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SMP - Neurophysio Exam 2 > Lecture 3 - Olfactory System > Flashcards

Lecture 3 - Olfactory System Flashcards

1
Q

Describe odorants.

A

Small, volatile, and hydrophobic molecules

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2
Q

What other epithelium does the olfactory epithelium resemble?

A

The respiratory epithelium

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3
Q

Describe the olfactory epithelium.

A

Pseudo stratified columnar epithelium with ciliated apical portion

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4
Q

What 3 cell types does the olfactory epithelium contain? Which cell type has cilia?

A
  1. Olfactory cells***
  2. Support cells
  3. Basal cells
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5
Q

What sits in between the olfactory cells and the olfactory bulb?

A

The cribriform plate of the ethmoid bone

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6
Q

Describe the olfactory pathway.

A

Olfactory cell cilia => olfactory epithelium => olfactory cell axons => ethmoid bone => axon convergence to form CN I (multiple bundles) => glomeruli where CN I synapses with mitral and tufted cells in the olfactory bulb => lateral olfactory tracts => piriform cortex of the cerebrum and amygdala

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7
Q

What is another name for olfactory receptor cells?

A

Olfactory receptor neurons

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8
Q

How many receptor types does each olfactory cell express?

A

Only ONE

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9
Q

Can one odorant activate multiple receptor types?

A

YUP

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10
Q

Can one receptor be activated by different odorants?

A

YUP

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11
Q

What gives olfaction a high degree of specificity?

A

The fact that one odorant can activate multiple receptor types

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12
Q

What gives olfactory cells a high degree of differentiation?

A

The fact that one cell only expresses one receptor type

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13
Q

What kind of receptors are odorant receptors?

A

GPCRs

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14
Q

Describe the olfaction transduction pathway.

A
  1. Odorant binds receptor
  2. Galpha activates AC
  3. AC synthesizes cAMP
  4. cAMP activates cyclic nucleotide gated (CNG) ion channels
  5. Na+/Ca2+ flow in => depolarization
  6. Ca2+ activated Ca2+ activated Cl- channels: Cl-flows out => depolarization until threshold
  7. AP in olfactory cell to the olfactory nerve (its axon)
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15
Q

In what structure do the olfactory nerves synapse with the olfactory bulb? Explain in detail.

A

Glomeruli: one type of olfactory receptor cells synapses with mitral and tufted cells

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16
Q

Describe the symmetry of the olfactory bulb. What does this mean?

A

Bilateral symmetry so each side has an olfactory tract

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17
Q

What are periglomerular cells?

A

Cells in the olfactory bulb that sharpen/filter the signal via lateral inhibition

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18
Q

Is there crossing over between the 2 lateral olfactory tracts?

A

Nope except for the occasional mitral cell collateral

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19
Q

Is the convergence of one type of olfactory cell (aka topography) in each glomerulus preserved in the amygdala?

A

Yes

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20
Q

Is the convergence of one type of olfactory cell in each glomerulus preserved in the piriform cortex?

A

NOPE

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21
Q

What are the 4 targets of the olfactory tracts? Which is the main one?

A
  1. Piriform cortex***
  2. Amygdala
  3. Olfactory tubercle
  4. Entorhinal cortex
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22
Q

Does the thalamus receive information from the olfactory bulb?

A

Not directly, but some from the amygdala

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23
Q

What are the 3 targets of the amygdala once it receives information from the olfactory bulb?

A
  1. Orbifrontal cortex
  2. Thalamus
  3. Hypothalamus
24
Q

What is the target of the entorhinal cortex once it receives information from the olfactory bulb? What is the significance of this?

A

Hippocampal formation, meaning olfaction is linked to memory structures

25
Q

Is there a topography of receptors on the olfactory epithelium?

A

YUP (group in ante/post rows)

26
Q

Are there more odorants or tastants?

A

Odorants

27
Q

How many types of odorant receptors?

A

600+

28
Q

Does the olfactory information pass through the thalamus before reaching the cortex?

A

NOPE

29
Q

What is anosmia?

A

Lack of olfactory sense that can be temporary or permanent

30
Q

What are the 2 possible causes of anosmia?

A
  1. Trauma: can tear the olfactory sensory epithelium from the ethmoid bone
  2. Illness/blockage of nasal passage due to mucous
31
Q

What is phantosmia?

A

Olfactory hallucinations

32
Q

What are the causes of phantosmia?

A

Many from either CNS or PNS

33
Q

What are pheromones?

A

Volatile compounds sensed on a subconscious level

34
Q

Do humans have a vomeronasal organ?

A

Yes, but it’s a residual organ

35
Q

What do pheromones regulate?

A

Reproductive behaviors in mammals (e.g. synchronization of menstrual cycles)

36
Q

How many olfactory sensory epithelium does each human have? Where?

A

2, one in each nasal cavity above the superior concha

37
Q

What is another name for the concha bone? Describe it.

A

Superior turbinate

Curls like a conch shell

38
Q

What kind of neurons are olfactory receptor cells?

A

Bipolar neurons with cilia

39
Q

On what part of the olfactory receptor cells are cilia located?

A

The bulbous dendrite

40
Q

What is the G olf protein?

A

The trimeric G protein bound to olfactory receptors

41
Q

What are cyclic nucleotide gated (CNG) ion channels permeable to?

A

Cations (Na+ and Ca++ flow in mostly)

42
Q

Where is the olfactory bulb located?

A

Forebrain

43
Q

What is the accessory olfactory system? Where is it found?

A

Vomeronasal system

Only found in non-human mammals

44
Q

What is the accessory olfactory system pathway?

A

Odorants => vemoronasal organ => olfactory epithelium => accessory olfactory bulb => medial amygdala => hypothalamus

45
Q

Does olfaction bypass the thalamus?

A

YUP

46
Q

What is the difference between the mitral and tufted cells of the olfactory bulb?

A
  • Mitral cells: Principal projection neurons of olfactory bulb and form the lateral olfactory tract
  • Tufted cells: local circuit neurons in glomeruli and sharpen sensitivity of individual glomeruli to certain ORNs
47
Q

What is another name for the piriform cortex?

A

Primary olfactory cortex

48
Q

Where is the piriform cortex located?

A

Medial temporal lobe

49
Q

What is the role of the olfactory tubercle?

A

Relay center

50
Q

Where is the olfactory tubercle located?

A

Medial temporal lobe

51
Q

Where is the entorhinal cortex located?

A

Medial temporal lobe

52
Q

What is the orbitofrontal cortex part of?

A

Limbic system

53
Q

What part of the thalamus is sent olfactory info from the amygdala?

A

Medial dorsal nucleus

54
Q

Is the convergence of one type of olfactory cell in each glomerulus preserved in the orbitofrontal cortex?

A

NOPE

55
Q

What can be said of the neurons of the olfactory epithelium?

A

High turnover

56
Q

Where are the olfactory bulbs located in relation to the optic nerves?

A

Almost directly inferiorly

SMP - Neurophysio Exam 2 (9 decks)

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