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Sensation > taste > Flashcards

taste Flashcards

1
Q

Retronasal olfactory sensation

A

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
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2
Q

Flavor

A

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

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3
Q

Patient case

A

Damaged taste, but normal olfaction —could smell lasagna, but had no flavor

Similar effect created in lab: Chorda tympani anesthetized with lidocaine

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4
Q

Chorda tympani

A

The branch of cranial nerve VII (the facial nerve) that carries taste information from the anterior, mobile tongue (the part you can stick out)

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5
Q

Brain imaging studies

A

Brain processes odors differently, depending on whether they come from nose or mouth

Food industry: Adds sugar to intensify sensation of fruit juice § Increase in sweetness (a pure taste sensation) increases perceived olfactory sensation of fruit

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6
Q

Taste buds

A
  • Create neural signals conveyed to brain by taste
    nerves
  • Embedded in structures: Papillae (bumps on
    tongue)
  • Each taste bud contains taste receptor cells
  • Information is sent to brain via cranial nerves
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7
Q

Four kinds of papillae

A
    1. Filiform papillae: Small structures on the tongue
      that = the bumpy appearance. Have
      no taste function
    1. Fungiform papillae: Mushroom-shaped
      structures (maximum diameter 1 mm) that are
      distributed most densely on the edges of the
      tongue, especially the tip. An average of six taste
      buds per papilla are buried in the surface
    1. Foliate papillae: Folds of tissue containing taste
      buds. Located on the rear of the tongue lateral to
      the circumvallate papillae, where the tongue
      attaches to the mouth
    1. Circumvallate papillae: Circular structures that
      form an inverted V on the rear of the tongue (three
      to five on each side). Moundlike structures
      surrounded by a trench. Much larger than
      fungiform papillae
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8
Q

Microvilli

A

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

Contain the sites that bind to taste substances

Not tiny hairs (as the name implies): We now
know they are extensions of the cell membrane

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9
Q

Tastant

A

Any stimulus that can be tasted
Tastants can be divided into two large categories:

Some are made up of small, charged particles that
taste salty or sour

Small ion channels in microvilli membranes
allow some types of charged particles to enter
but not others

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10
Q

Pathway

A

Taste buds to cranial nerves to medulla
and thalamus and then on to cortex

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11
Q

Insular cortex

A

Primary cortical processing area for
taste. The part of the cortex that first receives taste
information

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12
Q

Orbitofrontal cortex

A

The part of the frontal lobe of
the cortex that lies above the bone (orbit)
containing the eyes

Receives projections from insular cortex

Involved in processing of temperature, touch,
smell, and taste, suggesting it may be an
integration area

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13
Q

Inhibition

A

Plays an important role in processing taste
information in the brain.

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14
Q

Function

A

To protect our whole mouth perception of
taste when we have injuries to taste system.
Descending inhibition from taste cortex blocks pain
perception
* Has survival value because we need to eat even if
our mouth has been injured

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15
Q

Four basic tastes

A
  • Salty
  • Sour
  • Bitter
  • Sweet
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16
Q

Salty:

A
  • Salt is made up of two charged particles: Cation
    and anion.
  • Ability to perceive salt is not static
    § Low-sodium diets will increase in intensity of
    salty foods over time
  • Liking for saltiness is not static
    § Early experiences can modify salt preference.
    Chloride-deficiency in childhood leads to
    increased preference for salty foods later
    § Gestational experiences may affect liking for
    Saltiness
17
Q

Sour:

A
  • Comes from acidic substances
  • At high concentrations, acids will damage both
    external and internal body tissues
18
Q

Bitter:

A
  • Quinine: Prototypically bitter-tasting substance
  • Cannot distinguish between tastes of different
    bitter compounds
  • Many bitter substances are poisonous
19
Q

Sweet:

A
  • Evoked by sugars
  • Many different sugars that taste sweet:
    § Glucose: Principle source of energy for most
    animals
    § Fructose: Even sweeter than glucose
    § Sucrose: Common table sugar. Combination of
    glucose and fructose
20
Q

