influences.
The excitability of nerve cells is usually higher than that of muscle cells. The level of excitability depends not only on the type of cell, but also on numerous factors affecting the cell and especially the state of its membrane (permeability, polarization, etc.).
The indicators of excitability include the following.
Stimulus strength threshold- this is the minimum strength of the current stimulus sufficient to initiate excitation. Stimuli whose strength is below the threshold are called subthreshold, and those whose strength is above the threshold are called supra- or superthreshold.
There is an inverse relationship between excitability and the magnitude of the force threshold. The more an excitable cell or tissue reacts to a lesser impact by developing excitation, the higher its excitability.
The excitability of tissue depends on its functional state. With the development of pathological changes in tissues, their excitability can decrease significantly. Thus, measuring the threshold of stimulus strength has diagnostic significance and is used in the electrodiagnosis of diseases of the nervous and muscle tissues. One of its examples can be the electrodiagnosis of dental pulp diseases, called electroodontometry.
Electroodontometry (electroodontodiagnosis) is a method of using electric current for diagnostic purposes to determine the excitability of the nervous tissue of teeth (sensory receptors of the sensitive nerves of the dental pulp). The dental pulp contains a large number of sensitive nerve endings that respond to certain mechanical, temperature and other influences. Electroodontometry determines the threshold for feeling the action of electric current. The electric current threshold for healthy teeth is 2-6 µA. with medium and deep caries - 10-15, acute pulpitis - 20-40, with the death of the coronal pulp - 60, with the death of the entire pulp - 100 μA or more.
The magnitude of the threshold force of irritation of excitable tissue depends on the duration of exposure to the stimulus.
This can be tested experimentally by applying electric current pulses to excitable tissue (nerve or muscle), observing at what values of the strength and duration of the electric current pulse the tissue responds with excitation, and at what values excitation does not develop. If the duration of exposure is very short, then excitation in the tissue may not occur even with superthreshold exposures. If the duration of the stimulus is increased, the tissue will begin to react with excitation to lower-strength impacts. Excitation will occur with the least powerful impact if its duration is infinite. The relationship between the force threshold and the stimulation time threshold sufficient for the development of excitation is described by the force-duration curve (Fig. 3).
Rice. 3. Force-duration curve (the ratio of force and duration of exposure necessary for the occurrence of excitation). Below and to the left of the curve are the ratios of the strength and duration of the stimulus, insufficient for excitation; above and to the right are sufficient
The concept of “rheobase” was introduced specifically to characterize the threshold of electric current, which is widely used as a stimulus in the study of tissue responses. Rheobase- this is the minimum electric current required to initiate excitation, with prolonged exposure to a cell or tissue. Further prolongation of stimulation has virtually no effect on the magnitude of the threshold force.
Irritation time threshold- the minimum time during which a stimulus of threshold strength must act to cause arousal.
There is also an inverse relationship between excitability and the time threshold. The tissue reacts to shorter threshold influences with the development of excitation, the higher the excitability. The threshold time for excitable tissue depends on the strength of the stimulus, as can be seen in Fig. 3.
Chronaxia - the minimum time during which a stimulus with a force equal to two rheobases must act in order to cause excitation (see Fig. 3). This excitability indicator is also used when electric current is used as a stimulus. The chronaxy of nerve cells and skeletal muscle fibers is ten thousandths of a second, and that of smooth muscles is tens of times greater. Chronaxy as an indicator of excitability is used to test the condition and functionality of skeletal muscles and nerve fibers of a healthy person (in particular, in sports medicine). Determining chronaxy is valuable for diagnosing a number of diseases of muscles and nerves, since in this case the excitability of the latter usually decreases and chronaxy increases.
Minimum gradient (steepness) increase in the strength of the stimulus over time. This is the minimum rate of increase in stimulus strength over time sufficient to initiate excitation. If the strength of the stimulus increases very slowly, then the tissue adapts to its action and does not respond with excitation. This adaptation of excitable tissue to a slowly increasing stimulus strength is called accommodation. The greater the minimum gradient, the lower the excitability of the tissue and the more pronounced its ability to accommodate. The practical significance of this indicator lies in the fact that when carrying out various medical manipulations in a person, in some cases it is possible to avoid the development of severe pain and shock conditions by slowly changing the rate of increase in force and the time of exposure.
Lability- functional mobility of excitable tissue. Lability is determined by the rate of elementary physicochemical transformations underlying a single excitation cycle. A measure of lability is the maximum number of cycles (waves) of excitation that a tissue can generate per unit time. Quantitatively, the magnitude of lability is determined by the duration of a single cycle of excitation and the duration of the phase of absolute refractoriness. Thus, interneurons of the spinal cord can reproduce more than 500 cycles of excitation or nerve impulses per second. They have high lability. Motor neurons that control muscle contraction are characterized by lower lability and are capable of generating no more than 100 nerve impulses per second.
