Pain Pathways (Exam II) Flashcards
Differentiate the sensory-discriminative & motivational-affective aspects of pain.
- Sensory-discriminative - Ascending pathways and the perception of pain (location, intensity, sensation, etc.)
- Motivational affective - responses to painful stimuli (Ex. arousal, reflexes, endocrine responses, and emotional changes)
What is nociception?
- The experience of pain through a series of complex neurophysiologic processes.
What are the four stages of pain perception?
- Transduction (tissue level)
- Transmission (via nerves)
- Modulation (via spinal cord)
- Perception (CNS)
Where does the modulation of pain impulses occur?
- Dorsal horn of the spinal cord
What drugs are used to affect the transduction of pain?
What specifically is being affected by these drugs?
- Local anesthetics & NSAIDs
- Peripheral nociceptors
What drugs are used to affect the transmission of pain?
What specifically is being affected by these drugs?
- Local anesthetics
- Αδ and C fibers
What drugs are used to affect the modulation of pain?
What specifically is being affected by these drugs?
- LA’s, opioids, ketamine, α2 agonists
- Afferent fibers of the dorsal horn
What drugs are used to affect the perception of pain?
What specifically is being affected by these drugs?
- General anesthetics, opioids, α2 agonists
- Brain
Where are nociceptors located?
- Skin
- Muscles
- Joints
- Viscera
- Vasculature
What characterizes afferent C-fibers?
- Unmyelinated
- Pain from heat (burning) & sustained pressure
- Slow (less than 2 m/s)
What characterizes Aδ fibers?
-Myelinated
- Type I: Aβ & Aδ (heat,mechanical, chemical)
- Type II: Aδ (heat)
- Fast (>2 m/s)
What chemical mediators of pain are targeted with spinal anesthetics?
Peptides
- Substance P
- Calcitonin
- Bradykinin
- CGRP
Which chemical mediator is released first in response to injury?
- Bradykinin
What chemical mediators of pain are inhibited by NSAIDs?
Lipids
- Prostaglandins
- Thromboxanes
What chemical mediators of pain are inhibited by cannabis?
Lipids
- Endocannabinoids
What is sensitization?
- Decreased pain threshold (likely due to upregulation of receptors)
Differentiate hyperalgesia and allodynia.
- Hyperalgesia - ↑ pain sensations to normally painful stimuli.
- Allodynia - perception of pain to things that aren’t normally painful.
What characterizes primary hyperalgesia?
Hyperalgesia at original site of injury.
- Lower pain threshold
- Spontaneous pain
- Expansion of receptive field
What characterizes secondary hyperalgesia?
- Sensitization of CNS → hyperalgesia from uninjured skin surrounding injury.
What area of the brain accounts for the perception (location & intensity) of pain?
- Somatosensory Cortex I & II (SI & SII)
What is the relay center for nociceptive and sensory activity?
How does sensory activity travel from this area to the cerebrum?
- Spinal Dorsal Horn
- Ascending pathways
What areas of the brain may depress or facilitate the integration of painful information in the spinal dorsal horn?
- PAG - Peraqueductal Gray Matter
- RVM - Rostral Ventral Medulla
Where are afferent C-fibers located in the spinal column?
- Dorsal horn: Lamina I & II
What is another name for Lamina II?
What drugs work here?
- Substantia gelatinosa
- Opioids
What nerve fibers are associated with an “open-gate” for pain?
What nerve fibers can shut this gate?
- Aδ & C-fibers = open
- Aβ fibers = closed
What receptors does ketamine target for pain modulation?
- NMDA
The excision of what structure would result in the complete loss of perception of pain?
Amygdala
Bonus points if you just said the whole brain you degenerate.
What neurotransmitters propagate excitatory transmissions in the spinal column?
- Glutamate
- Calcitonin
- Neuropeptide Y
- Aspartate
- Substance P
What neurotransmitters propagate inhibitory transmissions in the spinal column?
- GABAA
- Glycine
- Enkephalins
- NE
- Dopamine
What are the four ascending pain pathways?
- Spinothalamic
- Spinomedullary
- Spinobulbar
- Spinohypothalamic
What information is carried by the spinothalamic pathway?
What laminae are used?
- Pain, Temp, & Itch
- Laminae I, VII, and VIII
What information is carried by the spinobulbar pathway?
What laminae are used?
- Behavior towards pain
- Laminae I, V, and VII
What information is carried by the spinohypothalamic pathway?
What laminae are used?
- Autonomic, neuroendocrine & emotional aspects of pain
- Laminae I, V, VII, & X.
What part of the suprapinal pathway differentiates where pain is coming from?
S1 & S2 (Somatosensory cortex 1 & 2)
What supraspinal areas deal with the emotional/motivational aspects of pain?
- Anterior cingulate cortex (ACC)
- Insular Cortex (IC)
- Amygdala
Where do the descending inhibitory tracts originate?
Where do they then synapse at?
- PAG (periaqeueductal gray matter)
- Synapse at dorsal horn
What neurotransmitters are increased with exercise?
- Endorphins
- Enkephalins
- Serotonin
How do inhibitory tracts inhibit the propagation of painful stimuli?
Hyperpolarizing Aδ & C fibers
- ↓ release of substance P
- ↑ pK⁺ and inhibiting Ca⁺⁺ channels
Where does the pain inhibiting impulse originate from in the descending inhibitory tracts?
PAG-RVM areas
When is pain considered chronic rather than acute?
- If > 3 - 6 months
- If pain persists beyond tissue healing
Who is at increased risk of neuropathic chronic pain?
- Cancer patients
- Diabetics
What is the treatment for chronic neuropathic pain?
- Opioids
- Gabapentin
- Amitriptyline
- Cannabis
All situation dependent
How is visceral pain characterized?
What examples were given in lecture?
- Diffuse and poorly localized
What is complex regional pain syndrome?
- Variety of painful issues following an injury (sponateous pain, hyperalgesia, edema, etc.)
When can babies begin to perceive pain?
23 weeks
How does pain affect the GI/GU system?
- ↑ SNS = ↑ sphincter tone and ↓ peristalsis = N/V, ileus, distension, etc.
- Stress ulcers
How can the effects of pain in the cardiovascular system be summarized?
↑ SNS
↑BP, HR, etc.
What hormones experience a decrease in response to chronic pain?
Anabolic Hormones
- Insulin
- Testosterone
What are the pulmonary effects of chronic pain?
- Shallow breathing → atelectasis and pneumonia.
