Sensory Systems Chapter 43 Complete Test Bank

Biology, 12e (Raven)

Chapter 43 Sensory Systems

1) All sensory input arrives at the central nervous system in the same form, as ________ propagated by afferent neurons. Perception of the type and intensity of a stimulus depends on which part of the brain the impulse projects to and the firing frequency of the sensory neuron.

A) action potentials

B) receptor potentials

C) reflexes

D) frequency localizations

E) thresholds

2) The simplest sensory receptors are ________ that respond to mechanical distortion, changes in temperature, or specific chemicals.

A) nociceptors

B) free nerve endings

C) gated channels

D) photoreceptors

E) ganglia

3) What sensory receptors sense stimuli that arise from within the body?

A) gustatory receptors

B) photoreceptors

C) interoreceptors

D) ampullae of Lorenzini

E) exteroreceptors

4) When membrane proteins on an olfactory neuron are stimulated by the binding of a specific chemical, what is the immediate result?

A) membrane depolarization

B) membrane repolarization

C) active ion transport

D) membrane hyperpolarization

E) neurotransmitter release

5) Which includes all of the components that make up the Organ of Corti?

A) the basilar membrane only

B) the tectorial and basilar membranes

C) hair cells and associated neurons only

D) hair cells and the tectorial membrane

E) hair cells and the basilar and tectorial membranes

6) The lateral line system provides ________ with a sense of "distant touch," enabling these animals to sense objects that reflect pressure waves and low-frequency vibrations.

A) adult amphibians

B) reptiles

C) birds

D) mammals

E) fish

7) Pit vipers are the only known vertebrates with an ability to detect a certain type of stimulus. What can these snakes sense?

A) infrared radiation

B) ultraviolet radiation

C) microwave radiation

D) visible light radiation

E) none of these

8) What are the receptors of sharks that can detect disturbances in electrical fields called?

A) Organs of Corti

B) pacinian corpuscles

C) lateral line canals

D) nodes of Ranvier

E) ampullae of Lorenzini

9) Which of the following receptors does not trigger depolarization of a sensory neuron?

A) mechanoreceptors

B) G-protein receptors

C) chemoreceptors

D) photoreceptors

E) exteroceptors and interoceptors

10) Which correctly represents the sequence of steps involved to convey sensory information to the CNS?

A) stimulation and ion flow through the synaptic cleft

B) neurotransmitter release and interpretation

C) neurotransmitter release and ion flow through the synaptic cleft

D) stimulation, transduction, transmission, and interpretation

E) stimulation, transmission, and neurotransmitter release

11) Which of the following stimuli do vertebrates NOT have a specialized receptor for?

A) hearing

B) taste

C) smell

D) humidity

E) vision

12) Which is NOT a stimulus that the simplest sensory receptors, free nerve endings, will respond to?

A) bending of the sensory neuron membrane

B) changes in temperature

C) changes in the oxygen content of the extracellular fluid

D) release of odorants from freshly baked bread

E) stretching of the sensory neuron membrane

13) Which is NOT a stimulus that exteroceptors can sense?

A) gravity

B) smell

C) light

D) muscle tension

E) sound

14) Which is NOT a stimulus that interoceptors can sense?

A) limb position

B) pain

C) gravity

D) body temperature

E) muscle length

15) Which of the following is NOT an example of a mechanoreceptor?

A) Meissner's corpuscles

B) Ruffini endings

C) Merkel cells

D) red corpuscles

E) Pacinian corpuscles

16) Cutaneous receptors are classified as interoceptors. These specialized skin receptors can respond to which of the following stimuli?

A) heat, cold, and light

B) pain, pressure, and sound

C) chemicals, light, and sound

D) heat, cold, pain, touch, and pressure

E) heat, cold, pain, pressure, light, and sound

17) What are the receptors called that transmit impulses that are perceived by the brain as pain?

A) baroreceptors

B) chemoreceptors

C) nociceptors

D) thermoreceptors

E) propioceptors

18) Which of the following stimuli will NOT activate a nociceptor?

