Pain Anatomy Flashcards
Nociceptive Pain
activation of peripheral nociceptors - from tissue damage
typically more sensitive to opioids
can be visceral (organs) or somatic (skin muscle tissue)
Visceral: migraine, ischemia, pancreatitis, peritoneal inflammation etc.
Somatic: tendons, bursa, ligaments
Neuropathic Pain
dysfunction or injury to the CNS or PNS.
better response to antidepressants or anticonvulsants
is chronic, burning, piercing
CNS: post-stroke, MS, spinal cord injury
PNS: diabetic neuropathy, postherpatic neuralgia, chemo pts etc.
A Delta Fibers
large 1-4mm diameter myelinated fast 5-10m/s sharp & localized immediate & transient
C Fibers
smaller unmyelinated slower 0.6-2m/s dull, ache, burn poor localization may be constant
Afferent Pathway
sensory: neurons send signals from periphery to CNS
PNS –> dorsal horn –> CNS
Efferent Pathway
motor: CNS–>dorsal root–>periphery
4 Phases of Nociception
- transduction - activation
- transmission - conduction along axons via 1,2,3 order neurons
- perception - limbic/reticular systems & cortex
- modulation - CNS response
dorsal horn anatomy
cell bodies of peripheral nerves located here
rexed laminae I-VI - receives afferent sensory input
I: marginal layer
II: substantia gelatinosa
II-IV: nucleus proprius
ventral horn
lamina VII-IX
lamina X
cluster of cells around the central canal
where do C afferent fibers terminate?
laminae I, II, & V
- sensory primarily in II
where do A delta fibers terminate?
laminae I, II, V, X
tract for ascending systems
anterolateral spinothalamic primarily
- anterior: pressure
- lateral: temp & pain
spinoreticular and spinomesencephalic also
Lissauers Tract
dividing point for A & C fibers into ascending & descending branches via the anterolateral spinothalamic tract
Drugs altering transduction
NSAIDs, antihistamines, local anesthetic ream, opioids, membrane stabilizers, serotonin antags
Drugs altering transmission
local anesthetics - peripheral nerve block - epidural
drugs altering perception
parenteral opioids
alpha 2 antagonists
GA
drugs altering modulation
spinal opioids
alpha 2 antagonists
NMDA antagonists
Spinothalamic Tract Neurons
1: arrives in dorsal horn via sensory nerves
2: decussates to anterolateral WHITE matter of cord - ascends to thalamus
3: projects to corresponding somatosensory area of cerebral cortex
Spinoreticular Tract
heightens level of arousal to pain - memory & emotion components
- terminates in the reticular formation
- has 4 order neurons
Gate Control Theory
pain is carried by small slow fibers
cells in the substantial gelatinous transmit impulses to the brain which can be modulated by C & A beta fibers.
with increased large fiber activity pain transmission can be inhibited - closes the gate to the small fibers.
Descending Inhibitory Pathways
areas: midbrain, medulla, spinal cord
NTs: serotonin, NE
Endogenous opioids: B-endorphins (mu) Dynorphins (kappa) Enkephalins (delta)
allodynia
sensation of pain from a stimulus that was not previously painful
