Which of the following statements regarding neurotransmitters is correct?

Correct Answer: B

Rationale: Dopamine is involved in the etiology of Schizophrenia . Excess dopamine in mesolimbic pathways contributto schizophrenias positive symptoms (e.g., hallucinations), per the dopamine hypothesis. Choice A is false; GABA is inhibitory. Choice C is incorrect; tryptophan forms serotonin, not acetylcholine (choline is its precursor). Choice D is wrong; acetylcholine acts on nicotinic and muscarinic receptors. is false; H1 histamine affects arousal, not vascular tone (H2 does). Bs truth dopaminrole, validated by antipsychotics contrasts with the biochemical errors of A, C, D, E, making it the correct answer.

Correct Answer: D

Rationale: Hydrocephalus is a condition characterized by an abnormal accumulation of cerebrospinal fluid (CSF) within the brain, leading to increased intracranial pressure. This can cause the skull to expand and take on a square or boxlike shape, especially in infants whose cranial suturhave not yet fused. Kleinfelter syndrome is a genetic disorder involving an extra X chromosome in males, primarily affecting sexual development and not skull shape. Neurofibromatosis is a genetic condition causing tumors along nervbut donot typically alter skull shape in this manner. Storage disorders , such as lysosomal storage diseases, lead to accumulation of substancwithin cells but are not associated with a boxlike skull. Chronic subdural hemorrhagcould cause other cranial changes, but not this specific shape. Thus, hydrocephalus is the correct answer due to its direct impact on skull morphology through fluid pressure.

Correct Answer: D

Rationale: Cranial CT is highly effective for detecting structural abnormalitilike skull fractur, intracranial hemorrhag, and acute infarcts due to its speed and sensitivity to bone and blood. Hydrocephalus is also well-visualized as it shows ventricular enlargement. However, impending herniation is the exception, as CT may not reliably detect early pressure changor subtle tissue shifts indicative of herniation risk, often requiring clinical correlation or MRI for confirmation. While CT can show gross herniation after it occurs, it is less valuable for predicting impending stagcompared to the other conditions, which are directly and immediately visible. Thus, D is the correct answer as the least reliably assessed by CT in this context.

Correct Answer: A

Rationale: Communicating hydrocephalus occurs when CSF flow is blocked after exiting the ventricles, often due to impaired absorption. Achondroplasia causforamen magnum stenosis, leading to communicating hydrocephalus from reduced CSF outflow, making it the correct answer. Aqueductal stenosis causnon-communicating hydrocephalus by blocking flow between ventricles. Chiari malformation and Dandy-Walker malformation also typically result in non-communicating hydrocephalus due to structural obstructions (tonsillar herniation or fourth ventricle cysts). Klippel-Feil syndrome affects cervical vertebrae, not directly causing hydrocephalus. Thus, A uniquely fits the communicating type among these options.

Correct Answer: A

Rationale: Minor risk factors for febrile seizure recurrence include age <1 year , family history of febrile seizur, male gender , and lower serum sodium , as these mildly elevate risk. Complex febrile seizure prolonged, focal, or multiple in 24 hours is a major risk factor, not minor, due to its stronger association with recurrence and epilepsy. This distinction is critical in clinical risk stratification: minor factors have subtler impacts, while complex seizursignal greater neurologic concern. Thus, A is the exception and correct answer, as it exceeds the scope of minor risk.