Equipment: collapsible eye model, table " Visual analyzer", three-dimensional objects, reproductions of paintings. Handouts for desks: drawings “Structure of the eye”, cards for reinforcement on this topic.
During the classes
I. Organizational moment
II. Testing students' knowledge
1. Terms (on the board): sense organs; analyzer; structure of the analyzer; types of analyzers; receptors; nerve pathways; think tank; modality; cortical zones big brain; hallucinations; illusions.
2. Additional information on homework(student messages):
– for the first time we encounter the term “analyzer” in the works of I.M. Sechenov;
– per 1 cm of skin there are from 250 to 400 sensitive endings, on the surface of the body there are up to 8 million of them;
- on internal organs there are about 1 billion receptors;
- THEM. Sechenov and I.P. Pavlov believed that the activity of the analyzer comes down to analyzing the effects of the external and internal environment on the body.
III. learning new material
(Message of the lesson topic, goals, objectives and motivation educational activities students.)
1. The meaning of vision
What is the meaning of vision? Let's answer this question together.
Yes, indeed, the organ of vision is one of the most important sense organs. We perceive and know the world around us primarily through vision. This is how we get an idea of the shape, size of an object, its color, notice danger in time, and admire the beauty of nature.
Thanks to vision, the blue sky, young spring foliage, bright colors of flowers and butterflies fluttering above them, and golden fields open before us. Wonderful autumn colors. We can admire for a long time starry sky. The world around us is beautiful and amazing, admire this beauty and take care of it.
It is difficult to overestimate the role of vision in human life. The thousand-year experience of mankind is passed on from generation to generation through books, paintings, sculptures, architectural monuments, which we perceive with the help of sight.
So, the organ of vision is vital for us, with the help of it a person receives 95% of information.
2. Eye position
Look at the picture in the textbook and determine which bone processes are involved in the formation of the orbit. ( Frontal, zygomatic, maxillary.)
What is the role of the eye sockets?
What helps to turn the eyeball in different directions?
Experiment No. 1. The experiment is carried out by students sitting at the same desk. One needs to follow the movement of the pen at a distance of 20 cm from the eye. The second one moves the handle up and down, right and left, and describes a circle with it.
How many muscles does the eyeball move? ( At least 4, but there are 6 of them in total: four straight and two oblique. Thanks to the contraction of these muscles, the eyeball can rotate in the socket.)
3. Protective devices eyes
Experiment No. 2. Observe the blinking of your neighbor’s eyelids and answer the question: what function do the eyelids perform? ( Protection from light irritation, eye protection from foreign particles.)
Eyebrows catch sweat flowing from the forehead.
Tears have a lubricating and disinfecting effect on the eyeball. The lacrimal glands - a kind of “tear factory” - open under upper eyelid 10–12 ducts. Tear fluid is 99% water and only 1% is salt. This is a great cleaner eyeball. Another function of tears has also been established - they are removed from the body dangerous poisons(toxins) that are produced during times of stress. In 1909, Tomsk scientist P.N. Lashchenkov discovered a special substance, lysozyme, in the tear fluid, which can kill many microbes.
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4. Structure of the visual analyzer
We see only when there is light. The sequence of passage of rays through the transparent medium of the eye is as follows:
ray of light → cornea → anterior chamber of the eye → pupil → posterior chamber of the eye → lens → vitreous body → retina.
The image on the retina is reduced and inverted. However, we see objects in natural form. This is explained by a person’s life experience, as well as the interaction of signals coming from all senses.
The visual analyzer has the following structure:
1st link - receptors (rods and cones on the retina);
2nd link – optic nerve;
3rd link – brain center (occipital lobe of the cerebrum).
The eye is a self-adjusting device; it allows you to see near and distant objects. Helmholtz also believed that the model of the eye is a camera, the lens is the transparent refractive medium of the eye. The eye is connected to the brain through the optic nerve. Vision is a cortical process, and it depends on the quality of information coming from the eye to the centers of the brain.