A) extremes in temperature

B) very intense mechanical stimulation

C) specific chemicals in the extracellular fluid

D) chemicals released by injured cells

E) external odorant molecules

19) What are the sensory structures that enable invertebrates to determine the orientation of the body with respect to gravity called?

A) carotid bodies

B) statocysts

C) Ruffini endings

D) baroreceptors

E) interoceptors

20) Which of the following do humans NOT have taste buds specialized to sense?

A) salty

B) sour

C) sweet

D) vitamins

E) bitter

21) Rank the sensory receptors in order, from the ability to detect the widest variety of molecules, to the least variety of molecules (or none).

1. gustatory receptors

2. photoreceptors

3. olfactory receptors

4. TRP channel temperature receptors

22) Which of the following are components of vertebrate gravity receptors?

I-Utricle and saccule chambers of a membranous labyrinth.

II-Hair cells with stereocilia and kinocilium.

III-Hairlike processes embedded with otolith membrane, a gelatinous membrane containing calcium carbonate crystals.

IV-Peripheral chemoreceptors.

A) I and II only

B) II, III, and IV

C) I and IV only

D) I, II, and IV

E) I, II, and III

23) Which of the following constitute the vestibular apparatus?

A) saccule and utricle only

B) semicircular canals, saccule, and utricle

C) ampullae of Lorenzini

D) saccule, utricle, and Organ of Corti

E) saccule, utricle, and ventricle

24) What does the middle ear consist of?

A) three ossicle bones

B) the ear canal

C) the ear drum

D) the vestibular canal

E) the tympanic canal

25) Which sequence of events is required for the brain to interpret sound?

I. Vibration of the basilar membrane relative to the tectorial membrane causes cilia on hair cells to bend and triggers depolarization.

II. Hair cells stimulate the production of action potentials in sensory neurons that project to the brain.

III. Ganglion cell axons transmit action potentials to the occipital lobe.

A) II then I

B) III then I then II

C) III then I

D) I then II

E) I then II then III

26) Which animal became numerous and widespread by using sonar to enable a high level of activity in the dark?

A) bats

B) whales

C) owls

D) dolphins

E) shrews

27) In the vertebrate eye, what structure is light focused onto?

A) pupil

B) lens

C) retina

D) sclera

E) iris

28) Which is NOT a part of the vertebrate eye?

A) cornea

B) retina

C) iris

D) cochlea

E) pupil

29) In the vertebrate eye, what structure controls the amount of light that reaches the retina?

A) fovea

B) cornea

C) iris

D) lens

E) sclera

30) What is the photopigment in rod cells called?

A) photopsin

B) rhodopsin

C) opsin

D) carotene

E) melanin

31) Which of the following cells are NOT found in the retina?

A) rods

B) cones

C) bipolar cells

D) hair cells

E) ganglion cells

32) What are the short retinal photoreceptors responsible for color vision called?

A) rods

B) cones

C) bipolar cells

D) glial cells

E) ganglion cells

33) Color blindness is caused by heritable mutations in cone photoreceptors. How many cone types does the retina of a colorblind individual typically contain?

A) only one

B) two

C) three

D) four

E) five

34) What sequence of events leads to the perception of a visual scene? 

I. In response to light, retinal dissociates from rod and cone photopigments, hyperpolarizing the photoreceptor cells and leading to activation of bipolar neurons.

II. Action potentials are propagated through ganglion cells, whose axons project to the occipital lobe of the brain.

III. In response to light, rod and cone photoreceptors depolarize, causing increased release of neurotransmitter and activation of bipolar neurons.

A) I then III

B) III then II

C) III then I then II

D) I then II then III

E) I then II

35) What sensory equipment is required for an animal to have binocular vision?

A) eyes located to the sides of the head

B) forward-facing eyes

C) a camera-type eye with multiple lenses

D) infrared vision

E) ultraviolet vision

36) Which of the vertebrates senses is the least well understood?

A) electroreception

B) magnetoreception

C) vision

D) hearing

E) touch

37) Which is NOT an example of a stimulus sensed by an interoceptor?

A) temperature

B) vibration

C) pain

D) magnetism

E) touch

38) Choose the receptor that is NOT correctly matched with its function.

