Sense organs are specialized structures through which parts of the brain receive information from the internal or external environment. With their help, a person is able to perceive the world around him.
Sense organs - afferent (receptive) section of the analyzer system. The analyzer is the peripheral part of the reflex arc, which communicates between the central nervous system and the environment, receives irritation and transmits it through pathways to the cerebral cortex, where information is processed and sensation is formed.
5 human senses
How many primary senses does a person have?
In total, a person usually has 5 senses. Depending on their origin, they are divided into three types.
- The organs of hearing and vision come from the embryonic neural plate. These are neurosensory analyzers, they belong to first type.
- The organs of taste, balance and hearing develop from epithelial cells, which transmit impulses to neurocytes. These are sensory epithelial analyzers and belong to second type.
- Third type includes peripheral parts of the analyzer that sense pressure and touch.
Visual analyzer
The main structures of the eye: the eyeball and auxiliary apparatus (eyelids, muscles of the eyeball, lacrimal glands).
The eyeball has an oval shape, is attached by ligaments, and can move with the help of muscles. Consists of three shells: outer, middle and inner. Outer shell (sclera)- this protein shell of an opaque structure surrounds the surface of the eye by 5/6. The sclera gradually passes into the cornea (it is transparent), which makes up 1/6 of the outer shell. The transition area is called the limb.
Middle shell consists of three parts: the choroid, the ciliary body and the iris. The iris has a colored color, in the center of it there is a pupil, thanks to its expansion and contraction, the flow of light to the retina is regulated. In bright light, the pupil narrows, and in low light, on the contrary, it expands to catch more light rays.
Inner shell- this is the retina. The retina is located at the bottom of the eyeball and provides light and color perception. The photosensory cells of the retina are rods (about 130 million) and cones (6-7 million). Rod cells provide twilight vision (black and white), cones serve for daytime vision and color discrimination. The eyeball contains a lens and chambers of the eye (anterior and posterior).
The value of the visual analyzer
With the help of the eyes, a person receives about 80% of information about the environment, distinguishes colors and shapes of objects, and is able to see even with minimal light. The accommodative apparatus makes it possible to maintain clarity of objects when looking into the distance or reading closely. Auxiliary structures protect the eye from damage and contamination.
Hearing analyzer
The organ of hearing includes the outer, middle and inner ear, which perceive sound stimuli, generate an impulse and transmit it to the temporal cortex. The auditory analyzer is inseparable from the organ of balance, so the inner ear is sensitive to changes in gravity, vibration, rotation, and movement of the body.
Outer ear It is divided into the auricle, auditory canal and eardrum. The auricle is an elastic cartilage with a thin ball of skin that detects sound sources. The structure of the external auditory canal includes two parts: cartilaginous at the beginning and bone. Inside there are glands that produce sulfur (has a bactericidal effect). The eardrum receives sound vibrations and transmits them to the structures of the middle ear.
Middle ear includes the tympanic cavity, inside which are located the hammer, stirrup, incus and Eustachian tube (connects the middle ear with the nasal part of the pharynx, regulates pressure).
Inner ear It is divided into a bony and membranous labyrinth, with perilymph flowing between them. The bony labyrinth has:
- vestibule;
- three semicircular canals (located in three planes, provide balance, control the movement of the body in space);
- cochlea (it contains hair cells that perceive sound vibrations and transmit impulses to the auditory nerve).
The value of the auditory analyzer
Helps to navigate in space, distinguishing noises, rustles, sounds at different distances. With its help, information is exchanged when communicating with other people. From birth, a person, hearing oral speech, learns to speak. If congenital hearing impairment occurs, the child will not be able to speak.
The structure of the human olfactory organs The receptor cells are located at the back of the upper nasal passages. Perceiving odors, they transmit information to the olfactory nerve, which delivers it to the olfactory bulbs of the brain.
With the help of smell, a person determines the good quality of food, or senses a threat to life (carbon smoke, toxic substances), pleasant aromas lift the mood, the smell of food stimulates the production of gastric juice, promoting digestion.
