This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Vomiting centre is situated in which part of brain? \nSelect and explain. \nA. Hypothalamus, B. Amygdala, C. Pons, D. Medulla', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The area postrema (AP) has been implicated as a chemoreceptor trigger zone for vomiting (emesis) for\xa0over 40 years. The AP is located on the dorsal surface of the medulla oblongata at the caudal end of\xa0the fourth ventricle. It is one of the so-called circumventricular organs that serve as an interface between the brain parenchyma and the cerebrospinal ﬂuid (CSF)-\xa0containing ventricles. The AP lacks a speciﬁc blood-brain diﬀusion barrier to large polar molecules\xa0 (i.e., a “blood-brain barrier”) and is thus anatomically positioned to detect emetic toxins in the blood\xa0 as well as in the CSF.\xa0\nThe NTS (nucleus of the solitary tract) may serve as the beginning of a ﬁnal common pathway by which diﬀerent emetic inputs trigger\xa0vomiting.', 'role': 'assistant'}]