Information from the left side of the visual fields from both eyes is transmitted to right hemisphere, and from the right side of the visual fields of both eyes to the left.
If the image from the right and left eyes falls into the corresponding brain centers, then they create a single three-dimensional image. Binocular vision - vision with two eyes - allows you to perceive three-dimensional images and helps determine the distance to an object.
Table. Structure of the eye
Components of the eye |
Structural features |
Role |
Tunica albuginea (sclera) |
Outer, dense, opaque |
Protects the internal structures of the eye, maintains its shape |
Cornea |
Thin, transparent |
Strong "lens" of the eye |
Conjunctiva |
Transparent, slimy |
Covers the front of the eyeball to the cornea and inner surface century |
Choroid |
Middle shell, black, permeated with a network blood vessels |
Nourishing the eye, light passing through it is not scattered |
Ciliary body |
Smooth muscle |
Supports the lens and changes its curvature |
Iris (iris) |
Contains melanin pigment |
Lightproof. Limits the amount of light entering the eye onto the retina. Determines eye color |
Hole in the iris surrounded by radial and circular muscles |
Regulates the amount of light entering the retina |
|
Lens |
Biconvex lens, transparent, elastic formation |
Focuses the image by changing the curvature |
Vitreous body |
Transparent jelly-like mass |
Fills in inner part eyes, supports the retina |
Front camera |
The space between the cornea and iris, filled clear liquid – aqueous humor |
|
Rear camera |
The space inside the eyeball, bounded by the iris, lens and ligament holding it, is filled with aqueous humor |
Participation in immune system eyes |
Retina (retina) |
Inner layer of the eye, a thin layer of visual receptor cells: rods (130 million) cones (7 million) |
Visual receptors form an image; cones are responsible for color production |
Cluster of cones in the central part of the retina |
Area of greatest visual acuity |
|
Blind spot |
Exit site of the optic nerve |
Location of the channel for transmitting visual information to the brain |
5. Conclusions
1. A person perceives light with the help of the organ of vision.
2. Light rays are refracted in the optical system of the eye. A reduced inverse image is formed on the retina.
3. The visual analyzer includes:
– receptors (rods and cones);
– nerve pathways (optic nerve);
– brain center (occipital zone of the cerebral cortex).
IV. Consolidation. Working with handouts
Exercise 1. Match.
1. Lens. 2. Retina. 3. Receptor. 4. Pupil. 5. Vitreous body. 6. Optic nerve. 7. Tunica albuginea and cornea. 8. Light. 9. Choroid. 10. Visual area of the cerebral cortex. 11. Yellow spot. 12. Blind spot.
A. Three parts of the visual analyzer.
B. Fills the inside of the eye.
B. Cluster of cones in the center of the retina.
D. Changes curvature.
D. Provides various visual stimulations.
E. Protective membranes of the eye.
G. Place of exit of the optic nerve.
H. Place of image formation.
I. Hole in the iris.
K. Black nourishing layer of the eyeball.
(Answer: A – 3, 6, 10; B – 5; AT 11; G – 1; D – 8; E – 7; F –12; Z – 2; I – 4; K – 9.)
Task 2. Answer the questions.
How do you understand the expression “The eye looks, but the brain sees”? ( In the eye, only receptors are excited in a certain combination, and we perceive the image when the nerve impulses reach the cerebral cortex.)
The eyes feel neither heat nor cold. Why? ( The cornea has no receptors for heat and cold.)
Two students argued: one argued that the eyes get more tired when looking at small objects located close, and the other - at distant objects. Which one is right? ( The eyes become more tired when looking at objects located close to them, since this causes the muscles that ensure the functioning (increased curvature) of the lens to become very tense. Looking at distant objects is a rest for the eyes.)
Task 3. Label the elements of the eye structure indicated by numbers.
Literature
Vadchenko N.L. Test your knowledge. Encyclopedia in 10 volumes. T. 2. – Donetsk, IKF “Stalker”, 1996.
