Physiology Of Pain 1

Question 1

Classifications of Pain

Answer 1

Nociceptive
Inflammatory
Neuropathic

Question 2

What is pain

Answer 2

Unpleasant sensory experience associated with tissue damage

via A delta and C fibres

Question 3

What is a nociceptor

Answer 3

First order neuron of spinothalamic tract
Pseudo unipolar (central and peripheral axon)
primary sensory

Question 4

What do A alpha and beta fibres fibres detect?

-comment on diameter and myelin content

Answer 4

Detect light touch and proprioception
Myelinated
Large diameter

Question 5

Which fibres detect sharp pricking pain?

-comment on this fibre’s diameter and myelin content

Answer 5

A Delta fibres 
Detect light touch, temperature and noiception, sharp 'pricking' pain 
thinly myelinated
medium diameter
low in viscera

Question 6

Which fibres detect slow, dull aches and burning pains?

-comment on this fibre’s myelin content and diameter

Answer 6

C fibres
Detects temperature, noiception 
Unmyelinated
Small diameter 
Slow burning pains, itch, dull ache

Question 7

What channel is activated by high temperature?

Answer 7

TRPV1

Question 8

CHILLI is an agonist of which channel

Answer 8

TRPV1

Question 9

Where does the spinothalamic tract synapse in the dorsal horn

Answer 9

Substantial gelatinosa

Question 10

How does stress induced analgesia occur?

Answer 10

PAG neurons excite RVM, which inhibits the spinothalamic tract

Question 11

Opioids

Answer 11

Found in both CNS and PNS

Inhibitory- so act on inhibitory metabotropic receptors

Question 12

How does ATP directly activate nociceptors?

Answer 12

Binds to purinergic receptors (p2X)

Question 13

How does H+ directly activate nociceptors?

Answer 13

Binds to acid sensing ion channels

Question 14

What is referred pain?

Answer 14

convergence of visceral and cutaneous nociceptor on same second order neurons in spinal cord

Question 15

Why is pain felt in upper left arm after an MI?

Answer 15

convergence on 2nd order neuron from visceral nociceptor from heart and cutaneous nociceptor from skin over left arm

Question 16

How does stress induced analgesia occur?

Answer 16

PAG (Periaqueductal gray matter) excite RVM (Rostral Ventromedial medulla) neuones, which inhibit (or excite) the spinothalamic tract

Question 17

What is allodynia?

Answer 17

Non-noxious stimuli produce a painful responce

Question 18

What is hyperalgesia?

Answer 18

Noxious stimuli produce an exaggerated pain response

Question 19

What is peripheral sensitization

Answer 19

Increase in responsiveness of peripheral ends of nociceptors
driven by tissue injury or inflammation
Bradykinin and NGF reduce the threshold of heat activated (TRPV1)
Prostaglandins reduces threshold of sodium channels

Question 20

Describe the mechanism of action of Bradykinin

Answer 20

Binds to receptor (metabotropic-GPCR)

Activation of protein kinase phosphorylates TRPV1 (this phosphorylation reduces threshold of channel so it fires more easily)