Physiology Of Pain - 4/19 Karius Flashcards
How can pain be characterized by location?
Deep
Muscle
Visceral
Somatic/cutaneous
Adelta fiber characteristics?
Small, sparsely myelinated
Fast and sharp pain
C fibers characteristics?
Unmyelinated fibers associated with dull pain
Nociceptive are sensitive to what?
What additional types?
Thermal and mechanical stimuli
Silent/sleeping
Mixed modality nociceptors express what?
Mechanosensitive Na+ channel (SCN9A or Na1.7)
Mutations in what channel lead to an absence of pain sensation?
Additional mutation may produce what?
SCN9A or Na1.7
Paroxysmal pain syndrome
Nociceptors express what kind of receptors?
What do they do?
Ligand-gated
Alter the sensitivity of the nociceptors to input
What do the nociceptors include receptors for?
Substance P
Kinins (bradykinin)
ATP
H+
How can pain be characterized?
Fast pain (sharp)
Slow pain (dull)
A delta fibers release what kind of nt?
Act on what?
Associated with what kind of pain?
EAA
Non-NMDA receptors
Fast pain
What nts are released by C fibers?
What kind of pain?
Substance P
EAA
Slow pain
Visceral afferents travel with what?
Autonomic nerves
What parts of the brain play a role in localizing the pain?
S1 and S2
This part of the brain is particularly important in the interpretation of nociceptive inputs
Insular cortex
Fx of insular cortex?
Processes info about the internal state of the body
Contributes to the autonomic response to the pain
Integrates all signals related to the pain (asymbolia)
Where else do many nociceptive inputs go to?
Amygdala
The amygdala is particularly important for activating/producing what?
Emotional components inherent in the sensation of pain
Visceral nociceptors have synapses where?
Associated with what physiological changes?
Hypothalamus and medulla
Diaphoresis and altered BP
This theory is based on the observation that other somatic input can alleviate pain…
Gate Theory
1st step in the gate theory of pain involves what kind of fiber?
Branches/travels where?
ABeta fiber
Travels via dorsal columns but also branches within the spinal cord
Step 2 of the gate theory involves ABeta fiber releasing what that activates what?
EAA that activates inhibitory interneurons in the spinal cord
Step 3 Of the gate theory involves the interneuron doing what?
Inhibitory interneuron releases glycine to inhibit the activity of the 2nd order neuron in the pain pathway
What is activated in step 1 of the descending mechanism?
Activated by what?
Neurons in the Periaqueductal Gray
EAA, opiates, cannibinoids
Axons from the PAG neurons travel where?
Release what?
These activate what?
Midline Raphe nuclei
Enkephalins (Leu and Met)
Raphe neurons (mu receptors)
Axons from the Raphe neurons travel where to release what?
Activating what?
Causing what?
Spinal cord to release serotonin
Inhibitory interneurons
Release opiates
Opiates released by the interneuron active what? Where?
Mu receptors on the presynaptic terminal of the C fiber
Opiates released from the interneuron produce what?
Pre-synaptic inhibition that reduces the release of Substance P from the nociceptors and reduces pain transmission
Deep pain is associated with what kind of fibers?
With what parts of the body?
What special feature?
C fibers
Periosteum, ligaments
Muscle spasm
Cause of muscle pain?
Source?
Types of associated pain?
Injury or ischemia during contraction
A delta and C type
Fast and slow pain
Visceral pain has what type of receptors?
Opened by what?
C type (Group IV)
Stretch receptors (distention), often referred
Referred pain from heart attack in men goes where?
Left arm
Left shoulder
Jaw