Zverev I.D. A book for reading on human anatomy, physiology and hygiene. – M.: Education, 1983.
Kolesov D.V., Mash R.D., Belyaev I.N. Biology. Human. Textbook for 8th grade. – M.: Bustard, 2000.
Khripkova A.G. Natural science. – M.: Education, 1997.
Sonin N.I., Sapin M.R. Human biology. – M.: Bustard, 2005.
Photo from the site http://beauty.wild-mistress.ru
Question 1. What is an analyzer?
An analyzer is a system that provides perception, delivery to the brain and analysis of any type of information (visual, auditory, olfactory, etc.).
Question 2. How does the analyzer work?
Each analyzer consists of a peripheral section (receptors), a conductive section ( nerve pathways) and the central department (centers analyzing this type information).
Question 3. Name the functions of the auxiliary apparatus of the eye.
The auxiliary apparatus of the eye is the eyebrows, eyelids and eyelashes, lacrimal gland, lacrimal canaliculi, oculomotor muscles, nerves and blood vessels.
Eyebrows and eyelashes protect your eyes from dust. In addition, eyebrows drain sweat from the forehead. Everyone knows that a person blinks constantly (2-5 eyelid movements per minute). But do they know why? It turns out that at the moment of blinking, the surface of the eye is moistened with tear fluid, which protects it from drying out, while at the same time being cleansed of dust. Tear fluid is produced by the lacrimal gland. It contains 99% water and 1% salt. Up to 1 g of tear fluid is secreted per day, it collects in the inner corner of the eye, and then enters the lacrimal canaliculi, which discharge it into the nasal cavity. If a person cries, the tear fluid does not have time to escape through the canaliculi into the nasal cavity. Then tears flow through the lower eyelid and run down the face in drops.
Question 4. How does the eyeball work?
The eyeball is located in the recess of the skull - the orbit. It has a spherical shape and consists of inner core, covered with three membranes: the outer - fibrous, the middle - vascular and the inner - reticular. The fibrous membrane is divided into a posterior opaque part - tunica albuginea, or sclera, and the anterior transparent cornea. The cornea is a convex-concave lens through which light enters the eye. The choroid is located under the sclera. Its front part is called the iris, and it contains the pigment that determines the color of the eyes. In the center of the iris there is a small hole - the pupil, which reflexively, with the help of smooth muscles, can expand or contract, allowing the required amount of light into the eye.
Question 5. What functions do the pupil and lens perform?
The pupil reflexively, with the help of smooth muscles, can expand or contract, allowing the required amount of light into the eye.
Directly behind the pupil is a biconvex transparent lens. It can reflexively change its curvature, providing a clear image on the retina - the inner layer of the eye.
Question 6. Where are the rods and cones located, what are their functions?
The retina contains receptors: rods (twilight light receptors that distinguish light from dark) and cones (they have less light sensitivity, but distinguish colors). Most cones are located on the retina opposite the pupil, in the macula.
Question 7. How does the visual analyzer work?
Receptors in the retina convert light into nerve impulses, which optic nerve transmitted to the brain through the nuclei of the midbrain (superior colliculus) and diencephalon (visual nuclei of the thalamus) - to the visual zone of the cerebral cortex, located in the occipital region. The perception of color, shape, illumination of an object, and its details, which begins in the retina, ends with analysis in the visual cortex. Here all the information is collected, deciphered and summarized. As a result, an idea of the subject is formed.
Question 8: What is a blind spot?
Next to the macula is where the optic nerve exits; there are no receptors here, which is why it is called the blind spot.
Question 9. How do myopia and farsightedness occur?
People's vision changes with age, as the lens loses elasticity and the ability to change its curvature. In this case, the image of closely located objects blurs - farsightedness develops. Another vision defect is myopia, when people, on the contrary, have difficulty seeing distant objects; it develops after prolonged stress and improper lighting. With myopia, the image of an object is focused in front of the retina, and with farsightedness, it is focused behind the retina and is therefore perceived as blurry.
