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Cellular And Molecular > Lecture 5 - Transduction At Nerve Endings > Flashcards

Lecture 5 - Transduction At Nerve Endings Flashcards

1
Q

Why is a nematode worm tethered?

A

So a mechanical probe can meet the nematode worm

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2
Q

What are C.elegans?

A

Transgenic that expresses a yellow fluorescent protein

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3
Q

What happens when the mechanical probe is applied?

A

It gives rise to mechanical stimulus on the worm

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4
Q

What is the ratio fluorescence indictive of?

A

What the calcium concentration there is in the neuron

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5
Q

What is role of mechanical stimuli?

A

Activating ion channels in the membrane that allows calcium across neuron membrane

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6
Q

What do humans have?

A

Homologous proteins

Genes that show substantial homologous with the genes in the c.elegans

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7
Q

What are mammalian equivalent of MEC4 and MEC2?

A

ASIC channels

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8
Q

Where are ASIC channels expressed?

A

Pain sensing neurons

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9
Q

What are the sensory modalities?

A 
Vision
Hearing/balance I.e. mechanoreceptors 
Taste I.e. chemoreception 
Olfaction I.e. chemoreception
Skin and other body surfaces
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10
Q

What are examples of other body surfaces?

A 
Light touch 
Vibration 
Warm/hot/cool/cold I.e. thermoreception
High-threshold mechanoreceptors/pain
Chemoreception/Pain
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11
Q

What are other sensory modalities?

A

High threshold mechanoreception in viscera (respond to distension)
Chemoreception in viscera (pain)
Chemoreception in circulation/brain e.g. carotid body, medulla surface
Proprioceptive input (mechanoreception) - muscle length/position/tension - tendon stretch

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12
Q

What are the elements required to transduce the world into nerve impulses?

A
  1. Light sensitivity
  2. Chemical sensitivity
  3. Mechanosensitivity
  4. Temperature sensitivity
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13
Q

Light sensitivity

A

Rods
Cones
Blue light sensitivity RGC

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14
Q

Chemical sensitivity

A

Odorant receptors
Taste
Pain

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15
Q

Mechanosensitivity

A

Touch
Pain
Joint position

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16
Q

Temperature sensitivity

A

Skin thermosensitivity

Pain

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17
Q

Where is the pacinian Corpuscle found?

A

Skin/membrane
Inside our abdomen
Myelinated axon
Signalling mechanical stimuli

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18
Q

What are the features of Pacinian Corpuscle?

A

lamellated
Fluid filled capsule
Expanded myelin

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19
Q

What is found inside the Pacinian Corpuscle?

A

Stretch of unmyelinated axon

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20
Q

What happens further along the nerve?

A

Myelination begins as the nerve fibre is coming towards the edge of lamellated structure

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21
Q

What is found outside the nerve fibre as it’s going towards the central nervous system?

A

Myelin

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22
Q

What is Crystal and probe?

A

A device that can change an electrical stimulus into a motion

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23
Q

What occurs when the crystal is activated?

A

Mechanical device can be used to press down on the Corpuscle

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24
Q

What is the role of micro-manipulator?

A

Holds the Corpuscle in position
Inactivate the first node of Ranvier by applying circumscribed pressure to damage the nerve and prevent it from signalling by applying pressure to the first node