The special case of umami:

A
  • Candidate for fifth basic taste
  • Comes from monosodium glutamate (MSG)
  • Glutamate: Important neurotransmitter
21
Q

Survival value of taste

A

Taste is a system for detecting nutrients and
antinutrients

Bitter: Might signal poisons

Sour: Configured to detect acidic solutions that
might harm the body

Sweet and Salty: Our bodies need sodium and
sugar to survive

22
Q

Different flavored foods placed on tips of infants’
tongues

A
  • Sweet food evokes a “smilelike” expression
    followed by sucking.
  • Sour produced pursing and protrusion of lips
  • Bitter produced gaping, movements of spitting, and
    sometimes vomiting movements
23
Q

Specific hungers theory

A

The idea that deficiency of a
given nutrient produces craving (a specific hunger) for
that nutrient

only holds for sweet and salty foods

24
Q

Labeled lines:

A
  • Theory of taste coding in which each taste fiber
    carries a particular taste quality
    § Major source of controversy in literature
  • Other possibility: Patterns of activity across many
    different taste neurons
25
Q

Taste adaptation

A
  • All sensory systems show adaptation effects
  • Constant application of certain stimulus temporarily
    weakens subsequent perception
    § Example: Adaptation to salt in saliva affects our
    ability to taste salt
26
Q

Cross-adaptation:

A

Cross-adaptation: When the taste of one food
affects the taste of another

Example: A sour beverage tastes too sour after
eating a sweet substance

27
Q

Arthur Fox (1931) discovered that phenylthiocarbamide
(PTC) tastes dramatically different to different people

  • Bitter taste to some but not to others
  • 1960s: Started using propylthioracil (PROP)
    instead of PTC because it is safer
A

Arthur Fox (1931) discovered that phenylthiocarbamide
(PTC) tastes dramatically different to different people

  • Bitter taste to some but not to others
  • 1960s: Started using propylthioracil (PROP)
    instead of PTC because it is safer
28
Q

Gene for PTC/PROP receptors discovered in 2003

A
  • Individuals with two recessive genes are
    nontasters of PTC/PROP
  • Individuals with one or more of the genes are
    tasters of PTC/PROP
29
Q

Supertaster

A

Individual who is a taster of PTC/PROP
and has a high density of fungiform papillae
* Perceives the most intense taste sensations

30
Q

Cross-modality matching

A

Ability to match the intensities of sensations that come from different sensory modalities

  • Used to assess intensity of taste sensations for nontasters, medium tasters, and supertasters
31
Q

Health consequences of taste sensation

A
  • Variations in sensory properties of foods and beverages
    affects food preferences and therefore diet
    § For instance, some vegetables have a bitter taste and so
    might be avoided by supertasters
32
Q

Valerie Duffy and colleagues

A

Valerie Duffy and colleagues showed that among men
getting routine colonoscopies, those tasting PROP as the
most bitter had the most colon polyps. Why? Perhaps
because they avoid bitter vegetables

  • Note that fats also taste bitter to supertasters, so this may
    cause them to eat fewer high-fat foods, which could lower
    their risk for heart disease
33
Q

Orthonasal olfaction

A

Olfaction through the nostrils
* Do we learn to like or dislike smells separately for
retronasal versus orthonasal olfaction? Possibly

§ Example: Many people like the smell of freshly
cut grass, but wouldn’t want to eat it

if an aversion is acquired retronasally, it
usually shows up orthonasally as well

§ Example: Becoming sick from eating fish and
then disliking even the smell of fish

34
Q

Chili Peppers

A
  • Acquisition of chili pepper preference depends on
    social influences
  • Restriction of liking to humans
  • Variability across individuals, depending on
    number of papillae
35
Q

Capsaicin:

A

The chemical that produces the burn in
chilis. Desensitizes pain receptors

36
Q

Desensitization:

A

If a food is too hot for your palate, wait for burn
to subside after the first mouthful. Your palate
will desensitize (from the capsaicin) and you
should be able to eat the rest of your meal

Sensation (7 decks)

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