Vision Flashcards
What is happening during presbyopia
near point of vision recedes
how is the image on retina in comparision to IRL
inverted and reversed
near response when someone looks at a near object
accommodation
convergence of visual axes
pupils constrict
what is unique about the optic disc
it’s a blind spot
scotoma
a visual field defect
what is responsible for scotopic vision
rods
what is responsible for phototopic vision
cones
what type of vitamin deficiency is associated with night blindness
vit A
what do photosensitive retinal ganglion cells contain
melanopsin
function of melanopsin
measure overall light intensity
what is happening in the dark
channels tha tpermit entry of Na+ and Ca++ are help open by cGMP
what happens when the channels that permit entry of Na+ and Ca++ are open
depolarization, release of neurotranmiter
capture o fa photon activates what
visual pigment (ex - rhodopsin)
when do photoreceptors hyperpolarize
when K+ leaves cell
what is the retina formed by embryologically
evagination of the diencephalon
what makes up the optic nerve and tract
axons of ganglion cells
what are axons in the optic nerve/tract myelinated by
oligodendrocytes
where does preliminary processing of visual information take place
in retina
what are the only things that produce APs in the eye
ganglion cells
what neurotransmitter is released by photoreceptors
glutamate
what is the result of glutamate
it can excite or inhibit bipolar cells
what is the receptive field of a neuron
the area of retina from which the neuron can be influenced
what is the organization of bipolar celll receptive fields
center-surrond
what do bipolar cells response better to
properly position spot of light than to even illumination
Where do retinal fiberss terminate
lateral geniculate of thalamus
suprachiasmatic nucleus of hypothalamus
pretectal nucleus
superior colliculus
what is the function of the retinal cells that terminate in the lateral geniculate of thalamus
relays to visual cortex and recieves input from the visual cortex
where do most retinal cells terminate
LGN
what is the function of retinal cells that terminate in the suprachiasmatic nucleus of hypothalamus
circadian rhythms
what is the function of retinal cells that terminate in the pretectal nucleus
mediate pupillary light reflexes
what is the function of retinal cells that terminate in the superior colliculus
in response to visual stimuli can cause eyes, head, and body to turn towards stimuli
where do ganglion cell axons from the nasal retina cross
at optic chiasm
what causes bitemporal hemianopsia
damage to central part of optic chiasm
what causes homonymous hemianopsia
contralateral to optic tract damage
what causes superior-quadrant anopsia
contralteral to lesion of Meyer’s loop
What is the dorsal pathway responsible for
analysis of motion and relative posititions of object in visual scene
what is ventral stream responsible for
high level form vision and object recognization
prosopagnosia
visually identifying faces
object agnosia
problem identifying objects
cerebral akinetopsia
loss of ability to see motion
short wavelength cone
blue
middle wavelength cone
green
long wavelength cone
red
what is red green color blinded caused by
missing either red or green cone
what do red green color blindness have trouble distinguishing between
green, yellow, orange, red
monochromatopsia
either you have 1 cone or no cones
how do you test for color blindness
ishihara charts
where are the genes for red and green cone pigments
X chromosome
where is teh gene for blue cone pigmenet
chromosome 7
where is the gene for rhodopsin
chromosome 3
stereoscopic vision
requires binocular vision. can make use of binocular disparity for near objects
strabismus
squint or cross eyes
amblyopia
brain ignores the suppressed eye
what happens if you have retinal detachment
vitreous body will seep behind retina, cause further detachment
fovea
highest acuity
where do the major blodo vessels orginate from
optic disk
foveola
center of fovea
what is unique about foveola
avascular
where are cones located
center of fovea
what cones are located in the very center of the fovea
red and green
where is the highest concentration of rods
just outside the fovea
mesopic vision
rods and cones (moonlight)
quadrantopsia
blind in one quadrant
what is quadrantopsia caused by
lesion in meyer’s loop or superior radiations on contraltareal side
what causes hemianopsia with macular sparing
lesion in optic radiations
