Deck 22: Transduction and Transmission in the Retina

Question 1

What is one reason we cannot clearly read text that we are not focused on?

A) Cones, which contribute to color vision, are more concentrated in the fovea.
B) Light is not projected fully on the periphery of vision, making it difficult to see text.
C) Photoreceptor density falls off sharply in the periphery of vision, making it difficult to distinguish patterns like text.
D) Rods, which enable us to distinguish patterns of text, are highly concentrated in the fovea.
E) Our perception of peripheral images is not as detailed as foveal images because of higher-order processing.

Answer 1

C

Question 2

Density and connectivity of rods is highest in the periphery, just outside of the fovea. What is one consequence of this configuration?

A) Color vision is most clear in the periphery.
B) Vision in dim light is most clear in the periphery.
C) Vision in dim light is most clear in the fovea.
D) Color vision is most clear in the fovea.
E) Color vision is just as clear in the fovea as in the periphery.

Answer 2

B

Question 3

Which type of cell is chiefly responsible for responding to illumination, without consideration for color?

A) Rods
B) Amacrine cells
C) Bipolar cells
D) Cones
E) Horizontal cells

Answer 3

A

Question 4

Amacrine type II (AII) cells primarily synapse with

A) D bipolar cells.
B) H bipolar cells.
C) ganglion cells.
D) D bipolar cells and H bipolar cells.
E) horizontal cells.

Question 5

Photoreceptors, horizontal, and bipolar cells generate _______ ganglion cells and amacrine cells generate _______.

A) action potentials; action potentials
B) graded local potentials; graded local potentials
C) action potentials; graded local potentials
D) graded local potentials; calcium cascades
E) graded local potentials; action potentials

Question 6

_______ are found in the _______ layer of the retina.

A) Ganglion cells, deepest
B) Bipolar cells, deepest
C) Horizontal cells, middle
D) Amacrine cells, outermost
E) Photoreceptors, deepest

Question 7

_______ cones generally outnumber _______ cones in humans.

A) Long (L) and short (S); medium (M)
B) Long (L); medium (M) and short (S)
C) Medium and short (S); long (L)
D) Medium; long (L) and short (S)
E) Long (L) and medium (M); short (S)

Question 8

The names for the different types of cones (long, short, and medium) refer to

A) the wavelengths of light they absorb.
B) the length of their bodies.
C) the time it takes for them to fire action potentials.
D) the length of their axons.
E) how long they live.

Question 9

Pigments that are responsive to light are found in the _______ of the photoreceptor.

A) dendrites
B) outer segment
C) inner segment
D) synaptic terminal
E) axon

Question 10

Pigments in cones are found _______ the cell membrane and pigments in rods are found _______ the cell membrane.

A) inside; continuous with
B) continuous with; outside
C) inside; inside
D) continuous with; inside
E) outside; continuous with

Question 11

While stargazing one night, you notice that a particular star appears to vanish whenever you move your eyes to a specific part of the sky. Why might this occur?

A) The light of the star is too dim to be detected by certain rods.
B) The light of the star is being projected onto the fovea, where there are too few rods to detect it.
C) The light of the star is being projected onto the periphery, where there are too few cones to detect it.
D) The light of the star is producing varying quanta of photons, which rods cannot reliably detect.
E) The light of the star is too dim to be detected by certain cones.

Question 12

Under certain conditions, visual stimuli, even in bright light, can seem to disappear from our perception. What is one potential cause of this phenomenon in healthy human eyes?

A) Light can be completely blocked from reaching the retina if pupils constrict too far.
B) Corneas may reflect only part of an image to the retina.
C) There are no photoreceptors at the location where optic nerve fibers leave the eye, which causes a blind spot.
D) In certain parts of the retina, photoreceptors may "cancel" each other out so no signals are sent.
E) This phenomenon is a product of higher-order perception and does not involve the retina.

