lecture 71 Flashcards
Li -- pathophysiology of pain
how is chronic pain defined?
pain that lasts over 3 months
can be nocicpetive, neuropathic, visceral, and mixed
what pain would be classified as nociceptive?
osteoarthritis
rheumatoid arthritis
osteosarcoma (skin/deep tissue)
what pain would be defined as central neuropathic pain?
post-stroke
MS
spinal cord injury
migraine
HIV-related neuropathic pain
what would be defined as peripheral neuropathic pain?
post-herpetic neuralgia
diabetic neuropathy
what are examples of visceral pain?
internal organ pain
pancreatitis
inflammatory bowel syndrome
what are examples of mixed pain?
lower back pain
cancer pain
fibromyalgia
what are the functions of pain?
act as a warning system to avoid injury
aid in repair (hypersensitivity)
maladaption
how would inflammatory pain present?
throbbing and pulsating
how would neuropathic pain present?
stabbing, shooting, burning, and tingling
how would visceral pain present?
squeezing
would pain be classified as an emotion?
yes, it can impact mood thus
what pain pathways are peripheral receptors and channels involved in?
temperature-sensitive
acid-sensitive
chemical irritant sensitive receptors
what is TRPV?
transient receptor potential cation channel vanniloid
functions to respond to heat
what is TRPM?
transient receptor potential cation channel melastatin
functions to respond to cold
what is the ASIC?
acid-sensing ion channel
activated by H+ to conduct sodium
what receptors are chemical-irritant sensitive?
histamine
bradykinin
what are the different type of pain fibers that transduce pain signals?
AB fibers
A-delta fibers
C-fibers
what are the characteristics of AB fibers?
non-noxious (touch/pressure)
innervate the skin
fast transduction (35-75 m/s)
what are the characteristics of A-delta fibers?
regulate pain and cold
myelinated
fast transduction (2-35 m/s)
role in first pain aka reflex arc, sharp, prickly
what are the characteristics of C fibers?
regulate pain, temperature, touch, pressure, and itch (polymodal)
unmyelinated
slow (0.5-2 m/s)
role in second pain aka dull, aching
what is the role of substance P?
heightens pain responding in the periphery via vasodilation, degranulation of mast cells, release of histamine, and inflammation/prostaglandins
how does peripheral sensitization carry out?
repeated stimuli and increased expression of pain receptors leads to reduced firing threshold
how does neuropathic pain sensitization play out?
increased AMPA/NMDA expression sensitivity –> spinal sensitization –> spontaneous afferent activity –> enhanced expression of sodium channel subtypes contributing to enhanced cellular excitability and generation of ectopic action potentials
what is a key characteristics of the descending pathway?
has high expression of opioid receptors
