The concept of a reflex is very important in physiology. With the help of this concept, the automated work of the body to quickly adapt to changes in the environment is explained.
With the help of reflexes, the nervous system coordinates the activity of the body with signals coming from the external and internal environment.
The position of the receptor and effector in different organs, as an external reflex. These R., which do not obey the will, are innate and allow animals and people to quickly adapt to special conditions. environment, as well as the coordinated interaction of all parts of the body with the simultaneous advantage of releasing the conscious functions of the central nervous system.
Accordingly, the reflex time, i.e. the reaction time as the period between exposure to the stimulus and the reaction is relatively short, but for individual reflexes it has a different length. It is the shortest in the monosynaptic reflex and the longest in some autonomic reflexes in which relatively slow, smooth muscles or glands act effectively. In the language of learning theory, these unconditioned reflexes are compared with conditioned reflexes. Reflex: patellar tendon reflex as an example of a monosynaptic reflex.
Reflex (reflection) is the basic principle and way of working of the nervous system. More general concept - reactivity . These concepts imply that the reason for the behavioral activity of the organism lies not in the psyche, but outside the psyche , outside the nervous system, and is triggered by signals external to the psyche and the nervous system - stimuli. Also implied determinism , i.e. predetermination of behavior due to a causal relationship between the stimulus and the body's response to it.
Hitting the knee, the patella disc is slightly pulled down, and the muscles with the quadriceps muscle are easily stretched. Muscle spindles, which are also stretched in the quadriceps muscle, lead to excitation of sensory nerve cells. Excitation is directed to the spinal cord and is transmitted to the motor nerve fibers, which, in turn, are in contact with the muscle fibers of the quadriceps. Excitation coming to the end plate of the motor leads to a contraction of the quadriceps muscle, which occurs when the nose of the lower leg moves.
Elke Brechner Dr. Scientific supervisors: professor dr Helmut Koenig, Institute for Microbiology and Wine Research, Johannes Gutenberg-Mainz. Walter Sudhaus, Institute of Zoology, Free University, Berlin. Wilfried Wichard, Institute for Biology and its Didactics, University of Cologne.
The concepts of "reflex" and "reflex arc" belong to the field of physiology of the nervous system and they must be understood to the level of complete understanding and clarity in order to understand many other topics and sections of physiology.
Concept definition
A simple definition of the concept of "reflex"
Reflex is responsiveness. It is possible to give such a definition to the reflex, but after that it is necessary to name 6 important criteria (signs) of the reflex that characterize it. They are indicated in the full definition of the concept of reflex below.
Essay authors: Thomas Beerus, Kulmbach Dr. Daniel Diersmann, Cologne Inke Drosse, Prof. Neubiberg Manfred Jake, Prof. Karlsruhe Gerhard Eisenbeis, Mainz, Germany. Wilfried Wichard, Cologne. The reflex consists in a neural mediated, involuntary, fast and similar reaction of the body to a specific stimulus. Reflexes can be complex, congenital or acquired, from a simple reflex arc to "higher" reflexes; in the latter case, they also speak of learned, acquired, conditioned reflexes.
Congenital or unconditioned reflexes are biologically determined reactions. They are interpreted as evolutionary adaptation to living conditions. Reflexes enable living beings to live in a long-term, permanent environment: through an automatic, schematic, or stereotyped response that is adapted to such living conditions, which, under constant circumstances, is sufficient to meet sexual maturity and produce offspring. In short, reflexes do not depend on the will and are combined with feedback.
Reflex is a stereotyped automated adaptive responsiveness to a stimulus (stimulus).
Reflex in the general broad sense is secondary a phenomenon caused by another phenomenon (primary), i.e. reflection, a consequence in relation to something original. In physiology, a reflex is responsiveness the body to an incoming signal, the source of which is outside the psyche, when the triggering signal (stimulus) is the primary phenomenon, and the reaction to it is secondary, reciprocal.
They are characterized by fast response as defense mechanism and influence various bodily functions. The prerequisite for the emergence of reflexes is the ability of the body to make perceptions, process them automatically and develop in exactly the same interaction of the sense organs, nerves and muscles, specific stimuli, reactive reactions that allow or ensure independent life. Genetically fixed and reflexive responses are quasi-evolutionary "tried and tested" responses; they form only in living beings in which they have proven effective in their lives in relation to long-term permanent living conditions.
