CN 2: Orbital Nerve Flashcards
What type of axon?
Special sensory afferent
Where does the the nerve originate and terminate?
Originates in the eye (retinal ganglion cells) to lateral geniculate nucleus (in thalamus)
What is the fovea?
Center of visual field; where eye is trying to focus light to
What is the most superficial part of the retina?
Dense Neural tissue, then comes the photoreceptors
Describe the path of light and information as light initially hits the retina?
Light goes through layer of nerves to rods and cones -> info goes the opisite way from rods and cones through the nuclei that come together to form the optic nerve
Where are the cell bodies for the axons in the optic nerve?
Retina
Where do some of the optic nerve axons decussate?
Optic chiasm
After chiasm, what happens to the optic nerve?
Optic tract: consists of fibers from crossed and uncrossed axons
Goes to thalamus (lateral geniculate nucleus)
Goes to primary visual cortex in calcarine sulcus (occipital lobe)
Why do some axons cross the brain at the chiasm?
Visual fields: each eye catches bits from both the nasal and temporal sides
At chiasm, fibers sort into left and right visual fields
NASAL fibers cross, TEMPORAL fibers stay
How does the lateral geniculate nucleus (thalamus) process visual inputs?
6 layers takes information from each eye and sends it to the cortex
Each layer gets input from one eye
When processed in the cortex, what part of the cortex represents the inferior visual field?
Superior portion of optic radiations in the cortex
What are two other destinations for visual information?
1: Superior colliculus
2: Hypothalamus: keeps body in seasonal rhythm; body temperature changes
What is a hemianopia?
Loss of half of visual field
Quadrantopia?
Loss of one quarter of a visual field
If damage anterior to chiasm only what would result?
One eye is totally blind
