Trigeminal System Flashcards by Kevan Green

What is chemesthesis?

The ability to detect chemical stimuli

Ex. Blister in salt water burns

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What is stereognosis?

The ability to sense size, texture, viscosity, hardness of 3D objects

Mouth feel

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T/F: Flavor is related solely to taste sensation.

FALSE

Taste and olfaction (special senses)

Texture, temperature, chemesthesis (CN V)

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Which branch of CN V has motor function?

Mandibular

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What are the two other names for the trigeminal ganglion?

Gasserian and Semilunar

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What nucleus has a separate ganglion and is key in reflexes?

Mesencephalic nucleus

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After sensory fibers get to the mesencephalic nucleus where do they go?

Trigeminal motor nucleus

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What are the two major destinations of sensory fibers after going through the trigeminal ganglion?

Principal (main or chief) sensory nucleus: light touch

2. Spinal trigeminal nucleus (three subdivisions)

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What are the three subdivisions of the spinal trigeminal nucleus?

Oralis: light touch
Interpolaris: temperature
Caudalis (medullary dorsal horn): oral pain

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After exiting the principal sensory nucleus and the spinal trigeminal nucleus where do fibers then go?

Ventral posterior medial nucleus of thalamus

VPM nucleus

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T/F: The face is represented on the most medial part of the cortex.

FALSE

Lateral

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What is the largest sensory fiber associated with CN V?

A-beta

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A-beta fibers have a low threshold for activation. What can this tell you about their function?

Do NOT sense pain.

Touch and proprioception

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Which CN V sensory fibers have the fastest conduction?

A-beta

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T/F: Conduction speed is directly related to fiber diameter.

TRUE

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What is the function of A-delta fibers?

Very ambiguous: touch, temp., chemesthesis, pain (sharp)

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T/F: C-fibers are not myelinated.

TRUE

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Which fiber would give a dull and burning pain sensation?

C-fibers

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How can sensory fibers be classified?

Receptive field size: I = small; II = large

2. Adaptation: SA = slow and static; RA = rapid and not static

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What are the two types of fibers found at the superficial level of the hand?

Meissner corpuscle: spatial discrimination (RA I)

Merkel disk: pressure (SA I)

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What are the two fibers found in the deep skin of the hand?

Pacinian corpuscle: vibration (RA II)

Ruffini ending: skin stretch (SAII)

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Which receptors of the hand are encapsulated? What do they have in common functionally?

Meissner corpuscle and pacinian corpuscle

Rapid response

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The ___________ composed of cells and _________ fibers provide a cushion to applied stimulus in a pacinian corpuscle.

Lamellae; collagen

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What are three mechanisms of mechanotransduction?

ENaC
TRP channels
Piezo 1 and Piezo 2

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What form of mechanotransduction is involved with merkel cell activation?

Piezo 2

What four factors influence mechanoreceptors?

1. Size & myelination 2. Superficial or deep receptor 3. Structure of ending (encapsulation) 4. Transduction method (TRP, Piezo, ENacS)

T/F: A threshold is a definite point of stimulus that will result in an AP and detection.

FALSE It is NOT absolute/definite but rather a probability

What is a von frey Hair?

Measures nerve sensitivity

What parts of the face have similar thresholds for sensitivity as the fingertips?

Lips and perioral structures

What is microneurography?

A tool to record human nerves, map receptive fields, and determine neuron properties.

What major branch is the infraorbital branch of CN V associated with?

Maxillary nerve

What types of receptors are found on the infraorbital nerve?

SAI, SAII, and RAI

________ corpuscles are missing from the infraorbital nerve. This means our ability to sense __________ in the side of the face is poor.

Pacinian; vibration

The lingual nerve is a branch of the _________ branch of CN V and provides innervation for the _______.

Mandibular; tongue

T/F: The tip of the tongue is less sensitive than the dorsal portion of the tongue.

FALSE! Tip of tongue is more sensitive than fingertip!

Krause end bulbs are found in which oral structure? Are they encapsulated?

Tongue; no

T/F: Both SA and RA receptors are found on the tongue.

TRUE

Krause end bulbs are similar in structure to a _______ corpuscle.

Meissner

You notice a patient is constantly reaching up and touching their lip/chin after a recent third molar extraction. What might be the issue here?

Damage to the lingual or mental nerve during extraction -> mechanoreceptor malfunction but no pain

Along with the NT glutamate, what else can merkel cells release?

Neuropeptides and growth factors

T/F: Merkel cells are found in regions with high masticatory load.

TRUE

What could be a secondary function of Merkel cells?

Promote cell division and regeneration in areas of mechanical stress

What nerve innervates the TMJ?

Auriculotemporal nerve (Mandibular Nerve branch)

The auriculotemporal nerve approaches the TMJ from which location?

Posterior and moves toward lateral

What two smaller nerves help innervate the anterior TMJ?

Masseter nerve and Posterior deep temporal nerve

T/F: The TMJ has less innervation on the medial and anterior portions of the joint.

TRUE

Other than C-fibers, what is the majority of nerve endings found in the TMJ?

Ruffini endings

T/F: The superior alveolar nerve is a branch of the mandibular branch of CN V.

FALSE Maxillary branch

T/F: The anterior teeth are more sensitive than the posterior teeth.

TRUE

What types of receptors are found in the PDL?

1. Complex Ruffini endings 2. Simple Ruffini endings 3. Free nerve endings (C-fibers)

Fibers at the PDL near the apex of the tooth are innervated by which nuclei?

Mesencephalic nucleus

Sensory fibers in the PDL are most sensitive to forces in which direction?

Labial and distal

T/F: PDL Ruffini endings are slowly adapting and directionally sensitive.

TRUE

T/F: Denture and implant patients have trouble with sensory feedback but little trouble with motor function.

TRUE Likely due to lack of PDL sensory fibers

T/F: Studies have shown that both the PDL and TMJ sensory fibers play a role in interdentinal stereognosis.

TRUE

Fibers in the reflex pathway for the PDL would have what path?

PDL at Apex of tooth -> mesencephalic nucleus (and ganglion) -> Salivatory and motor nuclei

What would be the pathway for fibers from the PDL that do not contribute to a reflex?

1. PDL (not at apex) -> trigeminal ganglion -> principal nucleus -> VPM 2. PDL (not apex) -> trigeminal ganglion -> nucleus oralis -> trig. Motor nucleus -> anterior digastric m.

What is the difference between thresholds and super thresholds?

Thresholds = off or on Super = varying intensities

T/F: Facial region is more sensitive to warm stimuli than intraoral.

TRUE

What type of transduction is used for thermal transduction?

TRP channels

Which TRP receptor will be the first to indicate thermal pain?

TRPV1