Pharmacology may be a branch of drugs and pharmaceutical sciences which cares with the study of drug or medication action, where a drug are often broadly or narrowly defined as any man-made, natural, or endogenous (from within the body) molecule which exerts a biochemical or physiological effect on the cell, tissue, organ, or organism. Often confused with pharmacy, pharmacology may be a separate discipline within the health sciences. Pharmacology is that the study of how a drug affects a biological system and the way the body responds to the drug. The discipline encompasses the sources, chemical properties, biological effects and therapeutic uses of medicine.