Pain And Nociception

Question 0

Which afferents fibres transduce these signals ?

Answer 0

C and a- delta

Question 1

When tissue is damaged and inflamed it release substances what are they?

Answer 1

Bradykinin, histamine and prostaglandins

Sensitise peripheral nociceptors inducing hyperalgesia

Question 2

What is fast pain ?

Answer 2

Conducted by a-delta fibres 
Sharp prickling pain 
Short duration 
Occurs rapidly 
Easily localised 
Mechanical or thermal nociceptors

Question 3

What is slow pain?

Answer 3

Conducted by c fibres 
Dull ache, burning 
Slow onset 
Persistent 
Poorly localised
Poly modal nociceptors

Question 4

What receptors detect heat ?

Answer 4

Trpv1-3, trek-1

Question 5

What receptors detect chemicals ?

Answer 5

Trpv1, asic, drasic

Question 6

What receptors detect mechanical changes ?

Answer 6

Mdeg, drasic, trek-1

Question 7

What receptors detect cold ?

Answer 7

Trpm8

Question 8

What happens in the zone of lissauer and what effect does it have ?

Answer 8

The afferents enter into dorsal horn and go up/down a few spinal segments in the zone of lissauer
It makes it more difficult to localise the pain

Question 9

What is the substantia gelatinosa ?

Answer 9

Laminae 1 and 2 where nociceptive afferents project into and synapse

Question 10

What is referred pain ?

Answer 10

Cross talk between afferents which enter dorsal horn through common route
- visceral pain is perceived as having a cutaneous source

Question 11

Examples of referred pain?

Answer 11

Oesophagus - chest wall 
Heart- chest and arm 
Bladder - perineum
Ureter - lower abdomen and back 
Prostate - lower trunk and legs 
These pains can be useful for clinicians

Question 12

What are the 3 ascending pain pathways ?

Answer 12

Lateral spinothalamic
Spinoreticulothalamic
Anterior spinothalamic tract

Question 13

What happens if you have a unilateral spinal cord injury and what is the effect ?

Answer 13

Sensory loss of touch, pressure, vibration and proprioception on the ipsilateral side
Diminished sensation of pain on the contralateral side
Brown sequard syndrome
This is called dissociated sensory loss

Question 14

What happens in he Trigeminal system ?

Answer 14

Carries info about pain and temp from face and head
Afferents descend ipsilaterally in spinal trigeminal tract to BRAINSTEM
Synapse with 2nd order neurons in pars caudalia
Decussate onto contralateral side to ascend to thalamus in trigeminothalamic tract
Project to cortex via the ventral posteromedial nucleus

Question 15

What is phantom pain and why do they think it occurs ?

Answer 15

Pain and touch sensations without input
Usually seen in amputees
May occur due to reorganisation in the virtual body maps in cortex and thalamus

Question 16

What happens in endogenous analgesia and pain modulation ?

Answer 16

Sensory inputs of pain without a sensation

Question 17

What are the examples of endogenous ligands of cannabis ?

Answer 17

Anandamide

2-arachidonyl-glycerol

Question 18

What is the purpose of the cortex, thalamus and limbic system in pain stimuli ?

Answer 18

Cortex- involved in localisation of pain
Thalamus - involved in perception of pain
Limbic system- involved in emotional pain

Question 19

What are the effects of endogenous opioids?

Answer 19

Presynaptic inhibition

- they decrease transmitter release so reduce pain response

Question 20

Examples of acute pain …

Answer 20

Skin abrasion 
Deep tissue injury 
Superficial burn 
Labour 
Important for protection

Question 21

Examples of chronic pain…

Answer 21

Inflammatory pain, neuropathic pain and neuralgias

Question 22

What is hyperalgesia ?

Answer 22

When tissue is already damaged or inflamed it is unusually sensitive to pain 
Can be 
- reduced threshold for pain 
- increase intensity of pain stimuli 
- spontaneous pain

Question 24

What is the gate theory of pain ?

Answer 24

Theory that if there is increased activity in the a-alpha/ beta fibres then there is less stimulation of the c fibres onto the projection neurons to the brain so reduced pain is felt