Where are the receptors that perceive odors located briefly. Tapestry “Lady with a Unicorn” – an allegorical depiction of the sense of smell
Among all the senses, the most important and significant role Sight and hearing play a role in human life. That's why for a long time it is these channels that connect us with the surrounding world, have been studied most actively. But the olfactory analyzer attracted the attention of physiologists to a much lesser extent. Indeed, the sense of smell in humans, and in primates in general, is relatively poorly developed. And yet, its role in our lives should not be underestimated.
Even a newborn baby reacts to odorous substances, and at the 7th–8th month of life, conditioned reflexes to “pleasant” and “unpleasant” odors are formed.
A person can perceive more than 10,000 odors. Some of them can stimulate or discourage appetite, change mood and desires, increase or decrease performance, and even force you to buy something that is not very good. the right thing. In many stores in Europe and America, fragrances are used with all their might to attract customers. According to an American marketing service, simply aromatizing the air in a store can increase sales by 15%. There are even five scents that, when present in the store, can “provoke” a visitor to buy underwear and outerwear. These are vanilla, lemon, mint, basil and lavender. Grocery supermarkets should be filled with fresh smells: warm bread, cucumbers and watermelons. There are also holiday smells. For example, before the New Year, stores should smell like tangerines, cinnamon and spruce or pine needles. For most people, these smells are strongly associated with memories of the holiday and give them pleasure. However, in some people (especially children), sprayed aromatic substances can cause allergies. So, maybe it’s good that “advertising” fragrances are not sprayed in our stores yet.
Smells can easily “stir up” our memory and bring back long-forgotten sensations, for example from childhood. The fact is that the centers of the olfactory analyzer are located in humans in the ancient and old cerebral cortex. Next to the olfactory center is the center responsible for our emotions and memory. Therefore, smells are emotionally charged for us, awakening not logical, but emotional memory.
The perception of smell by our olfactory system begins with the nose, or more precisely, with the olfactory epithelium, located in the human upper sections the middle turbinate, the superior turbinate and the upper part of the nasal septum. Peripheral processes receptor cells The olfactory epithelium ends in an olfactory club, decorated with a bunch of microvilli. It is the membrane of these villi (cilia and microvilli) that is the site of interaction between the olfactory cell and the molecules of odorous substances. In humans, the number of olfactory cells reaches 6 million (3 million in each nostril). This is a lot, but in those mammals in whose life the sense of smell plays a significant role, these cells are immeasurably more numerous. For example, a rabbit has about 100 million of them!
In the human embryo, the development of olfactory cells occurs quite quickly. Already in an 11-week fetus they are well differentiated and presumably capable of performing their function.
The receptor cells of the olfactory epithelium are constantly renewed. The life of one cell lasts only a few months or even less. When the olfactory epithelium is damaged, cell regeneration is significantly accelerated.
But how does the excitation of olfactory cells occur? In the last decade, it has become clear that the main role in this process belongs to receptor proteins, whose molecules, interacting with molecules of odorant substances, change their conformation. This leads to the launch of a whole chain of complex reactions, as a result of which the sensory signal is converted into a universal signal nerve cells. Next, from the receptor cells along their axons, which form the olfactory nerve, the signal is transmitted to the olfactory bulbs. This is where it happens primary processing, and then the signal along the olfactory nerve enters brain, where its final analysis takes place.
The ability to perceive odors changes as a person ages. Olfactory acuity reaches its maximum at age 20, stays at the same level for about 30–40 years, and then begins to decline. Especially noticeable decrease olfactory acuity manifests itself in people over 70 years of age, and sometimes even 60 years of age. This phenomenon is called senile hyposmia, or presbiosmia, and is not nearly as harmless as it might seem. Older people gradually cease to perceive the smell of food and therefore lose their appetite. After all, the aroma of food is one of the necessary conditions for the production of digestive juices in the gastrointestinal tract. No wonder they say: “... such a wonderful smell that even my mouth started watering...”. In addition, taste and olfactory perceptions are very close. The odorous substances contained in food products enter the nasal cavity through the nasopharynx, and we smell their aroma. But when we have a runny nose, no matter what we eat, it feels like we are chewing tasteless cardboard. Elderly people with a sharply reduced sense of smell perceive food in the same way. They also lose the ability to determine quality by smell. food products, and therefore can become poisoned by eating low-quality food. It also turns out that older people no longer perceive the smell of mercaptans as unpleasant. Mercaptans are substances added to household products. natural gas(which in itself does not smell of anything from a human point of view) specifically so that one can notice its leakage by smell. Old people stop noticing this smell...
But even among young people, sensitivity to the smell of the same substances varies greatly. It also varies depending on factors external environment(temperature, humidity), emotional state and hormonal levels. In pregnant women, for example, against the background of a general decrease in the acuity of smell, sensitivity to certain odors sharply increases. In general, the range of threshold concentrations of various odorous substances perceived by humans is very large - from 10-14 to 10-5 mol per 1 liter of air.
Until now, we have talked mainly about external odors that come from the world around us. But among the odorous substances, there are also those that are released by our body itself and are capable of causing certain behavioral and physiological reactions in other people. Substances with such properties are called pheromones. In the animal world, pheromones play a huge role in the regulation of behavior - we have already written about this in our newspaper (No. 10/1996 and No. 16/1998). Substances have also been discovered in humans that have a certain pheromonal effect during our communication. Such substances are found, for example, in human sweat. In the 70s XX century researcher Martha McClintock discovered that women who live in the same room (for example, in a dormitory) for a long time synchronize their menstrual cycles. And the smell of men's secretion sweat glands causes normalization of unstable menstrual cycles in women.
