PHRM845-FINAL EXAM Flashcards
Pathophys of pain
What is acute pain?
It is short-lived
-Likely from injury, post-operative flare, or acute damage to a tissue
What is chronic pain?
Pain that lasts more than 3 months
Appropriate pain assessment and adequate pain management are considered to be standard of care, with pain being the ____ vital sign.
Fifth
Functions of pain
-Warning system (to avoid injury/a particular area)
-Aid in repair (hypersensitivity)–becomes sensitive to pain and tells body to avoid the stimulus
-Can be maladaptive (irreversible neuropathy) and may lead to more damage
Temporal features of pain
Onset, duration, course, and pattern
Intensity of pain
Average, least, worst, current pain
-Utilize pain scales
Location of pain
-Focal
-Multifocal
-Generalized
-Referred (comes about from another part of the body; example: MI–> pain distributes down arm)
-Superficial
-Deep
**Opioid induced hyperalgesia (generalized)–chronic use of opioids causes pain to be worse
Quality of pain
Helps determine the source of pain
-Inflammatory: throbbing, pulsating (inflammatory)
-Neuropathic: stabbing, shooting, burning, tingling
-Visceral: squeezing
Clinical pain assessment
-Pain scale (assesses intensity): for adults and children
-Subjective: abused by drug addicts (seeking out opioid narcotics)
**PAIN IS AN EMOTION AND IMPACTS MOOD
Pain circuitry-periphery
-Starts in periphery from trauma or damage
-Receptors are activated and release inflammatory mediators (bradykinin, prostaglandins, and increase K+)
-This causes the afferent neuron to send a signal up to brain
Pain pathway
Periphery
Transmission
Activation of CNS at spinal cord
Input
Transmission of pain signal to brain
Modulation
Peripheral receptors and channels involved in pain signaling
-Temperature sensitive
~Transient receptor potential cation channel (TRP)–conducts Na, K, and Ca
~TRPV (vanniloid)=heat and spice
~TRPM (Melastatin)=cold and menthol
-Acid sensitive
~Acid sensing ion channel (ASIC)
~Activated by H+ and conducts Na+
-Chemical irritant sensitive
~Histamine
~Bradykinin
**Receptors send info to the spinal cord
Pathway of reflex upon painful stimuli
Skin–> afferent nerve/neuron–> spinal cord –> reflex arch bypasses CNS because it does not need CNS processing –> efferent nerve –> muscle to withdraw body part from something
Three different pain A-fibers transduce different pain signals. What are they?
Aβ-fibers
Non-noxious (not pain-producing)
Touch, pressure
Innervate the skin
Faster, (35-75 m/s)
Thick myelin coating
Not involved with pain conduction
Aδ-fibers
Pain, cold
Myelinated (not as thick as Aβ-fibers)
Fast (2-35 m/s)–Not as fast as Aβ-fibers
“First pain”, reflex arc
Sharp, prickly
C-fibers (“prolonged pain”)
Pain, Temp, Touch, pressure, Itch (polymodal)
Unmyelinated
Slow (0.5-2 m/s)
“Second pain”
dull, aching
Peripheral sensitization
Repeated stimuli reduces firing threshold–>gives heightened pain response. Easier for pain firing neuron to conduct action potential.
Increases expression of pain receptors (sensitization)–send more signal into spinal cord (ex: sunburn is sensitive to touch)
Substance P’s role in peripheral sensitization
**One of the neuropeptides release when there is an injury
1.Vasodilation
2. Degranulation of mast cells
3. Release of histamine
4. Inflammation and prostaglandins
Pain circuitry-spinal
-Possibly enhanced expression of sodium channel subtypes contributing to
~enhanced cellular excitability
~generation of ectopic action potentials
Pain circuitry-brain
-Conduction from spinal cord to brain for processing
-High expression of opioid receptors in the brain stem along the descending pathway
Which receptor is the most important in pain modules?
Mu opioid receptor
Impact of mu opioid receptor activation
-Brain
~Alter mood
~Produce sedation
~Reduce emotional reaction
-Brainstem
~Increase activity of descending fibers
-Spinal cord
~Inhibit vesicle release
~Hyperpolarize post-synaptic membrane
-Periphery
~Reduce activation of primary afferent
~Modulate immune activity
How does the somatosensory cortex process pain?
Registers which body part is in pain and the intensity of that pain. Less activity here when patients focus their attention away from their pain.
How does the amygdala process pain?
Anticipates pain and reacts to perceived threats
How does the prefrontal cortex process pain?
Processes pain signals rationally and plans action. Activated when trying to consciously reduce pain.
Decision-making
How does the right lateral orbitofrontal cortex process pain?
Evaluates sensory stimuli and decides on response, particularly if fear is involved. Mindfulness meditation calms down this response.
**Decision making
How does the nucleus accumbens process pain?
Releases DA and 5HT during pleasure or pain
**Important area for addiction
