Physiology of Pain

Question 1

Define pain

Answer 1

An unpleasant sensory and emotional experience which is associated with actual tissue damage or described in terms of such damage

Question 2

What are the three forms of pain?

Answer 2

1. Nociceptive - specific primary sensory afferent neurones normally activated by intense noxious stimuli
2. Inflammatory - activation of immune system by tissue injury or infection
3. Pathological

Question 3

Which type of pain is not adaptive?

Answer 3

Pathological pain

Question 4

What is pathological pain?

Answer 4

Pain that outlives its biological or adaptive purpose - neuropathic = damage to neural tissue

dysfucntional - no identifiable damage or inflammation eg fibromyalgia

Question 5

What is adaptive pain?

Answer 5

Pain which serves as an early warning system to detect and minimise contact with damaging stimuli

(nociceptive and inflammatory pain)

Question 6

What threshold level does nociceptive pain have?

Answer 6

High

It is activated by intense stimuli

Question 7

Which type of pain is associated with pain hypersensitivity?

Answer 7

Inflammatory pain

Question 8

What is pain hypersensitivity?

Answer 8

An increased behavioural response to a constant painful stimulus in order to allow for healing

This is adaptive

Question 9

What is allodynia?

Answer 9

Increased sensitivity to painful region and when non-painful stimuli cause pain.

This is to ensure constact with the painful area is minimised to allow for healing

Question 10

Which two types of pathological pain exist?

Answer 10

1. Neuropathic pain
2. Dysfunctional pain

Question 11

What is neuropathic pain?

Answer 11

Pain caused due to nerve cell damage

Question 12

What is dysfunctional pain?

Answer 12

A potentially irregular processing of inoculous information in the CNS

Question 13

What is the name of the condition that results in complete absense of pain?

Answer 13

Congenital insensitivity to pain (CIP)

Caused by a loss of function mutation affecting voltage activated sodium channels which are highly expressed in nociceptive receptors

Question 14

What are the two types of nociceptor?

Answer 14

1. Aδ fibres
2. C fibres

Question 15

What are the 3 main differences regarding Aδ and C nociceptive fibres?

Answer 15

1. Aδ fibres are thinly myelinated, C fibres are not
2. Aδ fibres only respond to thermal or mechanical stimuli whilst C fibres respond to all noxious stimuli (polymodal)
3. Aδ fibres confer “fast” pain, whilst C fibres confer “slow” pain

Question 16

What is the pathway from the sensory receptor to the CNS for pain?

Answer 16

1. Nociceptor
2. Second order neurone
3. Spinothalmic or spinoreticulothalmic tracts

Question 17

Which type of nociceptive fibre has:

a) A really high heat threshold (53 degrees)
b) A more moderate heat threshold (43 degrees)

Answer 17

a) Aδ type I
b) Aδ type II

Question 18

What is the neurotransmitter associated with nociceptive receptors?

Answer 18

Glutamate

Question 19

How is nociceptive information sent to the CNS within the dorsal horn?

Answer 19

• Glutamate
• Peptides (substance P and neurokinin A)

Question 20

What is the efferent function of C fibres?

Answer 20

Pro-inflammatory mediator release from peripheral terminals (calcitonin and substance P)

Question 21

Which nerve fibre transmits proprioceptive stimuli?

Answer 21

Aβ fibres

Question 22

How many major nociceptie tracts are there?

Answer 22

2

Question 23

what are the 4 distinct processes int eh physiology of pain

Answer 23

transduction - noxious stimulus into electrical activity

transmission - pain signal as nerve impulse

modulation - modification of pain transmission in nervous sytem - opioids

perception - conscious expereince of pain

Question 24

What is nociceptive pain?

Answer 24

nromal response to injury by noxious stimuli

Question 25

referred pain - what is it?

Answer 25

Pain developed in one part of the body but can be felt elsewhere; usually deep pain or visceral pain is referred