The light-sensitive elements rods and cones are located in. Rods and cones of the retina - structure and functions

Cones and rods belong to the receptor apparatus of the eyeball. They are responsible for transmitting light energy by transforming it into a nerve impulse. The latter passes along the fibers of the optic nerve in central structures brain. Rods provide vision in low light conditions; they are capable of perceiving only light and dark, that is, black and white images. Cones are capable of perceiving different colors and are also an indicator of visual acuity. Each photoreceptor has a structure that allows it to perform its functions.

Structure of rods and cones

The sticks are shaped like a cylinder, which is why they got their name. They are divided into four segments:

Basal, connecting nerve cells;
A binder that provides connection with eyelashes;
Outer;
Internal, containing mitochondria that produce energy.

The energy of one photon is quite enough to excite the rod. This is perceived by a person as light, which allows him to see even in very low light conditions.

The rods contain a special pigment (rhodopsin), which absorbs light waves in two ranges.
Cones by appearance They look like flasks, which is why they have their name. They contain four segments. Inside the cones is another pigment (iodopsin), which provides the perception of red and green colors. Pigment responsible for recognition blue still not installed.

Physiological role of rods and cones

Cones and rods perform the main function of perceiving light waves and transforming them into a visual image (photoreception). Each receptor has its own characteristics. For example, rods are needed to see at dusk. If for some reason they stop performing their function, a person cannot see in low light conditions. Cones are responsible for clear color vision in normal lighting.

In another way, we can say that rods belong to the light-perceiving system, and cones belong to the color-perceiving system. This is the basis for differential diagnosis.

Video about the structure of rods and cones

Symptoms of damage to rods and cones

In diseases accompanied by damage to rods and cones, the following symptoms occur:

Decreased visual acuity;
The appearance of flashes or glare before the eyes;
Decreased twilight vision;
Inability to distinguish colors;
Narrowing of visual fields (in as a last resort formation of tubular vision).

Some diseases are very specific symptoms, which easily allow you to diagnose pathology. This applies to hemeralopia or. Other symptoms may be present in various pathologies, and therefore additional diagnostic testing is necessary.

Diagnostic methods for damage to rods and cones

To diagnose diseases in which there is damage to the rods or cones, it is necessary to perform the following examinations:

with state definition;
(study of visual fields);
Diagnosis of color perception using Ishihara tables or the 100-shade test;
Ultrasound examination;
Fluorescent hagiography, providing visualization of blood vessels;
Computer refractometry.

It is worth recalling once again that photoreceptors are responsible for color perception and light perception. Due to the work, a person can perceive an object, the image of which is formed in the visual analyzer. For pathologies

Complete the sentences 1) In case of severe bruises and burns, it is impossible... 2) The level of street noise is reduced.. Select the correct statements: 1.

The white membrane of the eye (sclera) is transparent.

2. Choroid eyes are bright red.

3. The nasolacrimal stream drains excess tear fluid into nasal cavity.

4. Receptors in the retina are rods and cones.

5. The central visual analyzer is located in the occipital lobe of the cortex cerebral hemispheres, and auditory - in the temporal.

6. Hearing receptors are located in eardrum.

7. Cause of irritation auditory receptors is the deformation of their hair cells, which occurs when the main membrane under the integumentary plate vibrates.

8. Thermal, tactile, muscle receptors, receptors that perceive pressure and pain take part in the sense of touch.

A1. The nervous system is formed by cells of nervous tissue, the features of which are

1. Rapid regeneration 2. Excitability and conductivity 3. Excitability and contractility 4. Fibrous structure
A2. Of the listed functions for spinal cord the following is not typical
1. Implementation of simple reflexes 2. Conducting signals from body receptors to the brain 3. Conducting commands from the brain to skeletal muscles 4. Management voluntary movements skeletal muscles