Question 10. What are the causes of visual impairment?
Age, prolonged eye strain, improper lighting, congenital changes eyeball,
THINK
Why do they say that the eye looks, but the brain sees?
Because the eye is optical device. And the brain processes impulses coming from the eye and converts them into an image.
Date: 04/20/2016
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- A little about the structure of the visual analyzer
- Functions of the iris and cornea
- What does the refraction of the image on the retina give?
- Auxiliary apparatus of the eyeball
- Eye muscles and eyelids
The visual analyzer is a paired organ of vision, represented by the eyeball, muscular system eyes and auxiliary apparatus. With the help of the ability to see, a person can distinguish the color, shape, size of an object, its illumination and the distance at which it is located. So human eye able to distinguish the direction of movement of objects or their immobility. A person receives 90% of information through the ability to see. The organ of vision is the most important of all the senses. The visual analyzer includes the eyeball with muscles and an auxiliary apparatus.
A little about the structure of the visual analyzer
The eyeball is located in the orbit on a fat pad, which serves as a shock absorber. With some diseases, cachexia (emaciation), the fat pad becomes thinner, the eyes sink deeper into the eye socket and it feels like they are “sunken”. The eyeball has three membranes:
- protein;
- vascular;
- mesh.
The characteristics of the visual analyzer are quite complex, so they need to be sorted out in order.
The tunica albuginea (sclera) is the outermost layer of the eyeball. The physiology of this shell is designed so that it consists of dense connective tissue, not transmitting rays of light. The muscles of the eye that provide eye movements and the conjunctiva are attached to the sclera. The front part of the sclera has a transparent structure and is called the cornea. Concentrated on the cornea great amount nerve endings that provide its high sensitivity, and there are no blood vessels in this area. It is round and somewhat convex in shape, which allows for proper refraction of light rays.
The choroid consists of a large number of blood vessels that provide trophism to the eyeball. The structure of the visual analyzer is designed in such a way that the choroid is interrupted at the place where the sclera passes into the cornea and forms a vertically located disk consisting of a plexus of blood vessels and pigment. This part of the shell is called the iris. The pigment contained in the iris is different for each person, and it provides the color of the eyes. With some diseases, the pigment may decrease or be completely absent (albinism), then the iris becomes red.
In the central part of the iris there is a hole, the diameter of which varies depending on the intensity of illumination. Rays of light penetrate the eyeball onto the retina only through the pupil. The iris has smooth muscles - circular and radial fibers. It is responsible for the diameter of the pupil. Circular fibers are responsible for the constriction of the pupil; they are innervated by the peripheral nervous system and the oculomotor nerve.
Radial muscles are classified as sympathetic nervous system. These muscles are controlled from a single brain center. Therefore, the dilation and contraction of the pupils occurs in a balanced manner, regardless of whether one eye is exposed to bright light or both.
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Functions of the iris and cornea
The iris is the diaphragm ocular apparatus. It regulates the flow of light rays onto the retina. The pupil narrows when fewer light rays reach the retina after refraction.
This happens when the light intensity increases. When lighting decreases, the pupil dilates and more light enters the fundus of the eye.
The anatomy of the visual analyzer is designed in such a way that the diameter of the pupils depends not only on lighting; this indicator is also influenced by some hormones of the body. So, for example, when frightened it is released a large number of adrenaline, which is also capable of acting on the contractility of the muscles responsible for the diameter of the pupil.
The iris and cornea are not connected: there is a space called the anterior chamber of the eyeball. The anterior chamber is filled with liquid, which performs a trophic function for the cornea and is involved in the refraction of light as light rays pass through.
The third retina is the specific perceptive apparatus of the eyeball. The retina is formed by branched nerve cells that come out of the optic nerve.
The retina is located immediately behind the choroid and lines most eyeball. The structure of the retina is very complex. Only capable of perceiving objects rear end retina, which is formed by special cells: cones and rods.
