L30. Neuroscience: Trigeminal Pathways

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Questions and Answers

Which of the following is NOT a sensory modality of the trigeminal nerve?

  • Pain
  • Temperature
  • Light Touch
  • Taste (correct)

Which of the following muscles is NOT innervated by the motor division of the trigeminal nerve?

  • Lateral rectus (correct)
  • Tensor veli palatini
  • Anterior belly of digastric
  • Tensor tympani

Which of the following statements about the trigeminal nerve is TRUE?

  • It connects to the brainstem at the midbrain.
  • It has both sensory and motor fibers. (correct)
  • It has only motor fibers.
  • It is the smallest cranial nerve.

Which of the following is NOT a function of the trigeminal nerve?

<p>Control of facial expression (C)</p> Signup and view all the answers

What is the clinical significance of the corneal reflex?

<p>It is a test of the function of the trigeminal nerve. (C)</p> Signup and view all the answers

Which of the following accurately describes the trigeminal complex?

<p>It is a group of four nuclei in the brainstem that mediate trigeminal nerve function. (A)</p> Signup and view all the answers

Which of the following is NOT a clinical correlation regarding the trigeminal complex?

<p>Bell's palsy (C)</p> Signup and view all the answers

Which of the following statements accurately describes the role of the superior cerebellar peduncle in mastication?

<p>It receives proprioceptive information from the jaw muscles and relays it to the cerebellum. (A)</p> Signup and view all the answers

Based on the text, which of the following is NOT directly involved in the regulation of chewing?

<p>Hypothalamus (B)</p> Signup and view all the answers

What is the primary function of the mesencephalic nucleus of V in the jaw-jerk reflex?

<p>It processes proprioceptive information from the jaw muscles. (C)</p> Signup and view all the answers

Which muscle is responsible for closing the mouth?

<p>Masseter (D)</p> Signup and view all the answers

Which of these cranial nerves does NOT contribute to the sensory innervation of the auricle?

<p>Hypoglossal (XII) (C)</p> Signup and view all the answers

What is hyperacusis?

<p>An increased sensitivity to sound (A)</p> Signup and view all the answers

Which of the following structures is NOT innervated by the ophthalmic division (V1) of the trigeminal nerve?

<p>Lower eyelid (B)</p> Signup and view all the answers

Which of the following muscles is responsible for moving the jaw side to side?

<p>Lateral pterygoid (D)</p> Signup and view all the answers

What is the afferent limb of the jaw-jerk reflex?

<p>The sensory neurons of the trigeminal nerve (B)</p> Signup and view all the answers

A patient presents with a loss of sensation to the forehead, upper eyelid, and cornea. Which division of the trigeminal nerve is most likely affected?

<p>Ophthalmic (V1) (A)</p> Signup and view all the answers

What is the main purpose of the jaw-jerk reflex?

<p>To maintain jaw muscle tone and adjust it during chewing (D)</p> Signup and view all the answers

The maxillary division (V2) of the trigeminal nerve passes through which foramen?

<p>Foramen rotundum (A)</p> Signup and view all the answers

How does the cerebellum contribute to chewing?

<p>It coordinates and refines the chewing movements. (A)</p> Signup and view all the answers

Which of the following statements accurately describes the sensory innervation of the tongue?

<p>The anterior two-thirds of the tongue is innervated by the mandibular division (V3), and the posterior one-third is innervated by the glossopharyngeal nerve (IX). (B)</p> Signup and view all the answers

What is the function of the tensor tympani muscle?

<p>It is involved in hearing and sound transmission. (C)</p> Signup and view all the answers

A patient presents with pain in the lower jaw and difficulty chewing. Which division of the trigeminal nerve is most likely affected?

<p>Mandibular (V3) (D)</p> Signup and view all the answers

Which of the following structures is involved in relaying sensory signals from the trigeminal nerve to the thalamus?

<p>Pons (A)</p> Signup and view all the answers

Which of the following statements accurately describes the sensory innervation of the dura mater?

<p>The dura mater is innervated by branches of all three divisions of the trigeminal nerve (V1, V2, and V3) and the vagus nerve (X). (B)</p> Signup and view all the answers

Which of the following statements accurately describes the direct response in the corneal reflex?

<p>The closing of the ipsilateral eye due to stimulation of the ipsilateral cornea. (B)</p> Signup and view all the answers

What is the primary anatomical location of the first-order sensory neurons involved in the jaw jerk reflex?

<p>Mesencephalic nucleus (A)</p> Signup and view all the answers

Identify the correct sequence of neurons involved in the efferent limb of the corneal reflex.

