VISUAL
ANALYZER
The visual analyzer includes:
peripheral
Department:
retinal receptors
eyes
central
Department:
conductive
Department:
optic nerve;
occipital cortex
cerebral hemispheres
Function visual analyzer:
◦ perception, conduction and decoding of visual signals.
Structure of the eye
◦ The eye consists of:eyeball
auxiliary apparatus
eyebrows - protection from sweat;
eyelashes - protection from dust;
eyelids - mechanical protection and maintenance
humidity;
lacrimal glands - located at the top
outer edge of the orbit. She produces tears
liquid that moisturizes, rinses and
eye disinfectant. Excess tear fluid
fluid is removed into the nasal cavity
through tear duct, located in
inner corner of the eye socket.
EYEBALL
The eyeball is roughly spherical in shape with a diameter of about 2.5 cm.It is located on the fat pad in the anterior part of the orbit.
The eye has three membranes:
1) tunica albuginea
(sclera) with transparent
cornea
- very outdoor
dense fibrous
membrane of the eye;
2) choroid
with outer rainbow
membrane and ciliary
body
3) mesh
shell (retina) -
inner lining of the eye
apple
- permeated
blood vessels
(eye nutrition) and
contains pigment
obstructive
light scattering through
sclera;
- receptor part
visual analyzer;
function: direct
light perception and transmission
information to the central
nervous system.
Internal structure
Conjunctiva -mucous membrane,
connecting the eye
apple with skin
covers.
tunica albuginea
(sclera) -
outer durable shell
eyes; inner part
sclera is impermeable to
light rays.
Function: eye protection from
external influences and
light insulation; Cornea - anterior
Iris -
transparent part
sclera; is the first
lens in the path of light rays.
Function: mechanical protection
eyes and transmission of light
rays.
anterior pigmented part
choroid; contains
pigments melanin and lipofuscin,
determining eye color.
Choroid -
middle layer of the eye, rich
vessels and pigment.
The lens is a biconvex lens located behind
cornea. Lens function: focusing light
rays. The lens has no blood vessels or nerves. It does not develop
inflammatory processes. It contains a lot of proteins, which sometimes
may lose their transparency, which leads to disease,
called cataracts. The pupil is a round hole in
iris.
Function: light regulation
flow entering the eye.
Pupil diameter involuntarily
changes with the help of smooth muscles
iris when changing
illumination
Ciliary (ciliary) body
- part of the middle (vascular)
membranes of the eye;
function:
fixation of the lens,
ensuring the process
accommodation (change in curvature)
lens;
production of watery
moisture chambers of the eye
thermoregulation.
Front and rear cameras -
space in front and behind the rainbow
shell filled with transparent
liquid (aqueous humor). Retina
(retina) -
receptor
eye apparatus.
Vitreous body - eye cavity
between the lens and the fundus of the eye,
filled with a transparent viscous gel,
maintaining the shape of the eye.
STRUCTURE OF THE RETINA
◦ The retina is formedbranching endings
optic nerve, which
approaching the eyeball,
passes through the albuginea
shell, and shell
the nerve merges with the protein
shell of the eye. Inside the eye
nerve fibers are distributed
in the form of a thin mesh
shell that lines
rear 2/3 internal
surface of the eyeball.
The retina consists of supporting cells that form a network structure, from where
where its name came from. Only its back part perceives light rays. Mesh
the shell in its development and function is a part nervous system. All
the remaining parts of the eyeball play a supporting role for perception
retina of visual stimulation. The retina is a part of the brain
pushed outward, closer to the surface of the body, and
maintaining a connection with him through a couple
optic nerves.
Nerve cells form in the retina
circuits consisting of three neurons
First
amacrine
neurons have
dendrites in
in the form of sticks and
cones; these
neurons
are
final
cells
visual
nerve, they
perceive
visual
irritation and
present
are light
receptors.
second -
bipolar
e neurons;
third -
multipole
ry
neurons
(ganglinarn
y); from them
retreat
axons,
which
stretch along
bottom of the eye and
form
visual
nerve. Photosensitive
retina:
sticks -
perceive
brightness;
elements
cones -
perceive
color. Sticks
Cones
Sticks contain
substance rhodopsin
, thanks to
which sticks
very excited
fast weak
twilight light,
but they can't
perceive color.
In education
rhodopsin
vitamin involved
A.
◦ Cones slowly
get excited and just
bright light. They
able
perceive color. IN
the retina contains three
type of cones. First
perceive red
color, second -
green, third -
blue. Depending
from degree
excitation of cones
and combinations
irritations, eyes
perceives
various colors and
shades.
In case of its deficiency
develops
"night blindness" Sticks
Cones
Low light in progress
visions involve only sticks
(twilight vision), and the eye does not
distinguishes colors, vision turns out to be
achromatic (colorless).
