20.1

Question 1

What are the 4 sensory processes in sensation of pain?

Answer 1

Transduction (detection of stimulus), transmission, perception and modulation.

Question 2

What are the 2 major classes of pain?

Answer 2

Adaptive/protective, and maladaptive/pathological.

Question 3

In adaptive and protective pain, what are the 2 types of pain?

Answer 3

Nociceptive and inflammatory pain

Question 4

In maladaptive and pathological pain, what are the 2 types of pain?

Answer 4

Neuropathic and functional pain syndromes

Question 5

What are the 2 components of perception of pain?

Answer 5

Sensory/discriminative - intensity and location of pain.

Emotional/aversive.

Question 6

The sensory process of ‘perception’ of pain is only possible if the person is ___.

Answer 6

Conscious.

Question 7

Nociceptor nerve endings are ___ nerve endings.

Answer 7

FREE

I.e. there is no specialisation of the nerve ending

Question 8

There are two types of fibres of nociceptors:

Answer 8

C-fibres

Adelta fibres

Question 9

The cell bodies of nociceptors are located in the ___ ___ ___ or the ___ ___ (for pain from face).

Answer 9

Dorsal root ganglia

Trigeminal ganglia

Question 10

C-fibres are ___ and transmission is ___

Adelta fibres are ___ and transmission is ___

Answer 10

C-fibres are unmyelinated and transmission is slow e.g. slow burning pain due to heat.
Adelta fibres are myelinated and transmission is fast e.g. sharp immediate pain due to heat.

Question 11

Compared to a touch receptor, nociceptors have ___ thresholds, and firing rate ___ after removal of the stimulus.

Answer 11

HIGH thresholds e.g. high levels of heat.
Firing continues (tonically) after removal of the stimulus esp. if damage to tissue.

Question 12

The concept of first and second pain is due to difference in the speeds of ___ and ___ fibres.

Answer 12

C and Adelta fibres.
First pain is due to Adelta fibres.
Second pain is due to C fibres.

Question 13

C-fibres and Adelta fibres transmit information into the ___ part of the ___ horn of the spinal cord.

Answer 13

Dorsal part of dorsal horn (i.e. right at the back in laminae/layers 1/2 of the cord grey matter).

Question 14

Nociceptor fibres synapse in the ___ ___ immediately on entering the spinal cord, then second order neurons decussate via the ___ ___ ___ and travel up the spinal cord in the ___ tract - this is called the ___ tract.

Answer 14

Dorsal horn
Anterior white commissure
Anterolateral tract
Spinothalamic tract

Question 15

Nociception can occur ___ of pain, e.g. in withdrawal reflexes from noxious stimuli.

Answer 15

Independent!

Question 16

Describe the withdrawal reflex to a noxious stimulus (i.e. afferent, synapses, efferents).

Answer 16

Nociceptor afferents synapse on second order neurons in the dorsal horn.
Second order neurons project from dorsal horn to neurons in ventral horn.
Ventral horn neurons innervate limbs -> withdrawal from noxious stimulus.

Question 17

Nociceptor afferents enter the spinal cord at ___ or ___ spinal segments above AND below its main level.

Answer 17

1 or 2 above and below.

Question 18

Inflammatory pain is a physiological response to ___ damage (like nociceptive pain)!

Answer 18

Tissue

Question 19

Inflammatory pain occurs because inflammatory cells interact with ___ nerve endings in tissue.

Answer 19

Nociceptor

Question 20

By interacting with nociceptor nerve endings, inflammatory cells can cause ___ pain, or pain ___.

Answer 20

Spontaneous pain

Pain hypersensitivity - i.e. decrease activation threshold.

Question 21

Chemicals can target ___ OR ___ channels on nociceptor nerve endings.

Answer 21

Receptors or ion channels

Question 22

What are the two levels of sensitisation i.e. amplification of pain signal?

Answer 22

Peripheral sensitisation e.g. inflammatory mediators change the threshold to painful stimuli.
Central sensitisation - occurs if inflammation is continuous, and is due to changes in spinal cord or brain.

Question 23

What are the two types of responses due to sensitisation?

Answer 23

Hyperalgesia - pain to noxious stimulus increases.

Allodynia - pain due to innocuous stimulus.

Question 24

What is secondary hyperalgesia?

Answer 24

Refers to expansion of the painful area.
Remember that branches of nociceptors go 1 or 2 levels above and below to different spinal levels -> central sensitisation to sensory nociceptors of undamaged areas!

Question 25

Neuropathic pain occurs due to injury to ___.

Answer 25

Nerves

Question 26

What are the different responses to nerve injury that result in peripheral neuropathic pain?

Answer 26

Sprouting of nociceptor nerve terminals in tissues or spinal cord. Injured nerves can independently generate APs -> pain. Changes in spinal cord that can be semi-permanent/irreversible.

Question 27

The ___ cortex, ___ cortex (S1) and ___ cortex are esp. important in pain.

Answer 27

Cingulate, somatosensory, insular.

Question 28

In the brainstem, structures esp. involved in pain are the ___ ___ (PAG) and the ___ ___ ___ (RVM).

Answer 28

Periaqueductal gray | Rostral ventral medulla

Question 29

There is a descending inhibitory/modulatory pathway from the ___ ___ to the ___ ___ ___ to the dorsal horn. Injection of drugs into ___ ___ or ___ ___ ___ -> pain relief.

Answer 29

Periaqueductal gray to rostral ventral medulla to dorsal horn.

Question 30

Hypoalgesia refers to ___ sensitivity to pain.

Answer 30

Decreased

Question 31

Hypoalgesia occurs due to activity of ___ pathways that inhibit and modulate pain transmission.

Answer 31

Descending