<p>2nd order neurons in spinal V -&gt; Facial motor nucleus neurons -&gt; orbicularis oculi muscles (A)</p> Signup and view all the answers

Based on the information provided, trigeminal neuralgia is primarily associated with which of the following?

<p>Compression of the trigeminal nerve by aberrant vessels (B)</p> Signup and view all the answers

In contrast to the jaw jerk reflex, the corneal reflex differs in being:

<p>A disynaptic reflex with bilateral innervation (B)</p> Signup and view all the answers

Which of the following structures receives projections from the mesencephalic nucleus of V?

<p>Chief sensory nucleus of V (A), Cerebellum (B), Trigeminal motor nucleus (D)</p> Signup and view all the answers

Which of the following statements correctly describes the origin and projection of the dorsal trigeminothalamic tract (DTTT)?

<p>Originates in the chief sensory nucleus of V and projects ipsilaterally to the VPM. (C)</p> Signup and view all the answers

The sensory pathway for proprioception differs from the other sensory pathways for pain, temperature, and discriminative touch in that it involves:

<p>A different 1st order neuron nucleus. (C)</p> Signup and view all the answers

Which of the following muscles is NOT innervated by the trigeminal motor nucleus?

<p>Trapezius (A)</p> Signup and view all the answers

The ventral trigeminothalamic tract (VTTT) carries information about:

<p>Pain, temperature, and light touch. (A)</p> Signup and view all the answers

What is the name of the structure that carries the trigeminal motor axons to the muscles of mastication?

<p>Portio minor (B)</p> Signup and view all the answers

Which of the following statements is TRUE regarding the corticobulbar fibers that project to the trigeminal motor nucleus?

<p>They are bilateral. (D)</p> Signup and view all the answers

The sensory pathway for pain, temperature, and light touch is distinguished from the other sensory pathways of the trigeminal nerve by the following:

<p>It uses the spinal nucleus of V as the 2nd order neuron nucleus. (C)</p> Signup and view all the answers

Which of the following structures receives input from the trigeminal ganglion?

<p>The chief sensory nucleus of V. (C)</p> Signup and view all the answers

Which of the following correctly identifies the sensory pathway for vibration?

<p>V1, V2, V3 -&gt; Trigeminal ganglion -&gt; Chief sensory nucleus of V -&gt; VTTT -&gt; VPM -&gt; Postcentral gyrus (A)</p> Signup and view all the answers

Flashcards

Trigeminal Nerve

Largest cranial nerve, connects to the brainstem at pons; contains sensory and motor fibers.

Sensory Modalities

Sensory functions of the trigeminal nerve include pain, temperature, touch, vibration and proprioception.

Motor Fibers of Trigeminal

Supply muscles for chewing (mastication) and some ear muscles.

Trigeminal Nuclei

Four nuclei located in the brainstem associated with the trigeminal nerve.

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Cranial Nerve V

Also known as the trigeminal nerve, it has sensory and motor functions.

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Dermatomes of V

Regions of the head and neck innervated by the three divisions of the trigeminal nerve.

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Trigeminal Reflexes

Involuntary responses, like the jaw-jerk and corneal reflex, involving the trigeminal nerve.

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Ophthalmic Nerve (V1)

Innervates forehead, upper eyelid, cornea, and sinuses; passes through superior orbital fissure.

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Maxillary Nerve (V2)

Innervates upper lip, cheek, lower eyelid, and sinuses; passes through foramen rotundum.

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Mandibular Nerve (V3)

Contains sensory and motor fibers; innervates lower lip, chin, and anterior tongue; passes through foramen ovale.

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Dura Mater Innervation

Supplied by trigeminal branches V1, V2, V3, vagus nerve (X), and cervical nerves (C1-C3).

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Superior Orbital Fissure

An opening for the ophthalmic nerve (V1) to pass into the orbit.

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Foramen Rotundum

Opening allowing the maxillary nerve (V2) to exit the skull.

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Foramen Ovale

Opening for the mandibular nerve (V3) to exit the skull; also carries motor fibers.

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Ascending Trigeminothalamic Tracts

Pathways that carry sensory signals from trigeminal nerve through brainstem.

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Afferent Limb of Jaw Jerk Reflex

The afferent limb consists of sensory (V3) input affecting the reflex action.

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Efferent Limb of Jaw Jerk Reflex

The motor root accompanying V3 that triggers muscle contraction of the jaw.

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Corneal Reflex

A reflex causing both eyes to close when one cornea is stimulated; features direct and consensual responses.

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Afferent Limb of Corneal Reflex

The afferent limb involves the ophthalmic nerve (V1) providing sensory input for the reflex.

