Neurophysiology of Nociception

Question 1

Define pain according to the international association of pain

Answer 1

An unpleasant sensory and emotional experience associated with actual or potential tissue damage

Question 2

What language did the word ‘nociception’ come from and what does it mean?

Answer 2

Latin word ‘nocere’ = to injure

Question 3

What is nociception?

Answer 3

Mechanisms that provide notice of potential noxious substances or stimuli or injury

Question 4

What is ganglion?

Answer 4

An encapsulated neural structure containing a collection of cell bodies of neurones

Question 5

What is an afferent nerve?

Answer 5

A sensory nerve passing impulses from receptors to the central nervous system

Question 6

What is an efferent nerve?

Answer 6

A motor nerve conveying information from the CNS to the muscles or glands

Question 7

What is a nociceptor?

Answer 7

A receptor on a neurone (nerve fibre) which detect the actual or potential noxious stimuli

Question 8

Pain in the orofacial region is transmitted mainly by the cranial nerve _, also known as the _______ ______. Exception angle of the jaw which is supplied by the ______ __________ _______.

Answer 8

V. Trigeminal nerve. Upper cervical nerves.

Question 9

What are the three branches (+/- divisions) of the trigeminal nerve?

Answer 9

Ophthalmic (V1)
Maxillary (V2)
Mandibular (V3) + anterior (mainly motor exception long buccal) and posterior (mainly sensory exception nerve to mylohyloid) divisions

Question 10

The _________ processes and relays sensory information to the varying parts of the brain. It plays a major role in ______ systems.
a) Thalamus, sensory
b) Thalamus, motor
c) Hypothalamus, sensory
d) Hypothalamus, motor

Answer 10

b) Thalamus, motor.

Question 11

The _______ ______ is responsible for memory, language skills and consciousness. It governs voluntary motor control.
a) Pituitary gland
b) Medulla oblongata
c) Cerebral cortex
d) Spinal cord

Answer 11

c) Cerebral cortex

Question 12

Algogenic substances are substances that are associated with signalling pain by activating or sensitising the nociceptors. What are the two algogenic substances that can be inhibited by analgesia?
a) Histamine, prostaglandins
b) Substance P, prostaglandins
c) Leukotrienes, prostaglandins
d) Bradykinin, prostaglandins

Answer 12

b) Substance P, prostaglandins

Question 13

Nociceptive path:
1. Tissue damage
2. Release of _______ substances (via _________ on either an A-delta fibre or a C fibre in the trigeminal afferents)
3. Trigeminal (Gasserian) ganglion
4. Via the sensory root joining the __________ at the level of the pons
5. TNC in the brainstem: motor nuclei and sensory nuclei (mesencephalic, principal, spinal)
6. Thalamus
7. Interpreted by the brain and individual feels pain
8. Descending (motor) response

Answer 13

Algogenic
Nociceptors
Brainstem

Question 14

Two types of nociceptive axons (fibres):
1) __-_______ (1st/fast) - fast, myelinated, respond to noxious high intensity mechanical stimuli
2) __-________ (2nd/slow) - slower, unmyelinated, respond to mechanical, thermal and chemical stimuli

Answer 14

A-delta
C-polymodal

Question 15

Which statement is true:
1) There is very little cross-over within the trigeminal ganglion. Therefore the topography of the impulses (the relationship between the site that generated the impulse and the impulse) largely stays the same going into the brainstem
2) There is a lot of cross-over within the trigeminal ganglion. Therefore the topography of the impulses (the relationship between the site that generated the impulse and the impulse) largely varies going into the brainstem.

Answer 15

1) Very little cross-over within the trigeminal ganglion. Topography of the impulses largely stays the same going into the brainstem.

Question 16

Within the brainstem, there is a sensory tract called the ________ ________ ________ (TNC). The primary afferents in the sensory root of the trigeminal nerve go into the sensory nuclei of the TNC which is composed of:
1. ___________ nucleus - responsible for proprioception from the periodontal ligaments and muscle fibres in the jaw close reflex
2. ___________ nucleus - responsible for proprioception for all orofacial behavious except for the jaw close reflex (eg kissing, smiling, talking)
3. ____________ (spinal tract or dosal nedullary horn) nucleus - receives the majority of the nociception from the primary afferents of the trigeminal nerve

Answer 16

Trigeminal Nucleus Caudalis
Mesencephalic
Principal
Spinal

Question 17

Second order neurones take the information from the synapses, made with primary afferents in the ________ nuclei, up the brainstem, and feedback to the ________ nuclei as they ascend which can be used to help modulate pain.
a) Mesencephalic
b) Principal
c) Spinal

Answer 17

c) Spinal

Question 18

Second order neurones travel to the __________ where they synapse with the third order neurones. These go to the higher centres in the brain which allow the individual to experience and interpret pain.
a) hypothalamus
b) thalamus
c) brainstem
d) cerebral cortex

Answer 18

b) thalamus

Question 19

A ________ (motor) response is sent out by the brain once it has interpreted the signals presented to it from the periphery.

