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