Tapestry “Lady with a Unicorn” – an allegorical depiction of the sense of smell
The smell of the secretion secreted by our axillary sweat glands depends both on the substances secreted by the body itself and on the bacteria present in the sweat glands. After all, it is known that fresh axillary sweat itself (produced profusely, for example, in hot weather) does not have a strong specific odor. But the activity of bacteria contributes to the release of odorous molecules, initially associated with special carrier proteins from the group of lipocaines.
Chemical composition Male and female sweat varies greatly. In women it is associated with phases menstrual cycle, and a man who has been in prison for a long time intimate relationships with a woman, is able to determine by smell the time of his partner’s ovulation. True, as a rule, this happens unconsciously - it’s just that during this period the girlfriend’s smell becomes the most attractive to him.
In the secretions of the sweat glands of both men and women, in addition to other components, there are two odorous steroids - androstenone (ketone) and androstenol (alcohol). For the first time, these substances were identified as components of the sex pheromone contained in boar saliva. Androstenone has a strong, specific odor, which for many people is similar to the smell of urine. The smell of androstenol is perceived as musky or sandalwood. The content of androstenone and androstenol in men's axillary sweat is much higher than in women's. Research has shown that the odor of androstenone can affect the physiological and emotional condition people, in particular, suppress the above-described effect of synchronization of sexual cycles in women living in the same room. In some situations, the faint smell of androstenone creates a comfortable state of “security” in women, while in men, on the contrary, it causes discomfort and is associated with competition and aggression.
Representatives different cultures can perceive the same odors differently. Such differences were revealed in a completely unique survey conducted in 1986 by the magazine National Geographic. The next issue of this magazine included samples of six odorous substances: androstenone, isoamyl acetate (smells like pear essence), galaxolide (smells like synthetic musk), eugenol, a mixture of mercaptans and rose oil. The substances were enclosed in microcapsules applied to paper. When the paper was rubbed with a finger, the capsules were easily destroyed and the smell was released. Readers were asked to smell the proposed substances and then answer the questionnaire. It was necessary to evaluate the intensity of the proposed odors, define them as pleasant, unpleasant or neutral, and talk about the emotions and memories they evoked. Respondents were also asked to indicate their age, gender, occupation, country of residence, race, presence of diseases, etc. For women, it was necessary to indicate the presence of pregnancy. Letters with completed questionnaires came from more than 1.5 million people living on different continents!
Baker of the House of Amun donating incense to Osiris
Many of the respondents did not smell androstenone at all, and the number of people who were not sensitive to this smell varied greatly in different regions globe. So, if in the USA about 30% of women did not feel this smell, then among white women living in Africa there were half as many - about 15%.
We have already talked about the loss of olfactory acuity in older people, which was also clearly revealed during this study. The survey also confirmed that smoking people smells much worse than non-smokers.
People who, for various reasons, had completely lost their sense of smell also sent their answers to National Geographic. It turns out that there are a lot of such people, including among young people. According to the US National Institutes of Health, in 1969, smell disorders were noted in 2 million people, and by 1981 this figure had increased to 16 million! This situation is largely due to the deterioration environmental situation. Among the patients at the Smell and Taste Clinic in Washington, 33% of patients with dysosmia (impaired sense of smell) are people aged 17–20 years. According to researcher Hendricks, in 1988, 1% of the Dutch population had problems with their sense of smell. As for our country, very often people, overwhelmed by other problems, simply do not pay attention to such a “trifle” as a violation or lack of sense of smell. And if they do, they don’t know whether it’s possible in this case health care and where to go for it. Treatment of people with impaired sense of smell is carried out in Moscow, at the Moscow ENT Clinic medical academy them. THEM. Sechenov.
What can cause a violation of the sense of smell? Most often, the corresponding disorders are associated with damage to the receptor apparatus of the olfactory analyzer (about 90% of cases), with damage to the olfactory nerve - about 5% of cases, and with damage to the central parts of the brain - the remaining 5% of cases.
The causes of olfactory disorder at the “receptor level” are very diverse and numerous. These include injuries to the olfactory zone and cribriform plate, and inflammatory processes in the nasal cavity, and traumatic brain injuries, and drug intoxication, and allergic reactions, and mutations, and vitamin deficiencies (for vitamins A and B12), and salt intoxication heavy metals(cadmium, mercury, lead), and inhalation of vapors of irritating substances (formaldehyde), and viral infections (mainly the influenza virus), and ionizing radiation, and much more.
The causes of damage to the olfactory nerve are most often due to infectious diseases, disorders metabolism, toxic effects medications, nerve damage due to surgical operations and tumors.
Damages to the centers of the olfactory analyzer can be caused by traumatic brain injury, a violation cerebral circulation, brain tumors, genetic and infectious diseases, demyelinating processes, Parkinson's disease, Alzheimer's disease. In the latter two diseases, a decrease in the acuity of smell is often detected in the early stages, which allows treatment to begin earlier.
What is a violation of the sense of smell? It could be complete absence the ability to perceive odors (anosmia) or a decrease in the acuity of smell (hyposmia) of varying degrees of severity. A violation of the sense of smell can also be expressed in the form of a distortion in the perception of odors (aliosmia), in which all odors are perceived “in the same manner.” For example, with cacosmia, all odors seem putrid and fecal; with torsosmia - chemical, bitter, burning or metal odors; with parosmia, “garlic smells like violets.” Mixed cases and phantosmia – olfactory hallucinations – are also possible.