Full definition of the concept of "reflex"
Physiological definition of the concept of "reflex arc"
reflex arc - this is a schematic path of movement of excitation from the receptor to the effector.
We can say that this is the path of nervous excitation from the place of its birth to the place of application, as well as the path from the information input to the information output from the body. That's what a reflex arc is in terms of physiology.
With innate reflexes, a living being has adaptive and survival skills that do not need to be learned by oneself. Behavioral biologists distinguish the following types of reflexes. Unconditioned, unconditioned or inborn reflexes: they are either already fully developed with the birth of a living being, or develop in the process of their development to puberty and growth; typical of such biologically oriented responses is that each individual exhibits a variety of identical responses and responses to similar constellations of stimuli that vary only in appropriate intensity like speed or violence.
Anatomical definition of the concept of "reflex arc"
reflex arc - this is a set of nervous structures involved in the implementation of the reflex act.
Both of these definitions of the reflex arc are correct, but for some reason the anatomical definition is used more often, although the concept of the reflex arc refers to physiology, not anatomy.
An example is the century reflex. Conditioned or conditioned reflexes: called reflex reactions that are not innate, but have been studied. They are also referred to as acquired reflexes. In this form of learning, visceral reactions can also be conditioned; The Russian scientist Ivan Petrovich Pavlov was especially interested in studying this phenomenon. An example of this is his famous dog experiment: some dogs were given a bell at the same time they were given food. After a while, the dogs began to digest the discharge even when they heard the sound of the bell.
Remember that the diagram of any reflex arc must begin with stimulus , although the stimulus itself is not part of the reflex arc. The reflex arc ends with an organ- effector , which gives a response.
Stimulus - this is such a physical factor that, when exposed to sensory receptors adequate for it, generates nervous excitation in them.
A simple definition of the concept of "reflex"
Initially, the neutral bell seemed to suggest the same trigger function in dogs as the food itself; in such cases it is also said that the feeding and the bell were connected and calls such teaching classical education. Individual reflexes are called reflexes in which the stimulus and the reflex response occur in the same organ. An example of a self-reflex is the well-known patellar or patellar tendon reflex, which can be elicited by a short blow just below the knee to the relaxed quadriceps femoris tendon.
The stimulus triggers transduction in the receptors, as a result of which the irritation is converted into excitation.
Electric current is a universal stimulus, since it is able to generate excitation not only in sensory receptors, but also in neurons, nerve fibers, glands and muscles.
Variants of the result of the effect of the stimulus on the body
As a result of the impact, tension stimulators are stimulated in the muscles, muscle spindles and contraction of the quadriceps muscle, which leads to a short-term stretching movement in the knee joint, achieved by a reflex arc connected to the spinal cord. The purpose of such muscle reflexes is to maintain or restore an appropriate posture in the event of impacts from outside or sudden changes in position by counteracting: with a short blow from behind to the knee, the patellar tendon reflex can contribute, for example, to preventing a fall; The same can be said about stumbling.
1. Launching an unconditioned reflex.
2. Triggering a conditioned reflex.
3. Launching an orienting reflex.
4. Launch of the dominant.
5. Launching a functional system.
6. Triggering emotions.
7. Starting the creation of a neural model (in particular, a sensory image), the process of learning / memorization.
8. Launch memories.
There are not so many types of effectors.
In the case of self-reflexes, habituation does not occur, as in the case of external reflexes. Reflex reflexes are called reflexes when the organ sensitive to the stimulus is not the organ that performs the reflex response. An example is the corneal reflex: if the cornea of the eye is irritated by a draft, the eyelids close reflexively. Irritation follows at a point that cannot react due to lack of muscle; and the eyelid, which is activated to protect the cornea, was not irritated on his part. Unlike self-reflexes, reflexes are livable.
Types of effector in:
1) striated muscles of the body (fast white and slow red),
2) smooth muscles of blood vessels and internal organs,
3) external secretion glands (for example, salivary),
4) endocrine glands (for example, adrenal glands).
Accordingly, the responses will be the result of the activity of these effectors, i.e. contraction or relaxation of muscles, leading to movements of the body or internal organs and vessels, or the secretion of glands.
Coordinated reflex movements: These refer to when a stimulus is activated by more or less large muscle groups. These include, for example, the sucking reflex and the infant reflex, two reflexes that, through certain time cannot be released or released again or only under pathological conditions. First of all, however, there are all sensory reactions, that is, as a rule, so-called short-lived, but always so-called feelings in highly coordinated reflex movements, which are reflexively reflected, which can be deliberately influenced or controlled or "controlled" due to precisely this complexity.
