CN II. Optic Nerve
The optic nerve originates from the bipolar cells of the retina which are connected to the specialized receptors in the retina (rod and cone cells). Light strikes the rod and cone cells and electrical impulses are transduced and transmitted to the bipolar cells. The bipolar cells in turn transmit electrical activity to the central nervous system through the optic nerve. The optic nerve exits the back of the eye in the orbit and enters the optic canal and exits into the cranium. It enters the central nervous system at the optic chiasm (crossing) where the nerve fibers become the optic tract just prior to entering the brain.