Lecture 5: sensing the environment II Flashcards
What does “seeing” mean from the perspective of vision?
A) Detecting sound waves in the environment
B) Detecting wavelengths of the electromagnetic spectrum
C) Detecting electric fields from other organisms
D) Detecting radio waves through water
Correct Answer: B) Detecting wavelengths in the electromagnetic spectrum
What is the visible light range for human vision?
A) 100–350 nm
B) 350–750 nm
C) 750–1,000 nm
D) 10⁻³–10¹ m
Correct Answer: B) 350–750 nm
What does the narrow band of visible light suggest about humans?
A) We evolved in a terrestrial environment.
B) We evolved in aquatic environments.
C) We have the ability to detect microwaves.
D) We can perceive electric fields like sharks.
Correct Answer: B) We evolved in aquatic environments.
Why can humans not see microwaves?
A) Microwaves are too fast to detect.
B) Microwaves experience significant attenuation in water.
C) Microwaves are too weak to interact with photoreceptor cells.
D) Microwaves fall outside the electromagnetic spectrum.
Correct Answer: B) Microwaves experience significant attenuation in water.
What type of radiation do some aquatic organisms, like sharks, detect?
A) Visible light
B) Electric fields
C) Microwaves
D) Radio waves
Correct Answer: B) Electric fields
What is the main function of stereocilia in hair cells?
A) To release neurotransmitters
B) To detect mechanical stimuli
C) To produce action potentials
D) To amplify sound waves
Correct Answer: B) To detect mechanical stimuli
What happens to hair cells when stereocilia are displaced toward the kinocilium?
A) The cell hyperpolarizes.
B) The cell depolarizes.
C) The cell remains at resting potential.
D) Neurotransmitter release decreases.
Correct Answer: B) The cell depolarizes.
What is the “dark current” in rod cells?
A) Continuous influx of K⁺ in the light
B) Continuous influx of Na⁺ in the dark
C) Continuous efflux of Na⁺ in the dark
D) Closing of cGMP-gated channels
Correct Answer: B) Continuous influx of Na⁺ in the dark
What happens to rod cells in response to bright light?
A) They depolarize, increasing neurotransmitter release.
B) They hyperpolarize, reducing neurotransmitter release.
C) cGMP-gated Na⁺ channels open.
D) The resting membrane potential becomes less negative.
Correct Answer: B) They hyperpolarize, reducing neurotransmitter release.
Which photoreceptor pigment is activated in rods by light?
A) Rhodopsin
B) Opsin
C) Photopsin
D) Melanopsin
Correct Answer: A) Rhodopsin
Why does light hyperpolarize rod cells?
A) It opens K⁺ channels.
B) It reduces cGMP, closing Na⁺ channels.
C) It increases the activity of Na⁺/K⁺ ATPase pumps.
D) It activates calcium influx.
Correct Answer: B) It reduces cGMP, closing Na⁺ channels.
Explain the process of phototransduction in rod cells, starting from light absorption. Explain each of the 6 steps.
- Light is absorbed → Rhodopsin activated
✅ 2. Retinal changes from cis to trans → Rhodopsin fully activated
✅ 3. Rhodopsin activates transducin (G-protein)
✅ 4. Transducin activates phosphodiesterase (PDE)
✅ 5. PDE breaks down cGMP → Na⁺ channels close → Hyperpolarization
✅ 6. No Ca²⁺ entry → No neurotransmitter release (this means brain gets signal that we are percieving dim lighting - lack of neurotransmitter is perceived as light - dim light in this case)
What is photoreception?
A) The ability to respond to sound waves
B) The ability to detect and respond to light
C) The process of producing photons
D) The process of forming visual pigments
Correct Answer: B) The ability to detect and respond to light
Why did photoreception arise early in evolution?
A) Organisms needed to detect electric fields.
B) Sunlight was a weak selective force.
C) Sunlight was a strong selective force.
D) Light-sensitive proteins were absent in early organisms.
Correct Answer: C) Sunlight was a strong selective force
What allows photoreception to be possible in most organisms?
A) Clusters of photoreceptive organs
B) The presence of light-sensitive proteins called photopigments
C) High concentrations of neurotransmitters
D) The production of photons by photoreceptor cells
Correct Answer: B) The presence of light-sensitive proteins called photopigments
What happens to photopigments when exposed to light?
A) They amplify photons.
B) They change conformation.
C) They produce ATP.
D) They are destroyed.
Correct Answer: B) They change conformation
What is the primary function of photoreceptor cells?
A) To produce light
B) To convert photons into electrical signals
C) To increase cGMP levels
D) To cluster into sensory neurons
Correct Answer: B) To convert photons into electrical signals
Where are photoreceptor cells commonly found?
