Physiology Of Taste And Olfaction Flashcards
What is anosmia?
Loss of smell
What is augesia?
Loss of taste
What are tastants?
Chemical compounds that bind taste receptors and impart primary flavor categories (sweet, salty, bitter, sour, umami)
What are odorants?
Chemical compounds that bind odorant receptors that impart an odor
What is the stimulus and NTR for
SOUR?
Stimulus: H+ ions
NTR: Serotonin
What is the stimulus and NTR for
SALTY?
Stimulus: Na+ Binding ENaC
NTR: Serotonin
What is the stimulus and NTR for
SWEET?
Stimulus: sugars binding GPCRs
NTR: ATP
What is the stimulus and NTR for
UMAMI?
Stimulus: Glutamate binding mGluR4 (GPCR)
NTR: ATP
What is the stimulus and NTR for
BITTER?
Stimulus: Various compounds binding GPCRs
NTR: ATP
What is the strucutre of taste buds?
Specialized epithelial cells w/ distinct apical and basal domains
What is the chemosensory transduction involved with TASTE buds?
Apical domain—> electrical signals via GPCRs to basal domain —> NTR —> local afferents —> potential AP
Where are TASTE receptor proteins and related signaling molecules involved in chemosensory transduction concentrated?
On microvilli that emerge from apical surface of taste bud
What does the apical surface of taste buds contain?
Voltage regulated ionchannel
Channels w/ second messengers (especially Transient receptor potential receptor family (TRP))
What will allow the release of NTRs from the basal domain of taste buds?
Intracellular Ca release
What kind of neurons are olfactory cells?
Bipolar neurons
What NTR will olfactory nuerons release?
Glutamate
What is the chemosensory transduction pathway for SMELL?
Odorant —> mucus —> G-protein (Golf) activated —> adenylate cyclase activated —> cAMP generated —> Cyclic nucleotide gated channels opens (CNGC) —> Na and Ca influx —> depolarization —> Ca gated Cl channels open —> future depolarization —> receptor potential —> action potential
What will cause a reduction in the magnitude of receptor potential for the chemosensory transduction of taste and smell?
Enzymatic breakdown of cAMP
Reduced affinity for channel to cAMP bc Ca binds Calmodulin
What will elicit a robust response from odorant receptors?
Pleasant or pungent odors
What modifies the sensitivity of odorant receptors to odorants?
Phosphorylation
What will allow one to get “used” to a smell and no longer notice its strength?
Phosphorylation of odorant receptors
What happens when the odorant stimuli persists?
Sensitivity of CNCG to cAMP decreases and thus reduces cation influx = no more depolarization
Or
CNGC inactivated via receptor phosphorylation
What happens in regards to smell during Upper Respiratory infections?
Thickened mucus blocks odorants from binding odorant receptors
= reversible hyposmia
What is HYPERosmia seen in?
Migraine
Psychotic states
Pregnancy