KEY CONCEPT Germs cause many diseases in humans.

Transcription

1 Pathogens Infectious Diseases and Human Illness KEY CONCEPT Germs cause many diseases in humans.

2 Pathogens Infectious Diseases and Human Illness Germ theory states that microorganisms cause diseases. proposed by Louis Pasteur

3 Pathogens Infectious Diseases and Human Illness Disease-causing agents are called pathogens. Types of pathogens: Bacteria Viruses Fungi Protozoa Parasites Elephantiasis

4 Pathogens Infectious Diseases and Human Illness Pathogens can enter the body in different ways. Pathogens can be transferred by direct or indirect contact. 1) Indirect contact does not require touching an infected individual. touching an infected surface breathing in infected air vectors carry a pathogen and transmit it into healthy cells vector = a living organism that carries a pathogen ex: mosquito, fly, flea 2) Direct contact - requires touching an infected individual.

5 Pathogens Bacteria and Human Illness Structures of Bacteria 1) Plasmid = circular DNA 2) Cell wall = protection 3) Chromosomes = long strands of DNA

6 Pathogens Infectious Bacteria Diseases and Human Illness Structures of Bacteria 4) Plasma membrane = control what goes in and out 5) Pili = hairlike extensions which help bacteria to attach to a surface 6) Flagellum = whiplike tail 7) Capsule = protective gel-like layer surrounding cell wall

7 Pathogens Infectious Bacteria Diseases and Human Illness Characteristics of Bacteria all are prokaryotic and unicellular bacteria consist a single circular piece of DNA called plasmid some are autotrophic; some are heterotrophic some bacteria are pathogenic many are used in food production

8 Pathogens Infectious Bacteria Diseases and Human Illness Bacterial vs. Viral Diseases Bacterial Diseases - pathogenic bacteria kill healthy cells by their toxic membrane coat - can be cured by antibiotics/antiseptics if treated early

9 Pathogens Infectious Bacteria Diseases and Human Illness Bacterial vs. Viral Diseases Treatment for Bacterial Diseases 1) antibiotics - for internal use - interfere with bacteria s ability to reproduce - target specific pathogens - not effective against viruses - ex: penicillin, amoxicillin

10 Pathogens Infectious Bacteria Diseases and Human Illness Antibiotic resistance can cause medicines to become ineffective. Some bacteria in a population have genes that make them immune to antibiotics. These bacteria spread the gene, making the antibiotics useless. A bacterium carries genes for antibiotic resistance on a plasmid. A copy of the plasmid is transferred through conjugation. Resistance is quickly spread through many bacteria.

11 Pathogens Infectious Bacteria Diseases and Human Illness Bacterial vs. Viral Diseases Treatment for Bacterial Diseases 2) antiseptics - for external use - do not target the specific pathogen - ex: soap, vinegar

12 Pathogens Infectious Viruses Diseases and Human Illness Structure of a Virus Viruses have a simple structure. genetic material (DNA or RNA) capsid = a protein shell maybe a lipid envelope, a protective outer coat capsid nucleic acid lipid envelope surface proteins

13 Pathogens Infectious Viruses Diseases and Human Illness Characteristics of Viruses 1. not considered living because do not have all the properties of life 2. do not metabolize (no cellular respiration) 3. not a cell 4. do not grow 5. do not maintain homeostasis 6. they do reproduce but ONLY inside a host cell 7. cause diseases in many organisms 8. viruses are specific for the type of cell they attack

14 Pathogens Infectious Bacteria Diseases and Human Illness Bacterial vs. Viral Diseases Viral Diseases - cannot be cured by antibiotics/antiseptics - antiviral drugs can slow down viral reproduction, but cannot eliminate them - some viruses can never be completely eliminated ex: herpes, AIDS, genital warts

15 KEY CONCEPT The immune system is the body system that fights off infection and pathogens. The immune system has many responses to pathogens and foreign cells.

