Ch.40 - Jamestown School District
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Transcript Ch.40 - Jamestown School District
Unit 10 The Human Body
Ch. 40 The Immune System &
Disease
Infectious Disease
Disease - any change, other than an injury,
that disrupts homeostasis
Some diseases are produced by agents like:
bacteria, viruses, & fungi
Pathogens
Pathogens - disease-causing agents
Diseases caused by pathogens are
generally infectious disease
The Germ Theory of Disease
For thousands of years, people believed that
diseases were caused by curses, evil spirits,
or night vapors
Chemist, Louis Pasteur & bacteriologist,
Robert Koch, concluded that diseases were
caused by different types of
microorganisms, called germs
Koch’s Postulates
1. The pathogen should always be found in
the body of a sick organism, not in a healthy
one
2. The pathogen must be isolated & grown
in the lab in pure culture
Koch’s Postulates
3. When the cultured pathogens are placed
in a new host, they should cause the same
disease that infected the original host
4. The injected pathogen should be isolated
from the second host. It should be identical
to the original pathogen.
Agents of Disease
Some pathogens, including viruses & some
bacteria, destroy cells as they grow
Other bacteria release toxins that harm an
organism
Agents of Disease
Still others, especially parasitic
worms, produce sickness when
they block the flow of blood,
remove nutrients from the
digestive system, & disrupt other
bodily functions
How Diseases Are Spread
Some infectious diseases are spread from 1
person to another through coughing,
sneezing, or physical contact
Other infectious diseases are spread through
contaminated water or food
How Diseases Are Spread
Still others are spread by infected animals
Vectors - animals that carry pathogens from
person to person
Fighting Infectious Diseases
Antibiotics - compounds that kill bacteria
without harming the cells of the human or
animal hosts
The Immune System
The function of the immune system, is to
fight infection through the production of
cells that inactivate foreign substances or
cells - immunity
The immune system includes 2 general
categories of defense mechanisms:
nonspecific & specific defenses
Nonspecific Defenses
Nonspecific defenses do not discriminate
between 1 threat & another
These defenses include physical & chemical
barriers
Nonspecific Defenses
First Line of Defense:
The function is to keep pathogens out of the
body
This role is carried out by skin, mucus, sweat,
& tears
Your body’s most important
nonspecific defense is the skin
Nonspecific Defenses
Second Line of Defense:
If pathogens enter your body, they multiply
quickly, releasing toxins into your tissues
When this happens, it activates the
inflammatory response
Inflammatory response - a reaction to tissue
damage caused by injury or infection
Nonspecific Defenses
Second Line of Defense:
When pathogens enter the body, phagocytes
(white blood cells), move into the area & engulf
(eat) the pathogens
Inflammatory Response
Nonspecific Defenses
Second Line of Defense:
The immune system also releases chemicals
that increase the core body temp. - Fever
An elevated body temp. slows down or stops
the growth of some pathogens
Fever & increased # of WBC’s indicates an
infection
Nonspecific Defenses
Second Line of Defense:
Sometimes, virus-infected cells produce a
group of proteins that help other cells resist
viral infection
Interferons - “interfere” with the growth of
viruses; they inhibit the synthesis of viral
proteins in infected cells & help block viral
replication
Specific Defenses
If a pathogen gets past the body’s
nonspecific defenses, the immune system
reacts with specific defenses that attack that
particular disease-causing agent - Immune
response
Specific Defenses
Antigen - a substance that triggers this
response, includes: viruses, bacteria, &
other pathogens
2 types of lymphocytes recognize specific
antigens: B lymphocytes
(B cells) & T lymphocytes
(T cells)
Specific Defenses
B cells provide immunity against antigens
& pathogens in the body fluids - Humoral
immunity
T cells defend against abnormal cells &
pathogens inside living cells - Cellmediated immunity
Specific Defenses
Humoral Immunity:
When a pathogen invades the body, it is
recognized by B cells
These B cells grow & divide rapidly, producing
large #’s of plasma cells & memory B cells
Specific Defenses
Humoral Immunity:
Plasma cells release antibodies
Antibodies - proteins that recognize & bind to
antigens, they are carried in the bloodstream to
attack the pathogen causing the infection
Once the body has been exposed, memory B
cells remain capable of producing antibodies
specific to that pathogen
Specific Defenses
Cell-mediated Response:
T cells provide defense against
abnormal cells & pathogens
inside living cells
Specific Defenses
Although killer T cells are helpful in the
immune system, they make acceptance of
organ transplants difficult
Your immune system damages & destroys
the transplanted organ
The process is known as rejection
Acquired Immunity
Vaccination - the injection of a weakened
pathogen to produce immunity
Active immunity - immunity produced by the
body’s reaction to a vaccine
Passive immunity - when antibodies produced by
other animals are injected into the bloodstream
Acquired Immunity
Active Immunity:
It appears after exposure to an antigen, as a
result of the immune response
Active immunity may develop as a result of
natural exposure to an antigen (fighting an
infection) or from deliberate exposure to the
antigen (through a vaccine)
Acquired Immunity
Passive Immunity:
It only lasts a short time because eventually, the
body destroys the foreign antibodies
Like active immunity, it may develop naturally
or by deliberate exposure
Acquired Immunity
Passive Immunity:
1 kind of natural immunity occurs when the
mother passes antibodies to the fetus through
the placenta, or through breast milk
Immune System Disorders
There are 3 different types of immune
system disorders: allergies, autoimmune
diseases, & immunodeficiency diseases
Allergies
Allergies - overreactions of the immune
system to antigens
Common allergies include: pollen, dust,
mold, & bee stings
Allergies
When allergy-causing antigens enter the
body, they attach themselves to cells that
initiate the inflammatory response
Those cells release chemicals called
histamines
Allergies
Histamines - chemicals that increase the
flow of blood & fluids to the surrounding
area
They also increase mucus production,
resulting in sneezing, watery eyes, runny
nose, & other irritations
Asthma
Asthma - a chronic respiratory disease
where the air passages become narrower
than normal
It causes wheezing, coughing, & difficulty
in breathing
Asthma attacks can be triggered by
infections, exercise, stress, etc.
