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.
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell)
3. What are the types of cells and axons can we find in the human olfactory system?
- The system is found in the nasal cavity, whereas the olfactory epithelium is found in the posterior-superior part of the nasal cavity.
- There, we can find bipolar olfactory cells which have a peripheral axon and a central axon.
- The peripheral axon ends in the olfactory epithelium and is the receptor which can detect the chemical stimuli.
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell)
4. What is the structure of olfactory system?
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell)
5. Can olfactory stimuli evoke emotional response? If yes, how?
YES!!! IT CAN!!!
- In addition to the smell sensation, this system is closely attached to structures responsible for emotional responses -> olfactory stimuli can evoke emotional reactions (disgusting, attractive)
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Organization of olfactory system
6A. Describe the Organization of olfactory system?
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Organization of olfactory system
6B. What can we find in the olfactory epithelium?
In the olfactory epithelium, we can find bipolar cells which are dedicated to only 1 olfactory
sensation
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Organization of olfactory system
6C. What types of receptors can we find at endings of each bipolar cell?
- Each cell, at their endings, have different GPCRs
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Organization of olfactory system
6D. How is each odorant recognized?
- Each odorant is recognized by an unique combination of receptors.
- Different compound is recognized by several different odorant receptors, because each compound has different structures - the olfactory epitopes => the pattern of which odorant receptors get activated, will cause the specific olfactory sensation
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Organization of olfactory system
6E. Where will the central axon of the bipolar cells go?
The central axon of the bipolar cells will go to the olfactory bulb, mainly to the glomeruli
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Organization of olfactory system
6F. What are the structure and localization of glomeruli in olfactory system?
- The glomeruli is a collection of neurons, where each glomeruli will have neurons from cells that all have the same specific receptor on the periphery
- In the olfactory bulb, the localization of the same glomeruli is symmetric in both sides
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell)
7. How many olfactory receptors that a human have?
Even though we have 350 different receptors which recognize 350 different epitopes, the signal transduction mechanism is the same
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Mechanism and regulation of olfactory sensation
8A. What is the mechanism of olfactory sensation?
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Mechanism and regulation of olfactory sensation
8B. What happen if cAMP bind to CNG?
cAMP will activate CNG (cyclic nucleotide gated channels) – a cation channel
=> ↑Na+, K+-permeability
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Mechanism and regulation of olfactory sensation
9A. What are the mechanisms for the adaptation of olfactory sensation?
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Mechanism and regulation of olfactory sensation
9B. What happen if we activate PDE?
activates PDE
-> ↓cAMP
-> ↓olfactory signal
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Mechanism and regulation of olfactory sensation
9B. What happen if there is an inhibition of CNG channel?
↓Ca2+ + Na+-influx
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Mechanism and regulation of olfactory sensation
9C. What happen if we activate activate Na+/Ca2+- exchanger?
activateNa+/Ca2+-exchanger
-> ↑Ca2+ efflux
-> ↓[Ca2+]IC…
-> inhibit activation of
depolarization
- odorant molecules activate GPCRs
II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Mechanism and regulation of olfactory sensation
9D. What happen to GPCRs after activation?
GPCRs will after activation get desensitized by phosphorylation and arrestin binding
=> If the odorant stimulus is continuously present, after a while we will not feel it, because of the strong desensitization (protects nervous system from exhaustion)
