Topic 16: The Chemical Senses

Question 1

Taste

Answer 1

the chemical sense that occurs when molecules – often associated with food – enter the mouth in solid or liquid form and stimulate receptors on the tongue

Question 2

Olfaction

Answer 2

the sense of smell

usually results from stimulation of receptors in the olfactory muscosa

Question 3

Flavor

Answer 3

the perception that occurs from the combination of taste and olfaction

Question 4

Neurogenesis

Answer 4

the cycle of birth, development, and death of a neuron

this process occurs for the receptors for olfaction and taste

Question 5

Papillae

Answer 5

ridges and valleys on the tongue, some of which contain taste buds

there are four types of papillae: filiform, fungiform, foliate, and circumvallate

Question 6

Taste Buds

Answer 6

a structure located within papillae on the tongue that contains the taste cells

Question 7

Taste Cells

Answer 7

cell located in taste buds that causes the transduction of chemical to electrical energy when chemical contact receptor sites or channels located at the tip of this cell

Question 8

Taste Pore

Answer 8

an opening in the taste bud through which the tips of taste cells protrude

when chemicals enter a taste pore, they stimulate the taste cells and result in transduction

Question 9

Nucleus of the Solitary Tract

Answer 9

the nucleus in the brain stem that receives signals from the tongue, the mouth, and the larynx transmitted by the chorda tympani, glossopharyngeal, and vagus nerves

Question 10

Insula

Answer 10

an area in the frontal lobe of the cortex that receives signals from the taste system and is also involved in the affective component of the perception of pain

Question 11

Frontal Operculum

Answer 11

an area in the frontal lobe of the cortex that receives signals from the taste system

Question 12

Across-Fiber Pattern

Answer 12

the pattern of nerve firing that a stimulus causes across a number of neurons

also referred to as distributed coding

Question 13

Amiloride

Answer 13

a substance that blocks the flow of sodium into taste receptors

Question 14

Microsmatic

Answer 14

having a weak sense if smell

this usually occurs in animals, such as humans, in which the sense of smell is not crucial for survival

Question 15

Macrosmatic

Answer 15

having a keen sense of smell

usually important to an animal’s survival

Question 16

Detection Threshold

Answer 16

for olfaction the detection threshold is the lowest concentration at which an odorant can be detected

Question 17

Forced-Choice Method

Answer 17

method in which two choices are given, and the subject has to pick one

for example, a subject is presented with a weak odorant on one trial, and no odorant on another trial, and has to pick the trial on which the odorant was present

Question 18

Sustentacular Cells

Answer 18

cells that provide metabolic and structural support to the olfactory sensory neurons

Question 19

Alzheimer’s Disease

Answer 19

serious loss of memory and other cognitive functions that is often preceded by mild cognitive impairment (MCI)

Question 20

Mild Cognitive Impairment

Answer 20

cognitive impairments that extend beyond those associated with normal aging, but which often do not interfere with activities of daily living

often is a precursor to more serious conditions such as Alzheimer’s disease

Question 21

Odor Objects

Answer 21

the source of an odor, such as coffee, bacon, a rose, or car exhaust

Question 22

Olfactory Mucosa

Answer 22

the region inside the nose that contains the receptors for the sense of smell

Question 23

Olfactory Bulb

Answer 23

the structure that receives signals directly from the olfactory receptors

the olfactory bulb contain glomeruli, which receive these signals from the receptors

Question 24

Olfactory Receptor Neurons (ORNs)

Answer 24

sensory neurons located in the olfactory mucosa that contain the olfactory receptors

Question 25

Olfactory Receptors

Answer 25

a protein strong that responds to odor stimuli

Question 26

Calcium Imaging

Answer 26

a method of measuring receptor activity by using fluorescence to measure the concentration of calcium inside the receptor

this technique has been used to measure the activation of olfactory receptor neurons

Question 27

Recognition Profile

Answer 27

the pattern of olfactory activation for an odorant, indicating which ORNs are activated by the odorant

Question 28

Glomeruli

Answer 28

small structures in the olfactory bulb that receive signals from similar olfactory receptor neurons

one function of each glomerulus is to collect information about a small group of odorants

Question 29

Chemotropic Maps

Answer 29

the pattern of activation in the olfactory system in which chemicals with different properties create a “map” of activation based on these properties

for example, there is evidence that chemicals are mapped in the olfactory bulb based on carbon-chain length

also called odor map

Question 30

Piriform Cortex (PC)

