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*Neuroendocrine Exam 3 > 7. Physiology of Taste and Olfaction > Flashcards

7. Physiology of Taste and Olfaction Flashcards

1
Q

What tastes will cause ATP release?

A

Sweet
Umami
Bitter

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2
Q

What tastes will cause serotonin release?

A

Salty

Sour

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3
Q

ATP can have which effects on neuronal taste receptors?

A

It can stimulate serotonin release (salty, sour).

Activate autocrine signaling.

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4
Q

Salty physiological response

A

epithelial Na+ enters via ENaC.
Ca++ enters
Depolarization
Serotonin release

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5
Q

Sour physiological response

A

H+ inhibits K+ channels.
Increase Ca++
Depolarization.
Serotonin release.

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6
Q

Sweet physiological response

A

Gq increases IC Ca++.
TRPM5 activation.
Depolarization.
ATP released thru specific channels

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7
Q

Umami physiological response

A

Same as sweet, but includes Gq protein mGluR4.

Gq increases IC Ca++.
TRPM5 activation.
Depolarization.
ATP released thru specific channels

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8
Q

Bitter physiological response

A

Same as sweet.

Gq increases IC Ca++.
TRPM5 activation.
Depolarization.
ATP released thru specific channels

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9
Q

Why is there high binding affinity for bitter tastants?

A

Because poisons are bitter tasting

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10
Q

Gustatory cortex (3)

A

Postcentral gyrus
Frontal operculum
Insula

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11
Q

Where do all the taste branches of CN VII, IX and X terminate?

A

Nucleus tractus solitarius

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12
Q

Obitofrontal cortex

A

Integrates visual, SS, olfaction and gustatory stimuli.

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13
Q

Amgydala’s role in eating

A

Emotional aspects of eating, memories, etc.

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14
Q

Hippocampus’s role in eating

A

Homeostatic mechanisms of hunger (I’m hungry now, etc).

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15
Q

How does an odorant lead to an IC cascade?

A

Odorant binds Golf which stimulates AC –> increase cAMP which opens CNGC (cyclic nucleotide gated channels) leading to cation influx and depolarization.

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16
Q

How can you get used to a smell?

A

If the odorant persists, sensitivity of CNGC to cAMP decreases. This lowers cation influx or can be inactivated by receptor phosphorylation.

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17
Q

Explain the relationship between an olfactory neuron and glomerulus and what they can detect

A

One neuron expresses receptor for only one odorant. They synapse into a glomerulus with neurons that detect similar odors.

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18
Q

How can we detect so many smells?

A

One odorant can stimulate more than one receptor or combinations of different neurons, changes in conc, etc

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19
Q

Granular cells and periglomerular cells do what?

A

Increase specificity of signal by inhibition (GABA)

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20
Q

Olfactory system is the only sense that:

A

Does not go through the thalamus before going to the cortex.

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21
Q

Pifiform cortex projection to the lateral hypothalamus controls:

A

Appetite

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22
Q

Piriform cortex projection to thalamus to medial orbitofrontal cortex does:

A

Integration of taste, sight and smell.

Appreciates flavors of food.

23
Q

Anterior cortical amygdaloid nucleus

A

Emotional learning. Olfactory fear conditioning.

24
Q

Etorhinal cortex to the hippocampus is important for:

A

Memory formation

25
Q

How might a patient present with a loss of gustation and a loss of olfaction?

A

Everything is integrated in the medial orbitofrontal cortex

Ex: with a cold, thickened mucus blocks odorants from binding odorant receptors, example of reversible hyposmia

26
Q

Reversible hyposmia

Hyperosmia

A

Mucous may block odors from binding, like in a URI.

Can occur in migraines, psychotic states and pregnancy.

27
Q

What conditions would one have hyperosmia?

A

hyperosmia: increased smell

migraine, psychotic state, pregnancy

28
Q

What nutritional/physiological requirements does sweet receptors respond to?

A

presence of carbs that serve as energy source

29
Q

What nutritional/physiological requirements does salty receptors respond to?