Organs of taste
On the surface of the tongue there are papillae - these are taste buds, on the apical part of which there are microvilli that perceive taste.
The sensitivity of receptor cells to food products is different: the tip of the tongue is susceptible to sweets, the root to bitter, the central part to salty. Through nerve fibers, the generated impulse is transmitted to the overlying cortical structures of the taste analyzer.
Organs of touch
A person can perceive the world around him through touch, with the help of receptors on the body, mucous membranes, and muscles. They are able to distinguish temperature (thermoreceptors), pressure levels (baroreceptors), and pain.
Nerve endings are highly sensitive in the mucous membranes and earlobe, and, for example, the sensitivity of receptors in the back area is low. The sense of touch makes it possible to avoid danger - to remove your hand from a hot or sharp object, determines the degree of pain threshold, and signals an increase in temperature.
Plan:
1. VISUAL APPARATUS 1
2. HEARING ORGAN 14
3. OLfactory Organ 24
4. TASTE ORGAN 28
5. List of used literature 33
SENSE ORGANS
Sense organs are anatomical formations that perceive any external influence (light, sound, smell, taste, etc.) and convert it into a nerve impulse, which is then transmitted to the brain, where the cortical sections of sensation analyzers are located. Each analyzer includes: 1) a peripheral device that perceives external influence and transforms it into a nerve impulse; 2) the pathways through which the nerve impulse enters the brain; 3) the nerve center in the cerebral cortex (the cortical end of the analyzer, where external influences are analyzed and the relationship of the body with the external environment is comprehended). The perception of external influence can be direct, or contact: sense of touch (tactile), pain, temperature, taste, and remote(at a distance): sense of sight, hearing, smell. Thus, with the help of the senses, a person receives all the information about the world around him, studies it and responds to external influences with specific actions.
VISUAL APPARATUS
visual apparatus, apparatus visus , is of great importance in the process of perceiving the surrounding world. In evolutionary terms, the visual apparatus has gone from the simplest light-perceiving cells to a complex organ capable of moving, conducting and changing the light flux, directing it to special light-sensitive cells, perceiving black-and-white and color images, seeing an object in volume and at different distances. The visual apparatus is located in the orbit, the walls of which play a protective role, and consists of the eye and auxiliary organs (eyelids, lacrimal apparatus and oculomotor muscles).
Eye , oculus (Fig. 1), consists of the eyeball and the optic nerve with its membranes. Eyeball, bulbus oculi, spherical, with two protruding poles - anterior and posterior.
Rice. 1. The structure of the eyeball.
1 - fibrous membrane; 2 - choroid; 3 - veins of the eyeball; 4 - retina; 5 - optic nerve; 6 - vitreous body; 7 - conjunctiva; 8 - ciliary muscle (meridional fibers); 9 - ciliary muscle (circular fibers); 10 - lens, 11 - cornea; 12 - anterior chamber of the eye; 13 - iris; 14 - muscle that constricts the pupil; 15 - muscle that dilates the pupil; 16 - venous sinus of the sclera; 17 - ciliary body; 18 - ciliary processes.
Anterior pole corresponds to the most protruding part of the outer fibrous membrane (cornea), and rear- the most protruding part located lateral to the exit point of the optic nerve. The line connecting these points is called outer axis eyeball. The line connecting a point on the inner surface of the cornea (corresponding to the anterior pole) with a point on the surface of the inner (sensitive) shell of the eye - the retina (corresponding to the posterior pole) is called internal axis of the eyeball. If the relationship between the lengths of the outer and inner axes of the eyeball is disrupted (occurs when the light-refractive properties of its parts change), the image of objects is focused either in front of the retina (myopia, myopia) or behind it (farsightedness, hyperopia); in both cases, vision correction is required (focusing the image on the retina), achieved by wearing glasses. The visual axis of the eyeball is also distinguished - the line connecting its anterior pole with the central fovea of the retina (the point of best vision).
The eyeball consists of membranes: outer fibrous, middle vascular, and internal sensitive (retina), and the nucleus of the eye (aqueous humor of the anterior and posterior chambers, lens, vitreous).
