Physiology and Pathophysiology of Pain

Question 1

What is pain?

Answer 1

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

Question 2

Are pain and nociception the same?

Answer 2

No

Question 3

What is nociception?

Answer 3

The physiological process by which noxious stimulation is communicated through the peripheral and central nervous system

Question 4

Where does the perception of pain occur?

Answer 4

Somatosensory cortex

Question 5

What detects pain in the periphery?

Answer 5

Nociceptors

Question 6

Which neurons transmit the pain from the periphery to the spinal cord?

Answer 6

First order neurons

Question 7

Which type of neurons transmits from the spinal cord to the thalamus?

Answer 7

Second order neurons

Question 8

What happens when the pain information reaches the thalamus?

Answer 8

Perception, learning, response

Question 9

Nociceptors are free nerve endings of which types of fibres?

Answer 9

A delta and C fibres

Question 10

At which temperature does it become known as noxious stimuli range?

Answer 10

Above 42 degrees.

Question 10

Which type of things do nociceptors respond to?

Answer 10

Thermal, chemical and mechanical noxious stimuli

Question 11

The first order neurons carry fibres to which part of the spinal cord?

Answer 11

Cell body in dorsal root ganglion

Question 12

Which fibres transmit fast, sharp pain?

Answer 12

A delta fibres

Question 13

Which types of fibre transmits dull pain?

Answer 13

C fibres

Question 14

Where in the dorsal root ganglion do the first order neurons synapse?

Answer 14

Rexed lamina 1 and 2

Question 15

Give three characteristics of the neurons which receive the input from primary afferents.

Answer 15

1. Nociceptive specific
2. Low threshold mechanoreceptive
3. Wide dynamic range

Question 16

Which tract in the main ascending tract for nociception?

Answer 16

Spinothalamic tract

Question 17

Which rexed lamina does the spinothalamic tract arise from?

Answer 17

Rexed lamina 1, 2 & 5

Question 18

What is allodynia?

Answer 18

Pain due to a stimulus which does not usually provoke pain

Question 19

What changes are seen in the nociceptor in response to allodynia?

Answer 19

Decreased threshold for response

Question 20

What is hyperalgesia?

Answer 20

Abnormally heightened sensitivity to pain

Question 21

What changes are seen in the nociceptor in response to hyperalgesia?

Answer 21

Exaggerated response to normal and supranormal stimuli

Question 22

What changes are seen in the nociceptor in response to spontaneous pain?

Answer 22

Spontaneous activity in nerve fibres

Question 23

What is central sensitization?

Answer 23

Response of second order neurons in the CNS to both noxious and non-noxious stimuli

Question 24

There are three components of central sensitization; wind-up, classical and long-term potentiation. What is meant by wind-up?

Answer 24

Homosynaptic activity is dependant on the progressive increase in neuron response

Question 25

Which type of synapses does wind-up involve?

Answer 25

Only activated synapses

Question 26

Name the neurotransmitters involved in the process of wind-up.

Answer 26

Substance P CGRP

Question 27

What happens in classical central sensitization?

Answer 27

Involves opening up of new synapses and is responsible for a lot of pathophysiology

Question 28

Which synapses are involved in long-term potentiation?

Answer 28

Mainly activated synapses

Question 29

Which two things can pain be based on?

Answer 29

Duration e.g. chronic or acute Mechanism

Question 30

What are three mechanisms of pain?

Answer 30

Nociceptive Neuropathic Nociplastic

Question 31

Is acute pain physiological or pathological?

Answer 31

Physiological

Question 32

Is chronic pain physiological or pathological?

Answer 32

Pathological

Question 33

Which type of pain serves as a protective function?

Answer 33

Acute pain

Question 34

Which type of pain is nociceptive?

Answer 34

Acute

Question 35

Which type of pain can be nociceptive, neuropathic or neoplastic?

Answer 35

Chronic

Question 36

What is nociceptive pain?

Answer 36

A sensory experience that occurs when nociceptors respond to noxious stimuli

Question 37

Describe nociceptive pain.

Answer 37

-Pain usually localised to site of injury -Usually time limited -Tends to respond to conventional analgesics

Question 38

What is neuropathic pain?

Answer 38

Pain caused by a lesion or disease of the somato-sensory NS

Question 39

Describe neuropathic pain.

Answer 39

-Painful region may not necessarily be the same of the affected site -Predominantly chronic -Poor response to analgesics

Question 40

What is nociplastic pain?

Answer 40

Pain that arises from altered nociception despite no clear evidence of tissue damage, lesion or disease affecting the somatosensory system.

Question 41

Describe nociplastic pain.

Answer 41

-Stimulus independent -No inflammation/injury -No structural neuronal damage -Pathological -No protective or adaptive function -Due to central plasticity