Lecture 22- Taste & Smell

Question 1

What is a taste bud?

Answer 1

group of taste receptors

Question 2

Of the 4 cells found within a taste bud which is the actual taste receptor cell?

Answer 2

type 3

Question 3

Type 3 is the actual taste receptor cell. What is the purpose of type 1,2 and 4?

Answer 3

type 1 and 2 are supporting cells and type 4 is a basal cell

Question 4

What is the purpose of the basal cell in faste bud (type 4)?

Answer 4

makes new sensory receptor cells (receptor cells have a lifetime of 10 days)

Question 5

What are the 3 types of papillae that contain taste buds?

Answer 5

fungiform, foliate and circumvallate

Question 6

What nerve carries taste sensation from the anterior 2/3 of the tongue?

Answer 6

chorda tympani (branch of CN VII)

Question 7

What nerve carries taste sensation from the posterior 1/3 of the tongue?

Answer 7

glossopharyngeal (CN VIII)

Question 8

What nerve carries taste sensation from the pharynx and larynx?

Answer 8

vagus (CN X)

Question 9

What are the 5 basic tastes?

Answer 9

bitter, sweet, salt, sour and umami

Question 10

How is the taste of salt transduced?

Answer 10

passive influx of salt through amiloride sensitive channels causes depolarization

Question 11

What does amiloride block?

Answer 11

passive Na channels that are involved in transducing the “saltly” taste

Question 12

What determines the degree of sourness?

Answer 12

proton concentration

Question 13

What are the two types of sour channels? How does each work?

Answer 13

sour1- H+ blocks K+ channels

sout2- H+ passive influx through Na+ channels

Question 14

How do the two types of bitter channels work?

Answer 14

Bitter 1- GPCRs block K+ efflux

Bitter 2- GPCR (gustucin) uses Gq like activity-IP3 releasing internal Calcium stores

Question 15

What are the two mechanisms that “sweet” is transduced?

Answer 15

1. Gq- PLC->IP3–> Ca (similar to bitter 2)

3. Gs- AC-> cAMP-> PKA-> Phosporalate K Channels and prevent efflux

Question 16

What is the specific name for the GPCR that functions in bitter 2 and sweet?

Answer 16

gustucin

Question 17

What amino acid provides the umami taste?

Answer 17

glutamate (MSG)

Question 18

What is the specific receptor that the umami receptor utilizes?

Answer 18

mFluR4

Question 19

What is the main ingredient that makes food spicy?

Answer 19

capsaicin- triggers a painful heat sensation channel

Question 20

How does capsaicin work?

Answer 20

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

Question 21

Where do odorant molecules first bind once being absorbed into the mucus?

Answer 21

bind to plasma membrane of cilia of olfactory neurons

Question 22

What happens after the cilia of the olfactory neuron are stimulated by odorant molecules?

Answer 22

It triggers Golf cascade–> AC–> cAMP

cAMP opens CNG (Cyclic nucleotide gate) channels which allow an influx of Ca and Na

Question 23

Where is the information from the olfactory neuron sent?

Answer 23

mitral cells of the olfactory bulb

Question 24

Where are the mitral cells located? Where do they receive afferent information from?

Answer 24

Mitral cells are found in the olfactory bulb and receive afferent information from the olfactory neuron

Question 25

How many olfactory neurons project to one mitral cell in the olfactory bulb?

Answer 25

1000s of olfactory neurons can project afferent information to one mitral cell in the olfactory bulb

Question 26

Are olfactory cells slow or fast adapting?

Answer 26

SLOW- the “getting used to and odor” is due to inhibitory central circuits NOT fading receptor response

Question 27

How does your nervous system determine the difference between smells?

Answer 27

Different smells produces specific spatial distribution of activity in the CNS (remember; one neuron can response to MANY different odors-unlike taste receptor cells)

Question 28

Which tastes use the gustducin GPCR?

Answer 28

bitter 2 and sweet

Question 29

Which tastes use the amiloride sensitive Na channels?

Answer 29

Salt and sour2

Question 30

Which two tastes function to block K+ efflux?

Answer 30

sour1 and bitter 2