Tuesday, 4-19-Physiology of Pain (Karius) Flashcards
___ pain is associated with the immediate injury (sharp)
___ pain is characterized as dull or achy, often occurs after the injury
fast
slow
what are the 2 types of nociceptor nerve fibers?
- Adelta fibers
- C fibers
These nociceptor fibers are small, sparsely myelinated, and associated with fast/sharp pain
Adelta fibers
These nociceptor fibers are unmyelinated fibers associated with dull pain (slow pain)
C fibers
Mutations in this channel lead to an absence of pain sensation: __
SCN9A or Na 1.7 (Mechanosensitive Na channel)
Nociceptors express a number of ligand-gated receptors which alter the sensitivity of the nociceptors to input. These include receptors for: __
- Substance P
- Kinins (bradykinin)
- ATP
- H+
-When these chemicals bind to their receptors, they change the sensitivity of the nociceptors (usually increasing) and activate the silent nociceptors
This tract/pathway to the brain is concerned with “fast” pain: ___
This tract/pathway to the brain is concerned with “slow” pain: ___
spinothalamic tract
spinoreticulothalamic system
___ fibers release EAA’s as NT acting primarily on non-NMDA receptors
Adelta
__ fibers release Substance P and EAA as its NTs
C type
Nociceptors that travel with the __ pathway synapse on an interneuron in the SC before crossing and ascending to the RF. This synapse is the site of much modulation of SC function –> Local (gate theory) and descending (opioid pathways)
spinoreticulothalamic
Visceral afferents travel with __, rather than with either of the 2 spinal pathways
autonomic nerves
___ receive input from the nociceptors and play a role in localizing the pain
S1 and S2
The ___ is particularly important in the interpretation of nociceptive inputs. It processes information about the internal state of the body and contributes to the autonomic responses to the pain. It INTEGRATES ALL SIGNALS RELATE TO THE PAIN (ASYMBOLIA)
insular cortex
i.e., sweating, rapid breathing, increase HR and BP; BP increasing due to pain
Many nociceptive inputs go to the ___. This is particularly important for activating/producing the emotional components inherent in the sensation of pain
amygdala
___ nociceptors, traveling with the autonomic nerves, have additional synapses within the hypothalamus and the medulla
visceral
-these additional synapses form the basis of the physiological changes associated with visceral pain, including diaphoresis and altered BP
How does rubbing the area of skin activated by the Abeta fiber reduce sensation of pain?
activation of an Abeta fiber by normal stimuli (pain) –> Abeta fiber releases EAA and activates an inhibitory interneuron in the SC –> Inhibitory interneuron releases Glycine to inhibit activity of 2nd order neuron in the pain pathway
Descending influences can physiologically modify pain:
1) Neurons in the ___ are activated by numerous inputs, including opiate, EAA, and the cannibinoids –> 2) Axons from step 1 travel to the midline Raphe Nuclei and release ___, which activate the raphe neurons –> 3) Axons from the raphe neurons travel to the SC and release ___, which activate inhibitory interneurons, causing them to release opiates –> 4) the opiates released by the interneuron activate __ receptors on the presynaptic terminal of the C fiber –> 5) This produces pre-synaptic inhibition that reduces the release of ___ from the nociceptor and reduces pain transmission
1) Periaqueductal gray
2) enkephalins
3) serotonin
4) mu
5) substance P
Deep pain is associated with periosteum, ligaments, is usually dull/achy. It has few __ fibers and many __ fibers. They are associated with muscle spasm
few Adelta fibers
Many C fibers
Muscle pain is caused by injury or ischemia during contraction, has both Group ___ fibers present, and gets both fast and slow pain associated with muscle.
III and IV
Visceral pain is poorly localized, has few receptors and mostly group __ receptors, activated by stretch receptors (distention) and is often referred
IV
