Anatomy and Physiology of Pain

Question 1

What are the four physiological mechanisms of pain?

Answer 1

Transduction
Transmission
Perception
Modulation

Question 2

Define pain

Answer 2

Unpleasant sensation and emotional experience associated with actual or potential tissue damage, or described in terms of such damage

Question 3

What is nociceptive pain?

Answer 3

Normal, acute pain resulting from nociceptor activity

Question 4

Which is the fastest nociceptor sensory neurone?

Answer 4

Ad

Question 5

Which is the slowest nociceptor fibre?

Answer 5

C

Question 6

Which is the second fastest nociceptor fibre?

Answer 6

Ab

Question 7

What are in the membrane of nociceptors which allow responses to tissue damaging stimuli

Answer 7

receptor proteins

Question 8

Which receptor detects pH changes in skeletal and cardiac muscle relating to ischaemia?

Answer 8

ASIC3

Question 9

Why is there sometimes lack of pain fibres?

Answer 9

Shortened life span

Question 10

Which nociceptors produce sharp, fast pain?

Answer 10

Ad (+ some Ab)

Question 11

Where are nociceptors present?

Answer 11

Thermal + Mechanical

Provides precise location

Question 12

Where do Ad fibres synapse?

Answer 12

laminae I and V

Question 13

What type of pain do C fibres produce?

Answer 13

slow, burning

Question 14

What are the two types of C fibres?

Answer 14

Peptidergic fibres

Peptide poor fibres

Question 15

What do peptidergic fibres do?

Answer 15

Release peptides to produce inflammatory responses + healing

Question 16

What do peptide poor fibres do?

Answer 16

Have distinct receptors which provides mechanical nociception

Question 17

Where do C fibres synapse?

Answer 17

laminae I and II

Question 18

Where do C fibres also innervate through interneurons?

Answer 18

lamina V

Question 19

What does the spinothalamic tract pathway start + finish?

Answer 19

Sensory pathway from skin to thalamus

Question 20

Where is information from Ventral Posterolateral (VPL) of the thalamus relayed to?

Answer 20

somatosensory cortex of brain?

Question 21

Where does spinothalamic tract decussate at?

Answer 21

Level of spinal cord

Question 22

What does the lateral spinothalamic tract modulate?

Answer 22

Pain + Temperature

Question 23

Where does the lateral spinothalamic tract end?

Answer 23

Different sites of the brainstem

Question 24

What are the primary afferents of lateral spinothalamic tract?

Answer 24

C fibres and some Ad fibres

Question 25

Where are projection neurones found in lateral spinothalamic tract?

Answer 25

laminae I

Question 26

What does the lateral tract innervate?

Answer 26

more posterior and medial parts of the thalamus; MDvc, POm and VMpo

Question 27

Where does MDvc project to?

Answer 27

Anterior cingulate cortex

Question 28

What is anterior cingulate cortex responsible for?

Answer 28

emotion and motivation

Question 29

Where does posterior thalamus project to?

Answer 29

anterior/rostral insula

Question 30

What does lateral STT sub serve as?

Answer 30

Punishing aspects of pain

Question 31

What does the anterior tract modulate?

Answer 31

Pressure and touch

Question 32

What are primary afferents of Ad of anterior tract?

Answer 32

Ad fibres and some Ab and C fibres

Question 33

Where are projection neurones found for anterior tract?

Answer 33

laminae V

Question 34

What does anterior tract innervate?

Answer 34

VPL and VPM (mainly project to primary somatosensory cortex)

Question 35

What does anterior STT sub serve as?

Answer 35

Fast, discriminative aspects of pain

Question 36

What are inflammation signs of normal acute pain?

Answer 36

Heat Redness Pain Swelling

Question 37

What is peripheral sensitisation?

Answer 37

Increased sensitivity to afferent nerve stimuli

Question 38

How does peripheral sensitisation work?

Answer 38

Inflammatory mediators impact nociceptors by reducing activation threshold and increasing responsiveness

Question 39

Where does increased pain sensitivity occur?

Answer 39

directly in damaged tissue

Question 40

Where do prostaglandins work?

Answer 40

key role in inflammatory pain

Question 41

What do phospholipase A2 release and where?

Answer 41

Arachidonic acid from cell membranes

Question 42

What uses arachidonic acid as a substrate for PG synthesis?

Answer 42

COX 1 + COX 2

Question 43

Where is COX 1 found?

Answer 43

low levels tonically

Question 44

Where is COX 2 found?

Answer 44

Induced by inflammation

Question 45

How do PGs sensitise C fibres?

Answer 45

Increase number of open Na+ channels

Question 46

What do PGs also cause?

Answer 46

central sensitising effects

Question 47

What can target PGs?

Answer 47

Analgesics NSAIDs (for pain reduction)

Question 48

What is released in central sensitisation?

Answer 48

glutamate + peptides

Question 49

What releases glutamate + peptides in central sensitisation?

Answer 49

Nociceptor afferents

Question 50

What causes central sensitisation?

Answer 50

Prolonged nociceptor input

Question 51

Where does prolonged nociceptor input work on in central sensitisation?

Answer 51

dorsal horn neurones

Question 52

What is an effect of central sensitisation?

Answer 52

Increased sensitivity of dorsal horn nociceptive 2nd order neurones to inputs

Question 53

What does increased sensitivity of dorsal horn cause?

Answer 53

allodynia or secondary hyperalgesia (pain occuring in the region surrounding the damage)

Question 54

Define allodynia

Answer 54

pain from things which are not painful

Question 55

define hyperalgesia

Answer 55

heightened response

Question 56

Define chronic pain

Answer 56

Pain > 12 weeks

Question 57

What can be a characteristic of chronic pain?

Answer 57

maladaptive

Question 58

Why does chronic pain occur?

Answer 58

abnormal activity in the neural system

Question 59

What is the difference between neuropathic pain vs dysfunctional pain?

Answer 59

``` Neuropathic = injury or dysfunctional in neural system Dysfunctional = no known lesion or inflammation ```

Question 60

How do you deal with peripheral nociceptors?

Answer 60

Local anaesthetics + anti-inflammatory drugs

Question 61

How do you deal with peripheral nerves

Answer 61

Local anaesthetics

Question 62

How do you deal with dorsal root?

Answer 62

Local anaesthetics opioids A2 agonist

Question 63

How do you modulate pain in brain?

Answer 63

Opioids | A2 agonists

Question 64

What does acupuncture do?

Answer 64

Activate Ad fibres so stimulates primary pain modulation centre (PAG)

Question 65

What does PAG mediate?

Answer 65

Diffuse Noxious Inhibitory Control (DNIC) so pain inhibits pain