Pain and Nocioception Flashcards

1
Q

What is pain?

A

Pain is an unpleasant sensory experience which may be associated with tissue damage

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2
Q

What is nociception?

A

Detecting and stimulation by noxious stimuli which cause tissue damage

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3
Q

What are the benefits of pain?

A

Avoid infection and harm, reduces our mobility to enable healing and be aware of our surroundings.

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4
Q

What is somatic pain?

A

Divided into superficial and deep pain.

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5
Q

What is superficial pain?

A

Pain in the skin which is highly localised.

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6
Q

What is deep pain?

A

Pain in the muscles, connective tissues, tendons or bones that is achy or sharp and localised.

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7
Q

What is visceral pain?

A

Pain in the organs which is poorly localised and vague.

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8
Q

What is acute pain?

A

Short term pain with an identifiable onset associated with pain and its function is to limit function as a warning for healing. It is associated with child birth and sports injuries.

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9
Q

What is chronic pain?

A

Pain with a duration over 3 months which is unpredictable and inconsistent severity even with treatment. There is no biological function and rest does not releive pain. This is associated with visceral pain, cancer pain and migraine.

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10
Q

How does nociception occur?

A

Detected by nociception down the primary afferent fibres to the odrsal root ganglion of the spinal cord to be transmitted via the dorsal horn to the brain.

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11
Q

What are nocioceptors?

A

Unspecialised nerve endings in the skin and tissues which respond to noxious stimuli. They are characterised by their axons and their receptor channels.

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12
Q

What are the types of nociceptors?

A

Mechanical, chemical, thermal, polymodal and silent nocioceptors

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13
Q

What is the mechanical nociceptor?

A

Responds to painful mechanical pressure on via the a-delta fibres.

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14
Q

What is the thermal nociceptor?

A

Transmits information about painful extreme temperature to the brain via the a-delta or c-fibres

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15
Q

What are the chemical nociceptors?

A

Transmits information about chemicals like irritants and food to the brain via the c fibres

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16
Q

What are polymodal nociceptors?

A

Detect thermal, mechanical and chemical noxious stimuli to the brain and have only c-fibres

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17
Q

What are sleeping/silent nociceptors?

A

Respond to inflammation following injury via c-fibres

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18
Q

How are nocicpetors characterised?

A

Based on their axon properties and receptor channels

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19
Q

What are the primary afferent fibres?

A

Axons/unspecialised nerve endings which respond to stimuli and classified by their diameter; a-alpha, a-beta, a-delta and c fibres

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20
Q

What are the A-alpha and A-beta fibres?

A

A-alpha has the largest diameter and highest conductivity and velocity and responds to propioception of skeletal muscle.

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21
Q

What are the A-beta fibres?

A

A-beta fibres have a large diameter with a fast conductivity to respond to non-painful mechanoreceptors in the skin

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22
Q

What are the Alpha-gamma and C fibres?

A

Alpha-gamma and C-fibres are afferent fibres of axons with a smallest diameter and a slow conductvity for nociception.

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23
Q

What are the a-delta fibres?

A

Axons/ unspecialised nerve endings with slow conductivity to respond to pain and temperature present in thermal nociceptors.

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24
Q

What are the C-fibres?

A

Axons/unspecialised nerve endings with the smallest diameter and slowest conductivity to respond to pain, temperature and itching. It is found in polymodal nociceptors, thermal nociceptors and silent nociceptors.

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25
Q

What is 1st pain?

A

Sharp localised pain in the skin with a fast onset and short duration driven by the a-delta fibres. Responsible for acute pain.

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26
Q

What is 2nd pain?

A

Dull/vague poorly localised pain with a slow onset and long duration driven by the c-fibres. Responsible for chronic pain.

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27
Q

What are first order somatosensory neurons?

A

Transduce information about the internal/external environment of the body to the spinal cord.

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28
Q

What are second order neurons?

A

Transduce information from the spinal cord to the thalamus

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29
Q

What are third order neurons?

A

Transduce information from the thalamus to the primary sensory cortex.

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30
Q

What are the Na+ channel nociceptors?

A

Na1.1, Na1.6, Na1.7, Na1.8

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31
Q

How is pain transduced?

A

From peripherals-> spinal cord dorsal horn-> contralateral path to the thalamus-> somatosensory cortex Via the spinothalamic pathway.

32
Q

How do first and second order neurons synapse in the spinothalamic pathway?

A

Receptors detect noxious stimuli and generate receptor potential that depolarises the membrane. This activates voltage gated Na+ channels to generate action potential down the axon of A-delta/C-fibres to the soma of the dorsal root ganglion of the dorsal horn of the spinal cord at lamina 1 and lamina 2. They ascend and decussate at the ventral white commisure and voltage gated Ca2+ channels are activated and vesicles of glutamate and substance P are released.They synpase at lamina 4 and 5.

33
Q

How do second and third order neurons synapse in the spinothalamic pathway?

A

These cross at the midline and ascend contralaterally via Lissauer’s tract and pass through the medulla to travel to the thalamus. It synapses with third order neurons to project to the somatosensory cortex of the cerebrum.

34
Q

What is congenital analgesia?

A

Inability to detect noxious stimuli due to mutations in Na 1.1, 1.6,1.7 and 1.8 channels.

35
Q

What is the consequences of congenital analgeisa?

A

Shortened life expectancy, frequent bruising, limb deformities due to improper healing

36
Q

How do the afferents terminate in the spinal cord?

A

At lamina 1 and 2

37
Q

What is the spinothalamic pathway?