In the area of the macula on the retina there is no
rods - only cones, here the eye
has the greatest visual acuity and
best color perception. That's why
the eyeball is in continuous
movement, so that the part in question
object was located on the yellow spot. By
as you move away from the macula, density
sticks increases, but then
decreases.
Muscles of the eye
Muscles of the eyepupil muscles
lens muscles
oculomotor
s muscles
- three pairs
striated
skeletal muscles,
which are attached
to the conjunctiva;
carry out movement
eyeball;
Oculomotor muscles Pupil muscles - smooth muscles of the iris (circular and radial), changing the diameter of the pupil;
The orbicularis muscle (contractor) of the pupil is innervated by parasympathetic fibers from
oculomotor nerve
The radial muscle (dilator) of the pupil is fibers of the sympathetic nerve.
The iris thus regulates the amount of light entering the eye; with strong
In bright light, the pupil narrows and limits the flow of rays, and in weak light it expands, giving
the ability to penetrate more rays. The diameter of the pupil is influenced by the hormone adrenaline.
When a person is in an excited state (fear, anger, etc.), the amount of adrenaline in
blood increases, and this causes the pupil to dilate.
The movements of the muscles of both pupils are controlled from one center and occur synchronously. Therefore both
The pupils always dilate or contract equally. Even if you apply bright light to one
only the eye, the pupil of the other eye also narrows. muscles of the lens (ciliary
muscles) - smooth muscles that change curvature
lens (accommodation -- focusing
retinal images).
Wiring department
◦ The optic nerve isconductor of light irritations from
eyes to the visual center and
contains sensitive fibers.
Moving away from the posterior pole of the eyeball,
The optic nerve leaves the orbit and enters the
cranial cavity, through the optic canal, along with
with the same nerve of the other side, forms a cross
(chiasma) under the hypolalamus. After the cross
the optic nerves continue into the optic
tracts The optic nerve is connected to the nuclei
diencephalon, and through them - with the cortex
hemispheres.
Central department
◦ Impulses from light stimulation byoptic nerve pass to the cerebral cortex
occipital lobe, where the visual optic is located
center.
◦ The fibers of each nerve are connected to two
hemispheres of the brain, and the image,
received on the left half of the retina of each
eyes, analyzed in the visual cortex
left hemisphere, and on the right half of the retina
- in the cortex of the right hemisphere.
Central division of the visual
analyzer is located in the occipital lobe
cerebral cortex. Passage sequence
rays through transparent
the environment of the eye is: ray of light →
cornea → anterior chamber of the eye →
pupil → posterior chamber of the eye →
lens → vitreous body →
retina.
Visual impairment
With age and under
influence of others
reasons ability
control curvature
surfaces
lens
weakens.
Myopia (myopia) - focusing the image
in front of the retina; develops due to an increase
curvature of the lens, which can occur with
abnormal metabolism or disorder
visual hygiene. Corrected by glasses with concave
lenses.
Farsightedness - focusing the image behind
retina; occurs due to a decrease
convexity of the lens. Corrected with glasses
convex lenses.
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 main substance of the cornea consists of a transparent connective tissue stroma and corneal bodies. In front, the cornea is covered with multilayered 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].
The lens is a 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 the 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. More rare option- 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 in school years, as well as while studying in secondary and higher 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. At a young age, if farsightedness is not too high, using 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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Slide captions:
Structure and functions of the membranes of the eye. Visual hygiene.
There should be a reflection of happiness in the eyes of beautiful and big ones” (G. Alexandrov) “I believe! These eyes don't lie. After all, how many times have I told you that your main mistake is that you underestimate the value of human eyes. Understand that the tongue can hide the truth, but the eyes can never! You are asked a sudden question, you don’t even flinch, in one second you control yourself and know what needs to be said to hide the truth, and you speak very convincingly, and not a single wrinkle on your face moves, but, alas, alarmed by the question oh the truth from the bottom of the soul jumps into the eyes for a moment, and it’s all over. She's been spotted and you've been caught! (Film “The Master and Margarita”) “But by the eyes - you can’t confuse them both up close and from afar. Oh, the eyes are a significant thing. Like a barometer. You can see everything - who has great dryness in their soul, who about what he can poke in the ribs with the toe of his boot, and who himself is afraid of everyone "(Mikhail Afanasyevich Bulgakov. Heart of a Dog). "The eyes are the mirror of the soul" (V. Hugo)
“A wonderful world, full of colors, sounds and smells, is given to us by our senses” (M.A. OSTROVSKY)
Her eyes are like two fogs, Half a smile, half a cry, Her eyes are like two deceptions, Covered in the mist of failure. A combination of two mysteries. Half delight, half fear, a fit of mad tenderness, anticipation of mortal torment. When darkness comes and a thunderstorm approaches, Her beautiful eyes flicker from the bottom of my soul. Nikolay Zabolotsky
How many sense organs does a person have? - Five: vision, smell, hearing, taste, touch. It turns out that we also have a sixth sense - a sense of balance.
