Perception Discussion #2

Question 1

What is the difference between the synaptic terminal of the rods and cones?

Answer 1

Cone pedicles are larger (flatter) and rod spherules are smaller

Question 2

What are the three lighting conditions from brightest to dimmest?

Answer 2

photopic, mesopic, scotopic

Question 3

What is the duplex?

Answer 3

rods and cones

Question 4

What are the four defining features of cones?

Answer 4

1. photopic vision
2. high light levels
3. high visual acuity
4. color vision

Question 5

What are the four defining features of rods?

Answer 5

1. scotopic vision
2. low light levels
3. low visual acuity
4. no color vision

Question 6

Where is the highest density of cones?

Answer 6

fovea

Question 7

How are foveal cones packed?

Answer 7

regularly, slender, hexagonal

Question 8

What happens to the density of cones as you move eccentrically?

Answer 8

cones decrease, but are present throughout

Question 9

Where is the peak rod density?

Answer 9

20 degrees

Question 10

What are the three types of cones

Answer 10

s, m, l

Question 11

S-cone

Answer 11

most sensitive to short wavelength (blue)

Question 12

M-cone

Answer 12

most sensitive to middle wavelength (green)

Question 13

L-cone

Answer 13

most sensitive to long wavelength (red)

Question 14

Where is the rod free zone?

Answer 14

1 degree eccentricity

Question 15

Where are there no s-cones?

Answer 15

0.35 degrees

Question 16

Where is the highest density of s-cones?

Answer 16

0.35-1 degrees

Question 17

What is the ration of L to M cones?

Answer 17

2:1

Question 18

A wavelength at 440 nm would need to have how much more quanta to be absorbed at the same rate as a 500 nm wavelength?

Answer 18

2x more

Question 19

A wavelength at 560 nm would need to have how much more quanta to be absorbed at the same rate as a 500 nm wavelength?

Answer 19

3x more

Question 20

Which of the following stimuli would yield the highest absorption by a normal
eye?
A. 50 quanta of light of 440 nm
B. 50 quanta of light of 500 nm
C. 100 quanta of light of 559 nm
D. All yield the same absorptions

Answer 20

B. 50 quanta of light of 500 nm

Question 21

Once bleached, does the pigment have any way of distinguishing the properties of the photon?

Answer 21

no, after bleaching the wavelength no longer matters

Question 22

Cyanolabe

Answer 22

blue (419 nm)

Question 23

Chlorolabe

Answer 23

green (530 nm)

Question 24

Erythrolabe

Answer 24

red (558 nm)

Question 25

Spectral Sensitivity Graph

Answer 25

wavelength affects the chance of bleaching a visual pigment

Question 26

Rhodopsin regenerates 50% every?

Answer 26

5 min

Question 27

Cone sensitivity recovers 50% every?

Answer 27

1 min

Question 28

Cone sensitivity recovers 100% within?

Answer 28

6 min

Question 29

How much faster do cones recover than rods?

Answer 29

5x faster

Question 30

A light-adapted individual views side-by-side photopic stimuli of 507 nm and 555 nm. Each stimulus emits the same number of quanta. Which of the following statements regarding the individual’s sensation is CORRECT? A) The 507-nm stimulus would appear brighter than the 555-nm stimulus. B) The 555-nm stimulus would appear brighter than the 507-nm stimulus. C) Both stimuli appear equally bright.

Answer 30

B) The 555-nm stimulus would appear brighter than the 507-nm stimulus.

Question 31

A circular light patch of 507 nm and another patch of 555 nm each bleaches 50 chlorolabe molecules. Which patch appears brighter? A) The patch of 507 nm B) The patch of 555 nm C) Both patches appear equally bright D) Insufficient information to determine the correct answer

Answer 31

C) Both patches appear equally bright

Question 32

Which of the following statements in relation to the Principle of Univariance is INCORRECT? A) Wavelength of the photon affects the chance that the photon will be absorbed. B) If a photopigment has a peak absorption coefficient at 419 nm, then a photon at 450nm absorbed by the photopigment produces a weaker visual sensation than a photon at 419nm absorbed by the same photopigment. C) Once photoisomerized, a photopigment has no means of distinguishing the wavelength of the photon that causes the photoisomerization. D) None of the above

Answer 32

B) If a photopigment has a peak absorption coefficient at 419 nm, then a photon at 450nm absorbed by the photopigment produces a weaker visual sensation than a photon at 419nm absorbed by the same photopigment.

Question 33

The log relative sensitivity at a given wavelength is -1, what is the threshold at this wavelength? A. -1 B. 1 C. 0.1 D. 10 E. None of the above

Answer 33

log sensitivity = -1 sensitivity = 10 -1 threshold = 1/sensitivity threshold = 10

Question 34

You have two containers, one with 100 bleached rhodopsin molecules and the other with 100 bleached erythrolabe molecules. Now you put the two containers in a completely dark room. Which container contains more bleached molecules after being in the dark for 5 min (or both contain the same number of bleached molecules)? A) Both have the same number of bleached molecules due to the principle of univariance B) Rhodopsin has more bleached molecules because it bleaches more easily in the dark C) Erythrolabe has more bleached molecules because cones recover from bleaching more slowly D) Rhodopsin has more bleached molecules because rods recover from bleaching more slowly

Answer 34

D) Rhodopsin has more bleached molecules because rods recover from bleaching more slowly

Question 35

What are the three testing conditions that will change the shape of the dark adaptation curve?

Answer 35

1. retinal eccentricity 2. stimulus size 3. stimulus wavelength

Question 36

Directional Sensitivity

Answer 36

Excitation of cones is strongly dependent upon the direction of light reaching the cones; excitation of rods is nearly independent of the direction of light