A

Pathway for nocioception to the brain

38
Q

What is the reticular formation and how does nociception affect this?

A

Brainstem nuclei stimulated by nociception for alertness

39
Q

What is the hypothalamus limbic system and how does nociception affect this?

A

Centre of the limbic system of the brain for behavioural response, stimulated by nociception for emotional response to pain

40
Q

What is the role of the thalamus in nociception?

A

Perception of pain

41
Q

What is the role of the somatosensory cortex in pain?

A

Localisation of pain

42
Q

What is the dorsal column-medial lemniscal pathway used of?

A

Touch, vibration and propioception.

43
Q

How do first and second order neurons synapse in the medial leminiscus pathway?

A

Action potential is generated by mechanoreceptors which is transmitted by afferent fibres such as a-alpha and a-beta fibres to the dorsal ganglia for the dorsal horn of the spinal cord. They will leave the dorsal horn to enter the dorsal faniculus and ascend to the medulla.They synapses with second order neurons in the cuneate nucleus of the medulla which cross over to either side of the medulla and decussate to ascend as the medial leminiscus.

44
Q

What is sensory decussation?

A

When the second order axons in the medualla cross over to the other side.

44
Q

How do the second order and third order neurons synapse?

A

The second order neurons ascend the brainstem as the medial leminiscus to synapse with the third order neurons in the nuclei of the thalamus

45
Q

What is the difference between the spinothalamic pathway and the dorsal column-medial lemniscal pathway?

A
46
Q

What is the pars caudalis?

A
47
Q

What is the trigeminothalamic tract?

A

Nociception in the head. Afferent a-delta or c-fibres enter at the dorsal horn of pons via Cranial nerve 5, 7, 9 and 10. They decend in the spinal tregiminal tract to the brainstem and synapse with second order neurons in the pars caudalis of the medulla. The second dorder neurons ascend contralateally to the thalamus via the trigeminothalamic tract to enter the ventral posteriomedial nucleus and project to the cortex.

48
Q

What are the consequences of a unilateral spinal cord injury in the medial leminiscus pathway?

A

Below the lesion there will be no sensation of touch such as pressure or vibration or propioception on the ipsilateral side

49
Q

What are the consequences of a unilateral spinal cord injury in the spinothalamic pathway?

A

Below the lesion there is no pain on the contralateral side

50
Q

What is referred pain?

A

Visceral and subcutaneous nociceptors enter the spinal cord at the same route and target the same spinal neurons thtat causes organ pain to be experienced on the skin

51
Q

What is referred pain of the heart?

A

Upper back, left arm and hand.

52
Q

Where does pain in the pelvic region and anus indicate?

A

Bladder pain

53
Q

Where does pain in the side and lower back indicate?

A

Ureter pain

54
Q

Where does pain in the side and legs indicate?

A

Prostate pain

55
Q

What is phantom limb?

A

Sensation that a removed limb is still there. Experienced in 60-80% of amputees.

56
Q

What is a phantom limb pain?

A

Sensation of pain in an absent limb.

57
Q

How is phantom limb pain treated?

A

Primarily an issue with the somatosensory map being rearranged in the brain so exercises like the mirror trick, stump stimulation. Painkillers or surgery on the stump may be ineffective.

58
Q

What is the gate theory?

A

Placing pressure on pain site will cause activation of a-alpha and a-beta fibres that will block pain stimuli.

59
Q

What is the central modulation of pain?

A

Pain sensation can be controlled in the brain such as powerful emotions, or intense concentration or belief such as placebo.

60
Q

What is hyperalgesia?

A

Nocioception caused by tissue damage or disease. Primary hyperalgesia is at the site of tissue damage. Secondary hyperalgesia is around the site of tissue damage. This is driven by C-fibres in response to inflammatory mediators

60
Q

What is allodynia?

A

Nocioception caused by light touch.

61
Q

wHAT IS FIBROMYALGIA?

A

Widespread pain with allodynia present greatly in women, with widespread ymtpoms such as irritable bowel syndrome. Treated with analgesics and antidepressants.

61
Q

wHAT IS FIBROMYALGIA?

A

Widespread pain with allodynia present greatly in women, with widespread ymtpoms such as irritable bowel syndrome. Treated with analgesics and antidepressants.

62
Q

What is the cause of disability no1 in Britain?

A

Back pain

63
Q

How can pain be releived?

A

Pharmacologically like Opioids, NSAIDS
Psychologically with a placebo or hypnosis
Neurosurgery to create a break in the nociceptive pathway
Stimulation of large fibres like touch
Physiotherapy
Acupuncture
Transcutaneuous electrical nerve stimualtion to areas of the brain
Cognitive releaxation techniques such as meditation

64
Q

How can opioids be used?

A

As an analgeisc

65
Q

What are the natural opioids?

A

Morphine

66
Q

What is a endogenous opioid?

A

Endorphin

67
Q

What is an opiate?

A

Opioids from opium poppy plant

68
Q

What is the periaqueductal grey?

A

Midbrain grey matter surrounding the cerebral aqueduct which can be stimulated to produce neurotransmitters for analgesic effects by blocking nonciception.

69
Q

What is the raphe nuclei?

A

Brainstem nuclei which has abundant 5-HT (histamine) neurons and neurotransmitters for analgesia

70
Q

What are the opioid analgesics?

A

Codein, fentanyl, tramadol, pethidine, morphine and diamorphine

71
Q

What is naloxone?

A
72
Q

How do opioids act on the nociception pathways?

A
73
Q

What is the mechnaism of opioids?
It is an agoni

A