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Medsci 206 > Module B: Chemical Senses > Flashcards

Module B: Chemical Senses Flashcards

1
Q

Sensation

A

Detection of physical stimulus

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2
Q

Perception

A

Interpretation modified by experience

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3
Q

Modality (type)

A

class of stimulus

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4
Q

Location

A

position of stimulus in space

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5
Q

Intensity

A

measure of the severity or amount of the stimulus

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6
Q

Timing

A

Onset, duration and offset of stimulus

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7
Q

5 major modalities

A

vision, hearing, taste, smell and touch

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8
Q

4 other modalities

A

Vestibular(balance)
electrosensory
magnetic
additional somatosensory (pain, temperature, itch, proprioception)

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9
Q

Transduction

A

sensory receptors transform signal into electrical energy

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10
Q

Receptor potential

A

Excitation leads to electrical responce

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11
Q

Receptor specificity

A

Receptors morphologically specialised for specific form of energy

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12
Q

Labelled line

A

neurons from specific receptors are modality specific

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13
Q

Mechanoreceptors:

A

detect mechanical deformation

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14
Q

Mechanical transduction mechanism (and example)

A

mechanical stimulus acts directly on cell structures to cause receptor potential

Eg muscle spindle detecting muscle displacement or position
Eg detection of vibration by the cochlear

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15
Q

Chemical transduction mechanism

A

Chemical utilise intracellular second messenger systems or sense chemical directly (eg salt on tongue)

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16
Q

Photoreceptor transduction mechanism

A

Photoreceptors utilize intracellular second messenger systems

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17
Q

Chemoreceptors in olfactory epithelium and photoreceptors in retins used what transduction mechanism

A

2nd messenger system

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18
Q

Spatial arrangement of receptors: (x3)

A
  • provides information on location of stimulus source on body or in space
  • enables discrimination of size and shape of object
  • enables resolution of fine detail of stimulus or environment
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19
Q

What defines the resolution of the stimulus(sensation)

A

The density of receptors

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20
Q

What area of the retina has a high density of receptors and a small receptor field

A

Fovea of retina

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21
Q

Intensity is determined by the stimulus amplitude which is…

A

the number of neurons activated and frequency (rate) of neural impulses

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22
Q

(Timing) onset, duration and offset of stimulus is coded by…

A

Frequency of the neural activity

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23
Q

Sensory input from the eyes goes to the

A

Thalamus (in forebrain)

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24
Q

Sensory information from the ears and skin goes to the…

A

midbrain then thalamus

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25
Q

Sensory input from taste goes to…

A

the medulla oblongata then thalamus

26
Q

Sensory input from smell goes to…

A

primitive part of cortex then thalamus

27
Q

What are 5 sensory areas in the forebrain

A
  • Primary visual cortex
  • temporal lobe
  • primary sensory cortex
  • Parietal lobe
  • Frontal lobe
28
Q

Pericheral sensory organs project to the cortex through…

A

polysynaptic pathways

29
Q

Diversity and adaptation:

Fish have weak ___ but many use ____ and ____

A

weak vision

use magnetic electrical fields and presure

30
Q

Diversity & adaptation:

In fish, esp Sharks, they use the _______ system, which uses ____-receptors to detect variations in ____

A

lateral line system; mechano-receptors; pressure

31
Q

Diversity & adaptation:

Insects have ____ organs on thorax or legs for localization

A

hearing

32
Q

Whats the oldest and most common sensory system that even brainless bacteria can detect and react to

A

Chemical senses

33
Q

Gustation =

Olfaction =

A 
Gustation = taste 
Olfaction = smell
34
Q

Sensory receptors in the tongue, mouth and near the larynx go to the brain via what Cranial nerves?

A

7 (Facial)
9 (Glossopharyngeal)
10 (Vagus)
And go to the Nucleus of the solitary tract (gustatory nucleus), and then ventral posterior medial nucleus of the thalamus, which then goes to the frontal taste cortex (frontal operculum)

(see image in slide 4, lecture 2 of chemical senses)

35
Q

List the 3 papillae on the tongue and what are the % of them:
(for image of them see slide 5, lecture 2 of chemical senses)

A 
Circumvallate papillae (cranial nerve 9) = 50% (aka vallate papillae)
Foliate papillae = 25%
Fungiform papillae (cranial nerve 7) = 25%
36
Q

What are papillae?

A

Multicellular protuberances surrounded by invaginations in the tongue epithelium. The invaginations form a trench to concentrate tastants. Taste buds are distributed along the lateral surfaces of the papillae protuberances as well as in the trench walls.

37
Q

What is a taste bud made up of?

A 
Taste cells (long) + basal cells (circular) +Microvilli (at one end)
At apex is a taste pore and the other end has Gustatory afferent axons.
38
Q

What are taste cells?