Potential difference (ΔE) between the resting potential on the membrane (E 0) and critical level of depolarization membranes (E k). ΔE = (E 0 - E k) is one of the most important indicators of cell excitability. This indicator reflects the physical essence of the stimulus strength threshold. A stimulus is threshold in the case when it is capable of shifting such a level of membrane polarization to E k, upon reaching which an excitation process develops on the membrane. The lower the ΔE value, the higher the excitability of the cell and the weaker influences it will respond with excitation. However, the ΔE indicator is difficult to measure under normal conditions. The physiological significance of this indicator will be considered when studying the nature of membrane potentials.
Laws of response of excitable tissues to irritation
The nature of the response of excitable tissues to the action of stimuli is classically described by the laws of irritation.
Law of force irritation states that when the strength of the suprathreshold stimulus increases to a certain limit, the magnitude of the response also increases. This law is applicable to the contraction response of an integral skeletal muscle and the total electrical response of nerve trunks, which include many fibers with different excitability. Thus, the force of muscle contraction increases with increasing strength of the stimulus acting on it.
For the same excitable structures, the law of stimulation duration and the law of stimulation gradient are applicable. Law of duration of irritation states that the longer the duration of suprathreshold stimulation, the greater the magnitude of the response. Naturally, the answer increases only up to a certain limit. Law of irritation gradient - the greater the gradient of increase in the strength of the stimulus over time, the greater (up to a certain limit) the magnitude of the response.
All or nothing law states that under the action of subthreshold stimuli, excitation does not occur, and under the action of threshold and suprathreshold stimuli, the magnitude of the response due to excitation remains constant. Consequently, already to a threshold stimulus, the excitable structure responds with the maximum possible reaction for a given functional state. A single nerve fiber is subject to this law, on the membrane of which an action potential of equal amplitude and duration is generated in response to the action of threshold and suprathreshold stimuli. The “all or nothing” law governs the reaction of a single skeletal muscle fiber, which responds with action potentials of equal amplitude and duration and the same force of contraction to both threshold and suprathreshold stimuli of different strengths. The nature of contraction of the entire muscle of the ventricles of the heart and atria is also subject to this law.
Law of polar action of electric current (Pfluger) postulates that when excitable cells are exposed to a direct electric current at the moment of circuit closure, excitation occurs at the point of application of the cathode, and when opened, at the point of contact with the anode. In itself, the prolonged action of direct current on excitable cells and tissues does not cause excitation in them. The impossibility of initiating excitation by such a current can be considered as a consequence of their accommodation to a stimulus that does not change in time with a zero slope of increase. However, since the cells are polarized and there is an excess of negative charges on their inner surface, and positive charges on the outer surface, then in the area of application of the anode (positively charged electrode) to the tissue under the influence of an electric field, part of the positive charges represented by K+ cations will move inside the cell and their the concentration on the outer surface will become less. This will lead to a decrease in the excitability of cells and the tissue area under the anode. The opposite phenomena will be observed under the cathode.
The effect of electric current on living tissues and recording of bioelectric currents are often used in medical practice for diagnosis and treatment, and especially when conducting experimental physiological studies. This is due to the fact that the values of biocurrents reflect the functional state of tissues. Electric current has a therapeutic effect, it is easily dosed in terms of magnitude and time of exposure, and its effects can be observed at impact forces close to the natural values of biocurrents in the body.
Functional mobility) in physiology - the rate of elementary physiological processes in excitable tissue, defined, for example, as the maximum frequency of stimulation that it is capable of reproducing without rhythm transformation.
1. Small medical encyclopedia. - M.: Medical encyclopedia. 1991-96 2. First aid. - M.: Great Russian Encyclopedia. 1994 3. Encyclopedic Dictionary of Medical Terms. - M.: Soviet Encyclopedia. - 1982-1984.