Answer 19

Descending

Question 20

Other than altering stimulus or pharmacological alteration/interruption of nociception eg analgesia and anaesthesia, what are the two MAIN mechanisms of modulation?

Answer 20

1. Descending impulses
2. Sensitisation

Question 21

Descending impulses mechanism of nociception modulation:
Descending impulses, which are endogenous chemical messenger eg endogenous ___________, from the brain via 1 route: ___________ ______ ________ (mid brain) -> __________ (Nucleus Raphe Magnus) -> ____________ ________, affect the transmission of impulses from primary afferents

Answer 21

Opioids
Periaqueductal gray matter
Medulla
Trigeminal nucleus

Question 22

How descending impulses from the brain are generated is by gate control. This involves: as ____ signal becomes higher (very fast proprioception), it can inhibit the interpretation of the ______ or ____ fibre’s signals by the secondary neurones, therefore closing the gate, which brings further stimulus centrally.
a) Aβ, Aδ, C
b) Aδ, Aβ, C

Answer 22

a) Aβ, Aδ, C

Question 23

What does hyperalgesia mean?

Answer 23

Increase in painful signal

Question 24

What is allodynia?

Answer 24

Something that would normally not be interpreted as painful is very painful

Question 25

In peripheral sensitisation, peripheral nociceptors are inflamed and can have (increased/decreased) responsiveness or respond to (higher/lower) thresholds. Stimulus of nociceptors may also be more __________ and _______ (hyperalgesia).

Answer 25

Increased, lower, persistent, intense

Question 26

Peripheral sensitisation is caused by constant chronic tissue damage releasing continual algogenic substances involving first order neurones. This constant barrage:
* recruits sleeping/silent nocicepptors to (increase/decrease) impulses to the brain
* makes nociceptors (prone/not prone) to spontaneous activity
* (raises/lowers) nociceptive thresholds in nociceptors

Answer 26

Increase, prone, lowers

Question 27

How does central sensitisation (neuroplasticity) occur?

Answer 27

If second order neurones receive prolonged stimulus of nociceptive input

Question 28

When second order neurones are sensitised (central sensitisation/neuroplasticity), what can happen?

Answer 28

May increase strength of pain sensation (hyperalgesia)
May lead to painful sensation from otherwise non-painful trigger (allodynia)

Question 29

Central sensitisation (neuroplasticity) occurs as a result of a number of factors including:

Answer 29

• Nerve trauma
• Hormonal, genetic and environmental factors
• Local factors (peripheral sensitisation continuing beyond healing process)
• Psychological factors and emotions
• Glial cells
• Gender and ethnicity

Question 30

During convergence, the brain (cortex) struggles to tell which area an impulse originally came from. This results in __________ pain where the brain interprets a pain as coming from one area, but the pain is from elsewhere.

Answer 30

Referred

Question 31

Divergence is __________ of pain. It occurs because of potential for primary afferents to synapse several second order neurones therefore sending impulses to the brain that appear to be from a larger area than the original site of noxious stimulation.

Answer 31

Radiation

Question 32

Previously used terms: atypical odontalgia, primary dental alveolar pain, phantom tooth pain.
Description: unilateral, or rarely multiple sites of intra-oral dentoalveolar pain with varying presentations but recurring daily for more than 2 hours per day, over more than 3 months without close temporal preceding event
Diagnostic criteria: a) unilateral, or rarely multiples sites of intra-oral dentoalveolar pain fulfilling criterion B and C; b) recurring daily for >2 hours per day for >3 months; c) pain has both of the following characteristics - localised to dentoalveolar site or sites (tooth or alveolar bone) & deep, dull, pressure-like quality; d) clinical and radiographic examination are normal and no local cause may explain the pain; e) not better accounted for by another ICOP or ICHD-3 diagnosis
What is the pain described as above?

Answer 32

Persistent idiopathic dentoalveolar pain (PIDP)

Question 33

According to the biopsychosocial model of pain, how can persistent pain be managed?

Answer 33

Multidisciplinary management
Cognitive behavioural techniques (CBT) to manage pain better and improve quality of life

Question 34

Persistent orofacial pain is estimated to have a similar impact upon quality of life as _________ and ________ __________.

Answer 34

Depression
Rheumatoid arthritis

Question 35

Cognitive behavioural techniques (CBT) ~___% reduction in TMD patients pain after 1 year

Answer 35

50