Pain and analgesia (8.4)

Question 1

Explain the difference between pain and nociception

Answer 1

Pain: An unpleasant emotional and sensory experience

• ALWAYS unpleasant

Nociception: The sensory process which provides signals which may trigger feelings of pain

• May be pleasant/enjoyable

Question 2

Describe the transduction of noxious stimuli

Answer 2

Pain is transmitted by nociceptors. They allow for the onward transmission of signals which may generate pain.

Nociceptors are triggered by noxious stimuli, commonly those which are likely to cause damage to the corresponding tissue.

Nociceptors:

• Generally are free nerve endings
• Generally are polymodal (mechanical, thermal and chemical stimuli) but some show selectivity
• Transmission may be achieved through fast Aδ or slow C fibres.
• Aδ transmit short, sharp pain. C fibres transmit slow, dull and longer pain. Hence, the intial and later feelings of pain are different.
• Use excitatory neurotransmitters (glutamate and substance P)
• Synapse with second order neurones in the dorsal horn substantia gelatinosa (first 3 laminae)

Question 3

Outline the transmission of nociception

Answer 3

Question 4

Outline the neural circuitries involved in regulating pain

Answer 4

Question 5

Outline the difference between acute and chronic pain

+ Key Terms

Answer 5

Acute pain:

Chronic pain: Pain persisting > 3-6 months OR which lasts beyond its reparative and protective role (healing has occured)

• Changes within the nociceptive pathway are seen. There is a lower threshold for pain
• It may be asked why endogenous analgesic systems are not able to control the pain. It may be that there is a deficit within these systems or that there is a lack of ‘drive’

Hyperalgesia: Enhanced pain sensation from a noxious stimuli. Normally seen when the area contacted is inflammed.

Allodynia: Pain from a stimulus which is normally not noxious

Spontaneous pain: Pain in the absence of a stimulus

Question 6

Outline the non-pharmalogical treatment of pain

Answer 6