Flashcards in Sensory Systems: Vision Deck (121):
The retina is _ - _ micrometers thick with _ output neurons.
Liquid sphere is surrounded by 3 layers
light sensitive receptors
White fibrous tissue with light-transparent cornea at front
(body of eyeball)
A layer of capillaries and melanin (the light absorbing pigment) behind the retina
Used to adjust lens
Vertebrate eyes are oriented _____ & _____.
The cornea and lens bend the light to achieve a focused image (_____).
changes in refractive power of the lens
The lends is _____ to view distant objects and _____ to view near objects.
_____ keep the lens flat.
Myopia (_% of US pop.) is the result of the cornea being _____ or the eyeball being _____.
(focus point _____ retina)
Hyperopia is known as _____ and results from refractory muscles being _____ or the eyeball being _____.
(focus point _____ retina)
Macula lutea and fovea form the region of _____.
highest visual acuity
optic disk contains _____ photoreceptors.
The _____ is the area of the retina where blood vessels enter and optic fibers leave the eye, creating a _____.
_____ fill in the blind spot of the eye.
The _____ is designed for acuity.
The fovea is a _____ (composed only of _____) around _____ wide.
Macular degeneration affects _____ people in the US.
_____ is a loss of vision in the center of the visual field (the _____) because of damage to the retina.
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).
5 classes of retinal circuitry neurons:
photoreceptors (rods & cones)
Three neuron chain of retinal circuitry:
to bipolar cell
to ganglion cell
Horizontal and amacrine cells enable interactions between _____ and _____ to maintain contrast over different light intensities.
_____ cells form the optic nerve.
Rods and cones have _____ and _____ segments.
In the dark, photoreceptors are _____.
Light stimulation _____ photoreceptors.
Photoreceptor potentials are _____.
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.
_____ is coupled to one of several opsins (for _____)
Light photon converts _____ to _____.
Conversion of retinal actives _____.
Transducin activates _____ (cGMP phosphodiesterase) which _____ levels of cGMP.
The rod system is _____ to light.
the rod system has a _____.
very low spatial resolution
The cone system is _____ sensitive.
the cone system has _____.
high spatial resolution
the cone system is responsible for perception of _____.
_____ vision uses both rods and cones
_____ vision uses no cones.
Cones have a _____ density throughout the retina.
_____ have a shark peak in density at the center of the fovea (_____).
Individual cones _____ in the fovea.
Rods have a _____ density throughout the retina.
Rods have a _____ in density in the fovea.
The _____ contains no capillaries.
Cones adapt more efficiently to _____, while rods saturate _____.
Cones are connected _:_ to bipolar cells.
Rods show _____ at bipolar cells which _____.
increases light sensitivity
_____ vision uses mainly cones.
Humans normally have _____ kinds of cones, resulting in _____ vision
L for _____ respondes to _____ wavelengths (peaking at _____)
M for _____ responds to _____ wavelengths (peaking at _____)
S for _____ responds to _____ wavelengths (_____, 5-10% and absent from _____)
_% of males are colorblind.
_____ results in the loss of long (_____) wavelength perception.
_____ results in loss of medium (_____) wavelength perception.
_____ results in loss of short (_____) wavelength perception
_____ center cells increase firing when luminance increase in their receptive field center.
_____ center cells increase their firing when luminance decreases in their receptive field center.
On- and off-center ganglion cells have selective connections with on and off _____.
Selective responses of on and off bipolar cells are due to their different _____.
_____ on "off"-center cells _____ the bipolar cell.
_____ on "on"-center cells close _____ channels, leading to _____.
Center vs. surround properties of ganglion cells are shaped by _____ from _____.
Antagonism of the surround area arises from _____ from horizontal cells.
Horizontal cells are depolarized by _____ from photoreceptors.
__% of ganglion cells cross at the optic chiasm.
_____ for the optic nerve.
ganglion cell axons
The _____ contains info from both eyes.
The optic tract leads to the _____, _____, _____ and _____.
dorsal lateral geniculate nucleus of thalamus
suprachiasmatic nucleus of hypothalamus
superior colliculus (midbrain)
The _____ is involved with reflex control of pupil and lens.
The _____ regulate constriction of the iris.
Pupilliary reflex should be _____ for both eyes.
Afferents from the pretectum lead to the _____, then the ciliary ganglions.
The crossing of light rays through the lens casuses the images of objects to be _____ and _____ on the retina.
The left half of the visual world is represented in the _____ half of the brain.
Ganglion cells in the _____ of each retina cross in the optic chiasm.
Projections of cells tat lie in the _____ stay on the same side.
The fovea is represented disproportionally large in the _____, while the peripheral stimuli are represented _____.
posterior striate cortex
A lot more ganglion cells are in the _____ to process focused binocular vision.
_____ (top) carries info about the contralateral superior visual field (inferior retinal quadrants)
_____ (bottom) carries info about the the contralateral inferior visual field (superior retinal quadrants).
small visual field deficit
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.
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.
The parvocellular layers are layers _____ of the VC.
The koniocellular layers are patches in layers _____ of the VC.
The _____ is important for spatial resolution.
The _____ is important for high temporal resolution.
The _____ details analysis of shape, size and color of objects.
The _____ transmits some color information.
The _____ evaluates location, speed and direction of a fast-moving object.
Magnocellular ganglion cells have _____ and are _____ (respond only _____).
large receptive fields
Parvocellular ganglion cells transmit _____ and are _____.
Magnocellular ganglion cells transmit _____ than parvocellular ganglion cells.
Cells in the primary visual cortex respond _____ and have a _____.
selectively to oriented edges
_____ respond best to a bar of light with a specific orientation.
Cells in the VC integrate inputs from _____ ganglion/LGN cells.
on- and off-center cells reside in the _____ and _____.
The receptive field of _____ in the VC are built from the fields of several simple 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.
Pyramidal cells in _____ project to subcortical areas, including LGN and superior colliculus.
In the LGN, the inputs from both eyes are separated in _____.
Distinction is maintained is the VC in _____.
ocular dominance columns (layer 4 inputs)
Neurons outside layer 4 integrate inputs from _____.
Blobs are groups of _____ neurons.
Blobs are typically stained with _____.