New Photoreceptor Discovery - Melanopsin Helps Control Biological Clock
Neuroscientists at John Hopkins report that they have identified a set of photoreceptors in the eye that monitor light levels to adjust the body clock rather than perceiving images. Unlike rods and cones, these melanopsin-containing cells are relatively insensitive to light when taken together, but individually are far more sensitive. They are, however, 5,000 times sparser than rods or cones, and respond very slowly so detect slow changes in light.