Many of the described smell disorders can be successfully treated, especially if you do not delay visiting a doctor.
Olfaction is the process of perceiving the odors of substances. Elements that perceive odors of substances are located in the mucous membrane of the superior and partly middle nasal concha. These elements are represented by olfactory cells and receptors.
The structure of the human olfactory organs
Receptor cells have short (15-20 µm) peripheral processes and long central ones. The bodies of these cells are located in the thickness of the mucosa, the surface of which is 240-500 mm 2. Olfactory receptors constitute the chemical sense organ. In humans there are about 40 million, and in dogs, for example, many times more (about 225 million). This explains high abilities dogs detect odors.
The peripheral processes of the olfactory cells end in club-shaped thickenings. These thickenings at their apex contain 10-12 pointed hairs, consisting of 9 pairs of filaments. Olfactory hairs are a kind of antennas that actively interact with molecules of odorous substances.
It is believed that molecules of odorous substances settle on the surface of the nasal mucosa and dissolve in the secretion of glands, which are also located in the nasal mucosa. Substances dissolved in this way irritate the olfactory hairs and club-shaped thickenings. From here, impulses travel along the olfactory nerves to the olfactory centers of the brain located in diencephalon and bark. There the sensation of the smell of inhaled substances is formed.
Olfactory receptor system olfactory nerves and olfactory centers is made up of an olfactory analyzer. This analyzer is less important for human life than vision and hearing. The loss of the sense of smell manifests itself in the inability to smell substances in the air (and they may be important for health), or to recognize spoiled food. For workers in the perfumery, food and nutrition industries, loss of smell can cause a change in profession.
The role of smell in the life of modern man cannot be underestimated. Surprisingly, the sense of smell allows us to smell more than 10,000 different smells. Most odorous substances can increase a person's appetite or stimulate good mood, and also promote the activation of brain activity.
The nose is so sensitive that some marketers use it in business. For example, how many times have you made a successful or not so successful purchase under the influence of a charming aroma in a store?
The sense of smell allows a person to avoid the dangers that exist around him, and also stimulates pleasure from objects and people nearby. But for some reason we underestimate the role of smell in our lives. In most cases, the human nose is an organ whose existence is remembered only when it is affected by various infectious or inflammatory processes.
The sense of smell is extremely highly developed in humans from birth. For example, a newborn may not see or hear his mother, but by smell he is able to recognize her from hundreds and even thousands of other women. Unfortunately, main body sense of smell - the nose, begins to lose its sensitivity already in the second year of a little person’s life.
As each year of life progresses, the sense of smell decreases, and the sensory receptors atrophy one by one. This is an irreversible process that no one can help influence. Thus, upon reaching old age, a person may notice that he no longer hears the smells around him so clearly. And this is absolutely normal occurrence, which can only be corrected by strong drug therapy.
A person’s sense of smell can decrease not only as a result of age-related changes. The nose may become less sensitive as a result of:
- Inflammatory processes occurring in the nasopharynx;
- Formation of nasal polyps;
- Allergic reaction;
- Side effects after taking drugs that eliminate cardiovascular failure;
- Poor hygiene oral cavity;
- Impact toxic substances on the body;
- Consequences of acute viral hepatitis;
- Deficiency of vitamins and minerals;
- Bad habits.
The organ of smell loses its functionality as a result of cirrhosis of the liver, damage to the body by multiple sclerosis, and the formation of benign or malignant tumors.
The sensitivity of odor receptors decreases in people diagnosed with Alzheimer's disease, pathological condition Parkinson's, epilepsy, and those who have suffered traumatic brain injury or suffer from dysfunction thyroid gland. Only a specialist can determine and understand which of the above reasons affected the organ of smell.
Ability to hear smells and personal relationships
The human sense of smell is a means of perceiving and receiving information that works 24 hours a day. Few people know that the sense of smell is very closely related to the sense of taste of food. For most famous chefs, the loss of smell can be equated to death.
Surprisingly, a person uses his nose not only to breathe, but also as a kind of x-ray of the people around him. Many people think that love for friends and life partner begins in the heart, but this is not so.
The first instinct that is triggered in a person is to scan the smell of an approaching person. And, if we like the odorous substances that the human body secretes, then this is already the first step towards rapprochement. This is very easy to check for yourself. Is there someone around you whose smell you don’t like?
How ideas about smell are formed
Smell and smell are two components that work so that a person can live a full and vibrant life. The olfactory system consists of the following components:
- Olfactory stimuli;
- Olfactory threads;
- Mucous membrane;
- Bulb;
- Olfactory tract;
- Cortex.
The sense of smell enters the brain through the olfactory analyzer, that is, the nose. It contains the receptor for the olfactory epithelium and the olfactory nerve.
The ability to perceive and analyze surrounding odors is carried out through receptor cells, of which there are about 10 million in humans. How can a person distinguish the odorous substances that surround him? The aroma enters the nose, affecting sensitive receptors, which, in turn, transmit a corresponding signal to the cerebral cortex.
Perception of smells around us
The role of the sense of smell is manifested not only in the perception of surrounding odors, but also affects color perception, excitability vestibular apparatus, hearing and taste. If the nose does not function as a result of inflammatory processes, then a person’s thinking slows down sharply. The sense of smell also takes an active part in the formation of behavioral reactions, emotionality and memory. All substances that enter the body through the nose find a response in the form of its reaction.
