Human Health and Disease

About this unit

Health is not just the absence of disease; it is a state of complete physical, mental and social well-being. This unit looks at common infectious diseases of humans and the pathogens that cause them, how the body defends itself through innate and acquired immunity, how vaccines work, and what goes wrong in allergies, autoimmunity, AIDS and cancer. It ends with the problems of drug and alcohol abuse, especially among adolescents, and ways to prevent them.

Key ideas

• Pathogens include bacteria, viruses, fungi, protozoans and helminths.
• Innate immunity is non-specific; acquired immunity is specific and has memory.
• B cells give humoral immunity (antibodies); T cells give cell-mediated immunity.
• Vaccines give active immunity; ready-made antibodies give passive immunity.
• HIV destroys helper T cells; cancer cells lose contact inhibition.
• Drugs such as opioids, cannabinoids and cocaine affect the nervous system and cause dependence.

How to prepare

Learn each disease with its pathogen, mode of spread and key symptom. Draw the life cycle of Plasmodium and the structure of an antibody. Memorise the sources and effects of commonly abused drugs, and the differences between benign and malignant tumours.