Pain

Question 1

Pain pathway

Answer 1

Nociception -> pain -> suffering -> pain behaviour

Question 2

3 sources of pain

Answer 2

1. trauma
2. inflammation
3. ischaemia

Question 3

Physiology of trauma

Answer 3

Neuronal - free nerve endings
Conducted by A delta fibres
Myelinated - fast pain, quick reaction

Question 4

Physiology of ischaemia and inflammation

Answer 4

Chemical - prostaglandins/histamine
Conducted by C fibres
Unmyelinated - delayed and continued pain

Question 5

Gate control theory

Answer 5

Pain conduction is modulated at the spinal cord by peripheral nerve impulses and impulses from the brain

Question 6

Gate-closing stimuli

Answer 6

Peripheral nerve stimulation (rubbing)

Mental state: endorphins, dynorphins and enkaphalins bind to ion-gated channels of post-synaptic nerve

Question 7

Gate-opening stimuli

Answer 7

Glutamate (most excitatory neurotransmitter) binds to receptors
Mental stress (lack of feel good chemicals)
Bradykinin and other inflammatory mediators

Question 8

Inflammation is caused by… in order to…

Answer 8

tissue damage

minimise consequences of damage and start repair

Question 9

Symptoms of inflammation (5)

Answer 9

Redness
Swelling
Heat
Pain
Loss of function

Question 10

3 stages of inflammation

Answer 10

1. Damage to blood vessel: compromises laminar blood flow, so cells start hitting endothelium on inside of vessel
2. Change in vascular permeability: joints in cell start leaking plasma and proteins, causing a drop in oncotic pressure and more fluid in interstial area
3. Leukocyte accumulation: leukocytes migrate and adhere to side of blood vessel, opening gaps between cells further so they can emigrate to damaged area
4. Phagocytosis of bacteria and damaged tissue and release of leukocyte product which dissolves foreign body

Question 11

Biochemical process of inflammation

Answer 11

1. Phospholipid from bilayer is acted on by phospholipase A2
2. Creates arachidonic acid
3. 5-lipoxygenase turns arachidonic acid into leukotrins, which attract white blood cells, cause vasoconstriction, bronchoconstriction, and vascular permeability
4. Cycloxygenase 1+2 turn arachidonic acid into prostaglandins, anticoagulants, and platelet activator

Question 12

Causes of ischaemic pain

Answer 12

Spasm causes blocked or narrowed blood vessels

O2 starvation

Question 13

Process of ischaemic pain

Answer 13

1. O2 starvation causes a lack of ATP
2. Cells generate energy anaerobically
3. Increased lactic acid
4. Increase in hydrogen ions
5. Increased acidity is perceived by pH sensitive nerves, which is converted to pain

Question 14

Acute pain

Answer 14

Less than 3 months
Response to a natural or therapeutic process
Response to trauma

Question 15

Chronic pain

Answer 15

More than 3 months
Typically not ‘useful’
Often caused by degeneration

Question 16

Mechanism of local anaesthetics

Answer 16

Stop nerve conduction by preventing sodium ion channels working

Question 17

Adverse effects of local anaesthetics (5)

Answer 17

Neurological disorders
Convulsion
Restlessness
Respiratory paralysis
Cardiac disorders - reduced impulse conduction

Question 18

2 areas of pain relief

Answer 18

Epidural - between dura matter and vertebral spines

Spinal block - next to spinal cord

Question 19

Mechanism of opioids

Answer 19

1. Mimic endorphins, dynorphins and enkaphalins
2. Bind to receptor on pre-ganglionc nerve
3. Prevent neurotransmitter release by opening K+ channels
4. Prevents depolarisation

Question 20

Adverse effects of opioids (10)

Answer 20

Cough centre depression
Sweating
Pupil constriction
Euphoria
Respiratory depression
Bronchial contraction
Vasodilation
Biliary spasm
Decreased peristalisis (constipation)
Increased bladder tone

Question 21

Types of opioid

Answer 21

Morphine
Codeine (less potent)
Pethidine (doesn’t cause constriction of smooth muscle, but is metabolised quickly)
Tramadol (synthetic)

Question 22

PK/PD lag

Answer 22

With opioids, the effect of drug is felt after drug levels have peaked, not at peak

Question 23

Non-opioid analgesics (2)

Answer 23

1. Non-steroidal anti-inflammatory drugs (NSAIDs), e.g. paracetamol or ibuprofen, inhibit cycloxygenase to reduce swelling and pressure
2. Corticosteroids stop formation of arychonic acid from phospholipid