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Causes of Trigeminal Neuralgia

Severe pain due to irritation or compression of the trigeminal nerve by vessels; triggered by light stimuli.

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Oral motor system

System requiring feedback during mastication and chewing.

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Mastication

Process of chewing food, altering texture and demands.

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Jaw-jerk reflex

Reflex that adjusts muscle tone during chewing.

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Proprioception in chewing

Sense of body position during mastication.

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Cerebellum in chewing

Brain region regulating the coordination of mastication.

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Tensor tympani

Inner ear muscle affecting hearing, can induce hyperacusis.

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Muscles of mastication

Muscles involved in moving the jaw for chewing.

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Jaw closing muscles

Muscles that help close the mouth during mastication.

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Jaw reflex afferent limb

Sensation traveling via stretch receptors during the jaw jerk reflex.

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Sensory pathway for pain

Pathway involving pain, temperature, and light touch perception via V1, V2, V3.

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1st order neuron

First neuron in the sensory pathway, located in the trigeminal ganglion.

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2nd order neuron

Neuron located in the spinal nucleus of V, transmitting signals to VTTT.

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Ventral trigeminothalamic tract (VTTT)

Contralateral projection pathway from the 2nd to the 3rd order neuron.

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3rd order neuron

Neuron located in the VPM nucleus of thalamus, leading to postcentral gyrus.

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Sensory pathway for discriminative touch

Pathway for discriminative tactile and vibration sensations via V1, V2, V3.

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Dorsal trigeminothalamic tract (DTTT)

Ipsilateral projection pathway associated with discriminative touch.

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Proprioception

Sense of body position maintained by muscle spindles and joint receptors.

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Trigeminal motor nucleus

Nucleus for motor function located in the mid pons, innervating mastication muscles.

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Study Notes

Trigeminal Complex (L30)

  • The trigeminal nerve has sensory and motor divisions.
  • It's the largest cranial nerve, connecting to the brainstem at the pons.
  • Sensory components include pain, temperature, light touch, discriminative touch, vibration, conscious and unconscious proprioception
  • Motor components innervate the muscles of mastication, tensor tympani, tensor veli palatini, and anterior belly of digastric.

Sensory Divisions of CN V

  • Ophthalmic (V1): Sensory area for forehead, upper eyelid, cornea, orbit, anterior aspect of nose, and nasal sinuses. Nerve exits via the superior orbital fissure.
  • Maxillary (V2): Sensory area for upper lip, cheek, lower eyelid, parts of nose, temple, and mucous membranes of the upper mouth, nose, teeth, and gums. Nerve exits via the foramen rotundum.
  • Mandibular (V3): Sensory area for lower lip, chin, posterior portions of the cheek and temple, external ear, and mucous membranes of the lower jaw, floor of the mouth, tongue, and temporomandibular joint. Includes motor fibers. Nerve exits via the foramen ovale.

Trigeminal Pathways

  • The sensory pathways for pain, temperature, light touch, and two-point discrimination (identifying two distinct points)
  • The sensory pathways for discriminative touch and vibration: The primary pathways are the trigeminothalamic tracts, which carry information to the thalamus. The thalamus then sends the information to the cortex.
  • Sensory pathway for proprioception: Information from muscle spindles and joint receptors travel along the trigeminal pathways to the mesencephalic nucleus: This nucleus plays a critical role in the jaw jerk reflex.

Trigeminal Motor Nucleus and Pathways

  • The motor nucleus of V is located in the mid-pons.
  • It receives inputs from corticobulbar fibers (bilateral) and the mesencephalic nucleus.
  • Motor root of V exits the skull via foramen ovale, and is called “Portio minor”.
  • Trigeminal motor neurons innervate muscles of mastication (e.g., temporalis, masseter, medial and lateral pterygoids), tensor tympani, tensor veli palatini, and anterior belly of digastric muscle.
  • The oral motor system requires continual feedback during mastication for proper jaw muscle tension.
  • The tensor tympani is an inner ear muscle, and abnormal spasm can lead to hyperacusis or tinnitus.

Trigeminal Reflexes

  • Jaw Jerk Reflex: A monosynaptic reflex elicited by tapping the chin. The afferent limb is from stretch receptors in the jaw muscles. The efferent limb is from the motor neurons of the trigeminal nucleus.
  • Corneal Reflex: A disynaptic and consensual reflex. Stimulation of the cornea causes closure of both eyes. The afferent limb is the ophthalmic nerve (V1). The efferent limb involves neurons in the facial motor nucleus that innervate the orbicularis oculi muscle which closes the eye

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