Diseases and Immunity

19.1 Types of Diseases

• Infectious Diseases: Caused by pathogens like bacteria, viruses, fungi, and parasites.
• Non-Infectious Diseases: Caused by factors such as genetics, lifestyle, and environmental conditions (e.g., cancer, heart disease).

19.2 Pathogens and Disease Transmission

• Pathogens: Microorganisms that cause disease.
• Transmission Methods:
  1. Direct Contact: Physical contact (e.g., common cold).
  2. Airborne: Coughing or sneezing (e.g., influenza).
  3. Waterborne: Contaminated water (e.g., cholera).
  4. Vector-Borne: Spread by animals (e.g., malaria).

19.3 The Immune System

• White Blood Cells (WBCs): Defend the body by engulfing pathogens (phagocytosis) or producing antibodies.
• Antibodies: Proteins that target and neutralize pathogens.
• Memory Cells: Retain information about pathogens for faster responses.

19.4 Vaccination

• Vaccination: Introduction of a harmless form of the pathogen to stimulate an immune response and protect against future infections.

19.5 Antibiotics and Antivirals

• Antibiotics: Used to treat bacterial infections.
• Antivirals: Used to treat viral infections.
• Resistance: Overuse of antibiotics can lead to antibiotic-resistant bacteria.

19.6 Cancer

• Cancer: Uncontrolled cell growth leading to tumor formation.
• Causes: Genetic mutations, environmental factors (e.g., smoking).
• Treatment: Surgery, chemotherapy, radiation therapy.