Human sense organs.
Brain centers that control the functioning of the senses.
What are analyzers? Physical, chemical Physiological Mental process. process process. Sensation irritation excitation pathways Stimuli Sensory organ (receptors) Center in the cerebral cortex
Analyzers – physiological systems, providing perception, carrying out and analysis of information from the internal and external environment and forming specific sensations. Sensation is a direct reflection of the properties of objects and phenomena outside world And internal environment, affecting the senses. An analyzer is a system consisting of receptors.
Receptors are specialized nerve endings that convert stimuli into nervous excitement. Information is information about objects and phenomena environment. Illusions are distorted, erroneous perceptions. Aesthesiology is a branch of anatomy that studies the structure of the sense organs.
Visual analyzer
* The eye is the peripheral part of the visual analyzer. * The eye is often compared to a camera, which contains a casing (cornea), lens (lens), diaphragm (iris) and light-sensitive film (retina). It would be more appropriate to compare the human eye with an analogue of a complex computer cable device, since we look with our eyes and see with our brains. * The eye has an irregular spherical shape, approximately 2.5 cm in diameter.
* Two eyeballs are securely hidden in the sockets of the skull. The organ of vision consists of the auxiliary apparatus of the eye, which includes the eyelids, conjunctiva, lacrimal organs, oculomotor muscles and fascia of the orbit, and the optical apparatus - the cornea, aqueous humor of the anterior and rear cameras eyes, lens and vitreous body. * The retina, optic nerve and visual pathways transmit information to the brain, where the resulting image is analyzed. * The lens has amazing property– accommodation. * Accommodation is the ability of the eye to clearly see objects at different distances due to changes in the curvature of the lens.
External structure of the organ of vision The eye is covered in front by the upper and lower eyelids. The outside of the eyelids is covered with skin, and the inside with a thin membrane - the conjunctiva. In the thickness of the eyelids in the upper part of the orbit there are lacrimal glands. The fluid they produce enters the nasal cavity through the lacrimal canaliculi and lacrimal sac. It also moisturizes the mucous membrane of the eye, so the surface of the eyeball is always moist. The eyelids glide freely over the mucous membrane, protecting the eye from adverse environmental factors. Under the skin of the eyelids are located the muscles of the eye: the orbicularis muscle and the levator muscle. upper eyelid. With the help of these muscles, the palpebral fissure opens and closes. Eyelashes grow along the edges of the eyelids, performing protective function. The eyeball moves with the help of six muscles. They all work in concert, so eye movement - moving and turning in different directions - occurs freely and painlessly.
Sclera, cornea, iris Internal structure organ of vision. The eyeball consists of three membranes: outer, middle and inner. Outer shell The eye consists of the sclera and cornea. The sclera (white of the eye) - the durable outer capsule of the eyeball - acts as a casing. The cornea is the most convex part of the anterior part of the eye. It is a transparent, smooth, shiny, spherical, sensitive shell. The cornea is, figuratively speaking, a lens, a window to the world. The middle layer of the eye consists of the iris, ciliary body and choroid. These three sections make up the vascular tract of the eye, which is located under the sclera and cornea. The iris (anterior section of the vascular tract) - acts as the diaphragm of the eye and is located behind the transparent cornea. It is a thin film painted in a certain color (gray, blue, brown, green) depending on the pigment (melanin) that determines the color of the eyes. People living in the North and South usually have different colour eye. Northerners mostly have blue eyes, southerners have brown eyes. This is explained by the fact that during the process of evolution, people living in the Southern Hemisphere produce more dark pigment in the iris, as it protects the eyes from the adverse effects of the ultraviolet part of the spectrum of sunlight.
Pupil, lens, vitreous body Internal structure of the organ of vision. In the center of the iris there is a black round hole - the pupil. Rays passing through it and the optical system of the eye reach the retina. The pupil uses muscles to regulate the amount of light entering, which contributes to the clarity of the image. The diameter of the pupil can vary from 2 to 8 mm depending on the lighting and the state of the central nervous system. In bright light the pupil constricts, and in dim light it dilates. Along the periphery, the iris passes into ciliary body, in the thickness of which there is a muscle that changes the curvature of the lens and serves for accommodation. In the area of the pupil there is a lens, a “living” biconvex lens, which is also actively involved in the accommodation of the eye. Between the cornea and the iris, the iris and the lens, there are spaces - chambers of the eye, filled with a transparent, light-refracting liquid - aqueous humor, which nourishes the cornea and lens. Behind the lens is a transparent vitreous body, which belongs to the optical system of the eye and is a jelly-like mass.
