After passing through the lens and vitreous body, rays of light fall on the inner shell of the eyeball – the retina. This multilayer formation contains visual receptors – cones (about 7 million) and rods (about 130 million). Rods contain the visual pigment rhodopsin, they are more sensitive than cones, and provide black and white vision in low light. The cones contain the visual pigment iodopsin and provide color vision in good light conditions. It is believed that there are three types of cones perceiving red, green and purple colors, respectively. All other shades are determined by a combination of excitation in these three types of receptors. Under the influence of light quanta, visual pigments are destroyed, generating electrical signals that are transmitted from the rods and cones to the optic nerve, and impulses enter the brain through its fibers. At the exit point of the optic nerve from the retina, there are no cones and rods. This place is called a blind spot.
Most cones are located directly opposite the pupil – in the yellow spot, and in the peripheral parts of the retina there are almost no cones, there are only sticks.
After exiting the eyeball, the optic nerve follows the superior tubercles of the quadruple of the midbrain, where visual information is subjected to primary processing. On the axons of the neurons of the superior tubercles, visual information enters the visual nuclei of the thalamus, and from there into the occipital lobes of the cerebral cortex. It is there that the visual image that we subjectively feel, that is, see, is formed.
The optical system of the eye forms on the retina not only a reduced, but also an inverted image of the object. Signal processing in the central nervous system occurs in such a way that objects are perceived in a natural position.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.