Download Chapter 27: Communicable Diseases

Notes: Communicable Diseases
A. What Causes Disease?
1. Diseases occur when normal body functions are
disrupted.
2. There are two types of disease.
a. Noncommunicable diseases- are NOT
spread from one person to another.
(ex. Cancer)
b. Communicable diseases-are passed from
one living thing to another by pathogens
(germs that can cause diseases).
1. Four basic kinds of pathogens:
Viruses, bacteria, fungi, and protozoa
are germs that can cause disease.
B. Ways Pathogens Can Be Passed.
1. Through the air. (sneezing)
2. Contaminated objects. (bacteria/viruses on door
knobs, desks, keyboards, towels, combs, glasses)
3. Person to person. (kissing, shaking hands, touching
sores of an infected person, blood/body fluids)
4. Animals. (ex. Ringworm & Lyme disease)
5. Food and Water. (microorganisms, bacteria, improper
handling or preparation of foods, unclean
utensils/countertops.)
C. Ways to Control Pathogens
1. Pasteurization-use of heat to kill bacteria. (milk)
2. Vaccines & Immunity: Vaccines are substances that
help your body develop immunity to a disease.
a. They are sometimes LIVE but weakened
pathogens.
b. When injected, they allow your body’s
immune system to build a defense against
the disease.
1. Immunity is resistance to a disease.
3. Antibiotics-substances that can kill bacteria or slow
its growth.
a. Viruses are NOT affected by antibiotics.
4. Good hygiene-Eat right, sleep well, exercise and KEEP
YOURSELF AND YOUR ENVIRONMENT CLEAN!
D. Your Body’s Defenses
1. Eyes, Ears, Nose, Mouth and Stomach-pathogens
get trapped in mucus or wax or destroyed quickly by
enzymes and chemical digestion.
2. Skin-Of the many layers of cells that create your skin,
the outermost layers are dead, therefore the
pathogen cannot find a live cell to infect.
a. Your glands also secrete oil onto your skin
which contains chemicals that kill
pathogens.
3. Your Immune System-If skin is burned, cut or
punctured pathogens may enter your body.
a. Body reacts to keep out as many as
possible.
1. Increased blood flow to the injured
area sends platelets that help create
clots to seal the open wound.
b. Immune System is an army of individual
cells, tissues and organs that work
together to fight against pathogens.
E. Three Types Of Cells In The Immune System (handout)
1. Macrophages: These cells eat microorganisms or
viruses that have entered.
2. T Cells: Help coordinate the immune system, helping
to gather antigens (the pieces of bacteria) and
produce killer T Cells which kill any cell infected with
the antigens.
3. B Cells: Make antibodies. These are proteins that
attach to specific pathogens to destroy them.
a. Memory B Cells-it takes 2 weeks to make
antibodies for a new pathogen.
1. This is too long to prevent infection,
therefore the first time you are
infected, you get sick.
b. Once created, when that specific pathogen
enters the body again, the antibodies are
sent quickly to attach to it.
F. Fevers
1. When the macrophages activate the helper T Cells,
they chemically send a signal to the brain to turn up
the heat.
2. A slight fever helps you get better by slowing down
the growth of some pathogens.
3. Fevers also help the T & B Cells multiply faster.
4. High fevers can cause tissue and blood vessel damage.
G. Challenges to the Immune System
1. Allergies occur when the immune system overreacts to
substances (ALLERGENS) that are NOT usually
dangerous to the body.
a. Causes: Food, medicine, pollen, dust/dust
mites, animal hair & dander, mold, grass,
etc.
b. Symptoms: runny nose, itchy eyes, asthma,
Swollen throat, rash, hives, coughing,
sneezing.
2. Autoimmune disease is when the immune system
attacks the body’s own cells.
a. The system cannot tell the difference
between pathogens and some body cells.
b. Ex. Rheumatoid arthritis, Multiple
Sclerosis, Type 1 Diabetes, Lupus.
3. Cancer is abnormal cell growth.
a. Killer T Cells destroy this type of cell,
however, sometimes the cell division gets
out of the control of the immune system.
b. Cancer can invade nearby tissues.
c. Cancer can enter into the cardiovascular or
lymphatic systems allowing it to travel to
other parts of the body.
d. Cancer disrupts normal activities of the
organs invaded, often leading to death.
1. Certain radiation or chemical drugs
can kill the cancer cells or slow their
growth.
4. AIDS: Acquired Immune Deficiency Syndrome is
caused by the Human Immunodeficiency Virus.
a. HIV affects the immune system itself.
b. It uses the helper T Cells to produce more
viruses, destroying the T Cells in the
process.
1. This means the B Cells and Killer T
Cells cannot be put to work by the T
Cells.
c. Without the T Cells doing their job, the
immune system cannot attack HIV or other
pathogens.
d. People with AIDS don’t usually die of
AIDS, but from the other diseases that
they are unable to fight off without a
properly working immune system.