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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
Q

How were recordings made?

A

Ex vivo preparation from isolated Pacinian Corpuscle

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26
Q

What is rectangular displacement?

A

Shows when the pressure is applied to the Corpuscle

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27
Q

How can the potential difference be recorded?

A

Extracellularly because of the incorporation of oil into the preparation

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28
Q

What does the use of oil prevent?

A

Miniature ex vivo preparation from drying out

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29
Q

When a generator potential is seen?

A

When a maintained pressure is applied onto Corpuscle

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30
Q

What is a biological device very sensitive to?

A

Changes in pressure

Not sensitive to maintained pressure

31
Q

What properties does the capsule have?

A

Very special visco elastic properties

32
Q

What is Pacinian Corpuscle?

A

Vibration sensitive device

33
Q

What is a decapsulated preparation?

A

Stripped off the lamellated structure over the Corpuscle

34
Q

How do you achieve a prolonged response?

A

Change the properties of receptor

Take capsule off

35
Q

What are the steps for a propagated action potential?

A 
Stimulus (e.g. mechanical)
Transduction 
Generator potential 
Activation of the first node 
Propagated action potential
36
Q

What happens when a large current is applied?

A

can only recruit one AP

37
Q

What happens when a long depolarising stimulus is applied?

A

The node is only generating a single action potential

38
Q

What limits the response to one or two action potentials?

A

Adaption to the stimulus

39
Q

What happens when long lasting currents applied to myelinated axons?

A

2 action potentials is achieved

40
Q

What blocks K+ channels?

A

Tetroethanol amino ions

41
Q

What is expressed at the node of Ranvier?

A

KV7

42
Q

What is KV7?

A

Kinetically slow K+ channel

43
Q

What is the result of application of TEA?

A

Convert accommodative nerve into a nerve that does not accommodate (continuously generate action potential)

44
Q

What is accommodation?

A

Allows nerve to soak up excitatory stimuli

Nerve is not continuously excited

45
Q

What are different categories ion channels expressed by sensory neurons ?

A
  1. Voltage-gated
  2. Ligand-gated
  3. Temperature-gated
  4. Mechanically-gated
46
Q

Voltage-gated

A

Activation depends on changes in membrane potential [Nav channels]

47
Q

Ligand-gated

A

Activation depends on binding of a chemical

48
Q

Temperature-gated

A

Activation depends on fall or an increase in temperature

49
Q

Mechanically-gated

A

Activation depends on membrane stretch

50
Q

What can be done to cell bodies of small diameter axons?

A

Dissociated and maintained in culture

51
Q

What underlies induction and propagation of action potentials?

A

Na+ channels

52
Q

What is a stimulating probe?

A

A device that converts changes in electrical probe potential into mechanical movements

53
Q

What can be seen in phase contrast?

A

Nucleus

Nucleolus of neuron

54
Q

What does a sensory neuron have?

A

Sensory nerve ending in the body

55
Q

What is low threshold mechanoreceptors?

A

Expressing channel that require less membrane stretch to get them to open

56
Q

What does MEC channels get?

A

Mechanically-gated currents

57
Q

What does membrane stretch do?

A

Activate channels that can generate an inward current which depolarise the neurons

58
Q

What are TRP channel?

A

Transient receptor potential

Prototype is deficient in a Drosophila mutant

59
Q

TRP channels

A

Group of ion channels located mostly on the plasma membrane of animal cell types

60
Q

What does TRP channels mediate?

A

Variety of sensations
Pain, hotness, warmth, coldness
Different kind of tastes, pressure and vision

61
Q

How are some TRP channels activated?

A

Molecules found in spices like garlic, chilli pepper, wasabi
Others by: menthol, camphor, peppermint and cooling agents

62
Q

What do some TRP channels act?

A

Sensors of osmotic pressure, volume, stretch and vibration

63
Q

How are sensation of warmth brought about?

A

Interaction between keratinocytes in skin which releases ATP and ATP receptor sensory nerves (TRPV4 + TRPV3)

64
Q

What an TRPV2 be gated by?

A

Noxious heat (temperature above 43)

65
Q

What do TRP channels form?

A

homo/heteromultimers
Polypeptide crosses the membrane 6 times
Hairpin loop - lining the channel pore

66
Q

What is TRPA1?

A

Sensitive to cold temperature (-10) + variety of chemical stimulators
Garlic, cinnamon, noxious cold receptors

67
Q

Where is TRPM8 present?

A

Skin and mouth and tongues and lips

Gated by cool temperatures

68
Q

What is microneography?

A

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
Q

What is a Peltier device?

A

Convert electrical signal (current) into a movement of heat

Creates a Temperature difference by transferring what between 2 electrical junctions

70
Q

What does Menthol potentiate?

A

Cool responses known to be due to activation of TRPM8

71
Q

Where is TRPV1 expressed?

A

small diameter neurons

72
Q

What is in-Situ hybridisation?

A

mRNA is being expressed for TRPV1 in small diameter sensory neurons in DRG

73
Q

What is Hyperalgesia?

A

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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