Photoreceptors Practice Test

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• Which statement correctly describes color perception in the visual system's cones and rods?
• The critical area for spatial summation is larger for which photoreceptor type?
• What is the resting membrane potential of rods?
• What is the half-life of cone rhodopsin regeneration?
• Which of the following is included in the inner segment of photoreceptors?
• Which color do short-wavelength cones respond to?
• Which wavelength corresponds to the blue cone type?
• The photopic spectral sensitivity curve represents the sum of absorption spectra from which two types of cones?
• How many activated rods are needed to activate a ganglion cell?
• Which cone type is typically the most numerous?
• What is the approximate peak density of cones in the foveola?
• Which system has greater temporal summation: scotopic or photopic?
• Where are photopigments primarily located in photoreceptors?
• Phototransduction causes a decrease in the concentration of which second messenger?
• Where does the S-cone density peak occur in the retina?
• What is the maximal absorption wavelength of rhodopsin?
• If an ERG has a d-wave, is it scotopic or photopic?
• In retinitis pigmentosa, which two ERG changes are commonly observed?
• In the transmission experiment, what can we use to measure the amount of monochromatic light transmitted through a box of rhodopsin?
• S cones can be found highly packed from 0 to 0.5 degrees of the fovea.
• What term describes several presynaptic neurons synapsing onto a single postsynaptic neuron, as in many rods converging on one bipolar cell?
• Which system is associated with a 20/20 spatial resolution?
• Region where ganglion cell axons leave the eye as the optic nerve?
• Photon absorption triggers phototransduction, leading to the closing of which channels?
• The principle stating that any single cone system is colorblind is called what?
• Near the peripheral retina, each rod bipolar cell collects signals from about how many rods?
• The 10 minute arc stimulus was used to investigate which phenomenon?
• Which stimulus conditions are important to consider when recording an ERG?
• What is the width of the foveola in degrees?
• True or false: One type of cone alone cannot differentiate between different wavelengths of light.
• Why are cones not as sensitive to light as rods?
• True or false: Each retinal ganglion cell receives signals from several photoreceptors.
• Compared with full-field ERG, multifocal ERG mainly provides information about what?
• Which photoreceptor mediates the scotopic visual system?
• Under scotopic conditions, the Stiles-Crawford effect shows what?
• True or false: Under scotopic conditions, photons falling within the summation area are summed regardless of their spatial distribution.
• For assessing localized retinal dysfunction, which ERG type is most appropriate?
• Which statement about retinal neurons is most accurate?
• What psychophysical method was used?
• When do rods mostly shed their outer segment discs?
• What is the critical area (summation area) for the rod system?
• Photopic vision corresponds to roughly which luminance range?
• Pattern ERG preserves which property of the stimulus while changing the pattern?
• In a scotopic ERG, which waveform is labeled as "b"?
• What do you need to compare between different types of cones in order to differentiate wavelengths?
• Which statement best describes the outer segment's role in photopigment localization?
• Which procedure measures temporal summation psychophysically?
• In the retina, which cells encounter light first?
• The bundle forming the optic nerve consists of the axons of which retinal cells?
• Which wavelength is the scotopic visual system most sensitive to?
• Hyperpolarization of a rod leads to a decrease in its release of what neurotransmitter?
• Which photoreceptors show greater temporal summation?
• Near the fovea, each rod bipolar cell collects signals from about how many rods?
• If an ERG has a c-wave, is it scotopic or photopic?
• How many rods are in the human retina?
• What is the purpose of the Ganzfeld Dome in ERG testing?
• In congenital stationary night blindness due to rhodopsin mutations, which cellular mechanism causes rod dysfunction?
• What does spatial summation specifically refer to?
• What does the 5-minute half-life represent in rhodopsin regeneration?
• Which retinal system is more sensitive to wavelengths longer than 650 nm?
• Mutations in which protein are associated with bradyopsia?
• The retina’s layers are inverted relative to the direction of incoming light. True or false?
• Which cells are responsible for the d-wave?
• Which process is continuously taking place in the outer segments of photoreceptors?
• True or false: Rods have directional sensitivity.
• In a photopic ERG, which photoreceptors contribute to the a-wave?
• A photopic ERG signal reflects the activity of which photoreceptors and under what adaptation?
• In the retina, which cells connect with bipolar cells to convey signals to the ganglion cells?
• Which ERG stimulus condition is used to measure amacrine cell activity?
• What unit is used to express the summation area for the rod system?
• Which waves are found on a photopic ERG?
• In very dim light, which photoreceptors detect light first, and do they convey color information?
