The difference between the sense of smell and other senses. Signal processing in the olfactory bulb. Interesting facts about the sense of smell: how people perceive odors

The senses are very important to all of us. A person’s sense of smell can make the perception of the world much brighter.

The role of the olfactory organ

The organ of smell is the nose, which serves us so that we can enjoy wonderful smells and aromas. He also warns us about various kinds dangers (fire, gas leak). A good sense of smell is very important for any person, since without it it is impossible to perceive the world 100%. So, with a poor sense of smell, life can become gray and dull, devoid of all colors.

The organ of smell is a tool for obtaining information; it helps a person to understand the world. It is known that children whose perception of smells is impaired cannot develop properly and lag behind their peers. The human olfactory organ is closely related to the taste organ. A very small loss of the ability to subtly feel and distinguish odors negates the pleasure of the tasty food. And people often choose their surroundings by smell. Probably no one will be able to communicate with a person for a long time if his aroma is not very pleasant.

The olfactory organ, helping us to perceive odors, is able to create mood and influence well-being. For example, cinnamon and mint scents can increase alertness and reduce irritability, while coffee and lemon scents can help promote clear thinking. The human olfactory organ has the ability to distinguish up to 10,000 aromas. This wealth given to us by nature must be treasured. None of the people wants to stop smelling flowers, herbs, forests, and the sea.

What is the sense of smell?

The ability to distinguish and perceive various odors of substances that are in environment, is the sense of smell. Recognition of odors usually provokes the emergence of various emotions. In this sense, the sense of smell often becomes more important than, for example, good hearing or excellent vision. The impact of various aromatic substances on the olfactory organ can excite the human nervous system. This, in turn, leads to changes in functions different organs and systems of the whole body.

Organ structure

The organ of smell is the nose, which perceives appropriate stimuli dissolved in the air. The process of smell consists of:

olfactory mucosa;
olfactory filament;
olfactory bulb;
olfactory tract;
cerebral cortex.

The olfactory nerve and receptor cells are responsible for the perception of odors. They are located on the olfactory epithelium, which is located on the mucous membrane of the upper posterior part of the nasal cavity, in the area of the nasal septum and the upper nasal passage. In humans, the olfactory epithelium covers an area of about 4 cm2.

All signals from the receptor cells of the nose (of which there are up to 10 million) through nerve fibers enter brain. There the idea of the nature of the smell is formed or its recognition occurs.

In humans, there are olfactory and trigeminal nerves, to the endings of which odor receptors are attached. Nerve cells have two types of processes. The short ones, called dendrites, are rod-shaped, each containing 10-15 olfactory cilia. Others, the central processes (axons), are much thinner, forming thin nerves that resemble threads. These very threads penetrate into the cranial cavity, using for this purpose the holes in the plate of the ethmoid bone of the nose, and then join the olfactory bulb, which passes into the olfactory tract. The bulb lies at the base of the skull and forms a special lobe of the brain.

The visceral brain system, or limbic system, includes cortical areas olfactory analyzer. These same systems are responsible for the regulation of innate activity - search, food, defensive, sexual, emotional. The visceral brain is also involved in maintaining homeostasis, regulating vegetative functions, formation of motivational behavior and emotions, organization of memory.

Peculiarity

The olfactory organ is capable of influencing the thresholds of color perception, taste, hearing, and excitability vestibular apparatus. It is known that if a person’s sense of smell sharply decreases, then the pace of his thinking slows down. The structure of the olfactory organ is special; it distinguishes it from other senses. All structures of the olfactory analyzer take an important part in organizing emotions, behavioral reactions, memory processes, autonomic-visceral regulation, and regulation of the activity of other areas of the cerebral cortex.

There are substances that have pungent odor(ammonia, vinegar essence). They are capable of exerting both an olfactory effect and an irritation on sensitive fibers trigeminal nerve. This explains the specificity of the formation of odor sensations. Respiration rate, pulse, and blood pressure can reflexively change under the influence of olfactory stimuli.

Organ sensitivity

The acuity of smell can be judged by the fact that a person is able to clearly perceive, for example, the smell of 0.0000000005 parts of a gram of rose oil or musk, approximately 4.35 parts of a gram of mercaptan gas. If the air contains even 0.00000002 g per 1 cm 3 of hydrogen sulfide gas, then it is clearly noticeable to us.

There are odors that are very powerful and persistent and can even be stored for 6-7 thousand years. An example of this is the smells that were felt by the people who participated in the excavations Egyptian pyramids. We can say that our nose is capable of detecting various impurities of odorous substances in very small quantities in the inhaled air, which cannot be measured even through chemical research. It has been proven that the acuity of smell depends on the time of day (smells are better sensed after sleep) and physiological state person. The sense of smell is more acute when a person is hungry, as well as during spring and summer.

