MODULE 5- Pain + Temperature Flashcards
nociceptors
unspecialized, nonspecific nerve endings that transmit a variety of stimuli + translate then into afferent APs
2 kinds of slowly transmitting afferent fibers
-Aδ (delta) lightly myelinated axons
-C unmyelinated axons, small diameter
pain is transmitted only when strength of stimulus is low/high
high
2 categories of pain
-faster conducting sharp FIRST PAIN carried by Aδ fibers
-delayed, broadly acting, dull SECOND PAIN carried by C fibers, which respond to all types of nociceptive stimuli
faster conducting sharp FIRST PAIN is carried by Aδ/C fibers
Aδ fibers
`
delayed, broadly acting, dull SECOND PAIN is carried by Aδ/C fibers
C fibers
2 types of Aδ fibers
-type 1
-type 2
type 1 Aδ fibers
-high heat thresholds
-respond to immediate potentially dangerous stimuli (e.g., pin prick)
type 2 Aδ fibers
-low heat threshold
-high threshold for mechanical stimulation
what does capsaicin activate
TRPV1 (VR-1)
-whose endogenous ligand is anandamide + temperature
where is capsaicin found
chili peppers, habanero, etc.
when is capsaicin an irritant
when applied to mucus membranes of the mouth + when injected subcutaneously
repeated administration of capsaicin leads to
desensitization
how is capsaicin clinically useful
as an analgesic + anti-inflammatory agent
central pain pathways (3)
-dorsolateral tract of Lissauer
-anterolateral system (AL)
-dorsal-column medial lemniscal system (DCML)
dorsolateral tract of Lissauer
ascending + descending branches of incoming afferent axons entering the dorsal horn
anterolateral system (AL)
formed from 2nd-order neuronal axons in the dorsal horn laminae I + V (wide dynamic range neurons)
-ascends carrying pain, temperature, + crude touch information to somatosensory cortex via the thalamus
dorsal-column medial lemniscal system (DCML)
carries mechanical stimuli
-touch, pressure, vibration, proprioception
AL + DCML systems are separate or together in the spinal cord
separate
where does the AL system decussate
at the point of entry into the spinal cord
where does the DCML system decussate
at the medulla
pain + temperature are ipsilateral/contralateral
contralateral
touch + pressure are ipsilateral/contralateral
ipsilateral
dermatomes
enable diagnosis of the location of the spinal cord injury