Question 13

You train a macaque to respond to the presentation of a red circle by ringing a bell, after which she is presented with a treat. One evening, the power goes out, but you decide to continue your training with the macaque using the waning sunlight. To your surprise, the macaque seems to be unable to respond properly to the red circle after about an hour. What is one explanation for the macaque's regression?

A) The repeated training has made the red stimulus too ambiguous to the macaque's perception.
B) The waning light has made the red stimulus appear brighter due to increased cone activation.
C) The waning light has made the red stimulus less prominent due to increased rod activation.
D) The waning light has made the red stimulus less prominent due to decreased cone activation.
E) The repeated training has made the red stimulus appear green to the macaque.

Question 14

Retinal plays a key role in preventing rhodopsin from

A) undergoing thermal isomerization.
B) responding too readily to photons.
C) undergoing isomerization in the presence of one photon of light.
D) changing structure due to being exposed to light.
E) opening calcium channels in the photoreceptor.

Question 15

During transduction, the α subunit of the associated G protein binds to which part of the photoreceptor?

A) Chromosphere
B) Amino terminus
C) Opsin
D) Retinal subunit
E) Carboxy terminus

Question 16

Within picoseconds of a photon being absorbed by rhodopsin,

A) retinal undergoes photoisomerization, shifting from 11-cis retinal to all-trans retinal.
B) opsin changes configuration to metarhodopsin II.
C) rhodopsin is regenerated and able to bind photons again.
D) the membrane potential of the photoreceptor is altered.
E) the outer segment of the photoreceptor separates from the inner segment.

Question 17

You are tracking the concentration of rhodopsin in a culture of rod cells. Following a flash of light, you return the culture to complete darkness. How long will it take for the concentration of rhodopsin to return to the state observed before the flash?

A) Seconds
B) Picoseconds
C) Minutes
D) Up to an hour
E) Microseconds

Question 18

In most invertebrates, light _______ photoreceptors; in most vertebrates, light _______ photoreceptors.

A) hyperpolarizes; depolarizes
B) hyperpolarizes; hyperpolarizes
C) depolarizes; depolarizes
D) depolarizes; hyperpolarizes
E) depolarizes and hyperpolarizes; hyperpolarizes

Question 19

Rhodopsin responds to light by causing _______ channels to close, halting the constant influx of these ions into photoreceptors that occurs in darkness.

A) calcium and sodium
B) potassium and calcium
C) sodium and chlorine
D) chlorine and calcium
E) potassium and sodium

Question 20

Cyclic guanosine monophosphate (cGMP) found in the cytoplasm of photoreceptors is usually found in

A) high quantities in the dark, where its presence keeps ion channels open.
B) low quantities in the dark, during which ion channels are closed.
C) high quantities after the absorption of photons, which causes ion channels to open.
D) low quantities after the absorption of photons, which causes ion channels to open.
E) high quantities after the absorption of photons, which causes ion channels to close.

Question 21

Ion channels on photoreceptors that open or close due to cyclic guanosine monophosphate (cGMP) are responsible for maintaining the photoreceptor's resting membrane potential, which is usually about

A) -80 mV, until it is depolarized by light.
B) -40 mV, until it is depolarized by light.
C) -80 mV, until it is hyperpolarized by light.
D) -40 mV, until it is hyperpolarized by light.
E) -20 mV, until it is hyperpolarized by light.

Question 22

The hydrolyzation of cyclic guanosine monophosphate (cGMP) is caused by the interaction between transducin and which molecule?

A) Metarhodopsin I
B) Metarhodopsin II
C) Thodopsin
D) 11-cis retinal
E) All-trans retinal

Question 23

Reduced concentrations of the molecule cGMP causes channels in the cell membrane of photoreceptors to _______, which _______ the cell.

A) open; hyperpolarizes
B) open; depolarizes
C) form; hyperpolarizes
D) close; hyperpolarizes
E) close; depolarizes

Question 24

During sustained illumination, a decrease in intracellular _______ prevents all nucleotide gated channels in photoreceptors from closing.