The structure of the retina is very complex. Cones are responsible for perceiving the color of objects, rods are responsible for the intensity of light. Rods and cones are interspersed, but in some areas there is a cluster of only rods, and in some there is a cluster of only cones. Light hitting the retina causes a reaction within these specific cells.
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What does the refraction of the image on the retina give?
As a result of this reaction, a nerve impulse is generated, which is transmitted along the nerve endings to the optic nerve, and then to occipital lobe cerebral cortex. It is interesting that the pathways of the visual analyzer have complete and incomplete crossovers with each other. Thus, information from the left eye enters the occipital lobe of the cerebral cortex on the right and vice versa.
An interesting fact is that the image of objects after refraction on the retina is transmitted upside down.
In this form, information enters the cerebral cortex, where it is then processed. Perceiving objects as they are is an acquired skill.
Newborn babies perceive the world upside down. As the brain grows and develops, these functions of the visual analyzer are developed and the child begins to perceive the outside world in its true form.
The refraction system is presented:
- anterior chamber;
- posterior chamber of the eye;
- lens;
- vitreous body.
The anterior chamber is located between the cornea and iris. It provides nutrition to the cornea. The posterior chamber is located between the iris and the lens. Both the anterior and posterior chambers are filled with fluid, which is able to circulate between the chambers. If this circulation is disrupted, a disease occurs that leads to vision impairment and can even lead to its loss.
The lens is a biconvex clear lens. The function of the lens is to refract light rays. If the transparency of this lens changes due to certain diseases, a disease such as cataract occurs. To date the only treatment Cataract is a replacement of the lens. This operation is simple and quite well tolerated by patients.
The vitreous fills the entire space of the eyeball, providing permanent form eyes and its trophism. The vitreous body is represented by a gelatinous transparent liquid. When passing through it, light rays are refracted.
Most people associate the concept of “vision” with eyes. In fact, the eyes are only part of a complex organ called in medicine the visual analyzer. The eyes are only a conductor of information from the outside to the nerve endings. And the very ability to see, distinguish colors, sizes, shapes, distance and movement is provided precisely by the visual analyzer - a system of complex structure that includes several departments interconnected.
Knowledge of the anatomy of the human visual analyzer allows you to correctly diagnose various diseases, determine their cause, choose the right treatment tactics, carry out complex surgical operations. Each of the departments of the visual analyzer has its own functions, but they are closely interconnected. If at least some of the functions of the organ of vision are disrupted, this invariably affects the quality of perception of reality. You can restore it only by knowing where the problem is hidden. This is why knowledge and understanding of the physiology of the human eye is so important.
Structure and departments
The structure of the visual analyzer is complex, but it is thanks to this that we can perceive the world so bright and full. It consists of the following parts:
- Peripheral department– Receptors in the retina are located here.
- The conductive part is the optic nerve.
- The central department - the center of the visual analyzer is localized in the occipital part of the human head.
The operation of a visual analyzer can essentially be compared to a television system: antenna, wires and TV
The main functions of the visual analyzer are the perception, processing and processing of visual information. The eye analyzer does not work primarily without the eyeball - this is its peripheral part, which accounts for the main visual functions.
