Final answer:
Melanopsin ganglion cells are a type of retinal ganglion cell that responds to the presence or absence of light. They play a role in establishing the circadian rhythm of our bodies by sending information about day length. These cells project their axons to the suprachiasmatic nucleus of the hypothalamus.
Step-by-step explanation:
Melanopsin ganglion cells are a type of retinal ganglion cell (RGC) that are photosensitive, meaning they respond to the presence or absence of light. Unlike the photoreceptors (rods and cones), melanopsin ganglion cells cannot be used to perceive images. Their main role is to send information about day length, allowing the circadian rhythm of our bodies to be established. These cells project their axons from the optic chiasm to the suprachiasmatic nucleus of the hypothalamus, which plays a role in regulating our internal body clock.