Ch. 14

Question 1

1. The conversion of stimulus energy into an electrical signal is known as
   a. transmutation.
   b. transference.
   c. transduction.
   d. an action potential.
   e. a graded potential.

Answer 1

C

Question 2

2. Which of the following receptors does not appear to use an ionotropic mechanism of signal transduction?
   a. Photoreceptors
   b. Vestibular receptors
   c. Mechanoreceptors
   d. Thermoreceptors
   e. Auditory receptors

Answer 2

A

Question 3

3. “The sensory modality or quality of sensation associated with a stimulus depends solely on which receptor cells are stimulated, rather than on how they are stimulated.” This generalization is known as the
   a. brain partitioning principle.
   b. principle of pathway analysis.
   c. regional cortex principle.
   d. principle of sensory organization.
   e. principle of labeled lines.

Answer 3

E

Question 4

4. Which of the following senses is not based on direct ionotropic activation via stretch?
   a. Insect touch
   b. Vertebrate touch
   c. Insect hearing
   d. Vertebrate hearing
   e. Insect vision

Answer 4

E

Question 5

7. In insects, the most common form of auditory organ is the
   a. tympanal organ.
   b. statocyst.
   c. cochlea.
   d. bristle sensillum.
   e. hair cell.

Answer 5

A

Question 6

8. Which of the following statements regarding the vertebrate hair cell is false?
   a. The vertebrate hair cell is an epithelial cell.
   b. Displacement toward the kinocilium produces a depolarization.
   c. Displacement away from the kinocilium produces a hyperpolarization.
   d. When displaced enough toward the kinocilium, the hair cell will produce a train of action potentials.
   e. Hair cells are found in the lateral line system of fish.

Answer 6

D

Question 7

9. Which of the following does not contribute to the transduction of sound qualities?
   a. The degree of hair cell bending
   b. The direction of hair cell bending
   c. The number of hair cells that are bending
   d. The location of the hair cells that are bending
   e. All of the above contribute to the transduction of sound qualities.

Answer 7

E

Question 8

10. Which of the following statements best describes the vertebrate vestibular system?
    a. Three semicircular canals detect movement via fluid that stimulates hair cells in the crista ampullaris.
    b. A circular canal detects movement via fluid that stimulates the oval window.
    c. Four canals, including the cochlea, detect indirect movement of hair cells.
    d. The incus, malleus, and stapes detect movement by amplifying sound to the oval window.
    e. The Eustachian tube detects movement via air that bends the associated hair cells.

Answer 8

A

Question 9

11. Which of the following statements regarding the basilar membrane is false?
    a. It separates the cochlea into an upper chamber and a lower chamber.
    b. It vibrates during sound transduction.
    c. It is widest at its basal end and narrowest at its apical end.
    d. It is stiffer at its basal end and more compliant near its apical end.
    e. It responds maximally to high frequency sounds toward its basal end.

Answer 9

C

Question 10

12. In the ear, low-frequency sounds tend to displace
    a. the whole length of the basilar membrane equally.
    b. mainly the basal portion (oval window end) of the basilar membrane.
    c. mainly the apex portion of the basilar membrane.
    d. only the portion of the basilar membrane between the basal portion and the apex.
    e. None of the above; low-frequency sounds do not displace the basilar membrane.

Answer 10

C

Question 11

13. The major source of auditory input to the brain comes from _______ hair cell signals.
    a. lateral line
    b. semicircular canal
    c. outer
    d. inner
    e. all

Answer 11

D

Question 12

14. Which of the following statement about bat navigation is true?
    a. Bats emit high-frequency sound pulses and detect the echoes reflected by the objects around them.
    b. Bats emit ultra-low-frequency sound pulses and detect the echoes reflected by the objects around them.
    c. In addition to detecting echoes from sound emissions, bats have keen night vision.
    d. Bats navigate by detecting sounds from animals and those reflected by the objects around them.
    e. All of the above

