1. Defense Against Disease
CORE 6.3

2. Examples of organisms that cause disease: Viruses
6.3.1 Define pathogen.
A pathogen is
Examples of organisms that cause disease:
Viruses
Not considered
Needs a
Causes:

4. Bacteria Prokaryote (lacks nucleus) Divides by
Causes: (diarrhea), (sore throat, affects breathing), , , , (muscle spasms),

5. Fungi
Eukaryotes
Causes: , , (yeast infection, thrush), (allergic reaction to breathing moldy crop),

6. Protozoa Animal-like protists
Causes: , (invades intestines, dysentery, diarrhea), (sleeping sickness)

7. Roundworms
Causes: , ,
Elephantiasis video clip:

8. Flatworms Pork and beef , , (bilharzias)
Schistosomiasis “swimmer’s itch” – initial invasion

9. 6.3.2 Explain why antibiotics are effective against bacteria but not against viruses.
Some work to while others may
They are naturally occurring substances obtained mainly from fungi or bacteria
Viruses are
Their reproduction relies on

10. Pathogens gain entry to the body using one of the following methods:
– diseases of the human respiratory system can be transmitted when an infected person coughs or sneezes out droplets containing pathogens, which are breathed in by an uninfected person
Ex.
– physical contact with an infected person carries the disease to an uninfected person through natural body openings (many diseases)

11. – allows pathogen to gain entry to body
– pathogens in contaminated food or water enter the body through the digestive system
Ex.
– allows pathogen to gain entry to body
– needle may contain pathogens in tiny drop of infected person’s blood left on needle; common mode of transmission in drug addicts

12. – only occurs if blood supply is contaminated with a disease such as AIDS
– sexually transmitted diseases gain entry through the soft mucous membranes of the penis and vagina during sexual intercourse
– blood-sucking insects inject their mouthparts through the skin and can transmit pathogens that they sucked out of an infected person
Ex.

13. The human body has three lines of defense against microbial attack:
6.3.3 Outline the role of skin and mucous membranes in defense against pathogens.
The human body has three lines of defense against microbial attack:
External barriers 
Intact skin acts
Dry, dead skin does necessary for microbial growth and most will be ejected when skin cells are constantly sloughed off
Skin is protected by

14. 6.3.3 Outline the role of skin and mucous membranes in defense against pathogens.
Membranes (in respiratory and digestive tracts)
The mucus also that enter body through nose or mouth
on the membranes sweep up the mucus with microbes to be swallowed, coughed or sneezed out

15. – effective against a – three categories:
6.3.4 Outline how phagocytic leucocytes ingest pathogens in the blood and in body tissues.
– effective against a – three categories:
Phagocytic cells and natural killer cells
(most important):
White blood cells that crawl around in the extracellular fluid (similar to how amoeba feed)
Also act as “ ” cells (present parts of microbe to other cells of immune system)
Phagocytosis animation:

16. 6.3.4 Outline how phagocytic leucocytes ingest pathogens in the blood and in body tissues.

17. 6.3.4 Outline how phagocytic leucocytes ingest pathogens in the blood and in body tissues.:
Another class of white blood cells
Do not directly attack microbes,
Also

18. (localized injury) – results from injury and large-scale breaches of the skin such as a cut
Inflammation occurs:
Injured area is walled off to isolate infected tissue:
Phagocytes & Killer cells are recruited:

19. Inflammatory Response:
Wound
Skin
Phagocytes move into the area and engulf the bacteria and cell debris
Bacteria enter the wound
Capillary

20. – results when Fever increases the Fever
Fever also helps by increasing the production of (increases resistance of surrounding cells to viral attack)
For more info on interferons:

21. Immune Response (specific defenses) –
Immune system consists of about (special type of white blood cell) distributed throughout the body but clustered in
Immune response results from interactions among the various types of lymphocytes and the molecules that they produce

23. A successful immune response involves:
Recognizing an invader,
Launching a successful attack to overcome the invader, and
Retaining a memory of the invader to ward off future attacks

24. Two key lymphocyte cells are involved in the immune response:
Arise from
Some of these cells are released into bloodstream and

25. Details of the Immune Response:
6.3.5 Distinguish between antigens and antibodies.
Details of the Immune Response:
Step 1:
Antigens –
Can be (usually large proteins, polysaccharides, and glycoproteins)
Antigens on our own cells are recognized as “ ” and do not stimulate an immune response
Antigen (bacteria)
Macrophage
B cell (lymphocyte) releasing antibodies that attack antigens

26. 6.3.5 Distinguish between antigens and antibodies.
The surfaces of the body’s own cells bear large proteins and polysaccharides just like microbes do
These proteins are collectively called the
MCHs are – one person’s MHCs would be recognized as foreign antigens in another person’s body
Which is why

27. 6.3.5 Distinguish between antigens and antibodies.
Any foreign material entering the body can act as an antigen and stimulate an immune response
“Anti-” means & “-gen” means , so antigen is an

