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Neuroscience Semester 2 > Chemical Senses > Flashcards

Chemical Senses Flashcards

1
Q

What receptors do chemical receptors utilise?

A

Chemoreceptors

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2
Q

What receptor is used for smell?

A

Ofactory receptor

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3
Q

What class of chemoreceptors are gustatory and olfactory receptors?

A

Exteroreceptors

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4
Q

What are chemoreceptors?

A

Receptors thst generate a signal when they bind to chemicals

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5
Q

What is olfaction?

A

Information about if airborne molecules (odorants)

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6
Q

What is gustation?

A

Information about ingested substances

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7
Q

Olfaction is also known as….

A

Distance chemosensation

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8
Q

What does the interpretation of oflactory receptors rely on?

A
  • threshold for AP of that odorant
  • concentration of odorant
  • combination of many odorants to make one odour
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9
Q

What is a natural odour?

A

Combination if different odorant

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10
Q

Whg is the olfactory/nasal epithelium so important?

A

Contain olfactory receptor neurones-detect airborne odorants

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11
Q

What is the cribriform plate?

A

Bone plate with pores that is positioned between oflactory receptor neurones and the olfactory bulb

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12
Q

Where are the olfactory receptor proteins found?

A

Oflactory receptor neurone cillia

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13
Q

Olfactory cillia are found in a layer of mucus. How does this help?

A

Mucus traps and concentrates odorants causing amplification of the signal

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14
Q

The olfactory mucus layer is secreted by what?

A

Bowmans gland

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15
Q

Why are there stem cells found close to basal lamina in the nose?

A

As olfactory neurones are prone to damage - last between 6-8 weeks

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16
Q

How are odours transduced?

A

Using GPCRs

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17
Q

Why are GPCRs so useful when detecting odorants?

A

They have constitutive and variable regions. Variable regions allow the detection of varying odorants

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18
Q

Pathway of olfactory GPCRs?

A

Odorant binds GPCR- Golf subunit dissociates-Golf adenylase cyclase producing cAMP- cAMP causes the opening of cAMP gated Na/Ca channel- if this causes threshold to be surpassed an AP is transduced

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19
Q

When a GPCR activates Calcium influx,what does the calcium cause? (In olfaction)

A

Ca can bind to chloride channels causing an eflux of chloride ions increasing polarisation.

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20
Q

How does repolarisation of the olfactory receptor neurone occur?

A

It occurs via a calcium 2+ and sodium 1+ exhanger causing repolarisation

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21
Q

What is across fibre pattern coding?

A

Odorants cause different levels of depolarisation in different neurones. The across fibre pattern is the pattern it creates

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22
Q

What are olfactory glomeruli?

A

Where the receptor neurones AP converge causong amplification

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23
Q

What neurones carry AP from glomeruli to the olfactory bulb?

A

Mitral cells

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24
Q

What is the central processing pathway of the olfactory system?

A

Olfactory receptors- olfactory bulb-to pyriform complex via the mitral cells (travel through the cribriform plate.

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25
Q

What is contact chemosensation?

A

Gustation

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26
Q

What are taste papillae?

A

Specialised invaginations on the tounge

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27
Q

What are the 4 types of papilla?

A

Filliform papilla
Fungiform papilla
Circumvallate
Follate papilla

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28
Q

How many tasted buds of filliform papilla?

A

No taste buds

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29
Q

How many taste buds in fungiform papilla?

A

25% of all tastebuds (3 on each apical surface)

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30
Q

How many taste buds on circumvallate?

A

50% of taste buds 250 taste buds in each trench

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31
Q

How many taste buds does folate papilla have?

A

25% of tastebuds (parallel ridge with ~600 on the ridges)

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32
Q

Where are papilla postitioned?

A

Positioned in troughs when food is dissolved it accumulates in higher concentration in trough papilla are in- contain taste buds sensory cells

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33
Q

What are the 5 basic tastes?

A 
Bitter ( caffeine, nicotine)
Sour (Acid)
Sweet (glucose)
Salty (NaCl)
Umami (meaty taste-glutamate)
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34
Q

What is the structure of a Taste bud?

A

Found in trough with pores on whic you find microvilli that increase surface area for taste receptors

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35
Q

Why is taste bud pore useful?

A

Further concentrates Ligands

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36
Q

What are the 2 domains of a taste bud?

A

Apical (external environment)

Basolateral (taste bud)

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37
Q

What receptors are on the apical surface of a taste bud?

A

Ion-channels (sweet/sour)

GPCRs (sweet,bitter&umami)

38
Q

How are gustation neurones stimulated?

A

Via the release of ions through ion channels and use of cellular machinery to release neurotransmitters , through the basolateral surface

39
Q

What cranial nerves transduce gustation impulses?

A

Facial nerve (7)
Glossopharyngeal (9)
Vagus (10)

40
Q

What neurotransmitters are utilised in gustation?

A

Serotonin and ATP

41
Q

What does salt tasting reception utilise?

A

Utilise an Amiloride sensitive Na+ channel. Cause direct depolarisation of the taste cell.

42
Q

What does Acid tasting utilise?

A

H+ sensitive transient receptor potential (TRP) channel. Cause direct depolarisation of taste cell.

43
Q

What GPCRs are utilised for sweet and umami tastes?

A

T1R family

44
Q

How do T1Rs work during taste of sweet and umami?

A

They form Heterodimers, have many monomers with varying combinations to code for varying ligands- example different ones for sweet and umami.

45
Q

What is the sweet heterodimer?