The fibrous membrane of the eyeball, tunica fibrosa bulbi, is an outer dense membrane that performs protective and light-transmitting functions. The front, smaller, transparent part is called cornea. The back, large part has a whitish color, is opaque and is called sclera. The boundary between the cornea and sclera is the circular scleral groove, sulcus sclerae.
The cornea, cornea, is one of the transparent, light-conducting and light-refracting media of the eye; it is a convex-concave (in the form of a watch glass) round plate, devoid of blood and lymphatic vessels. It is nourished by the aqueous humor of the anterior chamber of the eye. The cornea consists mainly of a special dense fibrous connective tissue called the substantia propria (stroma), covered on the outside with stratified squamous non-keratinizing epithelium, and on the inside with single-layer squamous epithelium (endothelium) of the cornea. The cornea contains a large number of nerve endings, which causes the eyelids to reflexively close at the slightest touch.
The sclera, sclera, consists of dense fibrous connective tissue and performs protective and supporting functions. The visible part of the sclera in the area of the palpebral fissure is covered with epithelium, which passes into the epithelium of the conjunctiva of the eye. In the area of transition of the sclera into the cornea (limb) there are small, irregularly shaped, branched cavities lined with endothelium, communicating with each other and forming venous sinus of the sclera(Schlemm's canal), which ensures the outflow of aqueous humor from the anterior chamber of the eye. In its posterior part there are numerous openings through which vessels pass and bundles of optic nerve fibers emerge. The extraocular muscles are attached to the sclera.
The choroid of the eyeball, tunica vasculosa bulbi, contains a large number of blood vessels, providing nutrition to the retina and the release of aqueous humor. It regulates the intensity of the light flux and the curvature of the lens. The choroid consists of the choroid itself, the ciliary body and the iris.
The choroid itself, choroidea, makes up most of the choroid and lines the inside of the posterior part of the sclera. It is formed by vessels and connective tissue with pigment cells, loosely fused with the outer shell; between them there is a narrow gap - perivascular space.
The ciliary body, corpus ciliare, is the middle thickened part of the choroid, lying between the choroid proper and the iris in the form of a circular ridge behind the iris, with the outer ciliary edge of which the ciliary body is fused. The stroma (base) of the ciliary body is made up of loose connective tissue, rich in blood vessels and smooth muscle cells. The anterior section has radially directed eyelashes, processus ciliares, which consist mainly of vessels and form the ciliary crown, corona ciliaris. The radially located fibers of the ciliary girdle are attached to the latter, coming from the anterior and posterior surfaces of the lens. The posterior section has no processes, consists mainly of smooth muscle cells and is called ciliary circle. In the thickness of the ciliary body lies ciliary muscle, m. ciliaris, in which circular, radial and longitudinal (meridional) muscle fibers are distinguished.
The ciliary body produces aqueous humor in the anterior and posterior chambers of the eye and regulates its exchange. Contraction of the ciliary muscle leads to relaxation of the ciliary girdle, weakening the tension of the lens capsule, which leads to an increase in the curvature of the lens and an increase in its refractive power, which forms the basis of the accommodation mechanism (the ability to clearly see objects located at different distances from the eye).
The iris, iris, is the most anterior section of the choroid, has the shape of a disk with a diameter of 10-12 mm, placed in the frontal plane with an opening - pupil, pupilla, in the center. The iris consists of connective tissue with blood vessels, pigment cells that determine eye color, and muscle fibers located circularly and radially. In the iris there are: ne middle surface fades anterior, constituting the posterior wall of the anterior chamber eyes; pupillary edge, margo pupillaris, limiting the pupillary opening, back surface, fades posterior, constituting the anterior surface of the posterior chamber of the eye; ciliary edge, margo ciliaris, connecting to the ciliary body using the pectineal ligament, which fills the iridocorneal angle formed by the iris and cornea. Muscle fibers located radially in the thickness of the iris muscle that dilates the pupil m. dilatator pupillae, when contracting, they increase the opening of the pupil, and the circular fibers - pupillary sphincter, m. sphincter pupillae, contracting, reduce it.
