1 - physiology of pain

Question 1

allodynia

Answer 1

sensitization. - abnormal response to touch

caused by lesion or trauma to nerve or CNS

Question 2

hyperalgesia

Answer 2

sensitisation - enhanced sensitisation to noxious stimuli following injury

normal response to injury

Question 3

somatogenic pain

Answer 3

pain with a physiological. cause

- localised in the body tissue

Question 4

2 types of somatogenic pain

Answer 4

a) nociceptive pain - picked up by a pain receptor and sent to the brain
b) neuropathic pain - damage to sensory nuerons along the pathway

Question 5

nueropathic pain

Answer 5

caused by damage at some point along the pathway of transmission eg. spinal cord

Question 6

nociceptive pain

Answer 6

starts at painreceptor andmessage sent to the brain

Question 7

pschyogenic pain

Answer 7

no known physical cause but processing of sensitive information in CNS is disturbed

Question 8

examples pf nociceptive pain

Answer 8

postoperative pain
mechanical lower back pain
arthritis
exercise and sports injuries

Question 9

neuropathicpain examples

Answer 9

CRPS (complex regional pain syndrome)
trigeminal neuralgia 
central post-stroke pain 
distal polyneuropathy (diabtic, HIV) 
neuropathic lower back pain 
postherpetic neuralgia

Question 10

mechanical pain

Answer 10

prickingm stabbing, pinching

Question 11

thermal pain

Answer 11

burning, freezing

Question 12

chemical pain

Answer 12

aching, stinging, soreness

Question 13

fast pain

Answer 13

sharp and well localised
transmitted by myelinated axons 
glutamate neurotransmitter 
- extremely rapid acting 
- very short duration

Question 14

slow pain

Answer 14

dull aching sensation
transmitted by unmyelinated axons 
substance P neurotransmitter 
- slower acting 
-long duration

Question 15

visceral pain

Answer 15

very poorly localised (lacks tactile afferents)

referred pain

Question 16

fast pain is transmitted by

Answer 16

myelinated axons

glutamate neurotransmitter

Question 17

slow pain is transmitted by

Answer 17

unmyelinated axons (C fibres)
substance P neurotransmitters

Question 18

TRP channels

Answer 18

transient receptor potential channels
temperature sensitiveion channels
excitatory Na+/Ca2+ channels

Question 19

cold receptors

Answer 19

TRPM8 channels

- firing rate increases as temp decreases

Question 20

hot receptors

Answer 20

TRPV1/3 channels

firing rate increases as temp increases

Question 21

freezing or burning can excite

Answer 21

any nocioceptor

Question 22

damage can excite

Answer 22

any nocioceptor

Question 23

specific mechanical nocioceptors

Answer 23

receptors with stretch gated ion channels
Na+/Ca2+ channels - excitatory
excited by strong pressure, pinch or squeezing
high threshold
mediate pain from skeletal muscle or viscera due to excessive stretch or contractile force

Question 24

exogenous chemicals that can penetrate the skin

Answer 24

acid, alkali, organic molecules

capsaicin, mustard oil

Question 25

intracellular molecules released by cell injury

Answer 25

cations (K+, H+) peptides, neurotransmitters prostaglandins, histamine, bradykinin

Question 26

things that chemical nociceptors respond to

Answer 26

- exogenous chemicals that penetrate skin - intracellular molecules released by cell injury - pathological substances released by diseased tissue - toxins - from microorganisms,insect bites, venom

Question 27

polymodal nociceptors

Answer 27

receptive to all other painful stimuli - C fibres - unmyelinated free nerve endings - release glutamate and/or substance P - respond to head, cold, pinch and chemical stimuli - express multiple receptors

Question 28

chemicals causing sensitisation - sensitising soup

Answer 28

``` H+ norepinephrine bradykinin histamine K+ prostanoids purines interleukins tumor necrosis factor serotonin neuropeptides leukotrienes ```

Question 29

what does sensitising soup do

Answer 29

turns a nociceptor from having a high threshold to. a low threshold

Question 30

neospinothalamic tract

Answer 30

fast, sharp only has 2 synapses myelinated sensory neuron, synapses at the spinal cord, up the anterolateral pathway to the thalamus, synapses and then goes to the cortex

Question 31

branching in neospinothalamic tract

Answer 31

nearly no branching

Question 32

somatosensory cortex gives

Answer 32

localisation

Question 33

insular cortex gives

Answer 33

intensity of pain

Question 34

anterior cingulate cortex

Answer 34

pain emotional reaction

Question 35

hypothalamus and limbic cortex gives

Answer 35

body physical response to pain | subjective memory of pain

Question 36

role of the efferent analgesic system

Answer 36

inhibition of afferent pain signals

Question 37

pain afferents stimulate neurons in

Answer 37

periaqueductal grey region (PAG) locus coeruleus (pons) nucleus raphne magnus

Question 38

neurons stimulated by pain afferents activate

Answer 38

descending anti-nociceptive pathways | transmitted through the spinal cord to the dorsal horn

Question 39

anti-nocciceptive pathwyas

Answer 39

release neurotransmitters | cause analgesia

Question 40

which neurotransmitters are released by anti-nociceptive pathways

Answer 40

serotonin, noradrenaline enkephalins, endorphins inhibit or block transmission of nocicceptive signals

Question 41

gate-control theory

Answer 41

neurons will talk to and suppress each other inhibitory interneurons prevent non-damaging pain from getting through. always active when there is only a low level of action potentials, pain doesn't transmit eg. don't feel pain just from sitting on a chair

Question 42

gate control when there is s strong pain stimulus

Answer 42

the nociceptive inhibits the inhibition interneuron | the fibres override the internuerons inhibition, pain is able to travel to the brain

Question 43

confusion of the nervous system

Answer 43

'rub it better' lateral inhibtion from sensory fibres activate inhibitory interneurones if both pain stimulus and non pain stimulus arrive at the same time, there will be partial inhibition of pain transmission

Question 44

opiates

Answer 44

act centrally by inhibiting neurotransmission of afferent neurons

Question 45

a2-adrenergic agonists

Answer 45

ie. clondine act centrally stimulate endogenous anti-nociceptive neurones

Question 46

local aneasthetics

Answer 46

block action potential conduction in nociceptive nerve fibres cation channel blockers lidocaine

Question 47

anti-inflammatory drugs + aspirin

Answer 47

can reduce hyperalgesia and allodynia | blocks prostaglandin production

Question 48

congenital analgaesia

Answer 48

hereditary sensory neuropathy (sensation is inhibited) specific to pain - nociceptive stimuli are not produced, processed and/or integrated

Question 49

causes of congenital analgesia

Answer 49

- increased anti-nociceptive pathways activity - high endorphins - SCN9A (a nociceptive specific Na channel) mutations - PRDM12 (a gene essential for nociceptor neurone development) mutations