Download Table of Contents Chapter 22

Chapter 22
Understanding Diseases
Table of Contents
Section 1 Disease
Section 2 The Germ Theory
Section 3 Your Body’s Defenses
Chapter 22
Section 1 Disease
Objectives
• Explain the difference between infectious
diseases and noninfectious diseases.
• Identify five ways that you might come into
contact with a pathogen.
• Discuss how medical discoveries have changed
the way that diseases are treated.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 22
Section 1 Disease
Causes of Disease
• Noninfectious Diseases are diseases, such as
most cancers and heart disease, that are not
spread from one person to another. Noninfectious
diseases may be caused by genetics or a
person’s lifestyle.
• Infectious Diseases are diseases that can be
passed from one living thing to another.
Infectious diseases are caused by agents called
pathogens.
Chapter 22
Section 1 Disease
Pathways to Pathogens
• Air Some pathogens travel through the air, such
as when someone sneezes.
• Contaminated Objects Drinking glasses,
doorknobs, keyboards, combs, and towels that have
been used by an infected person can all pass
pathogens.
Chapter 22
Section 1 Disease
Pathways to Pathogens, continued
• Person to Person You can become infected with
some illnesses by kissing, shaking hands, or
touching the sores of an infected person.
• Animals can carry pathogens, or they can
transmit a pathogen from host to a new organism.
• Food and Water Bacteria growing in foods and
beverages can cause illness.
•http://youtu.be/jDwrTJ9qqPM
Chapter 22
Section 1 Disease
Putting Pathogens in Their Place
• Early Attempts Many people once thought that
diseases were caused by spiritual forces and
needed spiritual cures.
• Some thought an imbalance of body fluids
caused disease, so patients were made to vomit or
bleed.
• After people understood that germs can cause
disease, doctors could develop more effective
treatments.
Chapter 22
Section 1 Disease
Putting Pathogens in Their Place, continued
• Medical Discoveries Antibiotics are one
discovery that has had a major impact on fighting
pathogens. An antibiotic is a substance that can
kill or slow the growth of microorganisms, such
as bacteria.
• Using Medicine Wisely Because medicines
have such powerful effects on the body, people
who use medicines must be careful. Following a
doctor’s instructions for taking medicines is
important.
Chapter 22
Section 2 The Germ Theory
Objectives
• Describe the germ theory
• Explain how pasteurization prevents spoilage.
• Explain how vaccination works.
• Describe how the germ theory affected modern
health practices.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 22
Section 2 The Germ Theory
Louis Pasteur
• In the 1800s, French scientist Louis Pasteur did
experiments that led people to accept the germ
theory. The germ theory states that
microorganisms can cause disease.
• Pasteur showed how microorganisms affected
food, drinks, animals, and people.
Microorganisms are tiny living things, such as
bacteria, small fungi, and protists.
Chapter 22
Section 2 The Germ Theory
Pasteurization
• Pasteur developed ways to prevent the damage
caused by microorganisms. One method of
controlling these organisms is named after
Pasteur.
• Pasteurization is the process of using heat to kill
microorganisms in foods by heating the food to a
certain temperature for a specified period of time.
Chapter 22
Section 2 The Germ Theory
Pasteurization, continued
• Spoiled Milk Pasteur found that microorganisms
enter products, like milk and wine, from the air,
multiply quickly, and make waste products.
• These wastes are sometimes desirable, such as
when yeast waste makes bread rise. But often the
wastes cause products to spoil.
• Pasteur found that heating a liquid to a
temperature that would kill the microorganisms
could keep the liquid from spoiling.
Chapter 22
Section 2 The Germ Theory
Pasteurization, continued
• Germ-Free Groceries Pasteurization is still
used today. This practice protects dairy
products and many other foods from spoiling.
• Because of pasteurization, you can buy food
or drinks at a grocery store and trust that you
will not get sick when you eat or drink them.
•http://youtu.be/1SMkYhJi5YI
Chapter 22
Section 2 The Germ Theory
Vaccines
• In the late 1700s, Edward Jenner studied a
disease called smallpox. He found that people
who had been infected with cowpox seemed to
have protection against smallpox.
