Lecture 3 - Olfactory System Flashcards Preview

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

Flashcards in Lecture 3 - Olfactory System Deck (56):
1

Describe odorants.

Small, volatile, and hydrophobic molecules

2

What other epithelium does the olfactory epithelium resemble?

The respiratory epithelium

3

Describe the olfactory epithelium.

Pseudo stratified columnar epithelium with ciliated apical portion

4

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

1. Olfactory cells***
2. Support cells
3. Basal cells

5

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

The cribriform plate of the ethmoid bone

6

Describe the olfactory pathway.

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

7

What is another name for olfactory receptor cells?

Olfactory receptor neurons

8

How many receptor types does each olfactory cell express?

Only ONE

9

Can one odorant activate multiple receptor types?

YUP

10

Can one receptor be activated by different odorants?

YUP

11

What gives olfaction a high degree of specificity?

The fact that one odorant can activate multiple receptor types

12

What gives olfactory cells a high degree of differentiation?

The fact that one cell only expresses one receptor type

13

What kind of receptors are odorant receptors?

GPCRs

14

Describe the olfaction transduction pathway.

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
6. AP in olfactory cell to the olfactory nerve (its axon)

15

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

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

16

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

Bilateral symmetry so each side has an olfactory tract

17

What are periglomerular cells?

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

18

Is there crossing over between the 2 lateral olfactory tracts?

Nope except for the occasional mitral cell collateral

19

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

Yes

20

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

NOPE

21

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

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

22

Does the thalamus receive information from the olfactory bulb?

Not directly, but some from the amygdala

23

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

1. Orbifrontal cortex
2. Thalamus
3. Hypothalamus

24

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

Hippocampal formation, meaning olfaction is linked to memory structures

25

Is there a topography of receptors on the olfactory epithelium?

YUP (group in ante/post rows)

26

Are there more odorants or tastants?

Odorants

27

How many types of odorant receptors?

600+

28

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

NOPE

29

What is anosmia?

Lack of olfactory sense that can be temporary or permanent

30

What are the 2 possible causes of anosmia?

1. Trauma: can tear the olfactory sensory epithelium from the ethmoid bone

2. Illness/blockage of nasal passage due to mucous

31

What is phantosmia?

Olfactory hallucinations

32

What are the causes of phantosmia?

Many from either CNS or PNS

33

What are pheromones?

Volatile compounds sensed on a subconscious level

34

Do humans have a vomeronasal organ?

Yes, but it's a residual organ

35

What do pheromones regulate?

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

36

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

2, one in each nasal cavity above the superior concha

37

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

Superior turbinate

Curls like a conch shell

38

What kind of neurons are olfactory receptor cells?

Bipolar neurons with cilia

39

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

The bulbous dendrite

40

What is the G olf protein?

The trimeric G protein bound to olfactory receptors

41

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

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

42

Where is the olfactory bulb located?

Forebrain

43

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

Vomeronasal system

Only found in non-human mammals

44

What is the accessory olfactory system pathway?

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

45

Does olfaction bypass the thalamus?

YUP

46

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

- 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

What is another name for the piriform cortex?

Primary olfactory cortex

48

Where is the piriform cortex located?

Medial temporal lobe

49

What is the role of the olfactory tubercle?

Relay center

50

Where is the olfactory tubercle located?

Medial temporal lobe

51

Where is the entorhinal cortex located?

Medial temporal lobe

52

What is the orbitofrontal cortex part of?

Limbic system

53

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

Medial dorsal nucleus

54

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

NOPE

55

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

High turnover

56

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

Almost directly inferiorly