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Zoology 523 > Unit 2 Week 1 > Flashcards

Unit 2 Week 1 Flashcards

1
Q

What are examples of sensory stimuli?

A

chemical senses
auditory system
somatic sensory system
visions part I and II

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2
Q

What are the two examples of chemical senses?

A

taste (gustation)
smell (olfaction)

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3
Q

What impacts our perception of flavor?

A

chemical senses
-taste and smell
other sensory modalities
-temp
-texture

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4
Q

What are we actually tasting?

A

hydrophilic chemicals that dissolve in saliva

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5
Q

What is taste for?

A

-distinguish between food and poison
-distinguish between different types of food
-important for the control of feeding

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6
Q

What are the 5 basic tastes? Include examples of chemicals that cause the taste

A

Saltiness - NaCl
Sourness - H+
Sweetness - Sucrose
Bitterness - Caffeine
Umami - Glutamate

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7
Q

Define Tastant

A

a chemical that stimulates the sense of taste

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8
Q

Describe the anatomy of the tongue

A

covered in papillae, each papillae has about 100 taste buds
taste buds have synapses, taste receptor cells,

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9
Q

What are taste receptor cells?

A

respond the taste stimuli, 50-150 TRCs per taste bud

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10
Q

Where does the synapse from a taste bud go?

A

onto gustatory afferent axons, pass along taste sensing

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11
Q

Describe the central taste pathway

A
  1. taste receptor cell
  2. gustatory nucleus
  3. VPM of thalamus
  4. gustatory cortex
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12
Q

Describe receptor potential

A

-a stimulus-induced change in the membrane potential of a sensory receptor
-can be depolarizing or hyperpolarizing

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13
Q

What is unique about taste receptor cells?

A

can respond to more than one basic taste, but with preference

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14
Q

When the taste receptors depolarize and release transmitters, what is the result?

A

excitatory effects on downstream neurons

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15
Q

Describe sensory transduction

A

the process by which an environmental stimulus causes an electrical response (receptor potential) in a sensory receptor cell

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16
Q

How is sensory transduction possible?

A

ion channels, GPCRs

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17
Q

What are the mechanisms of taste transduction?

A

During the transduction process, taste stimuli may:
-pass directly through ion channels
-bind to and block ion channels
-bind to G-protein-coupled receptors (GPCRs) and activate a second messenger to open ion channels

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18
Q

Which taste types use Ion Channels as receptors vs. dimer GPCRs?

A

Saltiness and Sourness - Ion Channels
Sweetness, Bitterness, and Umami - GPCRs

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19
Q

Describe the detection of saltiness

A

Salt-sensitive taste cells
-activate special Na+ selective channel
-cause depolarization
-release serotonin to activate gustatory afferent axons

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20
Q

Describe the detection of sourness

A

Proton-sensitive tase cells
-activate H+- selective channel
-block K+ - selective channel
-cause depolarization
-release serotonin to activate gustatory afferent axons

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21
Q

What are the two ways to detect sourness?

A

Both H+ channel and K+ channel

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22
Q

What are the receptors for bitter, sweet, and umami?

A

bitter : T2Rs (25 types)
sweet: T1R2 + T1R3
umami: T1R1 + T1R3

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23
Q

Describe the detection of bitterness, sweetness, and umami.

A

Transduction process:
-activate GPCRs
-trigger the PLC to IP3 to Ca2+ signaling cascade
-cause depolarization
-release ATP to activate gustatory afferent axons

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24
Q

Define receptor potential:
a) an action potential in a sensory axon
b) hyperpolarization of the receptor membrane
c) the potential for a receptor to fire
d) a change in membrane potential in a receptor in response to an appropriate sensory stimulus

A

D

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25
Q

Which of the following is not a basic taste?
a) bitter
b) sweet
c) spicy
d) umami

A

C

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26
Q

For sensing sweet and umami, which of the following is TRUE?
a) there is a different ligand-gated channel to sense each
b) the transmitter released in response to these is different
c) both use dimers of G-protein coupled receptors
d) the second -messenger pathways used are different

A

C

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27
Q

Describe the function of smell

A

Smell: detection of airborne chemicals
-warns of harmful substances/danger
-combines with taste for identifying foods
-serve as a most of communication

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28
Q

Described the simplified central olfactory pathway

A
  1. olfactory receptor cells
  2. glomeruli
  3. 2nd order olfactory neuron
  4. olfactory cortex
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29
Q

Describe the relationship between olfactory receptor neurons (ORNs) and odorants

A

ORNs are activated by odorants

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30
Q

What is an odorant?

