1. KEY CONCEPT Germs cause many diseases in humans.

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

3. Koch’s postulates support the theory.
Disease-causing agents are called pathogens.

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

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

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

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

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

13. 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 is a physical barrier to infection.
Mucous membranes trap pathogens entering the body.
The circulatory system transports immune cells.

14. 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.

15. 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

16. 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

17. KEY CONCEPT 31.3 The immune system has many responses to pathogens and foreign cells.

18. 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
capillary wall
extracellular space
white blood cell
characterized by swelling, redness, and pain

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

20. 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

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

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

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

24. 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

25. KEY CONCEPT 31.4 Living in a clean environment and building immunity help keep a person healthy.

26. Many methods are used to control pathogens.
Antibiotics and antiseptics cause pathogens to burst.

27. Antiseptics kill pathogens outside of the body.
do not target specific pathogens
examples include vinegar and soap
Antibiotics kill pathogens inside the body.
target one specific bacterium or fungus
not effective against viruses

28. 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.

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

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

31. KEY CONCEPT 31.5 An overactive immune system can make the body very unhealthy.

32. Allergies occur when the immune system responds to harmless antigens.
An allergy is an response to a harmless antigen.
Allergies are caused by allergens.
Allergens are antigens that cause an allergic reaction.
Allergens cause inflammation responses.

33. There are many different allergens.
food, e.g. peanuts, milk, wheat, etc.
airborne, e.g. pollen, dust mite feces, mold, etc.
chemical, e.g. nickel, medicine, bee stings, etc.

34. Allergens can cause anaphylaxis.
Anaphylaxis is an extreme inflammation response.
Blood vessels and airways become too porous.
If not treated immediately, anaphylaxis can cause death.

35. 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.
White blood cells attack healthy body cells.
Tissues fail because of attack.

36. There are over 60 autoimmune diseases.

37. KEY CONCEPT 31.6 When the immune system is weakened, the body cannot fight off disease.

38. Leukemia is characterized by abnormal white blood cells.
Leukemia is cancer of the bone marrow.
characterized by immature white blood cells
causes weakened immune system

39. Leukemia leads to opportunistic infections.
occur because white blood cells cannot fight infections
if immune system were healthy, would fight these infections

40. HIV targets the immune system.
The human immunodeficiency virus (HIV) is a retrovirus.
attacks and weakens the immune system
is transmitted by mixing infected blood with a bodily fluid

41. HIV infection leads to AIDS.
T cell
dead T cell
antibody
activated B cell
HIV reproduces in and destroys T cells.
The body cannot replace T cells fast enough.
T cells cannot help in immune responses.

42. AIDS is acquired immune deficiency syndrome.
several opportunistic infections
very low amount of T cells