The inner (sensitive) membrane of the eyeball, tunica interna bulbi, retina, retina, is tightly adjacent to the choroid along its entire length to the edge of the pupil. In the retina there is a posterior visual part, pars optica retinae, and a smaller anterior “blind” part that unites eyelash part, pars ciliaris, and iris part, pars iridica retina. The border between the parts of the retina is a clearly visible serrated edge, ora serrata, corresponding to the place of transition of the choroid proper into the ciliary circle of the choroid.
The visual part of the retina consists of an outer pigment part, pars pigmentosa, adjacent to the choroid, and an inner nervous part, pars nervosa. In the latter, up to 10 layers of nerve cells are isolated. The most important components of the inner part of the retina include neurosensory cells with processes in the form of cones and rods, which are the light-sensitive elements of the eyeball. It is in them that light quanta are transformed into nerve impulses. Cones perceive light rays in bright (daylight) light and at the same time are color receptors. These are predominantly daylight receptors. The total number in the human retina is 6-7 million. The absence of cone cells of one or another functional type causes congenital color blindness (color blindness). The rods function in twilight lighting (twilight light receptors) and are responsible for black-and-white vision. Their total number in the retina is 120 million. The remaining nerve cells play a connecting role. Their axons, connecting into one bundle, form the optic nerve, which exits the retina. In the posterior part of the retina there is the exit point of the optic nerve - the optic disc with a diameter of 1.5-1.7 mm. There are no light-receiving cells in it, so the area of the disc is called blind spot. In the center of the disc there is a depression where the trunks of the central arteries and veins of the retina emerge. Lateral to the optic disc there is a yellowish color spot, macula It corresponds to the posterior pole of the eye and is the place of best vision due to the accumulation of a large number of cones here (about 2500). There are no sticks in this place.
The five senses allow us to perceive the world around us and respond in the most appropriate way. The eyes are responsible for vision, the ears are for hearing, the nose is for smell, the tongue is for taste, and the skin is for touch. Thanks to them, we receive information about our environment, which is analyzed and interpreted by the brain. Usually our reaction is aimed at prolonging pleasant sensations or ending unpleasant ones.
Vision
Of all the senses available to us, we most often use vision. We can see through many organs: light rays pass through the pupil (hole), the cornea (a transparent membrane), then through the lens (a lens-like organ), after which an inverted image appears on the retina (the thin membrane in the eyeball). The image is converted into a nerve signal thanks to the receptors lining the retina - rods and cones, and is transmitted to the brain through the optic nerve. The brain recognizes the nerve impulse as an image, turns it in the right direction and perceives it in three dimensions.
Hearing
According to scientists, hearing- the second most used sense by a person. Sounds (air vibrations) penetrate the eardrum through the ear canal and cause it to vibrate. They then pass through the fenestra vestibule, an opening covered by a thin film, and the cochlea, a fluid-filled tube, irritating the auditory cells. These cells convert the vibrations into nerve signals that are sent to the brain. The brain recognizes these signals as sounds, determining their volume level and pitch.
Touch
Millions of receptors located on the surface of the skin and in its tissues recognize touch, pressure or pain, then send appropriate signals to the spinal cord and brain. The brain analyzes and deciphers these signals, translating them into sensations - pleasant, neutral or unpleasant.
Smell
We are able to distinguish up to ten thousand odors, some of which (poisonous gases, smoke) notify us of imminent danger. Cells located in the nasal cavity detect molecules that are the source of odor, then send corresponding nerve impulses to the brain. The brain recognizes these odors, which can be pleasant or, on the contrary, unpleasant. Scientists have identified seven main odors: aromatic (camphor), ethereal, fragrant (floral), ambrosial (the smell of musk - an animal substance used in perfumery), repulsive (putrefactive), garlicky (sulphuric) and, finally, the smell of burnt. The sense of smell is often called the sense of memory: indeed, a smell can remind you of a very long ago event.
