This module introduces students to the broad categories of diseases and injuries from a systems approach. The students learn the contemporary knowledge and perspectives on the pathological and abnormal physiological processes that lead to these diseases and injuries, current medical interventions, including surgery and drugs, and associated complications either arising from the disease processes or medical interventions. Students learn the effects of drugs on the biological systems (for instance, interactions between chemicals and biological receptors) and the effects of biological systems on drugs (that is, absorption, distribution, metabolism and excretion of chemicals from biological systems). In addition, students learn to recognize the desired and undesired effects of medication, delivery options, adverse drug reactions that health professionals may observe. The specific roles of these health professionals in communicating adverse reactions and requesting modification in medication delivery to optimize performance and minimize pain will also be discussed.