• Scotopic vision corresponds to roughly which luminance range?
• Which additional retinal structures can influence the ERG signal besides photoreceptors and bipolar cells?
• Typically, which cones are least numerous and what color do they respond to?
• During spatial summation, signals from multiple photoreceptors converge onto which intermediate neuron before reaching the ganglion cells?
• Which molecule is the light-sensitive pigment in rods?
• Post-receptor cells connected with which photoreceptors have a larger summation area?
• The d-wave polarity is what?
• In phototransduction, spatial summation results when what sequence occurs?
• What is the maximal absorption wavelength of cyanolabe?
• Photons not absorbed by the outer segments are mostly absorbed by which retinal layer?
• In ERG testing, what does a weak flash in a dark-adapted eye primarily assess?
• Under scotopic conditions, how does spatial resolution compare to photopic?
• Which region contains the lowest density of cones?
• At what wavelength is the photopic visual system most sensitive?
• According to the findings, at least how many rods must be activated to produce a reliable visual response?
• Which retinal system is more sensitive to wavelengths shorter than 650 nm?
• Oscillatory potentials in an ERG primarily reflect the activity of which retinal cells?
• Which statement best describes why dark adaptation was used in the study?
• Does the scotopic system have more or less spatial summation?
• Pattern ERG signals are mainly generated by which retinal cells?
• In a scotopic electroretinography, which wave is considered the slower third wave?
• Which photopigment is found in L-cones?
• Which phenomenon describes how the sensitivity of the retina changes with the entry location of light at the pupil, due to directional sensitivity of cones?
• At what membrane potential have we reached saturation of sodium channels?
• Which system has greater temporal resolution: scotopic or photopic?
• What composes the optic nerve?
• Which wavelength region is most likely absorbed by rhodopsin according to the transmission experiment?
• If a target exceeds the summation area, the number of quanta required for threshold detection will:
• Scotopic vision is mediated by which photoreceptors?
• In the center of the fovea, how many cones does each cone bipolar cell collect signals from?
• As the time between test flashes increases, the second signal can arrive up to how many msec later to still be summated?
• Which ERG is designed to map retinal function across multiple locations?
• Oscillatory potentials originate from which retinal cells?
• In the transmission experiment graph, which quantity is plotted on the x-axis?
• Which statement best describes the Purkinje shift?
• Two simultaneous 5-quanta flashes under scotopic conditions at two locations are perceived as how many ganglion cells contributing to perception?
• Under the principle of univariance, how many cone types are needed to differentiate wavelengths?
• How can we measure the absorption probability of different wavelengths for photopigments?
• Which waveform is associated with offset of the stimulus in a photopic ERG?
• What wavelength did they use in the study?
• Where does S cone density peak?
• In retinitis pigmentosa, which combination of changes is typical on ERG?
• Rods are most densely packed at about how many degrees from the fovea?
• Which statement describes the optic disc?
• Where are the most cones found in the retina?
• A light with wavelength 450 nm is gradually brightened. Which system and photoreceptor detect it first, and how does the color change as it becomes brighter?
• What term refers to the integration of EPSPs and IPSPs in the postsynaptic neuron?
• How can spatial summation be psychophysically measured?
• What is included in the outer segment of photoreceptors?
• There are 3 types of cones, which vary based on what?
• True or false: Absorption of one photon is enough to activate rhodopsin?
• Cone density is highest in the foveola at about 200,000 cones/mm^2. As you move outward, does the concentration increase or decrease?
• Phototransduction summary: Change in voltage occurs in which structure; Change in the concentration of what in the synapse; Change in the membrane potential of the post-synaptic cells; Change in the release of what at the next synaptic terminal?
• When a 450 nm light begins very dim and increases in brightness, what color is perceived once the rods have detected it and cones are not yet active?
• A flicker stimulus is used when measuring which type of ERG?
• If the inter-flash interval is increased beyond 100 ms, summation will occur?
• In a scotopic ERG, which waveform is labeled as "c"?
• Which example illustrates spatial summation?
• Where is the negative reference electrode placed during an ERG recording?
• Photopigment found in S-cones
• What is the width of the optic disc in degrees?
• A key consequence of large convergence in the rod pathway is what?
• Typically, which cones are most numerous and what color do they respond to?
• According to the principle of univariance, how can we differentiate wavelengths?
• The critical area for spatial summation increases with retinal eccentricity for which photoreceptor types?
• During ERG testing, which adaptation state is commonly used to assess rod function?
• With light of wavelength 507 nm hitting the retina, is this a greater or lesser threshold for rods to respond?
