Flashcards in Physio of Olfaction and Gustation Deck (43)
What is anosmia?
loss of sense of smell
What is ageusia?
loss of sense of taste
Chemosensory transduction is initiated in the ____ domain.
Electrical signals are generated at the ____ domain via graded receptor potentials and release of neurotransmitters.
What does intracellular calcium release facilitate?
synaptic vesicle fusion and extrusion of contained neurotransmitters to be released into the basal synapse with local afferents
What does the activation of the afferent primary sensory neuron generate?
A receptor potential that if large enough may induce an action potential
What is the stimulus and NT of sour taste?
H+ ions; serotonin
What is the stimulus and NT of salty taste?
Na+ binding ENaC (epithelial sodium channel); serotonin
What is the stimulus and NT of sweet taste?
sugars binding GPCRs; ATP
What is the stimulus and NT of umami?
glutamate binding mGluR4 (GPCR); ATP
What is the stimulus and NT of bitter taste?
various compounds binding GPCRs; ATP
Olfactory cells are bipolar neurons that release _____ as their primary neurotransmitter.
Odorants in the mucus directly bind to one of the receptor molecules located in the membranes of the cilia, activating ____.
G_olf, an odorant specific G-protein
G_olf activates _____ which generates _____.
adenylyl cyclase; cAMP
cAMP opens cyclic nucleotide gated channels (CNGC) leading to ......
cation influx (Na+ & Ca+) resulting in depolarization, which results in an opening of Ca++-gated Cl- channels that provide the remainder of the depolarization of the membrane needed to generate an AP.
As odorant stimulation persists, sensitivity of the CNGC to cAMP decreases, reducing ____ _____. Also, the odorant receptor itself can become _____ which inactivates the receptor leading to desensitization.
cation influx; phospharylated
Bitter taste is innately aversive. Why is this and what does this do to our bitter-tuned GPCRs?
Bitter taste is innately aversive and is thought to guard against consuming poisons. Bitter-tuned GPCRs bind their ligand with very high binding affinity compared to other taste receptors in order to detect potentially poisonous compounds and very low concentrations.
Why do old people add more salt to their food? Why is this a problem?
Gustatory and olfactory sensitivity declines with age. This is a problem because increased salt intake in patients with HTN can cause fluid overload.
Why is sugar used as an analgesic in newborns?
Newborns respond to dilute sweet tastes, seen by relaxation of the face and neural imaging showing a response similar to pleasurable sensation. Small amounts of a sweet solution placed on the tongue of a crying newborn exert a rapid, calming effect along with decreased HR that persists for several minutes.
What is the most widely accepted mechanism of the analgesic effect of sugar?
The most widely accepted mechanism is a sweet-tasted induced beta-endorphin release, activating the endogenous opioid system.
Why is there an age-related decline in preference for sweetness?
Basically, children need extra calories during growth, so carbs are less important once reaching childhood; however, this is truly unknown.
What is added to liquid medications, alcohol, and caffeinated drinks and why are they added?
Active pharmaceutical ingredients are by their nature bitter, so sodium salts and sugar are added.
Sodium salts suppress bitter taste at the level of the ________.
Sugars suppress the taste of bitterness at the _____ level.
Where is the first synapse in the gustatory pathway?
Axons from the solitary nucleus travel through the ____ _____ _____ on their way to synapse in the ______ _____ _____ _____.
central tegmental tract; ventral posterior medial nucleus of the thalamus (VPM)
Axons from the VPM travel through the _______________ before synapsing at the ____ cortex.
posterior limb of the internal capsule; gustatory
The gustatory cortex is comprised of what three areas?
anterior insular cortex, frontal operculum, and the post-central gyrus (specifically the rostral area of Brodmann area 3b).
What is the amygdala's role in gustation?
Affective aspects of eating, emotional context to eating, and memories of eating.