Pain - 230

Question 1

Give a basic description of chronic pain

Answer 1

Pain that persists beyond normal healing time (3-6 months)

Question 2

What is CIP and what is it due to?

Answer 2

Congenital insensitivity to pain. Due to mutations in the Na channels

Question 3

Name 3 molecules that sensitize receptors to pain

Answer 3

Histamine
Bradykinin
Prostaglandins

Question 4

How is mechanical pain detected by nociceptors?

Answer 4

Stretch receptors

Question 5

How is thermal pain detected by nociceptors?

Answer 5

TRPV1 - capsaicin receptor. Detects pain as temp .43*C

Question 6

Describe the 2 types of nociceptor and how they differ

Answer 6

A-delta fibres: myelinated, fast and unimodal SPECIFC

C-fibres: unmyelinated, slow, polymodal.

Question 7

What do A-beta receptors detect?

Answer 7

Pressure and tactile sensations

Question 8

Describe the mechanism by which rubbing a sore knee can alleviate the pain

Answer 8

Rubbing the knee stimulates A-beta fibres (pressure & tactile info), which inhibits A-delta fibres (fast pain sensation)

Question 9

What is the relevance of Na regarding pain?

Answer 9

Action potentials result in Na influx, which causes depolarisation and triggers the propagation of an AP. This would relay the pain signal.

Question 10

How do local anaesthetics work? Give an example

Answer 10

Block voltage-gated Na channels.

Lidocaine

Question 11

How do anticonvulsants work? Example

Answer 11

Block voltage gated Na channels.

Carbamazepine

Question 12

What are the 1st, 2nd and 3rd order neurones in the pain pathway?

Answer 12

1st = nociceptor
2nd = Spinothalamic tract
3rd = Thalamocortical projection

Question 13

Where do the 1st order neurones synapse with 2nd order neurones?

Answer 13

Substantia gelatinosa

Question 14

Axons from nociceptors enter where and ascend in what?

Answer 14

Enter dorsal horn.

Ascend in Lissaures tracts

Question 15

What happens regarding pain sensation if the primary somatosensory cortex is damaged?

Answer 15

You can still feel pain but cannot tell where it is coming from, as it is responsible for detecting and localizing pain.

Question 16

How do descending pathways mediate the pain response?

Answer 16

They modulate the activity of the ascending pathway and produce opioids

Question 17

What do spinal interneurones release to prevent APs (and inhibit pain) and where do they release it?

Answer 17

Enkephalins. Between 1st and 2nd order neurones.

Question 18

What is the mechanism behind phantom limb pain?

Answer 18

Massive loss of sensory input, which results in sensory confusion that is expressed as pain.

Question 19

Name the 3 opioid receptors

Answer 19

Mu, Delta, kappa

Question 20

Endorphins have the highest affinity for which opioid receptor?

Answer 20

Mu -> highly addictive, e.g. heroin.

Question 21

Which opioid receptor agonists are the most potent analgesics?

Answer 21

Mu and delta

Question 22

Where can referred pain from the diaphragm, heart, stomach, gall bladder and appendix radiate to?

Answer 22

Diaphragm - C3-4
Heart - T1-4
Stomach - T6-9
Gall bladder - T7-8
Appendix - T10

Question 23

Which opioid must be taken with caution in those with seizure risks?

Answer 23

Tramadol