Cranial Nerve X (Vagus Nerve)

Origin

• The vagus nerve emerges from the lateral aspect of the medulla oblongata and traverses the jugular foramen, where the superior and inferior sensory ganglia are located.

• Rootlets arise from the postolivary sulcus, between the olive and inferior cerebellar peduncle.

  Brainstem Origin

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Course

1. Intracranial: Exits the skull via the jugular foramen (along with CN IX and XI).

   • At the jugular foramen it has two sensory ganglia:

     • Superior (jugular) ganglion – small, general somatic sensation.

     • Inferior (nodose) ganglion – large, visceral sensation.

2. Cervical course: Descends in the carotid sheath with the internal jugular vein and internal carotid/common carotid artery.

3. Thoracic course: Enters the thorax, contributes to the cardiac, pulmonary, and esophageal plexuses.

4. Abdominal course: Forms the anterior and posterior vagal trunks around the esophagus and enters the abdomen, supplying abdominal viscera up to the proximal two-thirds of the transverse colon.

Branches

• Auricular branch (Arnold’s nerve) – external ear sensation.

• Pharyngeal branches – pharyngeal plexus, most pharyngeal muscles.

• Superior laryngeal nerve → external branch (cricothyroid motor) & internal branch (laryngeal mucosa sensation).

• Cardiac branches – cardiac plexus.

• Recurrent laryngeal nerves – motor to laryngeal muscles (except cricothyroid), sensation below vocal cords.

  • Right recurrent loops around subclavian artery.

  • Left recurrent loops around aortic arch.

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Functional Components (Modalities)

Vagus nerve is mixed (sensory, motor, parasympathetic):

1. Branchial Motor (Special Visceral Efferent)

   • Muscles of the pharynx (except stylopharyngeus, CN IX)

   • Muscles of the larynx (except cricothyroid, external SLN)

   • Muscles of soft palate (except tensor veli palatini, CN V3)

2. Visceral Motor (Parasympathetic, General Visceral Efferent)

   • Smooth muscle and glands of pharynx, larynx, thoracic and abdominal viscera to proximal transverse colon.

   • Cardiac inhibitory fibers (slows heart rate).

3. Visceral Sensory (General Visceral Afferent)

   • Sensation from larynx, pharynx, trachea, thoracic and abdominal viscera, aortic arch chemoreceptors and baroreceptors.

4. General Sensory (General Somatic Afferent)

   • Sensation from external ear, external auditory canal, part of tympanic membrane, posterior meninges.

5. Special Sensory (Special Visceral Afferent)

   • Taste sensation from epiglottis and root of the tongue.

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Physiology / Functions

 

• Swallowing and speech: Via motor innervation to pharyngeal and laryngeal muscles.

• Parasympathetic control:

  • Slows heart rate, reduces atrial contractility.

  • Stimulates peristalsis and glandular secretion in GI tract.

  • Controls bronchoconstriction and secretion in airways.

• Reflexes:

  • Gag reflex (afferent limb CN IX, efferent limb CN X).

  • Carotid sinus and aortic arch baroreceptor reflexes.

• Sensation: Provides afferent input from thoracic/abdominal viscera, pharynx, and larynx.

• Taste: From epiglottis region.

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✅ Clinical correlations

• Lesion → hoarseness, dysphagia, loss of gag reflex, uvula deviates to contralateral side.

• Vagal overactivity → bradycardia, fainting.

• Testing: Observe palate elevation, gag reflex, voice quality.

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CN X Modalities

The vagus nerve exits the medulla oblongata and travels with CNN IX and XI into the jugular foramen. CN X consists primarily of the following four modalities:

• Visceral sensory neurons. Provide visceral sensory information from the larynx (below the vocal folds), trachea, and esophagus, and the thoracic and abdominal viscera as well as the stretch receptors of the aortic arch and the chemoreceptors of the aortic and carotid bodies (Figure 17-7A and B).
• General sensory neurons. Provide general sensory information from part of the external acoustic meatus, the pinna, and the laryngopharynx (Figure 17-7A).
• Branchial motor neurons. Supply the palatoglossus, laryngeal, and pharyngeal muscles (except for the stylopharyngeus muscle, which is supplied by CN IX) and the palatal muscles (except for the tensor veli palatini, which is supplied by CN V-3) (Figure 17-7A).
• Visceral motor neurons. Provide parasympathetic innervation to the smooth muscle and the glands of the respiratory system and gastrointestinal tract to the transverse colon (Figure 17-7B). In general, CN X increases secretion from glands and smooth muscle contraction. CN X slows the heart rate, stimulates bronchiolar secretions, bronchoconstriction, and peristalsis, and increases secretions.