• What is the width of the fovea in degrees?
• Which system has poorer spatial resolution due to large summation?
• As eccentricity increases, does cone density increase or decrease?
• Which retinal cells send signals from the retina to the brain via the optic nerve?
• Which part of the photoreceptor contains the nucleus?
• Temporal summation refers to what?
• The 1 millisecond duration was used to study which type of summation?
• Which photoreceptors recover faster after bleaching?
• In a scotopic ERG, which photoreceptors contribute to the a-wave?
• Which of the following is NOT one of the five standard ERG tests?
• Which photoreceptors have the higher threshold for detecting light?
• What is the initial symptom of retinitis pigmentosa?
• Which photoreceptors are primarily affected in CSNB?
• What is the benefit of the photopic system’s reduced spatial summation?
• What percentage of incident quanta are transmitted in the example?
• Which two cell types are the main contributors to the ERG signal?
• In photopic conditions, if light enters the pupil through the center to reach the retina, does the light appear brighter or dimmer?
• Which cells in the retina encounter light first?
• Which type of cones contributes the least to the photopic spectral sensitivity curve?
• What term describes the difference in sensitivity between the scotopic and photopic systems for a given wavelength?
• What is the half-life for rhodopsin regeneration?
• What term describes the size of the summation area used to trigger an action potential?
• Which photopigment has a maximal absorption wavelength of 507 nm?
• As we age, the amount of rods in the retina tends to?
• What is the approximate membrane potential range for a rod during hyperpolarization?
• What cells are primarily responsible for the b-wave in an ERG?
• What term describes the process when all sodium channels are closed even though only about 10% of rhodopsin has been bleached?
• What is the order of the three main cells in the phototransduction process? (feedforward connection)
• Which factor remains constant within the same cone type, limiting single-cone color discrimination?
• Which lighting condition is best described as dawn or dusk levels, involving both rods and cones?
• Threshold for observers to see a faint impression of light (quanta incident on the cornea) falls in which range?
• In the transmission experiment, what molecule is put in a box for monochromatic light to shine through?
• How many cones are in the human retina?
• As cones move away from the fovea, what happens to the degree of spatial summation?
• Far peripheral retina, each rod bipolar cell collects signals from about how many rods?
• During measurement of temporal summation, how long is the time window within which quanta must be summed together?
• Which waves are found on a scotopic ERG?
• An electroretinogram primarily records the response to what stimulus?
• Are there more cones in the nasal or temporal retina?
• Where is the ground electrode placed during an ERG recording?
• What clinical significance does an electroretinogram have?
• Which non-invasive method records the retina's summed electrical potentials?
• In the context of directional sensitivity, light striking the cones at what orientation is absorbed most efficiently?
• Which pair of wavelengths corresponds to the peak sensitivities of the scotopic and photopic systems, respectively?
• Under scotopic conditions, two simultaneous flashes occur at two locations, and each flash results in 5 quanta absorbed by photoreceptors. How many lights are perceived?
• What light source is commonly used to stimulate the entire retina during ERG recording?
• What is the outermost layer of the retina that provides metabolic support and absorbs light not absorbed by photoreceptors?
• Which description best characterizes the pattern of rod and cone distribution around the fovea?
• Just 1 degree away from the fovea, cone density relative to its maximum at the foveola is about?
• True or false: Rods and cones are distributed equally throughout the retina.
• Which cone photopigment has a maximal absorption wavelength of 557 nm?
• What photoreceptive state should the subject be in before recording an ERG?
• In a transmission experiment, 100 quanta of light at 400 nm are incident and 80 quanta are transmitted. How many quanta did rhodopsin absorb?
• The condition characterized by delayed termination of phototransduction, causing temporary blindness when transitioning to bright light, is called?
• Which color do long-wavelength cones respond to?
• For a blue light at 400 nm, under Purkinje effect, under which lighting condition will it appear brighter?
• During rod phototransduction, what is the immediate effect on membrane potential when Na+ channels close?
• The Stiles Crawford effect relates to two perceptual aspects of vision. Which pair best describes these Type I and Type II categories?
• Which inherited disorder is characterized by degeneration of photoreceptors and accumulation of retinal pigments?
• What happens to the spacing of cones with increasing retinal eccentricity?
• Which photoreceptor type has higher light sensitivity?
• Around the fovea, the greatest concentration of rods and cones is surrounding which retinal feature?
• Why are rods more sensitive to light than cones?
• Which photoreceptor type tends to have more photoreceptors connected to a single post-synaptic bipolar cell?
• In this study, quanta refer to which of the following?