Retina The internal structure of the organ of vision. Light entering the eyes is refracted and projected onto the back surface of the eye, which is called the retina. The retina (photosensitive film) is a very thin, delicate and extremely complex nerve formation in structure and function. Figuratively speaking, the retina - a kind of window into the brain - is the inner shell of the eyeball. The retina is transparent. It occupies an area equal to approximately 2/3 of the choroid. The photoreceptor layer, which includes rods and cones, is the most important cell layer in the retina. The retina is heterogeneous. Its central part is the macula, which contains only cones. The macula has yellow due to the yellow pigment content and is therefore called a macula macula. Rods are most common on the peripheral parts. Closer to the yellow spot, in addition to the rods, there are cones. The closer to the macula macula, the more cones become, and in macula there are only cones. In the center of the visual field, we see with the help of cones, this part of the retina is responsible for distance visual acuity, and in the periphery, rods are involved in the perception of light. The human retina is arranged in an unusual way - it seems to be upside down. One of possible reasons This is the location behind the receptors of a layer of cells containing the black pigment melanin. Melanin absorbs light passing through the retina, preventing it from being reflected back and scattered inside the eye. Essentially, it plays the role of black paint inside the camera, which is the eye.
The human eye contains two types of light-sensitive cells (receptors): highly sensitive rods, responsible for twilight (night) vision, and less sensitive cones, responsible for color vision. In the human retina there are three types of cones, the maximum sensitivity of which falls on the red, green and blue part of the spectrum, that is, corresponds to the three “primary” colors. They provide recognition of thousands of colors and shades.
Visual analyzer Perception of visual sensations The visual analyzer is a set of nerve formations that provide the perception of the size, shape, color of objects, their relative position. In the visual analyzer: - peripheral section make up photoreceptors (rods and cones); - conduction section - optic nerves; - central section - visual cortex of the occipital lobe. The visual analyzer is represented by the perceptive department - the receptors of the retina of the eye, the optic nerves, the conduction system and the corresponding areas of the cortex in the occipital lobes of the brain.
Visual hygiene. Our eyes provide a unique opportunity to perceive the world around us. But they are vulnerable and tender, so we must take care of them. There are rules that, if followed, help maintain eye health for a long time. It is necessary to read in sufficient, good lighting. The eyes should not be overstrained. Lighting is considered good if: - the lamp is located above and behind - the light should fall from behind the shoulder; - when the light is directed directly into the face, you cannot read; - the brightness of the lighting should be sufficient; if it is twilight around and the letters are difficult to distinguish, it is better to put the book aside; - the desktop in daylight should be positioned so that the window is on the left; - table lamp in evening time should be on the left; - the lamp must be covered with a lampshade so that the light does not fall directly into the eyes. You should not read in transport when it is moving. After all, due to constant shocks, the book approaches, moves away, and deviates to the side. Our eyes probably don’t like this kind of “training.”
Do not hold the book closer than 30 cm from your eyes. If you look at objects too close, the eye muscles become overstrained, quickly causing fatigue. When going to the beach or for a walk in the bright sun, do not forget to wear Sunglasses. After all, your eyes can also get sunburned. With such a burn, the conjunctiva of the eye swells and turns red, the eyes itch and hurt, vision deteriorates - objects around seem blurry. If the sunlight is not bright, you can take off your glasses. Watching TV for a long time or working at a computer for a long time also negatively affects our eyes. It is better to sit further away from the TV, at least two meters away. But the distance to the monitor should be no less than the length of an outstretched arm. When working at a computer, it is very useful to take breaks every 40-45 minutes and... blink! Yes, exactly blink. Because it - natural way clean and lubricate the surface of the eye. To good vision has not left you for many years, you need to eat right. Vitamins A and D are especially beneficial for the eyes. Vitamin A is found in foods such as cod liver, egg yolks, butter, and cream. In addition, there are foods rich in provitamin A, from which the vitamin itself is synthesized in the human body. Provitamin A is found in carrots, green onions, sea buckthorn, sweet peppers, and rose hips. Vitamin D is found in pork and beef liver, herring, butter.
Eye diseases There is an old Turkmen proverb: “A person does not die from eye diseases, but no one will come to inquire about his health.” We are taught to take care of our eyes from childhood, but in the fast pace of life we forget about the good advice of parents, teachers and doctors, and, unfortunately, we do not have a clear idea of how to preserve our vision for many years. This is due to the characteristics of our upbringing, living conditions, family traditions, etc. Blepharitis is inflammation of the edges of the eyelids. Abscess of the century - purulent inflammation century Allergic conditions. In this case, there is itching in the eye area, swelling of the soft tissues, and there may be redness and lacrimation.
