Lec 8 Pain Flashcards
Receptive fields of pain/temp neurons are ____ (larger/smaller) than mechanosensory.
larger, bc detecting presence of pain more impoartant than exact location of pain
A-delta: myelinated or not? Responds to?
lightly myelinated.
dangerously intense.
C fibers: myelinated or not? responds to?
unmyelinated.
several types of stimuli.
A-delta mechanosensitive detect…
dangerous mechanical (e.g. crrush)
A-delta mechanothermal detect…
dangerous thermal (e.g. burns)
Types of C-fibers
Polymodal - respond to several types of stim.
Non-Nociceptive Thermo - nonharmful thermal stim.
Channel receptor in A-delta & C
Vanilloid (VR-1)
VR-1 is activated by what? What happens when activated?
Activated by heat, [H+], capsaicin.
Opens pore & allows influx of Na+ & Ca2+ = AP.
Inflammatory response: damaged tissues release…
Prostaglandins Histamine Bradykinin ATP Substance P
Inflammatory response: peripheral sensitization
released substances = increased nociceptor responsiveness = reduced threshold for depolarization
Inflammatory response: hyperalgesia
enhanced sensitivity to stimulation around area of damaged tissue (e.g. mild heat on a sunburn hurts worse)
Anti-inflammatory agents act where?
injury site
Opiate drugs act where?
CNS
Local anesthetic acts where?
on nociceptor neurons (blocks Na channels)
Segregation: A-delta & C go where?
Lateral division of dorsal root
Segregation: A-beta, I, & II go where?
medial division of dorsal root
Lissaur’s tracts
incoming spinothalamic axons branch into ascending/descending collaterals.
run up/down 1-2 spinal cord segments before synapsing on N2.
Rexed lamina
gray matter in spinal cord is split into 10 different sections (each section is a rexed lamina). Cell body of N2 is in one of these lamina.
Name some of the Rexed lamina
Marginal Zone
Substantia Gelatinosa
Nucleus Proprius
Spinothalamic projects where?
Reticular Formation (medulla). Parabrachial Nucleus (pons). Intralaminar Nuclei (thalamus).
Parabrachial projects where?
Hypothalamus & amygdala.
Periaqueductal grey matter (midbrain).
Intralaminar Nuclei (thalamus) project where?
frontal lobe
insula
cingulate cortex
Brown Sequard Syndrome results from what?
exactly half of spinal cord segment damaged.
Brown Sequard Syndrome: loss of mechanosensory on what side?
Affected
Bc mechano ascends ipsi.
Brown Sequard Syndrome: loss of pain/temp on what side?
Contralateral to injury.
Bc crosses over before ascending up spinal cord.
Descending Modulatory Pathways originate from what structures? (5)
Periaqueductal Somatosensory cortex Hypothalamus Raphe Nuclei Rostral Medulla
Gate Theory
activating mechanoreceptors = activates interneurons that inhibit ascending nociception.
This is why rubbing a painful area can make it feel better.
How do endogenous opioids modulate pain?
synapse on ascending N2, reducing activity of ascending noci (N1)
Name 3 endogenous opioids
Enkephalins
Endorphins
Dynorphins
Where are enkephalins located?
Periaqueductal
Rostral Medulla
Spinal Cord
Where are dynorphins located?
Periaqueductal
Rostral Medulla
Spinal Cord
Where are endorphins located?
Periaqueductal