Synonyms:See what “Lability” is in other dictionaries:
- (from Lat. labilis sliding, unstable) in physiology, functional mobility, the speed of elementary cycles of excitation in nervous and muscle tissues. The concept of “lability” was introduced by a Russian physiologist... ... Wikipedia
lability- (from Latin labilis sliding, unstable) the maximum number of impulses that a nerve cell or functional structure can transmit per unit of time without distortion. The term was proposed by N. E. Vvedensky. In differential psychology L. one thing... ... Great psychological encyclopedia
- (from Lat. labilis sliding unstable), 1) functional mobility of nervous and muscle tissue, characterized by the highest frequency with which the tissue can be excited in the rhythm of stimulation. The highest lability is in thick nerves... ... Big Encyclopedic Dictionary
Instability, mobility Dictionary of Russian synonyms. lability noun, number of synonyms: 4 variability (23) ... Dictionary of synonyms
LABILE, oh, oh; flax, linen (book). Mobile, unstable. Labile pressure. Labile temperature. Ozhegov's explanatory dictionary. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 … Ozhegov's Explanatory Dictionary
- (from lat. labilis sliding, unstable) (physiol.), functional mobility, the property of excitable tissue to reproduce without distortion the frequency of applied rhythmic movements. irritations. Measure L. max, the number of impulses that a given structure can transmit... ... Biological encyclopedic dictionary
- (from Latin labilis sliding, unstable), 1) functional mobility of nervous and muscle tissue, characterized by the highest frequency with which the tissue can be excited in the rhythm of stimulation. The highest lability is in thick nerves... ... Encyclopedic Dictionary
- (lat. labilis mobile, unstable; synonym: functional lability, functional mobility) in physiology, the speed of elementary physiological processes in excitable tissue, defined, for example, as the maximum frequency... ... Large medical dictionary
- (from Lat. labilis sliding, unstable) (physiol.), functional mobility, the speed of elementary cycles of excitation in nervous and muscle tissues. The concept of "L." introduced by the Russian physiologist N. E. Vvedensky (See Vvedensky) ... ... Great Soviet Encyclopedia
lability- labilumas statusas T sritis chemija apibrėžtis Greitas kitimas keičiantis sąlygoms. atitikmenys: engl. lability rus. lability; instability... Chemijos terminų aiškinamasis žodynas
lability- labilumas statusas T sritis fizika atitikmenys: engl. lability vok. Labilität, f rus. lability, f pranc. labilité, f … Fizikos terminų žodynas
Books
- Typology of labile verbs, Letuchy Alexander Borisovich. The book uses typological material to examine labile verbs - verbs that can be both transitive and intransitive without changing their form. Lability has not yet been studied by linguistics in...
Lability
(from lat. labilis - slippery, sliding, unstable)
1) (in biology) instability, variability, functional mobility of nervous and muscle tissue, characterized by the highest frequency of excitation under the influence of stimuli (the highest of which is in thick nerve fibers - up to 500-600 impulses per second);
2) high adaptability or, conversely, instability of the body to environmental conditions;
3) (in chemistry) high mobility, the ability of certain chemical elements to form numerous bonds with other elements (for example, the ability of carbon to combine with other atoms, which determined the carbon-based nature of life on Earth). Labile - unstable, prone to change.
The beginnings of modern natural science. Thesaurus. - Rostov-on-Don. V.N. Savchenko, V.P. Smagin. 2006 .
Synonyms:See what “Lability” is in other dictionaries:
Lability- (from Lat. labilis sliding, unstable) in physiology, functional mobility, the speed of elementary cycles of excitation in nervous and muscle tissues. The concept of “lability” was introduced by a Russian physiologist... ... Wikipedia
lability- (from Latin labilis sliding, unstable) the maximum number of impulses that a nerve cell or functional structure can transmit per unit of time without distortion. The term was proposed by N. E. Vvedensky. In differential psychology L. one thing... ... Great psychological encyclopedia
LABILITY- (from Lat. labilis sliding unstable), 1) functional mobility of nervous and muscle tissue, characterized by the highest frequency with which the tissue can be excited in the rhythm of stimulation. The highest lability is in thick nerves... ... Big Encyclopedic Dictionary
lability- instability, mobility Dictionary of Russian synonyms. lability noun, number of synonyms: 4 variability (23) ... Dictionary of synonyms
lability- LABILE, oh, oh; flax, linen (book). Mobile, unstable. Labile pressure. Labile temperature. Ozhegov's explanatory dictionary. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 … Ozhegov's Explanatory Dictionary
LABILITY- (from lat. labilis sliding, unstable) (physiol.), functional mobility, the property of excitable tissue to reproduce without distortion the frequency of applied rhythmic movements. irritations. Measure L. max, the number of impulses that a given structure can transmit... ... Biological encyclopedic dictionary
lability- (from Latin labilis sliding, unstable), 1) functional mobility of nervous and muscle tissue, characterized by the highest frequency with which the tissue can be excited in the rhythm of stimulation. The highest lability is in thick nerves... ... Encyclopedic Dictionary
lability- (lat. labilis mobile, unstable; synonym: functional lability, functional mobility) in physiology, the speed of elementary physiological processes in excitable tissue, defined, for example, as the maximum frequency... ... Large medical dictionary
Lability- (from Lat. labilis sliding, unstable) (physiol.), functional mobility, the speed of elementary cycles of excitation in nervous and muscle tissues. The concept of "L." introduced by the Russian physiologist N. E. Vvedensky (See Vvedensky) ... ... Great Soviet Encyclopedia
lability- labilumas statusas T sritis chemija apibrėžtis Greitas kitimas keičiantis sąlygoms. atitikmenys: engl. lability rus. lability; instability... Chemijos terminų aiškinamasis žodynas
lability- labilumas statusas T sritis fizika atitikmenys: engl. lability vok. Labilität, f rus. lability, f pranc. labilité, f … Fizikos terminų žodynas
Books
- Typology of labile verbs, Letuchy Alexander Borisovich. The book uses typological material to examine labile verbs - verbs that can be both transitive and intransitive without changing their form. Lability has not yet been studied by linguistics in...
