Nociception I-III Flashcards
What tract carries temperature and pain information?
the anterolateral system
Where are the cell bodies for temperature receptors?
in the dorsal root or trigeminal nerve (for the head)
Each primary sensory temperature neuron has an axon that _____.
bifurcates
Where do each of the axon limbs in a primary sensory neuron go?
one goes to the skin and one goes to the CNS (the central axon)
Cool receptors are associated with ____ fibers.
Aδ
_____ (temperature) receptors are associated with Aδ fibers.
Cool
Warm receptors are associated with ____ fibers.
C
____ (temperature) receptors are associated with C fibers.
Warm
Where is the first synapse for the DRG neurons?
the dorsal horn of the spinal cord
What is the spinothalamic tract?
the relay of info thru the thalamus to the somatosensory cortex
What is the spinoreticular tract?
relay of info via the reticular formation to the hypothalamus for regulation of temperature and ANS function
This is tract relay of info via the reticular formation to the hypothalamus for regulation of temperature and ANS function.
spinoreticular tract
What tracts does the ALS system include?
spinoreticular
spinomesencephalic
The _____ pathway refers to the axons of the dorsal hor second order neurons that cross the midline and ascend anterolaterally.
ALS
With respect to site of origin of sensory info, info about temp and pain ascends _____ in the spinal cord.
contralaterally
The ____ is a principal pathway that conveys pain info to the ventrobasal thalamus (including the VPL).
spinothalamic tract
The spinothalamic tract is a principal pathway that conveys ____ info to the _______.
pain; ventrobasal thalamus (including the VPL)
The _____ pathway conveys pain inputs that lead to forebrain arousal and elicits emotional/behavioral responses from the limbic system.
spinoreticular tract
The spinoreticular tract pathway conveys ____ inputs that lead to ______ and elicits _____.
pain; forebrain arousal; emotional/behavioral responses from the limbic system
The _____ tract projects to the midbrain periaqueductal gray region (PAG) and is important for descending control of pain.
spinoreticular
The spinoreticular tract projects to the_____ and is important for ______.
midbrain periaqueductal gray region (PAG); descending control of pain
How does the cingulate gyrus contribute to pain?
it is the emotional component
How does the insular cortex contribute to pain?
processes info related to the ANS component of pain
Intense pressure activates ____ receptors.
Aδ
Damaged cells release what 4 items?
K
ATP
PGs
acids (H+)
Name 4 compounds that lead to direct activation of nociceptors.
bradykinin
potassium
acid
5-HT
Name 5 compounds that sensitize nociceptors.
PGs substance P ATP ACh 5-HT
___ increases the synthesis of prostaglandins from neighboring cells, which then sensitize nociceptors.
Bradykinin
How does aspirin work as an analgesic?
inhibits COX to prevent PG synthesis and prevent nociceptor sensitization
____ is known as primary hyperalgesia.
Sensitization of nociceptors
Sensitization of nociceptors is known as _____.
primary hyperalgesia
What is allodynia?
when pain sensitization is extreme enough to allow non-noxious stimuli to trigger a painful sensation
This is the term for when pain sensitization is extreme enough to allow non-noxious stimuli to trigger a painful sensation.
allodynia
What is the triple response?
a bradykinin mediated reddening, wheal, and flare due to tissue injury
This is a bradykinin-mediated reddening, wheal, and flare due to tissue injury.
the triple response
How does bradykinin cause pain?
it activates C fiber nociceptors –> depol –> APs –> substance P is release
What does substance P do?
causes vasodilation/pain; closes K+ channels –> depolarization –> enhancement, prolongation of glutamate action
Substance P is a sensitizer that ______ of nociceptors and collaterals in the exposed region.
reduces threshold for activation
_____ is a sensitizer that reduces threshold for activation of nociceptors and collaterals in the exposed region.
Substance P
Where in the brain do C fibers terminate?
in the substantia gelatinosa
On what fibers do C fibers terminate? Where are these fibers found?
in the Rexed’s laminae in the dorsal horn of the spinal cord (substantia gelatinosa)
Where do visceral and somatic pain inputs converge?
at the dorsal horn neuron
Why is injury to internal organs often perceived as cutaneous pain?
bc visceral and somatic pain pathways converge at the dorsal horn neuron, but cutaneous input dominates, and the two are perceived as the same
Name 2 types of glutamate receptor in the dorsal horn. Are they fast or slow?
NMDA (slow)
AMPA (fast)
Why does pain persist, even after glutamate is taken back up?
substance P persists bc it’s not removed by reuptake
What neurons process info related to the localization of pain?
the VPL
What is the pathway of the anterolateral system?
skin –> dorsal root ganglion –> dorsal horn of the spinal cord –> decussate –> specific tract in the brain (spinoreticular, spinomesencephalic, or spinothalamic)
Where does the ALS decussate?
immediately (in the spinal cord)
What is nociceptive pain?
detection of an acute, painful stimulus
What is neuropathic pain?
injury to the nervous system –> chronic pain
What is the pathway of the spinoreticular tract?
skin –> dorsal root ganglion –> dorsal horn of the spinal cord –> decussate –> medulla –> reticular formation –> hypothalamus and thalamic nuclei
Name the system that uses this pathway:
skin –> dorsal root ganglion –> dorsal horn of the spinal cord –> decussate –> specific tract in the brain (spinoreticular, spinomesencephalic, or spinothalamic)
the anterolateral system
What is the pathway of the spinomesencephalic tract?
skin –> dorsal root ganglion –> dorsal horn of the spinal cord –> decussate –> midbrain –> mesencephalon
What is the pathway of the spinothalamic tract?
skin –> dorsal root ganglion –> dorsal horn of the spinal cord –> decussate –> thalamus –> somatosensory cortex
Name the tract:
skin –> dorsal root ganglion –> dorsal horn of the spinal cord –> decussate –> medulla –> reticular formation –> hypothalamus and thalamic nuclei
spinoreticular
Name the tract:
skin –> dorsal root ganglion –> dorsal horn of the spinal cord –> decussate –> midbrain –> mesencephalon
spinomesencephalic
Name the tract:
skin –> dorsal root ganglion –> dorsal horn of the spinal cord –> decussate –> thalamus –> somatosensory cortex
spinothalamic
A brain region that is particularly sensitive to opioids is the _____.
PAG
What happens if the dorsal lateral funiculus is cut bilaterally?
stimulation-produced and systemic opiate-induced analgesia are blocked
Stress leads to increased activity in the limbic system, which in turn leads to activation of the ____.
PAG
Activation of the PAG ultimately leads to ____ in the pain pathway.
inhibition of 2nd order neurons of the dorsal horn
How do we know that endogenous opioids are involved in the placebo affect?
giving naloxone blocks the placebo affect
What are the 2 types of sodium channels that sensory afferents have?
TTX sensitive
TTX resistant
What does the TTX-resistant channel do?
plays a role in setting inflammatory pain thresholds
Following nerve damage, the expression, distribution, and function of _____ is altered, leading to spontaneous discharge of pain primary afferents.
Na+ channels
Why aren’t Na+ channel blockers used to treat pain?
they’re nonselective (CNS, CV SEs would occur)
What happens in the substantia gelatinosa following injury of C fibers?
Aβ afferents begin to invade it
How do glial and immune cells contribute to pain?
astrocytes develop and maintain neuropathic pain
macs secrete TNF that activates TTX-resistant Na+ channels
microglia secrete BDNF –> reverse potential so GABA becomes excitatory –> hyperalgesia