A

Specilized neuroepithelial receptor cells, they cluster around the taste pore (1mm opening)

39
Q

What is the life time of a taste cell and how are they regenerated?

A

2 weeks and are regenerated from basal cells

40
Q

How many taste buds are there

How many taste receptor cells per taste bud

A
  • 2000-5000 on the tongue, plate, epiglottis and esophagus

- 50-150 taste receptor cells per taste bud

41
Q

Fungiform papillae (x4)

A
  • Only found on the anterior two-thirds of the tongue
  • High density
  • mushroom-like
  • each one has 3 tastebuds at their apical surface
42
Q

Circumvallate papillae (4)

A
  • x9 circumvallate papillae
  • align in a V shape (chevron)
  • a the back of the tongue
  • each one has 250 taste buds
43
Q

Foliate papillae (x3)

A
  • x2 foliate papillae
  • present on the posterolateral part of the tongue
  • each has 600 tastebuds
44
Q

At ___ concentrations papillae are selective to specific stiumuls

At ___ concentration they are less sensitive

A

Low; high

45
Q

Activation of taste cells via a stimulus leads to _____ or _____, and then release of _____ or reduction in activity

A

depolarization or hyperpolariation

release of neurotransmitter

46
Q

Most taste (cells) receptors respond to 1 or 2 or more taste stimuli

A

more than 2

47
Q

What are the 5 different tastants?

see slide 9, lec2 of chemical sense for image

A
  • sour
  • bitter
  • salty
  • sweet
  • umami (savory, meat, protein rich)
48
Q

Salt tastes include:

A

NaCl

amino acids like glutamate

49
Q

Sour tastes are associated with:

A

acidity and protons, this indicates the palatability of foods

50
Q

Bitter tastes include:

A

Plant alkaloids like atropine, quinine, stychnine, indicating foods that might be poisonous

51
Q

Describe a Taste cell/receptor

A
  • Are specilized for sensory transduction
  • have an apical and basal domain
  • There are tastant-transducing channels (salt & sour) on the APICAL domain
  • There are G-protein-coupled receptors (for sweet, umami(aa), bitter) on the APICAL domain
  • Voltage regulated Na, K, Ca channels that mediate the release of neurotransmitter on the BASAL domain
52
Q

What in the APICAL domain of a taste cell/receptor

A
  • There are tastant-transducing channels ie ion channels (salt & sour) on the APICAL domain
  • There are G-protein-coupled receptors (for sweet, umami(aa), bitter) on the APICAL domain
53
Q

What in the BASAL domain of a taste cell/receptor

A
  • Voltage regulated Na, K, Ca channels that mediate the release of neurotransmitter on the BASAL domain
  • Endoplasmic reticulum (release Ca2+)
54
Q

Neurotransmitter from the taste receptor is released onto the terminals of…

A

peripheral sensory afferents

55
Q

ATP, GABA and ______ are neurotransmitters found in taste cells

A

Serotonin (with serotonin receptors found on the sensory afferents)

56
Q

Transduction mechanism of salt tastants:

A

Tastants can interact directly with Na+ ion channels by passing through them

-Then the membrane voltage with influence Ca2+ channels on basal membrane and hense neurotransmitter release

57
Q

Transduction mechanism of sour tastants:

A

Tastants can interact directly with K+ ion channels by passing through them or by blocking K+ channels
Then the membrane voltage with influence Ca2+ channels on basal membrane and hense neurotransmitter release

58
Q

Transduction mechanism of bitter, sweet and umami tastants: (x4)

A
  • Tastants bind to G-protein-coupled receptor on apical membrane
  • This activates Phospholipase C, which increases the synthesis of IP3 (2nd messenger)
  • IP3 triggers the release of Ca2+ from internal storage sites
  • Ca2+ opens taste cell ion channels (taste specific), leading to depolarization and transmitter release
59
Q

Bitternes Receptors:

x4

A
  • T2R receptors
  • 30 different types of T2R receptors
  • Each taste cell expresses many or all of the 30 bitter receptors, and each taste cell can only send 1 type of signal to its afferent nerve –> not good at telling bitter tastes apart, only know they are bad
  • Bitter receptors are poison receptors
  • Use 2nd messenger system
60
Q

Sweet receptors:

x4

A
  • T1R receptors
  • Need 2 members of the T1R receptor family: T1R2 & T1R3, if you dont have both wont be able to detect sweetness
  • Use 2nd messenger system
  • Bitter receptor proteins and sweet receptor proteins are expressed in differnet taste cells (so can distinguish between the 2 tastes)
61
Q

Amino Acid (Umami) receptors: (x2)

A
  • T1R receptors

- Need 2 members of the T1R receptor family: T1R1 & T1R3

Medsci 206 (6 decks)

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