Peripheral Pain Flashcards
What kind of neurons are nocicpetors?
pseudounipolar
remak bundle
one schwann cell that can ensheath multiple axons, but myelinates only one axon segment
What do the following connective tissue layers in a nerve surround:
- endoneurium
- perineurium
- epineurium
- endoneurium: surrounds axons
- perineurium: surrounds axon fascicles
- epineurium: surrounds entire nerve
What kind of nerves are spinal ganglia associated with?
spinal and cranial nerves
What kind of nerves are associated with autonomic ganglia?
sympathetic and parasympathetic nerves
What kind of neurons do spinal ganglia contain? autonomic ganglia?
- spinal ganglia: large pseudounipolar sensory neurons
- autonomic ganglia: multipolar neurons
Do synapses occur at spinal ganglia or autonomic ganglia?
autonomic ganglia
Arrange the following from most to least myelinated:
- C
- Abeta
- Aalpha
- Adelta
Aalpha > Abeta > Adelta > C
What are Aalpha fibers responsible for?
proprioceptors of skeletal muscle
What are Abeta fibers responsible for?
mechanoreceptors in skin
What are Adelta fibers responsible for?
sharp and immediate pain and temperature
What are C fibers responsible for?
dull and achey temperature, pain, and itch
Classify the Adelta and C nociceptors based on conduction velocity.
- Adelta: first, sharp pain
- C: second, prolonged and diffused pain; result from acute damage
What do merkel receptors respond best to?
steady pressur from small objects
What do Meissner corpuscles respond best to?
rubbing against skin
What do Ruffini cylinders respond best to?
steady pressure and stretching of the skin (e.g. joint movement)
What do Pacinian corpuscles respond best to?
changing stimulation
What causes nociceptive pain? Examples?
- tissue damage
- burns, fractures, lacerations
What causes inflammatory pain? Examples?
- inflammation initiated by autoimmune response
- gout, rheumatoid arthritis
What causes neuropathic pain? Examples?
- nerve damage/somatosensory system
- diabetic neuropathy, carpal tunnel syndrome, complex regional pain syndrome
What causes nociplastic pain?
- no clear evidence of tissue damage
- fibromyalgia, chronic lower back pain, IBS
Which organ does not have nociceptors?
brain
Can you still feel second pain if first pain is blocked?
yes
What kind of channels are associated with nociceptors? What kind of stimulus activates these channels?
transient receptor potential (TRP) channels; activated by heat
Where do C fiber afferents synapse with 2nd order neurons?
dorsal horn of spinal cord; rexed’s laminae 1 and 2
Where do Adelta fiber afferents synapse with 2nd order neurons?
dorsal horn of spinal cord; rexed’s laminae 1 and 5
What type of information is transmitted in the anterolateral (spinothalamic) pathway? Dorsal Column Medial Lemnisus pathway?
- anterolateral = pain and temperature
- DCML = sensation, vibration, proprioception
first order neuron path of the anterolateral path? DCML path?
- anterolaterl: nociceptor –> dorsal horn
- DCML: receptor –> dorsal column –> medulla
second order neuron path of the spinothalamic path? DCML path?
- spinothalamic: dorsal horn –> VPL nucleus of thalamus
- DCML: medulla –> thalamus
third order neuron path of the spinothalamic path? DCML path?
- spinothalamic: thalamus –> somatic sensory cortex
- DCML: thalamus –> somatic sensory cortex
Site of decussation in the spinothalamic path? DCML path?
- spinothalamic: cord
- DCML: medulla
In brown sequard syndrome, injury to the left hemi-cord causes?
- loss of pain/temperature on RIGHT side below lesion (spinothalamic)
- loss of touch, vibration, proprioception on LEFT side below lesion (DCML)
What system manages spinal pain suppression (i.e. peripheral)?
gate control hypothesis
What systems manage supraspinal pain suppression (i.e. from the brain/CNS)?
- descending serotonergic and opioid inhibitory system
- descending purinergic inhibitory system
- descending adrenergic inhibitory system
Describe the gate control hypothesis. What is the theory? Which order neuron does it act on?
theory: mechanoreceptors (pressure) blocks peripheral ascending pain; act on 2nd order neurons
1) Abeta fiber synapses on inhibitory interneuron
2) inhibitory interneuron synapses on C-fiber
3) decreased C fiber firing
Describe descending control of central pain. Which order neuron does it act on?
act on 1st order neurons
1) PAG release enkephalin to Raphe nucleus
2) raphe nucelus release 5-HT to inhibit C fiber from releasing Sub-P
3) decreased C fiber firing in the dorsal horn
What is chronic pain?
pain that persists past normal healing time (>3-6 months)
hyperalgesia?
increased pain sensation to normally painful stimulus
hyperesthesia?
increased sensitivity to stimulation (e.g. irritation)
allodynia
perception of pain from non-noxious stimulus (e.g. tight clothes on sunburn)
dysesthesia
unpleasant abnormal sensation (e.g. feel sick)
Describe peripheral sensitization.
inflammatory substances sensitize/activate nociceptors
Describe central sensitization.
transcription dependent and transcription independent
