Download 4.2 defence mechanisms - science

GCSE Core Science
Human Biology
Key Words
WHITE BLOOD CELL,
INGEST, ANTIBODY, ANTITOXIN
GCSE Core Science
Objectives
By the end of the lesson I will:
•Know a PATHOGEN is a microorganism that causes an infectious
disease
•Know pathogens reproduce before
they make enough toxins to make you
feel ill
•Know that the best way to protect
ourselves is through the first line of
defence (the skin) and not let any
pathogens into the body
• Identify the second and third line of
defence
•Know what the white blood cells do to
protect your body
Human Biology
GCSE Core Science
Starter
Human Biology
There are four main ways in which you can get sick
1. Droplet infection – When a sick person coughs,
sneezes or talks too close to you
2. Direct contact – through skin, kissing or other sexual
contact
3. Contaminated food and/or drink – ingestion
4. Break in the skin – scratches or needle punctures
I know HOW TO USE ASEPTIC TECHNIQUE
GCSE Core Science
How do we effect change?
Human Biology
We are going to grow some yeast…..
AND THEN KILL IT!
1. Using ASEPTIC TECHNIQUE infect a petri dish with a
yeast solution.
2. Wait for the solution to slightly dry (perhaps 1hour)
3. Place a full drop of antiseptic onto the centre of the agar
plate.
4. Incubate for 24-48hours.
WHAT ARE YOU TRYING TO FIND OUT?
WHAT DO YOU EXPECT TO FIND OUT?
GCSE Core Science
How many lines
of defence do
you have in
your body?
Lines of defence
Human Biology
1) Skin: Provides both a
physical (protective layer
that completely wraps
around the body, shielding
blood vessels, nerves,
muscles, organs, and bones)
and a chemical barrier
(When there is a cut or tear
in the surface of the skin
pathogens can breach the
bodies defence and so
glands beneath the skin
produce an enzyme that
helps kill bacteria)
GCSE Core Science
Lines of defence
Human Biology
2) Mucous membranes, stomach acid, cilia:
• Mucous membranes, produce a sticky substance that traps
irritants that enter through the nose.
•
Structures like tiny hairs, called cilia, line the body's airways and
constantly wave foreign particles and mucus away from the lungs
to where they can be swallowed safely.
•
Most harmful microbes that make it to the stomach are destroyed
by stomach acids.
•
Tears and saliva both contain enzymes that destroy invaders.
•
The brain-blood barrier, a specialized "filter" that surrounds the
brain and spinal cord and acts as a physical barrier to keep out
proteins, toxins, and most microbes, while letting in glucose, the
source of the brain's nutrients.
GCSE Core Science
Lines of defence
Human Biology
3) Lymphatic system (white blood cells): You have white
blood cells in your body that defend it by
•Ingesting pathogens and destroying them (Never EVER say
they eat the pathogen as this is WRONG. The only correct word
is INGEST)
•Some white blood cells produce antibodies that recognise the
antigens that are on the surface of the pathogen. The
anitbodies of the white blood cell then bind with the antigens of
the pathogen which destroys the pathogen or tags it for
ingesting by another white blood cell. Each antigen is different
and so your body needs to produce an antibody to match each
antigen.
•Some white blood cells produce antitoxins to counteract the
toxins produced by some bacteria. The toxins are bound and
destroyed.
GCSE Core Science
Human Biology
GCSE Core Science
Lines of defence
Human Biology
GCSE Core Science
Human Biology
physical and
chemical barriers
most
essential
non-specific
defences
inflammation
to attract white
cells into tissues
pathogen-specific most
controllable
defences
ingestion of
bacteria by
white cells
involves
antibodies and
T- and B-cells
GCSE Core Science
Delayed response
Human Biology
The B-lymphocyte that produces the correct antibody for the
antigen begins dividing to produce many more antibodyproducing cells.
It takes a few days to produce enough
antibodies to destroy the pathogen. This
means there is delay between infection
and the person beginning to feel better.
Once a pathogen has been destroyed, a few memory cells
remain. These recognize the pathogen if it re-infects, and
make the immune response much quicker and more effective.
This is called active immunity.
GCSE Core Science
Research
Human Biology
Use pages 64-65 to complete the
Provided worksheets on
‘White Blood Cells’
OR
‘Infection’
Miss will pair you with someone who
you will work with. You will
complete a different sheet each.
You will then have to
teach what you have
learnt to your
partner!
GCSE Core Science
Objectives
By the end of the lesson I will:
•Know a PATHOGEN is a microorganism that causes an infectious
disease
•Know pathogens reproduce before
they make enough toxins to make you
feel ill
•Know that the best way to protect
ourselves is through the first line of
defence (the skin) and not let any
pathogens into the body
• Identify the second and third line of
defence
•Know what the white blood cells do to
protect your body
Human Biology