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Chapter 6
Body Defenses and
Disease
Section 1- Disease
 Noninfectious disease: a disease that
cannot spread from one individual to
another.
 These can be caused by a variety of
factors including heredity and unhealthy
life choices such as smoking, not
exercising and eating unhealthy foods.
 Avoiding these harmful habits may help
you avoid noninfectious diseases.
Disease cont…
 Infectious disease: a disease that is
caused by a pathogen and that can be
spread from one individual to another.
 Pathogen: a microorganism, another
organism, a virus, or a protein that causes
disease.
 Pathogens depend on living things to
reproduce.
Pathway to Pathogens
 There are many ways that pathogens can
be passed from person to person.
 1. Air: pathogens can travel through air
and be ingested by someone while
breathing. One sneeze has more than
100,000 tiny droplets on moisture that
could contain pathogens.
 2. Contaminated Objects: pathogens can
live on objects for a given amount of time.
If the healthy person touches the
contaminated object, the pathogen is
passed to them.
 3. Person to Person: Pathogens can be
spread from person-to-person through
direct contact with the infected person
through fluids. You can become infected
through kissing, shaking hands, or
touching sores of an infected person.
 4. Animals: Pathogens can be carried by
animals. The pathogens can reside in their
fur, eyes, or mouth. After touching an
unfamiliar dog or cat, you should wash
your hands before touching yourself.
 5. Food and Water: The water supply in
the USA is generally safe, but accidents
do occur and pathogens can make it
into the water supply and cause
illnesses. Meat, fish and eggs that are
not cooked enough can contain harmful
bacteria or parasites. Refrigerate foods
properly to decrease chance of bacteria
forming. Washing all used cooking
surfaces also helps to fight the spread
of bacteria.
Dealing with Pathogens
 Pasteurization: invented by Louis
Pasteur. He discovered that by bring
certain substances to a boil he was able to
kill a large amount of bacteria. This
method is still used today with things such
as milk, cheese and wine.
 Vaccines and Immunity:
Immunity: the ability to resist or to recover
from an infectious disease
Vaccine: a substance that helps your body
develop an immunity to a disease.
Dealing with Pathogens cont…
 Vaccines are used throughout the world to
prevent many diseases that were deadly
years ago.
 Modern vaccines contain pathogens that
are killed or specially treated and it allows
your body to build up a defense against
the disease.
 Antibiotics: a substance that can kill
bacteria or slow the growth of bacteria.
They are also used for the treatment of
fungi.
Dealing with Pathogens cont…
 Viruses, such as the common cold, are not
affected by antibiotics. Antibiotics can only
kill living things.
 Viruses are not considered alive because
they can not reproduce on their own.
 To reproduce, viruses are dependent on
organisms.
 In the past, the only way to destroy viruses
was to locate and kill the cells that the
viruses had invaded.There have been
many advances in medicine to allow for
medications to kill viruses.
Sect. 2-Your Body’s Defenses
First Lines of Defense
 Organisms that try to enter your eyes or
mouth are usually destroyed by special
enzymes.
 Pathogens that enter through your nose
are usually pulled down the throat by
mucus to your stomach where they are
quickly destroyed by the stomach’s
environment.
 Your skin has many layers, the outermost
is dead cells. As a result, many pathogens
have a hard time finding a live cell to
infect.
 The dead skin calls are constantly
dropping off your body and as they do
pathogens fll off with them.
 In addition, glands secrete oil onto your
skins secrete oil onto your skin’s surface
which kills many pathogens.
Failure of First Lines
 When skin is cut or punctured pathogens
can enter the body. The body acts quickly
to keep out as many pathogens as
possible.
 Blood flow to the injured area increases.
 Cell parts in the blood called platelets help
to seal the wound so no more pathogens
can get inside.
 Immune system: the cells and tissue that
recognize and attack foreign substances in
the body.
 The immune system is not localized in any
one place in your body.
 The immune system is not controlled by
any one organ such as the brain either.
 The immune system is a team of individual
cells, tissues, and organs that work
together to keep you safe from invading
pathogens.
Cells of the Immune System
 Macrophage: an immune system cell that
engulfs pathogens and other materials.
 T-Cells: an immune system cell that
coordinates the immune system and
attacks many infected cells
 B Cell: a white blood cell that makes
antibodies.
 Antibodies: a protein made by B cells that
bind to a specific antigen
Fever
 When macrophages activate the helper T-
cells, they send a signal that tells your
brain to turn up the thermostat in your
body.
 In a few minutes, the temperature in your
body can rise several degrees.
 A fever of one or two degrees actually
helps you get well faster.
 The increase in temperature slows the
growth of some pathogens
 Helps B cells and T cells multiply faster.
Memory Cells
 Memory B Cell: a B cell that responds to
an antigen more strongly when the body is
reinfected with an antigen than it does
during its first encounter with the antigen.
 The first time you get infected with a virus
the B cell does recognize it so you will get
sick.
 After the first time your body remembers
what the virus looks like and has
developed its antigen for the virus. It is
likely you will not get sick from the same
thing as severe the second time around.
Challenges to the Immune System
 1. Allergies: a reaction to a harmless or
common substance by the body’s immune
system
 Can be caused by many things such as
food and medicines.
 Symptoms range from runny nose and
itchy eyes to more serious such as
asthma.
 Scientists believe allergies could be useful
because the mucus traps and carries away
possible infection.
Challenges cont…
 2. Autoimmune Diseases: a disease in
which the immune system attacks the
organisms own cells
 In an autoimmune disease, the immune
system cells mistake body cells for
pathogens.
 An example is rheumatoid arthritis, in
which the immune system attacks the
joints.
 Other examples include diabetes, multiple
sclerosis, and lupus.
Challenges cont…
 3. Cancer: a disease in which the cells
begin dividing at an uncontrollable rate
and become invasive.
 Can be killed by Killer T cells, until the rate
of reproduction of the cells becomes too
much for the killer T cells.
 Cancers invade nearby tissues and disrupt
the normal activities of the invaded organ
 If the reach the cardiovscular system they
can be transported to any place in the
body.
Challenges cont…
 4. AIDS: the Human Immunodeficiency Virus
(HIV) causes Acquired Immune Deficiency
Syndrome (AIDS).
 HIV infects the immune system directly.
 Uses helper T cells as factories to produce
more viruses. The helper T cells are
destroyed during this process.
 People with AIDS have very few helper T
cells so nothing activates the B cells and
killer T cells
 People don’t usually die of AIDS itself, they
die of the diseases that they cannot fight off
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