Pain+Pathways

=Goals=

1. Know characteristics of nociceptsr: high-threshold mechanoreceptors, mechanothermal noiceptors, molymodal, and free nerve endings)
==2. Know the Paleospinothalamic vs neospinothalamic pain pathways--

6. Approach to pain management: Escalating anagesics, antiepileptic drugs, TCAs, non-pharmacological means
=Ascending pain pathways= > ==Fast vs Slow== Fiber Types:
 * Small, unmyelinated: (Adelta): 5-30 m/s
 * Unmyelinated (C) 0.5-2m/s

Stimulus Selectivities
 * High-threshold Mechanoreceptors (Adelta)
 * Mechanothermal (Adelta)
 * Polymodal mechanical, thermal, chemical (C)

"Fast Pain"
 * Adfelta: High threshold mechanoreceptors & mechanothermal
 * stimulus differentiated, localized
 * //"Neospinalthalamic tract"//

"Slow Pain"
 * C, polymodal
 * Dull, burning, aching; less well localized
 * //"Paleospinothalamic tract"//

Adelta Fibers
 * Glutamate neurotransmitter
 * Terminate in laminae I and V

C fibers
 * Glutamate, pllus neuropeptides, especially Substance P
 * Terminate in Lamina II (cutaneous nociceptors)
 * Terminate in laminae I and V (visceral nociceptors)

Substance P: RPKPQQFFGLM-NH2

at first synapse, enkephalin (endogenous opioid) can modulate activity

Paleospinothalamic Tract > brainstem reticular formation bilatterally > intralaminar and midline thalamic nuclei > parietal, frontal, and limbic regions difusely
 * Difuse, polysunaptic connections in cord gray matter and bove
 * Projects to:
 * Affective and motivational aspects

Neospinalthalamic Tract Straight pathway....

descending Pain-Modlaing Pathways Pockets of neurons in brainstem... Raphe Nucleus...//Raphe means net//

Periaqueducatal Grey Matter is considerd to be start of pathway Gets input from ascending pathway

DLPT

RVM

Rostral Ventromedial Medulla (includes raphe nucleus)

allodynia: stimulus previously sensory becomes painful

Transmitters: Substance P:

=Descending Pain-modulatingpathways= =Sensitization= > ==Central Sensitization== > ==Peripheral Sensitization==

=Nociceptive vs Neuropathic Pain=

=Pain Management=