Answer 12

A

Question 13

15. Which of the following statements regarding fish taste is true?
    a. Fish taste buds are structurally similar to mammalian taste buds.
    b. Fish have taste buds in their mouth.
    c. Fish have taste buds on their skin.
    d. Fish have separate organs of taste and smell.
    e. All of the above

Answer 13

E

Question 14

16. The family of GPCRs that sense bitter compounds is much larger and more disparate in amino acid sequence than those that sense sweet or umami. Why might this be adaptive?
    a. Bitter receptors do not have to be as sensitive as those for sweet or umami.
    b. The ability to distinguish between many bitter compounds allows the animal to eat the one most agreeable to its digestive system.
    c. Bitter compounds are usually toxic, and so the ability to sense a wide variety of them is protective.
    d. Bitter compounds usually contain dense calories, which help a species survive and thrive.
    e. None of the above; it is unlikely to be adaptive.

Answer 14

C

Question 15

17. Which of the following sense perceptions depends on a metabotropic mechanism for initial signal transduction?
    a. Auditory reception
    b. Touch
    c. Bitter taste
    d. Acceleration
    e. Salty taste

Answer 15

C

Question 16

20. Which of the following statements regarding vertebrate olfactory receptor cells is true?
    a. They are epithelial cells.
    b. Their axons reside in the mucous layer.
    c. They have fine, myelinated axons.
    d. They undergo continuous turnover (die and are replaced).
    e. Their axons are among the largest axons in the nervous system.

Answer 16

D

Question 17

24. In the mechanism of vertebrate olfaction, a G protein activates the enzyme
    a. cGMP phosphodiesterase.
    b. phospholipase C.
    c. rhodopsin.
    d. transducin.
    e. adenylyl cyclase.

Answer 17

E

Question 18

25. Which of the following best describes the ion movement on the cilium of the olfactory receptor cell in vertebrate olfaction?
    a. Na+ enters the cell.
    b. Na+ enters the cell and K+ leaves the cell.
    c. Cl‒ moves out of the cell.
    d. Na+ and Ca2+ enter the cell.
    e. Na+ and Ca2+ move into the cell and Cl‒ moves out of the cell.

Answer 18

E

Question 19

26. Which of the following statements about the mammalian vomeronasal organ is true?
    a. It increases the sensitivity of the olfactory system.
    b. It mostly detects pheromones and other chemical signals.
    c. It integrates the olfactory information before sending it to the brain.
    d. It interacts with the olfactory system to amplify the signal.
    e. It detects chemicals from greater distances than olfaction does.

Answer 19

B

Question 20

28. The molecule that absorbs light is called a
    a. phototransduction.
    b. photoreceptor.
    c. photochemical.
    d. rhabdomere.
    e. photopigment.

Answer 20

E

Question 21

29. Which of the following is the most common evolved feature of eyes?
    a. A lens
    b. A retina
    c. Similar genes regulating eye development
    d. A rhodopsin-based photoreceptor cell
    e. Both c and d

Answer 21

D

Question 22

30. Which of the following statements is true of the transduction mechanism in both vertebrate and invertebrate vision?
    a. G protein activates phospholipase C.
    b. G protein activates cGMP phosphodiesterase.
    c. Light triggers the conversion of cis retinal to trans retinal.
    d. Cation channels are opened and Na+ enters the photoreceptor membrane.
    e. Second messengers IP3 and DAG are synthesized.

Answer 22

C

Question 23

31. Phototransduction in Drosophila takes place on the
    a. retina of the ommatidium.
    b. membrane of the microvilli of the retinular cell’s rhabdomere.
    c. membrane of the ommatidium of the compound eye’s retinular cell.
    d. membrane of the outer segment of the rod.
    e. membrane of the ommatidium’s rhabdomere.

Answer 23

B

Question 24

35. For terrestrial vertebrates, the greatest amount of refraction occurs
    a. at the interface between the air and the cornea.
    b. in the aqueous humor.
    c. in the lens.
    d. in the vitreous humor.
    e. at the retina.

