KEY CONCEPT Germs cause many diseases in humans.

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KEY CONCEPTGerms cause many diseases in humans.
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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

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• Kochs postulates support the theory.

• Disease-causing agents are called pathogens.

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There are different types of pathogens.

• Bacteria are single-celled organisms.
• cause illness by destroying cells
• release toxic chemicals

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• Viruses are genetic material surrounded by a
  protein coat.

• force host cells to make more viruses
• very small

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• Fungi can be multicellular or single-celled.

• take nutrients from host cells
• occur in warm and damp places

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• Protozoa are single-celled organisms.

• use host cells to complete their life cycles
• take nutrients from host cell

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• Parasites are multicellular organisms.

• grow and feed on a host
• possibly kill the host

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• Different pathogen cause common infectious
  diseases.

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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

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• Vectors carry a pathogen and transmit it into
  healthy cells.

• Direct contact requires touching an infected
  individual. Includes
• kissing
• sexual intercourse
• hand shaking

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

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Cells and proteins fight the bodys infections.

• White blood cells attack infections inside the
  body.
• Phagocytes engulf and destroy pathogens.
• T cells destroy infected cells.
• B cells produce antibodies.

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• Three types of proteins fight off invading
  pathogens.

• Complement proteins weaken pathogen membranes.
• Antibodies make pathogens ineffective.

• Interferons prevent viruses from infecting
  healthy cells.

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Immunity prevents a person from getting sick from
a pathogen.

• In all immunity, pathogens are destroyed before
  you get sick.
• Passive immunity occurs withoutan immune
  response.
• mothers milk
• genetics
• Active immunity occurs after aspecific immune
  response

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KEY CONCEPT 31.3The immune system has many
responses to pathogens and foreign cells.
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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 movetoward infection
  anddamaged tissue

• characterized by swelling, redness, and pain

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• In fever, body temperature increases.

• Low fevers stimulate white blood cells to mature.

• High fevers can cause seizure, brain damage, and
  even death.

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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.

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• There are two specific immune responses.

• Cellular immunity uses T cells to destroy
  infected body cells.

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• There are two specific immune responses.

• Humoral immunity uses B cells to produce
  antibodies.

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• Both responses produce memory cells.

• specialized T and B cells
• provide acquired (active) immunity

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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 donors tissue

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KEY CONCEPT 31.4Living in a clean environment
and building immunity help keep a person healthy.
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Many methods are used to control pathogens.

• Antibiotics and antiseptics cause pathogens to
  burst.

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• 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

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• 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.

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Vaccines artificially produce acquired immunity.

• Vaccines also control pathogens and disease.
• given to prevent illness
• contain the antigen of a weakened pathogen

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• Vaccination provides immunity.

• stimulates a specific immune response

• causes memory cells to be produced

• allows immune system to respond quickly to
  infection

• has such a fast response, a person will not get
  sick

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

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• 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.

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• 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.

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In autoimmune diseases, white blood cells attack
the bodys 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.

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• There are over 60 autoimmune diseases.

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

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• Leukemia leads to opportunistic infections.

• occur because white blood cells cannot fight
  infections
• if immune system were healthy, would fight these
  infections

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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

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• HIV infection leads to AIDS.

• HIV reproduces in and destroys T cells.
• The body cannot replace T cells fast enough.
• T cells cannot help in immune responses.

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• AIDS is acquired immune deficiency syndrome.

• several opportunistic infections
• very low amount of T cells