The concept of temporary neural connection
"Temporal connection is a set of biochemical, neurophysiological and, possibly, ultrastructural changes in the brain that occur in the process of combining conditioned and unconditioned stimuli and form strictly defined relationships between structural formations that underlie various brain mechanisms. The memory mechanism fixes these relationships, ensuring their retention and reproduction. (Khananashvili M.M., 1972).
To understand what it is, we must first look at the concept. A reflex act is a movement that a person performs involuntarily as a response to a given stimulus. The neural structure that is responsible for controlling this movement is called the reflex arc.
Reflex actions arise due to the ability they have different to generate a synapse in the area spinal cord. Thus, the body responds before the signal reaches the brain. According to which neurons are involved in this process, the reflex arc can have different characteristics.
Meanwhile, the meaning of this tricky definition boils down to the following:
Temporary neural connection is the flexible part subtly reflex arc, which is formed during the development of a conditioned reflex to connect two undoubtedly reflex arcs. It provides for the conduction of excitation between the nerve centers of two different unconditioned reflexes. Initially, one of these two unconditioned reflexes is triggered by a weak stimulus ("conditioned"), and the second is triggered by a strong one ("unconditioned" or "reinforcement"), but when the conditioned reflex has already been developed, the weak conditioned stimulus gets the opportunity to launch a "foreign" unconditioned reaction for due to the transition of excitation from its nerve center to the nerve center of a strong unconditioned stimulus.
When only two neurons act on it, the reflex arc is simple. If more than one is involved, the reflex arc becomes complex. In the latter case, intercalary neurons act between sensory and motor mechanisms. Specifically, the reflex arc is what follows nerve impulses through the body. Take the case of a blow to the knee that causes involuntary movement of the leg. The reflex arc goes from the sensory neuron, which picks up the stimulus, to the motor neuron, which orders the response.
It is important to distinguish between a reflex arc and a reflex act. It is called a reflex arc to a number of structures that make it possible to realize the so-called reflex act. Articulates with the help of reflex arcs a large number of very diverse nervous processes. It is important to emphasize that the reflex act is the fundamental unit of so-called integrated nervous activity, so much so that some scientists consider it to be the circuit from which the other nervous structures of the body arose.
Types of reflex arcs:
1. Elementary (simple) reflex arc of the unconditioned reflex. © 2015-2016 Sazonov V.F. © 2015-2016 kineziolog.bodhy.ru..
This reflex arc is the simplest, it contains only 5 elements. Although the figure shows more elements, we single out 5 main and necessary ones from them: receptor (2) - afferent ("bringing") neuron (4) - intercalary neuron (6) - efferent ("taking out") neuron (7, 8 ) - effector (13).
In each of these pathways, which are responsible for the transmission of nerve impulses and constitute the reflex arc, a number of components can be seen, some of which have been mentioned in the previous paragraphs. Sensory receptors can be different types such as chemoreceptors, mechanoreceptors, photoreceptors, and thermoreceptors.
Needless to say, it is vital to the development of our functions. Autonomic and somatic reflex arcs coexist in it, and although they are similar in certain aspects, their morphological and functional characteristics have differences that need to be known.
It is important to understand the meaning of each arc element. Receptor : converts irritation into nervous excitement. afferent neuron : delivers sensory stimulation to the central nervous system, to the intercalary neuron. Interneuron : transforms the incoming excitement and directs it along the desired path. So, for example, an intercalary neuron can receive sensory ("signal") excitation, and then transmit another excitation - motor ("control"). Efferent neuron : delivers control excitation to the effector organ. For example, motor excitation - on a muscle. Effector carries out a response.
The components with the most similarities between the two arcs are the afferents. The study of efferents, on the other hand, shows that there are two neurons in the somatic reflex arc instead of one: the first is found in the lateral horns of the medullary gray matter or in the brain and is associated with cranial nerves; the second can be found in autonomous ganglia of various types, such as prevertebral, paravertebral, intraorganic, or preorganic. In short, there is a ganglion between the effector organ and the autonomic nerve center.
The figure on the right shows an elementary reflex arc using the example of a knee jerk, which is so simple that it does not even have intercalary neurons.
Pay attention to the fact that on the motor neuron, which ends the reflex arc, many endings of neurons converge, located on different levels nervous system and striving to control the activity of this motor neuron.
