15.2

Question 1

define photo-transduction

Answer 1

process by which light energy produces graded receptor potentials

Question 2

what are photoreceptors

Answer 2

modified neurons that have their photoreceptive ends inserted into the pigmented layers of the skin

Question 3

what do photoreceptors contain, what is their function

Answer 3

visual-pigments/photo-pigments that change shape to absorb light

Question 4

why are rods more sensitive than cones

Answer 4

the way they are wired together, for rods many are connected and many cells are attached to a ganglion therefore many rods need to be activated in order to send a signal
as opposed to cones who converge much less than rods ad some have their own ganglion cell so the brain can get a high resolution image

Question 5

what occurs to photoreceptors in dark lighting

Answer 5

photoreceptor cells are slightly depolarized and release an inhibitory neurotransmitter to to the bipolar cell
when the bipolar cell is inhibited it cannot stimulate the ganglion to fire

Question 6

what occurs to photoreceptors in light lighting

Answer 6

light bleaches the pigment and hyper-polarizes the photoreceptor which stops releasing inhibitory neurotransmitters to the bipolar cell causing it to depolarize and send another neurotransmitter to the ganglion to fire it

Question 7

what happens in light adaption

Answer 7

both rods and cones are stimulated and large amounts of pigments are broken down instantaneously producing glare
pupils constrict to reduce the amount of light reaching the retina

Question 8

what happens in dark adaption

Answer 8

bright light has bleached rod pigments so they are turned off and require time to reactivate
pupils dilate to maximize the amount of light reaching the retina
rods accumulate rhodopsin so retinal sensitivity increases

Question 9

what are the light absorbing molecules in photoreceptors

Answer 9

retinal, opsin, rhodopsin (only in rods)

Question 10

what is the path of optic radiations from the ganglions to the primary visual cortex

Answer 10

ganglion, optic nerve, optic chiasma, optic tracts, lateral geniculate body, primary visual cortex

Question 11

briefly explain steps in visual processing

Answer 11

info is condensed by retinal ganglia to look for important things
lateral geniculate nucleus integrates info to begin processing depth perceptions and detailed cone vision is emphasized
primary visual cortex maps the retinal info onto the occipital lobe for further processing

Question 12

how is depth perception created

Answer 12

when visual fields of each eye differ slightly overlap and the visual cortex fuses these images to make a 3D perception