The human olfactory organ is capable of distinguishing no more than several thousand different shades of odors. In this we are very far behind animals. Dogs, for example, can recognize about 500 thousand odors.

Smell and emotions

Brain research suggests that the hemispheres gradually formed from the olfactory brain in the process of evolution forebrain who are responsible for higher nervous activity. Smell is the primary source and way of transmitting various information among creatures in living nature. In addition, for all animals and for primitive man, the organ of smell is necessary for finding food, a sexual partner, warning of danger or marking a habitat.

For a person living in modern world, the main method of transmitting information becomes verbal, which was able to supplant all others that arose earlier. Odor is known to have a powerful effect on emotional sphere, as well as processes associated with it. This influence often occurs at the subconscious level. This experience in a person's life is not always positive. For example, manifestations of diseases in the form of psychosomatic diseases are recorded.

Great importance of smell

The functions of the olfactory organ are numerous in the life of all living beings, as it is able to warn of the danger of poisoning by poisonous gases that can enter the body through the lungs. It is also possible to control the quality of food consumed using smell, which protects against the entry of decomposed and poor-quality products into the gastrointestinal tract.

Conclusion

As a conclusion we can say that close connection long-term memory, emotions and sense of smell indicate that smell is a powerful tool impact on the entire human body and his worldview as a whole.

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 outside world that 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 from the first hours of life, and at the 7th–8th month of life he develops conditioned reflexes to “pleasant” and “unpleasant” odors.

A person can perceive more than 10,000 odors. Some of them can excite or discourage appetite, change mood and desires, increase or decrease performance, and even force you to buy something you don’t really need. 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 have 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. The peripheral processes of the receptor cells of the olfactory epithelium end 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 last decade It became 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 travels through the olfactory nerve to the brain, where its final analysis occurs.

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. A particularly noticeable decrease in the acuity of smell occurs 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 natural gas used in everyday life (which in itself does not smell like anything from a human point of view) specifically so that its leak can be detected 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 male axillary sweat 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 of different cultures may perceive the same odors differently. Such differences were revealed in a completely unique survey conducted in 1986 by National Geographic magazine. 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 those who responded 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 sent their answers to National Geographic various reasons completely lost their sense of smell. It turns out that there are a lot of such people, including among young people. According to National Institute US health in 1969, smell disturbances were noted in 2 million people, and by 1981 this figure had increased to 16 million! This situation is largely due to the deterioration of the 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 of drugs, 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.

“He drank this smell, drowned in it, was saturated with it until the very last internal pore”
Patrick Suskind, "Perfume"

“Live a life in which you notice the smell of salty sea water carried by the cold breeze and the red-tailed hawk soaring proudly over the lake,” advises the famous American writer Anna Quindlen in her book “A Quick Guide to happy life"(Short Guide to a Happy Life).

Susan Sontag, theater and film director, literary and art critic, and successful writer, says that some of her favorite things are the smells of freshly cut grass and washed clothes.

John Steinbeck, an American prose writer, author of many world-famous stories and novels, in his book “East of Eden” (1952) writes: “Perhaps all your past life was gray, you lived in a gloomy, dull land, among gloomy, dull trees. But suddenly inspiration came! And now the cricket’s song captivates your ears, the earth sends you its scents, and the ripples of the sun, sifted through the foliage, caress your eyes.”

Any memory you have is somehow connected with some smells. American writer, poet and historian Diane Ackerman, who became famous thanks to the book “ Natural history feelings" (A Natural History of the Senses), writes the following about this phenomenon:

“A person’s sense of smell is almost always unmistakable, but you will not be able to describe to another person a smell that is unfamiliar to him...

We see something only when there is enough light around us, we hear only when the sound is loud enough, we taste it when food is in our mouth. But we always smell. Every breath is a new palette of aromas.

Close your eyes and you won't be able to see anything, close your ears and for a few seconds the world will fall silent. Stop breathing and you die."

Illustration by Wendy MacNaughton for the book “The Essential Scratch and Sniff Guide to Becoming a Wine Expert” by Richard Betts

Every day a person takes 23,040 inhalations and exhalations, consuming 438 cubic feet of air, inhaling which he always smells a variety of odors emanating from trees, flowers, earth, animals, food, other people, industrial activities, etc. However, when trying To describe this or that aroma, we always resort to some ephemeral comparisons, like “it was like the smell of apple blossoms” or “in my opinion, it smells a little like ammonia.”

The reason is that the connection between the speech center and the set of structures in the telencephalon associated with the perception of odors is too weak, which cannot be said about the connection between the olfactory brain and the hippocampus (part of the limbic system responsible for long-term memory).

