Pain Flashcards
Final experience of pain results from the concerted actions of what three orders of brain processing
1.NOCICEPTIVE MATRIX
•Ascending paths to reticular formation (PAG, PB) thalamus, amygdala and somatosensory regions
2.PERCEPTUAL / ATTENTIVE MATRIX
•Anterior insula and cingulate cortices
3.REAPPRAISAL / EMOTIONAL MATRIX
•PFC
Where to nocicepters enter and synapse
The dorsal horn
What are the two types of nociceptors?
C type to lamina I and II
A-beta type to lamina I and V
Explain the range of Lamina V neurons
Wide dynamic range (WDR)
What is within the WDR of lamina V neurons?
- signal pain intensity & mechanical stimuli
- Receive convergent info from A-beta (non-noxious mechanical, thermal & chemical stimuli) and A-gamma and C (pain afferents)
What forms the ascending anterolateral pain pathway and where does this pathway go?
Axons of lamina I and V decussate and from the ascending anterolateral pain pathways tot brain stem and thalamus.
Dorsal horn neurons mediate what two types of pain into CNS?
Fast pain and slow pain
what are the characteristics of fast and slow pain?
you should make a table to remember this
Where does the spinothalamic system project from?
Spinothalamicsystem projects from dorsal horn (layers I, V, VII)
Where do the spinothalamic neurons project up to?
Spinothalamicneurons decussate and project up the anterolateral column to posterior thalamus
Posterioir thalamus projects pain input into what three areas of the brain?
- somatosensory cortex (S1, S2)
- posterior insula
- cingulate cortex (ACC)
The posterior thalamus generates_________ in _____, _____, and ______ cortices supporting conscious perception and vegetative responses
somato-specific quality; parietal, frontal and insular
Spinothalamictracts branch into what?
reticular formation nuclei
What are the three spinothalamic tract branches?
- A5-7, a NE pathway to cortex/spinal cord for attention and arousal
- Parabrachial(PB), a pathway to the amygdala
- Periaqueductal gray (PAG), part of the descending pathway that control sensitivity to pain
What two roles does the perceptual matrix have?
-projects activity to anterior insula, anterior cingulate, PFC and posterior parietal cortex
•transform sensory events into vegetative reactions and internal feelings
What is the cingulate’s role in the perceptual matrix?
site of affective/emotional aspects of pain. Decides on behavioral patterns based on pain experience
What is the insula’s role in the perceptual matrix?
•Integrates appetitive and aversive valence of pain stimulus with impact
What structures does the Apino-parabrachial - amygdala circuit include?
dorsal horn of the spinal chord,, parabrachial nucleus, amygdala, PAG, Hypothalamus and ventrolateral medulla
Where is the parabrachial nucleus?
the RF
how does the SPINO-PARABRACHIAL-AMYGDALA CIRCUIT work?
Dorsal horn neurons project pain information
to PARABRACHIAL NUCLEUS in RF, which projects to the amygdala, then to the hypothalamus and PAG
amygdala’s role in the SPINO-PARABRACHIAL-AMYGDALA CIRCUIT
emotional-affective aspects of pain including: anxiety
fear conditioning
antinociception
autonomic adjustments
PAGs role in the SPINO-PARABRACHIAL-AMYGDALA CIRCUIT
défense responses and pain regulation
Hypothalamus & ventrolateral medulla role in SPINO-PARABRACHIAL-AMYGDALA CIRCUIT
autonomic homeostatic adjustment
What sympathetic activation occurs in the SPINO-PARABRACHIAL-AMYGDALA CIRCUIT
- Diversion of blood to ore vital organs
- Increased HR and BP to supply blood quickly and efficiently
- Increased respiratory rate to provide more oxygen
- Glycogenolysisin liver and muscle for glucose
- Gluconeogenesis from amino acids
- So where’s the fight or flight??
What does PAG stand for?
PERIAQUEDUCTAL GREY
What two things does the PAG receive input from?
- Ascending spinothalamicpathways or indirectly via parabrachialnucleus
- Amygdala mediating emotional aspects of pain responses
What actions is the PAG involved in?
Involved in:
•Defense responses
•Supraspinalpain regulation
What are the two PAG defense responses?
