Neuro - PHYSIOLOGY AND PATHOLOGY OF PAIN

Question 1

what is the area over which a receptor can respond to a stimulus?

Answer 1

receptive field

Question 2

what sensation does Meissner’s corpuscule detect?

Answer 2

light touch

Question 3

what sensation do Merkle’s corpuscules detect?

Answer 3

touch

Question 4

what sensation do free nerve ending detect?

Answer 4

pain

Question 5

what sensation do Pacinian corpuscules detect?

Answer 5

deep pressure

Question 6

what sensation does Ruffini corpuscule detect?

Answer 6

warmth

Question 7

is it axons or dendrites which transmit to CNS?

Answer 7

axons

Question 8

which primary afferent fibres mediate cutaneous sensation of touch, pressure, vibration at a speed of 30-70 ms^-1? what do these fibres look like in terms of myelination and size?

Answer 8

A beta, large myelinated fibres

Question 9

which primary afferent fibres mediate cutaneous sensation of cold, “fast” pain and pressure at a speed of 5-30 ms^-1? what do these fibres look like in terms of myelination and size?

Answer 9

A gamma, small myelinated fibres

Question 10

which primary afferent fibres mediate cutaneous sensation of warmth and “slow” pain at a speed of 0,5-2 ms^-1? what do these fibres look like in terms of myelination?

Answer 10

C, non-myelinated

Question 11

what 2 primary afferent fibres mediate proprioception?

Answer 11

A alpha and A beta (ex: muscle spindles, golgi tendon organ…)

Question 12

where do primary afferent fibres enter the spinal cord? where do primary afferent fibres in the head enter the CNS?

Answer 12

dorsal root ganglia for the spinal cord, cranial nerve ganglia for the head

Question 13

what fibres are considered mechanoreceptive?

Answer 13

A alpha fibres and A beta fibres

Question 14

how do the mechanoreceptive fibres travel up the spinal cord?

Answer 14

dorsal columns on ipsilateral side

Question 15

where do the mechanoreceptive fibres synapse?

Answer 15

cuneate and gracile nuclei

Question 16

where do the 2nd order fibres carrying mechanoreceptive decussate? where do they project after this?

Answer 16

decussate in brain stem, then project to reticular formation, thalamus and cortex

Question 17

what fibres are thermoreceptive & nociceptive?

Answer 17

A gamma fibres and C fibres

Question 18

how do thermoreceptive & nociceptive fibres travel up the spinal cord?

Answer 18

spinothalamic tract on anterolateral side

Question 19

where do thermoreceptive and nociceptive fibres synapse?

Answer 19

dorsal horn of spinal cord

Question 20

where do the 2nd order fibres carrying thermoreceptive and nociceptive fibres decussate? where do the project after this?

Answer 20

decussate in midline in the spinal cord, then project to reticular formation, thalamus and cortex

Question 21

damage to dorsal columns causes loss of touch, vibration, proprioception below lesion on which side?

Answer 21

ipsilateral side

Question 22

damage to anterolateral quadrant causes loss of nociceptor & temperature sensation below lesion on which side?

Answer 22

contralateral side

Question 23

what is the ultimate termination of sensory information?

Answer 23

sometosensory cortex (S1) of the postcentral gyrus

Question 24

what local chemical mediators activate pain receptors?

Answer 24

bradykinin, histamine, prostaglandins

Question 25

what do inhibitory interneurones release? what do these do?

Answer 25

opioid peptides (endorphins), they inhibit neurotransmitter release from A gamma fibres/ C fibres to their respective 2nd order neurones

Question 26

which neurones do inhibitory interneurones attach from?

Answer 26

A beta primary afferent neurones

Question 27

what way does the cortex have of exciting the inhibitory interneurone?

Answer 27

descending pathways from PAG (peri-aqueductal grey matter) and NRM (nucleus raphe magnus)

Question 28

how do NSAIDS work as a analgesic?

Answer 28

prostaglandins sensitise nociceptors to bradykinin and prostaglandin production is inhibited (inhibition of cyclo-oxygenase which converts arachidonic acid to prostaglandins)

Question 29

how do local anaesthetics work as analgesics?

Answer 29

block Na+ AP and therefore all axonal transmission

Question 30

how do opiates work as analgesics?

Answer 30

reduce sensitivity of nociceptors, block transmitter release in dorsal horn, activate descending inhibitory pathways

Question 31

what other way is there to block pain using the fact that activation A beta fibres will activate the inhibitory interneurone inhibiting A gamma fibres and C fibres?

Answer 31

Trans cutaneous electric nerve stimulation (TENS)