The brain is an organ made up of cells known as neurons which communicate using chemical signals that involve neurotransmitters such as serotonin, norepinephrine, and dopamine. The turnover model, which is composed of five steps, explains the process neurotransmitters undergo in order for them to be released and have an effect. It is important to note that drugs specifically target one or more of these steps in order to be effective. The first step is biosynthesis, which is when the presynaptic cell synthesizes neurotransmitters when a precursor interacts with an enzyme. For example, when the precursor tyrosine interacts with the enzyme tyrosine hydroxylase, it becomes L-Dopa, and when that precursor interacts with the enzyme DOPA decarboxylase, the outcome is dopamine.…