Transcript Chapter 40 The immune System & Disease

Chapter 40
The Immune System & Disease
Section 40-1
Infectious Diseases
Disease
• Any change, other than an injury, that disrupts
the normal functions of the body
• Produced by:
1. bacteria
2. viruses
3. fungi
4. materials in the environment
5. inherited traits
• Pathogens – disease causing agents
• Diseases caused by pathogens are generally
called “Infectious Diseases”
Germ Theory of Disease
• Scientists Pasteur & Koch concluded that
infectious diseases were caused by
microoganisms of different types,
commonly called GERMS.
• Koch developed a series of rules still used
today to identify microorganisms that
causes a specific disease,
called Koch’s Postulates
Koch’s Postulates
• Turn to page 1032 & copy the 4 main rules
• Identifying pathogens that cause disease
is the first step toward preventing or curing
the sicknesses they produce
Agents of Disease
• The human body provides just the right
condition for the growth of many
pathogens (right temp, watery
environment, & lots of nutrients)
• Some pathogens (viruses/bacteria)
destroy cells as they grow
• Bacteria release toxins that harm the body
• Parasitic worms removes nutrients &
cause body functions to shut down
Viruses
• Tiny particles that invade & replicate within
living cells
• Attach to cell, insert DNA/RNA into
nucleus and take over the cell’s functions
• Can infect every type of organism
• Colds, flu, smallpox, chicken pox, herpes,
HIV
• No cure
Bacteria
• Most are harmless to humans
• Few are deadly
• Cause disease 2 ways:
1. break down tissue in infected
organism for food
2. release toxins that harm body
• Ear infections, strep throat, anthrax
Protists
• Small parasites that live on insects,
animals, plants and contaminated water
• Cause the single most damaging
infectious disease – MALARIA
Worms
• Flatworms & roundworms are responsible
for many human diseases
• Usually are found in contaminated water
or living on other organisms
• Tapeworm, ringworm & hookworms are
examples
Fungi
• Most are harmless to human
• Athlete’s Foot – cause by Tinea, that
penetrates the outer layers of the skin
• Can infect the nails, mouth & throat
How Diseases are Spread
• From 1 person to another through
coughing, or PHYSICAL CONTACT
• Through contaminated water or food
• Spread through infected animals
Direct Physical Contact
• Through touching a person who is infected
• Through sexual contact – this includes
kissing !!!!
Indirect Physical Contact
• Carried through the air – coughs & sneezes
• Touching an object that has pathogens on it
• Can be prevented:
1. cover mouth when coughing/sneezing
2. washing hands
Contaminated Food & Water
• Food poisoning is caused by eating food
that contains pathogens
• Bacteria is always present in uncooked
meat
• Bacteria grow rapidly in warm, partially
cooked food
• Contaminated water causes disease,
especially in areas with poor sanitation &
untreated sewage
Infected Animals
• Animals also spread disease
• Animals that carry pathogens from person
to person are called VECTORS
• Malaria, Lyme disease, West Nile Virus,
rabies are diseases carried by vectors
Fighting Infectious Diseases
• Prevention isn’t always possible
• Some medicines have been developed to
fight pathogens
• Antibiotics – compounds that kill bacteria
without harming the cells of the organism
• Antibiotics have no effect on viruses, only
bacteria
• Antiviral medicines – stop the ability of
viruses to invade the cells
Over the Counter Medicines
• Treat only the symptoms of the disease
• Help you feel better – but does not treat
the cause of the infection
• Best treatment – rest, well-balanced diet,
& plenty of fluids
Section 40-2 Immune System
• A series of defenses that guard your body
against disease
• Recognizes, attacks, destroys, & “remembers”
each type of pathogen that enters the body
• Produces specialized cells that inactivate the
pathogen
• Function: to fight infection by producing cells
that inactivate foreign substances or cells
• This is called IMMUNITY
Nonspecific Defenses
• The fortress walls around the body
• Do not discriminate between 1 threat and
another (reacts the same no matter what)
• Include physical & chemical barriers
• 1st Line of Defense:
1. Most important – SKIN
2. mucus, saliva, tears, oil & sweat
glands
• 2nd Line of Defense: inflammatory response
Skin
• Very few pathogens can get across the
layers of dead cells on the surface
• When broken (cuts or wounds), pathogens
enter very easily & multiply
• Causes symptoms of INFECTION:
1. swelling
2. redness
3. pain
4. heat
Secretions of the Body
• Mucus, saliva and tears - all contain
LYSOZYME – breaks down the cell walls
of bacteria
• Oil & sweat glands produce an acidic
environment on the skin that kills many
bacteria
• Mucus in mouth & nose help trap
pathogens
• Stomach acids & digestive enzymes
destroy many pathogens that get in your
stomach
Inflammatory Response
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1.
