Gustation

Question 1

What is gustation?

Answer 1

taste 
contact chemosensation (mol has to touch tongue)

Question 2

What makes the tongue the sense organ for gustation?

Answer 2

specialised invaginations called papillae

Question 3

What do papillae do?

Answer 3

invaginations which concentrate chemicals in taste bud region

Question 4

What are the four taste buds in order ( front to back of throat)?

Answer 4

fungiform (25% of taste buds)
filiform
Foliate (25% of taste buds)
Circumvallate (50% of taste buds)

Question 5

Where are the fungiform papillae located ?

Answer 5

tip of tongue

Question 6

Where are the filiform papillae located?

Answer 6

middle of tongue

Question 7

Where are the foliate papillae located?

Answer 7

side of tongue (at the back)

Question 8

Where are the circumvallate located?

Answer 8

back of tongue

Question 9

What are the five basic tastes?

Answer 9

bitter (back of tongue)
sour (side)
Sweet (front + side)
Salty (front + side)
Umami

Question 10

What is the key difference between processing of the basic tastes?

Answer 10

regional differences in the threshold of responsiveness

Question 11

What are taste buds made up of ?

Answer 11

specialised epithelial cells (taste cells)

Microvili (where r are concentrated)

Question 12

Where are microvilli ?

Answer 12

tip of tongue
high SA
concentrate chems onto r proteins

Question 13

What are the 2 transduction domains in taste cells ?

Answer 13

Apical (external)

Basolateral (taste bud)

Question 14

What are the structures of the two domains of the taste cells?

Answer 14

1. Apical = microvili, have ion channels and GPCR

2. Basolateral = taste bud, ion channels and cellular machinery to release NT (serotonin +ATP)

Question 15

Which of the 5 basic tastes are detected by GPCRs?

Answer 15

sweet, bitter, umami

Question 16

Which of the 5 basic tastes are detected by ion channels ?

Answer 16

Salt (na channels)

sour (H+ sensitive)

Question 17

How do sour ion channels work?

Answer 17

H+ sensitive

H+ blocks K+ leaving cell = depolarisation = ca2+ open

Question 18

Which receptor detects sweet and umami ?

Answer 18

T1R

Question 19

What is the structure of T1Rs?

Answer 19

Heterodimers
large N terminal domain
intracellular C terminal
different heterodimers encode sweet and umami
bind to ligands
Graded potentials spread to the basal domain

Question 20

What is the signalling process of sweet taste?

Answer 20

Dowstream signalling
Sucrose, fructose, maltose
Indirect depolarisation
heterodimer = T1R2/ T1R3

Question 21

What is the signalling process of umami?

Answer 21

Umami = meaty taste
Indirect depolarisation of taste cell
Detected by mGluR4 = functional responses to glutamate (0.3 mol/L)
T1R1 / T1R3

Question 22

What is the signalling process for bitterness?

Answer 22

T2R receptor gene encodes GPCR
T2R not present in taste cells expressing T1R subtypes
Indirect depolarisation
GPCR called Alpha-gustducin

Question 23

What are the 3 sections to the central processing of gustation ?

Answer 23

1st order cranial nerves
2nd order (gustation nucleus)
medial half ventral posterior

Question 24

What are the 1st order cranial nerves for gustation?

Answer 24

VII: facial (tongue + palate)
IX: glossopharyngeal (back of tongue)
X: vagus (oesophagus)

Question 25

What is the gustation nucleus?

Answer 25

solitary tract which facilitates integration of sensory info

Question 26

What is the role of the medial half ventral posterior medial nucleus ?

Answer 26

VPM projections to anterior ínsula in temporal lobe

Sensory taste centre in orbitofrontal cortex

Question 27

What gives us our perception of food?

Answer 27

orbiofrontal cortex