Answer 24

A

Question 25

36. Which of the following best describes the vertebrate mechanism that operates on the outer segment cell membrane of the rod in the presence of light?
    a. cGMP detaches from the sodium channels, causing them to close.
    b. cGMP that is attached to the sodium channels causes them to open.
    c. Light activates rhodopsin by isomerizing retinal from cis to trans.
    d. Light activates rhodopsin by isomerizing retinal from trans to cis.
    e. A G protein activates cGMP phosphodiesterase.

Answer 25

A

Question 26

40. Which of the following occurs in the vertebrate rod in the absence of light?
    a. Rhodopsin is activated.
    b. cGMP is converted back to 5’-GMP.
    c. cGMP dissociates from Na+ channels.
    d. cGMP opens Na+ channels.
    e. G protein activates cGMP phosphodiesterase.

Answer 26

D

Question 27

41. In the dark, a cone membrane of a fish will be
    a. relatively depolarized.
    b. relatively hyperpolarized.
    c. at zero mV.
    d. photochemically fluctuating.
    e. Both a and b

Answer 27

A

Question 28

42. Which of the following statements regarding the regeneration of rhodopsin in vertebrates is false?
    a. All-trans retinol is re-isomerized back to all-cis retinol
    b. Regeneration of rhodopsin is enzymatic.
    c. All-trans retinal becomes unbound from the opsin protein.
    d. The enzyme in the photoreceptor is retinol dehydrogenase.
    e. An added photon is necessary to change all-trans retinal back to all-cis retinal.

Answer 28

E

Question 29

43. _______ cells are the output of the retina.
    a. Amacrine
    b. Horizontal
    c. Bipolar
    d. Ganglion
    e. Cone

Answer 29

D

Question 30

44. The area of the retina within which the membrane potential of a particular neuron can be influenced by light is called the
    a. lateral area.
    b. on-center area.
    c. straight-through area.
    d. outer plexiform layer.
    e. receptive field.

Answer 30

E

Question 31

1. Sensory receptor cells can be classified in all of the following ways except
   a. location of the source of the stimulus.
   b. sensory modality.
   c. form of stimulus energy.
   d. mechanism of transduction.
   e. sense organ.

Answer 31

E

Question 32

2. How does the CNS differentiate between sensory signals from the PNS?
   a. The action potentials are slightly different for each sense.
   b. The different sensory pathways project to different areas of the cerebral cortex.
   c. Some senses only produce graded potentials.
   d. The frequencies of action potentials from each sensory modality are different.
   e. All of the above

Answer 32

B

Question 33

3. Which of the following is not a mechanoreceptor cell in mammalian skin?
   a. Merkel disk
   b. Meissner corpuscle
   c. Malpighian corpuscle
   d. Pacinian corpuscle
   e. Ruffini ending

Answer 33

C

Question 34

4. Which structure is most commonly used as the auditory organ in insects?
   a. Ears
   b. Semicircular canals
   c. Statocyst
   d. Tympanal organ
   e. Hair cells

Answer 34

D

Question 35

5. Which of the following does not directly relate to transduction of an aspect of sound?
   a. The magnitude of hair cell bending
   b. The location (population) of hair cells bending
   c. The direction of hair cell bending
   d. The number of action potentials coming from the hair cell
   e. None of the above

Answer 35

D

Question 36

6. Which of the following statements regarding the transduction mechanism of the hair cell is true?
   a. Displacement of the hair cell bundle toward the tallest stereocilium depolarizes the membrane.
   b. The vibration of the hair cell bundle produces an action potential on the membrane.
   c. Displacement of the hair cell bundle in any direction depolarizes the membrane.
   d. Displacement of the hair cell bundle toward the shortest stereocilium depolarizes the membrane.
   e. Any movement of the hair cell bundle produces an action potential on the membrane.

