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MS2 - Nervous System > Nociception > Flashcards

Nociception Flashcards

1
Q

The first synapse for vibratory neurons is ___________.

A

the caudal medulla

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2
Q

The first synapse for pain neurons is ____________.

A

the posteromarginal nucleus in the dorsal horn of the spinal cord

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3
Q

For the warm/cold receptors that are not painful, which are myelinated?

A

Alpha-delta (cool): lightly myelinated

C (warm): unmyelinated

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4
Q

Warm receptors increase their firing rate in response to ____________.

A

increases in temperature

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5
Q

Cool receptors increase their firing rate in response to ______________.

A

decreases in temperature

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6
Q

There are 10x as many __________ receptors as ________ receptors.

A

cool; warm

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7
Q

What is nociception?

A

Sense of pain

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8
Q

What molecule does the P2X receptor sense?

A

ATP – this is important because it acts as a sensor of cytolysis

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9
Q

Differentiate activators and sensitizers.

A

Activators bring a neuron to threshold and sensitizers make it easier for a neuron to get to threshold.

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10
Q

Some activators and sensitizers include _____________.

A

Activators: bradykinin, 5HT

Sensitizers: substance P, prostaglandins

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11
Q

Describe the triple response.

A

After an injury, you get (1) a red center and (2) an edematous wheal (from bradykinin released from tissue damage) as well as (3) a flare of pinkness around the edema due to C fibers releasing substance P.

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12
Q

Bradykinin is a _____________.

A

vasodilator and inducer of vascular permeability

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13
Q

What are flares around wounds?

A

Pink areas that radiate outward

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14
Q

What are the qualitative differences between first pain and second pain?

A

First: tolerable, well-localized
Second: horrible, not well-localized, aching/throbbing

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15
Q

__________ and __________ are products of sensitization.

A

Hyperalgesia and allodynia

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16
Q

NMDA receptors can functionally become AMPA receptors by __________.

A

phosphorylation (which is accomplished by neurokinase I)

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17
Q

What causes hyperalgesia after a surgery?

A

Phosphorylation of the NMDA receptors

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18
Q

What neurotransmitter activates the inhibitory interneuron?

A

Enkephalin

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19
Q

Activation of inhibitory interneurons does what to the pre- and postsynaptic neurons?

A

Pre: blocks calcium channels (which thence makes the neuron release fewer vesicles!)

Post: opens potassium channels, which hyperpolarizes the membrane (making the neuron require more vesicle to become activated)

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20
Q

Stimulation of the ____________ leads to widespread analgesia.

A

periacqueductal gray

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21
Q

Enkephalin is an ______________.

A

endogenous opiate

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22
Q

What is tabes dorsalis?

A

A condition of dorsal column degeneration (that is, degeneration of A-beta axons)

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23
Q

TENS stands for ___________.

A

transcutaneous electrical nerve stimulation

24
Q

The main mechanism of systemic opiates is _______________.

A

activation of the periacqueductal gray area – there are “lots of” opiate receptors in the PAG – leading to widespread analgesia

25
Q

What is the principle of giving opiates in the spine (either epidural or intrathecal [which is subarachnoid])?

A

The inhibitory interneurons are in the spine; thus, giving opiates here leads to activation of the inhibitory neurons while avoiding the systemic side effects.

26
Q

The cannabinoid receptors have been shown to interact with two systems: ________________.

A

1) opiate system
2) immune system:
- decreasing proinflammatory cytokines
- increasing anti-inflammatory cytokines

27
Q

Fascinatingly, the placebo effect has been shown to be blocked by _____________.

A

naloxone; this is taken as evidence that the placebo effect relies on endogenous opiates (i.e., the frontal cortex – most likely –has a connection to the periacqueductal gray matter)

28
Q

Define neuropathic pain.

A

(n.) a state in which one experiences debilitating pain in the absence of external stimuli

29
Q

There are two rare disorders that lead to extreme pain states. What are they and what causes the disorder?

A

Primary erythralgia (PE) and paroxysmal extreme pain disorder (PEPD)

Both are due to gain-of-function mutations in sodium channels, making them hyperactive.