4. double sided arc conditional reflex E.A. Hasratyan. It shows that during the development of a conditioned reflex, counter temporary connections are formed and both used stimuli are both conditioned and unconditioned at the same time.
The figure on the right shows an animated diagram of a double conditioned reflex arc. It actually consists of two unconditioned reflex arcs: the left one is an unconditioned blinking reflex to eye irritation air flow(effector - contracting muscle of the eyelid), right - salivary unconditioned reylex to irritation of the tongue with acid (effector - salivary gland that secretes saliva). Due to the formation in the cortex hemispheres In the brain of temporary conditioned reflex connections, effectors begin to respond to irritants that are inadequate for them normally: blinking in response to acid in the mouth and salivation in response to blowing air into the eye.
5. reflex ring ON THE. Bernstein. This diagram shows how the movement is reflexively adjusted depending on the achievement of the goal.
6. Functional system to ensure the expedient behavior of P.K. Anokhin. This diagram shows the management of complex behavioral acts aimed at achieving a useful planned result. The main features of this model: action result acceptor and feedbacks between elements.
7. Double arc of the conditioned salivary reflex. This diagram shows that any conditioned reflex must consist of two reflex arcs formed by two different unconditioned reflexes, tk. each stimulus (conditioned and unconditioned) generates its own unconditioned reflex.
An example of an experiment protocol for the development of a conditioned pupillary reflex to a sound on laboratory lesson
| experience number | UR (conditioned stimulus), inadequate for the pupil | RR (conditioned response) of the pupil | BR (unconditioned stimulus), adequate for the pupil | ROR (unconditioned response) of the pupil | Note |
| Stimuli and responses | Sound (knocking or ringing a bell) | Extension/constriction pupil | Darkness/Light(blackout of one eye) | Extension/constriction pupil | unconditional response to sound
do not register, even if it is. We evaluate only the reaction to blackout. |
| Series 1. Obtaining an unconditional response to darkness in the form of pupil dilation |
|||||
| 1. | (-) | (-) | (+) | (+) | Only BOR is observed |
| … | (-) | (-) | (+) | (+) | Only BOR is observed |
| 10. | (-) | (-) | (+) | (+) | Only BOR is observed |
| Conclusion : An unconditional response of the pupil to an adequate BR (darkness) is constantly manifested. | |||||
| Series 2. Obtaining an indifferent (indifferent) action of an inadequate conditioned stimulus (sound) on the pupil |
|||||
| 1. | (+) | (+) ? | (-) | (+) ?
| |
| 2. | (+) | (+) | (-) | (+) | OER (indicative response) |
| … | (+) | (+) | (-) | (+) | OER (indicative response) |
| 10. | (+) | (-) | (-) | (-) | The stimulus is already indifferent |
| Conclusion : After several repetitions of irritation inadequate for the pupil, OOR disappears and the stimulus becomes indifferent (indifferent). | |||||
| Series 3. Development of a conditioned reflex (conditioned response) | |||||
| 1. | (+) | (-) | (+) | (+) | Only BOR is observed |
| … | (+) | (-) | (+) | (+) | Only BOR is observed |
| 15. | (+) | (+) | (+) | (+) | UOR appears |
| 16. | (+) | (+) | (-) | (-) | RC (conditioned response) occurs even in the absence of BOR (unconditioned response) |
| Conclusion : After a repeated combination of conditioned and unconditioned stimuli, a conditioned response of the pupil appears to a previously indifferent conditioned stimulus (sound). | |||||
| Episode 4 | |||||
| 1. | (+) | (+) | (-) | (-) | |
| … | (+) | (+) | (-) | (-) | CR observed (conditioned response) |
| 6. | (+) | (-) | (-) | (-) | |
| Conclusion : After repeated conditioned stimuli without reinforcement by unconditioned stimuli, the SVR disappears, i.e. the conditioned reflex is inhibited. | |||||
| Series 5. Secondary development (recovery) of an inhibited conditioned reflex | |||||
| 1. | (+) | (-) | (+) | (+) | Only BOR is observed |
| … | (+) | (-) | (+) | (+) | Only BOR is observed |
| 5. | (+) | (+) | (+) | (+) | UOR appears |
| 6. | (+) | (+) | (-) | (-) | UOR (conditioned response) manifests itself in the absence of BR (unconditioned stimulus) and the BOR (unconditioned response) caused by it |
| Conclusion : Secondary production (recovery) of conditioned reflexes occurs faster than the initial production. | |||||
| Series 6. Receiving secondary inhibition of conditioned reflexes (repeated extinction) | |||||
| 1. | (+) | (+) | (-) | (-) | CR observed (conditioned response) |
| … | (+) | (+) | (-) | (-) | CR observed (conditioned response) |
| 4. | (+) | (-) | (-) | (-) | Disappearance of the conditioned response |
| Conclusion: The secondary inhibition of the conditioned reflex is developed faster than its primary inhibition. | |||||
| Designations: (-) - no irritation or reaction, (+) - presence of irritation or reaction | |||||
> Reflex as the basis of nervous activity and reflex arc. The mechanism of formation of a conditioned reflex. Types of reflexes and their classification
Reflex- the main form of activity of the nervous system, the body's response to irritation, carried out with the participation of the nervous system. Perception of irritation from the external and internal environment by receptors, the occurrence of nerve impulses in them, which are transmitted through sensory neurons to the central nervous system, where they enter the intercalary, then to the executive (motor) neurons, and through them to the executive organs.
