week 10 - taste Flashcards
papillae
- extensions of the skin
- help increase surface area of the tongue
Where does transduction occur in the taste system?
when chemicals contact the receptor sites on the tips of taste buds
Why is the taste system considered the gatekeeper of the body?
- identify things that should be consumed for survival
- detect and reject harmful things
- cause good/bad affective responses
What is the taste cell pathway in cranial nerve 7?
takes information from chorda tympani (cn 7) from the front and sides of tongue to brain
What is the taste cell pathway in cranial nerve 9?
takes information from glossopharyngeal nerve (cn 9) from back of tongue
What is the taste cell pathway in cranial nerve 10?
takes information from vagus nerve (cn 10) from mouth and throat
What is the pathway information from cranial nerves to the process of coding?
these pathways make connections in the nucleus of the solitary tract in the spinal cord -> thalamus -> insula -> frontal lobe and frontal perculum
What makes the taste system different from other sensory systems we have learned about?
- no time for information to cross over to the side of brain
- ipsilateral (right side of tongue gets processed by right insula)
t/f: primary tastes are associated with the same receptors
false, they each have their own different type of receptors
monosodium glutamate (MSG)
- genetically based
- flavor enhancer
Water taste receptor experiment
- researchers found sour taste receptors in rats and inhibited them
- resulted in an inability to differentiate water from other substances
What is an example of different chemicals exciting different receptors?
Miracle berries activate sweet receptors in an inappropriate way which causes receptors to respond to any chemicals coming into the mouth
What primary taste receptors are ionotropic?
salty and sour
Salty taste receptors
- excited by Na+
- permits Na+ to cross membrane
Sour taste receptors
- activated by acids
- closes K+ channels
What primary taste receptors are metabotropic?
sweet, bitter, and umami
What is the process of metabotropic taste receptors?
- require a messenger inside of taste receptors as their transduction pathway of effects
- molecule binds to receptor -> g-protein interacts with 2nd messenger
distributed coding
pattern of distribution in which all neurons fire at different rates
Erikson experiment pt. 1 (distributed coding)
- measured action potentials in a specific nerve of the chorda tympani while presenting different taste stimuli to rats
- brain activity was similar for 2 substances but completely different for one which suggests they taste similar
Erikson experiment pt. 2 (classical conditioning)
- shocked rat when they drank a specific substance
- when presented with similar tasting substance, rat stayed away
- continued to drink substance that tasted different
How was distributed coding showcased in Erickson’s experiment?
through both physiological responses with chorda tympani fibers firing as well as behavioral responses
specificity coding
specific receptors coded for a specific taste
Mueller experiment (PTC)
gave mice a PTC gene (not found in mice) and measured the amount of licks when presenting a PTC concentration
What were the results of the Mueller experiment?
number of licks decreased
Mueller experiment (Cyx)
- took out Cyx receptor gene which is a substance mice usually avoid
- mice did not avoid cyx after is was removed
Sato experiment (monkey’s chorda tympani)
- recorded nerve fibers in monkey’s chorda tympani
- results showed that some fibers repsonded best to one of the basic tastes but poorly to the others
How are the taste system and the visual system for color similar?
different parts of pathway contribute to coding
What might cause differences in tasting?
- genetic basis
- distribution of taste receptors
- supertasters (more fungiform paillae -> stronger taste sensitivity
- hormones
