Download The Immune System

The Immune System
Part I
Physiology Standards: 10a-e
Germ Theory and Non-specific
defense
The Germ Theory

The germ theory states that:
– infectious diseases are caused by
microorganisms of different types,
commonly called germs
– Many believed that sickness and
poor health was the work of
‘spirits’ or some ‘higher source’
A disease is any condition that
disrupts the normal functioning
of the body
 A pathogen usually “transmits”
the disease to a host

Salmonella is a bacterium found on
and in all raw chicken!
Agents of Disease

There are many examples of
agents for diseases and they fall
into 5 major groups:
– Viruses – the most common is
influenza known as “the flu”
– Bacteria – can either break down
cells or release toxins into the
organism
– Protists – a disease that is often
transmitted by an animal like malaria
from mosquitoes
– Worms – worms use humans as
hosts while they act like parasites
– Fungi – fungus causes infections in
warm, moist places like athlete’s foot
E. coli is a bacterium
found in raw meat
Agents of Disease

Viruses vs. Bacteria
– Both cause disease, but they
act in different ways
– Viruses:
 Take over a cell’s DNA and
instruct the cell to “make” more
viruses
 There is no “pill” to cure a virus,
only the body can cure itself
– Bacteria:
 Either destroy tissue or release
poisonous toxins within your
body causing illness
 You can take antibiotics to cure
yourself of a bacterial infection
Flu virus
Agents of Disease

Protists – single-celled animals
– Protists often have a complex
lifecycle where they take a couple of
forms before infecting humans
– Malaria attacks human red blood
cells!

Worms – the “tropical” parasite
– Flatworms and roundworms are the
cause of many diseases and severe
discomfort
– Ascaris is a dangerous and common
roundworm while tapeworms are
common flatworms
Disease Transmission

How do you get sick ?
– What are three ways you
can acquire a disease?

What are the ways to
prevent disease?
– Name three things you can
do daily to prevent catching
a sickness.
Your Immune System

The function of your immune
system is to fight infection through
the production of cells that
inactivate foreign substances or
cells

There are two types of defenses:
– Non-specific defenses protect against
all pathogens equally (the skin is a
non-specific defense )
– Specific defenses act like “special
soldiers” that are designed to kill a
certain type of pathogen (these are the
host of white blood cells and other
disease fighting cells in your body)
The Immune System

Nonspecific Defense – your “general” defense
system against pathogens
– The skin is the most important line of defense
against nearly all pathogens
 The skin is capable of secretions such as oil, mucus,
saliva, and tears that create an intolerable
environment for many pathogens
 Sweat is also a great defense against pathogens!
Skin Structure