reflex arc- the path along which nerve impulses pass during the implementation of the reflex. Its integrity is a prerequisite for the functioning of the reflex. Coordinated reflex activity is the result of the interaction in the central nervous system of the processes of excitation and inhibition.
The reflex arc consists of:
receptor - a nerve link that perceives irritation;
afferent link - centripetal nerve fiber - processes of receptor neurons that transmit impulses from sensory nerve endings to the central nervous system;
central link - nerve center (optional element, for example, for an axon reflex);
efferent link - centrifugal nerve fiber that conducts excitation from the central nervous system to the periphery;
effector - an executive body whose activity changes as a result of a reflex.
There are: - monosynaptic, two-neuron reflex arcs; - polysynaptic reflex arcs (include three or more neurons). Pavlov divided reflexes into conditioned and unconditioned.
> Unconditioned reflexes
Unconditioned reflexes- hereditarily transmitted (innate) reactions of the organism, inherent in the whole species. They perform a protective function, as well as the function of maintaining homeostasis.
The main types of unconditioned reflexes: food, protective, indicative, sexual.
An example of a protective reflex is the reflex withdrawal of the hand from a hot object. Homeostasis is maintained, for example, by a reflex increase in breathing with an excess of carbon dioxide in the blood. Almost every part of the body and every organ is involved in reflex reactions.
are formed at birth and persist throughout life. However, they can change under the influence of the disease. Many unconditioned reflexes appear only at a certain age; Thus, the grasping reflex characteristic of newborns fades at the age of 3-4 months.
> Conditioned reflexes
Conditioned reflexes- these are reactions acquired during the individual life of the organism, arising under certain conditions on the basis of unconditioned reflexes. Conditioned reflexes occur during individual development and the accumulation of new skills. The development of new temporary connections between neurons depends on the environmental conditions. Conditioned reflexes are formed on the basis of unconditioned ones with the participation of higher parts of the brain.
The development of the doctrine of conditioned reflexes is associated primarily with the name of IP Pavlov. He showed that a new stimulus can start a reflex reaction if it is presented for some time together with an unconditioned stimulus.
As life experience is acquired, a system of conditioned reflex connections is formed in the cerebral cortex. Such a system is called a dynamic stereotype. It underlies many habits and skills. For example, having learned to skate, bike, we subsequently no longer think about how we move so as not to fall.
Conditioned reflexes are well formed only under certain conditions. The most important of them are:
1. The presence of two stimuli: indifferent (future conditional) and unconditional, which causes the corresponding action of the dog.
2. The use of these stimuli should coincide in time within 0.5-2 seconds.
3. The action of the signal stimulus must precede the action of the unconditioned within 0.5-2 seconds.
4. Multiple repetition of combinations of conditioned and unconditioned stimuli in a certain load and time mode.
5. The nerve centers of the cerebral cortex during the development of a conditioned reflex must be free from other types of activity and must be in an active state.
6. The strength of excitation to the unconditioned stimulus should be greater than to the signal, but not to cause inhibition.
7. Extraneous stimuli that cause an orienting reaction and distraction should be absent.
8. cheerful state of the body;
Conditioned reflexes are formed only if there is sufficient excitability of the centers of these reinforcing reflexes. For example, in the development of food conditioned reflexes in dogs, experiments are carried out under conditions of high excitability of the food center (the animal is in a hungry state).