The structure of the immediate eyeball includes 10 elements:
- sclera is the outer shell of the eyeball, relatively dense and opaque, it contains blood vessels and nerve endings, it connects in the anterior part with the cornea, and in the posterior part with the retina;
- choroid – provides a wire nutrients together with blood to the retina of the eye;
- retina - this element, consisting of photoreceptor cells, ensures the sensitivity of the eyeball to light. There are two types of photoreceptors - rods and cones. Sticks are responsible for peripheral vision, they are highly photosensitivity. Thanks to rod cells, a person is able to see at dusk. Functional feature cones are completely different. They allow the eye to perceive various colors and small details. Cones are responsible for central vision. Both types of cells produce rhodopsin, a substance that converts light energy into electrical energy. It is this that the cortical part of the brain is able to perceive and decipher;
- The cornea is the transparent part of the anterior section The eyeball is where light is refracted. The peculiarity of the cornea is that it has no blood vessels at all;
- The iris is optically the brightest part of the eyeball; the pigment responsible for the color of a person’s eyes is concentrated here. The more it is and the closer it is to the surface of the iris, the darker the eye color will be. Structurally, the iris consists of muscle fibers that are responsible for the contraction of the pupil, which in turn regulates the amount of light transmitted to the retina;
- ciliary muscle - sometimes called the ciliary girdle, main characteristic this element is the adjustment of the lens, thanks to which a person’s gaze can quickly focus on one object;
- The lens is the transparent lens of the eye, its main task is to focus on one object. The lens is elastic, this property is enhanced by the muscles surrounding it, thanks to which a person can see clearly both near and far;
- The vitreous is a clear, gel-like substance that fills the eyeball. It is this that forms its round, stable shape, and also transmits light from the lens to the retina;
- the optic nerve is the main part of the information pathway from the eyeball to the area of the cerebral cortex that processes it;
- The macula is the area of maximum visual acuity; it is located opposite the pupil above the entry point of the optic nerve. The spot got its name from great content pigment yellow color. It is noteworthy that some predator birds, distinguished by acute vision, have as many as three yellow spots on the eyeball.
The periphery collects a maximum of visual information, which is then transmitted through the conductive section of the visual analyzer to the cells of the cerebral cortex for further processing.
This is how the structure of the eyeball looks schematically in cross section
Auxiliary elements of the eyeball
The human eye is mobile, which allows it to capture a large amount of information from all directions and quickly respond to stimuli. Mobility is provided by the muscles surrounding the eyeball. There are three pairs in total:
- A pair that allows the eye to move up and down.
- A pair responsible for movement left and right.
- A pair that allows the eyeball to rotate relative to the optical axis.
This is enough for a person to look in a variety of directions without turning their head, and to quickly respond to visual stimuli. Muscle movement is ensured oculomotor nerves.
Also, auxiliary elements of the visual apparatus include:
- eyelids and eyelashes;
- conjunctiva;
- lacrimal apparatus.
Eyelids and eyelashes perform protective function, forming a physical barrier to penetration foreign bodies and substances, exposure to too bright light. The eyelids are elastic plates of connective tissue, covered on the outside with skin and on the inside with conjunctiva. The conjunctiva is the mucous membrane that lines the eye itself and the inside of the eyelid. Its function is also protective, but it is ensured by the production of a special secretion that moisturizes the eyeball and forms an invisible natural film.
Visual system human structure is complex, but quite logical, each element has a specific function and is closely connected with others
The lacrimal apparatus is the lacrimal glands, from which the lacrimal fluid is discharged into the conjunctival sac. The glands are paired, they are located in the corners of the eyes. Also in the inner corner of the eye there is a tear lake, where tears flow after they have washed the outer part of the eyeball. From there, the tear fluid passes into the nasolacrimal duct and flows into the lower sections of the nasal passages.
This is a natural and constant process, in no way felt by a person. But when too much tear fluid is produced, the nasolacrimal duct is not able to accept it and move it all at the same time. The liquid overflows over the edge of the tear pool - tears are formed. If, on the contrary, for some reason the tear fluid is produced too little or it cannot move through the tear ducts due to their blockage, dry eye occurs. A person feels severe discomfort, pain and pain in the eyes.
How does the perception and transmission of visual information occur?
To understand how the visual analyzer works, it’s worth imagining a TV and an antenna. The antenna is the eyeball. It reacts to a stimulus, perceives it, converts it into an electrical wave and transmits it to the brain. This is accomplished through the conductive section of the visual analyzer, consisting of nerve fibers. They can be compared to a television cable. The cortical department is a television; it processes the wave and deciphers it. The result is a visual image familiar to our perception.