A) In clusters within sensory organs such as the eyes
B) Spread evenly across the entire body
C) Only in aquatic organisms
D) Only in organisms exposed to UV radiation
Correct Answer: A) In clusters within sensory organs such as the eyes
Which of the following statements about photoreceptor cells is true?
A) They are insensitive to light.
B) They directly produce neurotransmitters.
C) They are responsible for transducing photons into electrical signals.
D) They are only present in animals with complex eyes.
Correct Answer: C) They are responsible for transducing photons into electrical signals.
Which of the following statements about ciliary photoreceptors is TRUE?
A) They are found primarily in invertebrates.
B) They rely on microvilli to detect light.
C) They are the main photoreceptors in vertebrates.
D) They are only found in aquatic organisms.
Correct Answer: C) They are the main photoreceptors in vertebrates.
What are rhabdomeric photoreceptors primarily associated with?
A) Vertebrates
B) Invertebrates
C) Mammals only
D) Fish and amphibians
Correct Answer: B) Invertebrates
Which structural feature is associated with rhabdomeric photoreceptors?
A) Microvilli
B) Cilia
C) Photopigments without membranes
D) Chloroplasts
Correct Answer: A) Microvilli
Which of the following best describes ciliary photoreceptors?
A) They rely on microvilli for light detection.
B) They have a single cilium with a highly folded membrane.
C) They are only found in invertebrates.
D) They lack photopigments.
Correct Answer: B) They have a single cilium with a highly folded membrane.
What is the primary function of the cilium in ciliary photoreceptors?
A) To generate action potentials.
B) To provide structural support.
C) To house photopigments for detecting light.
D) To process neurotransmitter release.
Correct Answer: C) To house photopigments for detecting light.
Which of the following statements about mammalian photoreceptors is TRUE?
A) Cones are specialized for dim light and black-and-white vision.
B) Rods are used for detecting colors in bright light.
C) Mammals have two types of ciliary photoreceptors: rods and cones.
D) Both rods and cones function equally well in bright light.
Correct Answer: C) Mammals have two types of ciliary photoreceptors: rods and cones.
Which of the following is FALSE about cones and rods?
A) Cones are responsible for color vision and function best in bright light.
B) Rods are specialized for dim light and black-and-white vision.
C) Rods are less important than cones in nocturnal animals.
D) Cones are less sensitive to light than rods.
Correct Answer: C) Rods are less important than cones in nocturnal animals.
What distinguishes rods from cones?
A) Rods function in bright light, while cones function in dim light.
B) Cones are used for detecting color and bright light, while rods are used for dim light and black-and-white shades.
C) Rods are present in invertebrates, while cones are exclusive to vertebrates.
D) Cones rely on microvilli, while rods rely on a single cilium.
Correct Answer: B) Cones are used for detecting color and bright light, while rods are used for dim light and black-and-white shades.
Which of the following is found in the outer segment of rods and cones?
A) Nucleus
B) Synaptic vesicles
C) Discs with photopigments
D) Mitochondria
Correct Answer: C) Discs with photopigments
Which of the following is NOT a shared feature of rods and cones?
A) Both are receptor cells.
B) Both contain outer segments with discs that house photopigments.
C) Both have synaptic terminals at the base.
D) Rods are used for color vision, while cones are used for dim light.
Correct Answer: D) Rods are used for color vision, while cones are used for dim light.
Where are the nucleus and organelles located in rods and cones?
A) In the outer segment
B) In the inner segment
C) In the synaptic terminals
D) In the photopigment discs
Correct Answer: B) In the inner segment
Which of the following statements about rods and cones is FALSE?
A) Rods and cones share similar structural features, including outer and inner segments.
B) The outer segment contains discs that house photopigments.
C) Synaptic terminals are located at the top of the cell.
D) Rods are more extensively studied than cones.
correct Answer: C) Synaptic terminals are located at the top of the cell.
Which of the following is a characteristic of rods?
A) Faster response time than cones
B) Detect specific color wavelengths
C) High sensitivity in low light
D) Found in high numbers in diurnal animals
Correct Answer: C) High sensitivity in low light
Why do nocturnal animals have a high number of rods?
A) Rods are more sensitive to color.
B) Rods have higher sensitivity to dim light.
C) Rods saturate in bright light.
D) Rods require photopigments for high-speed responses.
Correct Answer: B) Rods have higher sensitivity to dim light.
Which of the following is FALSE about frogs’ photoreceptors?
A) Frogs only have rods but can still detect color.
B) Frogs rely on cones for color detection.
C) Frogs demonstrate diversity in the shape of rods and cones.
D) Frogs use photopigment properties to detect color.
