Pain patho Flashcards
Chronic pain
-lasts > 3 months
-nocicpetive (somatic)*
-neuropathic
-visceral*
-mixed
*inflammatory
Referred pain
-pain not in same place as injury
Neuropathic pain
-stabbing, shooting, burning
Visceral pain
-squeezing
Pain is an:
-emotion
-impacts mood
Pain transmission
-activation of peripheral nervous system
-transmission to spinal cord
-activate CNS at spinal cord
-input
-transmisson of pain signal to brain by nociception-inhibiting neurons
-modulation
-back down spinal cord to periphery
Temp sensitive peripheral receptors
-Transient receptor potential cation channel (TRP)
-TRPV (vanniloid) = heat
-TRPM (melastatin) = cold
Acid sensitive peripheral receptors
-Acid Sensing ion channel (ASIC)
-activated by H+
-conduct Na+
Chemical irritant sensitive peripheral receptors
-histamine
-bradykinin
Reflex upon painful stimuli
-from skin up the AFFerent nerve
-up EFFerent nerve from spinal cord to muscle
Slide 11
slide 11
Pain fibers
-AB-finbers
-Aδ-fibers
-C-fibers
AB-fibers
-non-noxious
-touch, pressure
-innervate the skin
-fastest
Aδ-fibers
-pain, cold
-myelinated
-fast
-“first pain”, reflex arc (sharp, prickly)
C-fibers
-pain, temp, touch, pressure, itch
-unmyelinated
-slow
-“second pain” (dull, aching)
Peripheral sensitization
-repeated stimuli reduces firing threshold
-substance P
-inc expression of pain receptors = sensitization
Substance P
-vasodilation
-degranulation of mast cells
-release histamine
-inflammation and prostaglandins
Neuropathic pain sensitzation
-inc AMPA and NMDA expression and sensitivity
-neucleotides CGRP
-substance P
-spontaneous afferent activity possibly enhanced expression of Na channel subtypes contributing to enhances cellular excitability and generation of ectopic action potentials
Pain circutry in brain
-high expression of opioid receptors in brain stem along descending pathway
-brain: mood, sedation, reduce emotional reaction
-brainstem: inc activity of descending fibers
-spinal cord: inhibit vesicle release and hyperpolarize post-synaptic membrane
-periphery: reduce activation of primary afferent and modulate immune activity
-are these all opiod effects or pain?
Somatosensory cortex
-registers which body part is in pain
-less activity here when pt distracts self from pain
Amygdala
-anticipates pain and reacts to threats
Prefrontal cortex
-fight response
-active when trying to reduce pain
Right lateral orbitofrontal cortex
-flight
-evaluates stimuli and decides response
