Physiology of Taste and Smell Flashcards
What occurs when taste receptors are signalled?
usually depolarizing –> opens voltage-gated Ca channels –> NT release
What NT do Sour and Salty taste receptors release and what does it signal?
Serotonin –> post-syn primary gustatory neurons
What NT do Sweet, Bitter, and Umami receptors release and what does that stimulate?
(these things give you energy)
ATP –> post-syn primary gustatory neurons
or pre-synaptic salty/sour recptor cells –> 5-HT
or Autocrine signaling
What is P2Y?
receptor for ATP
on SUB cells or Sour/Salty cells
What is P2X?
ATP receptor on SUB cells
(can do autocrine signaling)
How is salt allowed into taste receptors?
Na goes in via ENaC –> diffuses down gradient into cell –> depolarizes membrane –> increased Ca –> 5HT released
What molecule do sour foods use to stimulate taste receptors and what is its effect?
H+ from the acid –> inhibits potassium channels from flooding more + charges –> depolarization –> increased Ca –> 5-HT released
What type of receptor binds sweet, umami, and bitter flavors?
GPCR
all are Gq
What is the general mechanism of SUB taste cell signaling?
SUB molecule binds Gq GPCR –> PLC- IP3 –> increased intracellular Ca –> TRPM5 activation –> Na in –> depolarization –> release of ATP through PanxI channels = NT release
What is the specific receptor for umami flavors?
mGluR4 = GPCR for glutamate
Where are secondary sensory neuron cell bodies for the ascending taste pathway?
nucleus tractus solitarius
How does the brain integrate visual, somatosensory, olfaction, and gustatory stimuli?
VPM –> gustatory cortex –> orbitofrontal cortex
How does the brain do emotion and memory associated with eating/
Gustatory cortex –> amygdala
How does the brain integrate homeostatic mechanisms of eating (hunger)?
Hypothalamus –> nucleus tractus solitarius
Where do medularry reflex arcs occur (salivating, swallowing, etc)?
nucleus tractus solitarius
What type of cells are olfactory cells?
What are their receptor proteins?
bipolar neurons
GPCRs = Gs
What happens when an odorant binds its receptor?
binds Golf –> increased cAMP –> opes CNGC –> cation influx –> depolarization
How does odorant desensitization occur?
odorant persists –> sensitivity of CNGC to cAMP decreases –> reduces cation influx
or inactivated by receptor phophorylation
What is the relationship btw the number of odor receptors and a glomerulus?
one olfactory neuron expresses the same odorant receptor on all of its cilia
neurons with similar receptors all put their axons into the same glomerulus
How do we detect a ton of different odors w/ only ~350 odorant receptors?
one odorant can bind more than one type of OR
Patterns of OR binding –> different smells
What NT do granular cells and periglomerular cells release?
GABA –> increases specificity of signal
What type of NT do ORNs release?
glutamate
What is the major difference btw taste receptors and olfactory receptors?
taste = modified epithelial cells
olfactory receptors = neurons
What part of the brain is essential for perception of flavor?
gustatory and olfactory cortices =
medial orbitofrontal cortex
