Communicable Diseases Chapter 12: Lesson 1

BELL ACTIVITY List as many different diseases as you can.

Health Goal # 31 I will choose behaviors to reduce my risk of infection with communicable disease. P. 328

Germs & Disease p. 332 Just about everyone has had some experience with disease. A disease is any condition that interferes with the proper functioning of the body or mind. Communicable diseases are caused by microorganisms, organisms so small that they can be seen only through a microscope.

Infection p. 332 An infection results when germs get inside the body, multiply, and damage body cells. If the body is unable to fight off the infection, a disease occurs.

Did you know? Bacteria are tiny, but they reproduce amazingly fast. In several hours, just one bacterium can multiply to 250,000!

Viruses, Bacteria, and Other Germs Not all germs are the same. The types of germs that cause diseases include viruses, bacteria, fungi, and protozoa. Most diseases that occur in the U.S. are caused by viruses or bacteria.

Figure 12.1 Causes of Disease p. 333 A. Viruses Bacteria Fungi Protozoa

How germs are spread p. 334 Figure 12.2 Spreading Germs Direct Contact Indirect Contact Other Contacts Contact with Animals or Insects

Lesson 2: The Immune System p. 336

What are antibodies? An antibody is a protein complex used by the immune system to identify and neutralize foreign objects like bacteria and viruses. Each antibody recognizes a specific antigen unique to its target.proteinimmune systembacteriavirusesantigen

Antibodies Antibodies that recognize viruses can block these directly by their sheer size. The virus will be unable to dock to a cell and infect it, hindered by the antibody

Defending Against Invaders Each day your body is exposed to countless germs. To protect itself against these germs, your body takes action to repel, trap, or destroy them. The body has natural barriers that keep germs out or destroy them before they can do any damage.

The 5 major barriers, or “first lines of defense” p. 336 Skin Mucuous membranes Saliva Tears Stomach acid

The Immune System’s General Reactions p. 337 When germs get inside your body, your immune system launches an attack. Three general reactions may occur, no matter what kind of microorganism has invaded. 1. Special white blood cells called phagocytes attack the invading germs. These cells actually surround the germs and destroy them. 2. The cells may release a chemical substance called interferon that stops viruses from reproducing. 3. Rising body temperature, commonly called a fever, makes it difficult for some microorganisms to reproduce.

Fighting against specific germs p. 337 To fight against specific germs, the body calls upon the lymphatic system. The lymphatic system is a secondary circulatory system that helps the body fight germs and maintain its fluid balance. The lymphatic system carries a watery fluid known as lymph.

Lymphocytes p. 337 Special white blood cells in the lymph are called lymphocytes. 2 types: B-cells & T-cells Both are important in fighting off germs and disease The lymph also contains phagocytes known as macrophages, which help the lymphocytes identify invading germs.

Antigens & Antibodies p. 337 Antigens are substances that send your immune system into action when your body is invaded by germs. The body recognizes antigens as invaders. Anitbodies are proteins that attach to antigens, keeping them from harming the body. Your immune system produces specific antibodies to fight each antigen.

Figure 12.3 p. 338 How the Immune System Responds to Germs 1-7

Immunity p. 339 Your body’s ability to resist the germs that cause a particular disease is called immunity. You develop immunity in 2 ways: Natural exposure to germs Immunization

Closing WRITE QUESTIONS AND TURN IN WHEN FINISHED. 1. What are the body’s 5 barriers against disease? 2. List 3 general reactions of the immune system. 3. Define the terms antigen and antibody.