So, ammonia, possessing caustic and pungent odor, provokes irritation trigeminal nerve, activates brain activity and brings the person to consciousness. Thanks to the action of odorous substances, it is possible to successfully control a person’s emotions and feelings, which is what successful companies use in their practice. Next time you buy fast food, think about it: are you really hungry or just can't resist the smell of it?
Despite the fact that a person’s sense of smell contributes to the perception of the surrounding world and assessment of the surrounding environment, the threshold of sensitivity differs for each person. So, someone’s nose may react to the smell of vanillin, which comes from a neighboring street, but someone else will not hear it even at a distance of a couple of centimeters.
It is interesting to know that the threshold for the perception of odors can increase or decrease depending on the time of day and season. As a rule, the nose becomes more sensitive after prolonged sleep, as well as during periods of increased hunger.
Even if a person has a good sense of smell, he is still not able to sense and fully experience his own smell. Physiology is designed in such a way that we are able to perceive the odors of the people around us, but the odorous substances in our body are blocked when they hit the sensitive receptors of the epithelium.
Therefore, it is so important to pay attention to your own hygiene and monitor the amount of sweating. Surprisingly, we can get used to our own bad smell, as a result of which our sense of smell sharply decreases. TO basic rules and tips on maintaining good hygiene include daily showers, preference for clothing made from natural materials, and the use of deodorants.
If a person smells bad, then gradually this smell begins to spread to the room in which he lives. So creating a pleasant aroma in your own home is a prevention against a decrease in the sense of smell.
Development of the sense of smell
Experts advise constantly developing your sensitive receptors. To do this, you need to try to surround yourself with pleasant smells. Smell training can be done by visiting perfume shops, bakeries and specialty departments that sell herbs and spices. The house where you live can be decorated with various pillows of dried herbs that emit a pleasant aroma.
If you have reduced olfactory function, then increase your perception taste qualities dishes can be added to them by adding aromatic herbs and seasonings. It is known that sensitivity to odors is directly proportional to appetite.
If a person does not feel the aroma of food, then his appetite does not awaken. To stimulate the taste and olfactory receptors, you can place a saucer with coffee beans in the kitchen. This aromatherapy will help improve mood, eliminate depression and stimulate nasal receptors.
It is the peripheral part of the olfactory analyzer. There are the main organ of smell, represented by the olfactory region of the nasal mucosa, and the vomeronasal (Jacobson) organ. The latter has the appearance of paired epithelial tubes, closed at one end and opening into the nasal cavity at the other, located in the thickness of the nasal septum, on the border between the septal cartilage and the vomer. The vomeronasal organ perceives pheramones associated with the functions of the genital organs and the emotional sphere.
The olfactory organ is formed by the olfactory epithelium. It consists of three types of cells: olfactory, supporting and basal, lying on the basement membrane. Olfactory cells are chemosensory neurons. At the apical end they have a club-shaped thickening (clubs) with antennae - cilia, which are constantly moving. They contain chemoreceptors. They interact with odorous substances. In this case, the permeability of the cell membrane for ions changes and a nerve impulse arises, which is transmitted along the axons of neurons as part of the olfactory nerve to the olfactory bulbs of the brain. A person has up to 6 million olfactory cells, and a dog, which has a well-developed sense of smell, has 50 times more of these cells. Supporting cells are arranged in several rows; they support the olfactory cells in a certain position and create conditions for their normal activity. Basal cells, when multiplying, serve as a source of formation of new supporting and receptor cells.
Under the olfactory epithelium, in loose connective tissue, lie the alveolar-tubular olfactory glands, which secrete a mucous secretion that washes the surface of the olfactory epithelium. Odorous substances dissolve in it for better interaction with chemoreceptors. In the terminal sections of these glands, outside the secretory cells, lie myoepithelial cells. When they contract, the secretion of the glands is released onto the surface of the mucous membrane.
The olfactory analyzer consists of three parts: peripheral (olfactory organ), intermediate and central (olfactory cortex). In the peripheral part there are olfactory, chemosensory cells (the first neurons). Their basal processes form olfactory nerves, ending in synapses in the form of glomeruli on the dendrites of mitral cells (second neurons) located in the olfactory bulbs of the brain. Their axons go to the olfactory cortex of the brain, where third neurons are located, which belong to the central part of the olfactory analyzer.
Organ of vision
The organ of vision, the eye, is the most important of the senses, providing about 90% of information about the world around us. The eye is the peripheral part of the visual analyzer. It consists of the eyeball and auxiliary apparatus (oculomotor muscles, eyelids and lacrimal apparatus).
There are three functional apparatuses in the eye:
Receptor (retina);
Dioptric or light refractive - formed by a system of transparent structures and media that refract light entering the eye (cornea, lens, vitreous, fluid of the chambers of the eye)
Accommodative - provides a change in the shape and refractive power of the lens, which ensures a clear image of an object on the retina, regardless of the distance to the object. It is formed by the ciliary body, the ligament of cinnamon and the lens.
The eyeball is formed by three membranes: the outer - fibrous, the middle - vascular and the inner - reticular. Moreover, inside eyeball contains the lens, vitreous body, fluid of the anterior and posterior chambers of the eye.
The structure of the eyeball. Outer (fibrous) membrane of the eye. Consists of the sclera and cornea. The sclera covers the posterolateral surface of the eye and consists of dense, formed connective tissue 0.3-0.6 mm thick. The bundles of its collagen fibers, thinning, continue into the cornea's own substance. In the corner between the sclera and the iris there is a trabecular apparatus, in which there are numerous slit-like openings lined with endothelium - fountain spaces through which aqueous humor flows from the anterior chamber of the eye into the venous sinus (Schlemm's canal), and from there into the venous plexus of the sclera.
