Chapter 15: Gustation

Question 1

Gustation

Answer 1

Assesses quality of material entering system

• Basic tastes

Question 2

Basic tastes

Answer 2

5 well-established taste categories- sweet, salty, umami, sour, and bitter

Question 3

Nutritive tastes

Answer 3

Sweet, salty, and umami

Question 4

Non-nutritive tastes

Answer 4

Sour and bitter

Question 5

Flavor perception

Answer 5

More complex and multidimensional than taste perception

Question 6

Tastants

Answer 6

Molecules that taste receptors “recognize” and respond to by producing neural signals that brain represents as perception of different tastes

Question 7

Flavor

Answer 7

total sensory experience evoked by ingesting something
- includes perception of basic tastes, perception of basic tastes, perception of other attributes of tastants, such as pleasantness and intensity, and other sensory properties, most importantly smell

Affected by many things other than taste

*olfaction, hunger/thirst, vision, audition, and mouth feeling

Question 8

Taste and Flavor

Answer 8

• Sweet- sucrose, fructose, glucose
• Salty- NaCl, KCl, LiCl
• Umami- monosodium glutamate, L-arginine, L-glutamine
  - signals presence of protein in food
• Bitter- quinine, caffeine, PROP
• Sour- citric acid, acetic acid, hydrochloric acid

Question 9

Trigeminal Sense

Answer 9

Sense that signals presence of irritants in mouth, such as menthol and chili pepper

• contributes to “mouth feel” of foods

Question 10

Taste buds

Answer 10

Structures that contain taste receptor cells, within papillae in mouth

Question 11

Perceiving Tastes and Flavors

Answer 11

Taste buds and taste receptor cells (TRCs)

Question 12

Anatomical and neural basis of taste and flavor perception

Answer 12

On tongue, taste buds are found in three of the four types of papillae

• fungiform, folliate and circumvallate
• filiform do not contain taste buds

Question 13

Fungiform papillae

Answer 13

Tiny mushroom- shaped structure located along edges and top of front two-thirds of tongue

• 3-5 taste buds on upper surface

Question 14

Folliate papillae

Answer 14

Ridgelike folds of tissue located on sides of tongue neat the back

• few hundred taste buds are tucked into each fold

Question 15

Circumvallate papillae

Answer 15

Larger mushroom- shaped structures situated in row at back of tongue

• contains 200- 700 taste buds around its side

Question 16

Filiform

Answer 16

Manipulate food on tongue

Question 17

1/3 of taste buds are found on […]

Answer 17

1/3 of taste buds are found on soft palate, epiglottis, and upper esophagus

Question 18

Free nerve endings

Answer 18

Trigeminal nerve- how something feels in mouth (non-taste) factors

Question 19

We have […] taste buds each of which have […] taste receptor cells

Answer 19

We have 3000-12000 taste buds each of which have 40000-100000 taste receptor cells

Question 20

Taste receptors cells (TRCs)

Answer 20

Elongated neurons, packed within taste buds, that transduce tastants into neural signals

• TRCs only live about 1 week
  - New TRCs developed from basal cells in taste buds
• Cilia of TRCs project into taste pore at top of taste bud, when cilia come into contact with tastants molecules dissolved in saliva

Question 21

There are two types of TRCs

Answer 21

Receptor cells

Presynaptic cells

Question 22

Receptor cells

Answer 22

Type of taste receptor cells containing receptors that initiate transduction of sweet, umami, and bitter tastants

• do not have synapses with cranial nerve fibers, GPCRs

Question 23

Presynaptic cells

Answer 23

Type of receptor cells in which receptors take form of ion channels where transduction of salty and sour tastants is initiated

Question 24

GPCRs involved in taste perception

Answer 24

Characterized biochemically and genetically

• Linked via behavioral and genetic studies in mice to the transduction of sweet, umami, and bitter tastants
  - T1R2-T1R3: sweet tastants
  - T1R1-T1R3: umami tastants
  - T2Rs bitter tastants
• Acids Sour tastant
• ENaC Salty (everyday and other salts categories)
  - KO: transduction of Na+ ions in relatively low concentrations

Question 25

Cell-to-Cell signaling

Answer 25

In taste perception, signals from receptor cells to presynaptic cells cause the presynaptic cells to release neurotransmitters in a way that carries information about sweet, umami, and bitter tastants * ion channels in presynaptic cells transduce salty and sour tastants

