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18 multiple-choice questions and 9 flashcards on Behavioral Health & Nervous Systems/Special Senses, about 10% of the USMLE Step 1 bank. Every one carries a written rationale.
Behavioral Health & Nervous Systems/Special Senses is one of 10 chapters in CoStudy's USMLE Step 1 — Medical Licensing bank, and it holds 18 of the bank's 172 multiple-choice questions — roughly 10% of the total. That proportion is not arbitrary: chapters follow the certifying body's published exam outline, and the number of questions in each is set by that domain's published weight, so the share of your practice time this chapter takes matches the share of the real exam it accounts for.
Studying by chapter is worth doing once you have a diagnostic score. A single overall percentage tells you whether you are close; it does not tell you which domain is dragging. Working a weak chapter in isolation, and re-testing it in isolation, is the fastest way to move a score that has stalled — and it is why the mock exams in CoStudy report by domain rather than as one number.
9 questions drawn from this chapter, with the full rationale shown — the controlling principle behind the right answer, and why each wrong option tempts and fails.
A 75-year-old man with a-fib who is not anticoagulated develops sudden right-sided weakness and aphasia. Head CT excludes hemorrhage. He arrives 90 minutes after symptom onset. Which is the MOST appropriate treatment?
Answer: A — IV alteplase (tPA)
A) Correct: ischemic stroke within 4.5 hours of onset (no contraindications) → IV tPA. B) Aspirin is appropriate but inferior to tPA in this window. C) Acute heparin is NOT recommended in cardioembolic stroke acutely (no benefit, bleed risk) — common misconception trap. D) Warfarin is for secondary prevention, not acute. E) Mechanical thrombectomy is added for large-vessel occlusions, typically with NIHSS ≥6 (and selected up to 24h with imaging) — the 'only if <6' is backwards.
A 70-year-old man has progressive resting tremor, bradykinesia, rigidity, and shuffling gait. Which is the underlying pathophysiology?
Answer: A — Loss of dopaminergic neurons in the substantia nigra pars compacta with Lewy bodies
A) Correct: Parkinson disease — loss of dopaminergic neurons in SNc and α-synuclein Lewy bodies. B) GABAergic neuron loss in the caudate = Huntington disease (chorea, not parkinsonism) — off-by-one basal ganglia disorder trap. C) Cholinergic loss in nucleus basalis of Meynert = Alzheimer disease (dementia, not movement). D) Serotonin loss in raphe is associated with depression. E) Corticospinal demyelination ≈ MS or ALS, neither of which causes Parkinsonism.
A 35-year-old veteran has 4 months of intrusive memories, nightmares, hyperarousal, and avoidance of trauma-related stimuli after a combat deployment. Which is the MOST appropriate first-line treatment?
Answer: B — Trauma-focused cognitive behavioral therapy with an SSRI
B) Correct: PTSD first-line treatment is trauma-focused CBT or EMDR + SSRI (sertraline or paroxetine are FDA-approved). A) Benzodiazepines are AVOIDED in PTSD — they can worsen long-term outcomes, fail to extinguish trauma memory, and carry addiction risk in this population. C) Antipsychotics are adjunctive for refractory cases or psychotic features. D) Propranolol may reduce arousal but isn't first-line. E) Mood stabilizers are not first-line for PTSD.
A patient with a recent stroke benefits most from:
Answer: A — Rapid evaluation (imaging to distinguish ischemic vs hemorrhagic), early thrombolysis or thrombectomy for eligible ischemic strokes, blood-pressure management, antiplatelet therapy, secondary prevention, and rehabilitation — "time is brain"
A) Standard care. B/C/D) Each is incorrect.
The classic triad of Wernicke encephalopathy is:
Answer: D — Encephalopathy (confusion), oculomotor dysfunction (nystagmus, ophthalmoplegia), and gait ataxia
D) Classic thiamine-deficiency triad. A) Meningitis. B) Cardio-pulm. C) Diabetes mellitus.
Which neurotransmitter abnormality is most strongly implicated in major depressive disorder and is the target of SSRIs?
Answer: C — Serotonin
Monoamine hypothesis: depression involves reduced serotonergic (and noradrenergic) signaling. SSRIs (sertraline, fluoxetine, escitalopram, etc.) block the serotonin reuptake transporter (SERT), increasing synaptic serotonin. Dopamine (A) is more relevant to psychosis and motivation; glutamate (B) is the target of ketamine.
Which neurotransmitter is deficient in Parkinson disease and supplemented by levodopa therapy?
Answer: C — Dopamine
Parkinson disease results from loss of dopaminergic neurons in the substantia nigra pars compacta. Levodopa (L-DOPA) is the dopamine precursor that crosses the blood-brain barrier and is converted to dopamine — usually given with carbidopa to prevent peripheral conversion and side effects.
A 28-year-old woman has 3 weeks of depressed mood, anhedonia, fatigue, insomnia, decreased appetite, poor concentration, and feelings of worthlessness. She denies suicidal ideation. Which neurotransmitter pathway is MOST implicated in the response to first-line pharmacotherapy?
Answer: D — Selective inhibition of serotonin reuptake in the synaptic cleft
D) Correct: SSRIs (first-line for major depression) inhibit serotonin reuptake at the presynaptic terminal, increasing synaptic 5-HT. A) Dopamine reuptake inhibition describes bupropion or stimulants (not first-line for typical depression). C) NMDA blockade describes ketamine (rapid-acting antidepressant, second/third-line for treatment-resistant cases). B) GABA-A α1 agonism describes benzodiazepines/zolpidem (anxiolytic/hypnotic, not antidepressant). E) D2 blockade describes antipsychotics.
A 60-year-old woman presents with the worst headache of her life. Head CT is unremarkable. Lumbar puncture shows xanthochromia of the CSF. Which is the MOST likely underlying lesion?
Answer: B — Saccular (berry) aneurysm rupture
B) Correct: thunderclap headache + xanthochromia = subarachnoid hemorrhage, most commonly from rupture of a saccular aneurysm at the circle of Willis (anterior communicating artery is most common site). A) Migraine doesn't cause xanthochromia. C) AVMs typically cause intraparenchymal hemorrhage, not SAH; less common cause. D) Hypertensive bleeds are intraparenchymal (basal ganglia), not subarachnoid. E) Carotid dissection causes ischemic stroke or Horner syndrome, not SAH.
4 cards from the 9 in this chapter.
Alzheimer disease pathology?
Amyloid plaques + neurofibrillary tangles (tau). Atrophy especially hippocampus.
Defense mechanisms (mature)?
Sublimation, suppression, altruism, humor.
Guillain-Barré syndrome?
Acute demyelinating polyneuropathy. Ascending weakness post-infection. Often Campylobacter.
Sleep stages?
N1 (light), N2 (sleep spindles), N3 (slow wave), REM (dreaming).
These are a sample. The full Behavioral Health & Nervous Systems/Special Senses chapter runs 27 items with per-chapter progress tracking, on the web and in the iOS app.
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