•Fight-flight in response to pain/aversive stimuli
•Defense responses regulated by cingulate, insula,
amygdala, hypothalamus & PFC
what are the two zones of the PAG?
ventrolateral zone and lateral zone
What does the ventrolateral zone do?
Ventrolateralzone: passive emotional coping
•Quiescence, immobility, fright/hyporeactivity
•Disengagement, withdrawal, inhibition of sympathetic activity (hypotension, bradycardia)
•Long-lasting opioid mediated analgesia
What does the lateral zone do?
Lateral zone: active emotional coping
•Rostral: confrontation defense (fight)
•Caudal: defensive behavior (flight)
•Excitation of sympathetic activity (hypertension, tachycardia)
•Short-lasting non-opioid mediated analgesia
Descending pathways originating in limbic cortex do what?
alter the synaptic activity of dorsal horn neurons that mediate pain
Homeostatic maintenance of physiologically acceptable pain levels is determined by what?
activity and sensitivity of ascending and descending pain pathways.
The PAG and supra spinal pain regulation pathway occurs in what order?
•Cingulate cortex →hypothalamus →PAG →reticular nuclei →dorsal horn
PAG is central figure; it is responsible for ______
stress-induced hypoalgesia
What regulates the PAG modulation of pain?
Complex ascending and
descending pathways
Descending pathway provides negative (or positive) feedback on the spinal chord including:
- Somatosensory, cingulate, insula and prefrontal cortices regulate the amygdala, hypothalamus and PAG.
- PAG projects down to raphe and A5,7 reticular formation nuclei
Raphe and A5,7 regulate
synapse between ______ and _______
sensory;
spinothalamicneurons
Tell me about rap he nucleus serotonergic cells..
stress-mediated; tonic inhibition of pain transmission
Tell me about rap he nucleus Non-serotonergic cells..
- Non-serotonergic: regulates immediate pain, alerting and arousal.
- ON cells facilitate pain transmission
- OFF cells inhibit pain transmission via opioid mechanisms
How does A4,A7 regulate synapse between sensory and spinathalamic neurons?
•Inhibit pain transmission via α2 receptors.
Opiods are used in ascending or descending pathway regulating pain
descending
what activates opioids?
•Painful stimuli activate opioid interneurons (enkephalin& dynorphin) in various CNS regions including the PAG, reticular nuclei and dorsal horn
Opioids and cannabinoid actions in the midbrain and
medulla inhibit pain by …
upregulatingthe activity of
medullary raphe OFF-cells
What two things enhance the antinociceptive
effect of opioids by increasing the availability of
spinal norepinephrine?
Tricyclic antidepressants (TCAs) and other NE reuptake inhibitors
REGULATION AND INHIBITION OF PAIN
IN THE DORSAL HORN includes:
Descending serotonin and NE pathways stimulate dorsal horn opioid interneurons to inhibit the spinothalamic neurons.
OPIOID INTERNEURONS in dorsal horn preform what three actions?
- Inhibit synaptic transmission between pain afferent and spinothalamic neuron.
- Decrease Substance P transmitter release
- Down regulate Substance P neurokinin-1 receptors.
Opiate drugs are agonists of what?
opioid neurotransmitters (eg. enkephalin).
opiate drugs stimulate what?
opioid receptors in hypothalamus, PAG and dorsal horn.
In the Gate Control Theory,C fibers excite pain projection neurons directly or by what?
inhibiting enkephalininhibitory interneurons
In the Gate Control Theory, Cutaneous tactile mechanoreceptors Aα & Aβ inhibit C fiber pain axons by stimulating what?
enkephalin interneurons
In the Gate Control Theory, the descending pain control pathway inhibits what in response to pain?
C fiber-projection neuron synapse via presynaptic inhibition
In TENS (transcutaneous electrical nerve stimulation), \_\_ & \_\_\_ are selectively stimulated to \_\_\_\_\_ pain conveyed by C fibers.
Aα; Aβaxons; suppress
CINGULATE & INSULAR CORTices are the site of what?
Site of convergence of somatosensory and association cortex & ascending spinal pathways
•Somatic perceptual and cognitive features of pain are integrated with attentional and affective-motivational systems.
•Maintains flexibility in defense mechanisms for avoidance and pain regulation.
•Emotional-affective modulation of cognition in pain assessment of reward vs pain is provided by the interaction between what two brain structures?
the prefrontal cortex and the amygdala
