By studying and gaining knowledge about the mechanisms of the nervous system, physiological psychologists can uncover many truths about human behavior. ... Physiological psychology studies many topics relating to the body's response to a behavior or activity in an organism.
This field is closely linked with biology (Anatomy and physiology) and medicine. It seeks to explain psychological questions in terms of physiological processes such as brain/nervous system functions. Neurotransmitters and there effect on psychological parameters. Medications that come from such research would be antidepressants for example.