A) proprioceptor - monitors stretch of muscle fibers

B) baroreceptor - monitors hydrostatic pressure in blood vessels

C) nociceptor - transmits signals that the brain interprets as pain

D) chemoreceptor - perceives taste and smell stimuli

E) peripheral chemoreceptor - monitors the pH of the cerebrospinal fluid

39) Which of the following statements about the lateral line system is NOT correct?

A) allows fish to sense objects based on the pressure waves they produce

B) allows fish to sense objects based on the low-frequency vibrations they produce

C) allows fish to swim in synchrony with a school of other members of its species

D) provides the fish with the ability to see images

E) allows a blind cave fish to sense the water patterns flowing past its body

40) In what order will you encounter the following structures if you examine the human ear from the outside inward?

A) tympanic membrane → malleus →incus → stapes → oval window → cochlea

B) tympanic membrane → incus →malleus → stapes → oval window → cochlea

C) tympanic membrane → stapes →malleus → incus → oval window → cochlea

D) tympanic membrane → malleus →incus → stapes → cochlea →oval window

E) tympanic membrane → oval window → malleus →incus → stapes → cochlea

41) Which animal is NOT able to use sonar as a form of "lightless vision" to navigate in dark environments?

A) shrews

B) owls

C) bats

D) whales

E) dolphins

42) Where is the visual image in focus for a nearsighted individual?

A) behind the retina

B) in front of the retina

C) on the retina, but it appears blurred

D) at the lens, forming a shadow on the retina

E) on the retina, but it is upside down

43) The human retina is composed of three cell layers. Which represents the correct order of these layers, starting with the layer that is closest to the iris?

A) ganglion cells → bipolar cells → rods and cones

B) optic nerve cells → rods and cones → bipolar cells

C) rods and cones → bipolar cells → ganglion cells

D) bipolar cells → ganglion cells → rods and cones

E) rods and cones → optic nerve cells → bipolar cells

44) Which of the following animals does NOT have electroreceptors?

A) bony fish

B) sharks

C) duck-bill platypus

D) skates

E) pit viper snakes

45) Each type of cone cell is stimulated by a different color of light. In humans, a colorful scene is perceived as a combination of signals from three cone types. Which colors correspond to these three cones?

I-Red

II-Yellow

III-Orange

IV-Blue

V-Green

VI-Purple

A) I, II, and III

B) I, III, and IV

C) I, IV, and V

D) I, V, and VI

E) II, IV, and VI

46) Which of the following statements about hair cells is NOT true?

A) They are found in the mammalian ear.

B) They are found in the fish lateral line system.

C) They can be repaired if they rupture.

D) Bending of the cells triggers ion flow across the cell membrane.

E) Their structure includes stereocilia and a kinocilium.

47) Which of the following structures is found in a human eye, but NOT in an octopus eye?

A) retina

B) lens

C) optic nerve

D) blind spot

E) cones

48) Which taste modality does not involve activation of a G-protein coupled receptor?

A) bitter

B) sweet

C) umami

D) sour

E) all taste sensations involve GPCRs

49) What effect do high frequency sounds tend to have on the ear?

A) displace the whole length of the basilar membrane with a maximum near the apex

B) move only the basal portion of the basilar membrane

C) move only the apex portion of the basilar membrane

D) move only the portion of the basilar membrane between the basal portion and the apex

E) only move the tectorial membrane

50) The statoliths of a lobster are replaced with iron filings, and a strong magnetic field is produced at the top of its tank. How will the lobster respond?

A) Its dorsal surface will stick to the top of the tank and it will be unable to move.

B) It will turn upside down and grip the underside of the tank lid.

C) It will turn upside down and remain at the bottom of the tank.

D) It will not respond in any way.

E) It will continuously spin in circles.

Vision differs from the other senses in two interesting ways. Although most sensory receptor neurons are depolarized when the receive a stimulus, rod and cone cells become hyperpolarized when they receive light. When hyperpolarized, they stop releasing inhibitory neurotransmitter and allow the bipolar cells to fire. A second unusual aspect is that the vision circuit seems to be organized "backwards" — the light must pass through the layers of ganglion and bipolar cells to reach the rods and cones.

