This document discusses the biological basis of psychotropic drugs by reviewing brain anatomy and neurotransmitter functions. It explains that drugs target specific neurotransmitters to treat disorders like depression (targeting serotonin), bipolar disorder (targeting dopamine and norepinephrine), schizophrenia (targeting dopamine), and anxiety (targeting GABA). It provides examples of common drug classes and medications used to treat each condition, along with their mechanisms of action and side effect profiles. The goal of psychotropic drugs is to relieve mental disturbances without inducing untoward side effects.