Taste
Less developed than the sense of smell, the sense of taste informs about the quality and taste of the food and liquids consumed. Taste cells located on the taste buds, small tubercles on the tongue, detect flavors and transmit corresponding nerve impulses to the brain. The brain analyzes and identifies the nature of taste.
How do we taste food?
The sense of taste is not enough to appreciate food, and the sense of smell also plays a very important role. The nasal cavity contains two odor-sensitive olfactory areas. When we eat, the smell of food reaches these areas, which "determine" whether the food tastes good or not.
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Probably, in the first period of the existence of life on Earth, our planet seemed to living beings to be a completely dark, silent world. Gradually they learned to smell, taste, heat and cold, touch, thereby acquiring touch, smell, taste - the first external senses. With their help, ancient organisms searched for food and avoided dangers. Gradually, the world of colors and sounds opened up to the first creatures. The animals acquired a protective coloration and learned to quietly sneak up on prey or hide from the enemy. Their perception became more and more perfect, the world of living nature they perceived became more and more diverse.
Let's imagine that a person is standing on the seashore. The wind throws salty spray in his face. In front of him is endless blue and golden sun.
He listens to the sound of the sea, inhales its unique smell. A person feels strong and happy, feels every muscle, his entire body, standing firmly on the ground. A single image is born in his brain - the sea, which he will never forget.
1. VISUAL ORGAN
Through the organ of vision, a person receives the largest amount of information compared to other senses. “A tight fishing net thrown at the bottom of the eye glass and catching the sun’s rays” - this is how the wise Greek Herophilus imagined the retina of the eye. The retina, as the scientist has proven, is precisely a network that catches... individual, united and indivisible quanta of the radiant energy of the Sun. The quantum nature of absorption and the occurrence of radiation has now been established for the entire range of the electromagnetic spectrum. For the first time, the hypothesis about the occurrence of radiation in portions of energy was expressed in 1900 by the scientist Planck (1858-1947).
In terms of sensitivity, the eye approaches an ideal physical device, because It is impossible to create a device that would register energy of less than one quantum.
Where h is Planck's constant, equal to 6.624 * 10-27 erg * s
v - radiation frequency, s-1
Scientists - pioneers of atomic and nuclear physics - took advantage of this unique property of the eye. For centuries, science has been studying the eye, discovering more and more of its properties and secrets. An unsolved mystery, one of the most difficult and unexplored problems of modern physiology of the sense organs is color vision. It is completely unknown how the brain deciphers the color signals coming to it.
The eye is a complex optical system. Light rays enter the eye from surrounding objects through the cornea. The cornea in the optical sense is a strong converging lens that focuses light rays diverging in different directions. Moreover, the optical power of the cornea does not change and always gives a constant degree of refraction.
The sclera is the opaque outer layer of the eye; accordingly, it does not participate in conducting light inside
eyes.
It has been proven that the optics of the eye are just a window into which light quanta fly; that the retina and brain make the resulting image clear, three-dimensional, colorful and meaningful
But the human eye cannot perceive radiation beyond high intensity and distinguish short signals (lasting up to 0.05 s).
It is generally accepted that the average human eye, under average daylight conditions, perceives an extremely narrow (compared to the spectrum of possible radiation) range of wavelengths: from 380 to 780 nm (1 nanometer = 10-9 m) or (0.38 ? 0.78 μm ).
The resolution of the eye is also very small: the minimum size of an object discernible by the eye is about one micrometer (10-6 m). That's why we do NOT see the world as it really is, and new methods and ideas of physics, mathematics, chemistry, biology are the key to future discoveries in this area.
2. HEARING ORGANS. SOUND. RESONANCE THEORY OF HEARING
The world is filled with a wide variety of sounds. The noise of wind and waves, thunderclaps and the chirping of grasshoppers, birdsong and human voices, animal cries and the sounds of traffic - all these sounds are caught by the auricle and cause vibration of the eardrum.
