How Do Nerve Impulses From the Retina Reach the Brain?

When light reaches the rods and cones in the retina at the back of the eyeball, a series of complex chemical reactions takes place, forming the chemical rhodopsin that converts the light into electrical impulses, according to the Vision for Tomorrow Foundation. The electrical impulses travel to the optic nerve.

The optic nerve, which is a collection of retinal nerve fibers, conducts the electrical impulses to the optic chasm of the brain, according to the Vision for Tomorrow Foundation. Half of the retinal nerve fibers from each retina's inner half cross to the other side of the brain. The nerve fibers meet at the occipital lobe in the back of the brain. Vision is interpreted by the brain in the primary visual cortex.

Each rod and cone, which are photoreceptors, in the retina is connected to the optic nerve by a tiny nerve branch, according to the Merck Manual Home Edition.

The retina, a complex and multi-layered nervous tissue, covers two-thirds of the back of the eyeball, according to the Encyclopaedia Britannica. The retina is an extension of the brain that was formed from neural tissue. Between and within the retinal layers, complex synapses occur to assemble the nerve impulses generated by the rods and cones into a coherent pattern.