health and disease

• Healthy organism

  One that is in a state of functioning just as it should be, both physically and behaviorally
• Disease

  A condition that commonly damages cells of the host and disrupts the normal functioning of the organism
• Most organisms will experience disease at some point in their lifetime
• Types of disease and health

  • Organism may become infected by pathogen
  • Mutation (change) in the organism's genes
  • Organism may be affected by environmental conditions
  • Organism may experience trauma
  • Organism's lifestyle may affect their health
• Communicable disease

  A disease that can spread between organisms
• Pathogen

  A type of microorganism that causes disease, including bacteria, viruses, protists and fungi
• Non-communicable disease

  A disease that cannot be passed from one organism to another, e.g. cardiovascular and respiratory diseases, cancers and diabetes
• Symptoms

  Changes in the organism that indicate disease is present, e.g. a symptom of multiple sclerosis can be temporary loss of vision
• Symptoms may not always be obvious, especially in the early stages of a disease
• Incubation period

  The time between being infected with a pathogen and showing symptoms of the disease
• Having one disease

  Can make it more or less likely that you will suffer from another disease
• HPV (human papillomavirus)

  A virus that can infect the reproductive system and cause cell changes resulting in certain types of cancer
• Helminths

  A type of worm that can cause disease if they get inside the human body, e.g. Trichinosis
• Infection by Trichinella spiralis may reduce the development of some autoimmune diseases
• Autoimmune disease

  Diseases in which the body's immune system recognises the body's own cells as foreign, and attacks them
• Pathogens


  Microorganisms that can cause disease
• Human body's defence system

  • Has features that stop a lot of pathogens entering the blood
  • Includes physical, chemical, and microbial defences
• Physical defences


  1. Mucus traps particles that could contain pathogens

  2. Cilia move mucus to back of throat to be swallowed

  3. Platelets clump together to plug wounds and prevent microorganisms entering blood
• Platelets


  Fragment of cells that contain substances to help form blood clots and have proteins to stick to wound site
• Chemical defences


  1. Lysozyme enzyme in tears breaks down bacteria

  2. Saliva contains molecules that kill pathogens

  3. Stomach produces hydrochloric acid to kill pathogens
• Microbial defences


  1. Gut bacteria compete with pathogens to survive

  2. If pathogens enter blood, immune system with antibodies and cells deals with them
• Even if pathogens make it past all defences to enter the blood, the immune system with antibodies and immune cells still has to deal with them