PHYS physiology of olfaction and gustation Flashcards
5 taste categories:
ATP - channel?
5-HT
ATP: PanX1 channel
sweet
umami
bitter
5-HT
sour
saltyATP released from sweet umami bitter receptor cells stimulate
post-synaptic gustatory neurons
pre-synaptic salty/sour receptor cells to stimulate 5-HT
release
autocrine signaling
5-HT released from salty/sour receptor cells stimulate
post-synaptic primary gustatory cells
what evokes sour receptors
what happens when sour receptors are evoked
H+ ions
inhibits K channels from flooding additional positive charge into the cell –> depol.
sweet, umami, bitter receptor pathway
GPCR (PLC/IP3 pathway) –> increased Ca –> TRPM5 (Na) –> depol –> release of ATP through panx1 –> NT release
what GPCR does the umami pathway
mGluR4
why does the bitter pathway have the highest affinity GPCR
POISON
where do all taste tracts terminate
nucleus tractus solitarius (gustatory area)
ascending taste pathway
–>nucleus tractus solitarius –> VPM –posterior limb of IC–> postcentral gyrus, frontal operculum, insular cortex
which 3 cortical areas are referred to as the gustatory cortex
postcentral gyrus
frontal operculum
insular cortex
what is responsible for integrating visual, somatosensory, olfaction and gustatory stimuli
orbitofrontal cortex
what is responsible for the affective aspects of eating, emotional context to eating, and memories of eating
amygdala
what is responsible for the integration of homeostatic mechanisms of eating (hunger)
hypothalamus
olfactory g protein pathway
Golf –> cAMP –> opens cyclic nucleotide gated channels (CNGC) –> cation influx –> depol
describe adaptation of smell
as odorant persists:
1) sensitivity of CNGC to cAMP decreases
or
2) inactivated by receptor phosphorylation
what factors can affect how we percieve a smell
combination of odorant receptors activated
concentration of odorant
inhibitory interneurons of the olfactory bulb
granular cells
paraglomerular cells
f(x) anterior olfactory nucleus
???
relay station to ipsi- and contralateral cortices
f(x) of piriform cortex –> lateral hypothalamus
control of appetite
olfactory input influences appetite and hunger
f(x) of piriform cortex –> thalamus –> medial orbitofrontal cortex
integration of taste sight and smell
appreciation of the flavor of food
f(x) of anterior cortical amygdaloid nucleus
emotional learning; olfactory fear conditioning
f(x) of periamygdaloid cortex
integration of emotional aspect elicited by odor
f(x) of entorhinal cortex –> hippocampus
important in memory formation
olfactory input facilitates both memory formation and recall
what does perception of flavor require
gustatory input from gustatory cortex
olfactory input from olfactory cortex (esp piriform cortex)
somatosensory info from the mouth
medial orbitofrontal cortex