Answer 30

an area under the temporal lobe that receives signals from glomeruli in the olfactory bulb

also called the primary olfactory area

Question 31

Orbitofrontal Cortex

Answer 31

an area in the frontal lobe, near the eyes, that receives signals originating in the olfactory bulb

also called the primary olfactory area

Question 32

Orbitofrontal Cortex

Answer 32

an area in the frontal lobe, near the eyes, that receives signals originating in the olfactory receptors

also known as the secondary olfactory cortex

Question 33

Amygdala

Answer 33

a subcortical structure that is involved in emotional responding and in processing olfactory signals

Question 34

Proust Effect

Answer 34

the elicitation of memories through taste and olfaction

named for Marcel Proust, who described how the taste and smell of a tea-soaked madeleine cake unlocked childhood memories

Question 35

Odor-Evoked Autobiographical Memories

Answer 35

memories about events from a person’s life that are elicited by odors

Question 36

Retro-nasal Route

Answer 36

the opening from the oral cavity, through the nasal pharynx, into the nasal cavity

this route is the basis for the way smell combines with taste to create flavor

Question 37

Nasal Pharynx

Answer 37

a passageway that connects the mouth cavity and the nasal cavity

Question 38

Oral Capture

Answer 38

the condition in which sensations from both olfaction and taste are perceived as being located in the mouth

Question 39

Bimodal Neurons

Answer 39

a neuron that responds to stimuli associated with more than one sense

Question 40

Sensory-Specific Satiety

Answer 40

the effect on perception of the odor associated with food eaten to satiety (the state of being satiated or “full”)

for example, after eating bananas until satiety, the pleasantness rating for vanilla decreased slightly (but was still positive), but rating for banana odor decreased much more and became negative

Question 41

What is gustation?

Answer 41

flavor is a combination of smell and taste, but may also include texture and other sensory aspects

difficult to identify food without olfaction

not a “far” sense; gustation is the most intimate sense

adapted to test whether food with edible, spoiled, or poisionous

Question 42

What is the taste stimuli: salty?

Answer 42

in-/organic salts

cation is most important (e.g., Na+ in NaCl)

Question 43

What is the taste stimuli: sour?

Answer 43

in/organic acids that release H+ ions in solution

not all acids are sour

Question 44

What is the taste stimuli: sweet?

Answer 44

complex organic molecules: sugar, aspartame

Question 45

What is the taste stimuli: bitter?

Answer 45

varied: alkaloids; some nitrogen-containing molecules; some related to but having different molecular arrangement than sweet molecules

Question 46

What is the taste stimuli: umami?

Answer 46

brothy, meaty, or savory

salts of glutamic acid

found in protein-rich foods, Parmesan cheese, tomatoes, mushrooms, and Marmite yeast extract

glutamic acid + Na+ –> monosodium glutamate (MSG)

Question 47

What are the receptors of gustation?

Answer 47

tongue is covered with 4 kinds of bumps called papillae

we have up to 10,000 buds

each bud has several taste cells (receptors)

microvilli of receptor cells project out of taste pore

taste buds wear out and are replaced every 7-10 days; less frequently replaced after age 45

Question 48

Where are taste buds found on?

Answer 48

fungiform: mushroom-shaped; on tip and sides

foliate: folds along sides of tongue

circumvallate: flat mounds surrounded by a trench; on back of tongue

also found on soft palate

Question 49

What is transduction in gustation?

Answer 49

sodium penetrates membrane of receptor, depolarizing it

sour substances contain H+ which blocks ion channels

other substances may form bonds with molecules in the membrane, causing chemical changes within the cell

Question 50

What is labeled-line (specificity coding)?

Answer 50

different taste stimuli activate specific fibers; firing rate represents intensity

each nerve fiber is “labeled” as corresponding to a particular taste sensation

activity in a few fiber types is all that’s needed to code stimuli

however, many substances elicit more than one taste (e.g. sodium saccharine shifts from sweet to bitter with increased concentration)

Question 51

What is across-fiber pattern (population coding)?

Answer 51

there are no specialized receptors for each taste; taste quality signaled by pattern of activity across many fibers

each fibers type responds to a variety of substances, but seems to be tuned to respond best to one type of taste