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ZOOL 342 > Olfaction > Flashcards

Olfaction Flashcards

1
Q

What is olfaction?

A

detection of chemicals in the air

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2
Q

What is gustation?

A

detection of chemicals that have been placed in the mouth

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3
Q

The olfactory system detects _______________ that bind to _________________ receptors (_____________)

A

odorants; olfactory; in the nose

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4
Q

The gustatory system detects _______________ that bind to _________________ receptors (_____________)

A

tastants; gustatory; tongue

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5
Q

TRUE or FALSE: olfactory system detects volatile substances wherease the gustatory system detects water soluble substances

A

TRUE

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6
Q

TRUE or FALSE: all vertebrates have an accessory olfactory system

A

FALSE: all vertebrates have a MAIN olfactory system; MOST LAND vertebrates have an accessory olfactory system

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7
Q

another name for an accessoryt olfactory system

A

vomeronasal system

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8
Q

Where does the main olfactory epithelium (MOE) project to? vomeronasal organ (VNO)?

A
  • MOE to main olfactory bulb (MOB)
  • VNO to accessory olfactory bulb (AOB)
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9
Q

TRUE or FALSE: the olfactory epithelium is just a flat surface

A

FALSE: labyrinth-like

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10
Q

Place the following in order of info transmission:
- olfactory epithelium
- cribiform plate
- olfactory bulb
- nasal cavity

A

nasal cavity, olfactory epithelium, cribiform plate, olfactory bulb

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11
Q

Describe the cribiform plate

A

sieve-like structure between the anterior cranial fossa and the nasal cavity; part of ethmoid bone

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12
Q

TRUE or FALSE: the olfactory epithelium has a small surface area

A

FALSE: large surface area

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13
Q

how much larger is the olfactory epithelium surface area in dogs vs humans

A

30x larger in dogs

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14
Q

TRUE or FALSE: dogs have more olfactory receptors than humans

A

TRUE

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15
Q

What is the lifetime of olfactory receptors? is this considred short or long?

A

60 days; short

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16
Q

How many receptors are made daily?

A

10,000-30,000

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17
Q

What kind of cells doe new olfactory receptors arise from?

A

basal cells (stem cells)

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18
Q

Which type of olfactory cells does COVID affect?

A

basal cells

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19
Q

Describe the path of information transmision from the dendrites of the olfactory recetpors to the brain (OR = olfactory receptor)

A

OR dendritic knobs –> OR unmyelinated axons –> synapse on mitral cells at the glomerulus in the olfactory bulb –> mitral cell axons go to the brain

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20
Q

how many cilia do the dendritic knobs of the OR have?

A

20-30

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21
Q

what is the diameter of the OR axons?

A

0.2 micrometer

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22
Q

describe the afferent and efferent path of information transmission in the olfactory system using the following:
- granule cell
- olfactory tract
- centrifugal afferents
- mitral cell
- periglomerular cell
- tufted cell
- glomerulus
- OR

A
  • efferent: OR –> periglomerular cells in the glomerulus –> tufted and mitral cells –> olfactory tracts
  • afferent: centrifugal afferents –> granule cells –> mitral and tufted cells
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23
Q

How do odorant molecules bind to the OR?

A

odorant molecules dissove in the mucous then interact with ODROANT BINDING PROTEINS in the mucous; then this complex binds with OR receptors on the cilia

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24
Q

What percentage of the genome is dedicated to olfaction?

A

3%

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25
Q

Describe the structure of all OR proteins.

A
  • 7 transmembrane segments
  • GPCR
  • cAMP second messenger
26
Q

At which transmembrane segments of the OR proteins do odorants bind?

A

3,4,5

27
Q

TRUE or FALSE: each OR neuron expresses multiple types of OR proteins

A

FALSE: each OR neuron expresses ONE type of OR protein

28
Q

What reflects the range of scents that an organism can detect?

A

number of OR genes

29
Q

TRUE or FALSE: primates have many OR genes

A

FALSE: very few OR genes

30
Q

TRUE or FALSE: rodents have 4x the number of OR genes than primates

A

TRUE

31
Q

Arrange the following form most OR genes to least: primates, rats, african elephatns

A

african elephant > rat > primate

32
Q

Which ions do odorant binding conduct?

A

initial inward K+ current and then larger longer inward current due to 2nd messenger system (Na+, Cl-, Ca2+)

33
Q

TRUE or FALSE: the odorant binding directly opens the ion channel

A

FALSE: 2nd messenger system is involved

34
Q

Draw the current resulting from odorants released onto OR neuron cell body. onto the cilia?

A

slide 13; A then B

35
Q

Describe the 2nd messenger cascade that results from odorant binding.

