Download Chapter 19

Chapter 19
Fighting Disease
Infectious Diseases






can pass from organism to another (contagious)
caused by pathogens – bacteria, viruses, fungi, protists
pasteurization is a heating process used to kill microorganisms in food like milk
another person, contaminated objects, animal bites, and the environment (soil, air,
water, food) are sources of pathogens
3 lines of defenses in the body
1. barriers that prevent pathogens from going into the body are the skin
(sweat, oil, dead skin cells, washing, scabs on cuts); breathing passages
(mucus, cilia); mouth (chemicals in saliva); stomach (acid)
2. inflammatory response by phagocytes, white blood cells that fight disease
by engulfing and destroying pathogens – affected area is red, swollen, and
warmer because blood vessels widen to bring more blood in; sometimes
you have fever which actually helps you fight the infection since many
pathogens can’t grow/reproduce in higher temperatures.
3. immune response controlled by the immune system by lymphocytes, white
blood cells that distinguish different types of pathogens (T cells) and
destroy them by releasing chemicals called antibodies (B cells). Each B
cell produces one kind of antibody and each antibody has a different
structure.
AIDS – Acquired Immunodeficiency Syndrome
- caused by HIV – human immunodeficiency virus
- HIV destroys the T cells and eventually develops AIDS
- People with AIDS become sick with diseases not normally found in
people with healthy immune systems.
- No cure; medications to survive longer
- HIV is spread through body fluids of infected person; from infected
mother to child during pregnancy, childbirth, or breast milk; sharing drug
needles; blood transfusions
- HIV doesn’t live on skin, so you can’t be infected by hugging, shaking
hands, using toilet seats, or bumping into someone playing sports



Immunity is the body’s ability to destroy pathogens before they can cause disease
- Active immunity occurs when a person’s own immune system produces
antibodies in response to the presence of pathogens. One way is getting a
certain disease once like chicken pox; another way is by vaccination
(immunization) when pathogens, either weakened or killed, are
deliberately introduced into the body by mouth, injection, or nasal sprays.
- Passive immunity occurs when antibodies are given to the person. Unlike
active, passive immunity lasts less. A baby acquires passive immunity
when antibodies from mom pass to the baby’s body.
Nobody is immune to all diseases. You can prevent disease by not sharing items,
keeping clean, covering your mouth while sneezing/coughing, sleeping right,
eating a balanced diet, and exercising.
You can recover from diseases by getting plenty of rest and drinking lots of
fluids unless your stomach is upset. Medications can help get you better also. An
antibiotic kills bacteria or slows their growth without harming the body cells. No
medications to cure viral diseases. Over-the-counter medications can help you
feel comfortable while you get better.
Noninfectious Diseases






not spread from person to person
not caused by microorganisms
Cardiovascular disease like atherosclerosis and hypertension is the leading cause
of death in America.
Allergy is a disorder in which the immune system is overly sensitive to a foreign
substance called an allergen (pollen, dust, mold, some foods, and some
medications). Antibodies, other than the ones during the immune response, signal
the cells to release histamine, a chemical that causes the allergy symptoms of
sneezing and watery eyes. Antihistamines are drugs that lessen the reaction. The
best strategy is to avoid the allergen. Asthma is an example of an allergic
condition.
Diabetes develops when a person has high levels of glucose in the blood and
excretes glucose in the urine. The person’s cells however do not have enough
glucose. This happens because the pancreas fails to produce enough insulin
(hormone that enables body cells to take in glucose from the blood and use it for
energy) or the body cells can’t use insulin properly.
Cancer is a disease in which cells multiply uncontrollably, over and over,
destroying healthy tissue in the process. Tumors are the abnormal tissue masses.
Cancerous tumors invade healthy tissues around them and destroy them. Cancer
cells can break away from a tumor and invade blood or lymph vessels which carry
them to other parts of the body. Cancer can be caused by heredity and
carcinogens like tar and UV. Surgery, drugs, and radiation can be used to treat
cancer. To reduce the risk of cancer, you need to avoid any form of tobacco, limit
sun exposure, eat a diet low in fat, eat lots of fruits and vegetables, and get regular
medical checkups.