Chapter 15 Study Questions

What is a nontaster?

Answer: A nontaster is an individual born without receptors for the bitter compound PROP. Nontasters also tend to have the fewest fungiform papillae.

What is a supertaster?

Answer: A supertaster is an individual whose taste sensations are extremely intense and who also has a high density of fungiform papillae.

What causes something to taste sour?

Answer: Acidic solutions—those having a relatively higher proportion of hydrogen ions—taste sour to us.

Provide an example supporting the specific hungers theory.

Answer: An example supporting the specific hungers theory comes from a treatment for schizophrenia in the 1940s, wherein the brain would be deprived of glucose in order to bring it to a restful stage using insulin. This treatment in turn, created intense cravings for sweet, and later laboratory studies confirmed that insulin injections produce increased liking for sweet.

What is cross-modality matching?

Answer: Cross-modality matching is the ability to match the intensities of sensations that come from different sensory modalities. For instance, adjusting a light until it is as bright as a lemon tastes sour would be a cross-modality matching task.

In way do supertasters and normal tasters perform cross-modality matching differently?

Answer: Cross-modality matching is the ability to match the intensities of sensations that come from different sensory modalities. Normal tasters, who do not perceive bitter substances to be very extreme, usually match those substances to mild sensations in other modalities, such as a mild noise, or pain. However, supertasters who perceive bitter substances to be very intense usually match those substances to more severe sensations in other modalities, such as greater noise, or a more moderate pain level.

In way can diet affect the perception of saltiness?

Answer: Diet can affect the perception of saltiness by adjusting how much salt is consumed. For instance, people on low-sodium diets perceive salt to be more intense than others.

Provide an example showing how liking spicy foods can be influenced by social factors.

Answer: Liking spicy foods, such as chili peppers, can be influenced by social factors. For example, in Mexico, chili is gradually added to the diet of young children beginning at age 3, and the children observe their family eating it. By age 5 or so, children voluntarily add chili to their own food.

Provide one example of cross-adaptation in taste perception.

Answer: One such example is eating something sweet, such as candy and then immediately after consuming a sour beverage such as lemonade. The lemonade tastes a lot more sour than it normally does after consuming the sweet candy. This is due to the sugar in the candy causing the sweet receptors to adapt, so that the subsequent lemonade tastes less sweet and more sour than normal.

Describe the papillae and name the four kinds.

Answer: Papillae are the structures that give the tongue its bumpy appearance. They vary in size and shape, and contain the taste buds. The four types of papillae are: filiform papillae, fungiform papillae, foliate papillae, and circumvallate papillae.

What is retronasal olfactory sensation?

Answer: Retronasal olfaction is the sensation of an odor that is perceived when chewing and swallowing force an odorant from the mouth up behind the palate and into the nasal cavity. Such odor sensations are perceived as originating from the mouth, even though the actual contact between odorant and receptor occurs in the olfactory mucosa.

How is sensitivity for bitter flavors different for women than for men?

Answer: Sensitivity for bitter flavors is affected by hormone levels in women; this is not the case for men.

What are taste buds?

Answer: Taste buds are globular clusters of cells that create the neural signals conveyed to the brain by taste nerves. Some of the cells in the taste bud have specialized sites on their apical projections that interact with taste stimuli. Some of the cells form synapses with taste nerve fibers.

What is the function of the taste receptor cells?

Answer: Taste receptor cells within the taste bud contain sites on their apical projections that interact with taste stimuli. These sites fall into two major categories: those interacting with charged particles, and those interacting with specific structures.

What is the fifth basic taste candidate? Describe it.

Answer: The fifth basic taste candidate is umami. This is a taste sensation evoked by monosodium glutamate.

What are the four basic tastes?

Answer: The four basic tastes are: salty, sour, bitter, and sweet.

What is the functional difference between the insular cortex and the orbitofrontal cortex?

Answer: The insular cortex is the primary cortical processing area for taste. It receives taste information first. The orbitofrontal cortex, on the other hand, receives projections from the insular cortex. Some orbitofrontal cortex neurons are multimodal, responding to temperature, touch, smell and taste, suggesting that it is an integration area.

Describe the labeled lines theory.

Answer: The labeled lines theory states that each nerve fiber carries a particular taste quality. For example, the quality evoked from a sucrose-best fiber is sweet, that from NaCl-best fiber is salty, and so on.

How do the microvilli help in the process of taste perception

Answer: The microvilli are slender projections on the tips of some taste bud cells that extend into the taste pore. They contain sites that bind taste substances and help in the process of taste perception.

In way has the sense of taste helped humans survive over the years?

Answer: The sense of taste has helped humans detect nutrients and "antinutrients" (substances that are harmful) in the environment before ingesting them. Usually harmful substances have bitter or acidic flavors to them, and in this way the sense of taste has helped humans stay away from them.

What does the specific hungers theory contend?

Answer: The specific hungers theory contends that a deficiency of a given nutrient will produce a craving for that nutrient. Evidence supports specific hungers theory for sweet and salty foods but not for other nutrients.

In way were the early Greeks wrong in their belief that sensations perceived from foods in the mouth are "tastes," whereas sensations perceived through the nose are "smells"?

Answer: This is a misunderstanding because food molecules are almost always perceived by both our gustatory and our olfactory systems. The molecules are dissolved in our saliva and passed over to taste receptors in our taste buds. Then, as we chew and swallow foods, other molecules are released into the air inside our mouths and travel into the nasal cavity, stimulating the olfactory receptors.

What happens when the chorda tympani is anesthetized?

Answer: When the chorda tympani is anesthetized, one cannot taste anything. This cranial nerve normally carries information from taste receptors to the brain.