28. Antibodies 6.3.5 Distinguish between antigens and antibodies.
Y-shaped molecules made of 4 polypeptides ( )
Antibodies have two sites that stick out and constantly look for antigens (and attach to antigens) and one site that sticks to the surface of its lymphocyte

29. 6.3.5 Distinguish between antigens and antibodies.
Antibodies act in two ways:
Act as
Act as effectors and circulate in bloodstream
Tips of antibodies form for antigens – each site has a specific shape and binds only to a specific type of antigen

32. – T-cells also have receptors on their surfaces
These are
Act (as compared to antibodies that act as receptors to trigger a response AND function in destroying foreign antigens)

33. Details of the Immune Response:
Step 2: – the immune system mounts two types of attacks:
Humoral Immunity is provided by
Cell-mediated Immunity is produced by

34. 6.3.6 Explain antibody production.
Humoral Immunity
Produced by – because antibodies circulate in the bloodstream, humoral immunity can only defend against invaders in blood and extracellular fluid
B cells with specific antibodies on their surfaces bind to
Binding causes B cells to divide rapidly  – resulting population of cells are

35. Daughter cells differentiate into two cell types:
6.3.6 Explain antibody production.
Daughter cells differentiate into two cell types:
: do not release antibodies but play an important role in future immunity
: become enlarged and make huge quantities of their own specific antibodies that are released into bloodstream

37. Antibodies destroy microbes in four ways:
Neutralization – antibody may
Promotion of phagocytosis – antibody may

38. Agglutination – antibodies have multiple binding sites and may bind to antigens on two different microbes, holding them together
This
Complement reactions – the antibody-antigen complex on the surface of an invading cell may trigger a series of reactions with blood proteins called the
These complement proteins bind to antibodies and attract phagocytic cells or may directly destroy invaders by creating holes in their plasma membrane (similar to natural killer cells)

40. Cell-mediated Immunity
Produced by , primary defense against
Also important in overcoming infection by fungi or protists
Three types of cells contribute to cell-mediated immunity:
Cytotoxic T-cells
Helper T-cells
Suppressor T-cells

41. Cytototoxic T-cells Release
This attack is activated when receptors on the cytotoxic T- cell’s membrane bind to antigens on surface of infected cell – create giant holes in target cell’s membrane
Animation:

42. Helper T-cells
When receptors of these cells bind to an antigen, the cells (hormone-like) that assist other immune cells in their defense of the body
The chemicals released by Helper T-cells
Very little immune response (cell-mediated or humoral) can occur without the boost provided by helper T-cells (reason why AIDS is so deadly)

43. Suppressor T-cells
Act after an infection has been conquered – help to
After infection is over, some suppressor T cells and helper T cells remain and function as memory T cells to help protect the body against future exposure to the same antigen

44. Details of the Immune Response:
Step 3: :
Memory cells allow us to retain immunity to antigens
B and T memory cells survive for many years

45. If the body is exposed to antigens the immune system has previously encountered:
The appropriate
Second immune response is – invasion is overcome so fast, there

46. Secondary Immune Response

47. Summary:

48. Summary:

49. AIDS – Acquired Immune Deficiency Syndrome Cause:
6.3.8 Discuss the cause, transmission and social implications of AIDS.
AIDS – Acquired Immune Deficiency Syndrome
Cause:
Caused by two viruses –
HIV is a – contains RNA as its genetic material
AIDS describes the

50. Effect: HIV viruses HIV reproduces by
6.3.7 Outline the effects of HIV on the immune system.
Effect:
HIV viruses
HIV reproduces by
Eventually the infected cell begins
Proliferating viruses eventually

51. As the number of helper T-cells decline, the lymphocytes are
6.3.7 Outline the effects of HIV on the immune system.
As the number of helper T-cells decline, the lymphocytes are
AIDS does not directly kill its victims,  As the helper T-cell population declines they become more susceptible to opportunistic diseases

53. 6.3.8 Discuss the cause, transmission and social implications of AIDS.
Sexual intercourse – virus is present in semen and vaginal secretions
In traces of blood on a hypodermic needle that is shared by IV drug abusers
Across the placenta from a mother to a baby, or through cuts during childbirth or in milk during breast-feeding

54. Tattoos and ear piercing with infected needles
6.3.8 Discuss the cause, transmission and social implications of AIDS.
In transfused blood or with blood products such as Factor VIII used to treat hemophiliacs
Accidents causing blood contamination – the disease can be transmitted between a patient and a surgeon during operations, and between a patient and a dentist through cuts in open skin
Tattoos and ear piercing with infected needles

55. Social Implication of AIDS:
6.3.8 Discuss the cause, transmission and social implications of AIDS.
Social Implication of AIDS:
Due to ignorance about the methods of transmission,
HIV positive people may have difficulty
Sexual life styles have changed due to the awareness of and education about AIDS –
Children may become
May