Sen/Perc: Taste Flashcards

• sensations evoked by solutions in the mouth that contact the receptors on the tongue + roof of the mouth

• sensation of odor when chewing and swallowing
  • forces an odorant in the mouth up behind the palate into the nose

• the combination of true taste (sweet, sour, bitter) and retronasal olfaction

• Patient case: Damaged taste, but normal olfaction—could
  smell lasagna, but it had no flavor.
• Lab: Chorda tympani anesthetized
  with lidocaine.
• Chorda tympani: The branch of cranial nerve VII (the
  facial nerve) that carries taste information from the
  anterior, mobile tongue (the part you can stick out).
  15.1 Taste versus Flavor 3

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

• contribute greatly to retronasal olfaction.
• may increase perceived sweetness without adding more sugar
  • Potential way to increase sweet flavor without adding
    more calories.
    
    

• Create neural signals conveyed to brain by taste nerves
• Are embedded in structures—papillae (bumps on
  tongue)
• Contain taste receptor cells
• Send information to brain via cranial nerves

1. Filiform papillae:
2. Fungiform papillae
3. Foliate papillae
4. Circumvallate papillae

• Small structures on the tongue that provide most of the bumpy appearance.
• Have no taste function

• Mushroom-shaped structures (maxdiameter 1 mm) distributed most densely on edges of tongue,
  • especially the tip.
• Average of six taste buds per papilla are buried in the surface.

• 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.

• 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.

measured taste thresholds at different parts of the tongue

• replotted Hänig’s data and labeled it “sensitivity” instead of thresholds.
• The actual variations in the thresholds were small,
  • but Boring’s replotting made them look big
    
    

• Sweet, sour, salty, and bitter are tasted all over the tongue
  • not just in the locations indicated by this scientific urban legend
    
    

• 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) // extensions of the cell membrane.

Any stimulus that can be tasted

1. Some are made up of small, charged particles that
   taste salty or sour. (Small ion channels in microvilli membranes)
   1. allow some types of charged particles to enter but not
      others.
2. perceived via G protein-coupled receptors (GPCRs) similar to that in the olfactory system.
   1. taste sweet or bitter.

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

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

• 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, (may be an integration area)
    
    

Plays an important role in processing taste information in the brain

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

1. Salty
2. Sour
3. Bitter
4. Sweet

• made up of two charged particles: cation and anion.
• Ability to perceive is not static.
• Low-sodium diets = increase sensitivity to salty foods over time.

• Early experiences can modify salt preference
• Chloride-deficiency in childhood leads to an increased preference for salty foods later.
• Gestational experiences may affect liking for saltiness.

• Comes from acidic substances
• high acid concentrations = will damage both external and internal body tissues.

Prototypically bitter-tasting substance.

• Cannot distinguish between tastes of different bitter compounds.
• Many substances are poisonous.
• Ability to “turn off” bitter sensations—beneficial to liking certain vegetables.
• Bitter sensitivity is affected by hormone levels in women (intensifies during pregnancy)

• Evoked by sugars.
• Many different sugars taste sweet.
  • Glucose: Principle source of energy for most animals.
  • Fructose: Even sweeter than glucose.
  • Sucrose: Common table sugar; combination of glucose and fructose.

• Single receptor responsible for all sweet perception.
  • Different sweeteners stimulate different parts of
    receptor.
  • Artificial sweeteners stimulate this receptor as well.

• Candidate for fifth basic taste
• From monosodium glutamate (MSG)
• Glutamate: Important neurotransmitter

• Can lead to numbness, headache, flushing, tingling,
  sweating, and tightness in the chest
  • if sensitive individuals consume a large amount
  • For most people, MSG does not pose a problem in small doses

• important nutrient.
• Fat molecules evoke tactile sensations like oily, viscous, creamy, etc.
• Rats have fatty acid receptors on their tongues and humans may, too.
• Digesting fat in the gut produces conditioned preferences for
  the sensory properties of the food containing fat.

• 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

• discovered in 2003.
• Individuals with two recessive genes are non-tasters of PTC/PROP.
• Individuals with one or more of the genes are tasters of PTC/PROP.

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

• 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
• Nontasters match the bitterness of PROP to the same intensity as the sound of a watch or a whisper.

• same intensity as the smell of frying bacon or the pain of a mild headache

• same intensity as the brightness of the sun or the most intense pain ever experienced.

• Variations in sensory properties of foods and beverages affect food preferences (diet)
  • EX: some vegetables have a bitter taste and so might be avoided by supertasters.
    
    
• fats also taste bitter to supertasters => low fat food => lower risk of heart disease

Helps us identify objects in the environment

Helps us identify nutrients and antinutrients.

might signal poisons

configured to detect acidic solutions that might harm the body

our bodies need sodium and sugar to survive

evokes a “smilelike” expression followed by sucking.

produces pursing and protrusion of lips

produces gaping, movements of spitting, and sometimes vomiting movements.

• The idea that deficiency of a given nutrient produces craving (a specific hunger) for that nutrient.
• Cravings for salty or for sweet = deficiencies in those substances

• We come to like or dislike foods based on the consequences of eating
  them.
• “Evaluative conditioning”
• Foods with a positive or negative valence transfer to other neutral foods.
• We regulate our food through a combination of hardwired tastes and learned responses
  • from food flavors.

• When the taste of one food affects the taste of another.
  
  • Example: A sour beverage tastes too sour after eating a
    sweet substance.

• Olfaction through the nostrils.
• Do we learn to like or dislike smells separately for
  retronasal versus orthonasal olfaction?
  
  • Example: Many people like the smell of freshly cut
    grass => don't want to eat it.

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

The chemical that produces the burn in chilis; desensitizes pain receptors.

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