Pain Transmission Pathways

Question 1

What are the pain receptors and neurons associated with pain?

Answer 1

A delta fibres - myelinated
C fibres - non-myelinated (dorsal horns and sympathetic)

Question 2

Explain the ascending pathway

Answer 2

Stimulation of nociceptors in A delta and C fibres. 1st order afferent neurons release glutamate and substance P. 2nd afferent neurons then cross over within the SC and ascend contralacterally in ascending tracts

Question 3

Name the 4 tracts of the pathway

Answer 3

Spinothalamic, spinoreticular, spinoencephalic and spinoparabrachial-amygdala tracts

Question 4

What is the gate control theory of pain?

Answer 4

Modulation of pain at spinal cord level. Interneurons are activated. Inhibits pain transmission via the C fibres

Question 5

What are the types of pain?

Answer 5

Neuropathic pain - damage to nerves in the CNS/PNS. Described as an electric shock or a burning.
Inflammatory pain - release of arachindonic acid from phospholipids which are then converted into prostaglandins to regulate bodily injury.

Question 6

Define allodynia and hyperalgesia?

Answer 6

Allodynia - pain due a stimulus that does not normally provoke pain
Hyperalgesia - increased pain from a stimulus that normally provokes pain

Question 7

What is the descending pain pathway?

Answer 7

Serotonin or norderenaline inhibit communication between 1st and 2nd order neurons, meaning the sensation and interpretation of pain will be decreased.