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Neuroendocrine I: Exam 3 > Physiology of Gustation and Olfaction > Flashcards

Physiology of Gustation and Olfaction Flashcards

1
Q

What stimulus and subsequent NT release allows for the taste sensation of: sour

A
  • Stimulus is through H+ ions (acid)

- NT = Serotonin

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2
Q

What stimulus and subsequent NT release allows for the taste sensation of: Salty

A
  • Stimulus: Na+ binding epithelial Na+ channel (ENaC)

- NT: Serotonin

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3
Q

What stimulus and subsequent NT release allows for the taste sensation of: Sweet

A
  • Stimulus: sugars binding GPCR

- NT: ATP

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4
Q

What stimulus and subsequent NT release allows for the taste sensation of: Umami

A
  • Stimulus: mGluR4 (GPCR)

- NT: ATP

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5
Q

What stimulus and subsequent NT release allows for the taste sensation of: Bitter

A
  • Stimulus: various compounds binding GPCR

- NT: ATP

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6
Q

Sensory Transduction in odorant receptor neurons (ORN)

A
  1. Odorants diffuse into nasal mucus, binds olfactory receptor proteins (G_olf) on olfactory cilia and activates olfactory cell
  2. Activated G_olf activates adenylate cyclase to convert ATP –> cAMP (second messenger)
  3. cAMP binds and opens cyclic-nucleotide gated channels (CNGC) to allow Na+ and Ca2+ to influx into cell
  4. Increased [Ca2+] causes Ca2+-gated Cl- channels to open and resultant Cl- outflow to depolarize the cell
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7
Q

Mechanisms of olfactory receptor neuron (ORN) adaptation to smell

A
  1. Receptor potential reduced in magnitude as cAMP is enzymatically broken down
  2. Ca2+ binding calmodulin reduces cyclic-nucleotide gated channels affinity for cAMP
  3. Odorant receptor itself can become phosphorylated to decrease its sensitivity to the odorant
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8
Q

Physiological significance of: Bitter foods

A
  • Innately aversive to guard against poisons –> GPCRs have a higher binding affinity to this ligand than the other tastes
  • Detects poisons at low [] to avoid additional ingestion
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9
Q

Physiological significance of: Sweet foods

A

-Signal presence of carbohydrates (energy source)

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10
Q

Physiological significance of: Salty foods

A

-Governs Na+ and other salt intake to maintain body’s water balance and blood circulation

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11
Q

Physiological significance of: Umami

A

-Reflects a food’s protein content based on presence of AA (especially glutamate)

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12
Q

Physiological significance of: Sour

A
  • Generally aversive b/c avoid ingesting excess acids which can overload acid-base balance + spoiled foods are often acidic
  • Signals presence of dietary acids
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13
Q

Age-related decrease in gustatory sensitivity

A
  • Especially after 60 yo
  • Mouth produces less saliva
  • # taste buds decreases and remaining taste buds shrink in size
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14
Q

Age-related decrease in olfactory sensitivity

A
  • Especially after 70 yo
  • Decreased nasal mucus production
  • Fibers and receptors of odorant receptor neurons decrease w/ age
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15
Q

Mechanisms causing analgesic effect of sweet-solutions

A
  1. Anti-nociceptive action - most widely accepted mechanism is sweet-tasted induced beta-endorphin release which activates endogenous opioid system
  2. General brain arousal may be suppressed –> distraction
  3. Rewarding effect of sweet flavors blunts stress-response –> calmer affect
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16
Q

What are some chemically-induced ways to suppress bitter taste?

A
  • Sodium salts (e.g. monosodium glutamate and sodium gluconate) suppress @ lvl of the bitter-receptor
  • Sugars suppress @ cognitive lvl b/c this receptor is more prominent in brain
17
Q

Name the inputs required for the perception of flavor

A
  1. Gustatory input from gustatory cortex
  2. Olfactory input from olfactory cortex
  3. Somatosensory information from mouth
    * All these factors come together in the medial orbitofrontal cortex
18
Q

Function in processing taste: Nucleus tractus solitarius

A
  • Early site of gustatory-visceral integration
  • Receives inputs from CN VII, IX and X, as well as, from amygdala and hypothalamus
  • Projects to the ventral posteromedial nucleus of the thalamus
19
Q

Function in processing taste: ventral posteromedial nucleus (VPM) of thalamus

A
  • Relay station for taste perception
  • Begins discriminative aspects of taste
  • Receives input from nucleus tractus solitarius and projects to the gustatory cortex (post-central gyrus, frontal operculum and insula)
20
Q

Function in processing taste: gustatory cortex (Post-central gyrus, frontal operculum and insula)

A
  • Discriminative aspects of taste
  • Receives information from ventral posteromedial nucleus of the thalamus and projects to the amygdala and the orbitofrontal cortex
21
Q

Function in processing taste: orbitofrontal cortex

A
  • Integrates visual (what food looks like), somatosensory (texture of food), olfaction (smell of food) and gustatory (taste of food) stimuli
  • Receives input from the gustatory cortex (post-central gyrus, frontal operculum and insula)
22
Q

Function in processing taste: amygdala

A
  • Affective aspects of eating, emotional context to eating and memories of eating
  • Receives information from the gustatory cortex and projects back to the nucleus tractus solitariius
23
Q

Function in processing taste: hypothalamus

A
  • Integrates homeostatic mechanisms of eating (e.g. hunger)

- Projects to the nucleus tractus solitarius

24
Q

Function in processing taste: Limbic system

A

-Interplay b/w eating and calming effects of food involves limbic and reward systems

25
Q

Function in processing taste: medullary reflex arcs

A
  • Forms basis for salivating, mimetic responses and swallowing
  • Takes place w/in medulla and involves the nucleus tractus solitarius
26
Q

What brain structures make up the olfactory cortex?

A
  • Anterior olfactory nucleus
  • Olfactory tubercle
  • Piriform cortex
  • Anterior cortical amygdaloid nuclei
  • Periamygdaloid cortex
  • Lateral entorhinal cortex
27
Q

What brain structures make up the gustatory cortex ?

A
  • Post-central gyrus
  • Frontal operculum
  • insula
28
Q

Function in processing olfaction: anterior olfactory nucleus

A
  • Relay station to ipsilateral and contralateral cortices

- Poorly understood

29
Q

Function in processing olfaction: piriform cortex

A
  1. Projects to the lateral hypothalamus to control appetite
  2. Projects to the thalamus and then to the medial orbitofrontal cortex to integrate taste, sight and smell in order for us to appreciate flavor of food
30
Q

Function in processing olfaction: anterior cortical amygdaloid nucleus

A
  • Emotional learning

- Olfactory fear conditioning

31
Q

Function in processing olfaction: periamygdaloid cortex

A

-Integration of emotional aspect elicited by odor

32
Q

Function in processing olfaction: entorhinal cortex

A
  • Projects to the hippocampus and is important for memory formation
  • Olfactory input facilitates memory formation and recall (memory paired w/ olfactory input will form a stronger synapse)
  • Connections w/in limbic system and entorhinal cortex responsible for highly evocative experience of memory upon odor sensation
33
Q

Which places does adult neurogenesis occur in the brain?

A
  1. Olfactory bulb

2. Dentate gyrus of hippocampus

Neuroendocrine I: Exam 3 (18 decks)

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