Transcript The Immune System

The Immune System
The Body’s Defense
The Body’s Lines of Defense
 The body has three lines of defense against pathogens:
1. Barriers - skin, breathing passages, mouth, and stomach
trap and kill most pathogens.
2. Inflammatory Response - fluid and some WBC’s leak
from blood vessels into tissues to fight pathogens.
 The WBC’s are called phagocytes- they engulf and
destroy the pathogens.
 Inflammatory responses include a red, swollen, warm
area and sometimes fever.
3. Immune Response- these cells can distinguish between
different kinds of pathogens and react to each kind with
a specific defense.
Lymphocytes
 WBC’s that target specific pathogens are called lymphocytes.
 2 major types:
1. T Cells- identify pathogens by recognizing their antigens.
 Antigens are molecules that the immune system
recognizes as either a part of your body or coming
from outside your body.
2. B Cells- produce chemicals called antibodies.
 Antibodies bind to antigens and destroy them.
 Each kind of B Cell produces an antibody that can
only bind to one kind of antigen.
Non-Infectious Diseases
 Non-Infectious diseases are NOT caused by micro-organisms
and are NOT spread from person to person.
1. Allergy- the immune system is overly sensitive to a foreign
substance- something not normally found in the body.
 Allergen- any substance that causes an allergy: dust,
pollen, molds, some foods or medicines.
 Histamine- chemical responsible for symptoms of
allergies, like sneezing or watery eyes.
 Asthma- when the respiratory passages narrow causing
the person to wheeze and become short of breath.
Non-Infectious Diseases
2. Diabetes- when either your pancreas fails to produce enough
insulin or your body’s cells cannot use it properly. As a result,
there are high levels of glucose in the blood and glucose is
excreted in the urine. The body cells do not contain enough
glucose.
 Insulin - produced by pancreas- chemical that enables your
cells to take in glucose from the blood and use it for energy.
 Type I Diabetes- most serious- person needs insulin injections.
 Type II Diabetes - controlled by diet, weight control, and
exercise.
Non-Infectious Diseases
3. Cancer - a disease in which cells multiply uncontrollably, over
and over, destroying healthy tissue in the process.
 Tumors develop when a cancerous cell divides over and
over to form abnormal tissue masses.
 Surgery, drugs, and radiation are used to treat cancer.
 Carcinogens are substances or factors in the environment
that can cause cancer. Avoid carcinogens such as tobacco or
over-exposure to sunlight.
Infectious Diseases
 Infectious diseases are disease that can pass from one
organism to another.
 Pathogens are organisms that cause disease.
Diseases caused by pathogens are infectious.
 The four major groups of human pathogens are:
1. Bacteria
2. Viruses
3. Fungi
4. Protists
Infectious Diseases
 Bacteria- one-celled microorganisms
 Examples include strep throat and tetanus.
 Other bacterial pathogens produce a poison called a
toxin that damages cells.
 Viruses- smallest pathogens
 Cannot reproduce unless inside living cells.
 When viruses infect cells, the cells are damaged or
destroyed, and the damaged cells release new
viruses to infect other cells.
 Examples include influenza (flu), colds, chicken pox,
and AIDS.
Infectious Diseases
 Fungi- example- athlete’s foot
 Protist- example- malaria
 Sources of pathogens include:
 Another person - physical contact like shaking hands, or
indirect contact like sneezing or coughing.
 Contaminated object - eating food, drinking water, or using
silverware that’s infected.
 Animal Bite
 Environment - tetanus and botulism live naturally in the
environment.
Preventing Infectious Disease
 Immunity- the body’s ability to destroy pathogens
before they can cause disease
 Two types of immunity:
1. Active- antibodies come from the person
2. Passive- antibodies come from outside the person
Preventing Infectious Disease
1. Active Immunity -occurs when a person’s own immune
system produces antibodies in response to the presence of
a pathogen.
 T Cells and B Cells help destroy pathogens and keep a
“memory” of the pathogen’s antigen.
 Lasts for many years and sometimes for life. Ex: chicken
pox.
 Vaccination - (immunization)- harmless antigens are
deliberately introduced to a person’s body to produce active
immunity.
 Vaccine - the substance used in vaccinations. Consists of
pathogens that have been weakened or killed.
Preventing Infectious Disease
2. Passive Immunity - when the antibodies that fight the
pathogen come from another source rather than the
person’s own body
 Lasts no more than a few months.
 Babies acquire passive immunity to some diseases
before birth from their mother.
 You develop immunity from some diseases because you
have had them before or you have been vaccinated. You
will still become sick from them from time to time.
 Antibiotics - chemicals that kill or slow down the growth
of bacteria.
 No medications cure viral illnesses!!