1: UII CN II Flashcards
What is the outer most layer of the eye called?
Fibrous tunic
What is the fibrous tunic made of?
Sclera: white part
Cornea: clear part over color
What is the only complete layer of the eye?
The outer fibrous tunic
What is the primary refractory structure of the eye that focuses light on the correct area?
Cornea
What is the middle layer of the eye called?
Vascular tunic
What is the vascular tunic made of?
Ciliary body: ciliary muscle and ciliary organs
Iris: colored part with 2 muscles
Choroid: highly vascular
What is the inner most layer of the eye?
Retina
How many layers does the retina have?
10 layers
What are the 10 layers of the eye from inside to outside?
Internal limiting membrane Nerve fiber layer Ganglion cell layer Inner plexiform layer Inner nuclear layer Outer plexiform layer Outer nuclear layer External limiting layer Photosensitive outer segment Pigmented layer
What is the pigmented layer adjacent to?
The choroid
What is the photosensitive layer made of?
Outer segments of rods and cones
What does the outer nuclear layer contain?
Rod and cone cell bodies
What happens in the outer plexiform layer?
Rods and cones synapse with bipolar cells here
What does the inner nuclear layer contain?
Cell bodies of bipolar cells
What happens in the inner plexiform layer?
Bipolar cells synapse with ganglion cells here
What is contained in the ganglion cell layer?
Ganglion cell bodies
What is the nerve fiber layer made of?
Retinal ganglion cell axons
Are retinal ganglion cell axons myelinated?
No… Unmyelinated
What is the internal limiting membrane?
Glial boundary separating the retina from the vitreous body
What shapes can the distal end of photoreceptors (closest to choroid) be?
Cylindrical (rod) shape
Tapered (cone) shape
How many types of cones are there?
3: red, green, blue
What do the cones recieve?
Color information (can sharpen image)
What do the cones require to function properly
Adequate light
Where are cones more concentrated?
Toward center of retina (fovea)
How is color blindness genetic?
Fewer cones = greater color blindness
Mom carries, 23 chromosome, sex linked
What do rods sense?
Light vs. dark only
Where are rods found?
Periphery of retina al list all rods
Are rods found in the fovea?
NO
How do depolarized photoreceptors relay info?
To bipolar cells in outer plexiform layer
Where are bipolar cell bodies found?
Inner nuclear layer
What type of cells do bipolar cells relay info to?
Ganglion cells
What layer do bipolar cells synapse with ganglion cells
Inner plexiform layer
How do axons from ganglion cells travel?
In optic nerve from eye to optic disc
How does the optic nerve enter the skull?
Through the optic canal, unite to form optic chiasma
Are there photoreceptors on the optic disc?
NO
Are the optic nerve fibers myelinated?
Yes
What cells form the myelin on the optic nerve (CN II)
(Interfasciular) olgiodendrocytes
Which fibers of CN II cross in the optic chiasma
Medial side of retina
Which fibers of CN II do not cross in the optic chiasma?
The lateral retina fibers
After CN II fibers split and cross in the optic chiasma what is formed?
Optic tracts
How do the optic tracts travel?
Around the cerebral peduncles, fibers synapse on 1/3 nuclei of termination
What are the three nuclei of termination that the optic tracts can synapse on?
Lateral geniculate body, superior colliculus, tectospinal tract
How many layers is the eye made of?
Three layers
How do the majority of CN II fibers travel?
Synapse in the lateral geniculate body, relayed to the cerebral cortex in the occipital lobe (BMA 17)
How are the superior colliculus and tectospinal tract related?
Fibers synapse in the superior colliculus and info is relayed to the tectospinal tract
What two muscles are influenced by the tectospinal tract?
Trapezius and sternocleidomastoid
What is observed with optic nerve lesion?
Lose sight in the eye the lesion is on, lose depth perception
What is observed with a lesion in the optic chiasma?
Tunnel vision, loss of peripheral vision
What is observed with a lesion in the optic tract?
Lose 1/2 of vision on the opposite side of the lesion
What is the direct and consensual light reflexes?
Side with light constricts a lot: DIRECT
Side with out light slightly constricts: INDIRECT
What is the accommodation reflex?
Near/far
Increase in convexity = closer focus
What is the corneal reflex?
Touch cornea: person blinks and pulls away
What is the convergence reflex?
Look at nose
What are you testing with cranial nerve II reflex tests?
AFFERENT components only (CN II purely sensory)
Response requires motor function through different cranial nerve
