Unit 7 - Pain

Question 1

pain definition

Answer 1

an unpleasant sensory and emotional experience associated with potential or actual tissue damage, or described in terms of such damage

Question 2

nociception

Answer 2

process of transmitting painful stimulus

Question 3

categories of acute pain

Answer 3

somatic

visceral

Question 4

somatic acute pain

Answer 4

superficial e.g. skin, deep e.g. connective tissue, bone etc

well localised, protective role, promote healing

Question 5

visceral acute pain

Answer 5

internal organs - distension of organs e.g. colic or inflammation e.g. appendicitis

poorly localised - less nociceptors ⇒ larger receptive fields ⇒ pain not well localised

Question 6

chronic pain

Answer 6

long term debilitating pain

altered pain perception

e.g. rheumatoid arthritis, phantom limb pain

Not protective, does not promote healing

Question 7

Aδ nociceptors

proportion of receptors

responds to…

diameter

type of pain

Answer 7

20%

respond to mechanical stimuli - tissue injury

small diameter myelinated fibres

sharp, prickling, bright, well localised pain - ouch and withdraw

Question 8

C nociceptors

proportion of receptors

responds to…

diameter

type of pain

Answer 8

80%

respond to mechanical, thermal, chemical stimuli - polymodal

small diameter unmyelinated fibres

slow, burning, aching, diffuse pain

Finger on hot surface - withdraw first - Aδ fibres activated - then slow pain by C fibre

Question 9

C fibres - type of nerve ending

ion channels located on these nerve endings

Answer 9

free nerve endings

mechanical

cold

heat

chemical noxious stimuli

Question 10

inflammatory mediators

Answer 10

act to reduce pain threshold of nerves

COX inhibitors as analgesics

Question 11

where do Aδ fibres terminate

Answer 11

lamina I and V

Question 12

where do C fibres terminate

Answer 12

lamina I and II

Question 13

lamina II

synonym

NTs associated

type of AP

Answer 13

substantia gelatinosa

modulation of pain

number of NTs released (excitatory) e.g. glutamate and substance P

EPSP - AP

Lots of interneurons that can change and modify the pain stimuli

Question 14

flexation reflex =

fibres activated

Answer 14

withdrawal from painful stimulus

Aδ activation leads to activation of excitatory and inhibitory interneurons in spinal cord

contraction of agonist muscle and withdrawal from stimulus

Question 15

anterolateral system =

Answer 15

spinothalamic tract

In order to recognise where the stimulus is coming from - fibres come from spinothalamic pathway

Question 16

parallel pain pathways - sensory

Answer 16

sensory discriminative aspects of pain

location, intensity, quality

2nd order neurons synapse in thalamus

3rd order neurons to SI and SII

Question 17

parallel pain pathways - motivational-affective dimensions of pain

Answer 17

cognitive, emotional and motor aspect of pain

2nd order neuron terminate in thalamus and brainstem - spinoreticular pathway

3rd order neurons terminate in SI and SII and onto other brain regions

3rd order neurons terminate prefrontal cortex, amygdala, hippocampus, descending pain pathway

Question 18

Answer 18

Question 19

pain experience and modulation

Answer 19

Question 20

spinal modulation of pain - interneurons

Answer 20

spinal cord contains many inhibitory transmitters that may be anti-nociceptive (interneurons) - a mix of excitatory and inhibitory

endogenous opioids

endogenous cannabinoids

NA, serotonin

GABA

tonic activity in all of these neurons

modulation by descending pain pathway

role for glial

incoming non-nociceptive transmission

Question 22

pain gate theory =

Answer 22

local projections also modulate pain transmission

Question 23

what functions as a gate

what opens and closes this gate

Answer 23

substantia gelatinoas (lamina II of spinal cord)

small unmyelinated C fibres open gate - facilitate lateral spinothalamic tract activation

large myelinated fibres (Aβ - mechanoreceptors - on the skin - ruffini etc) close gate - inhibit laternal spinothalamic tract activation

Question 24

why does rubbing or scratching help reduce pain signal

Answer 24

balance of excitatory and inhibitory processes

mediated via interneurons

rubbing, scratching, TENS (Trans Electrical Neural Stimulation)

Question 25

pain gate theory

Answer 25

Activation of spinothalamic pathway and we inhibit any inhibitory neurons that dampen down signalling at the 2nd order neuron

Question 26

how does stress modulate pain

Answer 26

acute stress decreases pain - descending inhibition

chronic stress increases pain - descending facilitation

Question 27

descending pain pathway

Answer 27

Comes from all areas of brain

Signals to periaqueductal grey - sends projections to brainstem to SC

Either inhibit or activate interneurons and influence no of APs generated in ascending pathway

Question 28

brain modulation of nociceptive transmission

Answer 28

Question 29

referred pain

Answer 29

Somatic and visceral pain receptors

Visceral are not as prevalent but will innervate the SC at the same level

Activate ascending projections

We feel pain

Question 30

Answer 30