Where are the receptors located? Receptors

The article talks about what receptors are, why they serve humans, and, in particular, discusses the topic of receptor antagonists.

Biology

Life on our planet has existed for almost 4 billion years. During this period, incomprehensible to human perception, many things have changed on it and, probably, this process will continue forever. But if we consider with scientific point any view biological organism, then its structure, coherence and, in general, the very fact of existence are amazing, and this applies to even the most simple types. And there’s nothing to say about the human body! Any area of ​​its biology is unique and interesting in its own way.

In this article we will look at what receptors are, why they are needed and what they are. We will try to understand this in as much detail as possible.

Action

According to the encyclopedia, a receptor is a combination of the endings of nerve fibers in some neurons that differ in sensitivity, and specific formations and special cells living tissues. Together they are engaged in transforming the influence of factors of various kinds, which are often called stimuli, into a special one. Now we know what a receptor is.

Some types of human receptors perceive information and influence through special cells of epithelial origin. In addition, modified signals also take part in the processing of information about stimuli. nerve cells, but their difference is that they cannot generate nerve impulses themselves, but only act on the innervating endings. For example, this is how they work taste buds(they are located in the epithelium on the surface of the tongue). Their action is based on chemoreceptors, which are responsible for sensing and processing the effects of chemical or volatile substances.

Now we know what they are and how they work.

Purpose

Simply put, receptors are responsible for the functioning of almost all senses. And in addition to the most obvious ones, such as vision or hearing, they enable a person to sense other phenomena: pressure, temperature, humidity, etc. So we looked at the question of what receptors are. But let's look at them in more detail.

Stimuli that activate certain receptors can serve as very different effects and actions, for example, deformation mechanical properties(wounds and cuts), aggression chemical substances and even an electric or magnetic field! True, which receptors are responsible for the perception of the latter has not yet been precisely established. We only know that they definitely exist, but they are developed differently in everyone.

Kinds

They are divided into types according to their location in the body and the irritant, thanks to which we receive signals to the nerve endings. Let us consider in more detail the adequate stimulus:

• Chemoreceptors are responsible for taste and smell; their work is based on the effects of volatile and other chemicals.
• Osmoreceptors - are involved in determining changes in osmotic fluid, i.e., increase or decrease (this is something like the balance between extracellular and intracellular fluids).
• Mechanoreceptors - receive signals based on physical influence.
• Photoreceptors - thanks to them our eyes receive the visible spectrum of light.
• Thermoreceptors are responsible for sensing temperature.
• Pain receptors.

receptors?

To put it simply, these are substances that can bind to receptors, but do not change the course of their work. An agonist, on the contrary, not only binds, but also actively influences the receptor. For example, the latter include some narcotic substances, used for anesthesia. They desensitize the receptor. If they are called partial, then their action is incomplete.

nerve formations that serve to convert light, mechanical, chemical, thermal energy from external and internal environmental agents into nerve impulses. Peripheral specialized parts of analyzers, through which only a certain type of energy is transformed into the process of nervous excitation. Receptors vary widely in structural complexity and level of adaptation to their function. Individual receptors are anatomically connected to each other and form receptive fields that can overlap.

Depending on the energy of the corresponding stimulation, the receptors are divided into mechanoreceptors and chemoreceptors. Mechanoreceptors are found in the ear, vestibular apparatus, muscles, joints, skin and internal organs. Chemoreceptors serve the olfactory and taste sensitivity; many of them are in the brain, responding to changes chemical composition fluid environment of the body. Visual receptors are essentially also chemoreceptors. Sometimes thermoreceptors, photoreceptors and electroreceptors are also secreted.

Depending on the position in the body and the function performed, the following are distinguished:

1) exteroceptors - this includes distant receptors that receive information at a certain distance from the source of stimulation - olfactory, auditory, visual, gustatory;

2) interoceptors - signal about stimuli of the internal environment;

3) proprioceptors - signal the state of the motor system of the body.

Receptors

Word formation. Comes from Lat. receptor - receiving.

Kinds. Based on location and function, exteroceptors, interoceptors and proprioceptors are distinguished.

In accordance with the nature of the perceived impact, mechano-, thermo-, photo-, chemo- and electroreceptors are distinguished.

