Lecture 22- Taste & Smell Flashcards
What is a taste bud?
group of taste receptors
Of the 4 cells found within a taste bud which is the actual taste receptor cell?
type 3
Type 3 is the actual taste receptor cell. What is the purpose of type 1,2 and 4?
type 1 and 2 are supporting cells and type 4 is a basal cell
What is the purpose of the basal cell in faste bud (type 4)?
makes new sensory receptor cells (receptor cells have a lifetime of 10 days)
What are the 3 types of papillae that contain taste buds?
fungiform, foliate and circumvallate
What nerve carries taste sensation from the anterior 2/3 of the tongue?
chorda tympani (branch of CN VII)
What nerve carries taste sensation from the posterior 1/3 of the tongue?
glossopharyngeal (CN VIII)
What nerve carries taste sensation from the pharynx and larynx?
vagus (CN X)
What are the 5 basic tastes?
bitter, sweet, salt, sour and umami
How is the taste of salt transduced?
passive influx of salt through amiloride sensitive channels causes depolarization
What does amiloride block?
passive Na channels that are involved in transducing the “saltly” taste
What determines the degree of sourness?
proton concentration
What are the two types of sour channels? How does each work?
sour1- H+ blocks K+ channels
sout2- H+ passive influx through Na+ channels
How do the two types of bitter channels work?
Bitter 1- GPCRs block K+ efflux
Bitter 2- GPCR (gustucin) uses Gq like activity-IP3 releasing internal Calcium stores
What are the two mechanisms that “sweet” is transduced?
- Gq- PLC->IP3–> Ca (similar to bitter 2)
3. Gs- AC-> cAMP-> PKA-> Phosporalate K Channels and prevent efflux
What is the specific name for the GPCR that functions in bitter 2 and sweet?
gustucin
What amino acid provides the umami taste?
glutamate (MSG)
What is the specific receptor that the umami receptor utilizes?
mFluR4
What is the main ingredient that makes food spicy?
capsaicin- triggers a painful heat sensation channel
How does capsaicin work?
It binds to and triggers heat sensitive pain receptors that allow an influx of Na or Ca and give the sensation of the spicy tast
Where do odorant molecules first bind once being absorbed into the mucus?
bind to plasma membrane of cilia of olfactory neurons
What happens after the cilia of the olfactory neuron are stimulated by odorant molecules?
It triggers Golf cascade–> AC–> cAMP
cAMP opens CNG (Cyclic nucleotide gate) channels which allow an influx of Ca and Na
Where is the information from the olfactory neuron sent?
mitral cells of the olfactory bulb
Where are the mitral cells located? Where do they receive afferent information from?
Mitral cells are found in the olfactory bulb and receive afferent information from the olfactory neuron
How many olfactory neurons project to one mitral cell in the olfactory bulb?
1000s of olfactory neurons can project afferent information to one mitral cell in the olfactory bulb
Are olfactory cells slow or fast adapting?
SLOW- the “getting used to and odor” is due to inhibitory central circuits NOT fading receptor response
How does your nervous system determine the difference between smells?
Different smells produces specific spatial distribution of activity in the CNS (remember; one neuron can response to MANY different odors-unlike taste receptor cells)
Which tastes use the gustducin GPCR?
bitter 2 and sweet
Which tastes use the amiloride sensitive Na channels?
Salt and sour2
Which two tastes function to block K+ efflux?
sour1 and bitter 2