51) Which letter indicates the direction of incoming light in a typical vertebrate?

A) A

B) B

C) C

D) D

E) All of the directions are possible.

52) When a cone cell is stimulated by light, what will occur at the cell membrane?

A) excitation

B) inhibition

C) an action potential

D) hyperpolarization

E) depolarization

53) Which of type of information is NOT communicated by proprioceptors?

A) muscle temperature

B) limb movement

C) muscle position

D) muscle contraction

E) muscle stretch

54) What happens to a retinal photopigment when it captures a photon?

A) It releases an electron.

B) It fluoresces.

C) It changes shape.

D) It begins to vibrate.

E) It does nothing.

55) Which of the following statements regarding vision is NOT true?

A) Vertebrate rods and cones hyperpolarize in response to light.

B) Insects and birds can often see into the ultraviolet range.

C) Bright light will often produce action potentials in both rods and cones.

D) Rhodopsin is found in the membrane of rods.

56) Visual acuity is highest when an image is focused on what part of the retina?

A) rods outside the fovea

B) cones outside the fovea

C) rods within the fovea

D) cones within the fovea

E) anywhere, as long as there is ample light

Choose the letter that best describes the function of each receptor type. (You may use a letter more than once.)

A. tonic receptors located near the surface of the skin

B. pressure sensitive receptors deep in the subcutaneous layer

C. receptors on the face and fingertips sensitive to light touch

57) Pacinian corpuscle

58) Merkle cell

59) Ruffini corpuscle

60) Meissner's corpuscle

61) All of the varied sensations we experience are due to which three categories of sensory receptors?

A) visioceptor, audioceptor, olfactoceptor

B) exteroceptor, interoceptor, proprioceptor

C) mechanoreceptor, chemoreceptor, electromagnetic receptor

D) mechanoreceptor, olfactory receptor, photoreceptor

E) mechanoreceptor, chemoreceptor, nociceptor

62) True or false: Humans are unique among animals due to our highly-evolved repertoire of sensory receptors.

63) What difference in axonal signaling determines whether we experience a mild or a strong sensation?

A) amplitude of action potentials

B) frequency of action potentials

C) action potential threshold

D) conduction speed

E) amount of neurotransmitter released per vesicle

64) Since the optic nerve must pass through the retinal layer, we all have a blind spot devoid of light receptors. This normally goes unnoticed, since the brain attempts to compensate for missing sensory information by filling it in based on surrounding patterns. Which step of the sensory pathway is represented by perceptual filling-in of the physiological blind spot?

A) interpretation

B) stimulus

C) transduction into receptor potential

D) action potential transmission

65) What information would best help you distinguish what type of sensation a sensory neuron transmits?

A) the rate of action potential firing

B) the proteins it expresses most abundantly

C) the part of the brain it transmits signals to

D) the amplitude of action potentials

E) the diameter of the axon

66) What is the primary difference in how touch sensation and hearing sensation are conveyed?

A) the neurotransmitters secreted by the sensory neurons

B) the way that the axons physically connect to the brain stem

C) the shape of the sensory axons

D) the proteins that transduce the chemical signal in the brain

E) the part of the brain that receives the signal

Honeybees have an incredible ability to distinguish thousands of different odorant molecules, using their large repertoire of olfactory receptors. A wide variety of different types of chemicals can be detected as odorants -- they simply require olfactory neurons with a receptor that can bind the chemical and transduce that stimulus into a receptor potential.

67) Because small quantities of powerful explosives can be hidden easily, a sensor that could detect trace amounts of illicit chemicals would be a useful tool. What animal sensory modality is exquisitely sensitive to minute quantities of airborne chemicals?

A) olfaction

B) taste

C) vision

D) hearing

E) touch

68) Honeybees can detect a variety of odorants through olfactory receptors on their antennae. You genetically engineer a receptor to be gated by the explosive chemical TNT, and use a transgene to express the receptor in honeybee olfactory neurons. What would this provide to the bee?