A3. The size of the pupil and the curvature of the lens are adjusted nerve centers located
1. B medulla oblongata 2. In the midbrain 3. In the cerebellum 4. in the occipital lobes of the cerebral hemispheres

A4.Centers conditioned reflexes located
1. in the cerebral cortex 2. in the medulla oblongata 3. in diencephalon 4. in the spinal cord

A5. Parasympathetic nervous system activates
1..at large physical activity 2. in case of danger 3. during stress 4. during rest

A6. An analyzer is a system that includes
1. sympathetic and parasympathetic fibers 2. receptor, sensory pathway, part of the central nervous system, motor pathway, executive body 3. neurons that perceive, conduct and process information 4. various departments brain
A7. When touching a bitter tablet with the tip of the tongue, a person does not feel the bitter taste, because...
1. receptors that perceive bitter taste are located in the walls of the esophagus 2. receptors that perceive bitter taste are located on the walls oral cavity 3. receptors that perceive bitter taste are located closer to the root of the tongue 4. humans do not have receptors that perceive bitter taste
A8. Twilight vision is provided
1. iris 2. cones 3. rods 4. lens
A9. As a result of irritation by dust or the ingress of microbes, the mucous membrane of the eye becomes inflamed - it develops
1. myopia 2. farsightedness 3. conjunctivitis 4. Cataract
A. 10 The auditory tube of the middle ear provides
. 1.fluid fluctuations in the cochlea inner ear 2. transfer sound vibrations from the eardrum to the dry bones of the middle ear 3.
3 conversion of mechanical vibrations into nerve impulses 4. Pressure equalization according to to different parties eardrum

B1. Choose three correct answers out of six. For myopia
1. the eyeball is shortened 2. the image is focused in front of the retina
3. It is necessary to wear glasses with biconvex lenses
4. Eyeball has an elongated shape
5.the image is focused behind the retina
6. Glasses with focusing lenses are recommended
Answer:______________

Establish a correspondence between the part of the nervous system and its functions FunctionsDivision of the nervous system

Please add more suggestions.

1. The image in the myopic eye is focused ... retina, and in farsighted ... her.
2. Myopia is corrected ... glasses, farsightedness ... .
3. At severe bruises and no burns .... .

4. The cause of inflammation of the middle ear can be the penetration of sore throat and influenza pathogens through ... into the middle ear.
5. Street noise levels are reduced .... .
6. Works well on swings .... .
7. To find out the smell of an object, you need to direct a stream of air to ... .Inhale vapors of an unfamiliar substance ... .

Check true statements.
1. The white membrane of the eye (sclera) is transparent.
2. The choroid of the eye is bright red.
3. The nasolacrimal duct drains excess tear fluid into the nasal cavity.
4. The receptors of the setin are rods and cones.
5. The central visual analyzer is located in the occipital lobe of the cerebral cortex, and the auditory analyzer is located in the temporal lobe.
6. Hearing receptors are located in the eardrum.
7. The cause of irritation of the auditory receptors is the deformation of their hair cells, which occurs when the main membrane under the octal plate vibrates.

8. Thermal, tactile, and muscle receptors that perceive pressure and pain take part in the sense of touch.
_________________________________________________________________
Choose the correct answer
1. The “blind spot” is located in the place where the following are located:
a) sticks;
b) cones;
c) exit of the optic nerve;
d) choroid.
2. Oval and round windows, covered with membrane, are located between:
A) auditory tube and pharynx;
b) external and middle ear;
c) middle and inner ear.

A15. What skin formation performs the excretory function?

1. epidermal cells

2. sweat glands

3. cold and heat receptors

4. subcutaneous fat tissue

A16. The somatic nervous system controls the work

1. skeletal muscles

2. heart and blood vessels

3. intestines

1. executive body

2. sensitive neuron

3. receptor

4. interneuron

A18. Which layer of the eye contains receptors in the form of rods and cones?

