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Chapter 1: Nervous System

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A male patient is admitted to the hospital complaining of severe headaches. During the neurological examination, his tongue deviates to the left upon protrusion. A CT scan reveals a tumor affecting a cranial nerve. Which nerve if affected?

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A. Glossopharyngeal (CN IX)

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B. Hypoglossal (CN XII)

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C. Mandibular (CN V3)

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D. Maxillary (CN V2)

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E. Vagus (CN X)

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Answer B. The hypoglossal nerve supplies all intrinsic and most extrinsic muscles of the tongue. Bilateral contraction of the genioglossus (an extrinsic tongue muscle) results in protrusion of the tongue in the midline. Unilateral palsy of the hypoglossal nerve will cause the tongue to deviate from the midline and toward the affected side.

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A female patient is unable to close her left eye tightly. Which nerve is most likely affected?

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A. Facial (CN VII)

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B. Maxillary (CN V2)

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C. Oculomotor (CN III)

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D. Ophthalmic (CN V1)

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E. Trochlear (CN IV)

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Answer A. The facial nerve supplies the muscles of facial expression. Therefore, damage to this nerve results in weakness of facial muscles on the affected side. The orbicularis oculi (a muscle of facial expression) is located in the eyelids and around the orbit. Contraction of this muscle is responsible for closing the lids tightly.

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During surgery to repair the gastro-esophageal junction, the surgeon damaged the vagal trunks. Which part of the large bowel would be affected in this patient?

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A. Ascending colon

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B. Descending colon

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C. Left colic flexure

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D. Sigmoid colon

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E. All of the above

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Answer A. The anterior and posterior vagal trunks derived from the vagus nerves enter the abdomen through the esophageal hiatus of the diaphragm. These nerves carry the preganglionic parasympathetic component for abdominal organs that are supplied by the celiac trunk and the superior mesenteric artery. Postganglionic parasympathetic axons arise from terminal ganglia located near or in these organs. The ascending colon is supplied by the superior mesenteric artery and, therefore, would lose its parasympathetic innervation if the vagal trunks are damaged.

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Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that specifically targets motor neurons that control skeletal ...

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