solved I’m working on a nursing question and need an explanation

I’m working on a nursing question and need an explanation to help me learn.

Modern psychopharmacology is largely the story of chemical neurotransmission. One must be fluent in the language and principles of chemical neurotransmission to:

Understand the actions of drugs on the brain,
Grasp the impact of diseases upon the central nervous system,
Interpret the behavioral consequences of psychiatric medicines.

Discuss, 

When a cell is stimulated or polarized, it fires an action potential. Explain the process and how neurotransmitters are dispersed to other neighboring cells across the synapse.
Explain the concept of a drug’s half-life