58 Pain Flashcards
What is Referred Pain?
Perception of pain in an area different than the source.
Common phenomena with pain from deep musculoskeletal or visceral structures.
What is Hyperalgesia?
Magnification of pain perception to normally minimally painful stimuli
What is Allodynia?
Perception of pain from a non-painful stimuli
ex: touching a sunburn
Similarities with Dysthesia.
What is Hyperesthesia?
What is Dysthesia?
Hyperesthesia is a magnified sensation of any type
Dysesthesia is a distorted, magnified and unpleasant sensation to normal stimuli (this is similar to Allodynia)
What is Neuropathic pain?
Pain originating from the nervous system itself that is not explained by stimuli
Includes sensations of burning, stabbing, or shooting pain.
What is the difference between Nociceptive and Neuropathic pain?
Why is this relevant pharmacologically?
Nociceptive is normal pain from tissue damage.
Neuropathic is due to nervous system malfunction.
Different Tx and pharmocology works for each.
Describe the basic construction of a Nociceptive the two basic pain receptors.
What do each detect?
MECHANORECEPTORS: High threshold, usually with free nerve endings
CHEMORECEPTORS: detect tissue metabolites (released with tissue damage) as well as inflammatory mediators and neuromodulators
As pain stimuli for chemoreceptors, what are examples of... Tissue metabolites (3)? Neurotransmitters and modulators (2)? Tissue cell products (3)? Inflammatory mediators (3)?
Tissue metabolites - potassium, acids, ATP
Transmitters/neuromodulators - substance P, norepinephrine.
Tissue cell products - histamine, bradykinin, nerve growth factors
Inflammatory mediators - prostaglandins, cytokines, leukotrines
What is Substance P (SP)?
a neuropeptide - a substance that functions as a neurotransmitter and as a neuromodulator.
Substance P is released from the terminals of specific sensory nerves, it is found in the brain and spinal cord, and is associated with inflammatory processes and pain.
Chemical mediators…
Some directly activate & some sensitize fibers
Some cause release of other algetic substances
Some recruit other elements to an inflammatory reaction
Peripheral nerve fibers are modified by stimuli…
PGE2, bradykinin, and NGF activate G-protein mechanisms that phosphorylate ion channels
Protein Kinase A (cAMP-dependent) and C (calcium dependent) phosphorylate transient receptor potential ion channels (TRPV1)
.
What are afferent Pain fibers (Alpha Numeric Greek system)?
A delta (faster) C fibers (slow and unmyelinated)
What are the qualities of afferent nerve fibers A-delta and C fibers? Adaption speed? Conduction speed? Purpose? Effect is where?
Both: slow adapting and slow conduction
A-detla: 15 m/s (quick withdrawal from pain)
C: 1 m/s (confirmation or denial of pain)
Release neurotransmitters both in CNS and peripheral end of PNS which contributes to vasodilation and swelling at tissue and may affect neuroplasticity (via neurotrophic factor BDNF)
What is the Zone of Lissauer?
When pain sensory fibers reach the nervous system via the DRG, they collateralize and spread over several segments up and down the spinal cord via the Zone of Lissauer. This means that pain the input is not highly focused in the spinal cord.
In what layers (3) do C fibers terminate in the spinal cord?
Layer I
Layer IV
Layer V
What do A-beta fibers detect?
What is their relationship to pain fibers?
Convey normal touch, pressure, and proprioception
Can inhibit pain fibers (note: enkephalin interneurons also modulate pain sensation. These are in the spinal cord)
This is why rubbing a painful area can diminish pain
What are MARGINAL vs WIDE DYNAMIC pain transmission neurons?
What layer of the spine are each located?
What do each transmit?
MARGINAL aka nociceptive specific neurons are in LAYER 1 and transmit SHARP STINGING pain that enables you to LOCALIZE the pain, rather than intensity.
WIDE DYNAMIC pain transmission are in LAYERS 4 and 5 and receive highly CONVERGENT information via DENTRITES IN ALL LAYERS that relays the INTENSITY of pain rather than location. Contributes to REFERRED PAIN.
Both transmit to the spinothalamic tract.