2.
3.
4.
5.
6.
A nonspecific defense reaction to tissue damage
caused by injury or infection
Millions of white blood cells are produced –
which fight the infection
Blood vessels near the wound expand, allowing
the WBCs to travel faster to infected tissue
WBCs engulf & destroy bacteria
Area becomes swollen & painful
Body release chemicals to increase body temp. –
fever – slows or stops the growth of the pathogen
Fever also causes heart rate to increase which
pushes WBCs to infected tissue faster
Interferons
• Proteins that help other cells resist viral
infections
• Interfere with the growth of the virus
• Slows down the progress of the infection &
gives the immune system time to respond
Specific Defenses
• If a pathogen gets through the nonspecific
defenses, the body STARTS the
IMMUNE RESPONSE
• ANTIGENS: substances that trigger this
response – viruses, bacteria
• Cells in the immune system can recognize
these antigens are called - lymphocytes
Lymphoctyes
• B Cells – provide immunity against antigens &
pathogens in body fluids
- this is called HUMORAL IMMUNITY
• T-cells – provide defense against abnormal
cells & pathogens inside living cells.
- this is called CELL-MEDIATED IMMUNITY
Humoral Immunity
• When a pathogen enters the body, it is
recognized by a small amount of B cells
• These B cells grow & divide rapidly –
producing many memory B cells &
Plasma cells
Plasma cells
• Plasma cells release ANTIBODIES –
recognize & bind to antigens
• Antibodies attack the pathogen until it has
taken it over
• Once infection is gone, the plasma cells
die & stop producing antibodies
Memory B Cells
• Remember every pathogen that enters the
body
• Able to produce antibodies if exposed
again
• Greatly reduces the chance of being
infected again
Antibody Structure
• Shaped like a Y and has 2 binding sites to
connect with antigens
• The different shapes give antibodies the
ability to recognize a large variety of
antigens
• Its estimated that a healthy adult can
produce about 100 million different types
of antibodies
Cell-Mediated Immunity
• The body’s primary defense against its
own cells when they have become
cancerous or infected by viruses
• Also important in fighting infection by fungi
& protists
• Viruses & other pathogens can not be
destroyed by antibodies alone
Process of cell mediated immunity
1. T cells divide & change into Killer T cells,
Helper T cells, & Memory T cells
2. Killer T cells find & destroy the pathogen or
foreign tissue that contains the antigen
3. Helper T cells produce Memory T cells
4. Memory T cells remember the antigen in case
of future invasion
5. Once pathogen is taken over, Suppressor T
cells shut down Killer T cells
Acquired Immunity
• when immunity is taken from outside the
body – not naturally made
• Two types
• Active Immunity
• Passive Immunity
Active Immunity
• Vaccination – injection of a weakened form of a
pathogen to produce immunity
• More than 20 serious human diseases can be
prevented by vaccinations
• Modern vaccines stimulate the immune system
to create millions of plasma cells ready to
produce specific types of antibodies
• When the body reacts to the vaccines it is known
as Active Immunity
Passive Immunity
• When antibodies produced by other
animals against a pathogen are injected
into the bloodstream
• Last only a short time
• Can develop naturally - passing from
mother to child through placenta or breast
feeing
• or by deliberate exposure - vaccines for
malaria or when someone is bitten from
snake or rodent