1. protein

2. vascular

3. rainbow

4. retina

A19. Social nature person manifests itself in

1. adaptation to upright walking

2. speech activity

4. formation of conditioned reflexes

A20. For a person's height great influence provide hormones

1. adrenal glands

2. pituitary gland

3. thyroid gland

4. pancreas

A21. An example of a mixed secretion gland

1. pituitary gland

3. pancreas

4. thyroid gland

A22. When reading books in a moving vehicle, muscle fatigue occurs

1. changing the curvature of the lens

2. upper and lower eyelids

3. regulating pupil size

4. changing the volume of the eyeball

A23. You should breathe through your nose, since in the nasal cavity

1. gas exchange occurs

2. a lot of mucus is formed

3. there are cartilaginous half rings

4. the air is warmed and purified

A24. Promotion blood pressure in humans it is

1. normotension

2. hyperdynamia

3. hypertension

4. hypotension

A25. To reduce swelling and pain when a joint is dislocated, you should:

1. warm the damaged joint

2. apply an ice pack to the injured joint

3. independently adjust the dislocation in the damaged joint

4. try, overcoming pain, to develop the damaged joint

HELP IS REALLY NECESSARY >>>MARK THE TRUE STATEMENTS.>>>

1 .The white membrane of the eye (sclera) is transparent. 2 . The choroid of the eye is bright red. 3 . The nasolacrimal duct drains excess tear fluid into the nasal cavity. 4. Receptors in the retina are rods and cones. 5 . The central visual analyzer is located in the occipital lobe of the cerebral cortex. and auditory - in the temporal 6 . Hearing receptors are located in the eardrum. 7. The cause of irritation of auditory receptors is the deformation of their hair cells that occurs when the main membrane under the cover plate vibrates. 8 . Thermal, tactile, and muscle receptors that perceive pressure and pain take part in the sense of touch.Please help!!!))

The main light-sensitive elements (receptors) are two types of cells: one in the form of a stalk - sticks 110-123 million. (height 30 microns, thickness 2 microns), others are shorter and thicker - cones 6-7 million. (height 10 microns, thickness 6-7 microns). They are distributed unevenly in the retina. The central fovea of the retina (fovea centralis) contains only cones (up to 140 thousand per 1 mm). Towards the periphery of the retina, their number decreases, and the number of rods increases.

Each photoreceptor - rod or cone - consists of a light-sensitive outer segment containing visual pigment and an inner segment that contains the nucleus and mitochondria that provide energy processes in the photoreceptor cell

The outer segment is a photosensitive area where light energy is converted into receptor potential. Electron microscopic studies have revealed that the outer segment is filled with membrane disks formed plasma membrane. In sticks, in each outer segment, contains 600-1000 disks, which are flattened membrane sacs arranged like a column of coins. Cones have fewer membrane disks. This partly explains more high sensitivity sticks to the light(a wand can excite anything one quantum of light, A it takes more than a hundred quanta to activate a cone).

Each disc is a double membrane consisting of a double layer phospholipid molecules , between which there are protein molecules. Retinal, which is part of the visual pigment rhodopsin, is associated with protein molecules.

The outer and inner segments of the photoreceptor cell are separated by membranes through which a beam of 16-18 thin fibrils. The internal segment passes into a process, with the help of which the photoreceptor cell transmits excitation through the synapse to the bipolar nerve cell in contact with it

The outer segments of the receptors face the pigment epithelium, so that light initially passes through 2 layers nerve cells and internal segments of receptors, and then reaches the pigment layer.

Cones operate in high light conditions - provide day and color vision, and the sticks- are responsible for twilight vision.

visible to us the spectrum of electromagnetic radiation lies between short-wave (wavelengthfrom 400nm) radiation, which we call violet light and long-wave radiation (wavelengthup to 700 nm ) called red. The rods contain a special pigment - rhodopsin, (consists of vitamin A aldehyde or retinal and protein) or visual purple, the maximum of the spectrum, the absorption of which is in the region of 500 nanometers. It is resynthesized in the dark and fades in light. With a lack of vitamin A, the twilight vision- "night blindness".

