8.6B. The senses of taste and smell. Flashcards

1
Q

I. PHYSIOLOGY OF TASTE SENSATION
1. What are the features of gustation?

A
  • 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.
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2
Q

I. PHYSIOLOGY OF TASTE SENSATION
2. Location of tase buds

A
  • 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.
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3
Q

I. PHYSIOLOGY OF TASTE SENSATION - Gustatory system
1. What are the features of gustatory system?

A
  • 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.
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4
Q

I. PHYSIOLOGY OF TASTE SENSATION - Gustatory system
2. What is the neuronal pathway of gustatory system?

A
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5
Q

I. PHYSIOLOGY OF TASTE SENSATION - taste transduction
3. What is the signal transduction of salty sensation?

A

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!)

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6
Q

I. PHYSIOLOGY OF TASTE SENSATION - taste transduction
4. What is the signal transduction of sour sensation?

A

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!)

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7
Q

I. PHYSIOLOGY OF TASTE SENSATION - Sweet, bitter, umami sensation
5. What is umami?

A

Umami = taste of meat + AAs (glutamine and aspartate)

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8
Q

I. PHYSIOLOGY OF TASTE SENSATION - Sweet, bitter, umami sensation
6. What is bitter tase?

A

Bitter taste = toxic compounds
=> do not swallow it, spit it out (protective mechanism)

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9
Q

I. PHYSIOLOGY OF TASTE SENSATION - Sweet, bitter, umami sensation
7. What is Sweet taste?

A

Sweet taste = sugar molecules

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10
Q

I. PHYSIOLOGY OF TASTE SENSATION - Sweet, bitter, umami sensation
8. What is the receptor for bitter sensation?

A
  • 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)
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11
Q

I. PHYSIOLOGY OF TASTE SENSATION - Sweet, bitter, umami sensation
9. What are the receptors for Sweet + umami sensation?

A

Sweet + umami sensation: mediated by T1R – work in dimers, 2 different receptors from one dimer
 Sweet: T1R2 + T1R3
 Umami: T1R1 + T1R3

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12
Q

I. PHYSIOLOGY OF TASTE SENSATION - Sweet, bitter, umami sensation
10A. What is the signal transduction for the bitter, sweet and umami sensation?

A

Umami = taste of meat + AAs (glutamine and aspartate)

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13
Q

I. PHYSIOLOGY OF TASTE SENSATION - Sweet, bitter, umami sensation
10B. What happen if Ca2+ activates TRPM5 (Ca2+-sensitive TRP channel-cation channel)?

A
  • Opened by Ca2+ -> Na+-influx -> depolarization -> the whole cycle
  • TRPM5 serves as an amplification mechanism
    which ↑Ca2+-signal + release of transmitter
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14
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell)
1. What is the role of the human olfactory system?

A

The human olfactory system detects chemical stimuli from the air as various smells

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15
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell)
2. Where is the human olfactory system found?

A

The system is found in the nasal cavity, whereas the olfactory epithelium is found in the posterior-superior part of the nasal cavity.

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16
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell)
3. What are the types of cells and axons can we find in the human olfactory system?

A
  • 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.
17
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell)
4. What is the structure of olfactory system?

A
18
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell)
5. Can olfactory stimuli evoke emotional response? If yes, how?

A

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)

19
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Organization of olfactory system
6A. Describe the Organization of olfactory system?

A
20
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Organization of olfactory system
6B. What can we find in the olfactory epithelium?

A

In the olfactory epithelium, we can find bipolar cells which are dedicated to only 1 olfactory
sensation

21
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Organization of olfactory system
6C. What types of receptors can we find at endings of each bipolar cell?

A
  • Each cell, at their endings, have different GPCRs
22
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Organization of olfactory system
6D. How is each odorant recognized?

A
  • 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
23
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Organization of olfactory system
6E. Where will the central axon of the bipolar cells go?

A

The central axon of the bipolar cells will go to the olfactory bulb, mainly to the glomeruli

24
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Organization of olfactory system
6F. What are the structure and localization of glomeruli in olfactory system?

A
  • 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
25
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell)
7. How many olfactory receptors that a human have?

A

Even though we have 350 different receptors which recognize 350 different epitopes, the signal transduction mechanism is the same

26
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Mechanism and regulation of olfactory sensation
8A. What is the mechanism of olfactory sensation?

A
27
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Mechanism and regulation of olfactory sensation
8B. What happen if cAMP bind to CNG?

A

cAMP will activate CNG (cyclic nucleotide gated channels) – a cation channel
=> ↑Na+, K+-permeability

28
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Mechanism and regulation of olfactory sensation
9A. What are the mechanisms for the adaptation of olfactory sensation?

A
29
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Mechanism and regulation of olfactory sensation
9B. What happen if we activate PDE?

A

activates PDE
-> ↓cAMP
-> ↓olfactory signal

30
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Mechanism and regulation of olfactory sensation
9B. What happen if there is an inhibition of CNG channel?

A

↓Ca2+ + Na+-influx

31
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Mechanism and regulation of olfactory sensation
9C. What happen if we activate activate Na+/Ca2+- exchanger?

A

activateNa+/Ca2+-exchanger
-> ↑Ca2+ efflux
-> ↓[Ca2+]IC…
-> inhibit activation of
depolarization
- odorant molecules activate GPCRs

32
Q

II. PHYSIOLOGY OF OLFACTORY SENSATION (smell) - Mechanism and regulation of olfactory sensation
9D. What happen to GPCRs after activation?

A

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)