Sensory physiology of pain

Question 1

what are the two dimensions of pain?

Answer 1

1. sensory discrimination - perception of external or internal noxious information and localization of the site 2. motivation affective - emotional and sympathetic responses and associated (learning) behaviors

Question 2

initial superficial pain is carried by what type of fibers?

Answer 2

Ad

Question 3

superficial delayed pain is carried by what type of fibers?

Answer 3

C

Question 4

visceral pain is carried by what type of receptors?

Answer 4

C

Question 5

what are transient receptor potential families?

Answer 5

group of receptors that allows for influx of sodium and calcium upon activation, thus initiating a receptor potential

Question 6

what are activators of chemical stimuli?

Answer 6

1. potassium 2. low pH 3. substance P 4. bradykinin

Question 7

what are sensitizers of chemical stimuli?

Answer 7

1. prostaglandins 2. leukotrienes 3. ATP 4. other mediators of inflammation

Question 8

where are silent nociceptors primarily found?

Answer 8

viscera

Question 9

what do silent nociceptors respond to best?

Answer 9

inflammation

Question 10

what is primary hyperalgesia?

Answer 10

increased sensitivity to noxious and non-noxious stimuli in the area immediately surrounding the primary site of damage due to a sensitization of the peripheral nociceptors

Question 11

what is the main cause of primary hyperalgesia?

Answer 11

sensitization of peripheral nociceptors by chemical substances

Question 12

where are the spinothalamic neurons located? what type of information do they relay?

Answer 12

1. lamina I and V of dorsal horn 2. non-noxious sensory information conveyed by Aa and AB fibers 33. noxious mechanical sensory information conveyed by Ad fibers 4. noxious sensory information conveyed by C fibers

Question 13

the spinothalamic neurons in which dorsal horn lamina are considered nociceptive specific?

Answer 13

II and III - receive only noxious input

Question 14

what are wide dynamic range neurons?

Answer 14

spintothalamic neurons in lamina V that receive both non-noxious (Aa and AB) and noxious (Ad and C) input

Question 15

what are the NTs for the primary afferent inputs (Ad and C)?

Answer 15

1. substance P 2. glutamate 3. neurokinin A

Question 16

glutamate activates what receptor(s) in the spinal neuron?

Answer 16

AMPA and NMDA

Question 17

what allows glutamate to act on NMDA receptors?

Answer 17

substance P

Question 18

what is the result of opening NMDA channels?

Answer 18

long lasting depolarization of post synaptic membrane, making neuron more easily excitable and opening voltage sensitive calcium channels (increasing sensitivity)

Question 19

what is the wind up phenomenon?

Answer 19

increased neuronal sensitivity due to increased intracellular concentration of calcium, elaborating more AMPA and NMDA glutamate receptors

Question 20

what is the proposed cause of secondary hyperalgesia?

Answer 20

change in responsiveness of spinothalamic neurons mediated by substance P and glutamate

Question 21

definition: allodynia

Answer 21

pain resulting from a non-noxious stimulus, produced by facilitation of second order neuron responsiveness to non-noxious stimuli through the wind up or similar phenomenon elicited from intense noxious input

Question 22

what responses are associated with the paleospiniothalamic tract?

Answer 22

increased arousal, affective and autonomic responses (affective motivation pathway)

Question 23

what responses are associated with the neospinothalamic tract?

Answer 23

localization, quality, and type of pain (sensory discrimination pathway)

Question 24

what areas of the brain are crucial and consistent sites for pain perception with regards to noxious stimuli?

Answer 24

1. anterior cingulate gyrus 2. insular cortex

Question 25

which area of the brain appears to be predominantly involved in producing anti-nociception (analgesia) by descending pain controlling mechanisms?

Answer 25

periaqueductal gray

Question 26

what NT is used by the descending raphe system?

Answer 26

serotonin

Question 27

what NT is used by the locus coeruleus?

Answer 27

NE

Question 28

what is the gate control theory of pain?

Answer 28

1. low threshold, faster conducted mechanoreceptor activation (Aa and AB fibers) enhances the activity of an inhibitory interneuron which reduces excitability of the pain conveying spintothalamic and spinoreticulothalamic projection neurons 2. Aa and AB input arrives at the inhibitory interneuron faster than Ad and C fibers