In the outer segments of the three types of cones ( blue-, green- and red-sensitive) contains three types of visual pigments, the maximum absorption spectra of which are in blue (420 nm), green(531 nm) And red(558 nm) parts of the spectrum. Red cone pigment got the name - "iodopsin". The structure of iodopsin is close to rhodopsin.

Let's look at the sequence of changes:

Molecular physiology of photoreception: Intracellular recordings from cone and rod animals have shown that in the dark, a dark current flows along the photoreceptor, leaving the inner segment and entering the outer segment. Lighting leads to a blockade of this current. The receptor potential modulates the release of the transmitter ( glutamate) at the photoreceptor synapse. It has been shown that in the dark the photoreceptor continuously releases a transmitter that acts depolarizing way onto the membranes of postsynaptic processes of horizontal and bipolar cells.

Rods and cones have unique electrical activity among all receptors; their receptor potentials when exposed to light are hyperpolarizing, action potentials do not arise under their influence.

(When light is absorbed by a molecule of the visual pigment - rhodopsin, an instantaneous isomerization its chromophore group: 11-cis-retinal is converted to trans-retinal. Following the photoisomerization of retinal, spatial changes occur in the protein part of the molecule: it becomes discolored and passes into the state methorodopsin II As a result of this, the visual pigment molecule acquires the ability to interact with another near-membrane proteinG uanosine triphosphate (GTP) -binding protein – transducin (T) .

In complex with metarhodopsin, transducin enters an active state and exchanges ganosite diphosphate (GDP) bound to it in the dark for (GTP). Transfducin+ GTP activates a molecule of another near-membrane protein - the enzyme phosphodiesterase (PDE). Activated PDE destroys several thousand cGMP molecules .

As a result, the concentration of cGMP in the cytoplasm of the outer segment of the receptor decreases. This leads to the closure of ion channels in the plasma membrane of the outer segment that were open in the dark and through which inside the cell included Na + and Ca. Ion channels close due to the concentration of cGMP, which kept the channels open, drops. It has now been found that the pores in the receptor open due to cGMP cyclic guanosine monophosphate .

Mechanism for restoring the original dark state of the photoreceptor associated with increased concentrations of cGMP. (in the dark phase with the participation of alkaldehydrogenase + NADP)

Thus, the absorption of light by photopigment molecules leads to a decrease in permeability for Na, which is accompanied by hyperpolarization, i.e. the emergence of receptor potential. The hyperpolarizing receptor potential that arises on the membrane of the outer segment then spreads along the cell to its presynaptic end and leads to a decrease in the rate of transmitter release - glutamate . In addition to glutamate, retinal neurons can synthesize other neurotransmitters, such as acetylcholine, dopamine, glycine GABA.

Photoreceptors are connected to each other by electrical (slot) contacts. This connection is selective: sticks are connected to sticks, etc.

These responses from photoreceptors converge on horizontal cells, which lead to depolarization in neighboring cones, creating negative feedback that increases light contrast.

At the receptor level, inhibition occurs and the cone signal no longer reflects the number of absorbed photons, but carries information about the color, distribution and intensity of light incident on the retina in the vicinity of the receptor.

There are 3 types of retinal neurons - bipolar, horizontal and amacrine cells. Bipolar cells directly connect photoreceptors with ganglion cells, i.e. transmit information through the retina in the vertical direction. Horizontal and amacrine cells transmit information horizontally.

Bipolar cells occupy in the retina strategic position since all signals arising in the receptors arriving at the ganglion cells must pass through them.

It has been experimentally proven that bipolar cells have receptive fields in which they highlight center and periphery (John Dowling - et al. Harvard Medical School).

A receptive field is a set of receptors that send signals to a given neuron through one or more synapses.

