Lecture 5 - chemical senses Flashcards

1
Q

olfactory sensory transduction

A
  • binding of an odorant molecule triggers adenylyl cyclase
  • cAMP activates ion channels and calcium gated cloride channels
  • at every step in the pathway amplifies the signal more
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2
Q

why are these amplification systems useful?

A

they increase the sensitivity of the neurons of even dilute odours

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3
Q

olfactory receptors in mammals vs insects

A

in mammals they are GPCR and in insects they are ion channels

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4
Q

where do all axons go to

A

glomerulus. sensory neurons with different receptors go to different glomeruli

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5
Q

what is the insect equivalent of an olfactory bulb?

A

antennal lobe

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6
Q

local neurons

A

these carry information between the glomeruli these are granule cells and periglomerular cells

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7
Q

second order neurons

A

receive the information from each glomerulus these are mitral cells and tufted cells

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8
Q

how is odour specificity carried through?

A

receptor-specific matching of sensory neurons to second-order neurons

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9
Q

what does the first relay synapse do?

A

transforms the odour code between sensory neurons and second-order neurons

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10
Q

synaptic adaptation

A
  • first there is adaptation of synapse to emphasise the start of the odour
  • sensory neurons respond when there is an odour
  • projection neurons adapt to not fire as much and runs out of vesicles
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11
Q

converging sensory neurons onto second-order neurons

A
  • sensory neurons converge on one spot and this reduces the noise
  • second order neurons listen to many sensory neurons
  • projection neurons response is a sharp spike response to help detect weak odours
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12
Q

the two functions of lateral cross-talk

A

gain control and de-correlation

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13
Q

mechanism of gain control

A

for systems to be sensitive to different intensities is by the interneurons

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14
Q

weak odour on a graph (gain control)

A

with a weak odour the second-order neurons respond a lot. the plateau of the graph is where projection neurons are saturated

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15
Q

strong odour on a graph (gain control)

A

with a strong odour it activates multiple glomeruli with lateral cross talk between them
recruit inhibiting interneurons and pushes the curve over to the right and less steep at the beginning

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16
Q

de-correlation

A

decorrelate the odour responses and make the odours more widely separated
for each pair of odours, can calculate the similarity between the responses of different odours

17
Q

mechanism of decorrelation

A
  • knock out the lateral inhibiting neurons, the odour responses become more similar
  • stronger channels inhibit the weaker neurons
  • makes the odour responses more distinctive
18
Q

which area associates a particular odour?

A

piriform cortex

19
Q

which area is for more innate behaviour?

A

amygdala in mammals and lateral horn for insects

20
Q

where does learned behaviour happen for insects?

A

in the Kenyon cells in mushroom body

21
Q

how to reduce the response to an odour in the amygdala?

A

express the inhibiter in the amygdala and shine a light

22
Q

learning circuitry

A

need to discriminate multiple odours in the world and has sparse activity

23
Q

innate circuity

A

only way certain neurons to respond and has dense activity

24
Q

olfactory search behaviour

A
  • if things get better with an increased concentration of nutrient, go towards and turn less
  • chemical system detects the nutrient to keep going but if not it changes directions
25
Q

active sensing search strategy

A
  • behaviour allows the animal to actively sense the environment to fit well with how the olfactory system processes information
  • moving head back and forth actively changing the concentration of the odour
26
Q

taste transduction

A
  • uses metabotropic and ionotropic receptors and amplifies signals
  • chemical cues are GPCR that triggers enzyme and second messengers
  • salt taste is iontropic
27
Q

where do cranial nerves go?

A

go from the tongue to the solitary nucleus in the brainstem

28
Q

where is information from the thalamus relayed into?

A

relayed into the insula and parietal cortex

29
Q

what happens when tasting bitter and sweet at the same time?

A

the bitter tatste does lateral inhibiton of the sweet neurons and surpresses the synpatic release

30
Q

stimulating sensation of tastes

A

stimulate sensation of the bitter taste with a light and triggers artificial perception of taste