Physiology Of Olfaction And Gustation

Question 1

Sour Stimulus and NT Release

Answer 1

Stim: H+
-depolarizes and increase intracellular Ca2+ which causes release of NT

NT: Serotonin

Question 2

Salty Stimulus and NT Release

Answer 2

Stim: Na+ to ENaC
-increases Na, which depolarizers membrane and releases Ca++ intracellularly

NT: Serotonin

Question 3

Sweet Stimulus and NT Release

Answer 3

Stim: Sugars binding GPCR
-TRPM5 activation, deploarization and release of NT

NT: ATP

Question 4

Umami Stimulus and NT Release

Answer 4

Stim: Glutamate binging mGluR4
–TRPM5 activation, deploarization and release of NT

NT: ATP

Question 5

Bitter Stimulus and NT Release

Answer 5

Stim: Binding to GPCRs
-TRPM5 activation, deploarization and release of NT

NT: ATP

Question 6

Sensory Transduction in Taste Buds

Answer 6

Taste receptor proteins open voltage-regulated ion channels
-these open up second messengers that open the TRP receptors and Na+ channels
—this causes the cell to depolarize, which opens the Ca+ channels and cause NT vesicles to release and cause AP

Question 7

Sensory Transduction in Olfactory Neurons

Answer 7

Odorant molecules stuck in mucus binds to receptors and activates G(olf)
-activates adenylate Cyclase, which generates second messenger cAMP

-Opens Na+ and Ca2+ channels, which depolarizers the cell
—opening of a Ca2+ gated Cl- channels provide extra push

Question 8

Receptor Breakdown in olfactory neurons

Answer 8

Receptor potential is reduced when cAMP drops

-recovery also depends on calcium binding to calmodulin, which reduces affinity of channel for cAMP

Question 9

Why do we “get used” to a smell?

Answer 9

Sensitivity to CNGC to cAMP decreases, reducing cation influx

Or

Inactivation of receptor phosphorylation
-causes adaptation to smell

Question 10

Why do we avoid sour tastes?

Answer 10

Means presence of dietary acids, which are generally aversive
-do not want to disrupt acid-base balance

Also, spoiled foods are often acidic

Question 11

Why do we avoid bitter tastes?

Answer 11

Many poisons are bitter to humans, so they are avoided
-as a result, affinity of bitter-tuned GPCRs are very high compared to other modalities
—can sense poison at very low doses

Question 12

Are olfactory cues higher in children or adults?

Answer 12

Children

Question 13

What happens to an infant when they ingest sweets?

Answer 13

It has been shown to relax them, even to the point where it can be a mild analgesic

Cause is unknown, but mechanism is maybe sweet-tasted induced beta-endorphin release

Question 14

Nucleus of Solitary Tract

Answer 14

Early site of gustatory and visceral info

-reflex circuit for salivary secretions, mimetic responses of swallowing

Question 15

Discrimination of tastes processed here

Answer 15

VPM of thalamus

Question 16

What three areas make up Gustatory Cortex?

Answer 16

Insular taste cortex

Operculum of Frontal Lobe

Post-central gyrus

Question 17

What role do the hypothalamus and amygdala play in eating?

Answer 17

Emotion and memory of eating, integration of homeostatic mechanisms of eating (hunger), and interplay between eating and calming effects that take place in Limbic reward system

Question 18

Orbitofrontal cortex’s role in eating

Answer 18

Integrates visual, somatosensory, olfactory and gustatory stimuli to make us appreciate flavor of food

Question 19

Are taste and flavor the same thing?

Answer 19

Nope

Flavor requires gustatory info, olfactory info, and somatosensory info which come together in medial orbitofrontal cortex

Question 20

Olfactory Mucosa and Bulb

Answer 20

1. Olfactory Neurons Synapse onto Glomeruli and release Glutamate
   - at same time, periglomerular cells release GABA to increase specificity of signal
2. Mitral cells and tufted cells project to olfactory tract
   - granular cells release GABA here to increase specify of signal

Question 21

Anterior Olfactory nucleus

Answer 21

Relay station to ipsilateral and contralateral corticies

Question 22

What part of brain controls appetite and how olfactory input influences hunger?

Answer 22

Piriform cortex and lateral hypothalamus

Question 23

What part of brain integrates sight, smell, and taste of food to appreciate flavor?

Answer 23

Piriform cortex and medial orbitofrontal cortex

Question 24

What part of brain is important for emotional learning and olfactory fear?

Answer 24

Anterior cortical Amygdaloid nuclei

Question 25

What part of brain is important for emotional aspect of food brought on by the odor?

Answer 25

Periamygdaloid cortex

Question 26

What do the entorhinal cortex and hippocampus do with olfactory info in the brain?

Answer 26

Memory info and how olfactory input facilitates both memory and recall

Why some smells bring up certain memories