Human vision is much more complex and more than just the eyes. This is a complex multi-stage process, carried out thanks to the well-coordinated work of the group various organs and elements
It is worth considering the wiring department in more detail. It consists of crossed nerve endings, that is, information from the right eye goes to the left hemisphere, and from the left to the right. Why is this so? Everything is simple and logical. The fact is that for optimal decoding of the signal from the eyeball to the cortex, its path should be as short as possible. The area in the right hemisphere of the brain responsible for decoding the signal is located closer to the left eye than to the right. And vice versa. This is why signals are transmitted along crossed paths.
The crossed nerves further form the so-called optic tract. Here information from different parts of the eye is transferred for decoding to different parts brain so that a clear visual picture is formed. The brain can already determine the brightness, degree of illumination, and color scheme.
What happens next? The almost completely processed visual signal enters the cortical region; all that remains is to extract information from it. This is the main function of the visual analyzer. Here are carried out:
- perception of complex visual objects, for example, printed text in a book;
- assessment of the size, shape, distance of objects;
- formation of perspective perception;
- the difference between flat and three-dimensional objects;
- combining all received information into a coherent picture.
So, thanks to the coordinated work of all departments and elements of the visual analyzer, a person is able not only to see, but also to understand what he sees. Those 90% of the information that we receive from the world around us through our eyes comes to us in exactly this multi-stage way.
How does the visual analyzer change with age?
Age characteristics The visual analyzer is not the same: in a newborn it is not yet fully formed, infants cannot focus their gaze, quickly respond to stimuli, or fully process the information received in order to perceive the color, size, shape, and distance of objects.
Newborn children perceive the world upside down and in black and white, since the formation of their visual analyzer is not yet fully completed
By the age of 1, a child’s vision becomes almost as sharp as that of an adult, which can be checked using special tables. But the complete completion of the formation of the visual analyzer occurs only at 10–11 years of age. Up to 60 years of age on average, subject to hygiene of the visual organs and prevention of pathologies, the visual apparatus works properly. Then the weakening of functions begins, which is due to natural wear and tear. muscle fibers, blood vessels and nerve endings.
We can obtain a three-dimensional image due to the fact that we have two eyes. It was already mentioned above that the right eye transmits the wave to the left hemisphere, and the left, on the contrary, to the right. Next, both waves are combined and sent to the necessary departments for decoding. At the same time, each eye sees its own “picture”, and only with the correct comparison they give a clear and bright image. If a failure occurs at any stage, a violation occurs binocular vision. A person sees two pictures at once, and they are different.
Failure at any stage of information transmission and processing in the visual analyzer leads to various violations vision
The visual analyzer is not in vain compared to a TV. The image of objects, after they undergo refraction on the retina, arrives to the brain in an inverted form. And only in the appropriate departments is it transformed into a form more convenient for human perception, that is, it returns “from head to toe.”
There is a version that newborn children see exactly this way - upside down. Unfortunately, they themselves cannot tell about this, and it is not yet possible to test the theory using special equipment. Most likely, they perceive visual stimuli in the same way as adults, but since the visual analyzer is not yet fully formed, the information received is not processed and is fully adapted for perception. The baby simply cannot cope with such volumetric loads.
Thus, the structure of the eye is complex, but thoughtful and almost perfect. First, light hits the peripheral part of the eyeball, passes through the pupil to the retina, is refracted in the lens, then converted into an electrical wave and passes along crossed nerve fibers to the cerebral cortex. Here the received information is deciphered and evaluated, and then decoded into a visual image that is understandable to our perception. It's really similar to an antenna, cable and TV. But much more filigree, more logical and amazing, because nature itself created it, and under this complex process what is actually meant is what we call vision.
