Physiology of Pain and Thermosensation

Question 1

What are the 3 types of pain?

Answer 1

nociceptive
inflammatory
pathological

Question 2

Describe nociceptive pain?

Answer 2

immediate short lived protective response

adaptive

Question 3

Describe inflammatory pain?

Answer 3

assists in healing, persists over days - weeks

adaptive

Question 4

Describe pathological pain?

Answer 4

persists over lots of time
no physiological purpose
may be maladaptive

Question 5

What fibres make up nociceptors?

Answer 5

A gamma and C fibres

Question 6

What are the characteristics of A gamma fibres?

Answer 6

mechanical/thermal nociceptors
thinly myelinated
mediate fast/first pain

Question 7

What are the characteristics of C fibres?

Answer 7

respond to all noxious stimuli
unmyelinated
mediate second/slow pain

Question 8

What two peptides are released in inflammatory pain?

Answer 8

substance P

CGRP

Question 9

What is the role of Substance P?

Answer 9

causes vasodilation and extraction of plasma proteins (promotes formation of bradykinin and prostaglandins) causes release of histamine
sensitises surrounding nociceptors

Question 10

What is the role of CGRP?

Answer 10

induces vasodilation

Question 11

What do substance P and CGRP cause?

Answer 11

slow and prolonged epsp that activate NMDA receptors by relieving voltage dependant block by Mg

Question 12

What is the primary transmitter and what are its receptors?

Answer 12

glutamate

AMPA and NMDA receptors

Question 13

Where are primary afferent cell bodies located?

Answer 13

dorsal root ganglia

Question 14

Where do primary afferent cell bodies terminate?

Answer 14

laminae of Rexed

Question 15

Which laminae do nociceptive C and A gamma dibres terminate?

Answer 15

laminae I and II

V also for A gamma

Question 16

What fibre input do proprioceptive cells receive?

Answer 16

A beta fibres

Question 17

What does visceral pain result from?

Answer 17

nociceptors covering tissues of hollow organs - follow sympathetic pathways before entering the dorsal horn

Question 18

What causes referred pain?

Answer 18

some afferents converge upon the same spinothalamic neurones - but all cells with visceral receptive fields also have separate cutaneous receptive fields

Question 19

What is referred pain?

Answer 19

pain percieved at a distance from the affected organ
area of referral is to the segmental dermatome
often associated with autonomic features

Question 20

What is viscerosomatic pain?

Answer 20

sharp and well localised pain

Question 21

What causes viscerosomatic pain?

Answer 21

occurs when inflammatory exudate from a diseased organ contacts a somatic (body wall structure)

Question 22

What are Abeta fibres?

Answer 22

mechanoreceptors

Question 23

What are Agamma and C fibres?

Answer 23

pain perceivers

Question 24

Where are Agamma, C and Abeta fibres processed?

Answer 24

substantia gelatinosa

Question 25

What does the gate control theory relate to?

Answer 25

synaptic transmission of nociceptive signals

Question 26

What happens to the gate control theory when Abeta activity > Agamma/C activity?

Answer 26

gate is CLOSED, synaptic transmission of nociceptive signals is SURPRESSED SO PAIN IS NOT PERCIEVED

Question 27

What happens to the gate control theory when Agamma/C activity > Abeta activity?

Answer 27

gate is OPEN, synaptic transmission of nociceptive signals happens PAIN IS PERCIEVED

Question 28

In the Spinothalamic tract, where do Agamma projection neurones originate?

Answer 28

lamina 1

Question 29

In the Spinothalamic tract, where do WDR projection neurones originate?

Answer 29

lamina V

Question 30

Where do projection neurones from lamina 1 terminate?

Answer 30

posterior nucleus of the thalamus

Question 31

Where do projection neurones from lamina V terminate?

Answer 31

posterior and ventroposterior nucleus of the thalamus

Question 32

What fibres does the spinoreticular tract transmit?

Answer 32

slow C fibre pain

Question 33

What fibres respond to cold? C or Agamma?

Answer 33

C fibres

Question 34

What fibres respond to warm? C or Agamma?

Answer 34

C fibres or Agamma fibres

Question 35

What are more common C or Agamma fibres?

Answer 35

C fibres

Question 36

What is the presentation of chronic regional pain syndrome?

Answer 36

allodynia - sore to stimulus that shouldnt be painful eg cotton wool hyperalgesia - increased sensitivity to pain swelling hair and nail changes osteopenia

Question 37

What is neuropathic pain?

Answer 37

pain generated from within the nervous system - does not respond to NSAIDs or paracetemol

Question 38

What is the presentation of neuropathic pain?

Answer 38

allodynia hyperalgesia burning, shooting, tingling pain

Question 39

What can cause neuropathic pain?

Answer 39

``` shingles surgery trauma diabetic neuropathy amputation ```

Question 40

What can be used to treat neuropathic pain?

Answer 40

``` tricyclic antidepressants - amytryptilline anticonvulsants - gabapentin capsicin GABA agonists NMDA agonists Na channel blockers opioids ```