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Investigation Of Human Disease > channelopathies 2 > Flashcards

channelopathies 2 Flashcards

1
Q

Describe pain according to the content.

A

Pain is described as an unpleasant sensory and emotional experience linked to actual or potential tissue damage, serving as a protective response.

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2
Q

What are the two types of pain mentioned in the content?

A

The two types of pain mentioned are hyperalgesia and allodynia.

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3
Q

What is hyperalgesia in the context of pain?

A

Hyperalgesia refers to an increased sensitivity to pain, often observed in chronic conditions.

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4
Q

Explain allodynia as discussed in the content.

A

Allodynia is when pain is experienced in response to a stimulus that would not typically provoke pain.

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5
Q

How does pain serve as a physical process according to the content?

A

Pain functions as a physical process that aims to minimize contact with the injury and triggers protective responses like reflex withdrawal and behavioral changes to avoid further pain.

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6
Q

Describe the different subpopulations of nociceptive neurons based on size and conduction velocity.

A

Aβ fibers are fast, large, myelinated neurons. Ad fibers are fast, small, thinly myelinated neurons. C fibers are slow, small, unmyelinated neurons.

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7
Q

What is the role of primary afferent fibers (PAF) in sensing pain?

A

PAF, also known as nociceptive neurons or sensory neurons, carry inflammation signals to the Central Nervous System (CNS) to sense pain.

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8
Q

How are Aβ fibers characterized in terms of action potential speed and neuron size?

A

Aβ fibers are fast-conducting neurons with an action potential speed of over 100 m/s and are the largest neurons, over 40 mm in size.

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9
Q

Define Dorsal Root Ganglion (DRG) and its significance in pain sensation.

A

DRG is where the cell bodies of nociceptive neurons are located, playing a crucial role in transmitting pain signals from the periphery to the CNS.

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10
Q

How do Ad fibers differ from Aβ fibers in terms of action potential speed and myelination?

A

Ad fibers are fast-conducting neurons with an action potential speed of 30 m/s, smaller in size (20 mm), and thinly myelinated.

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11
Q

What are the characteristics of C fibers in terms of action potential speed, neuron size, and myelination?

A

C fibers are slow-conducting neurons with an action potential speed of less than 1 m/s, small in size (less than 5 mm), and unmyelinated.

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12
Q

How can Ad fibers be distinguished from Aβ fibers based on their response to pressure?

A

Ad fibers are blocked by pressure, leading to a tingly sensation, unlike Aβ fibers.

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13
Q

Explain how C fibers can be blocked using low-dose anaesthetic.

A

C fibers, being unmyelinated, can be blocked by low-dose anaesthetic, effectively reducing pain signals transmission.

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14
Q

Describe P2X receptors in the human body.

A

P2X receptors in the human body range from P2X1 to P2X7.

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15
Q

What is the role of ligand-gated, non-selective cation channels?

A

They are activated by extracellular ATP and play a role in responding to noxious stimuli.

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16
Q

How does neuropathic pain differ from acute pain?

A

Neuropic pain lacks defensive or behavioral purposes, is chronic, and arises from nerve damage.

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17
Q

Define allodynia and hyperalgesia in the context of neuropathic pain.

A

Allodynia is pain from stimuli that don’t normally cause pain, while hyperalgesia is an increased sensitivity to pain.

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18
Q

What are microglia and how are they related to neuropathic pain?

A

Microglia are immune cells in the central nervous system that play a key role in mediating neuropathic pain.

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19
Q

Do P2X receptors play a role in channelopathies and neuropathic pain?

A

Yes, P2X receptors are involved in channelopathies and neuropathic pain.

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20
Q

Describe how sciatica is related to neuropathic pain.

A

Sciatica is a chronic condition caused by nerve damage that leads to further pain in different areas of the body.

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21
Q

Describe microglia in the CNS.

A

Microglia are resident inflammatory cells in the CNS isolated by the BBB.

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22
Q

What receptors do microglia express?

A

Microglia express P2X4 and P2X7 receptors.

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23
Q

What happens to microglia in response to damage in the CNS?

A

Microglia are activated, move to the injury site, and produce inflammatory molecules.

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24
Q

Explain the role of cellular signaling between neurons and microglia in neuropathic pain.

A

Cellular signaling between neurons and microglia is critical to establish and maintain neuropathic pain.

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25
Q

Describe the role of spinal microglia in neuropathic pain.