Cornea- the transparent part of the outer shell is about 1 mm thick. It is located in the front of the eyeball, separated from the sclera by a thickening - the limbus. The cornea consists of 5 layers.
1. Anterior epithelium - stratified squamous non-keratinizing epithelium. It contains many free nerve endings, providing high tactile sensitivity of the cornea.
2. Anterior limiting membrane. This is the thick basement membrane of the anterior epithelium.
3. Own substance. The structure resembles dense, formed connective tissue. It consists of parallel collagen fibers forming connective tissue plates, fibrocytes lying between them and a transparent ground substance.
4. Posterior limiting membrane. Formed by collagen fibers immersed in the ground substance. It is the basement membrane for the posterior epithelium.
5. Posterior epithelium. This is a single-layer squamous epithelium.
There are no blood vessels in the cornea. Nutrition occurs due to the diffusion of substances from the anterior chamber of the eye and the blood vessels of the limbus. If blood vessels grow into the cornea, it loses transparency, becomes cloudy, and becomes white because the anterior epithelium becomes keratinized.
Choroid- middle layer of the eye. It provides nutrition to the retina, regulates intraocular pressure, and absorbs excess light entering the eye. The choroid consists of three parts:
1) the choroid itself; 2) ciliary body; 3) iris. Consists of 4 layers:
1. The supravascular layer is the outermost layer, lies on the border with the sclera. It is formed by loose fibrous connective tissue rich in pigment cells.
2. Vascular layer. Consists of plexuses of arteries and veins lying in loose connective tissue.
3 Choriocapillaris layer. It contains a plexus of blood capillaries coming from the arteries of the vascular layer.
4. Basal plate. Through it nutrients and oxygen from blood capillaries reach the retina.
If the retina detaches from the choroid as a result of injury, its nutrition is disrupted and blindness occurs. The derivatives of the choroid are the ciliary body and the iris.
Ciliated (ciliary) body. Its basis is the ciliary muscle. Ciliary processes extend from the surface of the ciliary body, to which the filaments of the ligament of cinnamon are attached. The lens is suspended on the latter. When the radial ciliary muscle relaxes, the threads tighten and stretch the lens. It flattens, resulting in reduced refractive power, providing a clear image of distant objects on the retina. When the annular ciliary muscle contracts, the threads weaken, and the lens, due to its elasticity, becomes more convex, refracting light more strongly, ensuring that objects at close range are focused on the retina. This ability of the eye to obtain a clear image of objects at different distances is called accommodation. Accordingly, the ciliary body, ligament of Zinn and lens form the accommodative apparatus of the eye.
Outside, the ciliary body and its processes are covered with pigment epithelium, under which lies a single-layer prismatic secretory epithelium, forming aqueous humor that fills both chambers of the eye.
Iris (iris). It is a derivative of the choroid, extends from the ciliary body and lies in front of the lens. In the center there is a hole called the pupil. The iris consists of 5 layers:
1. The anterior epithelium is a single-layer squamous epithelium, which is a continuation of the posterior epithelium of the cornea.
2. Outer boundary layer. It consists of loose fibrous connective tissue rich in pigment cells - melanocytes and smooth muscle cells.
3.Vascular layer. Consists of loose fibrous connective tissue with a large number of blood vessels and melanocytes.
4. Internal boundary layer. Consists of loose connective tissue rich in melanocytes and smooth muscle cells.
5. Internal epithelium, or pigment layer. This is a layer of pigment epithelium, which is a continuation of the pigment layer of the retina.
In the outer and inner boundary layers of the iris there are two muscles: the constrictor and the dilator of the pupil. The first is located circularly around the pupil. The second is radial, from the pupil to the periphery. By changing the size of the pupil, the amount of light entering the eye is controlled. Therefore, the iris acts as the diaphragm of the eye (like the diaphragm in a camera).
Lens. It has the appearance of a biconvex lens. On the outside, the lens is covered with a transparent capsule - a thickened basement membrane. In front, underneath it lies a single-layer cuboidal epithelium. Toward the equator, epithelial cells become taller and form the growth zone of the lens. These cells multiply and differentiate into both the epithelium of the anterior surface of the lens and the lens fibers.
Lens fibers- these are specialized cells that are transparent hexagonal prisms containing the transparent substance crystallin. They fill the entire lens and are glued together by a transparent intercellular substance. The lens has no nerves or blood vessels.
The lens is suspended in the posterior chamber of the eye by threads of the ligament of zinc. When the tension of the threads changes, the curvature of the lens and its refractive power change. This ensures accommodation and the ability to clearly see objects at different distances.
Currently, clouding of the lens (cataract) is becoming more common. In this case, vision sharply decreases and it is necessary to remove the altered lens and replace it with an artificial one.
