Pharmacology is the study of how a drug affects a biological system and how the body responds to the drug. The discipline encompasses the sources, chemical properties, biological effects and therapeutic uses of drugs.Pharmacology integrates the knowledge of many disciplines, including medicine, pharmacy, dentistry, nursing, and veterinary medicine. This integrative nature allows pharmacology to make unique and significant contributions to human health. The interactions between drug molecules and drug receptors and the effects of these interactions are studied under the umbrella of pharmacology. The umbrella of pharmacology is a wide one. It encompasses the examination of the different classes of drugs, their therapeutic uses, their societal roles and their mechanisms of action, among other things.