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25
How were recordings made?
Ex vivo preparation from isolated Pacinian Corpuscle
26
What is rectangular displacement?
Shows when the pressure is applied to the Corpuscle
27
How can the potential difference be recorded?
Extracellularly because of the incorporation of oil into the preparation
28
What does the use of oil prevent?
Miniature ex vivo preparation from drying out
29
When a generator potential is seen?
When a maintained pressure is applied onto Corpuscle
30
What is a biological device very sensitive to?
Changes in pressure | Not sensitive to maintained pressure
31
What properties does the capsule have?
Very special visco elastic properties
32
What is Pacinian Corpuscle?
Vibration sensitive device
33
What is a decapsulated preparation?
Stripped off the lamellated structure over the Corpuscle
34
How do you achieve a prolonged response?
Change the properties of receptor | Take capsule off
35
What are the steps for a propagated action potential?
``` Stimulus (e.g. mechanical) Transduction Generator potential Activation of the first node Propagated action potential ```
36
What happens when a large current is applied?
can only recruit one AP
37
What happens when a long depolarising stimulus is applied?
The node is only generating a single action potential
38
What limits the response to one or two action potentials?
Adaption to the stimulus
39
What happens when long lasting currents applied to myelinated axons?
2 action potentials is achieved
40
What blocks K+ channels?
Tetroethanol amino ions
41
What is expressed at the node of Ranvier?
KV7
42
What is KV7?
Kinetically slow K+ channel
43
What is the result of application of TEA?
Convert accommodative nerve into a nerve that does not accommodate (continuously generate action potential)
44
What is accommodation?
Allows nerve to soak up excitatory stimuli | Nerve is not continuously excited
45
What are different categories ion channels expressed by sensory neurons ?
1. Voltage-gated 2. Ligand-gated 3. Temperature-gated 4. Mechanically-gated
46
Voltage-gated
Activation depends on changes in membrane potential [Nav channels]
47
Ligand-gated
Activation depends on binding of a chemical
48
Temperature-gated
Activation depends on fall or an increase in temperature
49
Mechanically-gated
Activation depends on membrane stretch
50
What can be done to cell bodies of small diameter axons?
Dissociated and maintained in culture
51
What underlies induction and propagation of action potentials?
Na+ channels
52
What is a stimulating probe?
A device that converts changes in electrical probe potential into mechanical movements
53
What can be seen in phase contrast?
Nucleus | Nucleolus of neuron
54
What does a sensory neuron have?
Sensory nerve ending in the body
55
What is low threshold mechanoreceptors?
Expressing channel that require less membrane stretch to get them to open
56
What does MEC channels get?
Mechanically-gated currents
57
What does membrane stretch do?
Activate channels that can generate an inward current which depolarise the neurons
58
What are TRP channel?
Transient receptor potential | Prototype is deficient in a Drosophila mutant
59
TRP channels
Group of ion channels located mostly on the plasma membrane of animal cell types
60
What does TRP channels mediate?
Variety of sensations Pain, hotness, warmth, coldness Different kind of tastes, pressure and vision
61
How are some TRP channels activated?
Molecules found in spices like garlic, chilli pepper, wasabi Others by: menthol, camphor, peppermint and cooling agents
62
What do some TRP channels act?
Sensors of osmotic pressure, volume, stretch and vibration
63
How are sensation of warmth brought about?
Interaction between keratinocytes in skin which releases ATP and ATP receptor sensory nerves (TRPV4 + TRPV3)
64
What an TRPV2 be gated by?
Noxious heat (temperature above 43)
65
What do TRP channels form?
homo/heteromultimers Polypeptide crosses the membrane 6 times Hairpin loop - lining the channel pore
66
What is TRPA1?
Sensitive to cold temperature (-10) + variety of chemical stimulators Garlic, cinnamon, noxious cold receptors
67
Where is TRPM8 present?
Skin and mouth and tongues and lips | Gated by cool temperatures
68
What is microneography?
Recording of the activity of single afferent in a mixed nerve in human Use sharp microelectrode and carefully position within a human peripheral nerve Damage some of the axons in nerve
69
What is a Peltier device?
Convert electrical signal (current) into a movement of heat | Creates a Temperature difference by transferring what between 2 electrical junctions
70
What does Menthol potentiate?
Cool responses known to be due to activation of TRPM8
71
Where is TRPV1 expressed?
small diameter neurons
72
What is in-Situ hybridisation?
mRNA is being expressed for TRPV1 in small diameter sensory neurons in DRG
73
What is Hyperalgesia?
Changes in membrane properties of a primary sensory neuron leading to an increase in responsivensss (hypersensitivity)

Cellular And Molecular (9 decks)

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