Vitreous body. It is a transparent, jelly-like, cell-free mass. Consists of water, hyaluronic acid, vitrein protein. Its frame forms a network of thin transparent fibers. Retina (retina) This is the inner lining of the eyeball. It consists of a posterior - visual and anterior - blind part. The border between them is uneven and is called a jagged edge. The caecum consists of two layers of cuboidal glial epithelium. The visual part of the retina forms the receptor apparatus of the eye. It consists of 10 layers:
1. Ppigment layer. Consists of a single layer of prismatic cells containing melanosomes with the pigment melanin. The bases of the cells lie on the basement membrane located on the border with the choroid, and their apical parts form processes that surround the rods and cones and protect them from excessive illumination. They also absorb excess, scattered light and thereby increase the resolving power of the eye. In addition, they ensure the normal functioning of photoreceptor neurons, providing them with retinal, and also phagocytose aging, spent fragments of photoreceptor neurons;
2. Layer of rods and cones (photosensory layer). It is formed by the apical parts (dendrites) of photoreceptor cells, which are shaped like rods or cones. They consist of outer, inner and connecting segments. The outer segment of the rod contains a stack of disks (up to 1000) formed by deep folds of the plasmalemma. They contain the photoreceptor protein rhodopsin: Rods - receptors for black and white, night vision. There are about 130 million of them in the retina. Cones are distinguished by the fact that their outer segments contain half-discs, which contain the photoreceptor protein iodopsin, and internal segment there is an ellipsoid - a lipid droplet surrounded by mitochondria. Cones are responsible for color vision. There are 6-7 million of them in the retina. The ability of cones to perceive colors is due to the existence three types cones sensitive to long-wave (red), medium-wave (yellow) and short-wave (blue) parts of the spectrum, containing, respectively, three types of visual pigment. Color blindness (color blindness) is caused by the congenital absence of these proteins. Under the influence of light, the visual pigment in rods and cones disintegrates, Na channels close, hyperpolarization of the membrane occurs, which is transmitted along the axons of photoreceptor neurons to the membranes of photoreceptor cells, and then excitation is transmitted to the chain of neurons visual analyzer into the cerebral cortex. As a result of the analysis and synthesis of millions of impulses coming from photoreceptor cells, a visual image appears in the cerebral cortex.
3. Outer boundary layer. Formed by processes of Müller glial cells. Located between the 2nd and 3rd layers of the retina.
4. Outer nuclear layer. It is formed by the bodies and nuclei of photoreceptor neurons
5. Outer mesh layer. Formed by both the somata of photoreceptor neurons, the dendrites of bipolar neurons and the synapses between them.
6. Inner nuclear layer. Represented by the bodies of bipolar, horizontal and amacrine neurons.
7. Inner mesh layer. Formed by axons of bipolar neurons, dendrites of ganglion neurons and synapses between them.
8. Ganglion layer. Formed by the bodies of ganglion neurons. Their number is much smaller than that of bipolar neurons and, especially, photoreceptor neurons.
9. Nerve fiber layer. Formed by the axons of ganglion neurons, which together form optic nerve.
10. Inner boundary layer. Lines the retina from the inside. It is formed by processes of glial fiber cells.
Thus, in the retina there are chains of three neurons: 1 - photoreceptor, 2 - bipolar and 3 - ganglinar. In this case, the nuclear and ganglion layers are formed by the bodies of neurons, and the reticular layer is formed by their processes and synapses. The human retina is inverted, i.e. the photoreceptor cells are its deepest layer, the furthest from light.
Blind spot- the place where the axons of ganglion cells converge from the entire retina, together forming the optic nerve. All other layers of the retina are missing, including the rods and cones. Therefore, this part of the retina does not perceive light.
Yellow spot- this is the place of best vision. It is located in the retina on the light axis of the eye. Here, all layers of the retina are spread apart, except for the cones, to which light access is facilitated.
Adaptive changing retinas in light and darkness. When exposed to bright light, melanin moves from the retinal pigment cells from the bodies to the processes that surround the outer segments of the rods and cones. This protects the photoreceptor cells from excess light. During dark adaptation, melanin moves back from the processes of the body of pigment cells, and photoreceptors become more accessible to light.
Retinal regeneration. The retina is constantly being renewed. Every day, up to 160 membrane disks are renewed in each rod and cone. The lifespan of a stick is 9-12 days. After this, it is phagocytosed by pigment cells and a new photoreceptor cell is formed in its place.
Eye- peripheral part of the visual analyzer. The intermediate part is formed by the axons of ganglion neurons and neurons lying in the visual thalamus. The central part is represented by neurons of the visual zone of the cerebral cortex.
Accessory apparatus of the eye - consists of the striated muscles, eyelids and lacrimal apparatus of the eye, described in detail in the course of human anatomy.
Smell
The ability to sense odorous substances, perceiving them as odors. Chemical substances, distributed in the form of steam, gas, dust and other things, enter the nasal cavity, where they interact with the corresponding receptors. In addition to chemoreceptors, other receptors of the oral mucosa may also participate in the formation of olfactory sensations: tactile, pain, temperature. Thus, some odorous substances cause only olfactory sensations (vanillin, valerian, etc.), while others have a complex effect (menthol causes a feeling of cold, chloroform – sweetness).
Simultaneous exposure to several odorous substances can lead to mixing of odors, their mutual neutralization, the displacement of one odor by another, and the appearance of a new odor. Consecutive changes in odors, leading to an increase in sensitivity to one of the odors after the action of another, are used in perfumery.
To classify odors, a scheme is used that includes four main odors: fragrant, sour, burnt, putrid. Depending on objective conditions (temperature, humidity, etc.) and functional state body (for example, daily fluctuations in sensitivity: during the day it is lower than in the morning and evening) and the direction of activity, the sensitivity of smell, for which a nine-point scale is usually used, can change quite significantly. Thus, sensitivity to odors increases markedly during pregnancy.
With sufficiently long contact of odorous substances with the nasal mucosa, adaptation occurs, leading to a decrease in sensitivity, but complete adaptation to a certain odor does not exclude sensitivity to others.
