pain and analgesia (Abdel)

Question 1

What casues pain?

Answer 1

activation of nociceptors by thermal/mechanical/chemical ot other stimuli

Question 2

What is pain?

Answer 2

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

it is a perception

occurs in the brain

Question 3

types of nociceptive pain

Answer 3

visceral
somatic
referred
radiating
breakthrough
psychogenic
phantom

Question 4

visceral pain

Answer 4

diffuse, difficult to locate

referred to a distant, superficial, structure

Question 5

somatic pain

Answer 5

1. superficial pain - activation of nociceptors in skin/superficial tissue, shar/burning, well defined
2. deep somatic pain - activation of nociceptors in ligaments/bones/tendons/muscles, dull, aching, poorly localised

Question 6

referred pain

Answer 6

preceived at a location other than the site of the painful stimulus

Question 7

radiating pain

Answer 7

pain that spreads from the original area outwards to another part of the body

Question 8

breakthrough pain

Answer 8

transitory flare up of pain against a background of otherwise well controlled pain

Question 9

psychogenic pain

Answer 9

result of some underlying psychological disorder

Question 10

phantom pain

Answer 10

pain in a part of the body that has been removed surgically/traumatically

Question 11

What is neuropathic pain and conditions that experience it?

Answer 11

• after direct injurt to a peripheral nerve
• characterised by damage/dysfunction of somatosensory pathways in PNS/CNS AND pain/hypersensitivity within denervated zone and its surroundings
• DM, after traumatic injury, ischaemia, radiation therapy, excessive alcohol consumption, immune system disease, coeliac disease, viral infection

Question 12

most common cause of neuropathy

Answer 12

diabetic neuropathy

Question 13

types of diabetic neuropathy

Answer 13

1. peripheral/sensory neuropathy - affects mostly nerves of feet/legs
2. autonomic neuropathy - results from damage to nerves which control involuntary fxns
3. focal neuropathy - results from injury to periphral nerve at one site

Question 14

What is neuropathic pain insensitive to?

Answer 14

morphine and other opioids

Question 15

drug classes that can relieve neuropathic pain

Answer 15

TCAs (amitriptyline)

anticonvulsants (carbamazepina)

corticosteroids (dexamethasone) - esp cancer pain

Question 16

NICE recommended drugs effective for neuropathic pain

Answer 16

amitriptyline

duloxetine

gabapentin

pregabalin

Question 17

combination Tx for neuropathic pain

Answer 17

NOT recommended

Question 18

What is trigeminal neuralgia?

Answer 18

neuropathic facial pain condition

pain/loss of sensation in face

disorder of the 5th cranial nerve -> trigeminal nerve

severe paroxysmal, lancinating facial pain

Question 19

trigeminal nerve

Answer 19

5th (V) cranial nerve

largest cranial nerve (out of 12)

arises from brainstem

main nerve of sensation for the face

contains sensory fibres for facr

contains motor segment important for chewing/mastication

divides into 3 branches

Question 20

3 branches of the trigemnial nerve

Answer 20

V1 opthalmic division - provides sensation to forehead and eye

V2 maxillary division - provides sensation to cheek, upper lip, roof of mouth

V3 mandibular division - sensation to jaw and lower lip

Question 21

trigeminal neuralgia Tx

Answer 21

carbamazepina

Question 22

alternative Tx for trigemnial neuralgia

Answer 22

oxcarbazepine
gabapentin
phenytoin
baclofen
amitriptyline

Question 23

What to doif carbamazepine ineffective/c/i in trigeminal neuralgia?

Answer 23

get specialist advice

Question 24

What are sensory neurons described as?

Answer 24

pseudo-unipolar

-> have a single axon extending from the cell body that forms 2 extensions: dendrites and axon

Question 25

examples of sensory receptors

Answer 25

chemoreceptors - snese chemicals mechanoreceptors - sense touch, pressure, distortion/stretch, (vibrations fromsound waves) photoreceptors - sense light (retinas) thermoreceptors - sense temperature nocioceptors - repsond to a variety of stimuli (heat, pressure, chemicals) and SENSE TISSUE DAMAGE

Question 26

nociceptors

Answer 26

detect a wide range of stimuli chemical/physical stimuli excitate nociceptors by activating a single receptor excitatory neurons - release glutamate as their primary neurotransmitter have elevated stimulation threshold encode the intensity of a stimulus within the noxious range - must not saturat when a stimulus reaches noxious levels don't adapt to a persistent stimulus

Question 27

types of nociceptors

Answer 27

1. thermal - activated by noxious heat/cold at various temps 2. mechanical - respond to intense pressure and incisions that break skin surface 3. chemical - respond to variety of spices 4. polymodal - thermal, mechanical and chemical 5. silent/sleeping - become active when tissue becomes inflamed

Question 28

ascending pain pathway

Answer 28

neural projections where sensory info travells from periphery to brain

Question 29

pathways in the ascending pain pathway

Answer 29

1. dorsal column - 1st order neurons, mostly A alpha and A delta fibers 2. spinothalamic tract - lateral spinothalamic tract (A delta and C fibers) and anterior spinothalamic tract (A beta fibers) 3. spinocerebellar tract

Question 30

1st, 2nd and 3rd order neurons

Answer 30

1st order neurons - signals from periphery t spinal cord or medulla 2nd order - signals from spinal cord/medulla to thalamus 3rd order - signals from thalamus to primary sensory cortex

Question 31

decending pathway

Answer 31

modulatd pain sensation enhances or inhibits the conduction of pain includes: - anterior cingulate - insular cortex - PAG (periaqueductal gray) - nuclei in amygdala - PVG of hypothalamus (periventricular gray matter) - DLPT (dorsolateral pontine tegmentum) - RVM (rostral ventromedial medulla)

Question 32

NTs involved in decending pathway

Answer 32

``` opiodergic noradrenergic serotonergic cholinergic GABA-ergic endocannabinoids ```

Question 33

What area controls decending inhibitory modulation?

Answer 33

PAG - periaqueductal grey RVM and DLPT

Question 34

What neurons do the RVN and DVLP contain?

Answer 34

RVM - 5-HT neurons DVLP - NA neurons

Question 35

How does the decendng pathway work?

Answer 35

spinal cord received input from RVM 5-HT released - hyperpolarisation of ascending fibers/dornal horn when interacts with 5-HT 1 R - depolarisaiton of GABAergic interneurons, interacts with 5-HT2A, 5-HT3 R spinal cord receives input from DLPT AD released - hyperpolarisation of porjection neurons/primary afferent fibres, interacts with alpha2A R and apha2B/B Rs - depolarisation of dorsal horn/interneurons, interacts with alpha-1A R

Question 36

glutamate and pain

Answer 36

associated with acute pain good/warning pain

Question 37

substance P and pain

Answer 37

intense, persistent, chronic pain ad/damage injury pain

Question 38

prostaglandins and pain

Answer 38

potentiate the pain of inflammation by blocking the action of glycine