A

a chemical that stimulates the sense of smell

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31
Q

What is unusual about intracellular Cl- levels in dendrites of olfactory cells?

A

higher intracellular Cl- allows Cl- to leave cell visa Ca2+ activated Cl- channels leading to depolarization

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32
Q

Describe the mechanism of olfactory transduction

A

-odorants bind to GPCRs
-activate G-protein and adenylyl cyclase
-increase cAMP level
-open cAMP-gated cation channel (Na+ and Ca2+ influx)
-open Ca2+ activated Cl- channel (Cl- flow out of the cell)
-become depolarized and fire action potential

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33
Q

Describe the specifics of ORN expression and activation.

A

-each ORN expresses a single odorant receptor
-each ORN can be activated by multiple odorants

Each ORN expresses only one receptor, but that one receptor can detect multiple scents

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34
Q

How are odorants represented?

A

By multiple combinatorial activation of ORNs

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35
Q

Describe the makeup of an olfactory bulb

A

~2000 glomeruli
-each glomerulus receives inputs from one type of ORN expressing the same receptor
-creates a sensory map

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36
Q

What is a sensory map?

A

an orderly arrangement of neurons that correlated with certain features of the environment

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37
Q

What are two examples of spatial representations of olfactory information at the olfactory bulb?

A

-olfactory population coding
-olfactory maps

38
Q

What are GCaMPs?

A

a class of genetically encoded Ca2+ indicators used in calcium imaging

39
Q

What is calcium imaging used for?

A

visualizing neuron activity with in vivo

40
Q

What is temporal coding in the olfactory system?

A

the representation of information by the timing of action potentials rather than by their average rate

41
Q

For olfactory receptors in vertebrates, which of the following is part of the response to an odorant?
a) an odorant directly activates an ion channel
b) cAMP levels increase
c) a chloride channel opens and this makes the cell more negative
d) cAMP-gated ion channel is closed

A
42
Q

What is a sensory map?
a) temporal patterns of spiking that produce different sensations
b) a set of population-coded information specifying properties of stimulus
c) a spatial representation of the timing of action potentials
d) orderly arrangement of neurons correlated with certain features of the environment

A

D

43
Q

What is true of population coding?
a) a large number of neurons specify the properties of a stimulus
b) there is an orderly spatial arrangement of neurons
c) olfactory receptor cells are each responsive to only a single odor
d) none of the above

A

A

43
Q

What are sounds?

A

sounds are audible variations in the air pressure (sound waves)

43
Q

What is the audible range for humans?

A

20Hz - 20,000 Hz

43
Q

What is the relationship between pitch and frequency?

A

high pitch = high frequency
low pitch = low frequency

44
Q
A
45
Q
A
46
Q

What is the relationship between amplitude and intensity?

A

low intensity, low amplitude, quieter
high intensity, high amplitude, louder

47
Q

What is the sensation organ for sound detection?

A

cochlea

48
Q

Where are sounds converted into membrane vibration?

A

tympanic membrane (eardrum)

49
Q

What are the first stages of the auditory pathway?

A
  1. sound wave
  2. tympanic membrane
  3. ossciles
  4. oval window
  5. fluid in cochlea
  6. auditory sensory neuron
50
Q

What happens in the middle ear?

A

-sound force amplification by the ossicles (function like levers)
-much greater pressure at oval window than eardrum so that footplate can move fluids in cochlea, in response to sounds

51
Q

What are the three ossicles?

A

malleus, incus, stapes

52
Q

What happens in the inner ear?

A

transduction of sound energy into neural signals

53
Q

What is the organ or Corti for?

A

contains auditory receptor cells (hair cells)

54
Q

How many chambers are there in the inner ear? What fluids fill them?

A

3; two of them are filled with perilymph and one is filled with endolymph

55
Q

Describe the contents of perilymph vs. endolymph

A

perilymph: a liquid with 7 mM K+ and 140 mM Na+
endolymph: a liquid with 150 mM K+ and 1mM Na+

56
Q

How do vibrations travel?

A

in cochlear fluid

57
Q

What does the vibration of cochlear fluid lead to?

A

the vibration of the basilar membrane

58
Q

What are hair cells? Where can they be found?

A

hair cells are the auditory sensory cells that are activated by sounds
they sit on the basilar membrane in the organ of Corti

59
Q

Why type of cells are hair cells? How do they work?

