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Flashcards in Pain Deck (33):
0

Types of pain:
Noiciceptive

Stimulation of peripheral noiceptors
Limb fractures, sprains, burns

1

Types of pain:
Neuropathic

Neuronal damage by inflamation
Post-herpetic neuralgia, cancer pain, diabetic neuralgia

2

Types pf pain:
Psychogenic

Physical pain from emotional factors
Tension headache, back pain, stomach pain

3

Types of pain:
Phantom limb

Pain from removed limb

4

Why do we have pain?

Pain signals to brain that body has encountered a damaging stimulus

5

What two diseases improperly perceive pain?

Familial dysautonomia (disorder of ans)
Congenital insensitivity to pain and anhidrosis (mutation in ntrk1r for ngf)

6

How are pain pathways activated, ie. what threshold and firing rate?

High and fast

7

Types of nociceptors

Gpcr, ligand gated, heat/acid sensing trp, heat sensitive k+ channels

8

A delta fibres

Thinly myelinated
Fast 20m/s
Conveys 10% of pain

9

C fibres

Unmyelinated
Small diameter
2m/s
90% of pain

10

Reticular formation of brain

General onset of pain
Origin of descending analgesic pathways

11

Thalamus

Spinothalamic tract, sends efferents to map pain

12

Periaquiductal grey

Relays between ascending and descending pathways
Lesion does not increase pain threshold or reduce analgesia

13

Under what may pain be supressed?

Stress
Opiods


Stress induced analgesia in mice is partially blocked by naloxone mu opiod antagonist

14

Brain areas involved in descending pain pathways

Rostral ventral medulla
Periaquiductal gm

Contain lots of opiod receptors

15

Role of descending pathways in pain

Descend to spinal cord and inhibit release of substance p

16

How do opiods work?

Inhibit gaba inhib interneurones on descending pathway, therefore increase descending excitation into spinal cord to suppress pain.

17

Endogenous opiods

Enkephalins, dynorphin, endorphin

18

Endogenous cannabinoids

Anandamide and 2-aracidonyl glycerol

Stress induced analgesia partially blocked by rimonabant

19

Name nsaids

Asprin, ibuprofen, naproxen, indomethacin

20

Role of nsaids

Decrease inflammation, decrease sensitiation, decrease fever (antipyretic)

21

Analgesic effects of paracetamol and nsaids

Decrease synthesis of proinflammatory prostaglandins and pro-nociceptive compounds from arachidonic acid via inhibition of cox-1 and cox-2 enzymes

22

Mechanism of action of nsaids

Tissue injury, membrane breaks down to release arachidonic acid
Which with the use of cox1 and cox2 makes prostaglandins
Prostaglandins are isomerised in specific tissues (platelet aggression, sensitisatio of noiciceptors)

23

Role of cox1

Products protect the stomach from acid enviornment

Blocked by asprin, non selective nsaids

24

Role of cox2 and inhibitors

Products recruit inflamation, wbcs, sensitise oain, stimulate fever

Blocked by asprin, nonselc nsaids, cox inhibs

25

Cox2 selective inhibitors discuss.

Rofecoxibs, celocoxibs
Protect stomach
Increase formation of thromboxane
Decrease formation of protective prostacyclin
Increase cardio risks

26

Paracetamol discuss

Not an nsaid
Does not decrease inflamation but is an analgesic
Interacts with cox enzymes at different sites to nsaids?
Or interacts with endocannabinoid system?

27

Why dont you take paracetamol with alcohol?

Both metabolised by liver enzyme cytochrome p450
By products are free radicals, these require endogenous antioxidants (glutathione) in liver
But these are saturated

28

Endogenous antioxidant

Glutathione

29

What is referred pain?

Tissue damage in viscera feels like its coming from bodys surface

30

Mechanism of refered pain

Neurones from viscera and skin synapse on the same dorsal horn neurone
Brain cannot distinguish location of pain

31

What is sensitisation?

Damaged tissue releases inflam mediators that decrease activation threshold of nociceptors
Activation threshold of noicipetors is lowered
Pain extends beyond area of tissue damage
Protective mechanism but may be bad long term as receptor population in dorsal horn changes

32

Why dont you give asprin to children?

Linked to reyes syndrome
Especialy if they have a virus

Something to do with impaired mitochondria