A) the ability to taste TNT

B) it would have no effect

C) the ability to smell TNT

D) the ability to collect TNT molecules

E) the ability to see TNT

69) If genetically engineered bees could express a receptor for TNT in their olfactory neurons, what type of receptor would the TNT receptor be?

A) chemoreceptor

B) mechanoreceptor

C) electromagnetic receptor

D) it is a novel type of receptor

70) If genetically engineered bees could express a receptor for TNT in their olfactory neurons, how would the bees respond to the presence of TNT?

A) It would ignore the stimulus.

B) It would be attracted.

C) It would be repelled.

D) It would depend on which olfactory neuron expresses the transgene.

71) If genetically engineered bees could express a receptor for TNT in their olfactory neurons, how could the transgenic bees be useful for detecting explosives?

A) Watch for death of the bee when the neuron absorbs TNT.

B) Use MRI to monitor the brain activity of the bee.

C) Train bees to respond in a predictable way when the TNT neuron is activated by conditioning them to expect an associated food reward.

D) Grind up the bee's antennae for use in a TNT ELISA assay.

72) True or False: A single type of receptor is responsible for detecting all tactile pressure in humans.

73) What is the molecular basis of touch sensation?

A) Pressure on the skin squeezes out chemical signals from epidermal glands.

B) Cell membrane distortion opens touch receptors, creating a receptor potential.

C) Pressure damages the delicate strands of skin cell DNA, activating a complex signalling cascade.

D) Pressure on sensory axons bursts vesicles and causes neurotransmitter release.

74) Which of the following are tactile receptors? (Check all that apply.)

A) Merkle cell

B) ampullae of Lorenzini

C) node of Ranvier

D) Meissner corpuscle

E) Ruffini corpuscle

F) rod cell

G) Pacinian corpuscle

H) free nerve ending

J) ganglion cell

K) cone cell

75) True or False: There is only a single type of pain receptor.

76) Pain receptors are activated by tissue damage, but pain perception requires intact, functional neurons. How does this work?

A) Nociceptor neurons have special membrane repair mechanisms.

B) The nociceptor neuron only sends action potentials as it is dying.

C) The axon continues to fire action potentials despite damage to the cell body.

D) The neuron itself does not need to be damaged; it responds to signals released by nearby damaged cells.

TRP channels normally act as temperature sensors in the body — they are stimulus-gated ion channels, each specialized to open at various temperature thresholds. However, different TRP channels can also be gated by certain molecules such as capsaicin or menthol.

77) Why do we perceive chili peppers as "hot" and peppermint as "cold"?

A) It is a cultural convention to speak of chili peppers as hot and peppermint as cold.

B) Capsaicin and menthol act as agonists of TRP channels normally activated by temperature changes.

C) We are conditioned to think so because chili-containing foods are served hot, while mint-containing foods are served cold.

D) Neurons sensitive to heat or capsaicin project to nearby regions of the brain, while neurons sensitive to cold or menthol project to other adjacent regions.

E) Capsaicin transmits infrared energy, while menthol absorbs it.

78) What is the most likely hypothesis for the presence of TRP channel agonists in plants?

A) to speed up or slow down chemical reactions in the plant

B) to warm or cool the plant, depending on the season

C) to discourage feeding by herbivorous insects or mammals

D) to encourage human cultivation

79) You decide to perform an experiment to test this why plants possess TRP channel agonists. You first set up batches of plants in the field WITH or WITHOUT applied capsaicin or menthol. What parameter do you then measure?

A) photosynthetic rate

B) amount of leaf or fruit damage

C) metabolic rate

D) palatability to humans

80) In "The Disembodied Lady," neurologist Oliver Sacks tells the story of a patient who suffered a catastrophic loss of sensory function. She said, "I feel my body is blind and deaf to itself. . . . It has no sense of itself." The patient's nerve damage was strikingly specific. What single type of neuron most likely suffered damage?

A) gustatory receptors

B) proprioceptors

C) olfactory receptors

D) Meissner corpuscles

E) rods and cones

81) Nociceptors can respond to nearby tissue damage by sensing cytosolic factors released by damaged cells. Such "algogenic agents" can cause pain sensation even in the absence of tissue damage. What might be a practical use for such an agent?

