Gustation Flashcards
1
Q
Primary tastes
A
- salty; TFS = 0.01M
- sour; TFS = 0.009M
- sweet; TFS = 0.01M
- bitter; TFS = 0.000008M
- umami
2
Q
Why is the threshold for stimulation of bitter taste very low
A
it is primarily used to detect poisons (avoid)
3
Q
Role of the papillae
A
- help grip food while your teeth are chewing
- small buds on tongue
- contain taste buds
4
Q
Components of the taste buds
A
- taste cell
- microvilli
- supporting cell
- connective tissue
- sensory nerve fibres
5
Q
Role of the taste cell
A
sense various chemical compounds in foods and transmit these signals through gustatory nerve fibers to the central nervous system
5
Q
Role of the taste cell
A
sense various chemical compounds in foods and transmit these signals through gustatory nerve fibers to the central nervous system
6
Q
Organisation of taste bud
A
- found in papillae
- ~4000 on average, number declines with age
- each bud contains ~50-100 taste cells
- apical microvilli of taste cells are exposed to saliva through taste pore
7
Q
Taste cell
A
- mature taste cells are short-lived and continuously regenerated from basal cells
- action potential releases NT which activates gustatory afferent fibre
8
Q
How are substances sensed
A
- at microvilli
- induces depolarisation and AP generation
9
Q
Salty transduction
A
- satly-sensing taste cells express amiloride-sensitive sodium channels (ENaC)
- sodium enters through channel to depolarise cell
- potassium-type salts also stimulate cells because of leak potassium channels and change in EK
10
Q
Sour transduction
A
- sour-sensing taste cells express proton-sensitive potassium leak channels
- sour is the taste of acid (H+)
- Acid protons block potassium channels, reducing aK and depolarising cell
- newly discovered acid-sensing cation channel gated by H+
11
Q
Bitter transduction
A
- bitter-sensing taste cells use 7-TM receptors coupled to various G proteins
- recognises toxic compounds
- family of related bitter receptors (T2 receptors)
- some receptors couple to Gq which activates PLC to increase Ca2+ through IP3
- other receptors couple to gustducin which activates cyclic nucleotide phosphodiesterases
- few bitter compounds block leak potassium channels
12
Q
Sweet transduction
A
- sweet-sensing taste cells use 7-TM receptor coupled to Gs
- sugars act through Gs to produce cAMP
- PKA phosphorylates and closes K leak channels (depolarisation)
12
Q
Sweet transduction
A
- sweet-sensing taste cells use 7-TM receptor coupled to Gs
- sugars act through Gs to produce cAMP
- PKA phosphorylates and closes K leak channels (depolarisation)
13
Q
Transduction of artificial sweeteners
A
- bind receptors coupled to Gq which activates PLC to increase Ca2+ through IP3