Answer 36

A

Question 37

7. Which of the following statements regarding the mechanism of hearing is false?
   a. Sound travels into the semicircular canal and vibrates the tectorial membrane.
   b. Displacement of the hair cells in one direction depolarizes the hair cell membrane.
   c. The sound amplitude relates to the amount of hair cell membrane depolarization.
   d. Inner hair cells are responsible for most of the afferent signal to the brain.
   e. High frequency sounds tend to bend hair cells near the oval window.

Answer 37

A

Question 38

8. In the taste sensilla of Drosophila, which of the following substances would not likely be detected?
   a. Water
   b. Fructose
   c. NaCl
   d. A bitter substance, such as quinine
   e. Starch

Answer 38

E

Question 39

9. Which of the following taste quality mechanisms does not involve a G protein receptor?
   a. Sweet
   b. Sour
   c. Bitter
   d. Umami
   e. None of the above; all are mediated by a G protein receptor.

Answer 39

B

Question 40

10. Which of the following senses has a receptor cell that directly produces an action potential?
    a. Hearing
    b. Taste
    c. Equilibrium
    d. Vision
    e. Olfactory

Answer 40

E

Question 41

11. Which of the following is the most likely mechanism for odorant receptor molecules in mammals?
    a. Odorant receptors initiate a G protein-mediated signal cascade, which ultimately opens a cyclic nucleotide-gated cation channel.
    b. Odorant receptors bind to the odorant molecule and open, producing a depolarization.
    c. Odorant receptors initiate a G protein-mediated signal cascade, which ultimately produces a metabotropic action.
    d. Odorant receptors bind to the odorant molecule and close, producing a hyperpolarization.
    e. Odorant receptors initiate a G protein-mediated signal cascade, which ultimately opens potassium channels.

Answer 41

A

Question 42

12. In many vertebrates, _______ predominantly detect pheromones.
    a. specialized taste buds
    b. the olfactory system
    c. the vomeronasal organ
    d. modified nerves in the brain
    e. internal chemoreceptors

Answer 42

C

Question 43

13. In the vertebrate eye, the main transduction event takes place
    a. on the iris.
    b. at the cornea.
    c. in the retina.
    d. at the lens.
    e. within the optic nerve.

Answer 43

C

Question 44

14. _______ is the vertebrate sense in which the “resting,” or unexcited, condition of the receptor is depolarized.
    a. Touch
    b. Smell
    c. Vision
    d. Taste
    e. Hearing

Answer 44

C

Question 45

15. Which of the following best describes the first major transduction event in the vertebrate eye?
    a. Retinal changes from cis- to trans-isomer.
    b. Opsin changes conformation.
    c. Action potentials are generated in the optic nerve.
    d. Activated rhodopsin activates a G protein.
    e. Light is refracted at the lens to focus on the retina.

Answer 45

A

Question 46

16. When light activates rhodopsin, the result at the vertebrate rod or cone outer membrane is
    a. depolarization.
    b. hyperpolarization.
    c. polarity reversal.
    d. inhibition.
    e. an action potential.

Answer 46

B

Question 47

17. Which statement best describes the regeneration of rhodopsin in vertebrate rods?
    a. Rhodopsin does not need to be regenerated.
    b. Photochemical regeneration of rhodopsin is instantaneous.
    c. Photochemical regeneration of rhodopsin is slow.
    d. Enzymatic regeneration is slow.
    e. Enzymatic regeneration is based on dark adaptation.

Answer 47

D

Question 48

18. Which of the following types of cells in the retina have their most prominent action in the lateral pathway, as opposed to the straight-through pathway?
    a. Bipolar cells
    b. Rods
    c. Ganglion cells
    d. Cones
    e. Horizontal cells

Answer 48

E

Question 49

19. In the visual projection pathway of mammals, the geniculostriate pathway projects
    a. from one eye to the primary visual cortex.
    b. to the lateral geniculate nucleus within the primary visual cortex.
    c. to the primary visual cortex and then to the lateral geniculate nucleus.
    d. to the lateral geniculate nucleus and then to the primary visual cortex.
    e. None of the above