RECEPTOR

In most general terms, a specialized nerve cell or part thereof that converts physical stimuli into receptor potentials. That is, a cell that is sensitive to a particular form of stimulation and reliably undergoes a particular pattern of change. This definition is broad enough to cover everything that is discussed below and which should be classified as receptors, (a) Peripheral cells in various sensory systems that respond to certain forms of physical energy, for example, rods and cones in the retina, hair cells in the organ of Corti ear, pressure-sensitive cells in the skin, taste buds on the tongue, etc. (b) Proprioceptors that respond to external stimulation, for example, hair cells in the semicircular canals of the morning ear, stretch receptors in the internal organs, kinesthetic receptors in joints and tendons, etc. (c) Postsynaptic neurons, which respond to the release of neurotransmitter substances into the nerve system; see receptor site here. Behind last years Several receptor classification systems have been used. Some of them are based on the location of receptors in the body, for example, exteroceptors, interoceptors and proprioceptors. Some are based on the specific modality being served, such as visual receptors, auditory receptors, etc. Some depend on determining the form of physical stimuli to which the receptors are sensitive, for example, chemical receptors such as those for taste and smell, mechanical receptors for pressure and hearing, light receptors in vision, temperature receptors for heat and cold, etc. Other systems focus on neurotransmitter substances that connect nerve pathways serving a specific receptor system, for example, cholinergic receptors, paminergic receptors, etc. Please note that this last topic of classification is based on the analysis of a rather central nervous system than certain sensory systems that initiate neural changes. Usually the context in which certain receptors are discussed makes it clear which classification system is used.

Receptors

peripheral specialized part of afferent nerves that provide perception and transformation of a certain type of energy into a process nervous excitement. There are: visual, auditory, olfactory, etc. receptors.

Receptor

A specialized nerve structure with particularly high degree irritability, capable of perceiving irritation and transforming it into bioelectric potential - a nerve impulse. It has specificity to certain stimuli, which determines the structure of the receptor and its location (exteroceptor, proprioceptor, interoreceptor).

RECEPTORS

from lat. recipere - receive] - a specialized peripheral part of each analyzer: the terminal formations of afferent nerve fibers that perceive stimuli from the external (exteroceptors) or internal (interoceptors) environment of the body and convert the physical (mechanical, thermal, etc.) or chemical energy of the stimuli into excitation (nerve impulses) transmitted along sensory nerve fibers to the central nervous system (see Interoceptors, Proprioceptors, Exteroceptors)

RECEPTOR

from lat. receptor - receiving) is a peripheral specialized part of the analyzer, through which only a certain type of energy is transformed into the process of nervous excitation. Based on their location, R. are classified into exteroceptors, interoceptors, and proprioceptors. Exteroceptors include distant receptors that receive information at some distance from the source of stimulation (olfactory, auditory, visual, taste); interoreceptors signal about stimuli in the internal environment of the body, and proprioceptors signal about the state of the body. motor system body. Individual R. are anatomically connected to each other and form receptive fields that can overlap. Depending on the nature of the stimulus, mechano-, thermo-, photo-, chemo- and electroreceptors are distinguished. The largest group consists of R., which perceive mechanical irritations. These include skin mechanoreceptors that respond to touch and pressure; R. of the inner ear, perceiving sound stimuli; R. of the vestibular apparatus, responding to changes in the acceleration of movement of our body, and, finally, mechanoreceptors of blood vessels and internal organs. Thermoreceptors respond to changes in the temperature of the external and internal environment of the body; They are divided into thermal and cold. Light stimuli are perceived by photoreceptors located in the retina of the eye. Chemoreceptors include receptors of taste and smell, as well as interoreceptors of internal organs. All R. are distinguished by high sensitivity to adequate stimulation, characterized by the value of the absolute threshold of irritation or the minimum strength of the stimulus that can lead R. to a state of excitation. However, the sensitivity of different R. is not the same. Thus, rods are more sensitive than cones; phasic mechanoreceptors that respond to active deformation are more sensitive than static ones that respond to constant deformation, etc. Transformation in R. of the energy of the external world into a nervous process of spreading excitation that carries nerve centers information about the action of the stimulus is called reception. Reception processes are subject to the basic psychophysical law, and R.'s functions are under regulatory control from the c. n. With.