Dictionary of a practical psychologist. - M.: AST, Harvest. S. Yu. Golovin. 1998.
SMELL
(English) olfaction,smell sense) - type of chemical sensitivity(chemoreception), the ability to sense and distinguish odorous substances, e.g. smells food.
Odorous substances in the form of vapor, gas, mist, dust or smoke reach the receptors when inhaled through the nose or mouth. There is no single theory of the origin of O. Nominated stereochemical hypothesis(J. Eimour, 1964), according to which the interaction of molecules of an odorous substance with the membrane of the olfactory cell depends simultaneously on the spatial shape of the molecule and on the presence of certain functional groups in it. It is assumed that the olfactory pigment molecule can easily pass into an excited state under the influence of a vibrating molecule of an odorous substance. Olfactory receptors are excited by substances with molecular weights from 17 (ammonia) to 300 (alkaloids). According to this theory, there are 7 primary odors- camphor-like, floral, musky, minty, ethereal, putrid and pungent. Other odors (for example, garlic) are complex, consisting of several primary ones. Molecules with a camphor-like odor should have the shape of a ball with a diameter of about 0.7 nm, with a floral one - the shape of a disk with a handle, etc. The approximate sizes of the receptor “holes”, or nests, on the membrane of the olfactory cell, into which the molecules should enter, were calculated odorous substances.
Other receptors of the oral mucosa also participate in the formation of the olfactory sensation: tactile, temperature, pain. Substances that irritate only the olfactory receptors are called olfactory (vanillin, benzene, xylene), in contrast to mixed substances that also irritate other receptors (ammonia, chloroform). The range of odors perceived by humans is very wide; Many attempts have been made to systematize them. German psychologist H. Henning (1924) identified 6 main smells(fruity, floral, resinous, spicy, putrid, burnt), the relationship between which is reflected by the so-called. prism of smells. Later, the inaccuracy of Henning’s classification was shown, and now they use a scheme of 4 main smells(fragrant, sour, burnt, putrid), the intensity of which is usually measured on a conventional 9-point scale.
O. in one and the same subject can fluctuate within wide limits. With prolonged contact of odorous substances with the mucous membrane, adaptation is observed - a decrease olfactory sensitivity. The time it takes for different subjects to adapt to different odors varies. As the concentration of substances increases, it decreases, so people who deal with strongly odorous substances soon get used to them and stop feeling them. Full adaptation to one odor does not exclude sensitivity to others. The intensity of the odor depends on temperature and humidity. O. is subject to regular fluctuations: during the day the sensitivity is less than in the morning and evening. O. intensifies during pregnancy. see also , , , , .
Editor's addition: The etymology of the word “O.” deserves mention: its common Slavic root He related to Indo-European root an(verb “to breathe”), which forms in lat. language animus - “soul”,"spirit", in Greek anemos -"wind", in Sanskrit aniti- “breathes.”
Big psychological dictionary. - M.: Prime-EVROZNAK. Ed. B.G. Meshcheryakova, acad. V.P. Zinchenko. 2003 .
Smell
SMELL (With. 407)
Maurice Maeterlinck once remarked: “The sense of smell is the only luxury in the field of senses that nature has provided us with.” At the same time, the Belgian playwright and poet probably meant that, compared to, say, touch, sight or hearing, smell plays no role important role and serves as an optional addition to the main sense organs. It seems, however, that the famous writer was seriously mistaken. Recent studies by physiologists and psychologists have shown that the role of smell in a person’s perception of the world and behavior is clearly underestimated. Smells have a strong influence on us, which, however, the person himself is aware of vaguely and indefinitely. But in fact, many of our actions and moods, likes and dislikes owe their origin to smells.
If you ask any person a simple question: “What smells are there?” - then the answer will probably also be short and simple: “Pleasant and unpleasant.” However, such a response is completely inexplicable from a physiological point of view, since for the body most odors appear as neutral. Of course, the fumes of toxic substances have a specific odor, which is clearly perceived as unpleasant, because it poses a threat of poisoning. But many odors do not contain any threat, and on the other hand, they are too ephemeral to deliver tangible benefits to the body. Nevertheless, we unconsciously avoid some smells, while others we inhale with pleasure. Why?
In most cases, positive or negative emotional coloring a particular smell acquires in connection with the experience that was associated with it when it was first perceived. Perceived again, this smell can awaken even very old moods and feelings. This psychophysiological mechanism was known in ancient times. Indian Brahmins wore small bottles with rare incense on their belts in order to... capture in their memory the most vivid and pleasant events of their lives. When something particularly desirable happened, the Brahmin would put one of the bottles to his nose, and the strong aroma would become firmly associated with a joyful feeling. Subsequently, even years later, especially when faced with grief and adversity, it was enough to uncork the treasured bottle again for good memories to come flooding back with amazing brightness.
We inhale the aroma of freshly cut hay, and a bright feeling of genuine childish joy, experienced once in the summer in the village, is born in our memory. But from an early age, we associate the smell of medicine with pain. Therefore, novice doctors need a long hardening to learn not to react to the smell that seems to emanate from hospital walls.
All these combinations are born according to the law discovered by Aristotle - the concatenation of associations. As it turned out, this is not difficult to prove experimentally. The English psychologist Michael Kirk-Smith presented several subjects with a task that was clearly beyond their strength. While working, their sense of smell was exposed to an unfamiliar odor. When they were later given the same substance to smell, the smell aroused in them negative emotions associated with the failure they had experienced. People's mood unaccountably deteriorated and they gave up.