A

mechanosensory
1. sounds
2. sterocilia
3. receptor potential in hair cells

60
Q

What controls the receptor potential of hair cells?

A

depends on the bending of stereocilia
increased tension = higher receptor potential

61
Q

Describe transduction by hair cells

A
  1. stereocilia bends and tip link is stretched
  2. mechanically-gated K+ channel open and K+ ion enters the cell
  3. hair cells depolarize
  4. calcium influx through VGCC
  5. release the transmitter glutamate
62
Q

What are the auditory sensory cells?

A

hair cells

63
Q

How do hair cells get their name?

A

have stereocilia (hair-like structure) in the apical surface

64
Q

What are the two types of hair cells?

A

OHC - outer hair cells
IHC - inner hair cells

65
Q

Describe IHC

A

dominate synaptic output to spiral ganglion cells (SGCs)
1 IHC feeds ~ 10 SGCs
IHC contribute to 95% output to SGCs

66
Q

What is the ration of OHC/IHC?

A

3:1

67
Q

Describe OHCs

A

amplify basilar membrane deflections
depolarized
motor proteins are compressed
hair cells are shortened
function as the cochlear amplifier

68
Q

What is the cochlear amplifier?

A

loop mechanism that causes the stereocilia of IHC to bend more

69
Q

Describe what happens during human deafness

A

-hair cell damage or lost is the most common cause
-in many cases, auditory nerves remain intact
-can require a cochlear implant: an artificial, electrical cochlear

70
Q

Which of the following contains auditory receptor neurons?
a) tectorial membrane
b) basilar membrane
c) organ of corti
d) none of the above

A

C

71
Q

What are the two properties of sound?

A

frequency (pitch)
intensity (loudness)

72
Q

What is a characteristic frequency?

A

a given intensity frequency at which a neuron is most responsive
auditory nerve responses are frequency tuned

73
Q

Describe the properties of the basilar membrane of the cochlea along its length

A

Base: stiffer and narrower
Apex: more flexible and wider

74
Q

What is the tonotopy of the basilar membrane of the cochlea?

A

high frequency at the base, low frequency at the apex

75
Q

Define Tonotopy

A

the systematic organization within an auditory structure based on the sound frequency
as sensory map for the auditory system

76
Q

What is phase locking?

A

the consistent firing of a neuron at the same phase of a sound wave
important for encoding low frequency sound

77
Q

When does phase locking occur?

A

low-frequency sound can elicit phase-locked response in auditory neurons
phase locking occurs with sound waves up to ~5 kHz
It happens on every cycle or some fraction of cycles

78
Q

Can high-frequency sound elicit phase-locked response?

A

no

79
Q

Describe the mechanisms that can be used for encoding sounds for the following frequencies:
20-200 Hz
200-5,000 Hz
5,000 Hz - 20,000 Hz

A

phase locking
tonotopy + phase locking
tonotopy alone

80
Q

What impacts encoding sound intensity?

A

-firing rate of auditory nerve
-number of active neurons in auditory nerve

81
Q

How do we localize sound in the horizontal plane?

A

-required a comparison of the sounds reaching the two rears
-Interaural Time Delay (ITD)
-Interaural Intensity Difference
-Depend on sound frequency

82
Q

What is the Interaural Time Delay (ITD)?

A

difference in time for sound to reach each ear
sound reaches the closest ear first
works with a frequency range of 20-2,000 Hz

83
Q

What is the Ineraural Intensity Difference (IID)?

A

sound at one ear less intense because of head’s sound shadow
sound intensity is larger at the closest ear
works for sounds with a frequency range of 2,000Hz- 20,000Hz

84
Q

What is sensitive to ITD?

A

superior olive, has binaural neurons
-receives inputs from both left and right cochlear nuclei
-selective for interaural time delay

85
Q

What is the Duplex theory of sound localization in the horizontal plane?

A

ITD: 20-2,000 Hz
IID: 2,000 - 20,000 Hz

86
Q

How do we localize sound in the vertical plane?

A

-vertical sound localization based on reflections from pinna
-the delays between direct path and the reflected path changes as the sound source move vertically

87
Q

Which of the following is a definition of phase locking?
A. the firing of a neuron at 60 Hz
B. firing of a cell at the same phase as that of a sound wave
C. Firing of the cell at a predetermined frequency that is independent of the sound wave
D. the locking of the neuron’s firing rate to that of the body’s circadian rythym

A

B

Zoology 523 (5 decks)

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