Physiology of Olfaction and Gustation

Question 1

What is the loss of sense of smell called?

Answer 1

Anosmia

Question 2

What is the loss of sense of taste called?

Answer 2

Aguesia

Question 3

What are tastants?

Answer 3

Chemical compounds that bind to taste receptors and impart the primary flavor categories

Question 4

What are odorants?

Answer 4

Chemical compounds that bind odorant receptors and impart odor

Question 5

What tastants are associated with ion channels and serotonin release?

Answer 5

Sour and salty

Question 6

What tastants are associated with GPCRs and ATP release?

Answer 6

Sweet, umami, bitter

Question 7

What compound binds GPCRs for umami taste?

Answer 7

Glutamate binds mGluR4

Question 8

What happens after the tastant binds the GPCR or enters the ion channel?

Answer 8

Intracellular calcium release facilitates synaptic vesicle fusion with the basal membrane to release NTs onto the primary sensory neuron to induce an AP

Question 9

How do taste cells and olfactory cells differ?

Answer 9

Taste cells are specialized epithelial cells

Olfactory cells are bipolar neurons that release glutamate

Question 10

What happens after an odorant binds to a receptor molecule?

Answer 10

A specific G protein is activated that activates adenylate cyclase, resulting in cAMP generation and then an influx of Na+ and Ca2+. This results in depolarization which causes calcium-gated Cl- channels to open. Cl- leaves to further depolarize the cell

Question 11

What happens to reduce odorant receptor potential?

Answer 11

cAMP is broken down and calcium binds to calmodulin. The receptor can also be phosphorylated to decrease sensitivity to odorants (happens when you “get used to” a smell)

Question 12

What do sweet tastes signal to the brain?

Answer 12

Presence of carbs aka energy source

Question 13

What do salty tastes govern?

Answer 13

Intake of Na+, essential for maintaining water balance and blood circulation

Question 14

What do umami tastes signal to the brain?

Answer 14

Protein content (glutamate and other amino acids)

Question 15

What do sour tastes signal to the brain?

Answer 15

Dietary acids, also indicates spoiled food

Question 16

What do bitter tastes signal to the brain?

Answer 16

Guards against consuming poisons

Question 17

Which taste has the highest binding affinity to its receptors?

Answer 17

Bitter tastes

Question 18

Why do adults tend to add more salt and spices to food than children do?

Answer 18

Taste and smell sensitivity declines with age :(

Question 19

When do sensation of smell and taste begin?

Answer 19

In utero to prime the fetus to tastes in the external environment

Question 20

What can be used to reduce procedural pain in infants? How does this work?

Answer 20

Sucrose/sweetness - only for single painful events. Believed to be due to induced beta-endorphin release activating the endogenous opioid system

Question 21

How can bitter taste be masked?

Answer 21

Sodium salts at the level of the bitter-receptor

Sugars at the cognitive level

Question 22

How is the nucleus of the solitary tract involved in processing of taste?

Answer 22

Early site of gustatory and visceral information: receives inputs from Vagus N.

Question 23

How is the VPM of the thalamus involved in the processing of taste?

Answer 23

Relay station for taste perception, processes discriminative aspects of taste

Question 24

What makes up the gustatory cortex?

Answer 24

Insular taste cortex
Operculum of frontal lobe
Post-central gyrus

Question 25

How are the hypothalamus and amygdala involved in the processing of taste?

Answer 25

Amygdala- emotional context to eating, memories of eating

Hypothalamus- homeostatic mechanisms like hunger

Question 26

How is the orbitofrontal cortex involved in the processing of taste?

Answer 26

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

Question 27

How is the anterior olfactory nucleus involved in the processing of smell?

Answer 27

Relay station to ipsilateral and contralateral cortices, poorly understood

Question 28

How are the piriform cortex and lateral hypothalamus involved in the processing of smell?

Answer 28

Control appetite and how smells influence appetite/hunger

Question 29

How are the piriform cortex and medial orbitofrontal cortex involved in the processing of smell?

Answer 29

Integrate sight, smell, and taste of food to appreciate flavor of food

Question 30

How is the anterior cortical amygdaloid nuclei involved in the processing of smell?

Answer 30

Emotional learning and olfactory fear conditioning

Question 31

How is the periamygdaloid cortex involved in the processing of smell?

Answer 31

Integrates emotional aspect of food as elicited by odor

Question 32

How are the entorhinal cortex and hippocampus involved in the processing of smell?

Answer 32

How olfactory information facilitates both memory and recall, responsible for highly evocative experience of memory upon odor sensation

Question 33

What part of the taste bud is involved in chemosensory transduction?

Answer 33

the Apical domain

Basal domain—>electrical signaling