Retina and the CNS

When sunlight enters the eye, it strikes the light-sensitive retina. Remember, the retina is part of the central nervous system (CNS) and is connected to the brain via the optic nerve. The retina contains different types of cells. The photoreceptor cells are sensitive to light. I’m sure you’ve heard of rods and cones. These cells are specialized neurons in the human eye. Rods are more sensitive to light and help you see under low-light conditions. They do not process color vision, however. Cones are capable of color vision and are responsible for high spatial acuity. They need more light to produce a correct signal, however, so may find it difficult to process color on a dark night outdoors. The photosensitive retinal ganglion cells discovered only in the past decade or so, communicate not only with the master circadian pacemaker located in the suprachiasmatic nuclei or SCN of the hypothalamus, but also with many other brain areas that are known to be involved in the regulation of several functions including health.