The human ear consists of three parts: outer, middle and inner, the structure of each of which, in turn, represents a rather complex system. Let's try together to understand this complex process that we call “hearing.”
With the help of the auricle we determine the direction from which the sound is coming. The external auditory canal is an elongated canal, the walls of which produce a liquid substance, better known to us as sulfur. It is designed to remove foreign bodies and prevent the entry of various insects due to a specific odor. Due to the depth of the external auditory canal, the temperature and humidity at the eardrum remain almost constant, and the latter retains its mobility. At the same time, the eardrum is well protected from any damage.
The frequency range of sounds perceived by the ear is 16-20 to 20,000 Hz
Frequency range of speech 1200-9000 Hz
The frequency of sound vibrations to which the ear is most sensitive is 1500-3000 Hz
Through the system of sound ossicles of the middle ear, sounds are converted into impulses and transmitted to the receiving cells of the brain
How exactly the brain deciphers these impulses and “recognizes” sounds is still unclear to scientists.
But sounds perceived by the human ear are an important source of information and make it easier to adapt to the world around us. What sound is, how it arises, how it spreads, its parameters are studied by a special department of physics - acoustics.
Sound or a sound wave can only propagate in a material medium; it is an elastic wave that causes auditory sensations in a person. More than 20,000 thread-like receptor endings located in the inner ear convert mechanical vibrations into electrical impulses, which are transmitted along 30,000 auditory nerve fibers to the human brain and cause auditory sensations. We hear air vibrations with a frequency of 16 Hz to 20 kHz per second. 20,000 vibrations per second is the highest sound of the smallest wooden instrument in the orchestra - the flute - piccolo, and 16 vibrations corresponds to the sound of the lowest string of the largest bowed instrument - the double bass.
Vibrations of the vocal folds can create sounds ranging from 80 to 1400 Hz, although record low (44 Hz) and high (2350 Hz) frequencies have been recorded.
It has been proven that the length and tension of the vocal cords determines the pitch of a singer's voice. For men it is (18?25) mm (bass - 25 mm, tenor - 18 mm), A for women - (15?20) mm.
In a telephone, for example, the frequency range from 300 Hz to 2 kHz is used to reproduce a person’s voice. The frequency range of the main vibration modes of some instruments is shown in the figure:
The first truly scientific theory of hearing was the theory of the remarkable German naturalist, physicist and physiologist Hermann Helmholtz. It is called the resonance theory, it was confirmed by hundreds of experiments conducted by many scientists. But in recent years, with the help of an electron microscope, some inaccuracies in this theory have been discovered, in particular in the perception of high and low sounds. Helmholtz and the Italian Corti are considered pioneers in the study of hearing, although they took only the first steps. Over the past 100 years, we have come a long way towards understanding the science of hearing; now we are talking about refining it and developing it further. After all, any scientific theory must necessarily develop and bring new facts to people. Thus, the range of perception of the hearing organs is limited by the small threshold capabilities of perceiving low and high intensity sound, as well as the small frequency range of perceived sounds.
3. SENSE ORGANS OF THE SKIN
It’s amazingly nice to expose your face to the fresh wind! There are many special cells on the face and lips that sense both the coolness of the wind and its pressure. The skin is not only our protection, but also a huge source of information about the world around us, and the source is very reliable. Often we do not believe our ears and eyes, but feel the object - we want to make sure that it is there, to find out what it feels like. For all these sensations there are specialized cells, unevenly “scattered” throughout the body.
The ear perceives only sound, the eye perceives light, and the skin perceives touch and pressure, heat and cold, and finally pain. The main sense of the skin is touch, the sensation of touch. The tip of the tongue, lips and fingertips have the greatest sensitivity to pressure and touch. For example, on the skin of the fingertips, the sensation of touch occurs at a pressure of only 0.028 - 0.170 g per mm2 of skin. Not all of the skin feels touch, but only its individual points, of which there are about half a million. At each point there is a nerve ending, so even a slight pressure is transmitted to the nerve and we feel a light touch.
The organs of touch do not allow one to distinguish weak stimuli and fairly small roughnesses from each other.
