16″ x 20″
This is a depiction of the rods and cones of the eye; they are specialized neurons found in the retina that are responsible for vision. The human retina contains about 120 million rod cells and 6 million cone cells. Thesphotoreceptor cells convert light to electrical signals to send information to the occipital lobe of the cerebral cortex so that we can see. Rods are the most numerous photoreceptor cell, depicted here in black and white, are activated at very low light levels. Cones, depicted in colors, are responsible for color vision. Red cones are the most numerous, followed by green and then blue. Activation of cones requires significantly more light, and thus the reason we do not see color at night is that these photoreceptors are not activated. The signals from the rods and cones is transmitted through bipolar cells, depicted in the bottom of the picture, to the optic nerve. Pigmented epithelial cells, depicted on the top of the image, provide structure and nourishment to the photoreceptors.