Physiology Of Olfaction And Gustation Flashcards
(26 cards)
Sour Stimulus and NT Release
Stim: H+
-depolarizes and increase intracellular Ca2+ which causes release of NT
NT: Serotonin
Salty Stimulus and NT Release
Stim: Na+ to ENaC
-increases Na, which depolarizers membrane and releases Ca++ intracellularly
NT: Serotonin
Sweet Stimulus and NT Release
Stim: Sugars binding GPCR
-TRPM5 activation, deploarization and release of NT
NT: ATP
Umami Stimulus and NT Release
Stim: Glutamate binging mGluR4
–TRPM5 activation, deploarization and release of NT
NT: ATP
Bitter Stimulus and NT Release
Stim: Binding to GPCRs
-TRPM5 activation, deploarization and release of NT
NT: ATP
Sensory Transduction in Taste Buds
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
Sensory Transduction in Olfactory Neurons
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
Receptor Breakdown in olfactory neurons
Receptor potential is reduced when cAMP drops
-recovery also depends on calcium binding to calmodulin, which reduces affinity of channel for cAMP
Why do we “get used” to a smell?
Sensitivity to CNGC to cAMP decreases, reducing cation influx
Or
Inactivation of receptor phosphorylation
-causes adaptation to smell
Why do we avoid sour tastes?
Means presence of dietary acids, which are generally aversive
-do not want to disrupt acid-base balance
Also, spoiled foods are often acidic
Why do we avoid bitter tastes?
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
Are olfactory cues higher in children or adults?
Children
What happens to an infant when they ingest sweets?
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
Nucleus of Solitary Tract
Early site of gustatory and visceral info
-reflex circuit for salivary secretions, mimetic responses of swallowing
Discrimination of tastes processed here
VPM of thalamus
What three areas make up Gustatory Cortex?
Insular taste cortex
Operculum of Frontal Lobe
Post-central gyrus
What role do the hypothalamus and amygdala play in eating?
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
Orbitofrontal cortex’s role in eating
Integrates visual, somatosensory, olfactory and gustatory stimuli to make us appreciate flavor of food
Are taste and flavor the same thing?
Nope
Flavor requires gustatory info, olfactory info, and somatosensory info which come together in medial orbitofrontal cortex
Olfactory Mucosa and Bulb
- Olfactory Neurons Synapse onto Glomeruli and release Glutamate
- at same time, periglomerular cells release GABA to increase specificity of signal - Mitral cells and tufted cells project to olfactory tract
- granular cells release GABA here to increase specify of signal
Anterior Olfactory nucleus
Relay station to ipsilateral and contralateral corticies
What part of brain controls appetite and how olfactory input influences hunger?
Piriform cortex and lateral hypothalamus
What part of brain integrates sight, smell, and taste of food to appreciate flavor?
Piriform cortex and medial orbitofrontal cortex
What part of brain is important for emotional learning and olfactory fear?
Anterior cortical Amygdaloid nuclei