Receptive field size: d=10 µm or 0.01 mm - outside the central fossa.

In the hole itselfd=2.5µm (thanks to this we are able to distinguish 2 points when visible distance between them there are only 0.5 arc minutes - 2.5 microns - if you compare, this is a 5-kopeck coin at a distance of about 150 meters)

Starting from the level of bipolar cells, neurons of the visual system differentiate into two groups that react in opposite ways to lighting and darkening:

1 - cells, excited when illuminated and inhibited when darkened "on" - neurons And

Cells excited when darkened and inhibited when illuminated - " off" - neurons. A cell with an on-center discharges at a noticeably increased frequency.

If you listen to the discharges of such a cell through a loudspeaker, then first you will hear spontaneous impulses, individual random clicks, and then after turning on the light, a volley of impulses appears, reminiscent of a machine gun burst. On the contrary, in cells with an off-reaction (when the light is turned off - a volley of impulses) This separation is preserved at all levels of the visual system, up to and including the cortex.

Within the retina itself, information is transmitted in a non-pulse way (propagation and transsynaptic transmission of gradual potentials).

In horizontal, bipolar and amocrine cells, signal processing occurs through slow changes in membrane potentials (tonic response). PD is not generated.

The responses of rods, cones, and horizontal cells are hyperpolarizing, and the responses of bipolar cells can be either hyperpolarizing or depolarizing. Amacrine cells create depolarizing potentials.

To understand why this is so, we need to imagine the effect of a small bright spot. The receptors are active in the dark, and light, causing hyperpolarization, reduces their activity. If excitatory synapse, bipolar will be activated in the dark, A inactivate in the light; if the synapse is inhibitory, the bipolar cell is inhibited in the dark, and in the light, turning off the receptor, it removes this inhibition, i.e. the bipolar cell is activated. That. whether the receptor-bipolar synapse is excitatory or inhibitory depends on the transmitter released by the receptor.

Horizontal cells participate in the transmission of signals from bipolar cells to ganglion cells, which transmit information from photoreceptors to bipolar cells and further to ganglion cells.

Horizontal cells respond to light with hyperpolarization with pronounced spatial summation.

Horizontal cells do not generate nerve impulses, but the membrane has nonlinear properties that ensure impulse-free signal transmission without attenuation.

Cells are divided into two types: B and C. B-type, or luminance, cells always respond with hyperpolarization, regardless of the wavelength of light. C-type cells, or chromatic ones, are divided into two- and three-phase. Chromatic cells respond with either hyper or depolarization depending on the length of the stimulating light.

Biphasic cells are either red-green (depolarized by red light, hyperpolarized by green) or green-blue (depolarized by green, hyperpolarized by blue). Triphasic cells are depolarized by green light, while blue and red light cause hyperpolarization of the membrane. Amacrine cells regulate synaptic transmission at the next stage from bipolar to ganglion cells.

The dendrites of amacrine cells branch in the inner layer, where they contact the processes of bipolars and the dendrites of ganglion cells. Centrifugal fibers coming from the brain end on amacrine cells.

Amacrine cells generate gradual and pulsed potentials (phasic response). These cells respond with rapid depolarization to light on and off and exhibit weak

spatial antagonism between center and periphery.

The retina of the eye is the main part visual analyzer. Here the perception of electromagnetic light waves occurs, their transformation into nerve impulses and transmission to optic nerve. Day (color) and night vision are provided by special receptors in the retina. Together they form the so-called photosensory layer. Based on their shape, these receptors are called cones and rods.

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General concepts

Microscopic structure of the eye

Histologically, the retina of the eye is divided into 10 cell layers. The outer light-sensitive layer consists of photoreceptors (rods and cones), which are special formations of neuroepithelial cells. They contain visual pigments that can absorb certain wavelengths of light. Rods and cones are distributed unevenly on the retina. The main number of cones are located in the center, while the rods are located on the periphery. But this is not their only difference:

1. Rods provide night vision. This means that they are responsible for the perception of light in low light conditions. Accordingly, with the help of chopsticks a person can see objects only in black and white.
2. Cones provide visual acuity during the day. With their help, a person sees the world in color.