A

Spinal microglia express P2X4 receptors which, when activated by neuron-derived ATP, trigger the vesicular secretion of brain-derived neurotrophic factor (BDNF in channelopathies neuropathic pain.

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26
Q

How is pain perceived in the body through excitatory and inhibitory synapses?

A

Pain perception involves sensory neurons releasing glutamate at excitatory synapses and inhibitory interneurons releasing GABA at inhibitory synapses, where GABA receptors are activated causing hyperpolarization by allowing Cl- ions to permeate.

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27
Q

Define channelopathies in the context of neuropathic pain.

A

Channelopathies refer to diseases or disorders caused by dysfunction in ion channels, potentially leading to abnormal pain perception and signaling in conditions like neuropathic pain.

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28
Q

What is the role of neuron-derived ATP in activating P2X4 receptors in the context of neuropathic pain?

A

Neuron-derived ATP activates P2X4 receptors on spinal microglia, triggering the release of brain-derived neurotrophic factor (BDNF) in channelopathies and neuropathic pain.

29
Q

How does the balance between excitation and inhibition relate to the perception of pain?

A

If excitation surpasses inhibition in the nervous system, it can lead to the sensation of pain, highlighting the importance of maintaining a balance between excitatory and inhibitory signals in pain perception.

30
Q

Describe the mechanism by which GABA contributes to pain perception through ligand-gated ion channels.

A

GABA acts on ligand-gated ion channels, allowing Cl- ions to permeate and causing hyperpolarization, which plays a crucial role in inhibiting neuronal excitation and modulating pain perception.

31
Q

How does the activation of P2X4 receptors on spinal microglia contribute to neuropathic pain?

A

Activation of P2X4 receptors by neuron-derived ATP in spinal microglia leads to the release of brain-derived neurotrophic factor (BDNF), which is implicated in the pathophysiology of neuropathic pain.

32
Q

Explain the significance of brain-derived neurotrophic factor (BDNF) secretion in the context of channelopathies and neuropathic pain.

A

The vesicular secretion of BDNF triggered by the activation of P2X4 receptors on spinal microglia plays a crucial role in channelopathies and neuropathic pain by influencing neuronal plasticity and pain signaling.

33
Q

How can an imbalance between excitation and inhibition in the nervous system lead to the sensation of pain?

A

When excitation surpasses inhibition, it can disrupt the normal processing of pain signals, potentially leading to the perception of pain due to altered neuronal activity.

34
Q

What is the role of P2X4 receptors in the context of neuropathic pain and channelopathies?

A

P2X4 receptors on spinal microglia are activated by neuron-derived ATP, triggering the release of brain-derived neurotrophic factor (BDNF) and contributing to the pathophysiology of neuropathic pain in channelopathies.

35
Q

Describe the development of neuropathic pain.

A

Neuropic pain is developed when inhibitory synapses are disrupted due to changes in Cl- balance inside/outside neurons, leading to constant excitatory synapses and action potential firing.

36
Q

What happens to GABA receptors in patients with chronic pain?

A

Patients with chronic pain express a truncated version of a receptor that alters Cl- balance, affecting GABA receptors.

37
Q

How does GABA affect the membrane in neuropathic pain development?

A

GABA depolarizes the membrane instead of hyperpolarizing it, leading to disrupted inhibitory synapses.

38
Q

Define the role of cation channels in neuropathic pain.

A

Changes in Cl- balance lead to the activation of other cation channels, contributing to the development of neuropathic pain.

39
Q

What is the consequence of disrupted inhibitory synapses in neuropathic pain?

A

Disrupted inhibitory synapses result in constant excitatory synapses and action potential firing, leading to chronic pain.

40
Q

Describe the role of Na+ ion channels in neuropathic pain.

A

Na+ ion channels play a crucial role in neuropathic pain by modulating sodium currents involved in pain perception and transmission.

41
Q

What are μ-Conotoxins and how do they affect sodium currents?

A

μ-Conotoxins are substances that modulate sodium currents, particularly in the context of pain perception and transmission, offering therapeutic potential.

42
Q

How do mutations in Na+ ion channel genes contribute to pain syndromes?

A

Mutations in Na+ ion channel genes, such as Nav1.7, Nav1.8, and Nav1.9, can lead to the development of pain syndromes by altering the function of these channels.

43
Q

Do Na+ ion channels show preferential expression in specific neurons related to pain perception?

