Lecture 3 Part 2: Pain

Question 1

what are the 3 types of pain

Answer 1

acute

chronic

referred

Question 2

what is acute pain

Answer 2

Clearly defined stimulus that determines the intensity and duration of pain

localized receptors (afferents) are affected

Question 3

what is the function of acute pain?

Answer 3

Detect tissue damage or impending damage; initiate
avoidance reaction

Question 4

what is chronic pain

Answer 4

Persistence of pain, often in absence of obvious stimulus

Cause & mechanisms are largely unknown so it’s difficult to treat

often involves changes in pain pathways

Question 5

what is referred pain?

Answer 5

pain caused in one body part but felt in another area

Question 6

why do we have referred pain?

Answer 6

Very few neurons in the dorsal horn of the spinal cord are specialized for transmission of visceral (internal) pain

Question 7

how are pain receptors similar to mechanoreceptors

Answer 7

arise from DRG

Transduce a variety of stimuli into receptor
potentials > trigger action potentials

frequency rate coding (more tumulus intensity more depolarization and more firing rate of pain afferents

Question 8

what are the 4 ways pain (nociception) is different from somatosensation (touch)

Answer 8

Specialized for damaging (nociceptive) stimulation

Information travels much more slowly

Localization is relatively poor

Repeated or prolonged stimulation often leads to a stronger response (sensitization), rather than adaptation

Question 9

what are the 4 specializations of nociceptors?

Answer 9

mechano-nociceptors (intense force)

thermo-nociceptors

chemo-nociceptors

nonspecific (respond to more than one type of stimuli)

Question 10

does the perception of pain (nociception) depend on specifically dedicated receptors and pathways or excessive stimulation of the same receptors that generate other somatic sensations?

Answer 10

specifically dedicated receptors and pathways

Question 11

what are the 2 types of fibers that carry from the free nerve endings

Answer 11

alpha delta (myelinated. but still slower than somatosensation)

c fibres (unmyelintated)

Question 12

why is localization poor with nociception

Answer 12

there’s large receptive fields with more branching

Question 13

what are the two aspects of pain

Answer 13

sensory-discriminative: (spinothalamic tract> VPL/VPM in thalamus > primary sensory cortex

affective-motivational: spinothalamic tract > anterior nuclear group in thalamus > anterior cingulate cortex or insular cortex

Question 14

what does the Sensory-Discriminative aspect tell us

Answer 14

location and intensity of pain

Question 15

what does the Affective-Motivational aspect of pain tell us

Answer 15

Unpleasantness of Pain Fear & anxiety

Autonomic activation (fight or flight)

Question 16

how do the Sensory-Discriminative and Affective-Motivational aspects of pain differ

Answer 16

they go to different places in the thalamus

Question 17

what is gate control theory?

Answer 17

non nocecptibe info from rubbing hand inhibits pain information or spinothalamic tract which stops the pain from going up into the thalamus

Question 18

what is the endogenous opioid theory?

Answer 18

natural occuring pain killers that brain sends down to spinal cord to stop pain transmission

Question 19

what is peripheral sensitization?

Answer 19

Interaction of nociceptors with ‘inflammatory soup’ of substances released due to tissue damage

swelling area around site of damage more susceptible to pain called hyperalgesia

Question 20

what is central sensitization?

Answer 20

Allodynia (painful sensation to non-painful stimuli) outside zone of terminal branching (of nociceptors) – not due to peripheral mechanisms – must be centrally mediated

Question 21

why does allodynia happen?

Answer 21

High excitability in dorsal horn

Activity levels in nociceptive afferents that were subthreshold prior to the sensitizing event become sufficient to generate action potentials in dorsal horn neurons, contributing to an increase in pain sensitivity

Question 22

what causes neuropathic pain

Answer 22

Damage to nerve structures themselves

Question 23

is pain just a sensory system

Answer 23

no it also activates motivational parts of the CNS