Chapter 40 The Immune System & Disease

1. Chapter 40 The Immune System & Disease Section 40-1 Infectious Diseases

2. Disease • Any change, other than an injury, that disrupts the normal functions of the body • Produced by: 1. bacteria 2. viruses 3. fungi 4. materials in the environment 5. inherited traits • Pathogens – disease causing agents • Diseases caused by pathogens are generally called “Infectious Diseases”

3. Germ Theory of Disease • Scientists Pasteur & Koch concluded that infectious diseases were caused by microoganisms of different types, commonly called GERMS. • Koch developed a series of rules still used today to identify microorganisms that causes a specific disease, called Koch’s Postulates

4. Koch’s Postulates • Turn to page 1032 & copy the 4 main rules • Identifying pathogens that cause disease is the first step toward preventing or curing the sicknesses they produce

5. Agents of Disease • The human body provides just the right condition for the growth of many pathogens (right temp, watery environment, & lots of nutrients) • Some pathogens (viruses/bacteria) destroy cells as they grow • Bacteria release toxins that harm the body • Parasitic worms removes nutrients & cause body functions to shut down

6. Viruses • Tiny particles that invade & replicate within living cells • Attach to cell, insert DNA/RNA into nucleus and take over the cell’s functions • Can infect every type of organism • Colds, flu, smallpox, chicken pox, herpes, HIV • No cure

7. Bacteria • Most are harmless to humans • Few are deadly • Cause disease 2 ways: 1. break down tissue in infected organism for food 2. release toxins that harm body • Ear infections, strep throat, anthrax

8. Protists • Small parasites that live on insects, animals, plants and contaminated water • Cause the single most damaging infectious disease – MALARIA

9. Worms • Flatworms & roundworms are responsible for many human diseases • Usually are found in contaminated water or living on other organisms • Tapeworm, ringworm & hookworms are examples

10. Fungi • Most are harmless to human • Athlete’s Foot – cause by Tinea, that penetrates the outer layers of the skin • Can infect the nails, mouth & throat

11. How Diseases are Spread • From 1 person to another through coughing, or PHYSICAL CONTACT • Through contaminated water or food • Spread through infected animals

12. Direct Physical Contact • Through touching a person who is infected • Through sexual contact – this includes kissing !!!!

13. Indirect Physical Contact • Carried through the air – coughs & sneezes • Touching an object that has pathogens on it • Can be prevented: 1. cover mouth when coughing/sneezing 2. washing hands

14. Contaminated Food & Water • Food poisoning is caused by eating food that contains pathogens • Bacteria is always present in uncooked meat • Bacteria grow rapidly in warm, partially cooked food • Contaminated water causes disease, especially in areas with poor sanitation & untreated sewage

15. Infected Animals • Animals also spread disease • Animals that carry pathogens from person to person are called VECTORS • Malaria, Lyme disease, West Nile Virus, rabies are diseases carried by vectors

16. Fighting Infectious Diseases • Prevention isn’t always possible • Some medicines have been developed to fight pathogens • Antibiotics – compounds that kill bacteria without harming the cells of the organism • Antibiotics have no effect on viruses, only bacteria • Antiviral medicines – stop the ability of viruses to invade the cells

17. Over the Counter Medicines • Treat only the symptoms of the disease • Help you feel better – but does not treat the cause of the infection • Best treatment – rest, well-balanced diet, & plenty of fluids

18. Section 40-2 Immune System • A series of defenses that guard your body against disease • Recognizes, attacks, destroys, & “remembers” each type of pathogen that enters the body • Produces specialized cells that inactivate the pathogen • Function: to fight infection by producing cells that inactivate foreign substances or cells • This is called IMMUNITY

19. Nonspecific Defenses • The fortress walls around the body • Do not discriminate between 1 threat and another (reacts the same no matter what) • Include physical & chemical barriers • 1st Line of Defense: 1. Most important – SKIN 2. mucus, saliva, tears, oil & sweat glands • 2nd Line of Defense: inflammatory response

20. Skin • Very few pathogens can get across the layers of dead cells on the surface • When broken (cuts or wounds), pathogens enter very easily & multiply • Causes symptoms of INFECTION: 1. swelling 2. redness 3. pain 4. heat

21. Secretions of the Body • Mucus, saliva and tears - all contain LYSOZYME – breaks down the cell walls of bacteria • Oil & sweat glands produce an acidic environment on the skin that kills many bacteria • Mucus in mouth & nose help trap pathogens • Stomach acids & digestive enzymes destroy many pathogens that get in your stomach

22. Inflammatory Response • A nonspecific defense reaction to tissue damage caused by injury or infection • Millions of white blood cells are produced – which fight the infection • Blood vessels near the wound expand, allowing the WBCs to travel faster to infected tissue • WBCs engulf & destroy bacteria • Area becomes swollen & painful • Body release chemicals to increase body temp. – fever – slows or stops the growth of the pathogen • Fever also causes heart rate to increase which pushes WBCs to infected tissue faster

23. Interferons • Proteins that help other cells resist viral infections • Interfere with the growth of the virus • Slows down the progress of the infection & gives the immune system time to respond

24. Specific Defenses • If a pathogen gets through the nonspecific defenses, the body STARTS the IMMUNE RESPONSE • ANTIGENS: substances that trigger this response – viruses, bacteria • Cells in the immune system can recognize these antigens are called - lymphocytes

25. Lymphoctyes • B Cells – provide immunity against antigens & pathogens in body fluids - this is called HUMORAL IMMUNITY • T-cells – provide defense against abnormal cells & pathogens inside living cells. - this is called CELL-MEDIATED IMMUNITY

26. Humoral Immunity • When a pathogen enters the body, it is recognized by a small amount of B cells • These B cells grow & divide rapidly – producing many memory B cells & Plasma cells

27. Plasma cells • Plasma cells release ANTIBODIES – recognize & bind to antigens • Antibodies attack the pathogen until it has taken it over • Once infection is gone, the plasma cells die & stop producing antibodies

28. Memory B Cells • Remember every pathogen that enters the body • Able to produce antibodies if exposed again • Greatly reduces the chance of being infected again

29. Antibody Structure • Shaped like a Y and has 2 binding sites to connect with antigens • The different shapes give antibodies the ability to recognize a large variety of antigens • Its estimated that a healthy adult can produce about 100 million different types of antibodies

30. Cell-Mediated Immunity • The body’s primary defense against its own cells when they have become cancerous or infected by viruses • Also important in fighting infection by fungi & protists • Viruses & other pathogens can not be destroyed by antibodies alone

31. Process of cell mediated immunity • T cells divide & change into Killer T cells, Helper T cells, & Memory T cells • Killer T cells find & destroy the pathogen or foreign tissue that contains the antigen • Helper T cells produce Memory T cells • Memory T cells remember the antigen in case of future invasion • Once pathogen is taken over, Suppressor T cells shut down Killer T cells

32. Acquired Immunity • when immunity is taken from outside the body – not naturally made • Two types • Active Immunity • Passive Immunity

33. Active Immunity • Vaccination – injection of a weakened form of a pathogen to produce immunity • More than 20 serious human diseases can be prevented by vaccinations • Modern vaccines stimulate the immune system to create millions of plasma cells ready to produce specific types of antibodies • When the body reacts to the vaccines it is known as Active Immunity

34. Passive Immunity • When antibodies produced by other animals against a pathogen are injected into the bloodstream • Last only a short time • Can develop naturally - passing from mother to child through placenta or breast feeing • or by deliberate exposure - vaccines for malaria or when someone is bitten from snake or rodent