The optic nerve transmits an impulse from the retina to the brain, where vision is interpreted. The retina lines the inner surface of the eye and is sensitive to light waves. Photoreceptor cells are located in the retina and are of two types. Cones can sense color and are mainly used in daytime vision and rods can sense black and white and function mainly in dim light. When light strikes the retina, a nerve impulse is triggered. This is an electrical and chemical signal that is interpreted in the vision center of the cerebrum cortex.