Anatomy of the visual pathways.
Basic idea:
Retina -> optic nerve -> crossing over in optic chiasm -> optic tracts -> lateral geniculate nucleus -> optic radiation -> primary visual cortex
1) Retina:
Together the cornea and lens refract light into a small image and shine it on the retina. The retina transduces this image into electrical pulses using rods and cones. Rods and cones transmit the impulse to ganglia cells in the retina. The axons of all the ganglia cells gather together and form the optic nerve.
2) Optic nerve:
- runs through optic canal until it reaches the optic chiasm
3) Optic chiasm:
- Upon reaching the optic chiasm the nerve fibers decussate (left becomes right)
- as you can see in the picture, not all fibers of the optic nerve cross to the other site:
- fibers arising from the nasal side of each eye cross over
- fibers arising from the temporal side of each eye do not cross over
4) optic tracts:
- the fibers leaving the optic chiasm gather together and form the optic tract
- the optic tracts then carries the impulses to the lateral geniculate nucleus of the thalamus
5) optic radiation:
- fibers forming the optic radiation carry the impulses from the lateral geniculate nucleus to the primary visual cortex