A) potassium
B) calcium
C) sodium
D) chlorine
E) carbon

Question 25

Dark adaptation takes much longer than light adaptation. What is one reason this is the case?

A) Light adaptation involves the release of potassium, which is rapidly pumped through ion channels.
B) Dark adaptation is limited by the number of rods, which is much lower than the number of cones.
C) Light adaptation is handled by many photoreceptors while dark adaptation is handled by only a few.
D) Dark adaptation takes longer because fewer photons of light reach the retina.
E) Dark adaptation is limited by the recovery of pigment molecules in photoreceptors, which takes a long time.

Question 26

What do cone and rod pigments have in common?

A) They are all found in extracellular space.
B) They are all made up of the same amino acids.
C) They all contain 11-cis retinal.
D) They are all equally sensitive to light.
E) They are all found in the inner segment.

Question 27

Why do some photoreceptors respond to blue light, while others respond to red or green?

A) There are differences in the amino acid sequences for their opsin proteins.
B) There are differences in the amino acid sequences for their 11-cis retinal.
C) Photoreceptors for different colors are found at different depths within the retina.
D) Photoreceptors for different colors utilize center-surround organization in different ways.
E) Photoreceptors for different colors regenerate at different rates, leading to the perception of color.

Question 28

Through inheritance, Jorge does not possess long (L) or medium (M) cones in his retina. Jorge's vision is impacted in which way?

A) He can only perceive shades of the color blue.
B) He can perceive shades of blue and green.
C) He cannot perceive any color.
D) He can perceive only shades of yellow and green.
E) He cannot see properly in the dark.

Question 29

Which statement about receptive fields is true?

A) Receptive fields are only found primates.
B) Receptive fields are only found in relation to rods.
C) Receptive fields come in only two varieties.
D) Receptive fields tell the brain about patterns of light and dark.
E) Receptive fields are only found in invertebrates.

Question 30

Cones in the fovea are clustered in hexagonal patterns (one center, six surround). Flashing a light on the central cone produces perception of

A) whichever color cone is in the center.
B) whichever color cone makes the majority of the surround.
C) a number of colors, depending on background color and cones in the surround.
D) a number of colors, depending on cones in the surround.
E) whichever color light is used on the center cone.

Question 31

Which of the following is true about the center-surround organization of receptive fields?

A) Illumination of both the center and the surround leads to an increase in cell activity in the same direction.
B) Illumination of both the center and the surround leads to a decrease in cell activity in the same direction.
C) Illumination of both the center and the surround leads to an antagonistic effect on cell activity, with one exciting the cell and the other inhibiting the cell.
D) Only illumination of the center of the receptive field has an effect on cell activity.
E) Only illumination of the surround of the receptive field has an effect on cell activity.

Question 32

Which of the following is true about horizontal cells?

A) Horizontal cells are connected to one another via gap junctions.
B) Horizontal cells do not synapse directly with photoreceptors.
C) Horizontal cells synapse directly with retinal ganglion cells.
D) Horizontal cells release glutamate.
E) Horizontal cells produce action potentials.

Question 33

Which type(s) of cell receive(s) input directly from cones?

A) Depolarizing bipolar cell
B) Hyperpolarizing bipolar cell
C) Both depolarizing and hyperpolarizing bipolar cells
D) Ganglion cell
E) Amacrine type II (AII) cell

Question 34

What is the primary neurotransmitter released by photoreceptors?

A) Dopamine
B) Glycine
C) Glutamate
D) Acetylcholine
E) ℽ-aminobutyric acid (GABA)

Question 35

What is the primary neurotransmitter released by horizontal cells?

A) Glutamate
B) Nitric oxide
C) ℽ-aminobutyric acid (GABA)
D) Glycine
E) Serotonin

Question 36

In response to light in the surround of their receptive fields, H bipolar cells are _______, while D bipolar cells are _______.

A) unaffected; hyperpolarized
B) depolarized; hyperpolarized
C) depolarized; depolarized
D) hyperpolarized; depolarized
E) hyperpolarized; unaffected

Question 37

Rods synapse with _______, which in turn synapse with _______.