30
Q

True or false: a child who bites their lips or tongue to the point of mutilation likely has a condition caused by a gain-of-function mutation.

A

False

This is a classic sign of CID (congenital ionchannelopathy disorder) – a syndrome in which a loss-of-function mutation in pain-sensing sodium channels leads to decreased ability to sense pain.

31
Q

What temperature ranges are encompassed by “cool” and “warm” receptors?

A

Cool: 10 - 37
Warm: 30 - 48

32
Q

While warm and cool receptors are best at detecting changes in temperature, they can also ____________.

A

detect absolute temperature (with cool receptors firing more frequently at lower temperatures)

33
Q

Cool receptors are found on ________ fibers, while warm receptors are found on _______ fibers.

A

A-delta; C

34
Q

We’ve previously learned that the spinothalamic tract synapses on the VPL in the thalamus. To what other sites does the anterolateral system synapse?

A

The reticular formation (which thence goes to the hypothalamus) in the brainstem and the mesencephalon (aka midbrain, aka periacqueductal gray matter)

35
Q

The cingulate gyrus also activates in response to painful stimuli and is thought to play a role in the _________ response to pain.

A

emotional (because the cingulate gyrus is part of the limbic system)

36
Q

Where do painful sensations in the face/head synapse?

A

In the spinal trigeminal nucleus

37
Q

On which axons do hot (greater than 43 degrees C) stimuli travel?

A

A-delta (think of Dairy queen: Cool treats, Hot eats)

38
Q

Noxiously cold stimuli travel on ________ fibers.

A

C

39
Q

Intense pressure stimuli travel on _________ fibers.

A

A-delta

40
Q

What kind of fibers are polymodal fibers? What information do they transduce?

A

C fibers; mechanical and chemical pain (chemical pain includes moieties like capsaicin and acid)

41
Q

VR-1 is activated by ______________.

A

heat and capsaicin

42
Q

True or false: C fibers conduct faster than A-delta.

A

False (A-delta are myelinated and conduct faster)

43
Q

What is the fiber basis of the first-localized-then-diffuse pain?

A

A-delta are finely localized and arrive first, then C fibers – which are diffusely spread – arrive later

44
Q

The first fibers to be blocked by anoxia are _____________.

A

the more metabolically active A-beta and A-delta

45
Q

Bradykinin is produced by cleavage of ___________.

A

kininogen

46
Q

What is the cellular basis of referred pain?

A

Visceral-organ-pain neurons synapse on the same dorsal-horn neurons as external pain, and thus internal pain manifests as diffuse, C-fiber-like pain from a limb or external feature.

47
Q

The primary neurotransmitter used at the first synapse (in the dorsal horn) is __________, which activates these channels:

A

glutamate; AMPA and NMDA

48
Q

What is the receptor mechanism of substance P?

A

It binds to the neurokinin 1 receptor and causes potassium channels to close, thus depolarizing the cell. This allows glutamate to activate NMDA channels.

49
Q

Why does CNS substance P lead to long-term sensitization?

A

Because it is not efficiently removed from the extracellular environment

50
Q

Inhibitory interneurons stem from ______ fibers.

A

A-beta

51
Q

What is the pathophysiology of tabes dorsalis?

A

Advanced syphilis leads to the destruction of A-beta fibers and consequent hyperalgesia

52
Q

True or false: stimulation of top-down analgesia leads to action potentials in the nucleus raphe magnus in the medulla.

A

True! This is the pathway of the periacqueductal gray matter

53
Q

Neurons from the nucleus raphe magnus are activated by ___________ and synapse on __________ that use enkephalin.

A

serotonin; inhibitory interneurons

54
Q

Why are opiates sometimes given intrathecally?

A

Because they block transmission of pain signals in the spinal cord without systemic effects

55
Q

What is the dominant theory behind the stress-induced analgesia phenomenon?

A

That the limbic system (cingulate gyrus) stimulates the PAG

56
Q

When C fibers are killed and A-beta afferents sprout to make new connections, __________ results.

A

allodynia

MS2 - Nervous System (111 decks)

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