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KEY CONCEPT 31.1 Germs cause many diseases in humans.

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Presentation on theme: "KEY CONCEPT 31.1 Germs cause many diseases in humans."— Presentation transcript:

1 KEY CONCEPT 31.1 Germs cause many diseases in humans.

2 Germ theory states that microscopic particles cause certain diseases. –proposed by Louis Pasteur –led to rapid advances in understanding disease

3 Disease-causing agents are called pathogens. Koch’s postulates support the theory - Pathogen must be present in every case disease is found - Pathogen must be isolated and cultured - Healthy animal must be injected - Pathogen must be collected, isolated, and identical to original

4 There are different types of pathogens. 1. Bacteria are single-celled organisms. –cause illness by destroying cells –release toxic chemicals

5 2. Viruses are genetic material surrounded by a protein coat. –force host cells to make more viruses –very small

6 3. Fungi can be multicellular or single-celled. –take nutrients from host cells –occur in warm and damp places

7 4. Protozoa are single-celled organisms. –use host cells to complete their life cycles –take nutrients from host cell

8 5. Parasites are multicellular organisms. –grow and feed on a host –possibly kill the host

9 Different pathogen cause common infectious diseases.

10 Pathogens can enter the body in different ways. Pathogens can be transferred by direct or indirect contact. Indirect contact does not require touching an infected individual. – touching an infected surface – breathing in infected air

11 Vectors carry a pathogen and transmit it into healthy cells. Direct contact requires touching an infected individual. Includes: –kissing –sexual intercourse –hand shaking tick

12 Summary 31.1 1.What conditions must be met before a specific pathogen is proved to cause a disease? 2.Name the five general types of pathogens. Provide an example of each. 3.Name three ways a pathogen can be spread. 4.Contrast a virus with a bacteria. How do they differ in ways that they affect cells in the body? 5.What is a vector? Provide 2 examples.

13 Ch 31.2 KEY CONCEPT The immune systems consists of organs, cells, and molecules that fight infections.

14 Many body systems protect you from pathogens. The immune system is the body system that fights off infection and pathogens. Many other tissues and systems help the immune system. –Skin –Mucous membranes trap pathogens –The circulatory system transports immune cells.

15 Cells and proteins fight the body’s infections. White blood cells attack infections inside the body. –Phagocytes engulf and destroy pathogens. –T cells destroy infected cells. –B cells produce antibodies.

16 Three types of proteins fight off invading pathogens. –Complement proteins weaken pathogen membranes. –Antibodies make pathogens ineffective. –Interferons prevent viruses from infecting healthy cells. antibody pathogens

17 Immunity prevents a person from getting sick from a pathogen. In all immunity, pathogens are destroyed before you get sick. Passive immunity occurs without an immune response. –mother’s milk –genetics Active immunity occurs after a specific immune response Which would vaccines be?

18 Summary 31.2 1.How does the immune system work with other body systems to prevent and fight disease? 2.How do phagocytes help to fight infection? 3.Name the two types of immunities. Which requires white blood cells? Explain. 4.How do complement proteins differ from antibodies? 5.If a person had a disease that prevented lymphocytes from maturing, how would the immune system’s response to infection change?

19 31.3 Key Concept: Many body systems work to produce nonspecific responses. Nonspecific responses are the same for every pathogen. In inflammation, blood vessels become leaky. –white blood cells move toward infection and damaged tissue –characterized by swelling, redness, and pain capillary wall extracellular space white blood cell

20 In fever, body temperature increases. –High fevers can cause seizure, brain damage, and even death. –Low fevers stimulate white blood cells to mature.

21 Cells of the immune system produce specific responses. Specific immune responses begin with the detection of antigens. –Antigens are surface proteins on pathogens. –Each pathogen has a different antigen. virus antigens

22 pathogen antigens T cell receptors activated T cells antigens memory T cells There are two specific immune responses. –Cellular immunity uses T cells to destroy infected body cells.

23 There are two specific immune responses. –Humoral immunity uses B cells to produce antibodies. memory B cells activated B cells antibodies B cell T cell pathogen

24 Both responses produce memory cells. –specialized T and B cells –provide acquired (active) immunity B cell T cell

25 The immune system rejects foreign tissues. Tissue rejection occurs in organ or tissue transplants. –immune system detects protein markers on the donor tissue –makes antibodies against the donor’s tissue

26 Summary 31.3 1.How does inflammation help the immune system to fight pathogens? 2.What is the main difference between cellular and humoral immunity? 3.What is tissue rejection, and why does it occur? 4.Why might it be beneficial for a person to get blood or tissue donated from a relative instead of a non-related donor? 5.What are the differences between a specific and nonspecific immune response?

27 31.4 Many methods are used to control pathogens. Antibiotics and antiseptics cause pathogens to burst. Antibiotics inside body Antiseptic outside

28 Vaccines artificially produce acquired immunity. Vaccines also control pathogens and disease. –prevent illness –contain the antigen of a weakened pathogen

29 Vaccination provides immunity. stimulates a specific immune response causes memory cells to be produced allows immune system to respond quickly to infection has such a fast response, a person will not get sick Antigens in a vaccine trigger an immune response, and memory B cells are made. 1 memory B cells A memory B cell is stimulated when the real pathogen binds to it. 2 The B cell quickly activates and makes antibodies that fight the pathogens before you get sick. 3

30 31.5 Allergies occur when the immune system responds to harmless antigens. Allergies are caused by allergens. –Allergens: antigens that cause an allergic reaction. –Allergens cause inflammation responses. –Examples: foods, airborne, chemicals

31 Allergens can cause anaphylaxis. –Anaphylaxis is an extreme inflammation response. –Blood vessels and airways become too porous. –Can cause death

32 In autoimmune diseases, white blood cells attack the body’s healthy cells. Autoimmune diseases are failures of the immune system. –White blood cells cannot recognize healthy cells. –Tissues fail because of attack.

33 Ch 31.6 Leukemia is cancer of the bone marrow. –characterized by immature white blood cells –causes weakened immune system –Leads to opportunistic infections

34 HIV targets the immune system. The human immunodeficiency virus (HIV) is a retrovirus. –RNA –HIV causes host cell DNA to copy its RNA, then incorporate it into the DNA of the cell –Lysogenic until triggered to lytic

35 HIV infection leads to AIDS (Acquired Immune Deficiency Syndrome). –HIV reproduces in and destroys T cells. –The body cannot replace T cells fast enough. –T cells cannot help in immune responses. HIV T cell dead T cell antibody activated B cell

36 Summary Review Questions 1.What is the difference between specific and nonspecific response? 2.Summarize the steps the immune system takes when it your body is vaccinated. 3.Under what conditions is an antigen called an allergen? 4.What is an autoimmune disease and why might it be considered a failure of the immune system? 5.How do AIDS and HIV differ? 6.Which cells are affected by HIV and Leukemia? And what parts of the immune system do the influence?


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