Rods are sensitive only to short waves, the length of which does not exceed 500 nm (the blue part of the spectrum). But they are active even when diffused light, when the photon flux density is reduced. Cones are more sensitive and can perceive all color signals. But to excite them, light of much higher intensity is required. In the dark, visual work is carried out by rods. As a result, at dusk and at night a person can see the silhouettes of objects, but does not feel their color.

Dysfunction of the retinal photoreceptors can lead to various pathologies view:

impaired color perception (color blindness);
inflammatory diseases of the retina;
retinal dissection;
twilight vision impairment (night blindness);
photophobia.

Cones

People with good eyesight have about seven million cones in each eye. Their length is 0.05 mm, width - 0.004 mm. Their sensitivity to the flow of rays is low. But they qualitatively perceive the entire gamut of colors, including shades.

They are also responsible for the ability to recognize moving objects, since they respond better to lighting dynamics.

Cone structure

Schematic structure of cones and rods

The cone has three main segments and a constriction:

1. Outer segment. It contains the light-sensitive pigment iodopsin, which is located in the so-called half-discs - folds of the plasma membrane. This part of the photoreceptor cell is constantly renewed.
2. The constriction formed by the plasma membrane serves to transfer energy from internal segment outside. It represents the so-called cilia that carry out this connection.
3. Internal segment – area of active metabolism. Mitochondria are located here - the energy base of cells. In this segment there is an intense release of energy necessary for the visual process.
4. The synaptic ending is the area of synapses - contacts between cells that transmit nerve impulses to the optic nerve.

Three-component hypothesis of color perception

It is known that cones contain a special pigment - iodopsin, which allows them to perceive all color spectrum. According to the tripartite hypothesis of color vision, there are three types of cones. Each of them contains its own type of iodopsin and is capable of perceiving only its part of the spectrum.

1. L-type contains the pigment erythrolab and captures long waves, namely the red-yellow part of the spectrum.
2. M-type contains the pigment chlorolab and is capable of perceiving medium waves emitted by the green-yellow region of the spectrum.
3. S-type contains cyanolab pigment and reacts to short waves, perceiving the blue part of the spectrum.

Many scientists involved in the problems of modern histology note the inferiority of the three-component hypothesis of color perception, since confirmation of the existence of three types of cones has not yet been found. In addition, the pigment that was previously given the name cyanolab has not yet been discovered.

Two-component hypothesis of color perception

According to this hypothesis, all retinal cones contain both eritolab and chlorolab. Therefore, they can perceive both long and middle part spectrum And its short part, in this case, is perceived by the rhodopsin pigment contained in the rods.

This theory is supported by the fact that people who are unable to perceive short waves of the spectrum (that is, the blue part of it) simultaneously suffer from visual impairment in low light conditions. Otherwise, this pathology is called “ night blindness"and is caused by dysfunction of the retinal rods.

Sticks

Ratio of rods (gray) and cones (green) in the retina

The rods look like small elongated cylinders, about 0.06 mm long. Adult healthy person has approximately 120 million such receptors in each eye on the retina. They fill the entire retina, concentrating mainly on the periphery. The macula (the area of the retina where vision is sharpest) contains practically no rods.

The pigment that makes the rods highly sensitive to light is called rhodopsin or visual purple. . In bright light, the pigment fades and loses this ability. At this moment, it is susceptible only to short light waves, which make up the blue region of the spectrum. In the dark, its color and quality are gradually restored.

Structure of rods

Rods have a structure similar to that of cones. They consist of four main parts:

1. The outer segment with membrane discs contains the pigment rhodopsin.
2. The connecting segment or cilium makes contact between the outer and inner sections.
3. The inner segment contains mitochondria. This is where the energy generation process takes place.
4. The basal segment contains nerve endings and transmits impulses.

