True about corticospinal tract:

Correct Answer: D

Rationale: fibers terminate on the motor neurons in the ventral horn . The corticospinal tract originatfrom the motor cortex (precentral gyrus, not just premotor, making C incorrect), descends through the brainstem, and decussatin the lower medulla (not pons, making A wrong). Most fibers, especially lateral corticospinal, supply distal muscl(e.g., hands) for fine movement, not proximal (making B incorrect). These fibers synapse on alpha motor neurons in the ventral horn of the spinal cord, directly or via interneurons, to control voluntary movement, making D accurate. For example, corticospinal damage disrupts skilled tasks like writing, reflecting ventral horn innervation. Thus, D is the true statement about the corticospinal tract.

Correct Answer: C

Rationale: Fibers of corticospinal tract pass through the anterior limb of the internal capsule . Corticospinal fibers pass through the posterior limb (D is correct), not anterior (frontopontine fibers). Choice A is true (synapson alpha motor neurons). Choice B is accurate (above decussation causcontralateral paralysis). Thus, C mislocatthe fibers, making it the wrong statement.

Correct Answer: C

Rationale: Fibers of corticospinal tract pass through the anterior limb of the internal capsule . Corticospinal fibers pass through the posterior limb (D is correct), not anterior (frontopontine fibers). Choice A is true (synapson alpha motor neurons). Choice B is accurate (above decussation causcontralateral paralysis). Thus, C mislocatthe fibers, making it the wrong statement.

Correct Answer: D

Rationale: Located in the medulla oblongata . The vomiting center is in the medulla oblongata, near the area postrema (not hypothalamus, making A wrong, which regulatnausea indirectly). Vomiting is an involuntary reflex (B is false), unlike swallowing, triggered by medullary integration of signals. It receivinput from gastric stretch receptors via the vagus nerve (cranial nerve 10) (C is wrong), responding to distension (e.g., overeating). D is true; the medulla coordinatvomiting via cranial nerv9 (sensation), 10 (motility), and 8 (vestibular), with the chemoreceptor zone detecting emetics. Lesions here abolish vomiting, as in brainstem stroke, unlike hypothalamic effects. Thus, D is the true statement.

Correct Answer: B

Rationale: It is initiated involuntarily , which is false. The swallowing reflex involvcranial nerv5 (trigeminal, mastication), 7 (facial, lips/tongue), 9 (glossopharyngeal, sensation), and 10 (vagus, motility) (A is true), coordinating oral, pharyngeal, and esophageal phases. Choice B is incorrect; swallowing starts voluntarily (cortex initiatbolus movement), then shifts to an involuntary reflex controlled by the medulla. Choice C is true; peristalsis in the esophagus (primary and secondary waves) movthe bolus, driven by the vagus and enteric nervous system. Choice D is accurate; the swallowing center in the medulla oblongata (nucleus ambiguus) orchestratthe reflex. For example, cortical strokimpair voluntary initiation, while medullary damage disrupts the reflex, showing dual control. Thus, B is the exception, making it the correct answer.