Physiology of Olfaction and Gustation Flashcards
loss of the sense of smell
anosmia
loss of sense of taste
aguesia
taste buds are what type of cell?
specialized epithelia cells
the apical domain of taste buds contain what?
microvilli, tastant receptors, voltage-gated ion channels, and TRP receptors
what is the NT released when sours (H+ ions) tastants bind?
serotonin
what is the NT released when salty (Na+ ions) bind?
serotonin
what is the NT released when sugars bind to the GPCR?
ATP
where does glutamate bind to?
an mGluR4 GPCR
what is released when glutamate (umami) binds to it’s receptor?
ATP
what is released when bitter compounds bind to their GPCR?
ATP
olfactory cells are what type of neurons?
bipolar neurons
what do olfactory cells release as their NT?
glutamate
what is the olfactory receptor for odorants?
GPCR (Golf)
what is the second messenger in the olfactory receptor neuron?
cAMP
what does cAMP open in the olfactory receptor neuron?
cyclic-nucleotide gated channels
what is the role of the cyclic-nucleotide gated channels?
they allow Na+ and Ca2+ to influx into the cell and depolarization occurs
what are the three mechanisms for olfactory receptor neuron adaptation to a smell?
enzymatic breakdown of cAMP, reduced affinity for cAMP, Golf can become phosphorylated
what is specific to bitter tastes?
the bitter-tuned GPCRs bind their ligand with very high affinity compared to the other taste receptors
what happens to sensitivity as we age?
there is a decrease in sensitivity
when does the sense of smell and taste begin?
in utero
why is there an analgesic effect of sweet-solutions for infants?
anti-nociceptive action- sweet-tasted induced beta-endorphin release
what does sweet-tasted induced beta endorphin release activate?
endogenous opioid system
how can you suppress a bitter taste at the level of the bitter-receptor?
by using sodium salts (most commonly is MSG)
how can you suppress the sense of bitterness at the cognitive level?
sugars
the gustatory cortex is made up of three cortical areas. What are they?
post central gyrus, frontal operculum, and the insula
facial nerve (VII), glossopharyngeal nerve (IX), vagus nerve (X) send their information where?
to the nucleus tractus solitarius
what is the nucleus tractus solitarius?
it is an early site of gustatory-visceral integration
where does the information go after the nucleus tractus solitarius?
to the VPM of the thalamus
what is the purpose of the VPM?
it is the relay station for taste perception. Begins discriminative aspects of tast
where does the VPM send it’s information from the NTS?
to the gustatory cortex
where does the gustatory cortex send its information from the VPM?
to the orbitofrontal cortex
what is the role of the orbitofrontal cortex?
it integrates visual, somatosensory, olfaction, and gustatory stimuli
what is the role of the amygdala in gustation?
affective aspects of eating, emotional context to eating, and memory of eating
what is the role of the medullary reflex arcs?
forms basis for salivating, mimetic responses and swallowing
the projections of similar odorant receptors are collected into what?
one glomerulus
glomerulus cells send a projection where?
mitral/tufted cell
what is the only sensory system that does not route through the thalamus before connecting to the cortex?
the olfactory system
what is the role of the piriform cortex–> the lateral hypothalamus?
it controls appetite and hunger
what is the role of the piriform cortex–> thalamus–> medial orbitofrontal cortex?
integration of taste, sight, and smell; appreciation of the flavor of food
what is the role of the anterior cortical amygdaloid nucleus?
emotional learning; olfactory fear conditioning
what is the role of the periamygdaloid cortex?
integration of emotional aspect elicited by odor
what is the role of the entorhinal cortex–> hippocampus?
important in memory formation; memory upon odor sensation
adult neurogenesis is thought to occur in two places in the brain. Where?
the olfactory bulb and the dentate gyrus of the hippocampus
in what disease are neurons of the olfactory system among the first to demonstrate pathology?
parkinson disease
