Nociceptors/Pain Flashcards Preview

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Flashcards in Nociceptors/Pain Deck (19):
1

Polynodal Nociceptors

C fibers respond to wide variety of intense mechanical stimuli, more responsible for diffuse/dull/aching/burning pain and delayed response

2

Adelta Fibers

Larger and faster conducting, responsible for immediate "ouch" to more limited range of stimuli

3

3 Kinds of Pain

Nociceptive
Neuropathic/genic
Psychogenic

4

5 Activations of Nociceptors

a) K+ depols nerve terminals direclty
b) H+ open acid sensing ion channels that lets Na enter
c) ATP activates P2X cation channel
d) Bradykinin stimulates GPCRs
e) Heat activates unique temp-dependent TRPV1 cation channels

5

Plasma Kininogen

Torn capillaries release, induces bradykinin synth

6

Hyperalgesia

Increased lingering pain from tenderness/inflammation of tissues

7

Axon Reflex

APs from Adelta and Cs branch in SC to activate neurons that send signals back out to periphery to release sensitizing substances like Substance P, NGF, 5HT, PGs, leukotrienes, CGRP, etc

8

Substance P

Released in periphery to sensitize nociceptor nerve endings and induce mast cells to release histamine

9

Resolvins

PG metabolites hours later that resolve rather than promote inflammation. Asprin promotes their synthesis so it acts as a double whammy

10

Projection Neurons

Receive pain in dorsal root from pain fibers and decussate/rise up spinothalamic tract

11

Anterolateral System (ALS)

Spinothalamic tract and its collaterals given off in brain stem

12

2 Parallel Pathways for Pain

Both synapse in dorsal column and rise up spinothalamic tract contra, but one goes through thalamus to appropriate sensory cortex w/ detailed pain discrimination info. Other sends axons to parabrachhial nucleus and reticular formation in pons/medulla/thalamus and appears to carry affective or motivational aspects of pain - doesn't even distinguish locations

13

Third Pain Pathway

Carries visceral pain and rises up ipsilateral dorsal column

14

Brown-Sequard Syndrome

Nerves damaged on one side of spinal cord, so you lose temp/pain from contra side and touch/proprio from ipsi

15

Gate Theory vs. Allodynia

Aalpha/beta touch Rs can stimulate inhibitory interneurons on pain projection neurons or stimulate actual projection neuron

16

Endogenous Opioids

Mainly Enkephalins and endorphins, peptide NTs that suppress ALS neurons at various points as pain neg feedback

17

Central Sensitization

Prolonged EPSPs from C fibers cause hyperalgesia or allodynia similar to learning/memory, where touch can cause pain. Can cause post-surgical problems

18

Mu-Opioid R

GPCR that opens K+ channels to hyperpolarize neuron. Stimulated by morphine

19

Neuropathic Pain

Damaged nervous tissue releases ATP which stimulates microglia. These produce BDNF which converts GABA signals from inh to excitatory, opening up pain pathways. Morphine stimulates these microglia somehow so it is bad for neuropathic pain