Eye diseases Cataract. This is a disease of the lens. It is mainly found in old age and is associated with clouding of the lens, the cause of which is a violation of its structure. Color blindness (color blindness). This disease causes an inability to distinguish certain colors. Twitching of the eyelid. This is one of the types nervous tic. It can be associated with stress, lack of sleep, etc. Farsightedness or hypermetropia is especially common in older people. With it, light rays are focused as if behind the retina. Surrounding objects appear blurry and lack contrast. Myopia or myopia can be congenital or acquired. With it, light rays are focused in front of the retina. Good visual acuity is only possible at close range, and distant objects are seen blurred.
Run the test. 1. Match the sense organs and the stimuli that they perceive: Sense organ Stimulus: 1. Organ of vision A. Red traffic light. 2. Organ of hearing B. Smooth silk 3. Organ of taste B. Bitter medicine 4. Organ of smell D. Fire siren 5. Organ of touch E. Perfume 2. Arrange the parts of the analyzer in order. a) associative zone of the cerebral cortex, b) receptors, c) pathways 3. Match the analyzers with their representations in the brain: 1) occipital zone; A) Hearing analyzer: 2) parietal zone; b) Visual analyzer; c) Taste analyzer Conduct a self-test and evaluate your work according to following criteria: “3 points” – completed all tasks correctly. “2 points” – completed 2 tasks correctly. “1 point” – completed 1 task correctly
Run the test. 1.Which of the following is included in the composition of the eyeball? A) External rectus muscle of the eyeball B) Ciliary muscle C) upper and lower eyelids. 2. What are the cone cells in the retina responsible for? A) Twilight and daylight vision B) Twilight and color vision C) Daytime and color vision 3. What is myopia? A) Myopia; B) Farsightedness; B) Astigmatism 4. The “blind spot” is: A) the place where the cones are concentrated; B) the internal space of the eyeball; C) the place where the optic nerve exits. 5. When reading a book in the evening, the light should: A) be directed directly at the face; B) fall from the left; C) is not needed at all.
Crossword 1. A small hole in the center of the iris, which can reflexively expand or contract with the help of muscles, allowing the required amount of light into the eye. 2. A biconvex transparent formation located behind the pupil. 3. Convex-concave lens through which light penetrates into the eye 4. Inner membrane of the eye. 5. Processes nerve cells or specialized nerve cells that respond to specific stimuli. 6. Twilight light receptors. 7. Visual impairment, in which the lens loses its elasticity and nearby objects become blurred. 8. Depression in the skull. 9. An auxiliary device that protects the eye from dust. 10. Organ of vision. 11. Transparent and colorless body, filling the inside of the eye. 12. The middle part of the choroid, which contains the pigment that determines the color of the eyes. 13. The exit point of the optic nerve, where there are no receptors. 14. One of the auxiliary apparatus. 15. Outer shell. 16. Protein shell. 17. Visual impairment, when the image of an object is focused in front of the retina and is therefore perceived as blurry. 18. Receptors capable of responding to colors. 19. Protective formations from sweat flowing from the forehead. 20. A complex system, providing analysis of irritation and monitoring motor and labor activity of a person.
Resources used. Eyesurgery.surgery.su / eyediseases / cureplant.ru/index.php/ bolezni-glaz travinko.ru/ stati / bolezni-glaz le-cristal.ru/ gigiena-zreniya /
Slide 2
Structure and functions of the eye
A person sees not with his eyes, but through the eyes, from where information is transmitted through the optic nerve, chiasm, visual tracts to certain areas occipital lobes the cerebral cortex, where the picture of the external world that we see is formed. All these organs make up our visual analyzer or visual system. Having two eyes allows us to make our vision stereoscopic (that is, form a three-dimensional image). The right side of the retina of each eye transmits through the optic nerve " right side» images to the right side of the brain, works similarly left-hand side retina. Then the brain connects two parts of the image - right and left - together. Since each eye perceives “its own” picture, if the joint movement of the right and left eyes is disrupted, binocular vision may be disrupted. Simply put, you will begin to see double or see two completely different pictures at the same time.
Slide 3
Slide 4
Functions of the eye
optical system that projects the image; a system that perceives and “encodes” the received information for the brain; "serving" life support system.