A
  1. odorant binds to OR protein –> GDP exchanged for GTP causing alpha-subunit to separate from G-protein
  2. GTP-alpha-subunit activates adenylyl cyclase (AC) –> ATP converted to cAMP
  3. cAMP opens cyclic-nucleotide gated cation channel
  4. depolarization results from Na+ (and Ca2+) influx
  5. Ca2+ influx cause Cl- channels to open; Cl- flows OUT of cell to maintain depolarization
36
Q

Why does Cl- have to flow out of the OR cell to maintain depolarization?

A

the outside of the cell is not an extracellular space, but instead it is air or mucous; therefore the Na+ levels are not normal and do not allow Na+ to keep flowing in as in usual depolarizations. Cl- flowing out of the cell gives an extra push for depolarization to occur.

37
Q

How would the olfactory system be affected if we lacked cAMP-gated channels?

A

no odour discrimination

38
Q

What is different about the second messenger system in invertebrates?

A
  • OR proteins may be coupled to G proteins that activate PLC
  • IP3 can act on Ca2+ channels directly
39
Q

Which zones of the olfactory epithelilum and olfactory bulb are different families of the OR proteins localized to?

A

4 and 5

40
Q

There is segregation/refinement of information from each OR protein type. How is this demonstrated?

A

each glomerulus receives input from ORs containing a SINGLE OR PROTEIN

41
Q

What kind of map is found in the olfactory bulb?

A

chemotopic (slide 19)

42
Q

TRUE or FALSE: each OR protein responds to a unique odor

A

FALSE: each OR protein can recognize more than one odorant (odour generalist receptors)

43
Q

If each OR protein can recognize more than one odorant, then what determines the smell that we detect?

A

pattern of activity across all receptors / POPULATION CODING

44
Q

TRUE or FALSE: one odorant can excite more than one OR neuron

A

TRUE

45
Q

How many unique odours are there?

A

10,000

46
Q

What is the function of the vomeronasal organ?

A

detecting pheromones

47
Q

What are pheromones?

A

chemical signals that affect behaviour or physiology in conspecifics

48
Q

How does the olfactory system react to pheromones in mammals? in snakes and lizards?

A
  • mammals: nasopalatine duct is normally closed, but opens when an odour associated with a pheromone is detected
  • snakes and lizards: tongue draws in pheromones into the vomeronasal organ (tongue flicking)
49
Q

What is the name for the response where arnimals curl the tongue and open the mouth to allow scents to enter the VNO?

A

Flehmen response

50
Q

What is the only difference between the olfactory epithelium and the vomeronasal epithelium?

A
  • vomeronasal epithelium has microvilli
  • olfactory epithelium has cilia
51
Q

How many vomeronasal receptor (VR) proteins are there in mice? how specific are they?

A
  • 300 different VR proteins in mice
  • each responsive to a single (or a few) specific chemical compounds
52
Q

what is the difference between VR and OR?

A
  • VR = odour specialist receptors
  • OR = odour generalist receptors
53
Q

What are the 2 main families of G proteins that VRs are coupled to? Describe the cascade. which domain is important in this cascade?

A
  • V1R coupled to Gi2
  • V2R coupled to Go
  • both use IP3 and DAG as 2nd messengers to open TRPC2 cation channels; Na and Ca both flow in; Ca binds to CaM (CIRB domain)
54
Q

Where do vomeronasal receptor cells project to?

A

accessory olfactory bulb

55
Q

TRUE or FALSE: the vomeronasal epithelium projection to the accessory olfactory bulb has a similar type of organization to olfactory epithelium projection to olfactory bulb

A

TRUE

56
Q

TRUE or FALSE: the main olfactory bulb projects to the thalamus

A

FALSE: NO RELAY TO THALAMUS

57
Q

List the projections of the main olfactory bulb. Which is considered the primary olfactory cortex?

(REMOVE SLIDE)???

A
  • anterior olfactory nucleus (AON)
  • tenia tecta (TT)
  • olfactory tubercule (OT)
  • piriform cortex (PC) –> like primary olfactory cortex
  • anterior nuclsie of the cortical amygdala (COA) to entorhinal cortex (EC)
58
Q

What is the lateral olfactory tract?

A

main olfactory bulb –> COA –> EC

59
Q

What are the main projections of the main olfactory bulb? what are their functions?

A
  • piriform cortex: identification of odours
  • amygdala: emotion/fear/aggression
  • entorhinal cortex and hippocampus: memory
  • hypothalamus: appetite control/sexual behaviour
60
Q

The main olfactory bulb synapses onto the _____________ amygdala. The accessory olfactory bulb synapses onto the ___________ amygdala.

A
  • main = lateral (aLA, pLA)
  • accessory = medial (aMA, pMA)
61
Q

TRUE or FALSE: the lateral amygdala has more extensive connections with the hypothalamus; this means that the main olfactory bulb has more connections with the hypothalamus

A

FALSE: medial; accessory

62
Q

Which nucleus has extensive connectsion with the amygdala and hypothalamus? Is it associated with the main or accessory olfactory bulb?

A
  • bed nucleus of the stria terminalis (BST)
  • accessory olfactory bulb

ZOOL 342 (21 decks)

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