Vision I-II Flashcards
name the major structures that light passes through before reaching the retina
cornea, anterior chamber, lens, vitreous body
important structure in the eye for color vision
fovea of macula
how is the light signal sent to the brain?
once light hits retina, it initiates a biochemical series of events in photoreceptors, which are sent to the brain via the optic nerve
what produces aqueous humor? b lockage of aqueous flow causes what disease?
ciliary body
glaucoma
the path of aqueous humor
produced by ciliary body, flows from posterior chamber to anterior chamber and to the Canal of Schlemm
in glaucoma, which part of the visual field is impaired?
peripheral vision
the meninges around the eye from outermost to innermost
sclera (dura), choroid (pia + arachnoid), trabecular meshwork, granulation (arachnoid)
what happens if there is a blockage of the arachnoid granulation?
open/wide-angle glaucoma
what is accommodation?
changing the curvature of the lens to bring an image to focus on the retina
is the lens fatter or thinner when looking at something close?
fatter
name the muscle that helps to change lens curvature?
ciliary body
name the ligament that helps to change lens curvature?
zonule of Zinn
name a disease condition when a person has trouble focusing on an object because of a lens problem
astigmatism
farsightedness due to the lens losing elasticity during the aging process
presbyopia
what type of lens corrects for presbyopia?
convex
occurs when the lens loses opacity
cataract
difference in vision of px with glaucoma vs cataract
cataract makes whole visual field blurry, not just periphery like glaucoma does
is myopia determined by genetics or can it be caused by the environment?
mainly genetic but may also have environmental factor role
name for normal eye; name for when eyeball is to short; name for when eyeball is too long
emmetropia; hyperopia; myopia
eyesight problem caused by curvature of the cornea or the lens
astigmatism
can a person have myopia with astigmatism?
yes
layer of the retina where the photoreceptor cell bodies are
external nucleus layer
cells in this layer of the retina play important roles in relay/modulation of signals
internal nucleus layer
axons of these cells become the optic nerve
ganglion cell layer (of the retina)
order of layers of the retina from outermost to innermost
external nucleus layer, internal nucleus layer, ganglion cell layer
4 major cell types in the internal nuclear layer
Muller supporting cell (major glia), horizontal cell, bipolar neuron, amacrine cell
these cells in the internal nuclear layer modulate signals sent out by photoreceptors
horizontal cell
these cells in the internal nuclear layer relay signals between the cell layers
bipolar neuron
these cells of the internal nuclear layer modulate function of ganglion cells
amacrine cell
what is the optic nerve composed of?
axons from ganglion cells collected into a bundle become the optic nerve
*the area where the ganglion cell axons exit the eyeball
papilla (optic disc)
why is the fovea of the macula an area with high visual acuity?
it has high number of ganglion cells and cones
what is the optic disc a collection of?
ganglion cells ready to leave the eyeball; no photoreceptors, so no image happens when light falls onto this spot (blind spot)
where is the macula of the eye?
lateral to the optic disc in an avascular area
why is the macula in a region with no blood vessels?
helps macula acquire its high visual acuity because light is not blocked by blood vessels
what is the center of the macula? what is found here?
fovea. cone photoreceptors
the landmark used to define the various parts of the retina; the various parts?
the macula
superior retina, inferior retina, nasal retina, temporal retina
a disease that affects the macula
diabetes; Stargardt disease
leading cause of blindness in the elderly
macular degeneration
what part of the visual field is lost in patients with macular degeneration?
central vision
which layer of retina cells is affected by macular degeneration?
ganglion cell layer
causes of abnormal appearance of the optic disc
when ICP is high, CSF presses on the optic nerve
high ICP can cause abnormal optic disc appearance known as…/ what are possible causes of high ICP?
papilledema (distorted blood vessels, optic disc loses its fine edges and swells)
hematoma, hydrocephalus, brain bleeds
why can it cause problems if you do lumbar puncture on a patient with papilledema?
risk for tentorial herniation, subsequent death via cerebral herniation
where rods are concentrated/ where cones are concentrated
rods- retina
cones- fovea
when light hits the retina and causes a series of biochemical events in the outer segment of the photoreceptor, it is a very similar process to…. (name steps)
GPCR (light is stimulus, undergoes conformational change, binds GTP, decreases 2nd messenger, closes a channel in response)
when light hits a photoreceptor, it decreases the release of….
glutamate (an excitatory NT)
which of the following is a G-protein: rhodopsin? transducing? PDE?
rhodopsin
what does PDE stand for? what does it do?
phosphodiesterase: cleaves cGMP
which molecule undergoes conformational change?
rhodopsin
which molecule binds GTP?
transducin
which molecule activity is increased?
PDE
which molecule levels decrease due to PDE activity?
cGMP
what happens when cGMP levels are decreased?
Na+ channels close, hyperpolarization, reduce Glu release
what gene is mutated in retinitis pigmentosa?
mutation of rhodopsin gene
rods are important for ______; cones are important for ______.
rods- night vision, peripheral vision
cones- day-light vision, central vision
so, a px with retinitis pigmentosa has severe degeneration of rods or cones? what are the deficits?
