This model focusses on the physical processes, such as the pathology, the biochemistry and the physiology of a disease. It does not take into account the role of a person's mind or society in the cause and treatment.
This model is effective at diagnosing and treating most diseases. It cannot be denied that it has been extremely useful throughout history by establishing the reasons that a disease occurs, and in coming up with very effective treatment regimes.
It is however very limiting. By not taking into account society in general, the prevention of disease is omitted. Many diseases affecting first world countries nowadays, such as heart disease and diabetes mellitus are very much dependent on a person's actions and beliefs.