MC from dashboard quiz Ch 10 Flashcards
1
Q
- The iris
a. is responsible for the refraction of light onto the retina.
b. regulates the amount of light entering the eye.
c. applies tension to the lens.
d. contains the pigment epithelial cells that nourish photoreceptors.
e. covers the cornea, shielding it from harmful UV rays.
A
Answer: b
Textbook Reference: Anatomy of the Eye
Bloom’s Level: 1. Remembering
2
Q
- Our underwater vision is poor because
a. water disperses light, making it impossible to focus.
b. under water there is no longer a refractive index difference between the cornea and the
surrounding media.
c. water seeps into the iris, causing temporary cloudiness.
d. the hydrostatic pressure of water changes the shape of the eyeball.
e. the ions in the water cause hyperpolarization in the photoreceptor cells.
A
Answer: b
Textbook Reference: Image Formation on the Retina
Bloom’s Level: 2. Understanding
3
Q
- Why is myopia in humans thought to be more common now than it was in ancient
times?
a. The vigorous exercise associated with early human lifestyles better nourished the
retina.
b. Early humans were not exposed to the environmental toxins present in modern life.
c. Chronic exposure to fire smoke had a protective effect on the vision of early humans.
d. Early humans did not engage in the kinds of activities (e.g., reading and writing from
an early age, watching television) characteristic of modern life.
e. Myopia was not less common; it was less recognized.
A
Answer: d
Textbook Reference: Box 11A: Myopia and Other Refractive Errors
Bloom’s Level: 1. Remembering
4
Q
- The fovea
a. covers approximately 40 percent of the retina.
b. lies at the center of the optic disk.
c. lies at the center of the macula lutea.
d. is synonymous with “fundus.”
e. is the only part of the retina that contains xanthophyll.
A
Answer: c
Textbook Reference: The Retinal Surface
Bloom’s Level: 1. Remembering
5
Q
- Age-related macular degeneration, or AMD,
a. is rising in incidence in the United States.
b. can be detected by means of the Amsler grid.
c. can result from gradual loss of the pigment epithelium (dry AMD).
d. can be treated by laser-induced phototoxicity (wet AMD).
e. All of the above
A
Answer: e
Textbook Reference: Clinical Applications: Macular Degeneration
Bloom’s Level: 2. Understanding
6
Q
- Which sequence represents the most direct pathway for the transmission of visual
information from the eye to the brain?
a. Photoreceptor → bipolar cell → ganglion cell → brain
b. Horizontal cell → bipolar cell → ganglion cell → brain
c. Photoreceptor → bipolar cell → amacrine cell → brain
d. Photoreceptor → horizontal cell → ganglion cell →brain
e. Photoreceptor → bipolar cell → amacrine cell → ganglion cell → brain
A
Answer: a
Textbook Reference: Retinal Circuitry
Bloom’s Level: 3. Applying
7
Q
- The two main functions of the retinal pigment epithelium are _______ and _______.
a. structural support to maintain curvature of the retina; phagocytosis of shed outer
segments
b. structural support to maintain curvature of the retina; synthesis of rhodopsin
c. phagocytosis of shed outer segments; synthesis of rhodopsin
d. phagocytosis of shed outer segments; regeneration of the photoreceptor photopigments
e. synthesis of rhodopsin; regeneration of the photoreceptor photopigments
A
Answer: d
Textbook Reference: The Pigment Epithelium
Bloom’s Level: 2. Understanding
8
Q
- Which mechanism is not a component of the phototransduction signaling cascade
initiated by light falling on a rod?
a. Absorption of a photon of light by 11-cis retinal
b. Activation of protein kinase A
c. A conformational change in the rhodopsin protein
d. Dissociation of the α subunit of transducin from the β/γ complex
e. Increased activity of PDE (phosphodiesterase)
A
Answer: b
Textbook Reference: Phototransduction
Bloom’s Level: 2. Understanding
9
Q
- The mechanism that accounts for light-induced hyperpolarization of photoreceptors is
a. the gating of ion channels by released retinal monomers.
b. a sudden increase in the concentration of cAMP, leading to activation of potassium
channels.
c. a rapid fall in the concentration of cGMP, leading to closure of Na + / Ca 2+ channels.
d. a rapid rise in the concentration of cGMP, leading to closure of Na + / Ca 2+ channels.
e. light-induced photoisomerization of membrane-bound calcium channels.