RODS- impaired night vision, impaired peripheral vision
retinitis pigmentosa is inherited.
color blindness is a problem with rods, cones, or ganglion cells?
cones
this deficiency can cause impaired night vision because its needed for biochemical reactions in the photoreceptor
vitamin A
night blindness can also be caused by this genetic disease
retinitis pigmentosa
is thalamus involved in vision? what thalamic structures are in the visual pathway?
yes- lateral geniculate nucleus
something on the right visual field projects to which visual cortex?
left visual cortex
the image on the retina compared to the image in the visual field is..
reversed and upside down.
what happens at the optic chiasm?
the left and right visual field fibers cross here
right visual field goes to ____ retina to ____ lateral geniculate nucleus
left retina, left LGN
visual info sent to LGN for the purpose of..
patterns
visual info sent to superior colliculus for purpose of..
spatial/head movements
visual info sent to pretectal nucleus for purpose of..
light reflex
visual info sent to suprachiasmatic nucleus of hypothalamus for purpose of..
circadian rhythm
where is the LGN located? where is the superior colliculus located? what connects the two?
diencephalon
midbrain
superior brachium
the pretectal area regulates the
pupillary light reflex
what NT is used to communicate between the edinger-westphal nucleus and the ciliary ganglion?
acetylcholine
pupillary light reflex pathway: retina, optic nerve, optic chiasm, optic tract, …..
brachium of SC, pretectal area, ew NUCLEUS, CILIARY GNANGLION, SHORT CILIARY NERVE, CONSTRICTOR MUSCLE, PUPILLARY CONSTRICTION
Which structure connects the pretectal areas on the left and right sides?
posterior commissure
pupillary light reflex: need info to be sent to visual cortex?
no, but we send a lot of info here via the LGN
what is optic radiation?
signals sent from LGN to visual cortex
where in the brain is info sent to make sense of what is being looked at?
area 17 first, then area 18+19
Brodmann defined the areas of the brain based on..?
histology
does the primary visual cortex control eye movement?
no, the frontal lobe does. the primary visual cortex is in the occipital lobe (areas 17, 18+19)
the areas of the parietal lobe, and the name for them
3, 1, 2
primary sensory cortex
areas of the brain for Broca’s area
44, 45 (motor aspects of speech)
where is visual info sent from the eye for initial processing?
sent to LGN and then to area 17
which sulcus is in the middle of area 17?
calcarine sulcus
the structure above the calcarine sulcus? the structure below the calcarine sulcus?
above-cuneus
below- lingual gyrus
visual info from the macula of the retina enters which part of the visual cortex?
the posterior part (of lingual gyrus and cuneus)
visual info from the periphery of the retina enters which part of the visual cortex?
anterior part
instance when pupillary dilation reflex is iniatiated by info processing in the visual cortex
sight of something frightening like a rat can activate sympathetics and cause pupillary dilation reflex
the major NT that activates neurons in the superior cervical ganglion?
acetylcholine (from pre-ganglionics)
what is the major NT released by superior cervical ganglion neurons to activate post ganglionic neuron?
norepinephrine
describe the pathway of the pupillary light reflex being initiated via sympathetics due to visual stimulation
posterior diencephalon neuron descends down medulla, into thoracic level 1 where it synapses in lateral horn , exits through ventral root at pregang sympathetic fiber, to cervicothoracic ganglion, ascends to superior cervical ganglion and synapses, continues around carotid plexus as post ganglionic fiber in NASOCILIARY AND LONG CILIARY NERVES
a damage of this sympathetic pathway to initiate pupillary dilation reflex due to a visual stimulus would cause ____ syndrome
Horner’s
PAM is horny (horners) what muscles/NTs are affected by P.A.M.?
P= Ptosis= Muller’s muscle affected
A= anhidrosis = acetylcholine (pre ggl) or NE (post ggl) are affected
M=miosis (pupil constriction)= acetylcholine (parasympathetics) becomes dominant
ciliary muscle contraction: fattened lens or flattened lens?
fattened lens (short sighted)
visual field defects: recorded from whose perspective?
patients perspective. defects may have nothing to do with the eye.
blindless term
anopia, anopsia
monocular anopia can be caused by.
optic nerve optic neuritis of one optic nerve, trauma to left eye ball– blocks info from left eye
a pituitary tumor causes what type of anopia?
bitemporal hemianopia
a pituitary tumor presses on..
optic nerve chiasm
a pituitary tumor causing bitemporal hemianopia will salvage the nasal visual fields because…
the visual info from nasal fields does not have to cross the optic chiasm, they just go back to the ipsilateral optic tract
damage to the left optic tract would cause..
right homonymous hemianopia (blind in right temporal vision, and also left nasal field blindness)
T/F: lesions that are posterior to the optic chiasm always cause “homonymous” problems
false could affect 1 eye’s visual field but usually affects both
optic radiation lesion on the left side of the occipital lobe can cause..
right homonymous hemianopia (possibly with macula sparing)
possible reasons for macular sparing
overlapping blood supply, macula has large representation in the occipital lobe
blood supply of occipital lobe
posterior cerebral artery and middle cerebral artery
what optic radiation fibers do after leaving the lateral geniculate nucleus
split into 2 bundles, 1 ventral and 1 dorsal
Meyers loop is a part of which optic radiation bundle in the temporal lobe?
ventral optic radiation
fibers representing inferior retinal quadrants are from which part of the visual field?
superior visual field
so a lesion of Meyer’s loop on the right side of the brain, the visual field defect will be on the..
left side//superior area the visual field (Meyer’s loop is part of inferior fibers)
where is a lesion that causes righ thomonymous superior quadrantanopia?
majority of left optic radiation behind LGN
