Optic Nerve and Visual Pathways

Question 1

Rods and Cones

Answer 1

Outer segments contains discs containing photopigment

Inner segment has cell body, axon and synaptic terminals

Question 2

Phototransduction

Answer 2

Rods have rhodopsin
Cones have opsin (transmembrane proteins, contains light sensitive molecule retinal)

Answer 3

Photoreceptors can have graded responses.

Retinal ganglion cells not graded response - action potential/

Question 4

What happens at the Lateral Geniculate Nucleus?

Answer 4

Synapse.

Question 5

Pathway to occipital lobe

Answer 5

Optic nerve –> optic chiasm –> optic tracts –> lateral genicula nucleus –> optic radiations (one superiorly, one laterally on both sides) –> occipital lobe

Question 6

Light reflex (why both pupils constrict when light in only one eye)

Answer 6

Action potential from right eye reach both right and left pretectal nuclei.

The pretectal nuclei stimulate both sides of the Eddinger-Westphal nucleus even though the light was perceived only in the right eye.

The right and left sides of the Eddinger-Westphal nuclei generate action potentials through the right and left oculomotor nerves causing both pupils to constrict.