visual system overview

visual system overview

1. THE EYE

   • focus light waves onto retina
   • cells in retina transduce light into action potentials
     • the neuronal signals are transmitted to nervous system

2. OPTIC NERVE

   • bundle of axons from the last layer of neurones in the retina

3. OPTIC CHIASMA

   • optic nerves need to cross, there are no synapses here, some axons cross but no communication between neurones

4. LATERAL GENICULATE NUCLEUS (LGN)

   • primary relay system from eye to brain
   • axons leaving the retina via optic nerve synpase with a new set of neurones here
   • contains 6 layers of neurones - 'maps' one half of the visual field

5. SUPERIOR COLLICULUS

   • involved in eye movements
   • older than LGN
   • minor in humans, does most of visual processing in lower animals

6. OPTIC RADIATIONS

   • axons from cells that synapse with optic nerve fibers in LGN fan out in optic radiations as they go to the primary visual cortex
   • info from each eye still kept separate

7. STRIATE CORTEX

   • primary visual cortex
     • first place where visual info is received and processed
   • neurons from LGN synapse here then branch out