Lecture 41 - Pain

Question 1

Pain definition?

Answer 1

unpleasant sensory and EMOTIONAL experience associated with actual or potential tissue damage

Question 2

Physiological response to pain?

Answer 2

increase HR, BP, RR, glucose, decreased gastric motility and blood flow to viscera kidney and skin

Question 3

Pain tolerance definition?

Answer 3

duraton or intensity of pain that in individual will tolerate before initiation of overt pain responses

Question 4

Increasing pain tolerance?

Answer 4

alcohol, medication, warmth, faith

Question 5

Decreasing pain tolerance?

Answer 5

repeats, fatigue, sleep deprivation

Question 6

Allodynia?

Answer 6

pain due to stimulus that is not normally painful

Question 7

Windup?

Answer 7

increased AP output from dorsal horn cells in response to sustained f of input from nociceptive afferents via C fibres (hyperalgesia, allodynia)

Question 8

Windup biochem?

Answer 8

constant stimulation -> increased Glu and substance P stimulation -> increase Ca influx -> lower receptor threshold and more responsiveness -> Central sensitivity/secondary hyperalgesia/allodynia

Question 9

Neuropathic pain types?

Answer 9

peripheral (diabetic neuropathy, trigeminal neuralgia), or central (thalamic pain syndrome, spinal cord damage)

Question 10

Nociceptive specific dorsal horn cells?

Answer 10

lamina I & II, only noxious stimuli (A delta and C fibres)

Question 11

Wide dynamic range dorsal horn cells?

Answer 11

lamina II, both noxious and innocuous (A delta, C and A beta fibres)

Question 12

Fibre types?

Answer 12

primarily umyelinated C fibres which present the long lasting pain, with some myelinated A delta fibres that give the initial sharp sensation

Question 13

Fibre modalities?

Answer 13

C is all (mechanical, thermal and chemical) when A delta is noxious mechano-thermal stimuli

Question 14

Non-neurogenic inflammation?

Answer 14

involves release of inflammatory substances from blood vessels and connective t.

Question 15

Neurogenic inflammation?

Answer 15

release of neuropeptides from C-fibres -> hyperalgesia

Question 16

Gate control theory of pain?

Answer 16

a gate, located in the dorsal horn, modulates the afferent nerve impulses - implies non-painful stimulus can block transmission of noxious stimulus

Question 17

Opening and closing the gate?

Answer 17

A delta and C fibres,; A beta (light touch) and brain messages

Question 18

Keep gate shut?

Answer 18

inhibitory interneurons releasing enkephalin that blocks NT release from C and A delta

Question 19

Descending modulatory pain pathways?

Answer 19

periaqueductal grey area (midbrain) -> pons and medulla -> release NA and 5-HT stimulating inhibitory interneurons -> enkephalin release

Question 20

Chronic pain?

Answer 20

glial cells release cytokines within dorsal horn, pain signal becomes generated in dorsal horn rather than periphery