• What cells are responsible for the a-wave in an ERG?
• The cone photoreceptor’s synaptic ending is called?
• Which statement best describes the electroretinogram?
• In photopic vision, less spatial summation leads to which effect on sensitivity?
• Does the optic disc contain rods, cones, both, or neither?
• What term describes the angle-dependent absorption of light by cones?
• Which statement best describes the role of the retinal pigment epithelium (RPE) with respect to light?
• Which wave is primarily generated by glial cells and the retinal pigment epithelium?
• Which ERG condition primarily evaluates cone function?
• Are there more rods or cones in the retina?
• Which inherited disorder affects rod photoreceptors and impairs night vision and may involve rhodopsin gene mutations?
• The rod photoreceptor’s synaptic ending is called?
• Pattern ERG is used to assess which type of vision?
• In the visual system, does the photopic system exhibit more or less spatial summation?
• Which cells in the retina encounter light last?
• Which term describes vision under low-light conditions primarily mediated by rods?
• Spatial summation involves combining inputs from multiple synapses at different locations.
• Photopic ERG refers to vision under which lighting condition?
• Pattern ERG can be recorded using what type of stimuli?
• What happens to the size of cones with increasing retinal eccentricity?
• Thresholds were determined after which adaptation condition?
• Is a single synapse typically enough to reach threshold and trigger an action potential?
• Approximately how far apart are S cones?
• The d-wave is associated with which type of ERG?
• The scotopic system is mediated by which photoreceptors?
• Which statement about the retina is true?
• Which part acts as a light guide to direct photons toward photopigments?
• Under photopic conditions, with the same setup of two simultaneous flashes delivering 5 quanta each, how many lights are perceived?
• Why isn't the 15-minute arc flash seen in the described threshold test?
• Which photoreceptors mediate photopic vision?
• Which photopigment is found in M-cones?
• Under equal luminance, which color would appear brighter under scotopic conditions?
• The spectral sensitivity maximums for scotopic and photopic systems are approximately what values?
• Mesopic vision is mediated by which photoreceptors?
• Which photopigment is found in S-cones?
• When light hits a rod, what substance absorbs the photons?
• Pattern ERG displays typically involve which pattern?
• Which system has better spatial summation?
• In the described experiments, how many quanta does each test flash emit?
• What concept explains why a single ganglion cell can respond to inputs from multiple photoreceptors?
• For a red light at 680 nm, under Purkinje effect, under which lighting condition will it appear brighter?
• Duration required for multiple synapses in rapid succession to result in a stronger depolarization to trigger an action potential
• When measuring spatial summation, how many quanta do rods require to reach threshold?
• Where is the blind spot on the retina located?
• Which color do medium-wavelength cones respond to?
• The very center of the fovea has no rods and is dominated by a high density of which photoreceptor type?
• A strong flash delivered to a dark-adapted eye reflects activity of which photoreceptors?
• In plotting the transmission experiment graph, which quantity is represented on the y-axis?
• What is the maximal absorption wavelength of chlorolabe?
• Is the a-wave positive or negative in an ERG?
• A scotopic ERG signal reflects the activity of which photoreceptors, using a weak flash in a dark-adapted eye?
• Wave 3 in a scotopic ERG corresponds to which wave label?
• Which wavelength corresponds to the red cone type?
• Is the c-wave positive or negative?
• What stimulus size was used?
• Which photoreceptors have the highest detection threshold?
• Which photoreceptors have directional sensitivity?
• In phototransduction, does the closing of sodium channels lead to depolarization or hyperpolarization of the rod?
• Which ERG technique records photopic responses from multiple retinal locations?
• In the generation of the b-wave, which cells depolarize alongside bipolar cells?
• Which part of a photoreceptor does light encounter first?
• Where is the main electrode placed during an ERG recording?
• How many rods need to be activated to elicit a visual response?
• 100 rhodopsins are bleached with photons of light. After 10 minutes, how many have recovered and are now unbleached?
• A flicker stimulus, as opposed to a constant light, primarily assesses which photoreceptor system?
• Twilight conditions are mediated by which photoreceptors?
• Photopic vision is characterized by which lighting condition?
• The time from stimulus onset to the peak ERG response is called what?
• What is the initial negative wave on a scotopic or photopic ERG?
• Which statement best describes cone photopigment distribution?
• What do discs in rods and cones contain?
• Which wavelength corresponds to the green cone type?
• Which cone photopigment has a maximal absorption wavelength of 426 nm?
• What is the approximate threshold potential commonly cited for triggering an action potential in neurons?