Slide 5
The structure of the eye The eye can be called a complex optical device. Its main task is to “transmit” the correct image to the optic nerve. The cornea is the transparent membrane that covers the front of the eye. It lacks blood vessels and has great refractive power. Part of the optical system of the eye. The cornea borders the opaque outer layer of the eye - the sclera. The anterior chamber of the eye is the space between the cornea and the iris. It is filled with intraocular fluid. The iris is shaped like a circle with a hole inside (the pupil). The iris consists of muscles that, when contracted and relaxed, change the size of the pupil. It enters the choroid of the eye. The iris is responsible for the color of the eyes (if it is blue, it means there are few pigment cells in it, if it is brown, it means a lot). Performs the same function as the aperture in a camera, regulating the light flow. The pupil is a hole in the iris. Its size usually depends on the light level. The more light, the smaller the pupil. The lens is the “natural lens” of the eye. It is transparent, elastic - it can change its shape, almost instantly “focusing”, due to which a person sees well both near and far. Located in the capsule, held in place by the ciliary band. The lens, like the cornea, is part of the optical system of the eye. The vitreous is a gel-like transparent substance located in the back of the eye. The vitreous body maintains the shape of the eyeball and is involved in intraocular metabolism. Part of the optical system of the eye. Retina - consists of photoreceptors (they are sensitive to light) and nerve cells. Receptor cells located in the retina are divided into two types: cones and rods. In these cells, which produce the enzyme rhodopsin, the energy of light (photons) is converted into electrical energy of the nervous tissue, i.e. photochemical reaction.
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The rods are highly photosensitivity and allow you to see in poor lighting; they are also responsible for peripheral vision. Cones, on the contrary, require more light for their work, but they allow you to see small details (responsible for central vision) and make it possible to distinguish colors. The largest concentration of cones is located in the central fossa (macula), which is responsible for the highest visual acuity. The retina is adjacent to the choroid, but in many areas it is loose. This is where it tends to flake off when various diseases retina. The sclera is the opaque outer layer of the eyeball that merges at the front of the eyeball into the transparent cornea. 6 are attached to the sclera oculomotor muscles. It contains a small number of nerve endings and blood vessels.
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Structure of the eye
The choroid - lines the posterior part of the sclera; the retina is adjacent to it, with which it is closely connected. The choroid is responsible for the blood supply to intraocular structures. In diseases of the retina, it is very often involved in pathological process. There are no nerve endings in the choroid, so when it is diseased, there is no pain, which usually signals some kind of problem. Optic nerve - with the help of the optic nerve, signals from nerve endings are transmitted to the brain.
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Visual analyzer and its parts
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 the human eye is 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. The human eye is capable of distinguishing small objects and the slightest shades, while seeing not only during the day, but also at night. Experts say that with the help of vision we learn from 70 to 90 percent of all information. Many works of art would not be possible without eyes.
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Components of vision and their functions
Let's start by considering the structure of the visual analyzer, consisting of: the eyeball; conducting pathways - through them the picture recorded by the eye is fed to the subcortical centers, and then to the cerebral cortex. Therefore, in general, three sections of the visual analyzer are distinguished: peripheral – eyes; conduction – optic nerve; central – visual and subcortical zones of the cerebral cortex. The visual analyzer is also called the visual secretory system. The eye includes the orbit as well as the ancillary apparatus. The central part is located mainly in the occipital part of the cerebral cortex. The accessory apparatus of the eye is a system of protection and movement. In the latter case, the inside of the eyelids has a mucous membrane called the conjunctiva. Defense system includes lower and upper eyelid with eyelashes. The sweat from the head goes down, but does not get into the eyes due to the existence of the eyebrows. Tears contain lysozyme, which kills harmful microorganisms that enter the eyes. Blinking the eyelids helps to regularly moisten the apple, after which the tears descend closer to the nose, where they enter the lacrimal sac. Then they move into the nasal cavity.
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Outdoor
The outer shell contains the cornea and sclera. The first one doesn't blood vessels, however, it has many nerve endings. Nutrition is provided by intercellular fluid. The cornea allows light to pass through and also has a protective function, preventing damage to the inside of the eye. It has nerve endings: when even a little dust gets on it, cutting pain appears. The sclera is either white or bluish in color. The oculomotor muscles are attached to it.
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Average
The tunica media can be divided into three parts: the choroid, located under the sclera, has many vessels and supplies blood to the retina; the ciliary body is in contact with the lens; iris - the pupil reacts to the intensity of light that hits the retina (dilates in low light, contracts in strong light).
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Internal
The retina is a brain tissue that allows the function of vision to be realized. It looks like a thin membrane adjacent over the entire surface to the choroid. The eye has two chambers filled with transparent liquid: the anterior one; rear As a result, we can identify factors that ensure the performance of all functions of the visual analyzer: a sufficient amount of light; focusing the image on the retina; accommodation reflex.
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Binocular vision
To get one picture formed by two eyes, the picture is focused at one point. Such lines of vision diverge when looking at distant objects, and converge when looking at close ones. Thanks to binocular vision, you can determine the location of objects in space in relation to each other, evaluate their distance, etc.