A) a nonlethal riot control measure

B) an anesthetic drug

C) a treatment for damaged tissue

D) a tasty food additive

82) The discovery that ATP is a pain-signaling factor immediately suggested what possible therapeutic approach to alleviate chronic pain?

A) create large intracellular aggregates of ATP

B) treat with an ATP receptor antagonist

C) block the synthesis of ATP inside cells

D) use electric stimulation on pain centers of the brain

Hair cells are delicate sensors of sound, movement, and gravity. Since they are stimulated by movement of the stereocilia and kinocilium, these structures are vulnerable to damage when stimulus is too strong or sustained.

83) After years of listening to loud music on headphones, the cilia on Bob's hair cells are damaged. What is the result?

A) vestibular problems

B) hearing loss

C) vision problems

D) taste hallucinations

84) If the cilia on Bob's inner ear hair cells are damaged, what can be done to improve Bob's hearing, other than a hearing aid? 

A) transgenic expression of a cilia protein

B) minoxidil treatment

C) injection of microtubules into the cochlea

D) not much – there is currently no drug that can regenerate hair cells

85) Put the steps in the correct order for a birder hearing the call of a whip-poor-will.

1. malleus, incus, and stapes vibrate

2. action potentials travel down axons that represent different frequencies

3. pressure waves travel through fluid in the cochlea

4. basilar membrane vibrates in different regions for each note

5. cilia of hair cells bend in different regions for each note

6. auditory cortex interprets the pattern

7. bird sings "whip-poor-will"

8. sound waves travel to the birder's pinna and enter the canal

9. tympanic membrane vibrates

10. oval window vibrates

86) How is the lateral line of a fish similar to the ears of a human? (Check all that apply.)

A) cilia embedded in a gelatinous matrix

B) cochlea

C) hair cells

D) large external structures for capturing pressure waves

E) line of cells extends along length of the body

F) organ of Corti

G) pressure waves

H) sensory neurons

J) several kinocilia and one stereocilium

K) several stereocilia and one kinocilium

Hair cells are delicate sensors of sound, movement, and gravity. They are stimulated by movement of the stereocilia — which are actually microvilli — and the single kinocilium, which is a true cilium.

87) One patient at your audiology clinic has an actin defect, and another patient has a microtubule defect. How might these defects affect the function of their hair cells in hearing?

A) Neither actin nor microtubule mutations will disrupt hair cell cilia function.

B) Only the actin mutation will affect hair cell cilia function.

C) Only the microtubule mutation will affect hair cell cilia function.

D) Both can create problems in hair cell cilia function.

88) One patient at your audiology clinic has an actin defect, and another patient has a microtubule defect. What sense other than hearing may be affected in these patients?

A) smell

B) taste

C) balance

D) touch

E) proprioception

89) Mutations in the DFNA20/26 locus, which codes for the actin gamma 1 protein, are associated with congenital deafness. An irate senator complains that government money is being wasted on studies of this mutant gene -- in yeast! "I am no biologist," says the senator, "but I am pretty sure yeast don't have ears." How do you respond?

A) "You are right, Senator -- yeast do not have ears. We should revoke the funding immediately."

B) "We can learn valuable information about the structure of the mutant protein by expressing it in yeast. It is difficult to collect large amounts of actin from tiny hair cells, and unethical to collect it from human patients."

C) "We can learn valuable information about the transcription of the mutant gene in yeast. It is much more difficult to study transcription in human cells."

D) "We can learn valuable information about sound transmission through the mutant yeast. By placing a speaker against a yeast vial and recording sound from the other side, we can infer how the mutant actin affects sound waves."

90) As CO2 builds up in the atmosphere it also accumulates in the oceans, causing acidification. This poses a challenge to marine creatures that rely on calcium carbonate deposition such as corals, mollusks, and even fish, which use it to form otoliths. Researchers investigated whether otolith deposition was impaired at low pH, and were surprised to find that otoliths were actually larger in this condition. This means that, while coping with global climate change, at least fish will still be able to maintain which sense(s)?

