Pain

Question 1

What is pain?

Answer 1

An unpleasant sensory and emotional experience associated with actual or potential tissue damage

Question 2

Why is pain important?

Answer 2

1. Promotes avoidance of situations which may decrease biological fitness
2. Promotes resting behaviour that either enhances recovery or modifies behaviour so that further injury or death becomes less likely

Question 3

What type of receptors detect pain?

Answer 3

Nocioceptors

Question 4

How is pain sensed throughout the skin?

Answer 4

Free nerve endings

Question 5

How is pain felt from internal organs?

Answer 5

In the local area on the outside of the body

Question 6

How is intense pressure, stretching, shrinking and pinching felt?

Answer 6

High threshold mechanoreceptors, due to depolorisation and calcium influx

Question 7

Vanilloid receptors and temperature gated channels sense what types of pain?

Answer 7

Heats, acids and capsaicin

Question 8

What do vanilloid receptors flux?

Answer 8

Sodium, leading to an action potential

Question 9

Where are vanilloid receptors found?

Answer 9

In the free nerve endings

Question 10

What is released following tissue damage?

Answer 10

ATP

Question 11

What is the circuit that causes you to withdraw from a painful stimulus?

Answer 11

Spinal reflex reaction - neuron, spinal cord interneuron - efferent motor neuron

Question 12

What is the name of the neurons that send messages about the initial pain to the brain (before you’ve realised the pain has occurred)?

Answer 12

Procioceptors

Question 13

What are the features of procioceptors?

Answer 13

Large diameter and myelinated

Question 14

Name the fibres that carry messages about the first pain, and localisation of the painful stimulus?

Answer 14

Delta fibres

Question 15

What fibres provide the secondary pain that is the continuing dull ache?

Answer 15

C fibres

Question 16

Name the 2 pathways to the brain

Answer 16

1. Somatosensory cortex via the thalamus
2. To the emotional cortex, the insula and cingulate

Question 17

What is hyperalgesia?

Answer 17

Noxious stimuli produce exaggerated pain sensation

Question 18

What is allodynia?

Answer 18

Non-noxious stimuli produce pain sensation, eg touching burnt skin

Question 19

What is released in peripheral sensitisation?

Answer 19

1. Chemicals released as a result of tissue damage such as hydrogen and ATP
2. Neuropeptides which trigger in the neighbouring blood supply the release of plasma

Question 20

Histamine and NGF are examples of what type of cells?

Answer 20

Mast cells

Question 21

Proteases cleave extracellular peptides to create what?

Answer 21

Bradykinin

Question 22

What do COX enzymes convert arachidonic acid to?

Answer 22

Protaglandins

Question 23

How does the nocioceptor become modulated so that it responds at lower pain thresholds?

Answer 23

1. Components of the inflammatory soup such as bradykinin, NGF and prostaglandin feedback to their own receptors on the nocioceptor neurons
2. The VR1 receptor is then phosphorylated and the threshold for firing changes
3. A sensory nerve specific sodium channel is phosphorylated so threshold voltage for firing is decreased, making the nocioceptor more excitable and hypersensitive to stimulation

Question 24

Why does pain increase sensitivity?

Answer 24

1. Reminds you that you have hurt yourself
2. Promoting the area for recovery

Question 25

How do neuroplastic changed at the synapses in the spinal cord occur?

Answer 25

1. Nocioceptive afferents release glutamate and substance P 2. Substance P activates the KN1 receptor which leads to phosphorylation of the NMDA and AMPA receptors 3. This means they become more responsive to glutamate and neurons become more excitable 4. Substance P diffused to to other synapses and so wind up pain can spread causing generalised sensitisation to painful stimuli

Question 26

What is gate-control theory?

Answer 26

When you hob up and down or blow on the area and it appears to reduce pain

Question 27

Stimulation of the non-nocioceptive mechanoreceptors in the vicinity of the injury activates neurons where? The activation of these neurons stops what neuron from firing?

Answer 27

1. Dorsal horn 2. Spinothalamic neuron

Question 28

Competition between what two neurons switches off C fibres and prevents the pain signal from getting to the brain?

Answer 28

The nocioceptor and the inhibition from the propcioceptors

Question 29

How much were burns patients pain ratings reduced by when in the VR condition?

Answer 29

30-50%

Question 30

What is stress-induced analgesia?

Answer 30

Adaptive response to down-regulate pain

Question 31

What is naloxine challenge?

Answer 31

An opioid antagonist which blocks the analgesic effect

Question 32

Give an example of stress-induced analgesia

Answer 32

Soldiers escaping danger who don't feel the pain of their wounds until in safety

Question 33

Name three methods of reducing pain

Answer 33

Opiates, NSAIDS, cannabinoids, sodium channle blockers

Question 34

What is neuropathic pain?

Answer 34

Pain caused by damage to the nerves themselves n