Transcript Your genes: Test #2

Taste: Gustation
Tongue
• Combination of 8
muscles
• 4 intrinsic: change
shape of the tongue,
not connected to bone
• 4 extrinsic: change
position of tongue,
connected to bone
Basic Anatomy
Longest tongue?
Blue Whale
• Tongue weighs as much as an elephant
Giraffe
• 18-20 inches
Tube-lipped Nectar Bat
1.5x its body size
Darwin hawkmoth:
Xanthophan morgani praedicta
• 10 inch tongue
Jobs of the tongue
• manipulates food for mastication
• Primary taste organ (gustatory organ)
• secondary function of the tongue is phonetic
articulation in humans
• natural means of cleaning one’s teeth
Intrinsic Muscles
• lengthening and
shortening it
• curling and uncurling its
apex and edges
• flattening and rounding
its surface
• provides shape, and
helps facilitate speech,
swallowing, and eating
Extrinsic Muscles
• Genioglossus: protrudes
the tongue
• Hyoglossus: depresses the
tongue
• Styloglossus: elevates and
retracts the tongue
• Palatoglossus, depresses
the soft palate, moves the
palatoglossal fold
towards the midline, and
elevates the back of the
tongue.
Cat Tongues…
• What purpose do the
barbs serve on a cat’s
tongue?
• What adaptive
advantage might this
serve?
Lab: try it at home
http://sciencenetlinks.com/student-teacher-sheets/blue-tongue/
Papillae: house taste buds
• Peg-like projections
• Abrasive feel
Several types…
2 forms: fungiform and circumvallate
• Fungiform: entire surface, concentrated at tip
and sides. Taste buds located at top
• Circumvallate: largest and least numerous,
make a v at back of the tongue, taste buds
located in side walls
taste buds
• Chemoreceptors
• Food chemicals dissolved in saliva
• Complement smell receptors and respond to
many of the same stimuli
• Mostly on tongue
• Soft palate, cheeks,
Pharynx, epiglottis as well
repair
• Routinely damaged
• Replaced every 7-10 days
Taste buds
• 50-150 columnar taste receptor cells, bundled
together
Microvilli, house the taste
receptors
“Taste nerves”
• Network of dendrites
• Interwoven between taste cells
• Chemical binds to receptor – triggers action
potential
• Travels via cranial nerves to brain
• Parietal and temporal lobes of cerebral cortex
• Respond to different stimuli
• Readily adapt
• Taste preferences change with needs
Name the primary taste sensations…
They are…
• Sweet - usually indicates energy rich nutrients
• Salty - allows modulating diet for electrolyte
balance
• Sour - typically the taste of acids, high in
vitamin C
• Bitter - allows sensing of diverse natural toxins
• Umami - the taste of amino acids (e.g. meat
broth or aged cheese)
• Not elicited by a single chemical 
• Combinations of chemicals
• Lead salts – taste sweet, licking lead paint???
Sensitivity varies: most sensitive?
Least?
Examples of some human thresholds
Taste
Substance
Threshold for
tasting
Salty
NaCl
0.01 M
Sour
HCl
0.0009 M
Sweet
Sucrose
0.01 M
Bitter
Quinine
0.000008 M
Umami
Glutamate
0.0007 M
Varies in the animal kingdom
• Pleasant, unpleasant, indifferent
• Cats don’t taste “sweet” – deletion of sweet
receptor gene
• Birds can’t taste chili peppers, squirrels can
• One cannibal says to another, while eating a
clown….”does this taste funny to you?”
Lab!
• Mapping sensitivity of the tongue
Extra credit
• Bring a can or bottle of soda tomorrow for
class
• MUST BE UNOPENED
Bellringer
• Super taster article
Soda experiment
• Pour freshly opened carbonated beverage into
a glass, almost to the top
• Prepare your phone (use it as a timer)
• Stick your tongue into the soda and start your
timer
• How long can you “stand it”?
What happened?
• Carbonic anhydrase – enzyme in saliva
• Changes carbon dioxide in drink to carbonic
acid
• Triggers nocioceptors
Next test…
• Brush teeth, then drink OJ – bitter?
• 2/3 of people, yes
• Why?
– Toothpaste’s sudsing agent (SLS) counteracts
sweetness, allows other flavors to come to surface
– Ability to detect bitterness = in your genes
Not the whole story…
YOUR GENES: TEST #2 – PTC PAPER
Phenylthiocarbamide (PTC)
• Dominant allele: sensitive to bitter tastes
• Recessive allele: not sensitive
• Incompletely dominant…
– PP: high sensitivity
– Pp: Mildly sensitive
– pp: nontaster
• http://learn.genetics.utah.edu/content/inherit
ance/ptc/
Pregnancy and beyond…
• http://www.npr.org/2011/08/08/139033757/
babys-palate-and-food-memories-shapedbefore-birth