A) feeling pain

B) vision

C) taste

D) olfaction

E) hearing and balance

91) What are the categories of taste sensation?

A) sweet, salty, sour, creamy, umami

B) sweet, sour, salty, bitter, umami

C) sweet, salty, bitter, chocolate, coffee

D) sweet, sour, salty, creamy, savory

92) You make a knockout of a gene involved in neurological development, and find that the mice have malformed semicircular canals. Instead of being orthogonal (at right angles) to each other, they are parallel. What aberrant behavior might you see in these mice?

A) overeating

B) falling over

C) not startling to sudden noise

D) unable to respond to a call to locate another mouse

E) low muscle tone

93) In 1908, chemist Kikunae Ikeda identified a new taste modality he called "umami", or "delicious" in Japanese. It gives a savory flavor to meat, seaweed, and tomatoes. What molecule is responsible for umami?

A) Na+ ions

B) H+ ions

C) glutamate

D) Mg+2 ions

E) Fe+2 ions

94) Beta-N-Methylamino-L-Alanine, or BMAA, is a glutamate receptor agonist produced by cyanobacteria. Since Glu is an excitatory neurotransmitter, it is not surprising that BMAA is associated with neurological damage. Buildup of BMAA in fruit bats was hypothesized to cause neurodegenerative disease in islanders that fed on the bats. A recent study found high levels of BMAA in sharks, suggesting that consumption of shark fin soup is also dangerous. The researchers suggested that a secondary effect of BMAA may actually make these hazardous foods surprisingly desirable. What might this be?

A) Since BMAA is a Glu receptor agonist, it promotes incorporation of Glu into proteins, and has health-promoting effects.

B) Since BMAA is derived from cyanobacteria, it provides unique nutrients not found in the animal or plant kingdom.

C) Since BMAA is a Glu receptor agonist, it imparts a strong umami flavor that makes food more delicious.

D) Since BMAA contains alanine, it improves protein synthesis by providing this rare nutrient.

Unlike sweet, salty, sour, or umami, the "bitter" category of tastants includes wide structural variety of detected molecules. Multiple receptors are required to sense the different bitter tastants. What do they have in common? Bitter taste is thought to have evolved as a warning system for toxic compounds.

95) The bitter receptor hTAS2R38 is activated by glucosinolates found in plants such as turnips and broccoli. The gene variant a person has determines how sensitive their neurons are to these compounds. What would you predict for people who have the high-sensitivity variant of hTAS2R38?

A) They will not easily digest turnips and broccoli.

B) They will have to eat more turnips and broccoli to get the same flavor.

C) They will dislike turnips and broccoli.

D) They will become allergic to turnips and broccoli.

96) The bitter receptor hTAS2R38 is activated by glucosinolates found in plants such as turnips and broccoli. Glucosinolates can block synthesis and transport of iodine. Before the advent of iodized salt, this was a particular problem in areas of the world that are naturally low in iodine. Why might the human population include different variants of the hTAS2R38 gene?

A) Areas of high iodine are generally coastal, and turnips and broccoli are not easily grown there.

B) Iodine created mutations in the hTAS2R38 gene.

C) Where iodine was low, eating plants rich in glucosinolates helped people metabolize iodine, but where iodine was high they avoided such foods.

D) Where iodine was low, it was important to avoid foods with glucosinolates, but where iodine was plentiful, palatability of a wider range of plants was beneficial.

97) Which sensory modality responds to the broadest range of molecules?

A) TRP channels

B) Taste

C) Smell

D) Vision

E) Touch

98) Researchers studying olfactory and taste receptors have stumbled upon an unusual phenomenon. These receptor proteins are sometimes expressed in other animal tissues in addition to the nose or tongue. For example, the sweet taste receptor T1R2 is expressed in the pancreas. Suggest the best possible explanation for these findings.

A) Damaged receptors are recycled by the body and end up in waste-disposal organs.

B) Control of protein expression is imperfect. As long as a receptor doesn't interfere with organ function, expression will not be selected against.

C) Chemoreceptors bind molecules that help the body sense and respond to internal phenomena, such as sugar levels in the blood.

