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NAB > 5b. Olfaction > Flashcards

5b. Olfaction Flashcards

1
Q

Odourant Dissolution

A

Odorants dissolve in the mucus film and possibly become associated with oforant binding protein

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2
Q

Olfactory Receptor Length

A

Long

Send axons through the perforated cribriform plate to synapse in the olfactory bulb.

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3
Q

Olfactory Epithelium

- 3 Cell Types

A
  • Olfactory receptor cells
  • Supporting cells
  • Basal cells
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4
Q

Odorant Receptor Genes

  • Dogs
  • Humans
A

Dogs have 1,000 odourant receptor genes

Humans have 350 odourant receptor genes

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5
Q

Olfactory Epithelium

- Basal Cells

A

olfactory receptors are renewed every 60 days due to basal cell division

New axons grow into the adult CNS, which is unique

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6
Q

Olfactory Epithelium

- Olfactory Receptor Cell Structure

A

Cilia cover by the mucus film

Olfactory knob which gives off cilia

Cell body

Axon

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7
Q

Olfactory Receptor

- Structure

A

G-protein coupled receptor

Golf G protein coupled

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8
Q

Olfactory Receptor

- Cascade

A
  1. Activated Golf stimulates adenylyl cyclase to produce cAMP
  2. cAMP opens cyclic nucleotide gated cation channels in the ciliary membrane
  3. Influx of Ca2+ and Na+
  4. Depolarisation and roles of Ca2+
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9
Q

Olfactory Receptor Cells

- Roles of Ca2+

A

Activates Ca2+ gated Cl- channels
- Olfactory receptor cells actively accumulate Cl- so flow is out of the cell, augmenting depolarisation

Ca2+ binds to calmodulin and decreases the affinity of cyclic nucleotide gated channels for cAMP, allowing channels too close.
- Adaptation

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10
Q

Olfactory Receptor Cells

- Ca2+ Efflux

A

Ca2+ leaves olfactory receptor cells via:

  • Na+:K+:ca2+ exchanger
  • Maybe Ca2+ ATPase
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11
Q

Olfactory Bulb

- 2 Cell Types

A
  • Mitral cells
  • Tufted cells

Located in medial and lateral glomeruli

Long receptor axons pass through the cribriform plate into the olfactory bulb and synapse with either of these cell types in the medial and lateral glomeruli

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12
Q

Olfactory Bulb

- Output

A

Mitral and tufted cell axons travel to higher processing centres

Mitral cell axons travel in the lateral olfactory tract

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13
Q

Olfactory Bulb

- Lateral Inhibition Cell Types

A
  • Periglomerular cells

- Granule cells

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14
Q

Olfactory Bulb

- Periglomerular Cells

A

Make inhibitory connections between glomeruli

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15
Q

Olfactory Bulb

- Granule cells

A

Make inhibitory connections between basal dendrites of the mitral cells

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16
Q

Olfactory Bulb

- Lateral Inhibition Function

A

Sharpen mitral cell odour tuning

17
Q

Olfactory Bulb

- Lateral Inhibition Pathway

A

Activation fo a mitral cell activates granule or periglomerular cells that synapse with it, which then inhibits surrounding mitral cells, which may have been less effectively stimulated by olfactory fibres

18
Q

Lateral Olfactory Tract Synapses

A
  • Anterior olfactory nucleus
  • Olfactory tubercle
  • Pyriform cortex
  • Amygdaloid complex
  • Entorhinal cortex
19
Q

Anterior Olfactory Nucleus

A

Mitral cell axons form synaptic connections with projection neurones in the anterior olfactory nucleus.

These cells send their axons via the anterior com issuere to the contralateral olfactory bulb to stimulate granule cells that will inhibit the contralateral mitral cell population

20
Q

Olfactory Tubercle

A

Projects to the medial dorsal nucleus of the thalamus, which projects to the orbitofrontal cortex

Conscious perception of odour

21
Q

Pyriform Cortex

A

Projects to other olfactory cortical regions

22
Q

Amygdaloid Complex

A

Projects to:

  • Hypothalamus = autonomic adjustments
  • Reticular formation = Arousal
23
Q

Entorhinal Cortex

A

Projects to:

  • Hippocampus = motivation and emotion
  • Hypothalamus = autonomic adjustments
24
Q

Odour Selectivity

A

Increases as the olfactory pathway is ascended

  1. Lateral inhibition in the olfactory bulb
  2. Olfactory cortex = relatively un-selective for odours
  3. Pyriform and amygdala = Slightly more selective for odours
  4. Orbitofrontal cortex is very selective, where most cells only respond to a single odour type
25
Q

Vomeronasal Organ

- Differences Compared to Olfactory Epithelium

A

Microvilli instead of cilia

Transduction cascade based on IP3 rather than cAMP

26
Q

Vomeronasal Organ

- Pathway

A

Long receptor axons project via the accessory olfactory bulb to the amygdala

27
Q

Vomeronasal Organ

- Ligands

A

Pheromones

MHC peptides

28
Q

Human Equivalent of Vomeronasal Function

A

Trace Amine Associated Receptors (TAAR) in main olfactory epithelium.

Detect volatile amines in sweat and shift female mood, perhaps to increase fertility

NAB (37 decks)

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