Answer 49

D

Question 50

20. Based on spectral sensitivities of human retinal cones, what types of cones do we have?
    a. Blue cones, blue/green cones, and red cones
    b. Blue cones, green cones, and red cones
    c. Yellow cones, green cones, and red cones
    d. Ultraviolet cones, green cones, and red cones
    e. Yellow cones, green cones, and violet cones

Answer 50

B

Question 51

1. What are the four different ways a sensory receptor cell can be classified?

Answer 51

Sensory receptor cells can be classified by sensory modality, by the form of stimulus energy, by the mechanism of transduction, and according to the location of the source of the stimulus energy relative to the body.

Question 52

2. Explain the principle of labeled lines.

Answer 52

The principle of labeled lines explains why action potentials that appear to be exactly the same are interpreted, when isolated, as the different senses. This relates to where in the brain these action potentials are being interpreted. The sensory modality or quality of sensation associated with a stimulus depends solely on which receptor cells are stimulated, rather than on how they are stimulated.

Question 53

3. How does the transduction mechanism work in a stretch (mechano-) receptor?

Answer 53

Stretch receptors have stretch-activated channels that are opened by the physical stretching of the membrane of the receptor cell. Typically, cations (Na+ and Ca2+) will then flow through these open channels and cause a depolarization on the membrane.

Question 54

4. Describe the process of adaptation as it relates to mechanoreceptors in mammalian skin.

Answer 54

Adaptation in a skin mechanoreceptor occurs as constant stimulation over time produces a lower frequency of action potentials

Question 55

5. How could the statocyst of a lobster be manipulated experimentally to cause the lobster to behave as if Earth’s gravity were the opposite of its true gravity?

Answer 55

If the dense grains in the statocyst could be removed and replaced with magnetic particles, such as small grains of iron, a simple magnet placed at the top of an aquarium would move the grains to the “top” of the statocyst. This would then alter the sense of gravity in the lobster and cause it to turn upside down

Question 56

6. Explain how the hair cells transduce sound intensity and frequency.

Answer 56

In the cochlea, both the number of bending hair cells and the degree of the bending transduce the mechanical information into a depolarization, which is decoded as sound intensity. It is the actual location of the bending hair cells on the cochlea that encodes frequency. Hair cells located toward the basal end of the cochlea will transduce higher frequency sounds, while hair cells located toward the apical end will transduce lower frequency sounds.

Question 57

7. A blowfly can taste with its feet. Explain.

Answer 57

A blowfly has taste receptors located within sensilla on the terminal segment of its legs. By walking into a substance, typically a fluid, it may be able to detect sugar or salt, or even bitter substances.

Question 58

8. How would you test whether or not an olfactory receptor cell responds to an odor?

Answer 58

A simple experiment is found in Figure 14.19 of the textbook. Typically, if you can isolate the olfactory receptor cell and record the current through a channel or channels, you only need to expose the cell to various odorants and a current change would indicate that the odorant causes that receptor (or receptors) to respond.

Question 59

9. Compare and contrast vertebrate and invertebrate transduction in photoreception.

Answer 59

While vertebrate and invertebrate photoreception share a similar initial transduction mechanism with the activation of rhodopsin (cis to trans retinal), the second messenger system, is different and the ultimate electrical events on the membrane are the opposite. Whereas light on an invertebrate photoreceptor causes an eventual depolarization, light in a vertebrate photoreceptor causes a hyperpolarization.

Question 60

10. Explain how hyperpolarization of a vertebrate cone will eventually be transduced into a train of action potentials sent to the brain via the optic nerve.

Answer 60

A hyperpolarization in a vertebrate cone will have two possible results on the associated bipolar cells. If the bipolar cell is an on-center bipolar cell, it will depolarize in response to the hyperpolarized cone, thus reversing the potential. On-center bipolar cells can excite an on-center ganglion cell to send a train of action potentials to the brain via the optic nerve.