D) Techniques used to visualize protein expression are imperfect and may lead to false positive results.

Pax6 is a transcription factor noted for its unique role in specifying eye development across the animal kingdom. A homologous gene known as eyeless specifies eyes in Drosophila, and misexpression of mouse Pax6 can cause ectopic eyes in flies! This creates a quandary -- how can we explain the universality of the master regulatory gene for eye development, with the striking variability of eye anatomy in different phyla?

99) Misexpression of the Pax6 gene was shown to promote eye development in both vertebrates and invertebrates. The authors of this study suggested that this was evidence that eyes evolved only once. What other evidence contradicts this view?

A) Invertebrates normally have only simple eyespots.

B) Many different transcription factors can initiate eye development when misexpressed.

C) While the anatomy of all animal eyes is the same, lens proteins vary greatly.

D) The anatomical structure of insect, mollusk, and vertebrate eyes are quite different.

100) What statement best summarizes the evolutionary history of eyes?

A) Development of light-sensing organs evolved once, but several eye structures evolved separately.

B) Eyes evolved once and were slightly modified in different phyla.

C) Eyes evolved separately in each phylum from an ancestor with no ability to detect light.

D) Light-detection organs can develop with very little developmental constraint.

101) Peripheral shadows or flashes of light can be a sign that the retina is peeling away from the layer below. Why is detachment of the retina a medical emergency?

A) It contains the photoreceptor cells that respond to light.

B) It is crucial for focusing the image.

C) It secretes tears that bathe and protect the eyeball.

D) It is a sphincter muscle that controls light transmission.

102) After your eye exam, the optometrist breaks the bad news: "Your lens is a little too flat, and as a result it is focuses the image just in front of your retina." What kind of vision do you have?

A) astigmatism

B) nearsighted

C) farsighted

D) night-blindness

103) Why are carrots said to be good for you?

A) That is just an old wive's tale.

B) Beta-carotene, the orange pigment in carrots, is a precursor to Vitamin A and retinal, the cofactor in photopigments.

C) Beta-carotene, the orange pigment in carrots, is necessary to form lens proteins.

D) Carrots have large amounts of glutamate, a neurotransmitter that activates sensory neurons.

104) At night, faint objects are best seen when not looked at directly. What is the basis of this phenomenon?

A) Rhodopsin is transported away from the fovea at night.

B) Cis-retinal builds up in the fovea at night, and is degraded during the day.

C) Cone photoreceptors are most sensitive in dim light, and few cones are present in the fovea.

D) Rod photoreceptors are most sensitive in dim light, and few rods are present in the fovea.

Match the specialized sense to the role it plays.

A) help long-distance migration

B) sense electrical currents from muscles

C) sense infrared radiation in prey

105) pit organs

106) ampullae of Lorenzini

107) magnetic field receptors

108) The ampullae of Lorenzini are jelly-filled pores that allow fish to sense electromagnetic currents. What is an important property of the jelly in these organs?

A) It secretes pheromones for conspecifics.

B) It is a good electrical conductor.

C) It contains gustatory receptors.

D) It is an electrical insulator.

109) A research strain of mice has a mutation that causes voltage-gated sodium channels to take longer to return to the active state after a spike. What is the likely consequence for transduction of sensory stimuli?

A) There will be no effect on sensory perception, because sensory information relies on stimulus-gated ion channels and not voltage-gated ion channels.

B) Sensory information will be incorrectly perceived as high intensity stimuli, due to the increased frequency of action potentials.

C) The mutation will interfere with the ability of stimuli to create receptor potentials, and thus the neuron will fire with slow, broad action potentials, giving the animal enhanced sensory perception.

D) Due to a longer refractory period, the neuron will be unable to conduct high frequency action potentials, and thus will not effectively transmit information about strong stimuli.

110) Which of the following statements would explains the importance of Pax gene families in animals?

A) Pax genes are believed to grow legs in fruit flies.

B) Pax genes are needed to form chemoreceptors in animals.

C) Pax genes are completely unrelated and found in a variety of animals by coincidence.

D) Pax gene families are found in a variety of animal phyla and help to show the evolutionary relationship of eye development.