7. Visual System


optic disk: area where retinal ganglion cell axons leave the eye à optic nerve

-           no photoreceptors

-           blind spot


central retina

-           macula lutea (“yellow spot”, specialized for visual acuity)

-           fovea centralis (“central pit”, concentration of cones, no blood vessels)



-           rhodopsin (from Vitamin A)

-           nocturnal vision


RGC projections:

1.         LGN (lateral geniculate nucleus, thalamus)

2.         SC (superior colliculus, tectum of midbrain)

a.         pulvinar (thalamus)

                                                                i.      unconscious vision

b.         pons, III IV VI, reticular formation, cervical regions of spinal cord

                                                                i.      orientation to moving stimuli, movement-vision reflexes

3.         pretectum à EW nucleus (Edinger-Westphal nucleus = parasympathetic III, midbrain)

a.         pupillary reflex

b.         entirely subcortical

4.         hypothalamus

a.         ambient light