Question 26

Taste perception models

Answer 26

Labeled-line pattern | Across- fiber pattern

Question 27

Labeled-Line Pattern

Answer 27

Suggests cranial nerve fibers are responsible for information about only one taste - cortical neurons on receiving end of these signals also response only to information about signal type of tastants

Question 28

Across-fiber pattern

Answer 28

Suggests cranial nerve fibers are responsible for information from several tastes; evidence supports the across-fiber pattern model - cortical neurons receiving these signals are broadly tuned to respond to signals carrying information about multiple types of tastants

Question 29

Receptor Cells and Presynaptic cells

Answer 29

Receptor cells: cilium of sweet, umami, and bitter receptor cells contain receptors Presynaptic cell: cilium of cells with salty and sour ion channels

Question 30

Across- fiber pattern model: […] carry signals to the brain

Answer 30

Across- fiber pattern model: cranial nerves carry signals to the brain - VII (facial; front two-thirds of tongue and soft palate) - IX (glossopharyngeal; back third of tongue) - X (vagus; epiglottis, and upper esophagus)

Question 31

Cranial nerve send signals to:

Answer 31

Nucleus of solitary tract (gustatory nucleus) —> Ventral posterior medial nucleus of thalamus —> primary taste cortex (representation of taste quality)

Question 32

Primary taste cortex

Answer 32

First cortical areas to receive taste signals (representation of taste quality) - anterior insular cortex - frontal operculum Goes to amygdala (representation of emotion), orbitofrontal cortex (representation of reward value of food), hypothalamus (representation of hunger)

Question 33

Taste Quality versus Reward Value

Answer 33

Taste quality- constant firing rate in primary taste cortex Reward Value- decreasing firing rate in OFC

Question 34

Adaptation

Answer 34

Tastants from one basic taste doesn’t reduce sensitivity to other basic tastes

Question 35

Cross- Adaptation

Answer 35

Cross- adaptation between similar tastants can occur

Question 36

Expectations and Flavor Perception

Answer 36

Increases price= increased pleasure - difference seen in orbitofrontal cortex

Question 37

Cognitive Influences in the OFC, and the Flavor of Expensive Wine

Answer 37

Expectations about a food or drink can influence activity in parts of the brain involved in signaling flavor- expectations can truly change the flavor that you perceive

Question 38

Satiety

Answer 38

Reduction in appetite for food

Question 39

Sensory- Specific Satiety

Answer 39

Reduction in appetite specifically for foods that have been recently consumed - aids in avoidance of nutritional deficiencies associated with a limited diet - may be influence by memory and previously consumed food

Question 40

Regulated food intake without taste information

Answer 40

KO mice still preferred sucrose water over sucralose water because of the nutritious values of sugar water

Question 41

Individual Differences in Taste and Flavor Perception

Answer 41

Ability or inability to taste certain bitter substances (most common) - two gene version: PAV (75%) and AVI (25%) Ability to taste bitter and other substances more intensely - Taster - Nontaster - Supertaster

Question 42

Taster

Answer 42

People with form of gene that allows them to detect certain bitter tastants

Question 43

Nontasters

Answer 43

People with form of gene that allows them to detect certain bitter tastants only at very high concentrations

Question 44

Supertasters

Answer 44

Tasters who have about 2x as many fungiform papillae as others and are especially sensitive to certain bitter tastants - 1/3 of tasters are supertasters

Question 45

Individual Difference in Taste and Flavor Perception

Answer 45

Many factors may lead to individual difference in taste preferences - Chocolate - Capsaicinoids: increased capsaicin conc= increased perceived spiciness

Question 46

The taste and use of artificial sweeteners

Answer 46

Artificial sweeteners create the perception of sweetness in the absence of sucrose by binding to the T1R3 GPCR, just like sucrose does

Question 47

Brain responses to artificial sweeteners: Behavioral responses research

Answer 47

- measurable effect on overt behavior associated with difference between natural and artificial sweeteners - perceptual system assessment takes the body’s current capabilities into account (ex. Assessing features of the spatial environment)

Question 48

Brain activity in response to sweeteners

Answer 48

Activity in response to sucrose: anterior insular cortex, frontal operculum, and orbitofrontal cortex= increase activation *same activation doesn’t occur in sucralose

Question 49

Behavioral Responses to Artificial Sweeteners

Answer 49

Weight Loss - artificial sweeteners might not effectively facilitate weight loss - artificial sweeteners can have complex behavioral effects - more research is needed