The concentration of harmful liquids on the skin and the range of temperature perceived by humans is small and provides only the biological survival mode of the body.
3.1. ELECTRICAL RESISTANCE OF BODY TISSUE
The electrical resistance of individual tissue areas depends primarily on the resistance of the skin layer. Through the skin, the current passes mainly through the channels of the sweat glands and, partly, the sebaceous glands; The current strength depends on the thickness and condition of the surface layer of the skin.
Skin is the outer covering of the body. Its area is about 2 m2. The skin consists of three main layers. The outer layer - the epidermis - is formed by multilayered epithelial tissue, which is constantly exfoliated and renewed due to the proliferation of deeper cells. Beneath the epidermis layer is a layer of connective tissue called the dermis. There are numerous receptors, sebaceous and sweat glands, hair roots, blood vessels and lymphatic vessels. The deepest layer - subcutaneous tissue - is formed by adipose tissue, which serves as a “cushion” for organs, an insulating layer, and a “warehouse” for nutrients and energy.
The main function of the skin is protective, protection from mechanical influences, preventing foreign substances and pathogenic microbes from entering the body.
The electrical resistance of the human body is determined mainly by the resistance of the superficial stratum corneum of the skin - the epidermis. Thin, delicate and especially sweaty or moisturized skin, as well as skin with a damaged outer layer of the epidermis, conducts electricity well. Dry, rough skin is a very poor conductor. Depending on the condition of the skin and the current path, as well as the voltage value, the resistance of the human body ranges from 0.5-1 to 100 kOhm.
4. OLfactory Organ
How can you describe the smell of freshness, how can you explain the difference between the smell of a rose and a rotten egg? You can describe it if you compare it with another familiar smell! There are physical instruments to measure current and light intensity, but there is no measure that can be used to determine and measure the strength of an odor. Although such a device is very necessary for modern chemistry, perfumery, the food industry and many other branches of science and practice. 
We know surprisingly little about the natural organ of smell, the organ that detects odors.
There is still no theory of smell perception, and there is no law. So far there are only experiments and scientific hypotheses, although the very first step towards understanding smell was taken 2 thousand years ago. The great Lucretius Carus proposed an explanation for the sense of smell: every odorous substance emits tiny molecules of a certain shape.
5. TASTE ORGAN
Taste is a complex concept; not only the tongue senses “tasty.” The taste of aromatic melon also depends on its smell. Touch cells in the mouth provide new flavors, such as the astringent taste of unripe fruits.
Taste in the mouth is perceived by taste buds - microscopic formations in the mucous membrane of the tongue. A person has several thousand of them in his mouth. Each bulb consists of 10–15 taste cells, arranged in it like orange slices. Experimenters have learned to record the weak bioelectrical response of individual taste cells by introducing a very thin microelectrode into them. It turned out that some cells react to several tastes at once, while others react only to one.
But it is unclear how the brain sorts out all this mass of impulses that carry information about taste: bitter or sweet, bitter-salty or sweet-sour. The first classification of tastes was proposed by M.V. Lomonosov. He counted seven simple tastes, of which only four are now generally accepted: sweet, salty, sour and bitter. These are simple, most primary tastes; they have no aftertaste. Different areas of a person's tongue sense taste differently. 
At the tip of the tongue there is a cluster of “sweet” bulbs, so sweet ice cream should be tasted with the tip of the tongue. The back edge of the tongue is responsible for acidity, and the front edge is responsible for saltiness. Bitter radish is felt by the back wall of the tongue. But we feel the taste of food with our entire tongue. Along with the bitter medicine, the doctor prescribes some other medicine that takes away the unpleasant taste, because... from two tastes you can get a third, not similar to either one or the other. The most important problem in the science of taste is to find the relationship between the molecular structure of the taste cell, the physicochemical nature of the substance and the taste itself. And to the question: “What is the limitation of the range of perception of the organ of taste?” one can answer that for him the nature of sensitivity is only to a limited set of substances and chemical compounds that the human body consumes. But man is a biological being, all his senses were formed during a long evolution, so the range of their perception was sufficient for adaptation to life in earthly conditions. But the narrow range of perception of the senses, compared to the diversity of natural information signals, has always been a hindrance in the development of scientific ideas about the world around us.
