PAIN

Question 1

Give 3 aspects of the definition of pain

Answer 1

Sensory, Emotional, Homeostatic response.

Question 2

Define Pain In terms of the Sensory component.

Answer 2

PAIN = A sensation evoked by injury

Question 3

Define Pain in terms of the Emotional component

Answer 3

PAIN = An unpleasant and aversive experience (affective)

Question 4

Outline the possible purposes of pain.

Answer 4

• Response to potential tissue damage
• Avoidance/defence
• Warning/Protection
• Rest
• LEARNING

Question 5

Give an example of how Pain can be caused directly by injury

Answer 5

David Lawrence (cricket player), knee-cap split, in obvious pain, last time he played.

Question 6

Give an example of where there is an absence of Pain following injury

Answer 6

Manteo MItchell (sprinter) broke his left fibula halfway through his run of relay but continued without pain.

Question 7

What was Descartes definition of Pain?

Answer 7

Fast moving particles of fire that pass along the nerve filament and reach the brain

Question 8

What are Nociceptors?

Answer 8

The sensory receptor that transduce painful stimuli to electrical signals and transmit them to higher centres in the CNS

Question 9

What is Microneurography?

Answer 9

a Neurophysiological method to visualise and record traffic of impulses in peripheral nerves of awake human subjects. Its used to record nociceptor activity

Question 10

With what type of Nociceptor is pain sensation transmitted>

Answer 10

Unmyelinated C fibers (primarily) and lightly myelinated A-delta fibres.

Question 11

What are the main features of C fibres?

Answer 11

• Are polymodal; respond to noxious mechanical, heat and even chemical (histamine)
• Have small receptive fields
• Have slow conduction velocities 0.5-1.5m/s

Question 12

What are the TRP family with regards to sensation and nociception?

Answer 12

Transient Receptor Potential Cation Channels. They open in the membrane of the C fibre in response to specific modalities

Question 13

What are TRPV1, TRPV2 and TRPA1 responsible for in the C-fibre?

Answer 13

TRPV1 = detection of temperature provides sensation of scalding heat (43 degrees up). Responds also to Capsaicin (in pepper) 
TRPV2 = detection of higher temps (52 degrees up) 
TRPA1 = mechanical stress sensor.

Question 14

What is the sodium channel expressed by nociceptors?

Answer 14

Nav1.7 which is encoded by the gene SCN9A. It amplifies small depolarisations and is a threshold channel that regulates excitability. It is required for pain sensation

Question 15

Name the three pain disorders caused by mutations of the SCN9A gene.

Answer 15

• Primary Erythromelalgia (PE)
• Paroxysmal Extreme Pain Disorder(PEPD)
• Congenital Insensitivity to Pain (CIP)

Question 16

Outline the symptoms of PE

Answer 16

Severe burning pain and skin redness in extremities triggered by heat, pressure and exertion Inheritance is Dominant. Nav1.7 function is increased

Question 17

Outline the symptoms PEPD

Answer 17

Pain in mandibular, ocular and rectal areas. Nav1.7 function is increased.

Question 18

Outline the symptoms of CIP

Answer 18

Insensitivity to Pain, otherwise the individual is normal. Nav1.7 function is absent

Question 19

Name the 7 factors that affect an individuals perception of pain.

Answer 19

• Site of origin
• Duration
• Context
• Cultural Background
• Past History
• Expectation
• Mood (depression)

Question 20

What 2 principles show that Nociceptive input is modified by CNS?

Answer 20

Pain without injury: back pain, migraine. neuropathic pain

Injury without pain.

Question 21

What is Neuropathic Pain?

Answer 21

The pain following a peripheral nerve lesion produces one of the worst pains.

Question 22

Outline the importance of the Dorsal Horn

Answer 22

It is the site of first synapse for nociceptive fibres it’s the site of integration and modulation of info.

Question 23

Outline the important features of the Gate Theory

Answer 23

• nociceptive signal is modified at the Dorsal Horn
• Low Threshold A-Beta mechanoreceptor input inhibit nociceptor input
• Descending info from brain can alter nociceptive signal.

Question 24

What is the difference between Pain and Nociception?

Answer 24

Nociception is the processing of signals from nociceptors but Pain is the subjective experience in the brain

Question 25

Explain what is meant by “Wind up”.

Answer 25

It’s the perceived increase in pain intensity over time when a painful stimulus is delivered repeatedly.

Question 26

What is the cause of Wind-up?

Answer 26

A progressive increase in the number of action potentials elicited per stimulus in dorsal horn neurons due to repetitive C fibre stimulation.

Question 27

What can prolonged nociceptor activity lead to?

Answer 27

Long Term Potentiation in the Dorsal Horn