The exceptional sensitivity of these receptors to the effects of photons allows them to convert light stimulation into nervous excitement and transmit it to the brain. This is how the process of perceiving light waves takes place. by the human eye– photoreception.

Man is the only living creature capable of perceiving the world in all the richness of its colors and shades. Eye protection from harmful effects and prevention of visual impairment will help preserve this unique ability for many years.

The sticks have maximum light sensitivity, which ensures their response to even the most minimal external light flashes. The rod receptor begins to operate even when receiving energy of one photon. This feature allows the rods to provide twilight vision and helps to see objects as clearly as possible in the evening hours.

However, since the retinal rods contain only one pigment element, designated rhodopsin or visual purple, shades and colors cannot differ. The rod protein rhodopsin cannot react as quickly to light stimuli as the pigment elements of cones do.

Cones

The coordinated work of rods and cones, despite the fact that their structure differs significantly, helps a person to see the entire surrounding reality in full qualitative volume. Both types of retinal photoreceptors complement each other in their work, this helps to obtain the most clear, clear and bright image possible.

Cones get their name because their shape is similar to the flasks used in various laboratories. The adult retina contains about 7 million cones.
One cone, like a rod, consists of four elements.

The outer (first) layer of the cones of the retina is represented by membrane discs. These discs are filled with iodopsin, a color pigment.
The second layer of cones in the retina is the connecting tier. It acts as a constriction, which allows the formation of a certain shape of this receptor.
The inner part of the cones is represented by mitochondria.
In the center of the receptor there is a basal segment that acts as a connecting link.

Iodopsin is divided into several types, which allows for full sensitivity of cones visual pathway in perception various parts light spectrum.

By dominance different types pigment elements, all cones can be divided into three types. All these types of cones work in concert, and this allows a person to normal vision appreciate all the richness of shades of the objects he sees.

Structure of the retina

IN general structure The rods and cones occupy a very specific place in the retina. The presence of these receptors on nerve tissue, which consists of retina, helps to quickly convert the resulting light flux into a set of pulses.

The retina receives the image, which is projected by the eye area of the cornea and the lens. After this, the processed image in the form of impulses arrives through the visual pathway to the corresponding part of the brain. The complex and fully formed structure of the eye allows complete processing of information in a matter of moments.

Most of the photoreceptors are concentrated in the macula - the central region of the retina, which, due to its yellowish tint, is also called macular spot eyes.

Functions of rods and cones

The special structure of the rods allows them to detect the slightest light stimuli at the lowest degree of illumination, but at the same time these receptors cannot distinguish the shades of the light spectrum. Cones, on the contrary, help us see and appreciate all the richness of the colors of the world around us.

Despite the fact that, in fact, rods and cones have different functions, only the coordinated participation of both groups of receptors can ensure the smooth operation of the entire eye.

Thus, both photoreceptors are important for our visual function. This allows us to always see a reliable picture, regardless of weather conditions and time of day.

Rhodopsin - structure and functions

Rhodopsin is a group of visual pigments, the structure of a protein belonging to chromoproteins. Rhodopsin, or visual purple, gets its name from its bright red hue. The purple coloration of the retinal rods has been discovered and proven in numerous studies. The retinal protein rhodopsin consists of two components - a yellow pigment and a colorless protein.

Under the influence of light, rhodopsin decomposes, and one of the products of its decomposition affects the occurrence of visual stimulation. Reduced rhodopsin acts in twilight lighting, and the protein is responsible for night vision at this time. In bright light, rhodopsin decomposes and its sensitivity shifts to the blue region of vision. The retinal protein rhodopsin is completely restored in humans in about 30 minutes. During this time, twilight vision reaches its maximum, that is, a person begins to see more clearly in the dark.