Gate control theory of pain

Question 1

3 significances of pain

Answer 1

1. forces to rest and so heal
2. warning
3. modifies avoidance behaviour

Question 2

why does rubbing an injury decrease pain perception?

Answer 2

rubbing stimulates A delta fibres which opens the gate

Question 3

How do we know descending pathways from the Brain Stem exist?

Answer 3

stimulation of PAG, PVG and raphe nuclei produced analgesia

Question 4

Where are the raphe nuclei?

Answer 4

The medulla

Question 5

What are the two main ascending pathways involved in pain?

Answer 5

spinoparabrachial and spinothalamic

Question 6

what is the route for spinoparabrachial?

Answer 6

superficial dorsal horn to brain areas concerned with affect

Question 7

how is the spinothalamic pathway involved in pain?

Answer 7

it distributes nociceptive info to areas of the cortex concerned with affect And discrimination

Question 8

which neurons do drugs activate and why?

Answer 8

PAG neurons because it has a high density of opiate receptors (mew not k at brainstem level)

Question 9

what were the first two discovered endogenous opiates?

Answer 9

met-enkephalin and leu-enkephalin (endorphins and dynorphins since discovered)

Question 10

which factors regulate the gate?

Answer 10

1. amount of activity in pain fibres
2. amount of activity in other fibres ex. A delta
3. Descending messages such as emotions and mental conditions

Question 11

Is glutamate or substance p involved in faster pain transmission?

Answer 11

Glutamate is fast transmission

Question 12

what % of amputees suffer from phantom limb pain?

Answer 12

80%

Question 13

what is included in the “raphe system”?

Answer 13

the raphe nucleus and the medullary reticular formation

Question 14

Which NT is released by the lateral spinal cord route path for descending pathways of pain inhibition?

Answer 14

NA, which acts mainly on enkephalin receptors

Question 15

Which NT is released by the dorsolateral spinal cord route path for descending pathways of pain inhibition?

Answer 15

serotonin, which acts mainly on enkephalin receptors

Question 16

What is the evidence for serotonergic systems in descending pain pathways?

Answer 16

1. Inhibition of 5HT synthesis/destruction of cells that produce 5HT blocks analgesic action of opiates
2. Applying 5HT to the spinal cord results in analgesia plus reduces response to noxious stimuli

Question 17

What is the evidence for noradrenergic systems in descending pain pathways?

Answer 17

1. morphine action blocked by alpha-adrenergic antagonists

2. NA to spinal cord induces analgesia

Question 18

What evidence is against the role of NA systems in descending pain pathways?

Answer 18

Blocking NA in the RVM still allows analgesia

Question 19

main potential function of facilitatory descending pathways

Answer 19

increase sensitivity to noxious stimuli during illness to promote recovery