The visual analyzer is the most complex and subtle system of perception of visual objects. A person is able to feel all the beauty of the world around him, his riot of colors and color shades thanks to the organ of vision and the instant ability of the brain to collect streams of visual, light information and also quickly analyze them. The human visual analyzer is the visual path through which all visual information enters the human brain. It allows you to connect the retina of the eye with brain structures, turning them into one constantly functioning mechanism.
The structure of the visual analyzer
The visual pathway, as noted above, begins with peripheral neurons that are located in different layers of the retina of the human eye. From these neuronal cells come very thin and fragile fibers, or axons, which, without interruption, reach the so-called external bent body of the internal capsule. These axons go to the brain not scattered, but as a single array, which is represented by the optic nerve of each eye. As part of each optic nerve, or n. opticus, there are about one million nerve fibers. All of them fully correspond to the quantitative composition of the receptor fields of the retina. This fact suggests that the visual analyzer is able to perceive pulses from almost any corner of the retina where the photoreceptors are located.
N.opticus itself can be topographically divided into four important anatomical departments:
- intragasic, or intraocularis,
- intraorbital, or interorbitalis,
- intraosseous (intracranial), or intercostalis,
- intracranial, or intercranialis.
Such a division is very important for practicing ophthalmologists to know. this will make it easier for them to make a correct diagnosis and predict visual function in affected patients in the future. The visual analyzer is also specific in that it alone has a complex cross of nerve fibers, called a "chiasm". The essence of this intersection is that the fibers that pass in the optic nerve begin to divide in the chiasm in such a way that after it the fibers appear in the optic tract, both from the right half of the eye and from the left.
However, the features that the visual analyzer possesses do not end there. After the intersection of two optic nerves, the fibers receive, as mentioned above, a different name - the optic tract. In the right optic tract there are non-crossed axonal processes of the right temporal half of the retina of the right eyeball and crossed fibers from the medial, that is, nasal, half of the retina of the left eyeball. Accordingly, the following can be observed in the left tract: non-crossed nerve fibers from the lateral half of the retina of the left eyeball and crossed axonal processes of the medial half of the retina of the right eyeball. Both the right and left optic tract are directed to the subcortical centers responsible for visual sensations. The bulk of the fibers ends in the external cranked bodies. From these anatomical formations of the brain, neurites depart, which form a bunch of Graziole. This bundle, or radiance, ends in the occipital lobe, where specific visual fields are located. It is in them, according to scientists, that the entire process of processing visual material occurs. The speed of such reactions is super powerful, amounting to several tenths, or even hundredths of a second. A moment - and a person learns and understands what his slightly wandering gaze “fell” at that moment. This is unique in the optical system of such an important sensory organ as the organ of vision. It is vision that gives people a greater percentage of information than any other sensory organ.