Article on human anatomy and physiology

Receptors and their role in the human body

Vorobiev Anton Sergeevich

• By position in the body
  • Exteroceptors (exteroceptors) - located on the surface or near the surface of the body and perceive external stimuli (signals from environment)
  • Interoreceptors (interoceptors) - located in internal organs and perceive internal stimuli (for example, information about the state of the internal environment of the body)
    • Proprioceptors (proprioceptors) are receptors of the musculoskeletal system, allowing one to determine, for example, the tension and degree of stretching of muscles and tendons. They are a type of interoreceptor
• Ability to perceive different stimuli
  • Monomodal - responding to only one type of stimulus (for example, photoreceptors to light)
  • Polymodal - responsive to multiple types of stimuli (for example, many pain receptors, as well as some invertebrate receptors that respond simultaneously to mechanical and chemical stimuli)
• By adequate stimulus :
  • Chemoreceptors - perceive the effects of dissolved or volatile chemicals
  • Osmoreceptors - perceive changesosmotic concentration fluids (usually the internal environment)
  • Mechanoreceptors- perceive mechanical stimuli (touch, pressure, stretching, vibrations of water or air, etc.)
  • Photoreceptors - perceive visible and ultraviolet light
  • Thermoreceptors - perceive decreasing (cold) or increasing (heat) stimuli
  • Pain receptors , stimulation of which leads to pain. There is no such physical stimulus as pain, so separating them into a separate group based on the nature of the stimulus is to some extent arbitrary. In fact, they are high-threshold sensors of various (chemical, thermal or mechanical) damaging factors. However, a unique feature of nociceptors, which does not allow them to be classified, for example, as “high-threshold thermoreceptors,” is that many of them are polymodal: the same nerve ending can be excited in response to several different damaging stimuli.
  • Electroreceptors - perceive changes in the electric field
  • Magnetic receptors - perceive changes in the magnetic field

• Pain receptors.
• Pacinian Taurus — encapsulated pressure receptors in a round multilayer capsule. They are located in the subcutaneous fat. They are quickly adapting (they react only at the moment the impact begins), that is, they register the force of pressure. They have large receptive fields, that is, they represent gross sensitivity.
• Meissner's corpuscles - pressure receptors located in dermis . They are a layered structure with a nerve ending running between the layers. They are quickly adaptable. They have small receptive fields, that is, they represent subtle sensitivity.
• Merkel discs are unencapsulated pressure receptors. They are slowly adapting (react throughout the entire duration of exposure), that is, they record the duration of pressure. They have small receptive fields.
• Hair follicle receptors - respond to hair deviation.
• Ruffini endings are stretch receptors. They are slow to adapt and have large receptive fields.

• Muscle spindles - muscle stretch receptors are of two types:
  • with nuclear bag
  • with nuclear chain
• Golgi tendon organ - muscle contraction receptors. When a muscle contracts, the tendon stretches and its fibers compress the receptor ending, activating it.

• David Hubel - “Eye, Brain, Vision” translation from English. Ph.D. biol. Sciences O. V. Levashova, Ph.D. biol. Sciences G. A. Sharaeva, ed. Corresponding member USSR Academy of Sciences A. L. Byzova, Moscow “Mir”, 1990
• http://anatomus.ru/articles/rol-retseptorov.html

Skin receptors are responsible for our ability to sense touch, heat, cold and pain. Receptors are modified nerve endings that can be either free, unspecialized or encapsulated complex structures that are responsible for a certain type of sensitivity. Receptors perform a signaling role, so they are necessary for a person to interact effectively and safely with the external environment.

Main types of skin receptors and their functions

All types of receptors can be divided into three groups. The first group of receptors is responsible for tactile sensitivity. These include Pacinian, Meissner, Merkel and Ruffini corpuscles. The second group is
thermoreceptors: Krause flasks and free nerve endings. The third group includes pain receptors.

The palms and fingers are more sensitive to vibration: due to the large number of Pacinian receptors in these areas.

All types of receptors have different zones of sensitivity, depending on the function they perform.

Skin receptors:
. skin receptors responsible for tactile sensitivity;
. skin receptors that respond to temperature changes;
. nociceptors: skin receptors responsible for pain sensitivity.

