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