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Rods and cones of the retina
Rods and cones are sensitive receptors in the retina of the eye that transform light stimulation into nervous stimulation, i.e. they convert light into electrical impulses that travel along the optic nerve to the brain. Rods are responsible for perception in low light conditions (responsible for night vision), cones - for visual acuity and color perception (day vision). Let's consider each type of photoreceptor separately.
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Retinal rods
The sticks have the shape of a cylinder with an uneven, but approximately equal diameter of the circumference along the length. In addition, the length (equal to 0.000006 m or 0.06 mm) is 30 times greater than their diameter (0.000002 m or 0.002 mm), which is why the elongated cylinder really looks very much like a stick. There are about 115-120 million rods in the eye of a healthy person. The human eye rod consists of 4 segments: 1 - Outer segment (contains membrane disks), 2 - Connecting segment (cilium), 3 - Inner segment (contains mitochondria), 4 - Basal segment (nerve junction)
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Cones of the retina
Cones get their name due to their shape, similar to laboratory flasks. The length of a cone is 0.00005 meters, or 0.05 mm. Its diameter at its narrowest point is about 0.000001 meters, or 0.001 mm, and 0.004 mm at its widest. There are about 7 million cones in the retina of a healthy adult. Cones are less sensitive to light; in other words, to excite them, a light flux that is tens of times more intense will be required than to excite rods. However, cones are able to process light more intensely than rods, which is why they better perceive changes in light flux (for example, they are better than rods at distinguishing light in dynamics when objects move relative to the eye), and also determine a clearer image. The cone of the human eye consists of 4 segments: 1 - Outer segment (contains membrane disks with iodopsin), 2 - Connecting segment (constriction), 3 - Inner segment (contains mitochondria), 4 - Synaptic connection region (basal segment).
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Optical system of the eye
Optical system- a set of optical elements (refractive, reflective, diffraction, etc.) created to transform light beams (in geometric optics), radio waves (in radio optics), charged particles (in electronic and ion optics) Optical diagram - a graphical representation of the change process light in an optical system. An optical instrument (English: optical instrument) is an optical system structurally designed to perform a specific task, consisting of at least one of the basic optical elements. An optical device may include light sources and radiation receivers. In another formulation, a device is called optical if at least one of its main functions is performed by an optical system.
Slide 20
The optical system of the eye can be considered as a system of lenses formed by various transparent tissues and fibers. The difference in the "material" of these natural lenses causes a difference in their optical characteristics and primarily in the refractive index. The optical system of the eye creates a real image of the observed object on the retina. Form normal eye close to the sphere. For an adult, the diameter of the eyeball sphere is approximately 25 mm. Its mass is about 78 g. With ametropia, the spherical shape is usually disrupted. The anteroposterior dimension of the axis, also called sagittal, with myopia usually exceeds the vertical and horizontal (or transverse). In this case, the eye no longer has a spherical, but an elliptical shape. With hypermetropia, on the contrary, the eye is usually somewhat flattened in longitudinal direction The sagittal size is smaller than the vertical and transverse ones.
Slide 21
Intravital measurement of the anteroposterior axis of the eye does not currently cause difficulties. For this, echobiometry is used (a method based on the use of ultrasound) or x-ray method. Determining this value is important for solving a number of diagnostic problems. It is also necessary to determine the true scale of the image of fundus elements.
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Visual acuity
Visual acuity is the ability of the eye to distinguish two points separately when minimum distance between them. A measure of visual acuity is the angle formed by the rays coming to the eye from these points. The smaller this angle, the higher the visual acuity. The visual acuity of the eye with the smallest visual angle, equal to 1 minute, is taken as one. The highest visual acuity is provided only by the area of the macula of the retina, and on both sides of it it quickly decreases and already at an angular distance of about 10° it is approximately 5 times less. Seeing with one eye makes it difficult to judge the depth of space. Combined vision with two eyes provides a clear three-dimensional perception of the object in question and allows you to correctly determine its location in space. With one eye, without turning the head, a person can cover about 150o of space, with two eyes - about 180o.
Slide 23
Doltonism
Doltonism, color blindness, is a hereditary, less commonly acquired feature of vision in humans and primates, expressed in the inability to distinguish between green and red colors to a greater extent. Named after John Dalton, who first described one of the species color blindness based on his own feelings in 1794. The inheritance of color blindness is associated with the X chromosome and is almost always transmitted from a mother who carries the gene to her son, as a result of which it is twenty times more likely to occur in men who have a set of XY sex chromosomes. In men, the defect in the only X chromosome is not compensated for, since there is no “spare” X chromosome. To varying degrees Colorblindness affects 2-8% of men, and only 0.4% of women. Some types of color blindness should not be considered " hereditary disease", but rather - a feature of vision. According to research by British scientists, people who find it difficult to distinguish between red and green colors can distinguish many other shades. In particular, khaki shades that appear the same to people with normal vision.
