Numbered below are various descending motor tracts: 1. Lateral cortico spinal tract, 2. Rubrospinal tract, 3. Vestibulospinal tract, 4. Medullary reticulospinal tract. Choose the correct statement:

Correct Answer: A

Rationale: 1 and 2 cross the midline in the brain stem . Lateral corticospinal crossin the medulla (brainstem), and rubrospinal crossin the midbrain (brainstem). Choice B is wrong (rubrospinal from red nucleus, not superior colliculus). Choice C is incorrect (vestibulospinal yes, medullary no). Choice D is false (medullary is lateral). Thus, A is correct.

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: In corticospinal tract hemisection of the right half of the spinal cord in the cervical region result in motor deficit in the left side of the body . This reflects intent but requirclarification: corticospinal fibers decussate in the medulla, so a right cervical hemisection below decussation affects right (ipsilateral) motor function. Above decussation, damage causcontralateral loss (making A wrong). Choice B is false (below is ipsilateral). Choice D is incorrect (ventral horn). Assuming a higher lesion intent, C aligns with contralateral logic if misworded.

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.