Possibly, odors can be used in practical purposes- to stimulate people's desired drives and motivations through positive associations. British perfumers did this experiment several years ago. They proceeded from the fact that traditional perfume aromas are too abstract and vague and do not evoke clear positive associations. What can cause them? Of course, the flavors are healthy delicious food. Special perfumes were developed that imitate the aroma of freshly baked buns, ripe fruits and fresh milk. Perfume with the smell of smoked salmon and steak was specially created for men. Alas, experimental testing of the new product demonstrated its complete fiasco. Men and women, when meeting with a suitably perfumed partner, fell into extreme bewilderment. There was no talk of any mutual attraction. Thus, it turned out that mutual attractiveness has nothing to do with food associations. So with what?
Ethologists who study animal behavior have long figured out how our little brothers use the sense of smell to communicate with members of their species. For these purposes, they secrete the secretions of certain glands, “marking” with them the boundaries of their territory or attracting a partner for mating. These secretions are therefore called “social hormones” or pheromones.
Although our olfactory system is amazingly sensitive, humans and other primates smell much less well than most other animal species. Some scientists suggest that our distant ancestors lost their sense of smell when they rose from the ground to the trees. Since visual acuity was more important there, the balance between various types feelings have shifted. During this process, the shape of the nose changed and the size of the olfactory organ decreased. It became less subtle and did not recover even when man's ancestors came down from the trees again.
Nevertheless, we have not completely lost the ability to distinguish each other’s smells. Apparently, each of us has our own individual smell, which allows other people to more or less unconsciously identify us with our “nose”. Some smells attract us, others unconsciously repel us. It is probably important in communication that partners find pleasant smell each other, even if they are not aware of the fact that they distinguish it (it’s not for nothing that people use the expression “sniffed”).
Interestingly, women are much more sensitive to odors than men. American researchers have long noticed that female police officers sitting in ambush sense burglars a little earlier than male police officers. Such a keen sense of smell may be the only one scientific explanation famous female intuition.
The saying that people are greeted by their clothes was probably invented by men. Women “meet” mainly by smell. By subconsciously analyzing the whole range of odors emanating from her counterpart, a woman determines her attitude towards him. Intuition tells me: this one is a coward or, on the contrary, a fearless person, this one is a good-natured person, but he lacks determination, this one is a miser and a bore, and this one is just a scoundrel, but I like him, nothing can be done.
True, in modern city there are many “buts”. One of them is the passion of men for various perfumes, which “throws off the scent” women's intuition. Back in the late 70s. In England, aerosols containing the male pheromone androsterone became fashionable. It was assumed that they unconsciously attracted and aroused women, causing them to perceive perfumed men as very sexy. Numerous experiments have confirmed that this aerosol indeed has a sexually attractive and arousing effect.
However, if a man is left to his own devices in choosing deodorants, lotions and colognes, he most often chooses a scent that suits his character, and he also does this intuitively. Here are some research results on the relationship between odors and male character.
Unpredictable, cheerful and sociable men mainly love oriental, nutmeg and aldehyde scents.
Equally unpredictable in their actions, but prone to melancholy, peace and stability, they prefer sweet floral scents.
Balanced, energetic, confident men love chypre, floral-mossy and fruity scents.
Ambitious and rather secretive men prefer aldehyde-floral and dry scents.
Specially selected aromas can also bring considerable benefits in everyday life and at work. Thus, Japanese psychologists recommend saturating the air in work areas with the aromas of flowers and fruits. Experiments have proven that the aroma of lemon, jasmine and eucalyptus improves performance and reduces drowsiness. The effect on computer system operators is especially pronounced - the smell of jasmine reduces errors when working with the keyboard by 30%, and lemon - by 50%. Many companies have introduced aromatic prophylaxis to protect specialists who work daily in front of a computer screen from overexertion. Recently, the Tokyo headquarters of construction firm Kajima installed a computer-controlled ventilation system that spreads programmed scents throughout the building. In the morning, in order to relieve transport fatigue from employees and shorten the period of “swinging”, the smell of lemon is introduced into the ventilation, during the lunch break - the soothing aroma of roses, in the afternoon, when one is getting sleepy, - invigorating smells. essential oils and resins from various trees. Other companies are planning to follow Kajima's example.
Popular psychological encyclopedia. - M.: Eksmo. S.S. Stepanov. 2005.
Synonyms:See what “smell” is in other dictionaries:
Smell- Sense of smell, the sense of smell, the ability to determine the smell of substances dispersed in the air (or dissolved in water for animals living in it) [source not specified 672 days]. U vertebrate organ the sense of smell is... ... Wikipedia
sense of smell- Cm … Synonym dictionary
SMELL- SMELL, sense of smell, pl. no, cf. 1. One of the five external senses, the ability to sense and recognize smells. Subtle sense of smell. Olfactory organs. 2. Action under Ch. smell (rare). Dictionary Ushakova. D.N. Ushakov. 1935 1940 … Ushakov's Explanatory Dictionary
SMELL- perception by the body through the olfactory organs of certain properties (smell) decomp. substances present in environment. Animals inhabiting land perceive odorous substances (OS) in the form of vapors, and inhabitants of reservoirs in the form of water... ... Biological encyclopedic dictionary
sense of smell- SMELL, sniff, sense INHALATION, sniffing books. SMELL, inhale/inhale, sniff/smell... Dictionary-thesaurus of synonyms of Russian speech
