Photoreceptors Practice Test

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