A

T1R-2, T1R-3

46
Q

What does T1R-2, T1R-3 detect in gustation?

A

Sucrose,fructose,glucose and maltose

47
Q

What is the mechanism of sweet signalling?

A

GPCR activates phospholipase Cbeta2, which cause calcium release of endoplasmic recticulum causing sodium release causing depolarisation.

48
Q

What T1Rs does umami signalling utilise?

A

T1R-1/3

49
Q

What is the bitter signalling pathway like?

A

Same as sweet but the alpha subunit is alpha gustducin

50
Q

Where do the gustatory cranial nerves go to?

A

Solitary tract nucleus

51
Q

What makes up the optic nerve?

A

Retinal ganglion axons

52
Q

What is partial decussation at the optic chiasm?

A

This is where optic nerves cross from either eye. Contralateral side and ipsilateral side travel to opposite sides.

53
Q

Where do retinal ganglion cells terminate?

A

Lateral geniculate nucleus

54
Q

What are the 3 layers of the eye?

A

Sclera, choroid and retina

55
Q

What is the fluid in the eye?

A

Vitreous humour

56
Q

Where do you find the cornea and lens?

A

At the front of the eye

57
Q

What’s the purpose of cornea and lens?

A

Cornea provides most refraction and lens provides fine tuning adjustable refraction

58
Q

How do you focus further?

A

Ciliary muscles relax, ligaments tighten causing outwards pull- less refractive power.

59
Q

How do you focus nearer?

A

Ciliary muscles contract ligaments relax lens relax thickening- focus near more refractive power.

60
Q

What is emnotropia?

A

Eye works perfectly focusing on the focal spot of the retina.

61
Q

What is myopia?

A

If refractive power to high or eye to long focal point is to far forward- unfocused

62
Q

What is hyperopia?

A

To little focusing power focal spot brhind the retina so unfocused.

63
Q

What is the fovea?

A

Point of light collection and highest resolution.

64
Q

What does the retina form from?

A

It’s part of the CNS forming from the Diencephalon

65
Q

What are 5 neuronal types in vision?

A

Photoreceptors, bipolar cells, ganglion cells, Amacrine cells and horizontal cells.

66
Q

What happens to Photoreceptors in the light?

A

cGMP channels close yet potassium channels remain open leading to a state of hyper-polarisation.

67
Q

What happens to photoreceptors in the dark?

A

cGMP gated sodium and calcium channels remain open and potassium efflux channels remain open maintaining a standard potential.

68
Q

What is an Opsin?

A

A protein which forms part of the visual pigment rhodopsin. It’s a 7-transmembrane-GPCR.

69
Q

What is the mechanism of an opsin?

A

Light absorption causes a conformational change, which activates transducin. Transducin activates cGMP hydrolysis activates alpha subunit. Deactivating Ca2+ and Na+ channels cause hyperpolarisation

70
Q

How is phototransduction turned off?

A

When Calcium levels reach so low they prevent inhibition of rhodopsin kinase and gaunyly Cyclase.

71
Q

What does rhodopsin kinase do?

A

When active causes reassociation of the alpha subunit to transducin.

72
Q

What does granulate cyclase do?

A

Produces cGMP from GTP allows Na/Ca to flow into cel repolarising it

73
Q

What types of photoreceptors?

A

Rods and cones

74
Q

What is night blindness?

A

Loss of rod function

75
Q

What is being legally bind?

A

Loss of cone function

76
Q

What is trichromatic colour vision?

A

Blue,Red and Green

77
Q

What is the fovea?

A

Highest resolution, very high density of cones and no rods in fovea

78
Q

What do ganglion cells detect?

A

Luminance

79
Q

Retinal ganglion cells have two types what are they?

A

Off/on centre ganglion cells.

80
Q

What happens when light is on and off with ganglion cells?

A

When lights on, on centre turns on off centre off and vice versa after that.

81
Q

What neurotransmitters do photoreceptors release?

A

Glutamate

82
Q

What the effect of glutamate on on-centre bipolar cells?

A

They express mGluR6 receptor which causes depolarisation of other bipolar cells releasing more glutamate onto oncentre ganglion cells

83
Q

What happens when glutamate is released on offcentre bipolar cells?

A

Off centre Bipolar cells have AMPA Kainate receptors which when in contact with glutamate hyperpolarising releasing less neurotransmitters

84
Q

What do horizontal cells do?

A

Join to each other and to photoreceptors via gap junctions allowing them to detect background illumination

85
Q

How are horizontal cell stimulated?

A

Stimulated by the release of glutamate by photoreceptors. Horizontal cells then release GABA back causing hyper-polarisation of photoreceptors due to a general area

86
Q

Where do ganglion cells in the optic tract project to?

A

Pretectum
Superchiasmatic nucleus
Superior colliculus
Dorsal lateral geniculate nucleus

87
Q

What is the pretectum?

A

Area of brain that feeds back to constrictor muscles in the pupil

88
Q

What is the superchiasmatic nucleus?

A

Runs the circadian cycle

89
Q

What is the superior colliculus?

A

Area of the brain for the Coordination of movement in response to visual cues.

90
Q

What is the Dorsal lateral geniculate nucleus?

A

Relays to visual cortex

91
Q

What fibres connect the dLGN to visual cortex?

A

Superior retinal quadrants

92
Q

What is stereopsis?

A

Perception of depth produced by reception in the brain from both eyes in combination with varying dominance of each eye.

Neuroscience Semester 2 (7 decks)

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