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Notes: Communicable Diseases A. What Causes Disease? 1. Diseases occur when normal body functions are disrupted. 2. There are two types of disease. a. Noncommunicable diseases- are NOT spread from one person to another. (ex. Cancer) b. Communicable diseases-are passed from one living thing to another by pathogens (germs that can cause diseases). 1. Four basic kinds of pathogens: Viruses, bacteria, fungi, and protozoa are germs that can cause disease. B. Ways Pathogens Can Be Passed. 1. Through the air. (sneezing) 2. Contaminated objects. (bacteria/viruses on door knobs, desks, keyboards, towels, combs, glasses) 3. Person to person. (kissing, shaking hands, touching sores of an infected person, blood/body fluids) 4. Animals. (ex. Ringworm & Lyme disease) 5. Food and Water. (microorganisms, bacteria, improper handling or preparation of foods, unclean utensils/countertops.) C. Ways to Control Pathogens 1. Pasteurization-use of heat to kill bacteria. (milk) 2. Vaccines & Immunity: Vaccines are substances that help your body develop immunity to a disease. a. They are sometimes LIVE but weakened pathogens. b. When injected, they allow your body’s immune system to build a defense against the disease. 1. Immunity is resistance to a disease. 3. Antibiotics-substances that can kill bacteria or slow its growth. a. Viruses are NOT affected by antibiotics. 4. Good hygiene-Eat right, sleep well, exercise and KEEP YOURSELF AND YOUR ENVIRONMENT CLEAN! D. Your Body’s Defenses 1. Eyes, Ears, Nose, Mouth and Stomach-pathogens get trapped in mucus or wax or destroyed quickly by enzymes and chemical digestion. 2. Skin-Of the many layers of cells that create your skin, the outermost layers are dead, therefore the pathogen cannot find a live cell to infect. a. Your glands also secrete oil onto your skin which contains chemicals that kill pathogens. 3. Your Immune System-If skin is burned, cut or punctured pathogens may enter your body. a. Body reacts to keep out as many as possible. 1. Increased blood flow to the injured area sends platelets that help create clots to seal the open wound. b. Immune System is an army of individual cells, tissues and organs that work together to fight against pathogens. E. Three Types Of Cells In The Immune System (handout) 1. Macrophages: These cells eat microorganisms or viruses that have entered. 2. T Cells: Help coordinate the immune system, helping to gather antigens (the pieces of bacteria) and produce killer T Cells which kill any cell infected with the antigens. 3. B Cells: Make antibodies. These are proteins that attach to specific pathogens to destroy them. a. Memory B Cells-it takes 2 weeks to make antibodies for a new pathogen. 1. This is too long to prevent infection, therefore the first time you are infected, you get sick. b. Once created, when that specific pathogen enters the body again, the antibodies are sent quickly to attach to it. F. Fevers 1. When the macrophages activate the helper T Cells, they chemically send a signal to the brain to turn up the heat. 2. A slight fever helps you get better by slowing down the growth of some pathogens. 3. Fevers also help the T & B Cells multiply faster. 4. High fevers can cause tissue and blood vessel damage. G. Challenges to the Immune System 1. Allergies occur when the immune system overreacts to substances (ALLERGENS) that are NOT usually dangerous to the body. a. Causes: Food, medicine, pollen, dust/dust mites, animal hair & dander, mold, grass, etc. b. Symptoms: runny nose, itchy eyes, asthma, Swollen throat, rash, hives, coughing, sneezing. 2. Autoimmune disease is when the immune system attacks the body’s own cells. a. The system cannot tell the difference between pathogens and some body cells. b. Ex. Rheumatoid arthritis, Multiple Sclerosis, Type 1 Diabetes, Lupus. 3. Cancer is abnormal cell growth. a. Killer T Cells destroy this type of cell, however, sometimes the cell division gets out of the control of the immune system. b. Cancer can invade nearby tissues. c. Cancer can enter into the cardiovascular or lymphatic systems allowing it to travel to other parts of the body. d. Cancer disrupts normal activities of the organs invaded, often leading to death. 1. Certain radiation or chemical drugs can kill the cancer cells or slow their growth. 4. AIDS: Acquired Immune Deficiency Syndrome is caused by the Human Immunodeficiency Virus. a. HIV affects the immune system itself. b. It uses the helper T Cells to produce more viruses, destroying the T Cells in the process. 1. This means the B Cells and Killer T Cells cannot be put to work by the T Cells. c. Without the T Cells doing their job, the immune system cannot attack HIV or other pathogens. d. People with AIDS don’t usually die of AIDS, but from the other diseases that they are unable to fight off without a properly working immune system.