Final answer:
The optic nerve is an extension of the brain, formed by the axons from retinal ganglion cells in the eye, which transmit visual information to the brain via the magnocellular and parvocellular pathways.
Step-by-step explanation:
The optic nerve is an extension of the central nervous system and is directly connected to the brain. Specifically, the optic nerve is made up of the axons of retinal ganglion cells that originate in the retina of the eye. These cells collect visual information from the photoreceptor cells, which include rods and cones, and transmit it to the brain. The optic nerve fibers pass through the optic chiasm, a structure where some fibers cross over to the opposite side of the brain. This arrangement allows visual information from the right field of vision to be processed by the left hemisphere and vice versa, ensuring a combined field of view and depth perception.
The retinal ganglion cells' myelinated axons coalesce to form the optic nerve which carries various qualities of visual signals through different pathways. The magnocellular pathway carries information about form, movement, depth, and brightness differences, while the parvocellular pathway conveys color and fine detail.