Physio of Olfaction and Gustation

Question 1

What is anosmia?

Answer 1

loss of sense of smell

Question 2

What is ageusia?

Answer 2

loss of sense of taste

Question 3

Chemosensory transduction is initiated in the ____ domain.

Answer 3

apical

Question 4

Electrical signals are generated at the ____ domain via graded receptor potentials and release of neurotransmitters.

Answer 4

basal

Question 5

What does intracellular calcium release facilitate?

Answer 5

synaptic vesicle fusion and extrusion of contained neurotransmitters to be released into the basal synapse with local afferents

Question 6

What does the activation of the afferent primary sensory neuron generate?

Answer 6

A receptor potential that if large enough may induce an action potential

Question 7

What is the stimulus and NT of sour taste?

Answer 7

H+ ions; serotonin

Question 8

What is the stimulus and NT of salty taste?

Answer 8

Na+ binding ENaC (epithelial sodium channel); serotonin

Question 9

What is the stimulus and NT of sweet taste?

Answer 9

sugars binding GPCRs; ATP

Question 10

What is the stimulus and NT of umami?

Answer 10

glutamate binding mGluR4 (GPCR); ATP

Question 11

What is the stimulus and NT of bitter taste?

Answer 11

various compounds binding GPCRs; ATP

Question 12

Olfactory cells are bipolar neurons that release _____ as their primary neurotransmitter.

Answer 12

glutamate

Question 13

Odorants in the mucus directly bind to one of the receptor molecules located in the membranes of the cilia, activating ____.

Answer 13

G_olf, an odorant specific G-protein

Question 14

G_olf activates _____ which generates _____.

Answer 14

adenylyl cyclase; cAMP

Question 15

cAMP opens cyclic nucleotide gated channels (CNGC) leading to ……

Answer 15

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.

Question 16

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.

Answer 16

cation influx; phospharylated

Question 17

Bitter taste is innately aversive. Why is this and what does this do to our bitter-tuned GPCRs?

Answer 17

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.

Question 18

Why do old people add more salt to their food? Why is this a problem?

Answer 18

Gustatory and olfactory sensitivity declines with age. This is a problem because increased salt intake in patients with HTN can cause fluid overload.

Question 19

Why is sugar used as an analgesic in newborns?

Answer 19

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.

Question 20

What is the most widely accepted mechanism of the analgesic effect of sugar?

Answer 20

The most widely accepted mechanism is a sweet-tasted induced beta-endorphin release, activating the endogenous opioid system.

Question 21

Why is there an age-related decline in preference for sweetness?

Answer 21

Basically, children need extra calories during growth, so carbs are less important once reaching childhood; however, this is truly unknown.

Question 22

What is added to liquid medications, alcohol, and caffeinated drinks and why are they added?

Answer 22

Active pharmaceutical ingredients are by their nature bitter, so sodium salts and sugar are added.

Question 23

Sodium salts suppress bitter taste at the level of the ________.

Answer 23

bitter-receptor

Question 24

Sugars suppress the taste of bitterness at the _____ level.

Answer 24

cognitive

Question 25

Where is the first synapse in the gustatory pathway?

Answer 25

Solitary nucleus

Question 26

Axons from the solitary nucleus travel through the ____ _____ _____ on their way to synapse in the ______ _____ _____ _____.

Answer 26

central tegmental tract; ventral posterior medial nucleus of the thalamus (VPM)

Question 27

Axons from the VPM travel through the _______________ before synapsing at the ____ cortex.

Answer 27

posterior limb of the internal capsule; gustatory

Question 28

The gustatory cortex is comprised of what three areas?

Answer 28

anterior insular cortex, frontal operculum, and the post-central gyrus (specifically the rostral area of Brodmann area 3b).

Question 29

What is the amygdala's role in gustation?

Answer 29

Affective aspects of eating, emotional context to eating, and memories of eating.

Question 30

What is the hypothalamus's role in gustation?

Answer 30

Integration of homeostatic mechanisms of eating, like hunger.

Question 31

What is the role of the orbitofrontal cortex in gustation?

Answer 31

Integrating visual, somatosensory, olfaction, and gustatory stimuli to collectively appreciate the flavor of food.

Question 32

What does GRow My EGO stand for?

Answer 32

Granule cell layer, mitral cell layer, external plexiform layer, glomerular layer, and olfactory nerve layer.

Question 33

Olfactory neurons synapse onto ____ and release _____.

Answer 33

glomeruli; glutamate

Question 34

Periglomerular cells are local interneurons and release ____ which _____ _____ of the signal.

Answer 34

GABA; increases specifity

Question 35

What do mitral cells and tufted cells project to?

Answer 35

olfactory tract

Question 36

Granular cells are local interneurons and release ____.

Answer 36

GABA

Question 37

What is the anterior olfactory nucleus?

Answer 37

A relay station to ipsilateral and contralateral cortices.

Question 38

What do the piriform cortex and lateral hypothalamus do when working together?

Answer 38

Controls appetite and how olfactory input influences appetite and hunger.

Question 39

What do the piriform cortex and medial orbitofrontal cortex do when working together?

Answer 39

integration of sight, smell, and taste of food; appreciation of the flavor of food

Question 40

What does the anterior cortical amygdaloid nucelus do?

Answer 40

emotional learning and olfactory fear conditioning

Question 41

What does the periamygdaloid cortex do?

Answer 41

integration of the emotional aspect of food as ellicited by odor

Question 42

What do the entorhinal cortex and hippocampus do when working together?

Answer 42

memory formation and how olfactory input faciliates both memory and recall

Question 43

In what disease are neurons of the olfactory system among the first to demonstrate pathology, even years before other symptoms?

Answer 43

Parkinson's disease