27: Abdominal/Visceral Pain - O'Connell Flashcards
nociceptive v. neuropathic pain
Nociceptive pains
Results from direct activation of nociceptors
Neuropathic pains
Results from direct injury to nerves in the peripheral or central nervous system
nociceptor receptor type
Receptor type – free nerve endings of primary sensory neurons with cell bodies in the dorsal root ganglia and the trigeminal ganglia.
Location: mainly found in skin, joints and muscle
Abdominal pain can be caused by problems in the abdominal wall or stimulation of parietal nociceptors in the peritoneal lining of the abdomen.
“Silent nociceptors” which only respond after tissue damage (or sensitization) are found in the viscera and also in the skin
Ischemia can result in pain via
the stimulation of acid-sensitive primary sensory nociceptors to the vasculature.
where does nociceptive information cross?
at level of spinal cord
anterolateral system
how might referred pain work?
convergence-projection theory
The basis for referred pain may be convergence of somatic and visceral pain fibers on the same second-order neurons in the dorsal horn of the spinal cord that project higher brain regions. The periaqueductal gray (PAG) is a part of a descending pathway that includes serotonergic neurons in the nucleus raphé magnus and catecholaminergic neurons in the rostral ventromedial medulla to modulate pain transmission by inhibition of primary afferent transmission in the dorsal horn
does some pain go up the dorsal column?
yes some visceral pain does go up ipsilateral dorsal column and crosses at medulla going to insular cortex
(anterolateral is the main tract for pain)
where does the neospinothalamic tract go? paleospinothalamic tract?
neo- somatosensory cortex via VPL - localilzation
paleo -limbic system - emotional
“wind up”
incoming pain signal releases substances, NMDA must be depolarized first before can be responsive to substances, wind up causes an amplification of the pain signal
define hyperalgesia
An increased response to a stimulus which is normally painful
Hyperalgesia is due to both peripheral and central sensitization.
define allodynia **
pain due to a stimulus which does not usually provoke pain
describe the gate-control theory
Stimulation of low threshold, large fiber A alpha and Abeta mechanoreceptor afferents can inhibit the transmission of nociceptive input from Adelta and C fiber afferents in the dorsal horn.
how do opiates work on pain pathway?
activation of opiod receptor decrease calcium influx in response to incoming action potential
this decrease release of excitatory Nt such as glutamate
