Basic Sciences Relevant to Psychiatry
Part I basic-science questions test whether you can connect neurobiology to bedside psychiatry: neuroanatomy, neurotransmitters, genetics, development, epidemiology, and drug mechanisms. The aim is mechanistic reasoning, not isolated fact recall.
Core rules
- Dopamine pathways: mesolimbic/mesocortical (psychosis, motivation), nigrostriatal (movement), tuberoinfundibular (prolactin). D2 blockade treats psychosis but can cause extrapyramidal symptoms, hyperprolactinemia, and tardive dyskinesia.
- Glutamate/GABA balance, HPA-axis stress response, sleep architecture, and neuroplasticity explain symptom clusters and treatment lag.
- Psychiatric genetics is polygenic and probabilistic; heritability is population-level, not a prediction for one person.
- Neuroimaging and biomarkers are research or exclusion tools, not diagnostic tests for common disorders.
Worked example
A patient with schizophrenia develops rigidity and tremor after starting a high-potency antipsychotic. Reasoning: mesolimbic D2 blockade helps psychosis, but nigrostriatal blockade produces extrapyramidal symptoms. A low-potency or atypical agent may reduce EPS but brings metabolic or anticholinergic burdens; clozapine has low EPS risk but requires blood monitoring.
Traps
Do not reduce disorders to one neurotransmitter deficiency. Do not infer causality from cross-sectional imaging. Do not forget that drugs act on multiple receptors, and that age, renal/hepatic function, and interactions change exposure.