All of the following descending tracts decussate EXCEPT:

Correct Answer: D

Rationale: Vestibulospinal . The vestibulospinal tract descends ipsilaterally from the vestibular nuclei to coordinate posture and balance, aiding antigravity musclwithout crossing. Choice A, Lateral corticospinal, crossin the medulla for contralateral voluntary movement. Choice B, Rubrospinal, decussatin the midbrain to influence flexor tone. Choice C, Tectospinal, crossin the midbrain for visual reflexes. Unlike these, vestibulospinal remains uncrossed, impacting ipsilateral extensors (e.g., standing stability). Thus, D is the non-decussating exception.

Correct Answer: C

Rationale: Damage to corticospinal tract above the level of decussation results in ipsilateral paralysis . This is incorrect: above decussation, damage causcontralateral paralysis. Choice A is wrong (right hemisection is right deficit). Choice B is false (ventral horn). Choice D is incorrect (below is ipsilateral). Assuming intent, C should be contralateral possible error.

Correct Answer: D

Rationale: Under involuntary control only , which is false. The swallowing center is in the medulla oblongata (A is true), coordinating the reflex via the nucleus ambiguus and vagus nerve. Swallowing is initiated voluntarily (B is true) in the oral phase (cortex, tongue), then becominvoluntary in pharyngeal and esophageal phases. It involvcranial nerv5 (trigeminal, mastication), 7 (facial, lips), 9 (glossopharyngeal, sensation), and 10 (vagus, motility) (C is true), orchestrating the process. Choice D is incorrect; while the reflex phase is involuntary, the initial act is voluntary, distinguishing it from fully reflex actions like vomiting. Stroke affecting cortical input or medullary centers shows this dual control, making D the exception and the correct answer.

Correct Answer: D

Rationale: The swallowing center is located in the cerebellum , which is not true. The swallowing center is in the medulla oblongata (A is true), specifically the nucleus ambiguus and dorsal motor nucleus, coordinating the reflex phase via cranial nerv9 and 10. Choice B is true; swallowing begins voluntarily in the oral phase (cortex-driven tongue movement) before becoming reflexive. Choice C is correct; the reflex involvcranial nerve 5 (trigeminal, mastication/sensation), 9 (glossopharyngeal, pharyngeal sensation), and 10 (vagus, pharyngeal/esophageal motility), with 7 also contributing (lips). Choice D is false; the cerebellum coordinatmovement but not swallowing, which relion medullary control. Damage to the medulla (e.g., stroke) causdysphagia, unlike cerebellar lesions affecting gait. Thus, D is the untrue statement, making it the correct answer.

Correct Answer: C

Rationale: It is under voluntary control , which is false. The vomiting center is in the medulla oblongata (A is true), coordinating the reflex near the area postrema. Choice B is correct; it receivvestibular input via cranial nerve 8 (e.g., motion sickness), triggering vomiting. Choice C is inaccurate; vomiting is an involuntary reflex, not voluntarily initiated, unlike swallowings oral phase. Choice D is true; cranial nerv8 (vestibular), 9 (glossopharyngeal, sensation), and 10 (vagus, motility) mediate the reflex arc. Brainstem damage abolishvomiting, while cortical lesions do not, confirming its involuntary nature. Thus, C is the exception, making it the correct answer.