Skin receptors responsible for tactile sensitivity

There are several types of receptors responsible for tactile sensations:
. Pacinian corpuscles are receptors that quickly adapt to pressure changes and have wide receptive fields. These receptors are located in the subcutaneous fat and are responsible for gross sensitivity;
. Meissner's corpuscles are located in the dermis and have narrow reception fields, which determines their perception of fine sensitivity;
. Merkel bodies - adapt slowly and have narrow receptor fields, and therefore their main function is the sensation of surface structure;
. Ruffini's corpuscles are responsible for sensations of constant pressure and are located mainly in the area of ​​​​the soles of the feet.

Also separately identified are receptors located inside the hair follicle, which signal the deviation of the hair from its original position.

Skin receptors that respond to temperature changes

According to some theories, for the perception of heat and cold there are different types receptors. Krause flasks are responsible for the perception of cold, and free nerve endings are responsible for hot. Other theories of thermoreception claim that it is free nerve endings that are designed to sense temperature. In this case, thermal stimulation is analyzed by deep nerve fibers, and cold stimulation by superficial ones. Between themselves, temperature sensitivity receptors form a “mosaic” consisting of cold and heat spots.

Nociceptors: skin receptors responsible for pain sensitivity

At this stage, there is no final opinion regarding the presence or absence of pain receptors. Some theories are based on the fact that free nerve endings located in the skin are responsible for the perception of pain.

Prolonged and severe painful stimulation stimulates the emergence of a stream of outgoing impulses, and therefore adaptation to pain slows down.

Other theories deny the presence of separate nociceptors. It is assumed that tactile and temperature receptors have a certain threshold of irritation, above which pain occurs.

Receptors (Latin receptor - receiving, from recipio - accepting, receiving)

special sensitive formations that perceive and transform irritations from the external or internal environment of the body and transmit information about the active agent to the nervous system (see Analyzers). R. are characterized by diversity in structural and functional terms. They can be represented by free endings of nerve fibers, endings covered with a special capsule, as well as specialized cells in complexly organized formations, such as the Retina eyes, organ of Corti, etc., consisting of many R.

R. are divided into external, or exteroceptors, and internal, or interoreceptors. Exteroceptors are located on the outer surface of the animal or human body and perceive stimuli from the outside world (light, sound, thermal, etc.). Interoceptors are found in various tissues and internal organs (heart, lymphatic and blood vessels, lungs, etc.); perceive stimuli signaling the state of internal organs (visceroceptors), as well as the position of the body or its parts in space (vestibuloceptors). Type of interoceptors - Proprioceptors , located in muscles, tendons and ligaments and perceiving the static state of muscles and their dynamics. Depending on the nature of the perceived adequate stimulus, they distinguish between mechanoreceptors, photoreceptors, chemoreceptors, thermoreceptors, etc. R. sensitive to ultrasound have been found in dolphins, bats and moths, and in some fish - to electric fields. Less studied is the existence of R. in some birds and fish, sensitive to magnetic fields(see Magnetobiology). Monomodal R. perceive stimuli of only one kind (mechanical, light, or chemical); among them are R., different in the level of sensitivity and attitude to the irritating stimulus. Thus, vertebrate photoreceptors are divided into more sensitive rod cells, which function as twilight vision cells, and less sensitive cone cells, which provide daytime light perception and color vision in humans and a number of animals. ; skin mechanoreceptors - to more sensitive phase R., reacting only to the dynamic phase of deformation, and static ones, reacting to constant deformation, etc. As a result of this specialization of R., the most significant properties of the stimulus are highlighted and a subtle analysis of the perceived irritations is carried out. Polymodal R. react to stimuli of different qualities, for example, chemical and mechanical, mechanical and temperature. In this case, specific information encoded in molecules is transmitted to the central nervous system along the same nerve fibers in the form of nerve impulses, undergoing repeated energy amplification along the way. Historically, the division of R. has been preserved into distant (visual, auditory, olfactory), which perceives signals from a source of irritation located at some distance from the body, and contact - in direct contact with the source of irritation. R. also distinguish between primary (primary-sensing) and secondary (secondary-sensing). In primary R., the substrate that perceives external influences is located in the sensory neuron itself , which is directly (primarily) excited by the stimulus. In secondary R., between the active agent and the sensory neuron there are additional, specialized (receptive) cells in which the energy of external stimuli is converted (transformed) into nerve impulses.