• Jenner’s work led to the first modern vaccine. A
vaccine is a substance that helps your body
develop resistance to a disease. Jenner
vaccinated people with cowpox to protect them
from smallpox.
•http://youtu.be/udmwoSnvMQc
Chapter 22
Section 2 The Germ Theory
Vaccines, continued
• Building Immunity Vaccines work because the
body learns to recognize a harmless version of a
pathogen. If the pathogen enters the body again,
the body recognizes and fights it quickly.
• The ability to resist an infections disease is
called immunity.
• Defeating Diseases Today, vaccines are used to
fight many serious diseases. Vaccines have even
controlled smallpox.
Chapter 22
Section 2 The Germ Theory
Controlling Germs
• The acceptance of the germ theory changed
public health practices dramatically. One example
is the importance of sanitation practices, such as
cleaning our bodies and our environments
regularly.
• The government has created inspection
regulations to ensure food and water safety.
• Quarantine policies stop serious diseases from
spreading to large populations.
Chapter 22
Section 3 Your Body’s Defenses
Objectives
• Describe how your body keeps out pathogens.
• Explain how the immune system fights
infections.
• Describe four challenges to the immune
system.
Chapter 22
Section 3 Your Body’s Defenses
First Lines of Defense
• Your skin is made
of many layers of
flat cells. The
outermost layers
are dead. As a
result, many
pathogens that land
on your skin have
difficulty finding a
live cell to infect.
Chapter 22
Section 3 Your Body’s Defenses
Failure of First Lines
• Sometimes, skin is cut or punctured and
pathogens can enter the body. Cell parts in the
blood called platelets help seal the open wound
so that no more pathogens can enter.
• The cells and tissues that recognize and attack
foreign substances in the body belong to the
immune system.
Chapter 22
Section 3 Your Body’s Defenses
Cells of the Immune System
• Macrophages engulf and digest many microorganisms or viruses that enter your body.
• T cells coordinate the immune system and attack
many infected cells.
• B cells are immune-system cells that make
antibodies. Antibodies are proteins that attach to
specific antigens.
Chapter 22
Section 3 Your Body’s Defenses
Chapter 22
Section 3 Your Body’s Defenses
Responding to a Virus
• If virus particles enter your body, some of the
particles may pass into body cells and begin to
replicate.
• Other virus particles will be engulfed and broken
up by macrophages. This is just the beginning of
the immune response.
• This process is illustrated on the next two slides.
Chapter 22
Section 3 Your Body’s Defenses
Chapter 22
Section 3 Your Body’s Defenses
Chapter 22
Section 3 Your Body’s Defenses
Fevers
• A moderate fever of
one or two degrees
actually helps you
get well faster
because it slows the
growth of some
pathogens.
• A fever also helps
B cells and T cells
multiply faster.
Chapter 22
Section 3 Your Body’s Defenses
Memory Cells
• Memory B cells are cells in your immune system
that “remember” how to make an antibody for a
particular pathogen.
• If the pathogen shows up again, the memory B
cells produce B cells that make enough
antibodies in just 3 or 4 days to protect you.
•http://youtu.be/pddZViGAJ7I
Chapter 22
Section 3 Your Body’s Defenses
Challenges to the Immune System
• Allergies happen when the immune system overreacts to antigens that are not dangerous to the
body.
• Autoimmune Disease is a disease in which the
immune system attacks the body’s own cells. In
an autoimmune disease, immune-system cells
mistake body cells for pathogens.
Chapter 22
Section 3 Your Body’s Defenses
Challenges to the Immune System, continued
• Cancer is a disease in which cells begin dividing
at an uncontrolled rate and become invasive.
• AIDS The human immunodeficiency virus (HIV)
causes acquired immune deficiency syndrome
(AIDS). HIV infects the immune system itself, using
helper T cells as factories to produce more viruses.
Chapter 22
Understanding Diseases
Concept Map
Use the terms below to complete the concept map
on the next slide.
hemophilia
pathogens
immune system
fungi
viruses
protists
infectious diseases
noninfectious diseases
Chapter 22
Understanding Diseases
Chapter 22
Understanding Diseases
End of Chapter 22 Show