Chapter 15

Question 1

taste

Answer 1

Sensations evoked by solutions in the mouth that contact receptors on the tongue and the roof of the mouth that then connect to axons in cranial nerves VII, IX, and X.

Question 2

retronasal olfactory sensation

Answer 2

The sensation of an odor that is perceived when chewing and swallowing force an odorant in the mouth up behind the palate into the nose. Such odor sensations are perceived as originating from the mouth, even though the actual contact of odorant and receptor occurs at the olfactory mucosa.

Question 3

flavor

Answer 3

The combination of true taste (sweet, salty, sour, bitter) and retronasal olfaction.

Question 4

chorda tympani

Answer 4

The branch of cranial nerve VII (the facial nerve) that carries taste information from the ante- rior, mobile tongue (the part that can be stuck out). The chorda tympani exits the tongue with the lingual branch of the trigeminal nerve (cranial nerve V) and then passes through the middle ear on its way to the brain.

Question 5

cranial nerves

Answer 5

Twelve pairs of nerves (one for each side of the body) that originate in the brain stem and reach sense organs and muscles through openings in the skull.

Question 6

taste bud

Answer 6

A globular cluster of cells that has the function of creating neural signals conveyed to the brain by the taste nerves. Some of the cells in a taste bud have specialized sites on their apical projections that interact with taste stimuli. Some of the cells form synapses with taste nerve fibers.

Question 7

papilla

Answer 7

Any of multiple structures that give the tongue its bumpy appearance. From smallest to largest, the papilla types that contain taste buds are fungiform, foliate, and circumvallate; filiform papillae, which do not contain taste buds, are the smallest and most numerous.

Question 8

taste receptor cell

Answer 8

A cell within
the taste bud that contains sites on its apical projection that can interact with taste stimuli. These sites fall into two major categories: those interacting with charged particles (e.g., sodium and hydrogen ions) and those interacting with specific chemical structures.

Question 9

filiform papillae

Answer 9

Small structures on the tongue that provide most of the bumpy appearance. Filiform papillae have no taste function.

Question 10

fungiform papillae

Answer 10

Mushroom-shaped structures (maximum diameter 1 milli- meter) that are distributed most densely on the edges of the tongue, especially the tip. Taste buds (an average of six per papilla) are buried in the surface.

Question 11

supertaster

Answer 11

An individual whose perception of taste sensations is the
most intense. A variety of factors may contribute to this heightened percep- tion; among the most important is the density of fungiform papillae.

Question 12

foliate papillae

Answer 12

Folds of tissue containing taste buds. Foliate papillae are located on the rear of the tongue lateral to the circumvallate papillae, where the tongue attaches to the mouth.

Question 13

circumvallate papillae

Answer 13

Circular structures that form an inverted V on the rear of the tongue (three to five on each side, with the largest in the cen- ter). Circumvallate papillae are mound- like structures, each surrounded by a trench (like a moat). These papillae are much larger than fungiform papillae.

Question 14

microvilli

Answer 14

Slender projections of the cell membrane on the tips of some taste bud cells that extend into the taste pore.

Question 15

insular cortex

Answer 15

The primary cortical processing area for taste—the part of

the cortex that first receives taste infor- mation. Also called the insula or the gustatory cortex.

Question 16

orbitofrontal cortex (OFC)

Answer 16

The part of the frontal lobe of the cor-
tex that lies behind the bone (orbit) containing the eyes. It is involved in many functions and is responsible for the conscious experience of olfaction, as well as the integration of pleasure and displeasure from food, and has been referred to as the secondary olfactory cortex and secondary taste
cortex. It is also critical for assigning affective value to stimuli—in other
words, determining hedonic meaning.

Question 17

basic taste

Answer 17

Any of the four taste qualities that are generally agreed to describe human taste experience: sweet, salty, sour, bitter.

Question 18

salty

Answer 18

One of the four basic tastes; the taste quality produced by the cations of salts (e.g., the sodium in sodium chloride produces the salty taste). Some cations also produce other taste qualities (e.g., potassium tastes bitter as well as salty). The purest salty taste is produced by sodium chloride (NaCl), common table salt.

Question 19

sour

Answer 19

One of the four basic tastes; the taste quality produced by the hydrogen ion in acids.

Question 20

bitter

Answer 20

One of the four basic tastes; the taste quality, generally considered unpleasant, produced by substances like quinine or caffeine.

Question 21

sweet

Answer 21

One of the four basic tastes; the taste quality produced by some sugars, such as glucose, fructose, and sucrose. These three sugars are particularly biologically useful to us, and our sweet receptors are tuned to them. Some other compounds (e.g., saccharin, cyclamate, aspartame) are also sweet.

Question 22

heterodimer

Answer 22

A chain of two molecules that are different from each other.

Question 23

umami

Answer 23

The taste sensation produced by monosodium glutamate.

Question 24

monosodium glutamate (MSG)

Answer 24

The sodium salt of glutamic acid (an amino acid).

Question 25

nontaster (of PTC/PROP)

Answer 25

An individual born with two recessive alleles for the TAS2R38 gene and unable to
taste the compounds phenylthiocar- bamide (PTC) and propylthiouracil (PROP).

Question 26

taster (of PTC/PROP)

Answer 26

An individual born with one or two dominant alleles for the TAS2R38 gene and able to taste the compounds phenylthiocarbamide (PTC) and propylthiouracil (PROP). PTC/PROP tasters who also have a high density of fungiform papillae are PROP supertasters.

Question 27

cross-modality matching

Answer 27

The ability to match the intensities of sensations that come from different sensory modalities. This ability allows insight into sensory differences. For example, a listener might adjust the brightness of a light until it matches the loudness of a tone.

Question 28

specific hungers theory

Answer 28

The idea that deficiency of a given nutrient produces craving (a specific hunger) for that nutrient. Curt Richter first pro- posed this theory and demonstrated that cravings for salty or for sweet
are associated with deficiencies in those substances. However, the idea proved wrong for other nutrients (e.g., vitamins).

Question 29

labeled lines

Answer 29

A theory of taste cod- ing in which each taste nerve fiber carries a particular taste quality. Thus a fiber that responds best to sucrose but also responds with small responses to other stimuli carries only sweet.