BMS11004 WEEK 11 - TUESDAY

Question 1

define specificity theory

Answer 1

pain is a distinct sensation, detected/transmitted by specific receptors to distinct brain area

Question 2

define convergence theory

Answer 2

pain is integrated, plastic state represented by pattern of convergent somatosensory activity within distributed network (neuromatrix)

Question 3

what type of fibre (a, b, y) are lightly myelinated nociceptors, what modality are they, how fast

Answer 3

Aδ (alpha delta)
fast (20m/s)
mechanosensitive, mechanothermal-sensitive

Question 4

what type of fibre (a, b, y) are unmyelinated nociceptors, what modality are they, how fast

Answer 4

C fibre
slow (2m/s)
polymodal= mechanical, thermal, chemical

Question 5

when are nociceptors most easily demonstrated

Answer 5

in heat response- find afferent whose activity correlate with pain perception

Question 6

what fibre types mediates fast pain

Answer 6

sharp, immediate
mimicked by direct stimulation of Aδ (delta) fibre nociceptors

Question 7

what fibre types mediates slow pain

Answer 7

diffuse, delayed, long-lasting
mimicked by stimulating C fibre nociceptors

Question 8

when you cut yourself, what nociceptors activate

Answer 8

first sharp pain = Aδ
replaced by long dull pain = C fibres

Question 9

what are molecular pain receptors

Answer 9

specific molecular receptors associated with nociceptive nerve endings and activated by heat, hot chillis

Question 10

capsaicin receptor (TRPV1) is a specific molecular receptor. describe what fibres it is activated in, how

Answer 10

activated in nociceptive Aδ and C fibres at 45c by capsaicin (vanilloid, active component in chilli)

Question 11

name the 2 ways that molecular receptors can respond in pain

Answer 11

responds to heat directly and fire
capaicin can bind and cause it to fibre

Question 12

name the 2 components of central pain pathways

Answer 12

sensory discriminative - signals location, intensity, stimulus type (involve spinothalamic tract)
affective motivational- signal unpleasant, enables fight/flight autonomic response

Question 13

what is spinothalamic tract also known as

Answer 13

anterolateral system

Question 14

explain topological maps of pain

Answer 14

topologically represented in cortex, region responding to painful stimulus and response correlates to pain intensities

Question 15

explain what brain areas are linked to affective-motivational response to pain

Answer 15

insula, cingulate cortex (limbic system)

Question 16

explain topographical maps of affective-motivational pathway, and locations

Answer 16

little mapping
share pathways with anterolateral system
neurons in paracrachial nucleus respond from any body surfaces

Question 17

what is hyperalgesia

Answer 17

increased response to painful stimuli (hypersensitivity of damaged skin to normally tolerable pain stimulus eg: pin prick)

Question 18

what is allodynia

Answer 18

painful response to normally innocuous stimulus (painful sensitivty of subburnt skin to brush)

Question 19

what is hyperalgesia due to, and peripheral effects

Answer 19

lowered nociceptor threshold
damaged tissue releases inflammatory substances, affecting nerve function, attract mast cell, neutrophils, increase blood flow

Question 20

what are prostaglandins (inflammatory response in hyperalgesia)

Answer 20

lower threshold for AP generation
in analgesic painkillers

Question 21

what is hyperpathia

Answer 21

variant of hyperalgesia/allodynia
due to fibre/axonal loss/damage
cause raised detection threshold, when exceeded causes explosive pain
can occur when central pathway damaged- shingles, diabeters, MS, stroke

Question 22

when is neuropathic pain experienced

Answer 22

post amptutation

Question 23

what can phantom limb pain suggest regarding central representations

Answer 23

illusion of limb being present
suggest central representation of body isnt passive, and occur when born without limb suggesting central map pre-formed

Question 24

what is referred pain

Answer 24

due to damage in viscera, perceived as coming from specific location according to location of organ eg: heart attack in shoulder
reflect convergence of visceral afferent onto pathway as cutaneous afferent in CNS
useful in clinical diagnosis

Question 25

what does stimulation of PAG do

Answer 25

activates brainstem nuclei modulating activity in dorsal horn neurons
activating enkephalin releasing interneurons, presynaptically inhibiting nociceptive fibres

Question 26

why does rubbing injury (modulation) work

Answer 26

locally inhibit mechanoreceptive (A-beta fibres) of nociceptive (C fibres) in spinal cord
suggests pain perception due to integration of convergent sensory info