Cranial Nerve II. DLA

Question 1

What is the stimulus of light?

Answer 1

• Signal is light
• Special sense of vision

• Photoreception arises from the retina and ganglion cell axons coalesce as the optic nerve
– leaves the back of the eyeball (blind spot)
– fibers from each side of the eyeball continue traveling on that side – passes through the optic canal

Question 2

What are the layers of the optic nerve?

Answer 2

Photoreceptive layer is divided into temporal and nasal portions based on the location
Light from the central region is caught by the temporal field
Light from the peripheral regions is caught by the nasal fibers

Question 3

Outline the path of the optic nerve

Answer 3

• The left and right optic nerves converge to form the optic chiasm
– closely associated with the stalk of the pituitary gland
– at this point the nasal fibers cross over to the opposite side

• The optic tracts pass from the chiasm to the thalamus (lateral geniculate nuclei)
• Because the nasal fibers cross over we have a wide visual field and depth perception created by the binocular visio