5 Pain

Question 1

How is nociceptor stimulation intensity encoded?

Answer 1

firing rate

Question 2

What are the types of pain generating stimuli?

Answer 2

Injury
Heat (>46degrees)
Cold
Inflammation
pH

Question 3

What are the 2 types of nociceptor?

Answer 3

Mechanical nociceptor (sharp pain)
Polymodal nociceptor (dull burning pain)

Question 4

What sort of axons do mechanical nociceptors use?

Answer 4

A-delta fibres

Question 5

What sort of axons do polymodal nociceptors use?

Answer 5

C-fibres

Question 6

Name 5 chemicals that might be released by damaged tissue

Answer 6

K+
H+
histamine
prostoglandins
bradykinin

Question 7

do non-noxious signals like touch pass through the dorsal horn or decussate at that level?

Answer 7

dorsal horn mate

Question 8

What is lamina 2 of the dorsal horn otherwise known as?

Answer 8

Substantia Gelatinosa

Question 9

What sorts of fibres carry non-noxious sensory information?

Answer 9

A-beta

Question 10

Which laminae of the dorsal horn receive sensory input from A-beta fibres?

Answer 10

III-V

Question 11

Which laminae of the dorsal horn receive sensory input from A-delta and C-fibres?

Answer 11

cutaneous (I-II)

visceral (I, V, X)

Question 12

Where does the inhibitory interneurone from the Substantia gelatinosa synapse with the ascending pain neurone?

Answer 12

lamina V-VI

Question 13

How do A-beta mechanoreceptors interact with neurones in the spinal cord?

Answer 13

+ synapse directly with the ascending pain neurone

also + synapse with substantia gelatinosa inhibiotry interneurone

Question 14

How do the A-delta and C fibres ensure we feel pain?

Answer 14

limits inhibition and offers + sitmulation of ascending spinal tract

Question 15

What is the Gate-control theory?

Answer 15

Increased non-noxious afferent input to spinal cord for analgesic effect

Question 16

What is the principle of TENS?

Answer 16

Transcutaneous electrical nerve stimulation

A-beta fibres are fat so easy to activate, increased activation dominates gate.

Question 17

What is the Intrinsic Analgesia system?

Answer 17

substances released in descending pathways inhibit ascending pathways, closing the gate

(5-HT, noradrenaline, enkephalin)

Question 18

Define allodynia

Answer 18

pain due to a stimulus that does not normally invoke pain (hyperalgesia)

this might be caused by injury

Question 19

What is an antidromic action potenital?

Answer 19

conduciton opposite direction to normal (orthodromic)

causes release at peripheral nerve ending

Question 20

What might antidromic action potentials induce?

Answer 20

substance P and CGRP release

Question 21

What do substance P and CGRP cause?

Answer 21

redness, swelling
plasma extravasation
immune cell migration and activation

Question 22

What is in the inflammatory soup?

Answer 22

Prostaglandins
H+
bradykinin
NGF
cytokines

Question 23

What does the inflammatory soup do?

Answer 23

sensitisation of polymodal nociceptor

Question 24

What are the 2 features of the peripheral sensitisation mechanism?

Answer 24

primary hyperalgesia (directly in damaged tissue)
secondary hyperalgesia (distant to site of injury)

Question 25

What is a common agonist of the AMPA and NMDA receptors?

Answer 25

Glutamate

Question 26

What does substance P bind to?

Answer 26

NK-1

Question 27

What effect does NK-1 have on other receptorrs?

Answer 27

increased depolarisaiton
MG2+ pops out of NMDA channel

glutamate can activate NMDA, Ca2+ influx

Question 28

What substance is released in the central sensitisation mechanism and not in acute pain signalling?

Answer 28

substance P