All R. are characterized by the same general properties. They are specialized for the reception (See Reception) of certain irritations characteristic of them, called adequate. When stimulation occurs in R., a change in the difference in bioelectric potentials occurs (See Bioelectric potentials) by cell membrane, the so-called receptor potential, which either directly generates rhythmic impulses in the receptor cell or leads to their occurrence in another neuron connected to R. through a synapse (See Synapses) . The frequency of impulses increases with increasing intensity of stimulation. With prolonged exposure to the stimulus, the frequency of impulses in the fiber extending from the R. decreases; A similar phenomenon of decreased R. activity is called physiological adaptation (See Physiological Adaptation). For different R. the time of such adaptation is not the same. R. are distinguished by high sensitivity to adequate stimuli, which is measured by the value of the absolute threshold, or the minimum intensity of stimulation that can lead R. to a state of excitement. So, for example, 5-7 quanta of light falling on the R. eye cause a sensation of light, and 1 quanta is enough to excite an individual photoreceptor. R. can also be excited by an inadequate stimulus. Affecting, for example, the eye or ear electric shock, can cause the sensation of light or sound. The sensations are associated with the specific sensitivity of R., which arose during the evolution of organic nature. The figurative perception of the world is associated primarily with information coming from exteroceptors. Information from interoceptors does not lead to clear sensations (see Muscle feeling). The functions of various R. are interconnected. The interaction of vestibular R., as well as R. of the skin and proprioceptors with the visual ones is carried out by the central nervous system and underlies the perception of the size and shape of objects and their position in space. R. can interact with each other without the participation of the central nervous system, that is, due to direct communication with each other. Such interaction, established in visual, tactile, and other signals, is important for the mechanism of spatiotemporal contrast. R.'s activity is regulated by the central nervous system, which adjusts them depending on the needs of the body. These influences, the mechanism of which has not been sufficiently studied, are carried out through special efferent fibers that approach certain receptor structures.

Lit.: Granit R., Electrophysiological study of reception, trans. from English, M., 1957; Prosser L., Brown F., Comparative physiology of animals, trans. from English, M., 1967; Vinnikov Ya. A., Cytological and molecular basis reception. Evolution of sense organs, L., 1971; Human Physiology, ed. E. B. Babsky, M., 1972, p. 436-98; Physiology of sensory systems, part 1-2, L., 1971-72 (Manual of Physiology); Handbook of sensory physiology, v. 1, pt 1. v. 4, pt 1-2, V. - HdIb. - N.Y., 1971-72; Melzack R., The puzzle of pain, Harmondswarth, 1973. see also lit. at Art. Interoreception.

A. I. Esakov.

Pharmacological receptors(RF), cellular receptors, tissue receptors, located on the membrane of the effector cell; perceive regulatory and trigger signals of the nervous and endocrine systems, the action of many pharmacological drugs that selectively affect this cell, and transform these effects into its specific biochemical or physiological reaction. The most studied are the RFs through which the action of the nervous system is carried out. The influence of the parasympathetic and motor parts of the nervous system (the mediator acetylcholine) is transmitted by two types of RF: N-cholinergic receptors transmit nerve impulses to skeletal muscles and in the nerve ganglia from neuron to neuron; M-cholinergic receptors are involved in the regulation of heart function and smooth muscle tone. The influence of the sympathetic nervous system (transmitter norepinephrine) and the hormone of the adrenal medulla (adrenaline) is transmitted by alpha and beta adrenoceptors. Stimulation of alpha adrenoceptors causes vasoconstriction, elevation blood pressure, pupil dilation, contraction of a number of smooth muscles, etc.; stimulation of beta-adrenoceptors - increased blood sugar, activation of enzymes, vasodilation, relaxation of smooth muscles, increased frequency and strength of heart contractions, etc. Thus, the functional effect is carried out through both types of adrenoceptors, and the metabolic effect is carried out mainly through beta-adrenoceptors. RFs have also been discovered that are sensitive to dopamine, serotonin, histamine, polypeptides and other endogenous biologically active substances and to pharmacological antagonists of some of these substances. The therapeutic effect of a number of pharmacological drugs is due to their specific action to specific R.

Lit.: Turpaev T. M., Mediator function of acetylcholine and the nature of the cholinergic receptor, M., 1962; Manukhin B.N., Physiology of adrenergic receptors, M., 1968; Mikhelson M. Ya., Zeimal E. V., Acetylcholine, L., 1970.

B. N. Manukhin.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

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Modern encyclopedia

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