Sensory Systems: Vision Flashcards
The retina is _ - _ micrometers thick with _ output neurons.
100
200
3 million
Liquid sphere is surrounded by 3 layers
Retina
Uveal layer
Sclera
Retina
light sensitive receptors
Uveal layer
Choroid
Ciliary body
Iris
Sclera
White fibrous tissue with light-transparent cornea at front
body of eyeball
Choroid
A layer of capillaries and melanin (the light absorbing pigment) behind the retina
Ciliary muscle
Used to adjust lens
Vertebrate eyes are oriented _____ & _____.
upside down
curved
The cornea and lens bend the light to achieve a focused image (_____).
refraction
Accommodation
changes in refractive power of the lens
The lends is _____ to view distant objects and _____ to view near objects.
flat
round
_____ keep the lens flat.
Zonule fibers
Myopia (_% of US pop.) is the result of the cornea being _____ or the eyeball being _____.
(focus point _____ retina)
nearsighted 50 too curved too long before
Hyperopia is known as _____ and results from refractory muscles being _____ or the eyeball being _____.
(focus point _____ retina)
farsighted
too weak
too short
behind
Macula lutea and fovea form the region of _____.
highest visual acuity
optic disk contains _____ photoreceptors.
no
The _____ is the area of the retina where blood vessels enter and optic fibers leave the eye, creating a _____.
optic disk
blind spot
_____ fill in the blind spot of the eye.
Cortical mechanisms
The _____ is designed for acuity.
fovea
The fovea is a _____ (composed only of _____) around _____ wide.
rod-free area
cones
200 micrometers
Macular degeneration affects _____ people in the US.
6 million
_____ is a loss of vision in the center of the visual field (the _____) because of damage to the retina.
Macular degeneration
Macular degeneration ("dry" form)
(_% of all cases)Debris between the retina and the choroid results in disappearance of the retinal pigment epithelium and loss of photoreceptors.
Macular degeneration (“wet” form)
Blood vessels grow from the choroid and the retina can also become detached.
Macular degeneration is treated with _____ and _____ to stop the growth of blood vessels (_____ form).
laser coagulation
medication
wet
5 classes of retinal circuitry neurons:
photoreceptors (rods & cones) bipolar cells horizontal cells amacrine cells ganglion cells
Three neuron chain of retinal circuitry:
photoreceptor
to bipolar cell
to ganglion cell
Horizontal and amacrine cells enable interactions between _____ and _____ to maintain contrast over different light intensities.
photoreceptors
bipolar cells
_____ cells form the optic nerve.
Ganglion
Rods and cones have _____ and _____ segments.
inner
outer
In the dark, photoreceptors are _____.
depolarized
Light stimulation _____ photoreceptors.
hyperpolarizes
Photoreceptor potentials are _____.
graded
The outer segment of photoreceptors is responsible for _____.
depolarization (Na+ and Ca++ influx)
The inner segment of photoreceptors is responsible for _____.
hyperpolarization (K+ outflux)
Light reduces _____ and _____ channels.
cGMP levels
closes
_____ is coupled to one of several opsins (for _____)
Retinal
different wavelengths
Light photon converts _____ to _____.
11-cis retinal
all-trans retina
Conversion of retinal actives _____.
transducin
Transducin activates _____ (cGMP phosphodiesterase) which _____ levels of cGMP.
PDE
reduces
The rod system is _____ to light.
extremely sensitive
the rod system has a _____.
very low spatial resolution
The cone system is _____ sensitive.
low-light
the cone system has _____.
high spatial resolution
the cone system is responsible for perception of _____.
color
_____ vision uses both rods and cones
Mesopic
_____ vision uses no cones.
Scotopic
Cones have a _____ density throughout the retina.
low
_____ have a shark peak in density at the center of the fovea (_____).
Cones
foveola
Individual cones _____ in the fovea.
become smaller
Rods have a _____ density throughout the retina.
high
Rods have a _____ in density in the fovea.
sharp drop
The _____ contains no capillaries.
avascular zone
Cones adapt more efficiently to _____, while rods saturate _____.
constant illumination
quickly
Cones are connected : to bipolar cells.
1
1
Rods show _____ at bipolar cells which _____.
convergence
increases light sensitivity
_____ vision uses mainly cones.
Photopic
Humans normally have _____ kinds of cones, resulting in _____ vision
3
trichromatic
L for _____ respondes to _____ wavelengths (peaking at _____)
long
long
red
M for _____ responds to _____ wavelengths (peaking at _____)
medium
medium
green
S for _____ responds to _____ wavelengths (_____, 5-10% and absent from _____)
short
short
blue
fovea
_% of males are colorblind.