A) hyperpolarizing (H) bipolar cells; amacrine type II (AII) amacrine cells
B) amacrine type II (AII) cells; depolarizing (D) bipolar cells
C) hyperpolarizing (H) bipolar cells; depolarizing (D) bipolar cells
D) depolarizing (D) bipolar cells; horizontal cells
E) depolarizing (D) bipolar cells; amacrine type II (AII) cells

Question 38

While watching the sun set in your garden, you notice that at first, the red-colored flowers are very vibrant compared to the blue flowers. However, as the sunlight begins to fade, you notice this reverses: the red flowers start to look dull and dark while the blue flowers look vibrant and bright. What is this phenomenon known as?

A) Monochromacy
B) The Thatcher effect
C) Acute color blindness
D) The Purkinje effect
E) Protanopia

Question 39

Which ganglion cell type is most likely to respond to a moving black circle shown in the periphery of vision?

A) Koniocellular (K)
B) Parvocellular (P)
C) Amacrine (A)
D) Long (L)
E) Magnocellular (M)

Question 40

Specialized cells called ______ can respond to light directly, rather than only through a signaling cascade from rods and cones.

A) parvocellular rods
B) midget ganglion cells
C) melanopsin sensitive bipolar cells
D) retinal photosensitive horizontal cells
E) intrinsically photosensitive retinal ganglion cells

Question 41

A certain breed of mice is shown to be unable to regulate their sleep schedule in response to regular cycles of bright and dim light. What is one mechanism through which these mice could have obtained this deficiency?

A) The mice were bred without long (L) cones.
B) The mice were bred without rods.
C) The mice were bred without intrinsically photosensitive retinal ganglion cells.
D) The mice were bred without horizontal cells.
E) The mice were bred without the ability to produce retinal.

Question 42

A friend is recounting a time when she was home and saw something move out of the "corner of her eye." When she turned to look at, all she saw was her coat hanging on a hook. Your friend is convinced what she saw was not of this world. What could you tell your friend about our visual system to put your friend's mind at ease?

Question 43

Photoreceptors synapse with other cell types before their signals reach the optic nerve. Describe how this process differs for the two main types of photoreceptor.

Question 44

Using 1-2 sentences, describe how the three different types of cones contribute to color vision in humans.

Question 45

Using your knowledge of the anatomy of the human retina, describe a possible experiment that would reveal where the blind spot created by optic nerves leaving the retina is located in an individual's visual field (hint: you can only do this with one eye open).

Question 46

Your grandfather is telling a story about how when he was camping in the northern part of Canada, he saw a black bear one night that was "as big as a grizzly." Knowing that black bears are usually a fraction of the size of a grizzly, how might you respond to this story?

Question 47

Describe what happens to the pigment rhodopsin when a photon of light hits it.

Question 48

Briefly describe the state of photoreceptors in darkness in terms of their electric potential.

Question 49

Describe a possible reason why it is advantageous for humans to be able to adapt quickly to changes in ambient illumination.

Question 50

Historical legend suggests that pirates used to wear eye patches over one good eye so that they could quickly switch to using the usually-covered eye when entering the darkened holds of enemy ships. Does this legend have merit from a physiological standpoint? Why or why not?

Question 51

Name one thing pigments in rods and cones have in common, and describe the major way in which pigments in rods and cones differ that leads to their differing responses to light.

Question 52

Describe how lacking just one type of cone can cause color blindness in humans.

Question 53

Receptive fields are an important concept to understand when studying the retina. Define receptive fields and describe their organization.

Question 54

Early one evening, you are struck by how vivid the blue flowers in your garden appear. You quickly pull out your phone and take a flash picture of your garden. However, you are dismayed to see that the blue flowers in your photo are muted compared to the red flowers. Assuming a camera works the same way as a human eye, what might explain this effect?

Question 55

There are three main categories of regional ganglion cells. Name the three types and give an example of the information they carry.