Pain II Flashcards by tcarlso 3

What is the difference between primary and secondary hyperalgesia?

Primary = in the periphery
Secondary = at the spinal cord

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What are the two fibers that play a role in nociception?

A-delta

C fibers

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What is the role that a-delta fibers play a role in? What do they respond to?

Sharp, first pain

Respond to intense mechanical

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What is the role of the C fibers? What do they respond to?

Mediate poorly localized, diffuse secondary pain

Polymodal response

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What are the three fiber types that are activated in response to pain, in order?

A-alpha
A-delta
C fibers

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What are the fibers that are found in the cutaenous tissue?

A-delta

C fiber

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What are the fibers that are found in the joints?

A delta
C fibers (more here)

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Which are more prominent in joints: c fibers or a delta?

C fibers

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What are the types of fibers found in muscles?

Similar to joint:

A-delta and C fibers, with x2 more C fibers

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What are the types of fibers found in visceral structures?

C fibers

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Where does spinal modulation occur?

Dorsal horn of the spine (substantia gelatinosa)

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What is the route of innervation of pain (second and first order neurons)?

Spinothalamic pathway

DRG, then substantia gelatinosa, anterior white commissure, and up to the thalamus

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What are the fibers found in lamina I and V? What type of pain is this associated with?

A-delta fibers–fast, acute pain

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What are the fibers that are found in lamina V? What type of stimuli do these respond to?

Wide dynamic range fibers

Respond to noxious and non-noxious stimuli

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What are the fibers that are found in lamina II and III? What type of pai is this associated with?

C fibers–slow, chronic pain

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What are the wide dynamic range fibers? What fibers do they synapse with?

Polymodal neurons in lamina V that respond to A-alpha, A-beta, A-delta , and C fibers

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What is the major neurotransmitter that is involved in pain transmission?

Glutamate

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What are the receptors that respond to glutamate? Which response to substance P?

AMPA and NMDA receptors

NK1 for substance P

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Which fiber type has the lowest threshold?

A-beta fibers

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What is secondary hyperalgesia?

Prolonged and increased activation of nociceptors in the periphery and projection pathways at the spinal cord

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What is the molecular basis for central sensitization or secondary hyperalgesia? (what is the primary neurotransmitter/receptor combination involved in the pain pathway? What happens to the receptor when the signal is prolonged/strong enough?)

Pain signal from neurons releases Glutamate, which activates AMPA receptor.

AMPA receptor will activate NMDA receptor, causing rush of Ca into cell, and “wind up”

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What is neuronal plasticity?

Modulation of intracellular signaling and changes in gene expression

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What is the chemical basis for chronic pain?

Exaggerated release of glutamate and substance P that results in increased gene expression of pain signals

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What is allodynia?

Pain resulting from a non-noxious stimulus (sunburn)

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What are the fibers in the DC/ML pathway? (1)

A-beta

What are the fibers in the AL system? (2)

C fibers and A-delta fibers

What is the major pathway that pain travels through? What type of fibers are utilized here?

Neospinothalamic tract--a-delta fibers

Where does the neospinothalamic tract arise from, and terminate?

Arises from lamina I, IV, V goes to VPL nucleus of the thalamus

Where does the VPL nucleus of the thalamus send projections to?

Primary somatosensory cortex

What type of information travels through the neospinothalamic tract?

Sharp pain, with sharp localization

What type of fibers are utilized by the paleospinothalamic tract?

C fibers

Where does the paleospinothalamic tract begin and terminate?

Begins in Lamina II, III, V Ends in the limbic system

What type of pain information comes from the paleospinothalamic tract? What is the quality of pain sensed through this tract?

Emotional response to pain Dull, throbbing pain

What is the function of the spinoreticular tract?

Descending pain control and motor response

What is the function of the spinomesencephalic tract?

Descending pain control Regulates pain experience

What is the function of the superior colliculus with the spinomesencephalic tract?

eye movement toward site of injury

What is the tract that is utilized for the sensory/discriminative component of pain?

Neospinothalamic tract

What is the tract the is utilized for the emotional component of pain?

Paleospinothalamic tract

What is the route of innervation from the VPL nucleus of the thalamus to the prefrontal cortex? (5)

1. Primary somatosensory 2. Somatosensory association cortex 3. Insular cortex 4, Anterior cingulate cortex 5. prefrontal cortex

What is the function of the anterior cingulate cortex in pain?