Autoimmune Diseases
Autoimmune disease - when the immune
system makes a mistake & attacks the
body’s own cells
Multiple sclerosis is an example where
antibodies destroy the functions of the
neurons in the brain & spinal cord
AIDS, an Immunodeficiency
Disease
1 type of immunodeficiency disease, the
immune system fails to develop normally
The 2nd type of immunodeficiency disease
is AIDS
AIDS, an Immunodeficiency
Disease
AIDS results from a viral infection (HIV)
that destroys helper T cells
As the # of helper T cells declines, the
normal immune response breaks down
When a person has AIDS, they die from the
inability to fight off infection, like the flu, a
cold, etc.
AIDS, an Immunodeficiency
Disease
AIDS - Acquired ImmunoDeficiency
Syndrome
HIV - Human Immunodeficiency Virus
(causes AIDS)
HIV Infection
AIDS, an Immunodeficiency
Disease
There are 4 main ways HIV can be
transmitted:
1. Sexual intercourse with an infected
individual
2. Shared needles or syringes
3. Contact with blood or blood products
4. Infected mother to child, during pregnancy,
birth, or breast-feeding
AIDS, an Immunodeficiency
Disease
The only no-risk behavior with respect to
HIV & AIDS is abstinence (no sex)
At the present time, there is no cure for
AIDS
The Environment & Your Health
Risk factor - factors that have potential to
affect health in a negative way
Environmental factors that can affect your
health include air & water quality,
poisonous wastes in landfills, & exposure to
solar radiation
Air Quality
Carbon monoxide is found in automobile
exhaust & cigarette smoke
When carbon monoxide is inhaled, it
prevents hemoglobin from carrying
oxygen
Air Quality
Lead is a particulate found in the air that
can poison the liver, kidneys, & nervous
system
Lead poisoning in babies & young children
can result in slow mental development
Air Quality
Asbestos is another particulate that may be
carried in the air
It was commonly used for insulation, &
when inhaled, it can cause lung cancer
Water Quality
Water can carry biological & chemical
pollutants
Biological pollutants, like human & animal
wastes, can contain bacteria or viruses that
cause cramps, vomiting,
diarrhea, or diseases
like hepatitis or cholera
Water Quality
Some chemical pollutants cause organ
damage
Others interfere with development of organs
& tissues, causing birth defects
Still others can damage DNA, causing
normal cells to become cancerous
Bioterrorism
Bioterrorism involves treating pathogens to
maximize their ability to infect & cause
disease
Anthrax is a disease common in cattleranching areas, not life-threatening
The spores can be treated to be spread in the
air & inhaled, producing a fatal infection
Cancer
Cancer is a life-threatening disease where
cells multiply uncontrollably & destroy
healthy tissue
Cancer cells are the bodies
own cells
Cancer
Cancer begins when cells grow & reproduce
uncontrollably, resulting in a tumor
Tumor - the formation of a mass of growing
tissue
Cancer
Benign tumors are NOT cancerous
Malignant tumors are cancerous, & are
capable of invading & destroying
surrounding healthy tissue
Cancer
Cancers are caused by defects in the genes
that regulate cell growth & division
The genetic defects may be inherited,
caused by viruses, or result from mutations
in DNA that are produced by chemicals,
radiation, or occur spontaneously
Cancer
Carcinogens - chemical compounds that are
known to cause cancer by triggering
mutations in the DNA of normal cells
Some of the most powerful chemical
carcinogens are found in tobacco smoke
Cancer
The best way to fight cancer is by
protecting your DNA from agents that cause
cancer
Regular exercise & a balanced diet, regular
checkups, self-examinations, etc., can all
help reduce your risk
Maintaining Health
To keep your immune system
working efficiently, practice
behaviors that reduce your exposure to
pathogens & maintain overall good health
Healthful behaviors include eating a healthy
diet, exercise, get plenty of rest, abstaining
from harmful activities, & have regular
checkups