ch 13. the chemical senses

Schiffman's multidimensional scaling model: (Classification of odors)

- using likert-like similarly measures from subjects (looking for similarities of odors) -schiffman calcuated a multi-dimensional odor space -she found that the merely 2D were adequately to describe this space *SAYING ALL ODORS FIT WITHIN A 2D SPACE PROBLEMS: -while 1 dimension correspond well with ideas of pleasantness there's no psychologically relevant term to describe 2nd dimension (ex. what makes odors smell similar)

classification of odors:

-17/18th century: practical concerns with classifying odors because "bad" odors are associated with disease

what secretes saliva

-3 major salivary glands as well as other small glands in the tongue in mouth

neural rep. of odor intensity:

-appears to be based on firing frequency of receptor cells (more firing = increased concentration / more intense odor) - odor QUALITY changes with intensity -- not independent dimensions *too much of any smell is not good*

taste receptor cells

-arranged like segments of an orange, the tips of taste receptor cells reach out into the opening and can touch any taste molecule int he saliva that flow into the pit -@ the tip of the taste receptor cells there are MICROVILLI (which fill the opening of the taste bud--the taste pore)

basic categories for taste from ancient greeks:

-artistotle proposed: sweet, bitter, salty, sour, astringent, pungent, harsh

tastant

-basic stimulus for taste -chemical compound dissolved in a solution like saliva

identification [odor perception]

-can be improved with practice -females are almost always better than males (unknown why) -mothers can detect their own newborns by smell alone after spending only 1 hour together -good detection, but bad identification seems due to a weak link between odor and its verbal label

location of taste receptors in the mouth:

-clue to their purpose -tells us about qualities from substances we put in our mouth

Hans Hennings smell (hollow) prism: (classification of odors)

-conceptual organization of principle smells (only the surface) -corners meant items could be described with one item, planes/ edges meant more than 1 descriptor with necessary PROBLEMS: -can't classify all smells using only 6 descriptions

adaption to odors

-continued exposure to an odor results in a gradual decrease in perceived intensity of that odor to about 30% of its initially perceived intensity -recovery from adaption (depending on intensity of initial exposure) may take as long as 1 hr -adaption is due to brain mechanisms NOT fatigue of olfactory receptors -blocking 1 nostril & adapting to an odor with the open nostril results in both nostrils

detection & identification for taste:

-higher (warmer) temps. make bitter substances taste less bitter and sweet substances taste more sweet -heating masks bitterness & cooling masks sweetness

olfactory epithelium

-kind of skin you smell with -12 million receptors -each receptor has tiny cilia protruding from it which protect mucus lining in nasal cavity, cilia also catches odorant

anosmia [odor blindness]

-may be caused by a blow to the head -otherwise temporary; olfactory cells reproduce & replace old ones in a few weeks time -odor hallucinations may signal a brain tumor (or mental illness)

olfactory build (olfactory pathway)

-receives all of the input from the olfactory nerve -structurally similar to the retina (several layers of cells laterally interconnected) --> NO topographic spatial map -it appears that specific odorants produce characteristic patterns of neural activity in olfactory bulb -perhaps these patterns are what we use to discriminate odors

absolute threshold [taste perception]

-tells us whether or not a person can detect the presence of a substance--even if he or she can't identify the taste

olfactory receptor cells

-these cells transduce chemical signals into neural events and carry the impulses directly to the brain

neural coding of odor quality

-with the visual and auditory senses, different cells respond \fire maximally to a specific range of stimuli -with the olfactory senses, receptor cells DO NOT respond with the same type of discrimination -instead, most olfactory receptor cells respond to a BUNCH of different odors even if they are not similar to one another -hence, there's no evidence of the specialization observed for the visual & auditory systems

stimuli for smell: Smell from an "object" requires objects to be:

1. volatile (give give off vapors--invisible molecules of gas) & 2. soluble in fat (vapor molecules must be absorbable by substances containing fat)

During normal breathing, _______ of the odorous molecules entering the nostrils actually make it to receptors.

2%

The percentage of accuracy for distinguishing sex based on the odor of hands, as determined by Patricia Wallace (1977), is:

80

about ___% of taste buds are located on __% of the tongues surface

90, 1

what stimulates unami taste?

MSG

does taste sensitivity get better with hungry?

NO! Also, doesnt get worse for smokers --Taste-dulling is due to a decrease in olfaction

_____ are about 70% of the population:

TASTERS make up 70% of the population that has inherited the ability to taste phenyltheiocarbamide (PTC) which to taters is very bitter

how often are taste buds replaced?

about 10 days [lifespan]

cross-adaption

adaption to one substance raises the threshold for another substance -ex: if you've been drinking tea w/ lemon, the vinegar salad dressing does not taste as sour

effects of age, time of day, & gender on detection of odor

age: younger= better time of day: better in the morning gender: females are more sensitive than males

Neural activity in the olfactory bulb of an animal is enhanced if that animal is: A) hungry B) thirsty C) fearful

all of these

the nasal cycle is:

alternating resistance to the inflow of air in each nostril

every taste bud is made up of:

basal and supporting cells that help maintain about 50 gustatory receptor cells -these receptors are stimulated by the chemical makeup of solutions -they respond to several tastes (sweet, salty, bitter, sour, unami, + fat)

taste bud

basic receptor for taste stimuli -visible only with a microscope -located throughout tongue and throat

tastant (taste stimulus)

basic stimulus for taste; a chemical compound dissolved in a solution such as saliva -many taste stimuli give rise to a limited # of qualities