“When I bring a violet to my nose, the molecules of its aroma penetrate into upper area my nasal cavity, where the olfactory receptor cells, forming the olfactory epithelium, lie in the thickness of the mucous membrane. Each receptor cell has about 10-12 thin processes (“cilia”), the main function of which is to capture molecules of odorous substances. As a result of such contact in the receptor cell it gives rise to nerve impulse, which along the olfactory filament (central processes of receptor cells) rushes into the brain.

Unlike neurons eyeball And inner ear“, damage to which leads to an irreparable deterioration in the functioning of both organs, damage to the olfactory epithelium does not pose any threat, since the receptor cells are completely renewed every 2-4 weeks.”

Smell is one of the most powerful emotional triggers. For example, it is enough for a person to simply smell the scent of his beloved for him to begin to experience pleasant excitement.

“Smell can awaken the most powerful memories, images and seemingly long-forgotten sensations. When you give a person perfume, you give him liquid memory. Kipling was absolutely right: “Spirits make the heartstrings tingle more than sounds and sights.”

In her book “The Natural History of Senses,” Diana Ackerman classifies the main natural odors and explains why synthetic perfume compositions are more popular than natural ones:

“All odors fall into several main categories: minty (mints), floral (roses), ethereal (pears), musky (musk), resinous (camphor), repellent (rotten eggs) and pungent (vinegar). However, since most perfumes today are created synthetically, there is virtually no need for natural substances.

As you know, the first artificial perfume created on an aldehyde basis was the iconic Chanel No. 5. When a journalist asked Marilyn Monroe in 1954 what she wore to bed, the actress flirtatiously replied, “A few drops of Chanel No. 5".

The top note of the popular women's fragrance is aldehyde (a synthetic floral scent) - you smell it first. Then your nose picks up the middle notes (jasmine, rose, ylang-ylang and lily of the valley) and finally the base, often called the “dry-down” (vetiver, vanilla, oakmoss, sandalwood, amber, musk and patchouli).”

Not all objects around us have their own smell, since one of the main conditions for its occurrence is the volatility of a substance (the property of molecules to break away from the surface of liquid and solids). Thus, when entering outer space, astronauts lose the ability to sense taste and smell, since in conditions of weightlessness the evaporation process occurs several times slower.

It's no secret that a person distinguishes only 4 basic tastes - salty, sour, bitter and sweet. That is, the majority taste qualities food is determined by nothing more than its smell. Judge for yourself: most often the desire to taste “something tasty” is caused by some pleasant aroma. :)

Some chemists went so far in developing this theory that they began to argue that wine is an absolutely tasteless liquid saturated with various aromas. According to this hypothesis, a person suffering from a runny nose is unable to distinguish wine from plain water. :)

Today there is great amount research that explains how the human olfactory system works. But despite the fact that the number of undisclosed secrets still remains large, we can be absolutely sure of one thing - in the lives of each of us, smells play far from a minor role. :)

The human nose, namely the part of it that is responsible for the sense of smell, is the least studied in the human body. Scientists are still trying to establish all the physiological subtleties of this function. human body. Some researchers believe that the ability to perceive odors is a vestige, that is, in the process of evolution it has lost its functional importance for humans. However, it is the olfactory system that helps a person navigate space, stimulate taste buds, and even determine whether we have a physical attraction to a person. That is why the mystery of smell is another interesting and still not fully solved mystery of nature.

The structure of the olfactory system: receptors that perceive odors

Olfactory cells, which are smell receptors, are located in the olfactory region of the nose. This area is an area in the superior turbinate and upper part of the nasal septum, occupying 2.5 cm². All these cells are bipolar neurons in structure, and at the tips of their dendrites there are hairs immersed in the mucus of the nasal cavity. When they dissolve in this mucus chemical substances, olfactory receptors perceive them in the form of a sensation of smell. Olfactory cells are the primary receptors physiological mechanisms activation of which leads to an increase in the perceived signal. Unlike the taste perception system, in the olfactory system it is impossible to distinguish a small amount of main primary odors. There are probably a lot of such odors and there is no single classification of them today.

The main pathways and centers of the olfactory system

The olfactory system has fundamental differences from other sensory systems: it does not have a spinal-stem region and most of the olfactory pathways that go to the cerebral cortex do not pass through the thalamus. The structure of the olfactory system is as follows:

axons of olfactory cells pass through ethmoid bone about twenty thin filaments that form the olfactory nerve and end in the olfactory bulbs;
from the olfactory bulbs the olfactory pathways pass through the olfactory tracts;
Then the olfactory pathways diverge in three directions:

to the medial olfactory area, which is the most ancient and is responsible for primitive reactions to odors, for example, excretion, licking saliva, and so on;
to the lateral olfactory area, which is responsible for complex behavioral acts;
into the orbital gyri of the frontal lobe, presumably responsible for the conscious perception of odors.

