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What are the learning outcomes described for students by the end of the lecture?
Describe the glossopharyngeal nerve nuclei location, course, type of fibers it carries, areas it supplies and effect of lesion; Describe the vagus nerve nuclei location, course, type of fibers it carries, areas it supplies and effect of lesion; Describe the spinal accessory nerve nuclei location, course, type of fibers it carries, areas it supplies and effect of lesion; Describe the hypoglossal nerve nuclei location, course, type of fibers it carries, areas it supplies and effect of lesion.
Which of the following areas are supplied by the glossopharyngeal nerve? (Select all that apply)
The glossopharyngeal nerve carries special senses (taste) information from the posterior 1/3 of the tongue.
True
What is the effect of a lesion in the vagus nerve?
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The (blank) nerve innervates the sternocleidomastoid and trapezius muscles.
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Match the effects of lesions with the corresponding cranial nerves:
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Study Notes
The Last Four Cranial Nerves
Glossopharyngeal Nerve (CN IX)
- Located in the medulla oblongata, between the pyramid and olive
- Rootlets leave the medulla through the groove between the olive and inferior cerebellar peduncle
- Nuclei:
- Nucleus Ambiguus: somatomotor fibers for stylopharyngeus muscle
- Inferior Salivary Nucleus: visceromotor fibers for parotid gland
- Nucleus solitarius: taste fibers from posterior third of tongue, carotid body, and carotid sinus
- Spinal trigeminal nucleus: general sensory from posterior third of tongue, pharynx, middle ear, auditory tube, and mastoid air cells
- Peripheral processes carry:
- Special sense (taste) and somatosensory information from posterior 1/3 of tongue
- Somatosensory information from oro-pharynx, middle ear, auditory tube, and mastoid air cells
- General viscerosensory information from carotid body and carotid sinus
- Effects of lesions:
- Absent gag reflex
- Reduction in salivation due to damaged CN IX
Vagus Nerve (CN X)
- Located in the medulla oblongata, between the olive and inferior cerebellar peduncle
- Contains somatomotor, visceromotor, and somatosensory components
- Nuclei:
- Nucleus Ambiguus: somatomotor innervation of skeletal muscles of larynx, pharynx, and soft palate
- Dorsal Motor Nucleus of the Vagus: parasympathetic innervation of smooth muscle of digestive system, respiratory system, and heart
- Inferior Ganglion of the vagus nerve (nodose ganglion): innervation of mucosa of larynx, respiratory system, heart, and digestive system
- Superior Ganglion: innervation of external auditory meatus, meninges of the posterior cranial fossa, and external surface of tympanic membrane
- Effects of lesions:
- Hyperactivity of vagus leading to stomach ulcers, disruption of swallowing, vomiting, and cough reflex
- Disruption or loss of carotid sinus reflex
- Disruption of normal respiratory functions, loss of taste sensation from root of the tongue
- Probable loss of somatosensory sensation from skin of external ear, tympanic membrane, and root of the tongue
Spinal Accessory Nerve (CN XI)
- Located in C1-C5 of the spinal cord, in the posterior portion of the anterior horn
- Fibers leave the spinal cord between the posterior and anterior roots, enter the cranial cavity through the foramen magnum, and exit through the jugular foramen
- Innervates the sternocleidomastoid and trapezius muscles
- Effects of lesions:
- Shoulder pain in neck and upper back due to straining of supporting muscles
- Limited or loss of sustained abduction of the shoulder
Hypoglossal Nerve (CN XII)
- Located in the hypoglossal nucleus, in the brainstem
- Exits the cranial cavity through the hypoglossal canal of the occipital bone
- Loops around the occipital artery to enter the lateral side of the tongue
- Innervates intrinsic and extrinsic muscles of the tongue (hyoglossus, styloglossus, and genioglossus)
- Effects of lesions:
- Unilateral hypoglossal nerve damage: tongue deviates to the side of the lesion on protrusion
- Supranuclear lesion: tongue deviates to the opposite side of the lesion
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