PAIN AND NOCICEPTION Flashcards

1
Q

what is pain?

A

an unpleasant sensory and emotional experience associated with actual or potential tissue damage

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2
Q

what is nociception?

A

the neural processes of detecting, encoding and processing noxious stimuli

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3
Q

why is pain good?

A

it is an early cue to help protect our bodies from serious harm
it teaches us to avoid harmful situations
it forces us to rest an injured part of the body to allow tissue repair
it makes us toss and turn in sleep to prevent bedsores or skeletal strain

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4
Q

why is pain bad?

A

sometimes it serves no useful function e.g. in chronic pain

pain can persist even when tissues have healed

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5
Q

what is acute pain?

A

pain that resolves when the injury heals and is expected to end in days or weeks, it forces rest and avoidance of further harm. It is adequately treatable

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6
Q

what is chronic pain?

A

pain persists and duration is long and unpredictable. it has no biological function and rest does not improve pain. it is poorly treatable.

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7
Q

what is visceral pain?

A

pain from organs of the thorax and abdominal cavity. it is a dull aching pain or a vague burning that can be poorly located

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8
Q

what is somatic pain?

A

pain from skin (superficial) or muscles, joints, deep skin layers and connective tissue (deep)

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9
Q

what lasts longer superficial or deep somatic pain? what do they both feel like?

A

deep pain lasts longer

superficial pain is a pinching whilst deep pain is an aching, burning or itching pain

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10
Q

what are nociceptors?

A

free nerve endings found in most body tissues other than the brain that respond specifically to noxious stimuli

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11
Q

what is a noxious stimulus?

A

one that is actually or potentially a tissue-damaging event

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12
Q

what are the 5 types of nociceptors?

A
thermal
mechanical
chemical
polynomial
sleeping/silent
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13
Q

what are thermal nociceptors activated by?

A

extreme temperatre

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14
Q

what are mechanical nociceptors activated by?

A

excess pressure or mechanical deformation

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15
Q

what are chemical nociceptors activated by?

A

chemical stimulants

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16
Q

what are polymodal nociceptors activated by?

A

extreme temperature, excess pressure, mechanical deformation, chemical stimulants

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17
Q

what are sleeping nociceptors activated by?

A

inflammation

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18
Q

what are the 4 types of primary afferents?

A

A-alpha, A-beta, A-delta, C

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19
Q

which of the 4 primary afferents have large diameters and are myelinated?
what does this mean?

A

A-alpha and A-beta

they are rapidly conducting

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20
Q

what do A-alpha primary afferent carry?

A

information related to proprioception

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21
Q

what do A-beta primary afferent carry?

A

information related to touch

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22
Q

Which primary afferents have small diameters?

of these, which is unmyelinated?

A

A-delta and C

C fibres are unmyelinated so travel the slowest

23
Q

what do A-delta primary afferents carry?

A

information related to pain and temperature

24
Q

describe the fast, first pain?

A

brief, pricking, and well localized pain. information carried by A-delta afferents=fast

25
Q

describe the slower, secondary pain?

A

slow onset, longer-lasting, burning, and less well localized

carried by C fibres

26
Q

Briefly describe the ascending pain pathway?

A

nociceptors stimulated by noxious stimuli, receptor potential depolarises membrane and generates an action potential which propagates towards the spinal cord and enters via the dorsal horn. voltage gated Ca2+ channels trigger release of neurotransmitters which activates 2nd order neurones which cross over to the other side of the spinal cord. sensory input ascends via the spinothalamic tract up to the thalamus and then this is relayed to the somatosensory cortex via a 3rd order neurone.

27
Q

what is congenital analgesia?

A

an insensitivity to pain caused by a mutation in the genes encoding the Na+ channels specific to nociceptors.

28
Q

what are associated symptoms of congenital analgesia?

A

recurrent bruises, cuts, burns, scars, eye damage

limb and joint deformity due to improperly healed bones, missing body parts, reduced life expectancy

29
Q

what is Brown-Sequard syndrome?

A

a rare neurological condition characterised by a lesion in the spinal cord which results in weakness on one side of the body and a diminished sensation of pain on the opposite side.

30
Q

what is hemianesthesia?

A

a loss of sensation in either lateral half of the body

31
Q

what is referred pain?

A

when the pain you feel in one part of the body is actually caused by pain/injury in another part of the body

32
Q

what is referred pain caused by?

A

the nerves in the body are all connected

33
Q

what is a phantom limb?

A

a sensation that a missing limb is still attached to the body and is moving appropriately. can still get pain here.

34
Q

what are the treatments for phantom limb pain?

A

painkillers
mirror therapy
myoelectric prosthesis
stump stimulation

35
Q

what is the gate theory?

A

a proposed mechanism for how pain can be reduced by activating a non-painful sensation. This works by co-activation of A-alpha or A-beta fibres and C fibres as it surpasses activation of the projection neurone by C fibres. e.g. rubbing sore knee reduces pain

36
Q

Why can subjective interpretation of pain vary greatly from objective reality of a painful stimulus?

A

as perception of pain is modulated by higher brain centres. e.g. strong emotions can suppress pain

37
Q

what is physiological pain?

what is pathological pain?

A

acute

chronic

38
Q

what is hyperalgesia?

A

increased sensitivity to pain from a stimulus that normally provokes pain

39
Q

what’s the difference between primary and secondary hyperalgesia?

A

primary- occurs in the site of tissue damage

secondary - occurs around the site of tissue damage

40
Q

what is allodynia?

A

a condition in which pain is caused by a stimulus that does not normally elicit pain e.g. light tough or pressure

41
Q

what is fibromyalgia?

A

chronic wide spread pain and allodynia

42
Q

what are the treatment options for fibromyalgia

A

analgesics, antidepressants to reduce nerve firings, counselling, exercise (very difficult to treat)

43
Q

what are some pharmacological methods to treating pain?

A

opioids
NSAIDS
local anaesthetics
psychotropic drugs (affects mental state)

44
Q

what are some psychological methods to treating pain?

A
placebos
hypnosis
coping strategies
relaxation techniques
meditation
45
Q

what are some stimulation methods to treat pain?

A

transcutaneous electrical nerve stimulation which stimulates skin externally to reduce pain sensation internally
stimulate large fibres= gate control theory
acupuncture
physiotherapy

46
Q

what are some neurosurgical methods to treat pain?

A

create a physical break in the nociceptive pathway
cute dorsal roots (rhizotomy)
spinal cord hemisection

47
Q

where are endogenous opioids produced in the brain?

A

periaqueductual grey matter and raphe nuclei

48
Q

what are the 3 types of opioid receptors?

A

mu, delta, kappa

49
Q

how do opioids work?

A

they bind to opiod receptor on the axon terminals which inhibits the release of substance P from afferent pain fibres within the spinal cord. this rescued the transduction of pain to the spinothalamic pathway

50
Q

what is naloxone?

A

an opioid selective receptor antagonist which is used to reverse opioid-induced respiratory depression and overdose with opioids

51
Q

what are the indications for morphine?

A

severe pain in palliative care

52
Q

what are issues with repeated administration of morphine?

A

it can cause dependance and tolerance

53
Q

what are contra-indications of morphine?

A

above in acute respiratory depression and acute alcoholism

54
Q

what are some of the most common side effects of morphine?

A

nausea, vomiting, constipation, drowsiness, depression, hypotension