lecture 2 and 3 duplex retina part 2

Question 1

1 packet of neurotransmitter is called…

Answer 1

a quanta

Question 2

what creates “Dark Light”?

Answer 2

spontaneous quanta packets released, aka neural noise

Question 3

The square root law (aka rose-devry law)explains the exponential curve on a TVI (threshold vs intensity) graph when what happens?

Answer 3

when a stimulus sufficiently exceeds the “dark light” neural noise threshold

Question 4

webers law explains:

Answer 4

where one can distinguish objects from their background (where normal vision happens) also most of the curve lies in this region

Question 5

saturation happens at which point of the TVI curve? satturation happens at ___% of rhodopsin regeneration?

Answer 5

saturation happens after webers law, 10%

Question 6

name the 4 elements of the TVI curve for rods

Answer 6

1) dark light 2) square root law 3) webers law 4)saturation

Question 7

What color tinted glasses would be worst for a rod monochromat?

Answer 7

green, they are most sensitive to green.

Question 8

what are the 2 light adaptation variables?

Answer 8

1) independent variable=background luminance 2) dependent variable=intensity in the test spot

Question 9

to a rod monochromat, light is _____

Answer 9

painful

Question 10

a green stimulus with a red background will ___ cones and _____ rods. You can do this flicker test for a pt when…?

Answer 10

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.

Question 11

a yellow stimulus with a green background will ____ cones and ___ rods. You can do this flicker test for a patient when…?

Answer 11

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.

Question 12

the ____ system is summing up more info to one ganglion cell:

a) photopic
b) scotopic

Answer 12

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.

Question 13

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

Answer 13

a) Ricco’s law=light intensity vs area

Question 14

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

Answer 14

b) Bloch’s law=light intensity vs time

Question 15

according to Ricco’s law, the critical area occurs when…

Answer 15

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)

Question 16

according to Bloch’s law, the critical duration occurs when…

Answer 16

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)

Question 17

The scotopic system has a temporal summation period of ____ms. The photopic system has a temporal summation period of ____ms.

Answer 17

scotopic=100ms. photpic=,10ms

Question 18

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?

Answer 18

none

Question 19

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?

Answer 19

one

Question 20

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?

Answer 20

two

Question 21

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?

Answer 21

one

Question 22

light needs to hit cones at a ____ angle and rods at ___ angle

Answer 22

perpendicular, no particular (lights hitting cones perpendicularly are perceived as brighter than those that hit obliquely.

Question 23

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

Answer 23

b) toward

Question 24

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

Answer 24

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)

Question 25

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

Answer 25

true

Question 26

scotopic webers fraction is ____. photopic webers fraction is _____

Answer 26

scotopic=0.140, photopic=0.015. this means that the contrast sensitivity for scotopic is low and for photopic is high.

Question 27

temporal summation is excellent in the _____ system and poor in the ____ system

Answer 27

scotopic, photopic

Question 28

maximal sensitivity in rods is ____nm and in cones is ___nm

Answer 28

rods=505nm, cones=555nm

Question 29

name the 3 photopic photopigments and their peak wavelengths

Answer 29

cyanolabe=426nm, chlorolabe=530nm, erythrolabe=552nm

Question 30

temporal resolution is poor in the _____ system and excellent in the ____ system

Answer 30

scotopic=poor @20HZ, photopic=excellent @70 HZ