Physiology and Pathophysiology of Pain

Question 1

what is the 1st step of processing pain?

Answer 1

Periphery:
Detection
Transmission to spinal cord (first order neurons)

Question 2

what is the 2nd step of processing pain?

Answer 2

Spinal cord:
Processing
Transmission to brain (Thalamus) (second order neurons)

Question 3

what is the 3rd step of processing pain?

Answer 3

Brain:

Perception, learning, response

Question 4

what is the 4th step of processing pain?

Answer 4

Modulation:

Descending tracts

Question 5

What is nociception?

Answer 5

The detection of tissue damage by specialized transducers connected to A-delta and C fibers

Question 6

what are nociceptors?

Answer 6

Free nerve endings of A delta and C-fibres

Respond to thermal, chemical, mechanical noxious stimuli

Question 7

describe Primary afferents?

Answer 7

Cell body in Dorsal root ganglion
First order neurons
Synapse at spinal cord

Question 8

what are the 4 different types of Primary afferents?

Answer 8

Aα fibres
Aβ fibres
Aδ fibers
C fibres

Question 9

what neurones receive the input from Rexed lamina 2 and 5?

Answer 9

Nociceptive specific
Low Threshold Mechanoceptive
Wide Dynamic Range

Question 10

where does the Spinothalamic tract arise in?

Answer 10

Rexed Lamina 2 & 5

Question 11

what is the Spinothalamic tract ?

Answer 11

Major ascending tract for nociception

sending impulses to thalamus

Question 12

what is the second relay station in the brain?

Answer 12

thalamus

Question 13

where does the Lateral Spinothalamic Tract terminate?

Answer 13

Ventroposterior thalamic nuclei

Question 14

The medial thalamic nuclei receives input from where?

Answer 14

ventral spinothalamic tract

Question 15

where does the Ventroposterior thalamic nuclei project to?

Answer 15

somatosensory cortex

Question 16

where does the medial thalamic nuclei project to?

Answer 16

Cortex

Limbic system

Question 17

where does Pain perception occur?

Answer 17

somatosensory cortex

Question 18

what is the primary control center for descending pain modulation?

Answer 18

Periaqeductal grey

Question 19

describe the defending pathways of pain modulation?

Answer 19

from brain to dorsal horn
Usually decreases pain signal
Noradrenergic system

Question 20

what is hyperalgesia?

Answer 20

abnormally heightened sensitivity to pain

happens whenever there is tissue injury and inflammation.

Question 21

what is allodynia?

Answer 21

Decreased threshold for response

Question 22

what is Spontaneous Pain?

Answer 22

Spontaneous activity in nerve fibres

Question 23

what is Central sensitization?

Answer 23

It is the response of second order neurons in the CNS to normal input both noxious & non-noxious

Question 24

what are the three main components of Central sensitization?

Answer 24

wind-up
classical
long-term potentiation

Question 25

what is the main difference between Central sensitization and peripheral sensitization?

Answer 25

central sensitization happens at the level of spinal cord and acts in tandem.

Question 26

what is wind-up Central sensitization?

Answer 26

Involves only activated synapses Homosynaptic activity dependent progressive increase in response of the neurons Manifests over the course of stimuli & terminates with stimuli

Question 27

what is Classical Central sensitization?

Answer 27

Involves opening up of new synapses (silent nociceptors) Heterosynaptic activity dependent plasticity Immediate onset with appropriate stimuli Outlast the initial stimuli duration Can be maintained even at low levels of ongoing stimuli

Question 28

what is Long-term potentiation

Answer 28

Involves mainly the activated synapses | Occurs primarily for very intense stimuli

Question 29

what is acute pain?

Answer 29

``` <1 month Physiological Presence of noxious stimuli Serves protective function Usually nociceptive ```

Question 30

what is chronic pain?

Answer 30

``` Pain for 3–6 months or more Pathological Presence of noxious Does not serve any purpose Nociceptive, neuropathic or mixed ```

Question 31

What is nociceptive pain?

Answer 31

A sensory experience that occurs when specific peripheral sensory neurones (nociceptors) respond to noxious stimuli

Question 32

What is neuropathic pain?

Answer 32

Pain initiated or caused by a primary lesion or dysfunction in the somato-sensory nervous system

Question 33

describe nociceptive pain

Answer 33

Pain typically localised at the site of injury – often described as throbbing, aching or stiffness Usually time limited and resolves when damaged tissue heals Can be chronic Tends to respond to analgesics

Question 34

describe neuropathic pain

Answer 34

pain occurs in the neurological territory of the affected structure (nerve, root, spinal cord, brain) Almost always a chronic condition (e.g. postherpetic neuralgia [PHN], poststroke pain) Responds poorly to analgesics

Question 35

what are some examples of neuropathic pain?

Answer 35

postherpetic neuralgia [PHN] | poststroke pain

Question 36

what drugs are effective when transduction is affected structure?

Answer 36

NSAIDs Ice Rest LA blocks

Question 37

what drugs are effective when transmission is affected structure?

Answer 37

``` Nerve blocks Drugs Opioids Anticonvulsants Surgery DREZ Cordotomy ```

Question 38

what drugs are effective when Perception is affected structure?

Answer 38

``` Education Cognitive behavioural therapy Distraction Relaxation Graded motor imagery Mirror box therapy ```

Question 39

what drugs are effective when Descending modulation is affected structure?

Answer 39

``` Placebos Drugs Opioids Antidepressants Surgery Spinal cord stimulation ```