Correct Answer: B) Frogs rely on cones for color detection.
What is a unique feature of rods compared to cones?
A) Ability to detect multiple colors.
B) Faster response times.
C) Greater amounts of photopigment.
D) Exclusively found in diurnal animals.
Correct Answer: C) Greater amounts of photopigment.
What are the two components of a photopigment?
A) Retinal and vitamin A
B) Chromophore and G-protein coupled receptor
C) Rhodopsin and opsin
D) Chromophore and rhodopsin
Correct Answer: B) Chromophore and G-protein coupled receptor
What is a chromophore?
A) A protein responsible for initiating the phototransduction cascade
B) A molecule that absorbs light and is a derivative of vitamin A
C) A protein that stabilizes photoreceptor cells
D) A molecule that reflects light to enhance vision
Correct Answer: B) A molecule that absorbs light and is a derivative of vitamin A
Which of the following is TRUE about rhodopsin?
A) It is a chromophore by itself.
B) It consists of retinal and opsin.
C) It is found only in cones.
D) It does not vary in sensitivity to different wavelengths.
Correct Answer: B) It consists of retinal and opsin.
Which of the following is FALSE about photopigments?
A) Photopigments consist of a chromophore and a G-protein coupled receptor.
B) Rhodopsin is a dominant photopigment found in animals.
C) Retinal, a chromophore, is derived from vitamin A.
D) Photopigments do not change shape in response to light.
Correct Answer: D) Photopigments do not change shape in response to light.
What happens when light interacts with rhodopsin?
A) Retinal is released into the extracellular environment.
B) Retinal changes its shape, initiating a phototransduction cascade.
C) Opsin becomes inactive and ceases signal transduction.
D) G-proteins are inhibited, halting the visual signal.
Correct Answer: B) Retinal changes its shape, initiating a phototransduction cascade.
What family of genes does the G-protein coupled receptor in photopigments belong to?
A) Rhodopsin gene family
B) Retinal gene family
C) Opsin gene family
D) Phototransduction gene family
Correct Answer: C) Opsin gene family
What happens to 11-cis retinal when it absorbs a photon of light?
A) It is converted to all-trans retinal.
B) It is degraded into vitamin A.
C) It remains unchanged.
D) It is converted to an inactive form.
Correct Answer: A) It is converted to all-trans retinal.
What is required for the conversion of all-trans retinal back to 11-cis retinal?
A) GTP
B) ATP
C) ADP
D) Photons of light
Correct Answer: B) ATP
Why might it take time to adjust when moving from bright light into a dark room?
A) The rods need time to regenerate photopigments as all-trans retinal is converted back to 11-cis retinal.
B) Cones are overactive in low-light conditions.
C) All-trans retinal degrades completely in low light.
D) The photoreceptor cells stop functioning in the dark.
Correct Answer: A) The rods need time to regenerate photopigments as all-trans retinal is converted back to 11-cis retinal.
Which of the following statements about retinal is FALSE?
A) 11-cis retinal converts to all-trans retinal when exposed to light.
B) ATP is required to convert all-trans retinal back to 11-cis retinal.
C) Retinal undergoes a bleaching process after isomerization.
D) The conversion of 11-cis retinal to all-trans retinal occurs in the absence of light.
Correct Answer: D) The conversion of 11-cis retinal to all-trans retinal occurs in the absence of light.
What is the effect of light on photoreceptor cells?
A) Light depolarizes the membrane.
B) Light opens cation channels.
C) Light hyperpolarizes the membrane.
D) Light has no effect on photoreceptor cells.
Correct Answer: C) Light hyperpolarizes the membrane.
How does light cause hyperpolarization in photoreceptor cells?
A) By opening cGMP-gated Na⁺ channels
B) By increasing cation influx
C) By closing cGMP-gated Na⁺ channels
D) By depolarizing cation channels
Correct Answer: C) By closing cGMP-gated Na⁺ channels
Which of the following stimuli causes the greatest hyperpolarization?
A) Dim light stimulus
B) Medium light stimulus
C) Bright light stimulus
D) No light
Correct Answer: C) Bright light stimulus
Which of the following statements about phototransduction is FALSE?
A) Light hyperpolarizes photoreceptor cells.
B) Phototransduction closes cation channels in response to light.
C) Dim light produces a slight hyperpolarization.
D) Hyperpolarization leads to the opening of cGMP-gated Na⁺ channels.
Correct Answer: D) Hyperpolarization leads to the opening of cGMP-gated Na⁺ channels.
What is the role of phosphodiesterase (PDE) in phototransduction?
A) It opens Na⁺ channels.
B) It converts cGMP to GMP.
C) It increases cGMP levels.
