Which of the following tracts has descending autonomic fiber providing a pathway by which the hypothalamus can control the sympathetic sacral parasympathetic outflow:

Correct Answer: D

Rationale: Reticulospinal tracts. The reticulospinal tracts from the brainstem, influenced by the hypothalamus, regulate autonomic functions like sympathetic (T1-L2) and sacral parasympathetic (S2-S4) outflow. Choice A (rubrospinal) is motor tone. Choice B (tectospinal) is head reflexes. Choice C (vestibulospinal) is posture. Thus, D correctly identifithe autonomic pathway, making it correct.

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: A

Rationale: Tracts 1 and 2 originate from the precentral gyrus of the frontal lobe . The lateral corticospinal tract and anterior corticospinal tract are pyramidal tracts arising from the primary motor cortex in the precentral gyrus, controlling voluntary movements. Choice B is incorrect; rubrospinal originatfrom the red nucleus (midbrain), and tectospinal from the superior colliculus (midbrain), not cerebellum. Choice C is wrong; lateral corticospinal tract crossin the medullary pyramids, not midbrain. Choice D is false; anterior corticospinal tract remains ipsilateral until synapsing in the spinal cord, with some fibers crossing locally. Thus, A correctly identifithe origin of corticospinal tracts 1 and 2, making it the right answer.

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.