lecture 2 and 3 duplex retina part 2 Flashcards
1 packet of neurotransmitter is called…
a quanta
what creates “Dark Light”?
spontaneous quanta packets released, aka neural noise
The square root law (aka rose-devry law)explains the exponential curve on a TVI (threshold vs intensity) graph when what happens?
when a stimulus sufficiently exceeds the “dark light” neural noise threshold
webers law explains:
where one can distinguish objects from their background (where normal vision happens) also most of the curve lies in this region
saturation happens at which point of the TVI curve? satturation happens at ___% of rhodopsin regeneration?
saturation happens after webers law, 10%
name the 4 elements of the TVI curve for rods
1) dark light 2) square root law 3) webers law 4)saturation
What color tinted glasses would be worst for a rod monochromat?
green, they are most sensitive to green.
what are the 2 light adaptation variables?
1) independent variable=background luminance 2) dependent variable=intensity in the test spot
to a rod monochromat, light is _____
painful
a green stimulus with a red background will ___ cones and _____ rods. You can do this flicker test for a pt when…?
supress, activate. If you want to see what the rods are doing, you can selectively activate them, good for doing increment threshold experiments on a rod monochromat since a rod monochromat has no functioning cones, only rods.
a yellow stimulus with a green background will ____ cones and ___ rods. You can do this flicker test for a patient when…?
stimulate, stimulate. patient complains it takes too long to recover after looking at a bright light. For example, when driving at night they look at headlights and it takes 5 minutes to regain their normal sight.
the ____ system is summing up more info to one ganglion cell:
a) photopic
b) scotopic
b) scotopic-there are many rods to 1 ganglion cell (20:1), whereas in the photopic system there is about 5:1 cones to ganglion cells.
Which law describes: As area decreases, light intensity must increase to maintain threshold (a gradient with a slope of -1):
a) Ricco’s law
b) Bloch’s law
c) Stile’s law
d) Crawford’s law
a) Ricco’s law=light intensity vs area
Which law describes: As time decreases, light intensity must increase to maintain threshold (a gradient with a slope of -1):
a) Ricco’s law
b) Bloch’s law
c) Stile’s law
d) Crawford’s law
b) Bloch’s law=light intensity vs time
according to Ricco’s law, the critical area occurs when…
light intensity vs area plateau’s. no matter how much the area is increased, there is no greater response. (threshold for seeing light at a certain intensity and area)
according to Bloch’s law, the critical duration occurs when…
light intensity vs time plateau’s.no matter how much the time interval is increased, there is no greater response. (threshold for seeing light at a certain intensity and time interval)
The scotopic system has a temporal summation period of ____ms. The photopic system has a temporal summation period of ____ms.
scotopic=100ms. photpic=,10ms
if 2 flashes are shown that outstretch the summation period of either the photopic or scotopic system and are also below the intensity threshold, how many flashes are seen?
none
if 2 flashes are shown that are within the summation period of either the photopic or scotopic system and are also below the intensity threshold, how many flashes are seen?
one
if 2 flashes are shown that outstretch the summation period of either the photopic or scotopic system and are also above the intensity threshold, how many flashes are seen?
two
if 2 flashes are shown that are within the summation period of either the photopic or scotopic system and are also above the intensity threshold, how many flashes are seen?
one
light needs to hit cones at a ____ angle and rods at ___ angle
perpendicular, no particular (lights hitting cones perpendicularly are perceived as brighter than those that hit obliquely.
The Stiles-Crawford effect: cones point ____ light in decentered pupils
a) away from
b) toward
c) at an angle equal yet opposite of the incident angle of the light that enters the pupil
b) toward
a patient with 2 pupils would have ___ photopic vision and ____ scotopic vision:
a) enhanced, reduced
b) reduced, enhanced
c) reduced, reduced
d) slightly enhance, enhanced
b) reduced photopic and enhanced scotopic. In light, patient would see dimmer than normal due to more oblique rays hitting the cones however in dark condition more rods would be activated and the patient would see slightly better in the dark. (stiles-crawford effect has more impact on photopic system)
True or false: Bloch’s law tells us that the most flashes we can see in the scotopic system is 1 in 100ms, 2 in 200ms, 5 in 500ms, etc
true
scotopic webers fraction is ____. photopic webers fraction is _____
scotopic=0.140, photopic=0.015. this means that the contrast sensitivity for scotopic is low and for photopic is high.
temporal summation is excellent in the _____ system and poor in the ____ system
scotopic, photopic
maximal sensitivity in rods is ____nm and in cones is ___nm
rods=505nm, cones=555nm
name the 3 photopic photopigments and their peak wavelengths
cyanolabe=426nm, chlorolabe=530nm, erythrolabe=552nm
temporal resolution is poor in the _____ system and excellent in the ____ system
scotopic=poor @20HZ, photopic=excellent @70 HZ
