Pain pathway Flashcards
Pain
- emphasizes the complex nature of pain as a physical, emotional, and psychological condition
- does NOT correlate with tissue damage
Nociception
- the experience of pain with a series of complex neurophysiologic processes
- Medications target causes of pain by actions on transduction, transmission, interpretation and modulation in both PNS and CNS
Hyperalgesia
increased pain sensations to normally painful stimuli
Allodynia
Perception of pain sensations in response to normally non-painful stimuli
Chronic pain affects ____% of adult population
40%
The order of pain perception
Transduction > transmission > modulation > perception
Transduction
Nerve/electrical impulses/signals start at the nerve endings
Transmission
Travel of nerve/electrical impulses to the nerve body connecting to the dorsal horn of the spinal cord
What is modulation and where does it occur?
Dorsal horn
Process of altering (inhibiting/excitatory) pain transmission mechanisms at the dorsal horn to the PNS and CNS
Perception occurs where
Thalamus acts as central relay station for incoming pain signals and the primary somatosensory cortex serving for discrimination of specific sensory stimuli
Which drugs affect transduction
- Local anesthetics
- NSAIDs
Which drugs affect transmission
- local anesthetics
Which drugs affect modulation
- local anesthetics
- opioids
- ketamine
- a2 agonists (clonidine, precedex)
Which drugs affect perception
- opioids
- a2 agonists (clonidine, precedex)
- general anesthetics
What are the 2 types of afferent nerve fibers, and what do they sense
- Unmyelinated (C-fibers): burning pain from heat and pressure from sustained pressure
Which chemical mediators cause pain
- peptides
- Eicosanoids
- Lipids
- neutrophins
- cytokines
- chemokines
- extracellular proteases and protons
Which chemical mediators of pain are peptides?
Substance P, Calcitonin, Bradykinin (1st released), CGRP
Which chemical mediators of pain are lipids?
Prostaglandins, Thromboxanes, Leukotrienes, Endocannabinoids
What is the difference between primary and secondary hyperalgesia?
Primary= at the original site of injury from heat and mechanical injury; decreased pain threshold, increase response to suprathreshold stimuli, spontaneous pain, expansion of receptive field
Secondary= uninjured skin surrounding the injury (only from mechanical stimuli); sensitization of central neuronal circuits.
Which part of the spinal cord serves as the relay center
dorsal horn
Which dorsal horn lamina are C fibers present
1 (marginal layer) and 2 (substantia gelatinosa)
Which dorsal horn lamina do opioids primarily act on
lamina 2 (substantia gelatinosa)
Which lamina are A fibers present?
1, 3, 4, 7
Which lamina is substance P found
3 and 4
In gate theory if the gate is open: pain is projected to __________ brain regions
supraspinal
If the gate is closed: pain is _____________________
not felt with simultaneous inhibitory impulses
A-Beta fibers deliver information about pressure and touch (rubbing)
If the gate is open, which fibers are active
A-delta and C fibers
What purpose does the limbic cortex and thalamus play in pain physiology
Perception of motivational-affective pain components
Which area of the CNS depress or facilitate the integration of pain info in the spinal dorsal horn?
Periaqueductal gray (PAG) and Rostral ventromedial medulla (RVM) system
Neuromodulators of pain include
- substance P
- glutamate
- CGRP
- NMDA
- AMPA
- BDNF
- Cytokines
Tissue injury releases which neuromodulators
Substance P and glutamate
Which neuromodulators in spinal area are excitatory impulses
- glutamate
- calcitonin
- Neuropeptide Y
- Aspartate
- Substance P
Which neuromodulators in spinal area are inhibitory impulses
- GABA
- glycine
- enkephalins
- norepinephrine
- dopamine
Ascending pathways of nociceptive information
- Spinothalamic - pain, temp, itch (I, VII, VIII) all afferent fibers
- Spinomedullary
- Spinobulbar - behavior toward pain (I, V, VII)
- Spinohypothalamic - autonomic, neuroendocrine, emotional aspects (I, V, VII, X)
Supraspinal modulation of pain occurs
- Forebrain SI and SII - location and intensity
- Anterior cingulate cortex (ACC) - emotional and motivational aspects
- Insular cortex (IC) - emotional and motivational aspects
- Prefrontal cortex
- Thalamus
- Cerebellum
Descending inhibitory tracts originate in
Periaqueductal gray (PAG), travels through rostral ventromedial medulla (RVM), dorsolateral funiculus, synapse in dorsal horn
Which neurotransmitters are in the descending inhibitory tracts
endorphins, enkephalins, serotonin
How do descending inhibitory tracts inhibit pain?
Hyperpolarize A-delta and C fibers,
- decreases release of substance P
- opening of K+ channels and inhibition of Ca2+ channels
Pain that persists after tissue has healed is called
Neuropathic -> allodynia and hyperalgesia
Treatment of neuropathic pain includes
symptomatic (opioids, gabapentin, amitryptiline, cannabis)
Pain that is diffuse and poorly localized (referred to somatic sites: muscle and skin)
Visceral
Visceral pain is caused by
ischemia, stretching of ligamentous attachments, spasms, distention
Pain perception in neonate occurs at ___ weeks
23 weeks
Neonates have a ____ threshold for pain and ______ pain responses
lower, exaggerated
What are complex regional pain syndromes
- A variety of painful conditions FOLLOWING INJURY in a region with impairment of sensory, motor, and autonomic systems
- Spontaneous pain, allodynia, hyperalgesia, edema, autonomic abnormalities, active and passive movement disorders, and trophic changes of skin and SQ tissues
CV responses to pain include
- HTN
- Tachycardia
- myocardial irritability
- inc SVR
In compromised LV can cause dec. CO and ischemia
Pulmonary responses to pain include
- Increased total body O2 consumption
- Increased CO2 production
- Increased Vm and work of breathing
- Splinting
- Decreased movement of chest wall -> atelectasis and shunting
- Impaired coughing
GI/GU responses to pain include
- N/V
- enhanced sympathetic tone = inc. sphincter tone and dec. motility (ileus and urinary retention)
- Hypersecretion of acid = stress ulceration and aspiration
- Abd. distention
Endocrine response to pain include
- Increased catabolic hormones = catecholamines, cortisol, glucagon
- Decreased anabolic hormones = insulin, testosterone
effects: negative nitrogen balance, carbohydrate intolerance, increased renin, aldosterone and angiotensin
Hematologic response to pain include
Stress related
- platelet adhesiveness
- reduced fibrinolysis
- hypercoagulability
Immune responses to pain include
Stress related leukocytosis, depressed reticuloendothelial system -> increased infection
