Neurobiology of Pain Flashcards
The two nerve fiber types associated with pain are
Type a-delta and Type C
Continue to respond at same rate even at higher temps
Nonnociceptive Thermoreceptors
Respond at higher temperatures only
Nociceptors
Has two temporal elements. A sharp (first) pain, and a second (dull) pain. Which nerve fibers carry:
- ) Sharp (first) pain
- ) Dull (second) pain
- ) Type a-delta
2. ) Type C
Block sodium channels to prevent conduction of impulses along C fibers
Local Anesthetics
What are the four components of pain?
- ) Sensory discriminative component
- ) Affective motivational component
- ) Sensitization
- ) Descending control/central modulation
Tells us the location, intensity and quality of noxious stimulation
Sensory discriminative component
Depends on pathways that target traditional somatosensory areas of cortex
Sensory discriminative component
Tells us the unpleasant quality of the experience and activates the autonomic (fight or flight) reaction
Affective motivational component
Depends on additional cortical and brainstem pathways
Affective motivational component
Hypersensitivity to protect injured area, promote healing and prevent infection
Sensitization Component
Functions to reduce pain perception
Descending control/Central modulation component
What are the three anterolateral pathways that transmit nociceptive information?
Spinothalamic tract, spinorectal tract, and spinomesencephalic tract
Tells us the discriminative aspects of pain and temperature
Spinothalamic Tract
Tells us the emotional and arousal aspects of pain
Spinoreticular Tract
Tells us the central modulation of pain
Spinomesencephalic Tract
What are the three components of the Spinoreticular tract?
Amygdala, Hypothalamus, and Reticular Formation
What are the two components of the spinomesencephalic tract?
Periaqueductal gray matter and superior colliculus
Spinoreticular and spinomesencephalic tracts relay to the
Midline thalamic and intralaminar nuclei
Localization of gray matter decreases in
Chronic pain
A lesion of the parietal lobe or primary sensory cortex causes
Contralateral numb tingling or pain
A lesion of the thalamus causes
Contralateral burning pain (Dejerine-Roussy Syndrome)
A lesion of the DCMLS causes
Tingling, numb sensation and a tight band-like sensation around the trunk or limbs
The feeling of having gauze on fingers is a sign of a lesion of the
DCMLS
A DCMLS lesion can result in an electricity sensation down the back and extremities upon neck flexion. This is called
Lhermitte’s sign
Radicular pain with numbness and tingling in dermatomal distribution (radiculopathy) is a lesion of
Nerve roots
Recessive mutation in sodium channels causing loss of function lead to
Congenital Insensitivity to Pain (CIP)
Dormant mutations of sodium channels resulting in gain of function cause
Inherited Erythromelaglia (IEM) and Paroxysmal Extreme Pain Disorder (PEPD)
Following repeated application of noxious stimuli, neighboring nociceptors that were not responsive now become responsive. This is called
Sensitization
The phenomenon of stimuli that are normally perceived as slightly painful as significantly more painful
Hyperalgesia
The induction of pain by what is normally an innocuous stimulus
Allodynia
Results from changes in sensitivity of peripheral nociceptive receptors and/or central targets
-Protects injured area, promotes healing and prevents infection
Sensitization
The interaction of nociceptors with the “inflammatory soup” of substances to decrease threshold of activation for nociceptors
Peripheral Sensitization
Increase response of nociceptive fibers
Prostaglandins
Non-steroidal Anti-inflammatory Drugs (NSAIDS) inhibit
-Prevents synthesis of prostaglandins
Cyclooxegenase (COX)
Found in C fibers and are activated by moderate heat (45C) and capsaicin
Vanilloid receptor (VR1) / transient receptor potential (TRPV1) channels
Repeated application causes desensitization of C fibers and also depletes Substance P to block peripheral sensitization
Capsaicin
An immediate, activity dependent increase in the excitability of neurons in the dorsal horn of the spinal cord following high levels of activity in the nociceptive afferents to increase pain sensitivity
Central Sensitization
Transcription independent (windup) lasts only during stimulation
Acute central sensitization
Transcription dependent (allodynia) outlast stimulus for hours and can be mediated by COX
Chronic Central Sensitization
Reduction in threshold for activation by peripheral stimuli
Chronic Central Sensitization
Chronic Central Sensitization causes the expansion of
Receptive field size
What are the two forms of descending control of pain perception?
Stress-induced analgesia and the placebo affect
Effects can be blocked by naloxone, an inhibitor of opiate receptors
Placebo pain response
The theory that pain results from the balance of activity in nociceptive and non-nociceptive afferents
Gate theory of Pain
Purposeful lesion in the lateral funiculus from dentate ligament to line of ventral rootlets several segments rostral to highest dermatomal level of pain
Cordotomy for Cutaneous pain
Visceral pain is also conveyed centrally by neurons that carry
-Called referred pain
Cutaneous pain