But man is a biological being, all his senses were formed during a long evolution, so the range of their perception was sufficient for adaptation to life in earthly conditions. But the narrow range of perception of the senses compared to the diversity of natural information signals has always been a hindrance in the development of scientific ideas about the world around us.
6. SENSE ORGANS AND THE PROCESS OF COGNITION
A person receives a limited amount of information from each sense organ. Therefore, the process of learning about the world around us can be compared to the situation that arose in the parable of the five blind men, each of whom tried to imagine what an elephant was.
The first blind man climbed onto the elephant's back and thought it was a wall. The second, feeling the elephant’s leg, decided that it was a column. The third picked up the trunk and mistook it for a pipe. The blind man who touched the tusk thought it was a saber. And the last one, stroking the elephant’s tail, thought it was a rope.
Likewise, a lack of sensory perception leads to contradictory and ambiguous ideas about the structure of the surrounding world. Life experience turns out to be insufficient when studying phenomena determined by time intervals and spatial dimensions that are inaccessible for observation. Under such conditions, additional information is obtained by experimental installations, with the help of which it is possible to expand the range of received signals, and by paradoxical physical theories that describe the basic patterns of physical phenomena.And, despite the limited range of perception, a person tries to determine the structure of a substance and understand the nature of numerous effects beyond the range of vibrations accessible to the senses.
With the help of the olfactory organ, located in the epithelium of the upper part of the nasal cavity, a person can distinguish objects by smell, determine the quality of food and inhaled air. The taste organ makes it possible to determine the taste of food, which a person perceives with the help of special nerve endings located in special formations of the oral cavity - taste buds located on the surface of the tongue. Different parts of the tongue perceive different tastes: the tip of the tongue is sweet, the root is bitter, the sides are sour, the edges and tip are salty.
With the help of vision, a person distinguishes colors, shapes, sizes of observed objects. The eyes are located in the sockets of the skull. The movement of the eyeballs is provided by muscles attached to their outer surface. With the help of the eyelids, eyelashes and lacrimal glands, the eyes are protected from foreign small particles. The eyebrows located above the eyes protect them from sweat.
The eye has a protein shell - sclera, which determines the shape of the eyeball. The sclera passes in front into the transparent cornea. Clearly visible through the cornea Iris, which regulates the size of the pupil and determines the color of the eye. The inner layer of the eye is called the retina. It consists of photoreceptor cells that look like cones and rods. Behind the pupil there is a lens adjacent to the iris. It has the shape of a biconvex lens. The space between the cornea and the lens is filled with fluid. The eyeball itself is filled with vitreous humor - a transparent mass of jelly-like consistency. There are blood vessels and nerves leading to the eye. Light hitting the retina causes excitation in the nerve endings of the eye - receptors, through which excitation is transmitted to the brain - the cerebral cortex.
With the help of the organ of hearing, a person gains the opportunity to perceive various sounds of the surrounding world, thanks to which he can navigate the environment. The hearing organ consists of the outer, middle and inner ears.
The outer ear consists of the pinna, ear canal And eardrum. Eustachian tube and three small bones - the malleus, the incus and the stirrup - belong to the middle ear. Finally, the inner ear consists of a complex system of interconnected canals and cavities, reminiscent of a cochlea. The cochlea contains fluid and nerve endings. The auditory nerve connects the inner ear directly to the brain.
The sense of touch arises in humans thanks to the skin. The skin, especially in the fingers, palms, soles, lips, etc., contains a large number of nerve endings, which ensures their increased sensitivity. Skin sensitivity is divided into four types: pain, tactile (touch and pressure), cold and heat. Impaired skin sensitivity may be associated with a disease of the internal organs. With the help of the skin, a person is protected from mechanical influences (shocks, pressure, etc.), as well as from ultraviolet radiation.