8
_____ results in the loss of long (_____) wavelength perception.
Protanopia
_____ results in loss of medium (_____) wavelength perception.
Deuteranopia
_____ results in loss of short (_____) wavelength perception
Tritanopia
blue-yellow
_____ center cells increase firing when luminance increase in their receptive field center.
on-center
_____ center cells increase their firing when luminance decreases in their receptive field center.
off-center
On- and off-center ganglion cells have selective connections with on and off _____.
bipolar cells
Selective responses of on and off bipolar cells are due to their different _____.
glutamate receptors
_____ on “off”-center cells _____ the bipolar cell.
AMPA receptors
depolarize
_____ on “on”-center cells close _____ channels, leading to _____.
mGluR6
Na+
hyperpolarization
Center vs. surround properties of ganglion cells are shaped by _____ from _____.
lateral inhibition
interneurons
Antagonism of the surround area arises from _____ from horizontal cells.
lateral connections
Horizontal cells are depolarized by _____ from photoreceptors.
glutamate
__% of ganglion cells cross at the optic chiasm.
60
_____ for the optic nerve.
ganglion cell axons
The _____ contains info from both eyes.
optic tract
The optic tract leads to the _____, _____, _____ and _____.
dorsal lateral geniculate nucleus of thalamus
suprachiasmatic nucleus of hypothalamus
pretectum
superior colliculus (midbrain)
The _____ is involved with reflex control of pupil and lens.
pretectum
The _____ regulate constriction of the iris.
ciliary ganglions
Pupilliary reflex should be _____ for both eyes.
identical
Afferents from the pretectum lead to the _____, then the ciliary ganglions.
Edinger-westphal nucleus
The crossing of light rays through the lens casuses the images of objects to be _____ and _____ on the retina.
inverted
left-right reversed
The left half of the visual world is represented in the _____ half of the brain.
right
Ganglion cells in the _____ of each retina cross in the optic chiasm.
nasal division
Projections of cells tat lie in the _____ stay on the same side.
temporal division
The fovea is represented disproportionally large in the _____, while the peripheral stimuli are represented _____.
posterior striate cortex
further anterior
A lot more ganglion cells are in the _____ to process focused binocular vision.
macula
_____ (top) carries info about the contralateral superior visual field (inferior retinal quadrants)
Meyer’s loop
_____ (bottom) carries info about the the contralateral inferior visual field (superior retinal quadrants).
Baum’s loop
Scotomas
small visual field deficit
Anopsias
large visual field deficits
Inputs from the right hemi-retina of each eye project to different layers of the _____.
right lateral geniculate nucleus (LGN) of thalamus
The LGN is comprised of the _____, _____ and _____ layers.
magnocellular
koniocellular
parvocellular
Mangocellular layers are _____.
ventral layers (1-2), large neurons
Parvocellular layers are _____.
dorsal layers (3-6), small neurons
The magnocellular layers are layers _____ of the VC.
4C-alpha
The parvocellular layers are layers _____ of the VC.
4C-beta
The koniocellular layers are patches in layers _____ of the VC.
2/3
The _____ is important for spatial resolution.
parvocellular pathway
The _____ is important for high temporal resolution.
mangocellular pathway
The _____ details analysis of shape, size and color of objects.
parvocellular pathway
The _____ transmits some color information.
koniocellular pathway
The _____ evaluates location, speed and direction of a fast-moving object.
magnocellular pathway
Magnocellular ganglion cells have _____ and are _____ (respond only _____).
large receptive fields
fast
transiently
Parvocellular ganglion cells transmit _____ and are _____.
color information
persistently active
Magnocellular ganglion cells transmit _____ than parvocellular ganglion cells.
faster
Cells in the primary visual cortex respond _____ and have a _____.
selectively to oriented edges
preferred direction
_____ respond best to a bar of light with a specific orientation.
simple cells
Cells in the VC integrate inputs from _____ ganglion/LGN cells.
several
on- and off-center cells reside in the _____ and _____.
retina
LGN
The receptive field of _____ in the VC are built from the fields of several simple cells.
complex cells
Axons from LGN terminate primarily on spiny stellate cells of _____.
layer 4C (afferents to VC)
Pyramidal cells in _____ project to higher order (visual) cortices.
layers 2/3
Pyramidal cells in _____ project to subcortical areas, including LGN and superior colliculus.
layers 5/6
In the LGN, the inputs from both eyes are separated in _____.
different layers
Distinction is maintained is the VC in _____.
ocular dominance columns (layer 4 inputs)
Neurons outside layer 4 integrate inputs from _____.
both eyes
Blobs are groups of _____ neurons.
color-sensitive
Blobs are typically stained with _____.
cytochrome oxidase
Interblobs receive the same input but are sensitive to _____.
orientation
