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Chapter 22 Understanding Diseases Table of Contents Section 1 Disease Section 2 The Germ Theory Section 3 Your Body’s Defenses Chapter 22 Section 1 Disease Objectives • Explain the difference between infectious diseases and noninfectious diseases. • Identify five ways that you might come into contact with a pathogen. • Discuss how medical discoveries have changed the way that diseases are treated. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Disease Causes of Disease • Noninfectious Diseases are diseases, such as most cancers and heart disease, that are not spread from one person to another. Noninfectious diseases may be caused by genetics or a person’s lifestyle. • Infectious Diseases are diseases that can be passed from one living thing to another. Infectious diseases are caused by agents called pathogens. Chapter 22 Section 1 Disease Pathways to Pathogens • Air Some pathogens travel through the air, such as when someone sneezes. • Contaminated Objects Drinking glasses, doorknobs, keyboards, combs, and towels that have been used by an infected person can all pass pathogens. Chapter 22 Section 1 Disease Pathways to Pathogens, continued • Person to Person You can become infected with some illnesses by kissing, shaking hands, or touching the sores of an infected person. • Animals can carry pathogens, or they can transmit a pathogen from host to a new organism. • Food and Water Bacteria growing in foods and beverages can cause illness. •http://youtu.be/jDwrTJ9qqPM Chapter 22 Section 1 Disease Putting Pathogens in Their Place • Early Attempts Many people once thought that diseases were caused by spiritual forces and needed spiritual cures. • Some thought an imbalance of body fluids caused disease, so patients were made to vomit or bleed. • After people understood that germs can cause disease, doctors could develop more effective treatments. Chapter 22 Section 1 Disease Putting Pathogens in Their Place, continued • Medical Discoveries Antibiotics are one discovery that has had a major impact on fighting pathogens. An antibiotic is a substance that can kill or slow the growth of microorganisms, such as bacteria. • Using Medicine Wisely Because medicines have such powerful effects on the body, people who use medicines must be careful. Following a doctor’s instructions for taking medicines is important. Chapter 22 Section 2 The Germ Theory Objectives • Describe the germ theory • Explain how pasteurization prevents spoilage. • Explain how vaccination works. • Describe how the germ theory affected modern health practices. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 The Germ Theory Louis Pasteur • In the 1800s, French scientist Louis Pasteur did experiments that led people to accept the germ theory. The germ theory states that microorganisms can cause disease. • Pasteur showed how microorganisms affected food, drinks, animals, and people. Microorganisms are tiny living things, such as bacteria, small fungi, and protists. Chapter 22 Section 2 The Germ Theory Pasteurization • Pasteur developed ways to prevent the damage caused by microorganisms. One method of controlling these organisms is named after Pasteur. • Pasteurization is the process of using heat to kill microorganisms in foods by heating the food to a certain temperature for a specified period of time. Chapter 22 Section 2 The Germ Theory Pasteurization, continued • Spoiled Milk Pasteur found that microorganisms enter products, like milk and wine, from the air, multiply quickly, and make waste products. • These wastes are sometimes desirable, such as when yeast waste makes bread rise. But often the wastes cause products to spoil. • Pasteur found that heating a liquid to a temperature that would kill the microorganisms could keep the liquid from spoiling. Chapter 22 Section 2 The Germ Theory Pasteurization, continued • Germ-Free Groceries Pasteurization is still used today. This practice protects dairy products and many other foods from spoiling. • Because of pasteurization, you can buy food or drinks at a grocery store and trust that you will not get sick when you eat or drink them. •http://youtu.be/1SMkYhJi5YI Chapter 22 Section 2 The Germ Theory Vaccines • In the late 1700s, Edward Jenner studied a disease called smallpox. He found that people who had been infected with cowpox seemed to have protection against smallpox. • Jenner’s work led to the first modern vaccine. A vaccine is a substance that helps your body develop resistance to a disease. Jenner vaccinated people with cowpox to protect them from smallpox. •http://youtu.be/udmwoSnvMQc Chapter 22 Section 2 The Germ Theory Vaccines, continued • Building Immunity Vaccines work because the body learns to recognize a harmless version of a pathogen. If the pathogen enters the body again, the body recognizes and fights it quickly. • The ability to resist an infections disease is called immunity. • Defeating Diseases Today, vaccines are used to fight many serious diseases. Vaccines have even controlled smallpox. Chapter 22 Section 2 The Germ Theory Controlling Germs • The acceptance of the germ theory changed public health practices dramatically. One example is the importance of sanitation practices, such as cleaning our bodies and our environments regularly. • The government has created inspection regulations to ensure food and water safety. • Quarantine policies stop serious diseases from spreading to large populations. Chapter 22 Section 3 Your Body’s Defenses Objectives • Describe how your body keeps out pathogens. • Explain how the immune system fights infections. • Describe four challenges to the immune system. Chapter 22 Section 3 Your Body’s Defenses First Lines of Defense • Your skin is made of many layers of flat cells. The outermost layers are dead. As a result, many pathogens that land on your skin have difficulty finding a live cell to infect. Chapter 22 Section 3 Your Body’s Defenses Failure of First Lines • Sometimes, skin is cut or punctured and pathogens can enter the body. Cell parts in the blood called platelets help seal the open wound so that no more pathogens can enter. • The cells and tissues that recognize and attack foreign substances in the body belong to the immune system. Chapter 22 Section 3 Your Body’s Defenses Cells of the Immune System • Macrophages engulf and digest many microorganisms or viruses that enter your body. • T cells coordinate the immune system and attack many infected cells. • B cells are immune-system cells that make antibodies. Antibodies are proteins that attach to specific antigens. Chapter 22 Section 3 Your Body’s Defenses Chapter 22 Section 3 Your Body’s Defenses Responding to a Virus • If virus particles enter your body, some of the particles may pass into body cells and begin to replicate. • Other virus particles will be engulfed and broken up by macrophages. This is just the beginning of the immune response. • This process is illustrated on the next two slides. Chapter 22 Section 3 Your Body’s Defenses Chapter 22 Section 3 Your Body’s Defenses Chapter 22 Section 3 Your Body’s Defenses Fevers • A moderate fever of one or two degrees actually helps you get well faster because it slows the growth of some pathogens. • A fever also helps B cells and T cells multiply faster. Chapter 22 Section 3 Your Body’s Defenses Memory Cells • Memory B cells are cells in your immune system that “remember” how to make an antibody for a particular pathogen. • If the pathogen shows up again, the memory B cells produce B cells that make enough antibodies in just 3 or 4 days to protect you. •http://youtu.be/pddZViGAJ7I Chapter 22 Section 3 Your Body’s Defenses Challenges to the Immune System • Allergies happen when the immune system overreacts to antigens that are not dangerous to the body. • Autoimmune Disease is a disease in which the immune system attacks the body’s own cells. In an autoimmune disease, immune-system cells mistake body cells for pathogens. Chapter 22 Section 3 Your Body’s Defenses Challenges to the Immune System, continued • Cancer is a disease in which cells begin dividing at an uncontrolled rate and become invasive. • AIDS The human immunodeficiency virus (HIV) causes acquired immune deficiency syndrome (AIDS). HIV infects the immune system itself, using helper T cells as factories to produce more viruses. Chapter 22 Understanding Diseases Concept Map Use the terms below to complete the concept map on the next slide. hemophilia pathogens immune system fungi viruses protists infectious diseases noninfectious diseases Chapter 22 Understanding Diseases Chapter 22 Understanding Diseases End of Chapter 22 Show