Most people have the greatest sensitivity to which basic taste?

bitter

The concentration yielding the highest hedonic rating is referred to as:

bliss point

olfactory neurons :

capable to reproducing -live about 5-8 weeks and are then replaced (axons and all) by new cells

The ____________ of the tongue contain(s) no taste receptors.

center

During normal eating, the taste of food changes over time in the mouth because:

chewing releases chemical substances from the food

olfactory neurons are the only neurons that:

come into contact with the outside world

recognition threshold [taste perception]

concentration of a solution that can be identified by quality. specifies the amount of a substance that must be added to water for tasters to recognize the taste as sweet/ salty/ etc.

fungiform papillae

contain 1 or a few taste buds (front of the mouth)

foliate papillae

contain hundreds of taste buds (side of mouth)

circumvillate papillae

contain thousands of taste buds (mostly in back of mouth)

the tongue (taste receptor)

covered with mucous membrane, contains bumpy structures that cover the surface, which are papillae (NOT taste buds)

The notion that taste perception is a function of the pattern of activity across a population of taste fibers was first postulated by Carl Pfaffmann (1955). His theory is called:

cross-fiber theory

Which of the following statements is true of olfactory receptor cells? A) Dogs have more of them than humans. B) They live only about five to eight weeks. C) They can grow new axons to reach their target site in the brain. D) All of these are true.

d) all of these are true A) Dogs have more of them than humans. B) They live only about five to eight weeks. C) They can grow new axons to reach their target site in the brain.

adaption

decrease in sensitivity following continuous presentation of a stimulus (occurs for taste)

saliva solution contains:

digestive enzymes that help break down foods chemically

Butter sitting in the refrigerator will take on the smell of:

fat-soluble volatile molecules

The sense of taste is also known as:

gustation

gustatory receptor cells

have long, spindlelike protrusions (gustatory hairs) that comes in contact with the outside world *hairs extend from a small opening (taste\pore) & mingles with molecules of food introduced by saliva

flavor

includes both taste and smell, as well as tactile experiences.

hedonics

involve judgment sof pleasant & unpleasantness which are central in our perceptual responses to food flavors -

Which is a minimum prerequisite for a substance to be tasted?

it must be soluble

Cigarette smokers, compared to nonsmokers, are:

less sensitive to odors

olfactory receptor cells are actual

neurons

olfacotry bulb:

neurons --> brain

what is mouth feel?

not only can the tongue detect gustatory stimuli, but it also perceives temperature & the complex tactile sensations

Sewer workers are able to carry out their work without being bothered too much by the stench. This is a result of:

odor adaption

The sense of smell is also known as:

olfaction

taste information goes to a region called the

orbitofrontal cortex (part of frontal cortex above eyes) -plays role in making food pleasant/ rewarding

detection [odor perception]

our sense of smell may be relatively dull compared to other animals; however, it's equal or more sensitive than current technology ~there's a BIG difference between being able to detect a smell & being able to identify the smell

bumpy structures covering the surface of the tongue are:

papillae which are goblet shaped elevations that sometimes contain taste buds and help create friction between the tongue and food

The ____________ are the bumps on the tongue that contain the ___________ that house the receptor cells responsible for taste.

papillae; taste buds

ageusia

person has lost the ability to taste a substance

Animal odors that appear to be important in mate identification and selection are called:

pheromones

anatomy and physiology of smell: OLFACTORY EPITHELIUM

reception cells for smell (40-50 mil) are located on patches of tissue -diameter of a very thin dime; forming part of the ceiling of EACH nasal cavity

when a stimulus activates gustatory cells:

receptor synapses with neurons and sends electrical impulses to the gustatory region of the cerebral cortex producing our perception of taste

taste (gustation)

refers only to the perceptions that result from the contact of substances with receptors in the mouth -- primarily the tongue.

nontasters:

remaining 30% of population, to these people the PTC is as benign as water

G-proteins

responsible for our perception of sweet, bitter, & unami

tasters have more :

rounded buds on their tongues which hold taste buds -also tend to like certain foods more than non tasters like coffee, veggies, grapefruit

5 basic tastes:

salty sweet sour unami bitter

when the same tasting leads to a loss of sensitivity to itself, this process is called

self-adaption -reaches max around 1 min

olfaction

sense of smell ("minor sense")

papillae

small projections (little bumps) -most common type of papillae does not contain taste buds, but some do

taste buds:

structures tucked in the folds between the papillae -we have ~10,000 taste buds in our mouth

The five basic taste qualities are:

sweet, salty, sour, bitter, & unami

cross adaption

temporary loss in sensitivity to 1 odor produced by exposure to a different odor (ex. polish remover, airplane glue)

Which of the following is not a principal quality of Henning's smell prism?

tepid

The coolness of menthol is detected by:

the common chemical sense

The reason given in the text why the color of food might influence its smell is:

the difficulty in locating the source of an odor.

hans hennig is credited with promoting:

the idea of 4 basic tastes: sweet, bitter, salty, & sour

axons of the olfactory neurons

the olfactory nerve

The intensity of a taste is signaled by:

the rate of firing within nerve fibers

The ability to sort cherry pits from cherry flesh in one's mouth is evidence of:

tongue haptics

cross-fiber theory of taste equality (pfaffmann)

uniqueness (taste quality) of tastes is calculated by the pattern of sensations across a population of receptors (taste fibers) ~like freq. theory of hearing~