22

Question 1

define plasticity in terms of pain pathway

Answer 1

plasticity is the ability of the pain sensing system to change in response to input

Question 2

define allodynia

Answer 2

stimuli that would not normally be painful is felt as painful

Question 3

clinical implications of “sensitization”

Answer 3

1. once pain is established, analgesic drugs become less effective2. with constant input over time, the pain felt by the animal increases

Question 4

generalized pain pathway

Answer 4

conscious experience (requires integration w brain)Nociception initiates pathway through detection of tissue damage and inflammatory mediators (peripheral sensitization)TRANSDUCTION: transformation of peripheral stimulus into action potentials (depolarization of nerve)TRANSMISSION: the afferent signal is conveyed to dorsal horn of the spinal cord (via laminae)MODULATION: Processing of signs at the dorsal horn (either amplifies or suppresses signal)PROJECTION: signal taken to brain/brainstem(spinothalamic tract)PERCEPTION: cerebral cortex (thalamic or cortical level)

Question 5

major classes of nociceptors

Answer 5

A delta: medium (1-5 microns), myelinated, mediate ACUTE fast well localized painA beta: larger, rapidly conducting myelinated fibers that respond to innocuous mechanical stimuliC-fiber: small (0.25-1.5 microns), UNMYELINATED, mediate poorly localized slow pain, HI threshold, POLYmodal

Question 6

T/Fmost nociceptores are relatively nonselective ion channels

Answer 6

TRUENOT stimulated by voltage but rather STIMULUS (temp, chemical, mechanical forces)

Question 7

define polymodal nociceptors

Answer 7

fibers or nociceptors that respond to MULTIPLE types of noxious stimuli (temp, chem, mechanical)

Question 8

T/FMost C fibers are high threshold and poly modal

Answer 8

TRUEMost C fibers are high threshold and poly modal (heat and mechanical)

Question 9

heat vs cold sensitive receptors in C fibers

Answer 9

Heat: TRPV-1Cold: TRPM-8

Question 10

where are A beta nociceptors located

Answer 10

A beta: larger, rapidly conducting myelinated fibers that respond to innocuous mechanical stimuli (ie. light touch)innervate MERKEL CELLS, PACINIAN CORPUSCLES, HAIR FOLLICLES

Question 11

receptive field of C fibers

Answer 11

large receptive field compared to A delta fibersThis contributes to the poorly localizing, burning, gnawing sensation that persists

Question 12

conduction speeds of A delta vs C fibers

Answer 12

A delta: FAST 5-30 m/secC fiber: SLOW 0.5-2.0 m/sec

Question 13

where does the analgesic effect of cold considered to originate from

Answer 13

much of the analgesic effect of cold is considered to originate due to the Inactivation of Na channels

Question 14

what voltage gated ion channel is a target for local anesthetics

Answer 14

voltage gated SODIUM channelsinvestigation into Na1.7 voltage gated channel blockers for analgesics

Question 15

Sensory information from the head enters the CNS via _____________nerve

Answer 15

Trigeminal nerveand then relayed to the nucleus caudalis–>thalamus and reticular formation

Question 16

discrete laminae in which the spinal afferent neuron travels to the dorsal cord A delta vs C fiber

Answer 16

during transmission to dorsal horn A delta fibers travel and terminate in laminae 1 and 5C fibers travel and terminate in laminae 1 and 2

Question 17

what are three pathways that control descending modulation of sensory input or modulate the pain response

Answer 17

1. periaqueductal grey matter of midbrain (send descending excite or inhibit influences)2. rostroventral medulla and pons in brainstem (on, off cells)3. thalamocortical structures

Question 18

main excitatory neurotransmitters released from1. brief, infrequent noxious stimuli2. frequent, severe stimuli of damaged tissue

Answer 18

1. glutamate2. substance P

Question 19

unique activity of substance P on NMDA receptor activation

Answer 19

neuropeptide/neurokinin/tachykininproinflammatory/excitatoryremoves the Mg block on NMDA receptors to allow for glutamate to activate NMDA receptors (with repeated stimulation and prolonged depolarization->windup pain)

Question 20

clinical expression of central sensitization

Answer 20

1. incr response to stimuli (hyperalgesia)2. expansion of receptive fields of peripheral nociceptors ( may see allodynia)3. incr in spontaneous activity (spontaneous pain)4. neuroplasticity (pain memory–phantom pain)

Question 21

3 important concepts of central sensitization

Answer 21

1. NMDA excitatory activity2. Loss of GABA-ergic and glycinergic inhibitory controls3. Glial-neuronal interactions (peripheral nerves are also damaged and release mediators)

Question 22

two inhibitory NT

Answer 22

glycineGABA

Question 23

the initial negative impact of surgical trauma and pain transmission is activation of _____________

Answer 23

sympathetic nervous system (sympathoadrenal and corticomedullary)release of catecholamines (changes metabolism, perfusion, CO, increases oxygen consumption, etc)

Question 24

categories to assess pain in animals based on Glasgow

Answer 24

1. posture2. restlessness3. vocalization4. attention to wound5. demeanor6. gait and ease to rise7. RESPONSE TO PALPATION

Question 25

define preemptive analgesia

Answer 25

strategy that has the power to deter or prevent anticipated unpleasant situation or occurrencebased on preventing nociceptive input to the CNS to prevent central sensitization and post injury hypersensitivity

Question 26

what is the only true way post injury hypersensitivity be prevented?

Answer 26

presurgical (preemptive) analgesia ALONG WITHintrasurgical AND post surgical analgesiapreemptive analgesia alone will not rid all pain post injury

Question 27

Lascelles et al prospective double blinded control on timing of NSAIDs and injury in OHE model

Answer 27

found that preoperative carprofen was most effective in controlling pain in OHE dogs

Question 28

study or pre vs post laparotomy infiltration with bupivicaine

Answer 28

PREincisional bupivicaine infiltration was superior

Question 29

7 therapeutic modalities used to decr pain and inflammation in vet patients

Answer 29

1. local hypo and hyperthermia2. pROM3. massage4, therapeutic exercise5. hydrotherapy6. US7. electrical stimulation

Question 30

define and give advantages of multimodal (balanced) analgesia

Answer 30

combining drugs with different MOA1. decr dosages–>decr side effects2. synergistic effects

Question 31

what areas of the pain pathway do local anesthetics work(figure 22-8 pg 246)

Answer 31

1. modulation at the trauma site2. modulation at the peripheral nerve3. modulation of the dorsal horn

Question 32

what area(s) of the pain pathway do antiinflammatories work(figure 22-8 pg 246)

Answer 32

1. modulation at the trauma site

Question 33

what areas of the pain pathway do opioids and alpha 2 agonist work(figure 22-8 pg 246)

Answer 33

1. modulation at the dorsal horn2. modulation at higher centers (brain)

Question 34

what areas of the pain pathway do 5-HT, NE, Opiodergic work(figure 22-8 pg 246)

Answer 34

descending modulation (via PAG, RVM)