Interesting facts about the sense of smell: how people perceive odors

Since smell is an understudied sense organ, scientists are still discovering many interesting facts related to this function of the human body. Here are some established interesting facts about the sense of smell:

It is with the help of scent receptors that people are able to detect each other's pheromones: individual chemical substances produced by the body of each person. It is pheromones that make us be attractive to each other and arouse sexual desire: the smell of the person you loved will never be confused;
the sense of smell is much better developed in women than in men: women are able to distinguish much large quantity smells, however, the best perfumers, as it happened historically, were men;
the sense of smell changes during a woman’s menstrual cycle: before and after ovulation it intensifies, and women during this period react sharply to the aroma of male pheromones. This is not surprising, because it is during this period of the menstrual cycle that the likelihood of conceiving a child is highest;
Infants' sense of smell is very developed, but during the first year the olfactory system loses almost half of its function. There is also atrophy of the olfactory fibers in elderly people;
The right nostril of a person perceives odors more acutely in right-handed people, while the left nostril perceives odors more acutely in left-handed people.

the sense of smell is the best way determine whether you really want to eat. If the smell of food does not seem too attractive, this means that the body is quite saturated at the moment.

Answer: The organ of smell is located in the nasal cavity at the beginning of the respiratory tract. It occupies an area equal to that of a small coin in the upper sinus and nasal septum.

The structure of the olfactory analyzer?

Answer: As is known, the olfactory region is located in the upper part of the nasal cavity, the so-called olfactory fissure. The space delimiting this area is the septum, the superior and middle conchae, and the cribriform plate. The mucous membrane covering this area differs from the rest of the mucous membrane of the nasal cavity by brown spots, which receive their color from the pigment contained in the olfactory cells: these spots or islands generally occupy 250 mm2 of area and have an irregular shape. There is no exact determination of the area of distribution of the olfactory part of the nasal mucosa containing pigment; this area varies among individuals, sometimes occupying part of the superior turbinate and nasal septum, sometimes moving to the middle turbinate. The olfactory pigment is apparently similar to the pigment of the retina, and its disappearance leads to a loss of smell, which is observed in old people, in people with a disease of the epithelium of the olfactory fissure itself.

Where is the cortical center of smell located?

Answer: Central department - cortical olfactory center, located on the lower surface of the temporal and frontal lobes of the cerebral cortex. The olfactory cortex is located at the base of the brain, in the region of the parahippocampal gyrus.

Organ of taste

What is the taste organ?

Answer: Taste receptors consist of neuroepithelial cells, contain branches of the taste nerve and are called taste buds.

Taste buds (gemma gustatoria) have an oval shape and are located mainly in the leaf-shaped, mushroom-shaped and grooved papillae of the mucous membrane of the tongue (see section “Digestive system”). They are present in small quantities in the mucous membrane of the anterior surface soft palate, epiglottis and back wall throats.

Irritations perceived by the bulbs enter the nuclei of the brain stem, and then to the region of the cortical end of the taste analyzer.

Receptors are able to distinguish four basic tastes: sweet is perceived by receptors located at the tip of the tongue, bitter - by receptors located at the root of the tongue, salty and sour - by receptors at the edges of the tongue.

Where is the taste organ located?

Answer: The organ of taste (organum custus) is a peripheral section of the taste analyzer and is located in the oral cavity.

The structure of a taste analyzer?

Where is the cortical taste center located?

General body cover

What is the importance of skin for the human body?

Human skin has a complex structure and performs a number of important functions. It covers the entire surface of the body and reliably protects it from negative impact external factors. Due to the structural features of the epidermis, it prevents the penetration of pathogenic bacteria, harmful chemical compounds, water and various contaminants into the body. In addition, the skin protects internal organs from mechanical injuries, temperature and other physical influences. Melanin, a special skin pigment, neutralizes the harmful effects of ultraviolet rays

Name the layers and appendages of the skin indicated by numbers in the figure?

stratum corneum

What formations perceive pain, where are these formations located?

Answer: Pain sensations are perceived by nociceptors

What formations perceive touch, where are these formations located?

Answer: The organ of touch perceives tactile irritations resulting from touching or pressing objects on the skin. Afferent innervation of the skin is carried out by nerve fibers coming from sensory neurons of the spinal ganglia. The dendrites of sensory neurons form tactile receptors that are found in the skin.

What formations perceive pressure, where are these formations located?

Answer: When the organs of touch and pressure are applied to the mechanoreceptors of the skin, the energy of the stimulus is transformed into nervous excitation, which is transmitted through a chain of neurons from the peripheral part of the skin analyzer to its cortical part - to the posterior central gyrus. The sensitivity of the skin of the legs is projected in the upper part, the sensitivity of the arms and torso is projected in the middle, and the scalp is projected in the lower part.

What formations perceive the feeling of heat, where are these formations located?

What formations perceive the feeling of cold, where are these formations located?