Attention part of the pain

Where do signals that go from the spinal cord to the amygdala go?

Prefrontal cortex

Where do signals that go from the spinal cord to the dorsomedual nucleus thalamus go?

Anterior cingulate gyrus to prefrontal cortex

What are the five things that the pain matrix contributes to pain?

1. Threatening visual and auditory cues 2. Memory of pain 3 Anticipation 4. Attention 5. Empathy with others

What are the two areas in the brain that are most active during pain and are the main parts of the pain matrix?

Insula and anterior cingulate cortex

When is the ACC active in pain? (3)

Perception of pain Imagining pain Observation of pain

What is the function of the insula in pain?

Relay station to the limbic system and hypothalamus

What is the gate control theory? How does it work?

C fibers can be deactivated by competition from the A beta fibers because A beta fibers are faster, and stimulate an inhibitory interneuron

What are the three areas of the brain that are a part of the descending pain control?

1. Periaqueductal gray 2. Rostral ventral medulla 3. Locus coeruleus -pons in brainstem

What drugs utilized the descending pathway of pain control?

Opioids

What is the role of the amygdala in pain perception?

Assigning a negative context to pain

What is the role of the prefrontal cortex in the pain pathway?

Cognitive experience of pain

What is the nucleus in the pons that plays a role in descending pain control?

Nucleus raphe magnus

What is the role of the ventrolateral PAG?

Sympathetic inhibition

What is the role of the dorsal PAG?

Sympathetic excitation--prepares for fight or flight

Which is blocked by naloxone: the ventrolateral or the dorsal PAG?

Ventrolateral

What is the MOA of the ventrolateral PAG?

Nonselective inhibition of A and C fiber input

What is reflective pain?

Pain that is Perceived at a location other than the site of the painful stimulus

What is convergence of pain?

somatic and visceral pain fibers converge on the same secondary afferents in the dorsal horn, causing referred pain

What is projected pain?

Stimulation of a nerve along its path, causing pain in the areas that is innervates distally (hitting ulnar nerve at the medial epicondyle of the humerus

What is the MOA of phantom pain?

Reorganization of the neurons in the spinal cord or brain

What is complex regional pain syndrome?

Continuous burning pain long after seemingly trivial injuries

What is the treatment for complex regional pain syndrome?

Sympathectomy or sympathetic nerve block

What is central pain? What type of pain is this characterized as?

‘pain’ originating from a central process. A form of | neuropathic pain.

What are the symptoms of thalamic pain?

Severe pain to the entire contralateral side of the body

What are the nociceptive specific neurons?

Neurons in laminas I, II, and III that receive only noxious input

Which is wider: primary or secondary hyperalgesia?

Secondary

What is the "wind up" phenomenon?

Activation of the NMDA receptor, causing Ca to rush in and activate lots of pain stuff

What is the cause of allodynia?

WInd up effect

What is the MOA of opioids?

Release of met-enkephalin on the presynaptic spinothalamic neurons, to reduce excitability

Which is more laterally located: the neospinothalamic tract, or the paleospinothalamic tract? Which has a smaller receptive field?

Neospinothalamic (for both)

True or false: the DC/ML pathway has nothing to do with pain, only discriminative touch and proprioception

False--carries visceral pain

The nucleus Raphe uses what neurotransmitter?

5HT

The locus ceruleus uses what neurotransmitter?

What is the MOA of the locus ceruleus and Raphe nucleus in the descending pain control system?

Activate inhibitory neurons in the spine

What is the role the PAG plays in the descending pathway?

Activates the Raphe and Locus Ceruleus

What is the gate control theory of pain?

Fast conducting mechanoreceptor activation stimulates an inhibitory interneuron with the primary afferents (a-delta and C fibers) pathway

What is projected pain?

Pain produced by irritation of a axon at an ectopic site (like hitting funny bone)

What is the basis for phantom limb pain?

reorganization of the somatosensory cortex and probably other subcortical areas, including the spinal cord

What is sympathetic mediated pain?

continuous burning pain that may develop following a | traumatic peripheral injury.

What is required to develop sympathetic mediated pain?

Intact SNS

What is the basis for Sympathetic Mediated Pain (SMP)?

tonic release of NE by a damaged sympathetic fibers can activate/sensitize the nociceptors eliciting ‘pain’