Lecture 27 Physiology and Pathophysiology of Pain

Question 1

Define pain

Answer 1

unpleasant sensory and emotional experience which we primarily associate with tissue damage or describe in terms of such damage or both

Question 2

Define Nociception

Answer 2

The detection of tissue damage by specialised transducers connected to A-delta and C fibres

Question 3

What do A-delta and C fibres respond to

Answer 3

Thermal, chemical, mechanical and noxious stimuli

Question 4

Describe the myelination of the primary afferents

Answer 4

A alpha and A beta- myelinated
A delta- lightly mtelinated
C fibres- not myelinated

Question 5

Describe the diameter of the primary afferent fibres

Answer 5

A alpha and A beta- large
A delta- medium
C fibre- small

Question 6

What doe A alpha and A beta respond to

Answer 6

Proprioception and light touch

Question 7

What does A delta respond to

Answer 7

Nociception (mechanical, thermal, chemical)

Fast pain or sharp pain

Question 8

What does C fibres respond to

Answer 8

Innocuous temperature, itch
Nociception (mechanical, thermal, chemical)
Dull second pain after someone pinches you

Question 9

What does the grey matter in the spinal cord represent

Answer 9

Neurons

Question 10

What doe the white matter in the spinal cord represent

Answer 10

Nerve tract arising from the neurone r descending neurone in the brain

Question 11

What is the grey matter divided into

Answer 11

Ventral, lateral and dorsal horn

Question 12

What layer of the grey matter are nociceptive neurons located

Answer 12

1 & 2 receiving inout from A delta and C fibres

Question 13

Name Ascending Tracts (sensory)

Answer 13

Dorsal columns

Spinothalmic Tract

Question 14

Name Descending Tracts (Motor)

Answer 14

Lateral Corticospinal Tract

Ventral Corticospinal Tract

Question 15

Where does the spinothalmic tract lead to

Answer 15

Major tract sending impulses to thalamus

Question 16

Where are the cell bodies of the spinothalmic tract located

Answer 16

Rexed lamina 1,2&5

Question 17

Where does the spinothalmic tract feed to

Answer 17

Somatosensory cortex to facilitate spatial, temporal and intensity discrimination of painful stimulus

Question 18

Name the second relay station in the brain

Answer 18

Thalamus

Question 19

What does the thalamus connect with

Answer 19

Cortex
Limbic system
Brainstem

Question 20

What is located in the medial part of the pain matrix

Answer 20

Amygdala
Hippocampus
Cigulate cortex
Insula
Prefrontal cortex

Question 21

What is located at the lateral aspect of the pain matrix

Answer 21

Somatosensory cortex and Basal ganglia

Question 22

What is usually the function of the descending pathways

Answer 22

Decrease pain signal

Noradrenergic system

Question 23

Where does pain modulation happen

Answer 23

Each level of pain transission

Question 24

Outcomes of sensitisation

Answer 24

Hyperalgesia
Primary hyperalgesia
Primary hyperalgesia
Allodynia

Question 25

Name the types of pain modulation

Answer 25

* Peripheral sensation * Central sensitisation * Gate control theory * Descending control

Question 26

What changes occur in the Nociceptor in Allodynia

Answer 26

Decreased threshold for response

Question 27

What changes occur in the Nociceptor in Hyperalgesia

Answer 27

Exaggerated response to normal and supernormal stimuli

Question 28

What changes occur in the Nociceptor in Spontaneous pain

Answer 28

Spontaneous activity in nerve fibres

Question 29

Describe the resting state in gate Control Theory

Answer 29

Firing of C fibre indirectly inhibits the inhibitory neurone and increases the chances the projection neurone will fire

Question 30

Describe the firing stage in the Gate Control Theory

Answer 30

Firing of the Aβ fibres activates the inhibitory interneuron, reducing the chances that the projection neuron will fire, even in the presence of a firing nociceptive fibre

Question 31

What is central sensitisation

Answer 31

``` • It is the response of second order neurons in the CNS to normal input both noxious & non-noxious • 3 main components o wind-up o classical o long-term potentiation ```

Question 32

Describe the wind-up process

Answer 32

Progressively increases the response of the neurones | Manifests over course of stimuli and terminates with stimuli

Question 33

Describe the Classical process

Answer 33

* Involves opening up of new synapses (silent nociceptors) in dorsal horn * Outlast the initial stimuli duration * Can be maintained even at low levels of ongoing stimuli

Question 34

What is the clinical result of classical central sensitisation

Answer 34

Hyperalgesia

Question 35

Describe long term potentiation

Answer 35

* Involves mainly the activated synapses | * Occurs primarily for very intense stimuli

Question 36

Name types of pain

Answer 36

Acute | Chronic

Question 37

Describe the features of acute pain

Answer 37

``` Physiological Noxious stimuli Protective function Nociceptive Pain resolves upon healing Less than 1 month ```

Question 38

Describe the features of chronic pain

Answer 38

``` Pathological Presence of noxious stimuli not essential No protective function Nociceptive, neuropathies or mixed Pain for 3-6 moths or more ```

Question 39

What is Nociceptive Pain

Answer 39

A sensory experience that occurs when specific peripheral sensory neurones (nociceptors) respond to noxious stimuli (actually or potentially tissue damaging event)

Question 40

What is Neuropathic Pain

Answer 40

Pain initiated or caused by a primary lesion or dysfunction in the somato-sensory nervous system

Question 41

How is pain involving transduction treated

Answer 41

NSAIDs Ice Rest LA blocks

Question 42

How is pain involving transmission treated

Answer 42

* Nerve blocks * Opioids * Anticonvulsants * Surgery- DREZ, Cordotomy

Question 43

How is pain involving perception treated

Answer 43

* Education * Cognitive behavioral therapy * Distraction * Relaxation * Graded motor imagery * Mirror box therapy

Question 44

How is pain involving descending modulation treated

Answer 44

* Placebos * Opioids * Antidepressants * Surgery: spinal cord stimulation