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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
What is contact chemosensation?
Gustation
26
What are taste papillae?
Specialised invaginations on the tounge
27
What are the 4 types of papilla?
Filliform papilla Fungiform papilla Circumvallate Follate papilla
28
How many tasted buds of filliform papilla?
No taste buds
29
How many taste buds in fungiform papilla?
25% of all tastebuds (3 on each apical surface)
30
How many taste buds on circumvallate?
50% of taste buds 250 taste buds in each trench
31
How many taste buds does folate papilla have?
25% of tastebuds (parallel ridge with ~600 on the ridges)
32
Where are papilla postitioned?
Positioned in troughs when food is dissolved it accumulates in higher concentration in trough papilla are in- contain taste buds sensory cells
33
What are the 5 basic tastes?
``` Bitter ( caffeine, nicotine) Sour (Acid) Sweet (glucose) Salty (NaCl) Umami (meaty taste-glutamate) ```
34
What is the structure of a Taste bud?
Found in trough with pores on whic you find microvilli that increase surface area for taste receptors
35
Why is taste bud pore useful?
Further concentrates Ligands
36
What are the 2 domains of a taste bud?
Apical (external environment) | Basolateral (taste bud)
37
What receptors are on the apical surface of a taste bud?
Ion-channels (sweet/sour) | GPCRs (sweet,bitter&umami)
38
How are gustation neurones stimulated?
Via the release of ions through ion channels and use of cellular machinery to release neurotransmitters , through the basolateral surface
39
What cranial nerves transduce gustation impulses?
Facial nerve (7) Glossopharyngeal (9) Vagus (10)
40
What neurotransmitters are utilised in gustation?
Serotonin and ATP
41
What does salt tasting reception utilise?
Utilise an Amiloride sensitive Na+ channel. Cause direct depolarisation of the taste cell.
42
What does Acid tasting utilise?
H+ sensitive transient receptor potential (TRP) channel. Cause direct depolarisation of taste cell.
43
What GPCRs are utilised for sweet and umami tastes?
T1R family
44
How do T1Rs work during taste of sweet and umami?
They form Heterodimers, have many monomers with varying combinations to code for varying ligands- example different ones for sweet and umami.
45
What is the sweet heterodimer?
T1R-2, T1R-3
46
What does T1R-2, T1R-3 detect in gustation?
Sucrose,fructose,glucose and maltose
47
What is the mechanism of sweet signalling?
GPCR activates phospholipase Cbeta2, which cause calcium release of endoplasmic recticulum causing sodium release causing depolarisation.
48
What T1Rs does umami signalling utilise?
T1R-1/3
49
What is the bitter signalling pathway like?
Same as sweet but the alpha subunit is alpha gustducin
50
Where do the gustatory cranial nerves go to?
Solitary tract nucleus
51
What makes up the optic nerve?
Retinal ganglion axons
52
What is partial decussation at the optic chiasm?
This is where optic nerves cross from either eye. Contralateral side and ipsilateral side travel to opposite sides.
53
Where do retinal ganglion cells terminate?
Lateral geniculate nucleus
54
What are the 3 layers of the eye?
Sclera, choroid and retina
55
What is the fluid in the eye?
Vitreous humour
56
Where do you find the cornea and lens?
At the front of the eye
57
What’s the purpose of cornea and lens?
Cornea provides most refraction and lens provides fine tuning adjustable refraction
58
How do you focus further?
Ciliary muscles relax, ligaments tighten causing outwards pull- less refractive power.
59
How do you focus nearer?
Ciliary muscles contract ligaments relax lens relax thickening- focus near more refractive power.
60
What is emnotropia?
Eye works perfectly focusing on the focal spot of the retina.
61
What is myopia?
If refractive power to high or eye to long focal point is to far forward- unfocused
62
What is hyperopia?
To little focusing power focal spot brhind the retina so unfocused.
63
What is the fovea?
Point of light collection and highest resolution.
64
What does the retina form from?
It’s part of the CNS forming from the Diencephalon
65
What are 5 neuronal types in vision?
Photoreceptors, bipolar cells, ganglion cells, Amacrine cells and horizontal cells.
66
What happens to Photoreceptors in the light?
cGMP channels close yet potassium channels remain open leading to a state of hyper-polarisation.
67
What happens to photoreceptors in the dark?
cGMP gated sodium and calcium channels remain open and potassium efflux channels remain open maintaining a standard potential.
68
What is an Opsin?
A protein which forms part of the visual pigment rhodopsin. It’s a 7-transmembrane-GPCR.
69
What is the mechanism of an opsin?
Light absorption causes a conformational change, which activates transducin. Transducin activates cGMP hydrolysis activates alpha subunit. Deactivating Ca2+ and Na+ channels cause hyperpolarisation
70
How is phototransduction turned off?
When Calcium levels reach so low they prevent inhibition of rhodopsin kinase and gaunyly Cyclase.
71
What does rhodopsin kinase do?
When active causes reassociation of the alpha subunit to transducin.
72
What does granulate cyclase do?
Produces cGMP from GTP allows Na/Ca to flow into cel repolarising it
73
What types of photoreceptors?
Rods and cones
74
What is night blindness?
Loss of rod function
75
What is being legally bind?
Loss of cone function
76
What is trichromatic colour vision?
Blue,Red and Green
77
What is the fovea?
Highest resolution, very high density of cones and no rods in fovea
78
What do ganglion cells detect?
Luminance
79
Retinal ganglion cells have two types what are they?
Off/on centre ganglion cells.
80
What happens when light is on and off with ganglion cells?
When lights on, on centre turns on off centre off and vice versa after that.
81
What neurotransmitters do photoreceptors release?
Glutamate
82
What the effect of glutamate on on-centre bipolar cells?
They express mGluR6 receptor which causes depolarisation of other bipolar cells releasing more glutamate onto oncentre ganglion cells
83
What happens when glutamate is released on offcentre bipolar cells?
Off centre Bipolar cells have AMPA Kainate receptors which when in contact with glutamate hyperpolarising releasing less neurotransmitters
84
What do horizontal cells do?
Join to each other and to photoreceptors via gap junctions allowing them to detect background illumination
85
How are horizontal cell stimulated?
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
Where do ganglion cells in the optic tract project to?
Pretectum Superchiasmatic nucleus Superior colliculus Dorsal lateral geniculate nucleus
87
What is the pretectum?
Area of brain that feeds back to constrictor muscles in the pupil
88
What is the superchiasmatic nucleus?
Runs the circadian cycle
89
What is the superior colliculus?
Area of the brain for the Coordination of movement in response to visual cues.
90
What is the Dorsal lateral geniculate nucleus?
Relays to visual cortex
91
What fibres connect the dLGN to visual cortex?
Superior retinal quadrants
92
What is stereopsis?
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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