Pain Flashcards

0
Q

Types of pain:

Neuropathic

A

Neuronal damage by inflamation

Post-herpetic neuralgia, cancer pain, diabetic neuralgia

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1
Q

Types of pain:

Noiciceptive

A

Stimulation of peripheral noiceptors

Limb fractures, sprains, burns

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2
Q

Types pf pain:

Psychogenic

A

Physical pain from emotional factors

Tension headache, back pain, stomach pain

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3
Q

Types of pain:

Phantom limb

A

Pain from removed limb

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4
Q

Why do we have pain?

A

Pain signals to brain that body has encountered a damaging stimulus

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5
Q

What two diseases improperly perceive pain?

A
Familial dysautonomia (disorder of ans)
Congenital insensitivity to pain and anhidrosis (mutation in ntrk1r for ngf)
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6
Q

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

A

High and fast

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7
Q

Types of nociceptors

A

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

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8
Q

A delta fibres

A

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

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9
Q

C fibres

A

Unmyelinated
Small diameter
2m/s
90% of pain

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10
Q

Reticular formation of brain

A

General onset of pain

Origin of descending analgesic pathways

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11
Q

Thalamus

A

Spinothalamic tract, sends efferents to map pain

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12
Q

Periaquiductal grey

A

Relays between ascending and descending pathways

Lesion does not increase pain threshold or reduce analgesia

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13
Q

Under what may pain be supressed?

A

Stress
Opiods

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

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14
Q

Brain areas involved in descending pain pathways

A

Rostral ventral medulla
Periaquiductal gm

Contain lots of opiod receptors

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15
Q

Role of descending pathways in pain

A

Descend to spinal cord and inhibit release of substance p

16
Q

How do opiods work?

A

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

17
Q

Endogenous opiods

A

Enkephalins, dynorphin, endorphin

18
Q

Endogenous cannabinoids

A

Anandamide and 2-aracidonyl glycerol

Stress induced analgesia partially blocked by rimonabant

19
Q

Name nsaids

A

Asprin, ibuprofen, naproxen, indomethacin

20
Q

Role of nsaids

A

Decrease inflammation, decrease sensitiation, decrease fever (antipyretic)

21
Q

Analgesic effects of paracetamol and nsaids

A

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

22
Q

Mechanism of action of nsaids

A

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
Q

Role of cox1

A

Products protect the stomach from acid enviornment

Blocked by asprin, non selective nsaids

24
Q

Role of cox2 and inhibitors

A

Products recruit inflamation, wbcs, sensitise oain, stimulate fever

Blocked by asprin, nonselc nsaids, cox inhibs

25
Q

Cox2 selective inhibitors discuss.

A
Rofecoxibs, celocoxibs
Protect stomach
Increase formation of thromboxane
Decrease formation of protective prostacyclin
Increase cardio risks
26
Q

Paracetamol discuss

A

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
Q

Why dont you take paracetamol with alcohol?

A

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

28
Q

Endogenous antioxidant

A

Glutathione

29
Q

What is referred pain?

A

Tissue damage in viscera feels like its coming from bodys surface

30
Q

Mechanism of refered pain

A

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

31
Q

What is sensitisation?

A

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
Q

Why dont you give asprin to children?

A

Linked to reyes syndrome
Especialy if they have a virus

Something to do with impaired mitochondria