A

Yes, Na+ ion channels like Nav1.7, Nav1.8, and Nav1.9 are preferentially expressed within dorsal root ganglion neurons, which are involved in pain perception.

44
Q

Describe the Nav1.7 channel.

A

Nav1.7 is encoded by the gene SCN9A and is preferentially expressed within dorsal root ganglion neurons.

45
Q

What is the impact of gain-of-function mutations in Nav1.7?

A

Gain-of-function mutations lead to persistent ion current.

46
Q

Explain the effect of loss-of-function mutations in Nav1.7.

A

Loss-of-function mutations result in insensitivity to pain.

47
Q

What type of stimuli does Nav1.7 amplify in its closed-state near resting potential?

A

Nav1.7 amplifies small, subthreshold depolarizing stimuli.

48
Q

What kind of pain is associated with Nav1.7 gain-of-function mutations triggered by mild warmth?

A

Severe burning pain in the extremities.

49
Q

What was the focus of the study by McDermott et al. in 2019 regarding Nav1.7?

A

Defining the Functional Role of NaV1.7 in Human Nociception.

50
Q

Describe the pain disorder linked to Nav1.7 mutations characterized by severe perineal, ocular, and perimandibular pain.

A

Extreme pain disorder with episodes of severe pain in specific areas.

51
Q

Describe Erythromelalgia.

A

Episodes of redness, swelling, and pain, particularly in limbs.

52
Q

What is a characteristic of Nav 1.7 in Erythromelalgia?

A

It opens easily and stays open for long periods.

53
Q

Explain the extreme pain disorder associated with Nav 1.7.

A

Pain attacks accompanied by skin flushing, changes in breathing, and heart pace.

54
Q

How does Nav 1.7 contribute to constant pain attacks in extreme pain disorder?

A

It can close but not fully, allowing Na+ ions to still depolarize the membrane.

55
Q

Define small fiber neuropathy.

A

A condition characterized by pain attacks and the inability to distinguish between hot and cold temperatures.

56
Q

What happens to neurons over time in small fiber neuropathy?

A

They degenerate due to the constant firing of action potentials.

57
Q

What is the focus of the study ‘Defining the Functional Role of NaV1.7 in Human Nociception’ by McDermott et al?

A

Understanding the role of Nav 1.7 in human pain perception.

58
Q

Describe GEFS+ in terms of the epilepsy phenotypes exhibited by individuals.

A

Individuals with GEFS+ exhibit numerous epilepsy phenotypes.

59
Q

What type of syndrome is GEFS+ in terms of inheritance?

A

GEFS+ is an autosomal dominant syndrome.

60
Q

What are the three voltage-gated sodium channel genes associated with mutations in GEFS+?

A

SCN1B, SCN1A, SCN2A are the three genes associated with mutations in GEFS+.

61
Q

How long can the disease persist in individuals with GEFS+?

A

The disease can persist beyond early childhood in individuals with GEFS+.

62
Q

Define Channelopathies in the context of GEFS+.

A

Channelopathies refer to diseases caused by dysfunction of ion channels, as seen in GEFS+.

63
Q

What is the relationship between GEFS+ and neuropathic pain?

A

GEFS+ is associated with neuropathic pain.

64
Q

What type of seizures are commonly seen in patients with GEFS+?

A

Patients with GEFS+ exhibit severe febrile seizures.

65
Q

What has been discovered in patients affected by inherited epilepsy syndromes related to febrile seizures?

A

Mutations in voltage-gated sodium channel genes have been discovered in patients affected by inherited epilepsy syndromes related to febrile seizures.

66
Q

Describe the impact of the R1648H mutation on SCN1A channels.

A

The R1648H mutation in SCN1A results in the substitution of a positively charged arginine residue with a histidine residue in the voltage sensor domain (S4), leading to increased sodium current size compared to wild-type channels.

67
Q

What type of mutation is the R1648H mutation in SCN1A?

A

The R1648H mutation is an example of a Gain of Function Mutation, making the channels hyper-active.

68
Q

What is the consequence of the R1648H mutation on SCN1A channels in terms of persistent current?

A

The R1648H mutation causes the channels to be persistently open, allowing Na+ to flow unperturbed, resulting in persistent firing of action potentials.

69
Q

How does the R1648H mutation in SCN1A affect neurons?

A

The R1648H mutation makes neurons hyper-excitable, leading to persistent firing of action potentials and potentially causing seizures.

Investigation Of Human Disease (19 decks)

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