Pain Pathways and Neurotransmission

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Questions and Answers

Which type of fibres carry nociceptive inputs in the trigeminal nerve?

Aγ fibres

Aα fibres

Aδ and C fibres (correct)

Aβ fibres

Which type of pain is characterized by being dull and poorly localized?

Cutaneous pain

Visceral pain

Pain carried by slow unmyelinated C fibres (correct)

Somatic pain

What is the primary location of cell bodies for 1st order neurons in the afferent pain pathway?

Midbrain

Dorsal horn of spinal cord

Sensory cortex

Dorsal root ganglia (DRG) (correct)

What is unique about the sensory perception from within tooth pulp?

There is no normal sensory perception Signup and view all the answers

Where do the afferent fibres of the trigeminal nerve terminate in the brain?

Ventroposterior nuclei of the brainstem and onwards to cortex Signup and view all the answers

Which of the following pain receptors is faster and myelinated, carrying sharp pain?

Aβ fibres Signup and view all the answers

What is the mechanism by which signals passing to 2nd order neurons are modulated in the spinal cord?

All of the above Signup and view all the answers

What type of convergence enables precise localization of pain from the skin surface?

Convergence with tactile stimuli Signup and view all the answers

Which division of the trigeminal nerve is not responsible for transmitting pain information from the orofacial region?

Vestibulocochlear nerve Signup and view all the answers

What is the primary difference between afferent impulses passing to the dorsal horn of the spinal cord and those passing to the brain stem in the Trigeminal nerve?

Anatomical structure Signup and view all the answers

What determines the severity of pain in the trigeminal region?

The balance of inputs from Aβ and Aδ, and C fibres Signup and view all the answers

What is the primary difference between pain pathways from teeth and oral cavity versus those from skin?

The modulating factors involved in pain transmission Signup and view all the answers

Which structure is responsible for modulating pain signals from the trigeminal nerve?

Sensory nuclei within the Spinal Tract of Trigeminal nerve Signup and view all the answers

What is the role of the 2nd order neurones in the pain pathway from the trigeminal nerve?

Modulation of pain signals by descending fibres Signup and view all the answers

What is the function of the 'Gate' in pain modulation?

To regulate the balance of pain signals Signup and view all the answers

Study Notes

Pain in the Trigeminal Region

Facial pain from the trigeminal nerve can be influenced by emotions, anxiety, and worry
Pain in the trigeminal region is similar to pain from other parts of the body
Central structures involved are similar to those in other parts of the body, but with differing anatomy and structures innervated

Toothache Pain

Pain from teeth and oral cavity is carried by:
- Faster myelinated Aβ and Aδ fibers carrying sharp pain
- Slow unmyelinated C fibers carrying dull, poorly localized pain
Cell bodies of 1st order neurons are in the Trigeminal ganglion
Signals pass to 2nd order neurons in the sensory nuclei within the Spinal Tract of the Trigeminal nerve

The 'Gate' Theory

Pain pathways from teeth and oral cavity are analogous to those from skin
Modulation of signals occurs in the sensory nucleus by the balance of inputs from Aβ and Aδ fibers and activity in fibers descending from higher centers
This is the site of the 'Gate' Theory of pain modulation

Pain Classification

Pain can be:
- Cutaneous
- Somatic
- Visceral

Trigeminal System Learning Objectives

To review the passage of afferent pain impulses to the dorsal horn of the spinal cord and their regulation
To consider the anatomical similarities and differences between afferent impulses passing to the dorsal horn of the spinal cord and those passing to the brain stem in the Trigeminal nerve
To site this discussion in the context of afferent impulses from the teeth
To emphasize that, although there are anatomical differences, the principles of the ‘Gate Theory’ hold true for the Trigeminal system

Trigeminal Nerve Anatomy

The Trigeminal nerve anatomy is broadly analogous to that of the peripheral nervous system, but has certain unique features that can influence pathological conditions
Processing of sensory information is carried out in similar regions of midbrain and sensory cortex
Unique structures (e.g., teeth) innervated by the Trigeminal nerve result in unique sensory characteristics

Peripheral Anatomy of Trigeminal Nerve

The Trigeminal nerve arises from the Pons just above the medulla and is mixed, with both afferent and efferent fibers, but afferent predominate
The ganglion (semi-lunar or Trigeminal ganglion) is equivalent to the dorsal root ganglion
The nerve splits shortly after the ganglion into three branches: Ophthalmic, Maxillary, and Mandibular divisions
Nociceptive (Aδ and C fiber) inputs cross to the spinothalamic (now trigeminothalamic) tract and ascend via the medulla and pons to ventroposterior nuclei of the brainstem and onwards to the cortex

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Description

This quiz covers the different types of pain, including cutaneous, somatic, and visceral pain, and the neural pathways involved in pain transmission from the periphery to the cortex.