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Myopia
With myopia (myopia), only objects located at a certain short distance can be clearly perceived by the eye, since their image is focused strictly on the retina. A person with myopia sees everything that is further away fuzzy and blurry. This happens because rays from more distant objects, refracted in the structures of the eye, form an image not on the retina, it is formed in front of the retina, and a person cannot see clear outlines. Causes of myopia: 1. The refractive power of the ocular media is too high,2. Elongated eyeball, 3. Inadequate change in lens curvature4. Changes in corneal curvature, 5. Injuries with displacement of the lens. Where do the causes of myopia come from? Of course, no one is immune from injury; it is most often an accident. But all other problems leading to myopia can be caused by heredity, too much visual stress, improper vision correction process or lack thereof.
Slide 25
Farsightedness
Farsightedness (hyperopia) is a condition in which the focusing of the image of distant objects (but only up to a certain distance) occurs on the retina, and a person sees them well. Images of other objects are focused behind the retina, so a person sees them blurry and unclear. Farsightedness is observed in all newborns; as the child and the eyeball grow, it goes away and vision becomes normal. Causes of farsightedness: Age-related changes in the structures of the eye, for example, loss of elasticity or shrinkage of the lens contractility ciliary muscle, Shortening of the eyeball. How does myopia differ from farsightedness? Firstly, by the peculiarities of vision: farsighted people see well only in the distance, myopic people only see close up. Secondly, these two conditions differ in the age of development, which, in turn, depends on the reasons. Myopia is most often caused genetically and fully develops by age 12. Farsightedness in most cases is the result age-related changes, occurring in the organs of vision. It begins to appear at the age of 35-50 or more years.
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Eye diseases
Amblyopia is a functional disorder of the visual system in which there is a decrease in vision that cannot be corrected with glasses or contact lenses, impaired contrast sensitivity and accommodative abilities of one or less often both eyes in the absence of any pathological changes organ of vision. Symptoms: deterioration of vision in one or both eyes, difficulty perceiving three-dimensional objects, estimating the distance to them, difficulties in learning.
Slide 27
Eye diseases
Anisocoria is a condition in which the pupils of the eyes differ in size. This phenomenon is quite common in the practice of doctors and does not always mean the presence of any pathology in the body. About 20% of the population has physiological anisocoria. Symptoms: the pupils of the right and left eyes differ in size.
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Eye diseases
Astigmatism A type of ametropia in which light rays cannot focus on the retina of the eye. In cases where the cause of astigmatism is an irregular shape of the cornea, it is called corneal, in cases of an abnormal shape of the lens - lenticular or lenticular. Their sum is total astigmatism. Symptoms: distortion, blur, ghosting, fast fatiguability eyes, constant eye strain, headache, the need to squint in order to better see an object.
Slide 3
Why do they say that the eye looks, but the brain sees?
Slide 4
Structure of the organ of vision
The organ of vision is the most important of the senses, providing a person with up to 95% of information.
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Functions of parts of the eye
Slide 7
The principle of the eye is similar to that of a camera.
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Optical system and light-receiving part of the eye
Slide 9
Retina
The light-receiving part is the retina. It contains light-sensitive cells - visual receptors, about 130 million rods, providing black and white vision, and about 7 million cones, providing information about color.
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Structure of the retina
Slide 11
The retina consists of several layers of cells:
- The outer layer adjacent to the choroid is a layer of black pigment cells. This layer absorbs light, preventing its scattering and reflection;
- three layers of cells: bipolar, ganglion, then their axons, uniting into the optic nerve;
Next comes the layer containing rods and cones.
Slide 12
- The maximum number of cones is located in the retina on the optical axis of the eye, opposite the pupil, this area is called the macula.
- In the place where the optic nerve leaves the eyeball, there are no receptors in the retina - a blind spot.
- The maximum number of rods is located on the periphery of the eye.
- Sticks contain visual pigment rhodopsin, a small amount of light is enough for its decomposition.
- In cones, under the influence of light, iodopsin decomposes, but more light is needed to excite the cones.
Slide 13
What happens on the retina
The light flux passes through:
- Cornea
- Iris
- Pupil
- Lens
- Vitreous body
- Retina
Retinal image is reduced and inverted
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Slide 15
- Light hits photosensitive cells;
- A photochemical reaction occurs (rhodopsin breakdown);
- The potential of photoreceptors changes;
- Excitement occurs;
- Along the optic nerve, excitation goes to the visual center of the cerebral cortex;
- The final analysis of excitation, image discrimination and sensation formation take place in the cortex.
Slide 16
As a result
- The brain sees, not the eye.
- Vision is a cortical process and depends on the quality of information received from the eye.
- That is why the eye looks and the brain sees.
