8.6B. The senses of taste and smell. Flashcards
I. PHYSIOLOGY OF TASTE SENSATION
1. What are the features of gustation?
- The human sense of taste (gustation) uses taste bud sensory receptors to detect chemical stimuli and interpret them as different tastes.
- Most taste buds are on the tongue, but others are on the palate, pharynx and larynx.
- Taste buds on the tongue are located near the base of fungiform, foliate and circumvallate papillae.
I. PHYSIOLOGY OF TASTE SENSATION
2. Location of tase buds
- Most taste buds are on the tongue, but others are on the palate, pharynx and larynx.
- Taste buds on the tongue are located near the base of fungiform, foliate and circumvallate papillae.
I. PHYSIOLOGY OF TASTE SENSATION - Gustatory system
1. What are the features of gustatory system?
- In the front of the tongue, the facial N (chorda tympani) is represented.
- In the back of the tongue, the
glossopharyngeal N is responsible for innervating taste buds + cells. - In the pharynx, it is a branch of the Vagus N.
I. PHYSIOLOGY OF TASTE SENSATION - Gustatory system
2. What is the neuronal pathway of gustatory system?
I. PHYSIOLOGY OF TASTE SENSATION - taste transduction
3. What is the signal transduction of salty sensation?
Sensation of Na+-ions
-> Na+-influx via ENaC
-> depolarization
-> VG Ca2+-channels open
-> ↑[Ca2+]IC
-> transmitter release
-> will activate nerve terminal
-> receptor potential – if above threshold
-> opening of VG Na+-channels
-> AP formation
(- NOTE: salt and sour sensing cells are 2 DIFFERENT cells!)
I. PHYSIOLOGY OF TASTE SENSATION - taste transduction
4. What is the signal transduction of sour sensation?
Sour sensation: (taste of protons – sour sensation has ↑[H+])
- Sensation of H+-ions
-> activate cation channels = TRPP3
-> Na+- influx = same PW as for salty sensation
(- NOTE: salt and sour sensing cells are 2 DIFFERENT cells!)
I. PHYSIOLOGY OF TASTE SENSATION - Sweet, bitter, umami sensation
5. What is umami?
Umami = taste of meat + AAs (glutamine and aspartate)
I. PHYSIOLOGY OF TASTE SENSATION - Sweet, bitter, umami sensation
6. What is bitter tase?
Bitter taste = toxic compounds
=> do not swallow it, spit it out (protective mechanism)
I. PHYSIOLOGY OF TASTE SENSATION - Sweet, bitter, umami sensation
7. What is Sweet taste?
Sweet taste = sugar molecules
I. PHYSIOLOGY OF TASTE SENSATION - Sweet, bitter, umami sensation
8. What is the receptor for bitter sensation?
- Bitter sensation: T2R (taste type 2 receptor – GPCR)
=> T2R have 30 subtypes, but none of them are perceived any differently (all are bitter either way)
I. PHYSIOLOGY OF TASTE SENSATION - Sweet, bitter, umami sensation
9. What are the receptors for Sweet + umami sensation?
Sweet + umami sensation: mediated by T1R – work in dimers, 2 different receptors from one dimer
Sweet: T1R2 + T1R3
Umami: T1R1 + T1R3
I. PHYSIOLOGY OF TASTE SENSATION - Sweet, bitter, umami sensation
10A. What is the signal transduction for the bitter, sweet and umami sensation?
Umami = taste of meat + AAs (glutamine and aspartate)
I. PHYSIOLOGY OF TASTE SENSATION - Sweet, bitter, umami sensation
10B. What happen if Ca2+ activates TRPM5 (Ca2+-sensitive TRP channel-cation channel)?
- Opened by Ca2+ -> Na+-influx -> depolarization -> the whole cycle
- TRPM5 serves as an amplification mechanism
which ↑Ca2+-signal + release of transmitter
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell)
1. What is the role of the human olfactory system?
The human olfactory system detects chemical stimuli from the air as various smells
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell)
2. Where is the human olfactory system found?
The system is found in the nasal cavity, whereas the olfactory epithelium is found in the posterior-superior part of the nasal cavity.