Sticks and cones. The cones of the retina. Structure of the retina

Vision is one of the ways to get to know the surrounding world and navigate in space. Despite the fact that other senses are also very important, with the help of the eye people perceive about 90% of all information coming from the environment. Thanks to the ability to see what is around us, we can judge events, distinguish objects from each other, and also notice threatening factors. The eyes of man are arranged so that in addition to the objects themselves, they also distinguish colors in which our world is colored. For this, there are special microscopic cells - rods and cones, which are present in the retina of each of us. Thanks to them, the information we received about the form of the environment is transmitted to the brain.

Structure of the eye: Scheme

Despite the fact that the eye takes up so little space, it contains many anatomical structures, thanks to which we have the ability to see. The organ of vision is almost directly connected to the brain, and with the help of special research, ophthalmologists see the intersection of the optic nerve. The eyeball has the shape of a ball and is located in a special notch - the orbit, which forms the bones of the skull. To understand why multiple structures of the organ of vision are needed, it is necessary to know the structure of the eye. The diagram shows that the eye consists of such formations as the vitreous, the lens, the anterior and posterior chambers, the optic nerve and the membranes. Outside, the organ of vision is covered by a sclera - the protective frame of the eye.

Shells of the eye

The sclera performs the function of protecting the eyeball from damage. It is the outer shell and takes about 5/6 of the surface of the organ of vision. A part of the sclera that is located outside and leaves directly to the environment is called the cornea. It has inherent properties, thanks to which we have the ability to clearly see the world around us. The main ones are transparency, mirror, humidity, smoothness and the ability to pass and refract rays. The rest of the outer shell of the eye - the sclera - consists of a dense connective tissue base. Below it is the next layer - vascular. The middle shell is represented by three formations, arranged in sequence: the iris, the ciliary body and the choreoid. In addition, the vascular layer includes the pupil. It is a small hole, not covered with an iris. Each of these formations has its own function, which is necessary to ensure vision. The last layer is the mesh of the eye. She is in direct contact with the brain. The structure of the retina is very difficult. This is due to the fact that it is considered to be the most important envelope of the organ of vision.

Structure of the retina

The inner shell of the organ of vision is a constituent part of the brain substance. It is represented by layers of neurons that cover the eye from the inside. Thanks to the mesh shell, we get an image of everything that is around us. It focuses all the refracted rays and are compiled into a clear object. Nerve cells of the retina pass into the optic nerve, the fibers of which information reaches the brain. On the inner shell of the eye there is a small spot that is in the center and has the greatest ability to see. This part is called the macula. In this place there are visual cells - rods and cones of the eye. They provide us with both day and night vision of the surrounding world.

Functions of rods and cones

These cells are located on the retina of the eye and are necessary for seeing. Sticks and cones are converters of black and white and color vision. Both types of cells act as photosensitive receptors of the eye. The cones are so named because of their conical shape, they are the connecting link between the mesh shell and the central nervous system. Their main function is the transformation of light sensations received from the external environment into electrical signals (impulses) processed by the brain. Specificity to the recognition of daylight belongs to the cones due to the pigment contained in them - iodopsin. This substance has several kinds of cells that perceive different parts of the spectrum. Wands are more sensitive to light, so their main function is more difficult - providing visibility at dusk. They also contain a pigment basis - the substance of rhodopsin, which is discolored when sunlight hits.

The structure of rods and cones

The name of these cells is due to its shape - cylindrical and conical. Sticks, unlike cones, are located more on the periphery of the retina and are practically absent in the macula. This is due to their function - providing night vision, as well as peripheral fields of vision. Both types of cells have a similar structure and consist of 4 parts:

1. The outer segment - in it is the main pigment of the rod or cones, covered with a shell. Rhodopsin and iodopsin are found in special containers - disks.
2. The cilium is the part of the cell that provides the relationship between the outer and inner segments.
3. Mitochondria - they are necessary for energy metabolism. In addition, they contain EPS and enzymes, which ensure the synthesis of all cellular components. All this is in the internal segment.
4. Nerve endings.

The number of photosensitive receptors on the retina is very different. Stem cells are about 130 million. The cones of the retina are much inferior to them in quantity, on average there are about 7 million.

Features of transmission of light pulses

Sticks and cones are able to perceive the light flux and transmit it to the central nervous system. Both types of cells are able to work in the daytime. The difference is that the photosensitivity of the cones is much higher than the rods. Transmission of received signals is due to interneurons, to each of which several receptors are attached. The combination of several rod cells makes the sensitivity of the organ of vision much larger. This phenomenon was called "convergence." It provides us with an overview of several fields of vision, as well as the ability to capture the various movements that are taking place around us.

Ability to perceive colors

Both types of retina receptors are needed not only to distinguish between day and twilight vision, but also to determine color images. The structure of the human eye allows a lot: to perceive a large area of the environment, to see at any time of the day. In addition, we have one of the interesting abilities - binocular vision, which allows to significantly expand the review. Rods and cones are involved in the perception of almost the entire color spectrum, so that people, unlike animals, distinguish all the colors of this world. Color vision is mostly provided by cones, which are of three types (short, medium and long wave). Nevertheless, the rods also have the ability to perceive a small part of the spectrum.