A
Answer: c
Textbook Reference: Phototransduction
Bloom’s Level: 1. Remembering
10
Q
- Which statement regarding photoreceptor cells is true?
a. Like typical sensory neurons, they fire action potentials when the cell depolarizes to
threshold in response to stimuli.
b. Unlike typical neurons, their resting membrane potential is more negative, usually
around –100mV.
c. Unlike typical neurons, cation channels are open at rest, allowing the influx of sodium
and calcium.
d. Unlike typical neurons, neurotransmitter release is dependent on an influx of potassium
ions.
e. Unlike typical neurons, they hyperpolarize in response to a stimulus due to opening of
chloride channels.
A
Answer: c
Textbook Reference: Phototransduction
Bloom’s Level: 2. Understanding
11
Q
- The death of retinal cells in retinitis pigmentosa is most likely caused by
a. infection.
b. apoptosis.
c. excessive light exposure.
d. environmental toxins.
e. injury to the eye.
A
Answer: b
Textbook Reference: Box 11B: Retinitis Pigmentosa
Bloom’s Level: 1. Remembering
12
Q
- The main reason that rods are more sensitive to light than cones is that
a. the photopigment of rods is much more sensitive to light than the photopigment used in
cones.
b. the eye contains 1000 times as many rods as cones.
c. the rod transduction mechanism provides greater signal amplification.
d. rods are sensitive to a much broader range of wavelengths.
e. rods have many different types of opsin proteins.
A
Answer: c
Textbook Reference: Functional Specialization of the Rod and Cone Systems
Bloom’s Level: 2. Understanding
13
Q
- By which mechanism are rod signals transmitted in conditions of low light?
a. Rod bipolar cells synapse on amacrine cells, which in turn synapse on cone bipolar
cells.
b. Rod bipolar cells synapse on off-center ganglion cells that then transmit the rod signals
to other ganglion cells.
c. Rod bipolar cells of both on and off types send outputs selectively to on- and off-center
ganglion cells.
d. Rod photoreceptors send their outputs directly to melanopsin-containing ganglion
cells.
e. Rod photoreceptors send their signals mainly through horizontal cells to the rod bipolar
cells.
A
Answer: a
Textbook Reference: Functional Specialization of the Rod and Cone Systems
Bloom’s Level: 2. Understanding
14
Q
- Which statement about the distributions of rods and cones is true?
a. Because cones carry three different color channels, there are three times as many cones
as rods.
b. Rods outnumber cones by 100 to 1, which explains the greater sensitivity of rods in
low light.
c. Rods are evenly distributed across the entire retina.
d. The density of cones is 200-fold higher in the fovea than in the most eccentric retinal
regions.
e. The density of rods is highest in the far periphery of the retina.
A
Answer: d
Textbook Reference: Anatomical Distribution of Rods and Cones
Bloom’s Level: 2. Understanding
15
Q
- Which statement about color vision is false?
a. Because there are several different color types of cones, they are more sensitive to low
(dim) illumination levels than the population of rods is.
b. Cones (in humans) come in three different “colors”: blue, green, and red (or short-,
medium-, and long-wavelength).
c. Different wavelengths of light produce different patterns of activity in the cone
population as a whole.
d. Information from specific color cones can be selectively relayed to specific regions of
a retinal ganglion cell’s receptive field.
e. The different photopigments in each cone are highly sensitive to a small range of
wavelengths but can actually be activated by photons of a wide range of wavelengths.
A
Answer: a
Textbook Reference: Cones and Color Vision
Bloom’s Level: 4. Analyzing
18
Q
- Refer to the figure.
For an OFF-center ganglion cell, which stimulus on the cell’s receptive field would cause
the highest rate of action potential firing? (In the figure, black fill indicates darkness, and
white fill indicates light in the receptive field.)
A
Answer: a
Textbook Reference: Retinal Circuits for Light and Dark
Bloom’s Level: 4. Analyzing
19
Q
- Refer to the figure.
The illusion shown, in which dark rectangles are placed within a pattern of light and dark
bars, is best explained by which statement?
a. Light scatters between adjacent photoreceptors.
b. Photoreceptors are unable to spatially resolve the intersections of the white bars.
c. Photic information is conveyed only by graded electrical responses.
d. Brightness percepts are generated on a statistical basis as a means of contending with
the inherent ambiguity of luminance.
e. All of the above are equally valid explanations.
A
Answer: d
Textbook Reference: Box 11D: The Perception of Light Intensity
Bloom’s Level: 3. Applying
