Pain & Temperature Flashcards
What are nociceptors?
Respond to noxious stimuli resulting from skin or soft tissue injury
Nociceptor activation usually causes ____
Pain
What is pain?
A subjective interpretation of unpleasant stimulus, not necessarily a product of nociceptor excitation
Nociceptive pain
Pain resulting from nociceptor activation due to tissue injury and resultant inflammation
neuropathic pain
Pain resulting from direct insult to the nerve
Fast, sharp, pricking pain is transmitted to the spinal cord by ____ which carry…
Myelinated A-delta fibers
Thermal & mechanical noxious stimuli
Slow dull pain is transmitted to the spinal cord by ____ which carry…
Unmyelinated C fibers
High intensity thermal, chemical, & mechanical noxious stimuli
What might explain referred visceral pain?
Pain from viscera enters spinal cord the same way somatic pain does
What is primary hyperalgesia?
Sensitization of surrounding nociceptors after injury or inflammation
What stimulates primary hyperalgesia?
Release of bradykinin, prostaglandins, histamine, acetylcholine, substance P, CGRP, etc. from cells involved in injury
How does the release of inflammatory products affect nociceptor activation?
Lowers activation threshold
What is central hyperalgesia?
Sensitization of dorsal horn cells after injury due to persistent activation of NMDA receptors by glutamate releasing C fibers
Changes/sensitization in dorsal horn may result in…
Long term decrease of pain threshold of patient
Central axons of A-delta & C fibers pathway
- Ascend 2 segments in Dorsolateral fasciculus of Lissauer
- synapse in dorsal horn with nucleus proprius, Pericornual cells and Substantia gelatinosa
Most synapses of primary A-delta and C fibers involve ____ that control pain perception
Interneurons
Axons of nucleus proprius cross the midline and form the ____
Lateral spinothalamic tract
Lateral spinothalamic tract ascends to the ____ in the ____
Thalamus
Anterolateral system
Lateral spinothalamic tract sends collaterals to…
Reticular formation
Periaqueductal gray (emotional response)
Nucleus gracilis
Nucleus cuneatus
Hypothalamus (autonomic pain control)
After spinothalamic fibers synapse in the thalamus, they ascend to the ____
Sensory cortex
Explain Gate Control Theory of Pain
- A-beta mechanoreceptors send collaterals to Substantia gelatinosa —> inhibits nucleus proprius
- A-delta & C nociceptors send excitatory signals to nucleus proprius while inhibiting Substantia gelatinosa
- mechanoreceptors turn off pain, nociceptors turn on pain —> relative excitation of 2 pathways can modulate pain
What is the Gate Control Theory of Pain?
Based on observation that proprioceptive & mechanical stimulation diminishes perception of pain
Stimulation of periaqueductal gray results in…
- profound & specific analgesia (can feel touch & vibration, not pain)
- excitation of serotoninergic Raphe nuclei and noradrenergic locus caeruleus
Raphe nuclei and locus caeruleus send fibers in the ____, resulting in…
Fasciculus of lissauer (DLF)
Inhibition of output of Pericornual cells & nucleus proprius
Descending inhibitory pathways of periaqueductal gray ultimately interfere with…
Glutamate secretion of primary pain afferents
Opioid administration in the periaqueductal gray results in ____
Anesthesia
Enkephalins, beta-endorphins, and dynorphins are ____ released in various areas of the nervous system
Endogenous opioid peptides