A

intake of Na+ and other salts, essential for maintaining body water balance and blood circulation

30
Q

What nutritional/physiological requirements does umami receptors respond to?

A

reflect foods protein content due to glutamate presence and other AA

31
Q

What nutritional/physiological requirements does sour receptors respond to?

A

dietary acids: we avoid ingesting excess acids and overloading mechanisms that maintain acid-base balance. Spoiled food are often more acidic, thus avoided

32
Q

What nutritional/physiological requirements does bitter receptors respond to?

A

innately averse, thought to guard against poisons, which taste bitter to humans. As a result, bitter tuned GPCRs bind ligand with very high affinity compared to other taste receptors- developed as a means to protect against poison and toxic substance consumption

33
Q

what 3 cortical areas make up the gustatory cortex?

A
  1. postcentral gyrus
  2. frontal operculum
  3. insula
34
Q

Requirements of flavor perception

A
  1. gustatory input from gustatory cortex
  2. olfactory input from olfactory cortex
  3. somatosensory input from mouth
35
Q

Role of thalamus in taste

A

Neurons synapse on VPM which process discriminative aspects of taste

36
Q

Role of hypothalamus in taste

A

integrates homeostatic mechanisms of eating like hunger

37
Q

Role of amygdala in taste

A

emotional and memory of food/eating

38
Q

Role of orbitofrontal cortex in taste

A

integrates visual, somatosensory, olfaction, and gustation stimuli to appreciate food flavor

39
Q

role of granular and periglomerular cells in smell

A

local inhibitory interneurons that release GABA and increase specificity of signal

40
Q

anterior olfactory nucleus in smell perception

A

relay station to (bilateral) IPSI and CL cortices, poorly understood

41
Q

piriform cortex and lateral hypothalamus in smell perception

A

control of appetite and how olfactory inputs influences appetite and hunger

42
Q

piriform cortex and medial orbitofrontal cortex in smell perception

A

integration of sight, smell, and taste of food to appreciate flavor

43
Q

anterior cortical amygdaloid nuclei in smell perception

A

emotional learning and olfactory fear conditioning

44
Q

periamygdaloid cortex in smell perception

A

integrates emotional aspect of food as elicited by odor

45
Q

entorhinal cortex and hippocampus in smell perception

A

memory formation and how olfactory input facilitates both memory and recall.
-connections b/t limbic system and entorhinal cortex are responsible for highly evocative experience of memory upon smell

46
Q

what condition can olfactory testing be used for as a early diagnostic tool?

A

neurodegenerative diseases, especially Parkinsons where olfactory neurons are first to demonstrate pathology

47
Q

How are medications (typically have a bitter taste) altered for children consumption?

A
  • Add sodium salts (monosodium glutamate and sodium gluconate) which suppress bitter taste at the level of the bitter-receptor
  • Sugar suppresses bitterness at cognitive level
48
Q

How does sugar possibly act as an analgesic for infants?

A
  • Sweet taste induced beta-endorphin release, activating the endogenous opioid system
  • General brain arousal may be suppressed, leading infants to be distracted
49
Q

Signal transduction for smell neurons (6)

A
  1. voltage sensitive
  2. odorant bind rec
  3. stimulate G-olf 2nd messenger system
  4. depolarization
  5. AP if threshold reached
  6. NT release from central terminal of bipolar cells
50
Q

Signal transduction for taste neurons (5)

A
  1. relatively voltage insensitive
  2. Rec activates GPCR, 2nd messenger
  3. IC Ca+ release
  4. Depolarization
  5. Serotonin or ATP release onto peripheral terminal of primary afferent neuron
51
Q

taste ligands

A

tastants

-H+, AA, sugars, Na+, bitter components

52
Q

smell ligands

A

Odorants

-complex chemical compounds

53
Q

what sense is NOT relayed through thalamus?

A

smell (olfaction)

54
Q

why do older adults seem to add more salt to their foods?

A

gustatory sensitivity decreases with age

*Neuroendocrine Exam 3 (27 decks)

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