16 Nonspecific Responses - do not target a specific pathogen - innate immunity (natural) - first line of defense prevents pathogen from entering the body

17 Many body systems work to produce nonspecific responses. Examples of Nonspecific responses: 1) skin - has oils and sweat; acts as a impenetrable barrier 2) mucous membranes - layers of cells that produce sticky material in areas where pathogens might enter (digestive system, nasal passages, lungs and reproductive tract); help to trap pathogens

18 Many body systems work to produce nonspecific responses. 3) Inflammatory Response (inflammation) Injury histamine is released Causes capillaries to expand and become leaky (red, swollen, hot, painful) WBC and platelets move to wounded area WBC destroys pathogens by phagocytosis dead tissues form pus Platelets seal the wound

19 Many body systems work to produce nonspecific responses. Inflammatory Response (inflammation) Pin or splinter Blood clot Bacteria Swelling histamine Phagocytes Blood vessel

20 Many body systems work to produce nonspecific responses. 4) Temperature Response (fever) Temperature increases when body is infected Fevers stimulate white blood cells to mature and help to slow down bacterial growth

21 Many body systems work to produce nonspecific responses. 5) Proteins - fight off invading pathogens Complement proteins weaken pathogen membranes. Interferons prevent viruses from infecting healthy cells.

22 Many body systems work to produce nonspecific responses. 6) White Blood Cells - attack infections inside the body - phagocytes engulf and destroy pathogens

23 Many body systems work to produce nonspecific responses. 6) White Blood Cells

24 Specific Responses If the pathogens get past nonspecific response, then body launches the specific immune responses. Specific responses - target a specific pathogen - acquired immunity (developed) - second line of defense - use lymphocytes (T and B cells) to fight specific pathogens

25 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 (very specific) antigens virus

26 Two types of specific immune responses 1) Cellular immunity - uses T cells to destroy infected body cells - T cells are lymphocytes that originated in bone marrow and matured in thymus - three types of T cells: killer (cytotoxic) T cells = kill pathogens helper T cells = activate other lymphocytes suppressor T cells = regulate the number of lymphocytes

27 Two types of specific immune responses 1) Cellular immunity pathogen antigens antigens T cell receptors activated T cells memory T cells

28 Two types of specific immune responses 2) Humoral immunity - uses B cells to produce antibodies - B cells are lymphocytes originated and matured in bone marrow - two types of B cells: B plasma cells = produce antibodies that bind to the antigen making it immovable; biological handcuffs!! B memory cells = remember the antigen and produce immediate responses the 2 nd time it enters

29 Two types of specific immune responses 2) Humoral immunity B cell B cell pathogen antibodies T cell memory B cells activated B cells

30 Antigen vs. Antibody Antigen: Invading foreign substance Pathogen or Toxic chemical Elicits immune response Antibody: anti =against Body s reaction to an antigen invasion Blood protein Made by plasma cells (a type of B cells) Green antibodies battle red antigens!

31 The immune system rejects foreign tissues. Tissue rejection occurs in organ or tissue transplants. Tissue rejection is the result of an immune response. immune system detects protein markers on the donor tissue makes antibodies against the donor s tissue

32 Immunity prevents a person from getting sick from a pathogen. 1)Passive immunity - occurs without an immune response - ex: mother s milk, genetics 2) Active immunity - occurs after a specific immune response - ex: after an infection, you produce immunity against that specific pathogen

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

34 Vaccination provides immunity. stimulates a specific immune response causes memory cells and antibodies to be produced allows immune system to respond quickly to infection memory B cells 1 2 Antigens in a vaccine trigger an immune response, and memory B cells are made. A memory B cell is stimulated when the real pathogen binds to it. 3 The B cell quickly activates and makes antibodies that fight the pathogens before you get sick.

35 Innate vs. Acquired Immunity Innate Immunity: Natural; born with it Non-specific WBC: Phagocytes & Macrophages Skin, Tears, Saliva, Mucus, Sweat Acquired Immunity: Developed; build up Specific Lymphocytes (T, B cells) Passive / Active immunity Active: exposure to pathogen to obtain immunity or vaccination Passive: breast milk or injection of antibodies

36 Immune Diseases System that Weaken Disorders the Immune System KEY CONCEPT When the immune system is weakened, the body cannot fight off disease.

37 Immune Diseases System that Weaken Disorders the Immune System AIDS (Acquired Immunodeficiency Syndrome) HIV infection leads to AIDS. HIV (human immunodeficiency virus) Attacks and destroys helper T cells Body unable to recognize and attack pathogens Body unable to fight off secondary infections (flu, pneumonia, etc.)

38 Immune Diseases System that Weaken Disorders the Immune System AIDS is characterized by very low amount of T cells. HIV can stay dormant for a long time without immediately destroying the cell. HIV-positive patients usually do not die from HIV, but from the secondary infections they catch because their immune system is not working properly (compromised immune system).

39 Immune Diseases System that Weaken Disorders the Immune System HIV can be transmitted through - infected blood - body fluids -birth