Vision 2, 3 Flashcards
(20 cards)
What do the stacks of discs in the rods and cones do?
Increase probability that any one photoreceptor cell will capture light particles that make it to the retina
What is the photopigment in rods?
rhodopsin
What describes how each sensory receptor cell specializes in just one part of overall range of intensity?
Range fractionation
What is the tendency of rods/cones to adjust to light sensitivity to match current levels of illumination?
Photoreceptor adaptation
What is the optic disc and what does it create?
region of retina without photoreceptors because ganglion cell axons and blood vessels exit eyeball there; create blindspot
What is the point at which parts the two optic nerves cross the midline and project to opposite hemispheres?
optic chasm
What describes the axons of retinal ganglion cells after have passed optic chiasm?
optic tract
What is part of the thalamus, receives info from optic tract and sends to visual areas in occipital cortex?
LGN (lateral geniculate nucleus)
What describes the axons from the LGN that terminate in primary visual areas of occipital cortex?
optic radiations
What happens to photoreceptors in the light?
hyperpolarized –> less NT released
What happens to photoreceptors in the dark?
depolarized –> more NT released
What is the primary visual cortex?
region where most visual info first arrives
The retina projects to brain in topographic fashion. What does this mean?
mapping that preserves point-to-point correspondence between neighboring parts of space
What is a receptive field?
stimulus region + features that affect activity of cell in sensory system
Are on center bipolar cells excited or inhibited by glutamate?
inhibited
What happens when light is presented to on center bipolar cell?
depolarized; inc NT release
What happens when there is NO light for an on-center bipolar cell?
hyperpolarized; dec NT release
What happens when light exposed to on center ganglion cells?
increase firing rates
What happens when light for off center ganglion cells?
decrease firing rates
What is the visual pathway?
retina –> optic nerve –> optic chiasm –> optic tract –> LGN (in thalamus) –> optic radiations –> visual cortex