• True or false: The photopic system is most sensitive at 507 nm. The scotopic system is most sensitive at 555 nm.
• The process that integrates neural inputs to a post-receptor cell is called what?
• What is the maximal absorption wavelength of erythrolabe?
• Which photoreceptors are affected first in retinitis pigmentosa (RP)?
• What retinal location was tested in the experiment?
• Why is the retina considered inverted?
• As the test flash area increases, the number of quanta required for detection remains the same up to what size?
• What photopigment(s) are in rods?
• Approximately how many ganglion cell axons leave the retina to form the optic nerve?
• Approximately how many photoreceptors are there in the retina relative to the number of retinal ganglion cells?
• Which retina region contains more cones, nasal or temporal retina, and by approximately what percentage?
• If an ERG shows activity from both rods and cones, which stimulus condition is likely?
• What is the order of the two main cells in the feedback phototransduction process? (i.e. NOT going toward the optic nerve)
• Which retinal cells participate in horizontal, lateral interactions across neighboring photoreceptors?
• Which combination defines a photopic ERG?
• Which photoreceptors bleach faster under typical light exposure?
• Which wave is the second positive wave on a scotopic or photopic ERG?
• The third wave on a photopic ERG, associated with offset of the stimulus, is which wave?
• According to a topographic map, the highest rod density is a ring encircling the fovea at what eccentricity?
• Which cells are primarily responsible for initiating phototransduction when light is detected?
• Pattern ERG uses which type of stimulus to evoke retinal responses?
• What stimulus duration was used?
• What is the typical acuity associated with rod-dominated (scotopic) vision?
• The photopigment with a peak absorption at 530 nm is found in which cone type?
• Multifocal ERG responses are typically associated with which lighting condition?
• Which photoreceptors exhibit neural convergence?
• Which photoreceptors have the higher sensitivity of detecting light?
• On a topography map, a cone streak is described as occurring in which direction?
• Under scotopic conditions, which wave is typically the earliest measurable response?
• 100 rhodopsins are bleached with photons of light. After 5 minutes, how many have recovered and are now unbleached?
• 555 nm peak sensitivity corresponds to which visual system?
• Which color is detected by the long-wavelength cone system?
• What wavelength is commonly used as a practical threshold between scotopic and photopic sensitivity?
• Which cone type is typically the least numerous?
• Under photopic conditions, two 5-quanta flashes cause how many ganglion cells to reach threshold?
• Are rods more numerous in the central or peripheral retina?
• Window of time over which the rod system sums absorbed photons
• In the described psychophysical experiment, what is the primary measurement used to determine the threshold for temporal summation?
• What cells are responsible for the c-wave in an ERG?
• What is the trade-off associated with the large spatial summation in the scotopic system?
• Absorption of how many photons does it take to bleach rhodopsin?
• In the Hecht-Schlaer-Pirenne 1942 experiment, which lighting system and photoreceptors were investigated?
• Are there S-cones at the central 0.3-0.4 degrees of the fovea?
• Which ERG test uses rapid light flashes to evaluate cone function?
• How many quanta are actually needed to elicit a visual response?
• Wave 2 in a scotopic ERG corresponds to which wave label?
• Which region shows the greatest convergence of rods onto rod bipolar cells?
• True or false: The amount of sodium channels closed in the initiation of phototransduction is directly proportional with how much the membrane potential changes.
• Two test flashes of 10 minutes of arc are shown 20 ms apart, and two test flashes of again 10 minutes of arc are shown next, this time 120 ms apart. Each emits 100 quanta. Which test flashes are seen as one: the 20 ms interval only, 120 ms interval only, or both?
• Wave 1 in a scotopic ERG corresponds to which label?
• Which cells mediate interactions between bipolar cells and ganglion cells?
• The very center of the fovea has no rods and is characterized by the highest density of cones. What is this region called?
• What photopigment(s) are in cones?
• Which three types of retinal cells are found in the middle layers as light passes through the retina?
• Which cells mediate interactions between photoreceptors and bipolar cells?
• What does ERG stand for?
• Is the b-wave positive or negative in an ERG?
• Which system has better spatial resolution?
• What makes up the optic nerve?
• A test flash of 5 minutes of arc is shown for 20 ms, and a test flash of 15 minutes of arc is shown next, also for 20 ms. Each emits 100 quanta. Which test flash is seen?
• If light enters the pupil through the edge to reach the retina, does that light appear brighter or dimmer?
• What mechanism enables triggering an action potential when a single synapse is not enough?
• How is the spectral sensitivity function for scotopic and photopic vision obtained?