Pain

Question 1

What is the receptive field ?

Answer 1

An area that a particular nerve responds to a stimulus in.

Question 2

What is a stimulus turned into ?

Answer 2

Depolarisation - Receptor potential - Generator potential

Question 3

What determines acuity ?

Answer 3

• Area of receptive field

- Density of neurones in the area

Question 4

What are Ab fibres ?

Answer 4

Large myelinated axons that carry information on touch, vibration and pressure

Question 5

What are Aℑ fibres ?

Answer 5

Small myelinated axons that carry information on fast , sharp pain and cold

Question 6

What are C fibres ?

Answer 6

They are unmyelinated axons that carry information on dull, slow pain and warmth

Question 7

Which fibres mediate proprioception ?

Answer 7

Aa and Ab

Question 8

Where do Aa get signals from ?

Answer 8

Extrafusal muscle spindles and GTO’s

Question 9

Where do Ab get signals from ?

Answer 9

Secondary receptors of muscle spindles

Question 10

What 3 things do sensory pathways do ?

Answer 10

• Converge
• Adapt
• Laterally inhibit

Question 11

Definition of nociception

Answer 11

The detection of noxious harmful stimuli by Aℑ and C fibres that have the ability to cause tissue damage.

Question 12

What is the gate control theory ?

Answer 12

Aa and Ab fibres activate inhibitory interneurones by releasing endorphins that inhibit transmitter release in Aℑ and C fibres. Descenind inhibition from PAG and NRM also activate these inhibitory interneurones and hence close the gate.

Question 13

Which is the name of the neurotransmitter release ?

Answer 13

Substance P

Question 14

How do NSAID’S work ?

Answer 14

They stop COX from converting arachidonic acid into prostaglandins. Less prostaglandins less sensitisation to bradykinin, less depolarisation and so less pain.

Question 15

How do local aesthetics work ?

Answer 15

Block all Na+ - axonal transmission is stopped

Question 16

How does TENS (Transcutaneous Electrical Nerve Stimulation) work ?

Answer 16

Some method as closing the gate. Aa and Ab fibres are activated and they activate inhibitory interneurones which prevent signals passing up through Aℑ and C fibres.

Question 17

How do opiates work ?

Answer 17

• Reduce the amount of neurotransmitter release
• Activate the descending inhibitory pathways
• Reduce the sensitivity of nociceptors

Question 18

What is Neuropathic pain ?

Answer 18

Pain caused by nerve damage. Usually a burning or prickling sensation. There is no obvious tissue damage, usually resistant to medical treatment.

Question 19

Why does referred pain occur ?

Answer 19

The visceral and somatic nerve fibres enter the spinal cord at the same level. This can sometimes lead to misinterpretation of incoming signals by higher brain centres.

Question 20

Where does the LST terminate ?

Answer 20

In the ventroposteior thalamic nuclei

Question 21

Where does the AST terminate

Answer 21

In the medial thalamic nuclei

Question 22

Where are signals sent from the thalamus ?

Answer 22

The cortex, brainstem and limbic system

Question 23

Where does pain perception occur ?

Answer 23

In the somatosensory cortex

Question 24

What is involved in the descending control of pain

Answer 24

The medial thalamus, hippocampus and amygdala are involved and they relay this to the brainstem.

Question 25

Where do descending pathways go ?

Answer 25

Via the PAG

Question 26

Definition of Hyperalgesia

Answer 26

Increased perception of pain

Question 27

Allodynia

Answer 27

Decreased threshold of pain response

Question 28

What happens during peripheral sensitisation ?

Answer 28

The nociceptive receptors have an increased sensitivity to stimuli

Question 29

What is central sensitisation ?

Answer 29

Increases the response of the 2nd order neurone in the CNS to normal input of both noxious and noxious stimuli.

Question 30

What can central sensitisation lead to ?

Answer 30

The development and maintenance of chronic pain.

Question 31

What are the 3 stages of central sensitisation ?

Answer 31

1. Wind up
2. Classical
3. Long-term potentiation

Question 32

What is wind up ?

Answer 32

Occurs only during the stimulus, and causes an increase in the number of AP’s that are fired due to a stimulus. Substance P and CGRP are involved.

Question 33

What is classical ?

Answer 33

Classical involves opening up new synapses. Starts with the stimulus and outlasts it. It results in secondary hyperalgesia.

Question 34

What is secondary hyperalgesia ?

Answer 34

Secondary hyperalgesia is defined as an increase in pain sensitivity when a noxious stimulus is delivered to a region surrounding, but not including, the zone of injury.

Question 35

What is long-term potentiation ?

Answer 35

Involved both AMPA and NMDA receptors activated by glutamate. Synapses are strengthened.

Question 36

Features of acute pain

Answer 36

• < 1 month
• Tissue damage
• Has a protective function
• Pain resolves upon healing
• Usually nociceptive
• Responds to conventional analgesics

Question 37

Features of chronic pain

Answer 37

• > 3 months
• Pain beyond the expected timeframe of healing
• No protective function
• Degrades health and function
• Usually neuropathic
• Doesn’t respond well to conventional analgesics

Question 38

What is neuropathic pain ?

Answer 38

Damage or disease affecting the somatosensory NS, it causes pain.

Question 39

What can block transduction ?

Answer 39

• Ice
• Rest
• NSAID’s

Question 40

What can block transmission ?

Answer 40

• Nerve block
• Opiates
• Cordotomy

Question 41

What can help with reducing pain perception ?

Answer 41

• CBT
• Relaxation
• Distraction

Question 42

What helps control descending modulation ?

Answer 42

• Opioids

- Anti-depressants