Pain

Question 0

Why do you get referred pain?

Answer 0

Visceral fibres converge on the spinal-cord second order neurones and are shared by somatic nociceptors fibres so they converge

Question 1

Define pain

Answer 1

Unpleasant, sensory and emotional experience associated with actual or potential tissue damage

Question 2

What do you get with somatic pain in terms of different responses?

Answer 2

Pain elicits sensation with autonomic, somatic endocrine and emotional responses so you get release of cortisol, eyes dilating, increased BP etc

Question 3

Define nociception

Answer 3

Non-conscious neuronal traffic originating with trauma or potential tissue trauma

Question 4

What is the difference between the threshold and tolerance of pain?

Answer 4

Everyone has the same threshold
Tolerance people differ in and it increases with age it may also depend on physiological, psychological and emotional factors

Question 5

What the ascending tracts for pain?

Answer 5

The spinothalamic tract with the lateral in particular

Question 6

What are the stages of nociception?

Answer 6

Transduction which is the activation of nociceptors
Transmission which is relay of action potentials to the CNS
Modulation by other peripheral nerves or CNS mechanisms
Perception is the final result

Question 7

What are the different types of nociceptors?

Answer 7

Mechanical which have A delta fibres
Thermal which is also A delta fibres
Polymodal which is C fibres which is both mechanical and thermal

Question 8

Explain about unmyelinated C fibres.

Answer 8

These are unmyelinated and slow and have capacitance they carry pain and temperature sensation and are responsible for dull and throbbing pain

Question 9

Explain about A delta fibres

Answer 9

These are myelinated so are responsible for fast transmission of pain they don’t have a capacitance and they also carry pain and temperature they are responsible for fast, sharp and stabbing sensation

Question 10

What lamiae is the nucleus proprius?

Answer 10

IV and V

Question 11

What factors are released with tissue damage?

Answer 11

Histamine, prostaglandins, bradykinin, serotonin, potassium, hydrogen and substance P.
Substance P is released from nerve endings and increases the permeability of capillaries so contributes to inflammation. It also causes mast cells to release histamine causing activation of nociceptors and an action potential.
It works via a positive feedback mechanism.

Question 12

How do NSAID’s produce their analgesic effects?

Answer 12

Cox 1 inhibitors therefore decrease prostaglandins therefore decrease activation of nociceptors.

Question 13

What is thalamus, the limbic system and the hypothalamus responsible for in terms of pain?

Answer 13

Thalamus carries information on location and intensity
The limbic system is responsible for the emotional response
The hypothalamus is responsible for the stress response.

Question 14

What is congenital analgia?

Answer 14

A congenital condition in which no pain is felt at all
It is incredibly dangerous because there is no protective mechanism from painful stimuli which can result in significant tissue damage.
E.g. placing your hand on a hot radiator and not realising -> would lead to burns

Question 15

Why do we get acute pain?

Answer 15

It is a survival mechanism in order to protect our bodies from severe harm

Question 16

What is the definition of chronic pain?

Answer 16

Pain or discomfort persisting continuously or intermittently for three months or more

Question 17

What are the 2 main types of pain?

Answer 17

Nociceptive

Neuropathic

Question 18

Explain the gate control theory of pain

Answer 18

C and A delta fibres synapse with either lamina I or V to the transmission neurone.
Lamina II is the gate which is open or closed and sets the pain threshold this then it goes onto a transmission neurone the thalamus

Question 19

Explain the pathophysiology of hyperalgesia and allodynia

Answer 19

Hyperalgesia is increased pain at a normal threshold
Allodynia is increased sensitivity to pain where a normal person would not feel pain at all.
Chronic pain stimulates nerves which become hypersensitive
There is excess glutamate release, and excess NMDA receptor activation which results in wind up which is the basis of these two conditions.
This can lead to receptive field expansion and hyperexcitsbility of neurones

Question 20

What is chronic pain often due to?

Answer 20

Nociceptors
Neuropathic
Mixed pain
It involves changes in the spinal cord such as increased calcium and sodium channels and also wind up the brain also remaps

Question 21

What is neuropathic pain caused by?

Answer 21

Nerve damage

It is pain of neuronal origin and very difficult to treat

Question 22

After you prefer nerve injury, sensation occurs which can lead to any of what?

Answer 22

D crease threshold of nociceptor activation
Increased receptive field expansion
Allodynia
Hyperalgesia
Hyperpathia
Emergence of spontaneous activity due to sodium channel up-regulation

Question 23

Explain phantom limb pain

Answer 23

This is a pain felt by amputees.
The nerve ending is still present and it also has a part still in the homunculus.
Therefore sensation can still travel to brain
The homunculus however, can remap and therefore you can get sensation in the phantom limb by stimulating other parts of the body for example touching the lip can sometimes lead to phantom limb pain because more area is given to the lip in the homunculus.

Question 24

What are the two types of complex regional pain syndrome?

Answer 24

Type one where there is no identifiable lesion

Type two where there is an identifiable nerve lesion

Question 25

Explain the epidemiology of complex regional pain syndrome

Answer 25

It tends to occur in about the fourth decade
It is 2 to 3 times more common in females
It usually involves a single limb at first
There is usually 30 months before diagnosis and after symptom onset.

Question 26

What is complete regional pain syndrome caused by?

Answer 26

Minor trauma
Bone fracture
Surgery
Stroke
MI

Question 27

What are the signs and symptoms of complex regional pain syndrome?

Answer 27

Oedema, redness, clammy extremities, allodynia, hyperalgesia, trophic effects, contractures, atrophy, burning pain

Question 28

What is the mechanism of complex regional pain syndrome?

Answer 28

An original injury is carried to the brain
The pain impulse then triggers the sympathetic nervous system which returns to the site of injury
The sympathetic impulse triggers inflammation and vasospasm leading to oedema and increased pain
The pain triggers another cycle

Question 29

What are the three stages of complex regional pain syndrome?

Answer 29

1 acute
2 dystrophic
3 atrophic

Question 30

What is cancer pain caused by?

Answer 30

Neuropathic due to invasion
Nociceptive due to inflammation
Drugs for example methotrexate

Question 31

What are the effects of opioids?

Answer 31

Nausea
Vomiting
Euphoria
Analgesia
Respiratory depression
Itching
Constipation

Question 32

What are the three types of opioid receptors and what type of receptor are they?

Answer 32

Mu, Delta, kappa

They are GPCR and inhibit neurotransmitter release

Question 33

Where are opioid receptors found?

Answer 33

Myenteric plexus which is why they cause constipation
Hippocampus which is why they cause memory loss
The brainstem which is why they cause respiratory depression
The heart, vas deferens, spinal-cord, thalamus and hypothalamus, cortex

Question 34

Give some examples of weak opioids

Answer 34

Tramadol
Codeine
Dihydrocodeine

Question 35

Give some examples of strong opiods

Answer 35

Morphine
Oxycodone
Hydromorphone
Diamorphine
Fentanyl

Question 36

What can you give for opiod insensitive pain?

Answer 36

Antidepressants
Anticonvulsants
Local anaesthetics
Spinal analgesia