Visual System

          Visual System

The human visual system comprises three main parts: the eye, the lateral geniculate nucleus (LGN) and the part of the cortex brain that processes the visual information – the visual cortex.

The human visual system encompasses the eyes and brain structures responsible for processing light and creating a visual perception of the world.

It involves the detection, transduction, and interpretation of light, ultimately enabling us to construct an image and a mental model of our surroundings.

Two broad "streams" of projections from primary visual cortex have been identified: a ventral stream projecting to the inferotemporal cortex and a dorsal stream projecting to the posterior parietal cortex.

The visual pathways perform the function of receiv- ing, relaying, and ultimately processing visual informa- tion.

These structures include the eye, optic nerves, chiasm, tracts, lateral geniculate nucleus (LGN) of the thalamus, radiations, striate cortex, and extrastriate association cortices.

Key Components and Their Functions:

Eyes:

    The primary organ of sight, containing the cornea, lens, retina, and optic nerve.

Cornea and Lens:

               Focus light onto the retina.

Retina:

       A light-sensitive layer at the back of the eye containing photoreceptor cells (rods and cones) that convert light into electrical signals.

Optic Nerve:

            A bundle of nerve fibers that carries visual information from the retina to the brain.

Brain:

      The visual cortex, located in the occipital lobe, is responsible for processing visual information.

Visual Pathway:

              The neural pathway that transmits visual information from the retina to the brain, including the optic nerve, optic chiasm, optic tracts, lateral geniculate nucleus, and visual cortex.

Visual Cortex:

             The brain's processing center for visual information, including areas like the primary visual cortex (V1) and extrastriate areas (V2, V3, V4, V5).

Lateral Geniculate Nucleus (LGN):

                                A relay station in the thalamus that receives signals from the retina and transmits them to the visual cortex.

Process of Vision:

:Light enters the eye through the cornea and is focused by the lens onto the retina.

:Photoreceptor cells in the retina convert light into electrical signals.

:These signals are transmitted through the optic nerve to the brain.

:The LGN relays the signals to the visual cortex.

:The visual cortex processes the information, allowing us to perceive shapes, colors, motion, and depth.

Visual Cortex

Primary Visual Cortex (V1, striate cortex, Brodmann area 17).

Visual Area Two (V2, secondary visual cortex, or prestriate cortex).

Visual Area Three (V3).

Visual Area Four (V4, extrastriate cortex).

Visual Area Five (V5, middle temporal cortex).

Inferotemporal Cortex.