Oral Somatosensory System

Question 1

What is the somatosensory system?

Answer 1

Part of the sensory system concerned with touch, pressure, pain, temp, position, movement, vibration which arise from muscles joints skin and fascia

Most of the discussion will be based on orofacial pain

Question 2

What are the components of pain experience?

Answer 2

Sensory-discriminative: Localisation, intensity discrimination, quality of noxious stimulus

Moitivative-affective: Emotion, arousal and pain behavior, how the individual reacts, influenced by prior experience, expectations, possible, misconception.

*Orofacial pain is unique: Life-sustaining physiological processes

Question 3

What is nociception?

Answer 3

Neurochemical process that detects noxious stimuli (mechanical, thermal, chemical)

Question 4

What could happen to nociception on the way to the brain?

Answer 4

Nociception is either, amplified, reduced, or inhibited on the way to the brain

Question 5

What are the 2 categories of pain?

Answer 5

Somatic and Visceral pain:

Somatic pain: Noxious stimuli from structures of the body. Normal and physiological, may be superficial or deep.

Visceral pain: Internal organs, diffuse and difficult to localize, tooth pulp.

Question 6

What is non-nociceptive pain?

Answer 6

Neuropathic pain: Abnormalities of the nervous system with no need for noxious stimuli, may be spontaneous, no protective role, episodic or continuous neuropathic pain

Psychogenic pain: Patients report pain without evidence of tissue damage or physiological cause, caused by psychological stress, no neurophysiological basis for pain, exaggerated pain and unresponsive to treatment.

Question 7

Watch video of trigeminal neuralgia

Answer 7

Very common to be seen by dentists

Question 8

What are the features of neuropathic pain?

Answer 8

Abnormalities of the nervous system with no need for noxious stimuli

May be spontaneous

No protective role

Episodic or continuous neuropathic pain

Question 9

What is orthodromic and antidromic conduction?

Answer 9

Orthodromic = Conduction in normal direction

Antidromic = Conduction in opposite direction

Question 10

What do glial cells do?

Answer 10

Maintain chronicity of pain

Question 11

Every year question bout the free nerve endings 3 types of nocieptors. What are they?

Answer 11

Thinly myelinated A-delta fibers FAST

Unmyelinated polymodal C fibers SLOWER

Silent/sleeping nociceptors PATHOLOGY

Large diameter, myelinated fibers A-alpha, A-beta and A-gamma transmite tactile and proprioceptive impulses to CNS

Question 12

Which is faster of the nociceptors

Answer 12

Thin myelinated is faster

Unmyelinated C-fibers slower

Silent/sleeping involved in pathology

Question 13

What is central sensitization?

Answer 13

Central sensitization causes hypersensitivty in pain. Allodynia and hyperalgesia are features of this

Question 14

What is allodynia?

Answer 14

Allodynia = light touch hurts

Question 15

How does the trigeminal system work?

Answer 15

Nociceptive information from head and face is transmitted to CNS via afferent fibers of trigeminal system.

Trigeminal system has mixed sensory and motor nerves

Question 16

How does the trigeminal system work?

Answer 16

Nociceptive information from head and face is transmitted to CNS via afferent fibers of trigeminal system.

Trigeminal system has mixed sensory and motor nerves

Question 17

What is the function of the thalamus?

Answer 17

Acts as a relay center. Acts to amplify or inhibit pain.

Question 18

What does convergence of pain do to nociception?

Answer 18

Convergence makes pain referral possible from different teeth and so confusion is very possible in practice

Question 19

What are the parts of the trigeminal brainstem complex?

Answer 19

3 parts:

Trigeminal main sensory nucleus

Trigeminal spinal tract nucleus

Motor nucleus of the trigeminal nerve

Question 20

What kind of stimuli do A-beta fibers respond to?

Answer 20

Light touch. When there is inflammation and nerve injury they can transmit impulses that are perceived as pain (Allodynia)

Question 21

What kind of stimuli do A-delta fibers respond to?

Answer 21

Intense mechanical and thermal sensations

Question 22

What kind of stimuli do C-fibers respond to?

Answer 22

Thermal

Mechanical

Chemical

Question 23

What velocity do A-beta, A-delta, and C-fibers transmit signals at?

Answer 23

A-beta = 40 - 70 m/sec

A-delta = 2.5 - 25 m/sec

C-fibers = 0.5 - 2.5 m/sec

Question 24

What are silent nociceptors and how do they act?

Answer 24

They are usually dormant in healthy tissues but are sensitive to chemical release following tissue injury and then respond to mechanical stimuli.

They respond to high intensity stimuli with added input from A-delta and C-fibers

Question 25

How do second-order neurones affect pain signals?

Answer 25

Increase in responsiveness in second-order neurones is called central sensitization

Question 26

What is the difference between first and second pain?

Answer 26

A-delta nerve fibers transmit signal quickly leading to first pain which is short lasting and easy to localize and is sharp + stabbing pain.

C-fibers slow conduction velocity down leading to second pain which is felt as dull, deep, and burning pain