D) It hyperpolarizes the photoreceptor directly.
Correct Answer: B) It converts cGMP to GMP.
What does activated opsin do during phototransduction?
A) It binds directly to cGMP.
B) It activates transducin, a G protein.
C) It increases the levels of cGMP.
D) It opens cGMP-gated Na⁺ channels.
Correct Answer: B) It activates transducin, a G protein.
Which of the following statements about phototransduction is TRUE?
A) Light leads to the opening of cGMP-gated Na⁺ channels.
B) The cell becomes depolarized in response to light.
C) Less neurotransmitter is released when the cell is hyperpolarized.
D) PDE converts GMP into cGMP, opening Na⁺ channels.
Correct Answer: C) Less neurotransmitter is released when the cell is hyperpolarized.
Which of the following is FALSE about phototransduction?
A) Light converts 11-cis retinal into all-trans retinal.
B) Transducin activates phosphodiesterase (PDE).
C) Hyperpolarization increases neurotransmitter release.
D) Reduction in cGMP causes cGMP-gated Na⁺ channels to close.
Correct Answer: C) Hyperpolarization increases neurotransmitter release.
Why do rod cells hyperpolarize when exposed to light? Explain the changes in ion channel activity, membrane potential, and neurotransmitter release.
In the presence of light, rhodopsin is activated, leading to the conversion of 11-cis retinal to all-trans retinal.
Activated rhodopsin triggers a cascade where transducin (a G-protein) activates phosphodiesterase (PDE).
PDE reduces cGMP levels by converting it to GMP.
The reduction in cGMP causes cGMP-gated Na⁺ channels to close, stopping the influx of sodium ions (Na⁺).
Potassium (K⁺) continues to leak out through potassium channels, making the inside of the cell more negative.
This unbalanced potassium efflux causes the cell to hyperpolarize, lowering the membrane potential to around -70 mV.
Hyperpolarization causes voltage-gated calcium (Ca²⁺) channels in the synaptic terminal to close.
The decrease in calcium influx reduces the release of the neurotransmitters, signaling the presence of light to downstream neurons.
Why do rod cells remain depolarized in the dark? Explain the role of ion channel activity, membrane potential, and neurotransmitter release.
In the dark, cGMP levels are high because no light is present to activate the phototransduction cascade.
High cGMP levels keep cGMP-gated Na⁺ channels open, allowing sodium ions (Na⁺) to flow into the outer segment of the rod cell.
This inward Na⁺ current, known as the dark current, is balanced by the continuous efflux of potassium (K⁺) through K⁺ leak channels in the inner segment.
The membrane potential is maintained at a depolarized state of about -35 mV.
Depolarization keeps voltage-gated calcium (Ca²⁺) channels in the synaptic terminal open.
The influx of calcium ions allows the continuous release of neurotransmitters, which signals the absence of light to downstream neurons.
Which type of eye is the simplest and found in barnacles?
A) Flat-sheet eye
B) Cup-shaped eye
C) Vesicular eye
D) Convex eye
Correct Answer: A) Flat-sheet eye
Which type of eye allows for better shape distinction but lets in less light?
A) Flat-sheet eye
B) Cup-shaped eye
C) Vesicular eye
D) Compound eye
Correct Answer: B) Cup-shaped eye
What is a distinguishing feature of the vesicular eye?
A) It is dome-shaped with afferent neurons.
B) It has a lens to focus light on the retina.
C) It creates a mosaic image using ommatidia.
D) It is the simplest form of an eye.
Correct Answer: B) It has a lens to focus light on the retina.
What type of eye is found in insects?
A) Flat-sheet eye
B) Cup-shaped eye
C) Vesicular eye
D) Convex eye
Correct Answer: D) Convex eye
What are the multicellular units that make up a compound eye called?
A) Retinas
B) Ommatidia
C) Pigment layers
D) Photoreceptors
Correct Answer: B) Ommatidia
Which of the following is TRUE about ommatidia?
A) Each ommatidium lacks its own lens and cornea.
B) Ommatidia collectively create a mosaic image.
C) Ommatidia are present in vesicular eyes.
D) Each ommatidium processes color vision exclusively.
Correct Answer: B) Ommatidia collectively create a mosaic image.
How does the number of ommatidia vary across species?
A) All species have approximately the same number.
B) The number ranges from 1 to 25,000 depending on the species.
C) Larger animals always have fewer ommatidia.
D) Dragonflies typically have fewer ommatidia than ants.
Correct Answer: B) The number ranges from 1 to 25,000 depending on the species.
Which of the following species is most likely to have a convex eye?
A) Barnacle
B) Squid
C) Dragonfly
D) Cephalopod
Correct Answer: C) Dragonfly