The importance of vision Thanks to the eyes, you and I receive 85% of the information about the world around us; they are the same, according to calculations by I.M. Sechenov, give a person up to 1000 sensations per minute. The eye allows you to see objects, their shape, size, color, movements. The eye is able to distinguish a well-lit object with a diameter of one tenth of a millimeter at a distance of 25 centimeters. But if the object itself glows, it can be much smaller. Theoretically, a person could see a candle light at a distance of 200 km. The eye is capable of distinguishing between pure color tones and 5-10 million mixed shades. Complete adaptation of the eye to the dark takes minutes.
Diagram of the structure of the eye Fig. 1. Scheme of the structure of the eye 1 - sclera, 2 - choroid, 3 - retina, 4 - cornea, 5 - iris, 6 - ciliary muscle, 7 - lens, 8 - vitreous body, 9 - optic disc, 10 - optic nerve, 11 - yellow spot.
The ground substance of the cornea consists of transparent connective tissue stroma and corneal bodies. The cornea is covered in front stratified epithelium. The cornea (cornea) is the anterior most convex transparent part of the eyeball, one of the light-refracting media of the eye.
The iris (iris) is the thin, movable diaphragm of the eye with a hole (pupil) in the center; located behind the cornea, in front of the lens. The iris contains varying amounts of pigment, which determines its color “eye color”. The pupil is a round hole through which light rays penetrate inside and reach the retina (the size of the pupil changes [depending on the intensity of the light flux: in bright light it is narrower, in weak light and in the dark it is wider].
Lens transparent body located inside the eyeball opposite the pupil; Being a biological lens, the lens is an important part of the light-refracting apparatus of the eye. The lens is a transparent biconvex round elastic formation,
Photoreceptors signs rods cones Length 0.06 mm 0.035 mm Diameter 0.002 mm 0.006 mm Number 125 – 130 million 6 – 7 million Image Black and white Colored Substance Rhodopsin (visual purple) iodopsin location Predominant in the periphery Predominant in the central part of the retina Macula – a cluster of cones, the blind spot – the exit point of the optic nerve (no receptors)
Structure of the retina: Anatomically, the retina is a thin membrane adjacent along its entire length to inside To vitreous body, and from the outside to choroid eyeball. There are two parts in it: the visual part (the receptive field - the area with photoreceptor cells (rods or cones) and the blind part (the area on the retina that is not sensitive to light). Light falls from the left and passes through all the layers, reaching the photoreceptors (cones and rods) Which transmit the signal along the optic nerve to the brain.
Myopia Myopia (myopia) is a vision defect (refractive error) in which the image falls not on the retina, but in front of it. The most common cause is an enlarged (relative to normal) eyeball in length. A rarer option is when the refractive system of the eye focuses the rays more strongly than necessary (and, as a result, they again converge not on the retina, but in front of it). In any of the options, when viewing distant objects, a fuzzy, blurry image appears on the retina. Myopia most often develops during school years, as well as during studies in secondary and higher education. educational institutions and is associated with prolonged visual work at close range (reading, writing, drawing), especially in poor lighting and poor hygienic conditions. With the introduction of computer science in schools and the spread of personal computers, the situation has become even more serious.
Farsightedness (hyperopia) is a feature of the refraction of the eye, consisting in the fact that images of distant objects at rest of accommodation are focused behind the retina. IN at a young age if farsightedness is not too high, using the accommodation voltage, you can focus the image on the retina. One of the causes of farsightedness may be a reduced size of the eyeball on the anterior-posterior axis. Almost all babies are farsighted. But with age, in most people this defect disappears due to the growth of the eyeball. The cause of age-related (senile) farsightedness (presbyopia) is a decrease in the ability of the lens to change curvature. This process begins at about 25 years of age, but only by 4050 years of age leads to a decrease in visual acuity when reading at the usual distance from the eyes (2530 cm). Colorblindness Up to 14 months in newborn girls and up to 16 months in boys, there is a period of complete color blindness. The formation of color perception ends by the age of 7.5 years in girls and by 8 years in boys. About 10% of men and less than 1% of women have a color vision defect (blindness between red and green or, less commonly, blue; there may be complete color blindness)
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