1. Chapter 27
Section 1 Disease
Bellringer
Brainstorm as many different names of diseases as you can. Don’t forget to list both physical illnesses and mental illnesses. How do you think people get these diseases?

2. Chapter 27
Section 1 Disease
Objectives
Explain the difference between infectious diseases and noninfectious disease.
Identify five ways that you might come into contact with a pathogen.
Discuss four methods that have helped reduce the spread of disease.

3. Chapter 27 Causes of Disease
Section 1 Disease
Causes of Disease
Some diseases, such as most cancers and heart disease, are not spread from one person to another. They are called noninfectious diseases.
A disease that can be passed from one living thing to another is an infectious disease. Infectious diseases are caused by agents called pathogens.

4. Chapter 27 Pathways to Pathogens Air Contaminated Objects
Section 1 Disease
Pathways to Pathogens
Air
Contaminated Objects
Person to Person
Animals
Food and Water

5. Putting Pathogens in Their Place
Chapter 27
Section 1 Disease
Putting Pathogens in Their Place
Pasteurization The method of using heat to kill bacteria is called pasteurization.
Vaccines and Immunity The ability to resist or recover from an infectious disease is called immunity. A vaccine is a substance that helps your body develop immunity to a disease.
Antibiotics An antibiotic is a substance that can kill bacteria or slow the growth of bacteria.

6. Chapter 27 Objectives Describe how your body keeps out pathogens.
Section 2 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.

7. Chapter 27 First Lines of Defense
Section 2 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.

8. Chapter 27 Failure of First Lines
Section 2 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.

9. Cells of the Immune System
Chapter 27
Section 2 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.

10. Chapter 27 Responding to a Virus
Section 2 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.

11. Chapter 27
Section 2 Your Body’s Defenses

12. Chapter 27
Section 2 Your Body’s Defenses

13. Chapter 27
Section 2 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.

14. Chapter 27
Section 2 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.

15. Challenges to the Immune System
Chapter 27
Section 2 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.

16. Challenges to the Immune System
Chapter 27
Section 2 Your Body’s Defenses
Challenges to the Immune System
Cancer is a disease in which the 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.