Pain Transmission

Question 1

pain

Answer 1

unpleasant sensory and emotional experience associated w/ actual or potential tissue damage or described in terms of such damage

Question 2

hyperalgesia

Answer 2

magnification of pain perception to normally minimally painful stimuli

Question 3

allodynia

Answer 3

perception of pain to normally non painful stimuli

Question 4

hyperesthesia

Answer 4

magnified sensation of any type

Question 5

dysesthesia

Answer 5

distorted, magnified and unpleasant sensation to normal stimulation

Question 6

neuropathic pain

Answer 6

generated by or magnified by disorders of neural tissue

Question 7

nocioceptive pain

Answer 7

mostly acute

high threshold mechanoreceptors- usually free nerve endings

also react to chemicals- tissue metabolites, transmitters, tissue cell products, inflammatory mediatiors

Question 8

pain afferent fibers

Answer 8

either Adelta or C fibers

slow conducting
slow adapting

transmitters- substance P, neurokinin A

release transmitters on both ends of axon- neurogenic inflammation

Question 9

why isnt pain input focused in the spinal cord

Answer 9

distribute over 4-8 segments

Question 10

central terminals

Answer 10

initial termination is in dorsal horn - substantia gelatinosa

c fibers terminate in layer 1 or layer 5

cells from layer 1 transmit stinging pain, sharp. dont encode intensity

cells from layers 4,5 respond to intensity, but not location

these go up spinothalamic tract

A-beta fibers (normal touch) terminate in 3 and 4

Question 11

neospinalthalamic tract

Answer 11

spinothalamic tract

decussate in ventral commissure in cervical cord

reach ventral posterolateral nucleus of thalamus (VPL)

most direct pathway

Question 12

paleospinothalamic pathway

Answer 12

most of projections are from WDR neurons

terminates in nonspecific thalamic nuclei that project broadly over cortex

can affect many areas of the cortex including those involved w/ mood, attnetion, etc

Question 13

spino-reticulo-thalamic pathway

Answer 13

collateral branches terminate in the brainstem resulting in changes in autonomic activity

ie- sweating, paleness, tachycardia, etc

Question 14

referred pain

Answer 14

caused by convergence of pain inputs on highly convergent cells

common in head b/c of convergence of trigeminal nerve

Question 15

how does pain produce muscle spasms?

Answer 15

reflexes mediated by interneurons produce withdrawals reflexes d/t pain

Question 16

causes of chronic pain

Answer 16

chronic inflammation

damaged peripheral nerves causing increased Na channel expression

potentiation of synapses

Question 17

long term potentiation

Answer 17

caused by increased intracellular Ca d/t activation of NMDA receptors

at higher levels of stimulation, brain neurotrophic growth factor is also released, which act on tyrosine kinase and enhance synaptic conductivity

Question 18

how can you modify acute pain

Answer 18

anti inflammation

inhibit pain nerve fiber

activate large diameter sensory axons

activate receptor that block transmission

Question 19

why does rubbing help prevent pain

Answer 19

activates A-beta sensory fibers that synapse on inhibitory interneurons that block pain signals

Question 20

how can you modify chronic pain

Answer 20

control inflammation

inhibit pain nerve fiber

activate large diameter sensory axons

activate systems that block transmission

Question 21

descending pain control system

Answer 21

act thru descending serotonin and norepi pathways

activated by periacqueductal gray

Question 22

modifying neuropathic pain

Answer 22

activation of serotonin systems- antidepressants

activation of norepi systems- SNRI

altering voltage gated calcium channels- anti convulsants

Question 23

thalamic pain syndrome

Answer 23

injury to thalamus deactivates inhibitory neurons and allow sensation of more pain

Question 24

suffering

Answer 24

affective components of pain mediated by frontal lobe and anterior cingulate gyrus

Question 25

cingulate cortex

Answer 25

most active on the border of pain- deciding how to react