Unit 1 - C.N. II - Optic Nerve Flashcards
Outermost layer of the eye
Fibrous tunic
The fibrous tunic consists of what two things?
Sclera and cornea
What is the only part that goes completely around the eye?
sclera
What is the middle layer of the eye?
Vascular tunic
What are the three parts of the vascular tunic?
Ciliary body, Iris, choroid
Why is the vascular tunic not complete?
Because of the Iris - has a pupil
What is the innermost layer of the eye?
The retina
What layer is adjacent to the choroid?
Pigmented layer (cementing layer)
What is the next layer inward after the pigmented layer?
Photosensitive outer segments of rods and cones
What layer covers the rods and cones?
External limiting membrane
What layer contains the cell bodies of rods and cones?
Outer nuclear layer
Rods and cones synapse with bipolar cells here.
Outer Plexiform layer
Layer that contains the cell bodies of bipolar cells?
Inner nuclear layer
Layer where bipolar cells synapse with ganglion cells?
Inner plexiform layer
Layer of ganglion cell bodies?
Ganglion cell layer
Are retinal ganglion cell axons myelinated?
no
Layer containing the ganglion cell bodies?
Ganglion cell layer
Layer containing the retinal ganglion cell axons?
Nerve fiber layer
A glial boundary separating the retina from the vitreous body?
Internal limiting membrane
Name the layers from 1 -10 (choroid to vitreous body)
Pigmented layer Photosensitive outer segments of rods and cones External limiting membrane Outer nuclear layer Outer plexiform layer Inner nuclear layer Inner plexiform layer Ganglion cell layer Nerve Fiber layer Internal limiting membrane
What is the distal end of the photoreceptor called?
The outer segment
The outer segment of the photoreceptor is closes to what?
The choroid
The outer segment of the photoreceptor has two shapes. What are they?
Cylindrical (rod shaped) and tapered (cone shaped)
There are three types of cones that receive information, they are?
Red, green, and blue
What is required for the cones to work?
Light
Where are the cones more concentrated?
Toward center of the retina (fovea)
What are the only thing rods sense?
Light and dark (only shades of grey)
Are there rods in the fovea?
NO
What is the periphery of the retina completely composed of?
rods
When depolarized, photoreceptors relay information to bipolar cells by synapsing in what layer?
Outer plexiform layer
Axons from ganglion cells are coveted in the nerve fiber layer toward the _____.
Optic disc
Where does the optic nerve attach to the eye?
Optic disc
Where are the axons from nerve fiber layer carried in outside of the eye?
In the optic nerve
Are ganglionic cells myelinated?
no
When do the axons of the ganglion cells become myelinated?
When they leave the eye
The optic nerve enters the skull through the _____ and unites to form the ______.
Optic canal
Optic chiasma
Are optic nerve fibers myelinated?
yes
What cells form the myelination of the optic nerve?
(interfasicular) oligodendrocytes
In the optic chiasma which fibers cross?
Fibers from the medial (nasal) side of the retina
In the optic chiasma which fibers do not cross?
Fibers from the lateral (peripheral) side of the retina
The optic tract travels around what?
Cerebral peduncles
After traveling around the cerebral peduncles, the optic tract fibers synapse which three nuclei of termination?
Lateral geniculate body
Superior colliculus
pretectal nucleus of the midbrain
The majority of optic tract fibers synapse in which N.O.T.?
Lateral geniculate body
After synapsing in the lateral geniculate body, where is the information relayed?
The cerebral cortex in the occipital lobe (B.A. 17)
After synapsing in the superior colliculus, where is the information relayed to?
The tectospinal tract
What are the two muscles influenced by the tectospinal tract?
trapezius
sternocleidomastiod
Fibers from rods/cones to SCM/trapezius arrive via what nerve?
C.N. XI - accessory nerve
The tectospinal tract goes down to what level of the spine?
C4
How many neurons are in the optic pathway?
3 - photoreceptor to bipolar to ganglionic
Colorblindness is most common in _____?
males
Most colorblindness is sex-linked on which chromosome?
X
Optic nerve lesion causes?
Loss of depth perception, decrease in size of visual field (
Decussating fibers of the optic chiasma causes?
tunnel vision, lose peripheral vision
What passes through the optic chiasma that can lead to tunnel vision?
infundibular stalk, so a pituitary lesion can cause
Lesion of the optic tract causes?
One side of vision is gone (opposite side of lesion)
Which 3 visual reflexes test C.N. II - sensory/afferent only?
Direct and consensual reflexes
Accommodation reflex
Corneal reflex
How do you test direct and consensual reflexes?
Shine light in L eye and swing light back and forth.
Direct = L pupil constricts
Consensual = R pupil slightly constricts
What is the accommodation reflex?
Changing the shape of the lens to focus near and far
How do you test convergence?
Use a pen and move pen towards patient’s nose. Eyes should coverage and track in.
