somatosensory function

Question 1

what does nociception provide, and what does the brain perceive this as

Answer 1

information about noxious (unpleasant or harmful) stimuli, which the brain perceives as pain

Question 2

difference between nociceptive stimuli and pain

Answer 2

nociceptive stimuli can be measured, pain is subjective

Question 3

suscpetibility of pain to contextual influences vs other modalities

Answer 3

pain is much more susceptible

Question 4

where are nociception sensory neurone cell bodies

Answer 4

in peripheral nervous system (dorsal root ganglion for body or trigeminal ganglia for face)

Question 5

what are the 2 nociception axon types

Answer 5

AB, C

Question 6

what are AB nociception axon types used for, and features of transmission

Answer 6

mechano- or thermoreceptor; faster, produces sharp pain, leads to avoidance

Question 7

what are C nociception axon types used for, and features of transmission

Answer 7

chemoreceptor (eg. bradykinin, histamine); produces dull aching pain, leads to guarding to allow recovery

Question 8

size of nociception receptive fields

Answer 8

usually large

Question 9

what is nociception intensity coded by

Answer 9

frequency of firing

Question 10

basic central spinothalamic tract pathway: what is information conveyed via

Answer 10

VPL (ventral posterolateral) and VPM (ventral posteromedial) nuclei of thalamus

Question 11

basic central spinothalamic tract pathway: where is information conveyed to and why

Answer 11

SI and SII cortex, for analysis of localisation and intensity of the noxious stimulus

Question 12

collateral branches to brainstem of spinothalamic tract pathway: where is information conveyed to and why

Answer 12

forebrain structures, for perception of pain (afferent pathway)

Question 13

collateral branches to periaqueductal grey of midrain of spinothalamic tract pathway: function

Answer 13

inhibit pain (central inhibition pathway)

Question 14

in central spinothalamic pathway, where is somatotropic organisation maintained

Answer 14

through entire pathway from dermatomes to cortex

Question 15

where does decussation of the pathway for information coming from the body occur

Answer 15

in spinal cord

Question 16

where does decussation of the pathway for information coming from the head occur

Answer 16

in brainstem

Question 17

afferent pain pathway (spinothalamic tract/spinal lemniscus) from face

Answer 17

face nociceptor-> primary sensory neurone -> through posterior pons down to medulla oblongata-> lateral synapse and decussation as secondary sensory neurone -> pass up through pons and midbrain -> thalamus -> tertiary sensory neurones -> somatosensory cortex

Question 18

afferent pain pathway (spinothalamic tract/spinal lemniscus) from upper limbs

Answer 18

upper limb nociceptor -> primary sensory neurone -> posterior cervical cord-> synapse and decussation as secondary sensory neurone -> up spinothalamic tract through medulla oblongata, pons and midbrain -> thalamus -> tertiary sensory neurones -> somatosensory cortex

Question 19

afferent pain pathway (spinothalamic tract/spinal lemniscus) from lower limbs

Answer 19

lower limb nociceptor -> primary sensory neurone -> posterior lumbar cord-> synapse and decussation as secondary sensory neurone -> up spinothalamic tract through medulla oblongata, pons and midbrain -> thalamus -> tertiary sensory neurones -> somatosensory cortex

Question 20

where do spinothalamic tract axons send collateral branches to

Answer 20

brainstem (reticular formation), thalamus (intralaminar nuclei), hypothalamus and some cortex (e.g. cingulate gyrus, insula)

Question 21

2 effects of axon collateral branches sent from spinothalamic tract

Answer 21

triggers increase in awareness, registers unpleasantness of stimulus i.e. pain

Question 22

nociceptive dysfunction: effect of pathway disruption on pain and injury predisposition

Answer 22

may reduce pain, but predisposes to increased injury

Question 23

nociceptive dysfunction: 3 changes which may exacerbate pain

Answer 23

windup in dorsal horn, thalamic syndrome, phantom pain

Question 24

nociceptor fibres: Ad effect and stimuli (type 1 and type 2)

Answer 24

mediate sharp, intense or fast pain; type 1: noxious mechanical; type 2: noxious heat

Question 25

nociceptor fibres: C fibres effect and stimuli

Answer 25

mediate dull, aching or second pain; noxious thermal, mechanicl and chemical stimuli

Question 26

spinal cord nociceptive process: first synapse of pain pathway neurotransmitter

Answer 26

glutamate

Question 27

sensory component of pain tract

Answer 27

lateral spinothalamic tract

Question 28

emotional component of pain tract

Answer 28

spinoreticular tract (passes through parabrachial area)

Question 29

functional MRI cerebral signature of pain: cortex

Answer 29

SI, SII, insula cortex, anterior cingulate cortex, prefrontal cortex

Question 30

functional MRI cerebral signature of pain: other brain areas

Answer 30

amygdala, cerebellum, brainstem

Question 31

nociceptive vs neuropathic pain

Answer 31

nociceptive: noxious stimulation of a nociceptor; neuropathic: lesion or disease of somatosensory system; can be mixed e.g. osteoarthritis and lower back pain

Question 32

effect of peripheral sensitisation to pain (“inflammatory soup”)

Answer 32

decrease thresholds to peripheral stimuli at site of injury

Question 33

3 effects of central sensitisation to pain (“inflammatory soup”)

Answer 33

decrease thresholds to peripheral stimuli at adjacent site of injury, expansion of receptive field, spontaneous pain

Question 34

define hyperalgesia, with reference to primary and secondary; effect on normal pain response sigmoid curve

Answer 34

increased pain from stimulus that normally provokes pain (usually thermal or mechanical); primary occurs at area of injury or noxious chemical, secondary occurs around that primary area (shift to left vs normal pain response, at higher stimulus and pain intensity)

Question 35

define allodynia; effect on normal pain response sigmoid curve

Answer 35

pain due to stimulus that does not normally invoke pain (shift to left vs normal pain response, at lower stimulus and pain intensity)

Question 36

3 neuropathic pain sensory profiles

Answer 36

sensory loss, thermal hyperalgesia, mechanical hyperalgesia

Question 37

descending control and chronic pain: inhibition vs facilitation endogenous drugs

Answer 37

inhibitory (protective): noradrenaline; facilitatory (harmful): serotonin

Question 38

state of descending control in chronic pain patients

Answer 38

impaired

Question 39

neuromodulation in chronic pain patients: what is done and how does it work

Answer 39

non-invasive primary motor cortex stimulation, activating endogenous analgesic systems in brain (periaqueductal grey and anterior cingulate cortex)