Transcript lesson 17: defence against disease learning

LESSON 17: DEFENCE AGAINST
DISEASE
STARTER ACTIVITY - 5,4,3,2,1:
Name………
• 5 places a micro-organism can enter the
body
• 4 ways our body prevents the entry of
micro-organisms
• 3 types of micro-organism.
• 2 diseases caused by a virus
• 1 meaning of a pathogen
LESSON 17: DEFENCE AGAINST
DISEASE
LEARNING OBJECTIVES:
• Explain that bacteria and viruses spread
rapidly and may produce toxins
• Describe how viruses damage cells
• Explain the different ways that white
blood cells fight infection
White blood cells
If viruses and bacteria do get into the body, it is
extremely likely that they will enter the blood
stream.
If this happens, the previous defence systems are
useless and so the body brings in its next line of
defence…
How do white cells attack micro-organisms?
White blood cells have 3 main methods of attacking
microbes:
1. Chemicals called Antibodies produced by White Blood
cells called Lymphocytes
2.Chemicals called Anti-toxins produced by White Blood
cells called Lymphocytes
3. Phagocytosis (eating) by White Blood cells called
Phagocytes
1. Releasing antibodies
Invading pathogen has antigens
on the surface
White blood cell
called LYMPHOCYTE
release a chemical
known as an antibody.
Once attached, the
antibodies can destroy
the microbe….. Or make
it more visible to be
eaten by the other type
of white blood cell
Antibodies released
to attack the
Antigens
Their shape is important
because it fits exactly
onto the antigen on the
microbe.
2. Producing antitoxins
bacterium
white blood cell
(Lymphocyte)
antitoxins
toxins
The Anti-toxin links to the toxin and neutralises its
effect.
The toxin is now harmless. This happens on a large scale
and reduces the effects of the infection.
As each pathogen has a differently shaped antigens…..
…..there are different white blood cells to produce
different antibodies and anti-toxins.
Antigens are
different shapes
For example….
In your body, there will be a specific
lymphocyte responsible for dealing with
virus that causes a sore throat…..
3. Phagocytosis
Some white blood cells (PHAGOCYTES) actually ingest
(eat) the microbes and then break them down once they
are inside the cell. The microbe is destroyed by powerful
digestive enzymes, which are released within the
cytoplasm of the white blood cell.
white
blood cell
microbe
The white blood cell
surrounds the microbe.
Digestive enzymes attack
the ingested microbe and
begin to break it down.
The blood
microbe
is destroyed.
Dead white
cells
chemicals that are
and The
pathogens
collectreleased
to form from
PUS the digested
microbe are used in other
parts of the cell.
Watch this animation
Active Teach
page 34, box C
Engulfing microbes - what’s the order?
11 of 44
© Boardworks Ltd 2004
Engulfing microbes - what happens?
12 of 44
© Boardworks Ltd 2004
ACTIVITY 3: WRITE THESE STATEMENTS AS A FLOW DIAGRAM
Your Task….
How WBC
fights microbe
Phagocytosis
Antibodies
Antitoxins
Description
Diagram
ACTIVITY 4: NATURAL IMMUNITY
“Once infected by a particular microbe, the body
stores levels of that specific antibody/antitoxin”.
Use the above statement to explain the following
facts:
1. If that microbe infects again, there is no need for
the body to spend time producing the specific white
blood cells to make the relevant antibody.
2. Humans tend to only suffer from certain diseases
once in their lifetimes.
REVIEW YOUR LEARNING:
Multiple choice questions
1) The outer body surface that acts
as a barrier to the entry of
microbes is...
A
B
C
D
hair.
skin.
clothing.
mucus.
2) A sticky substance is produced by the
breathing organs and it can help trap
microbes in the air you breathe in.
It is called...
A
B
C
D
gel.
bile.
mucus.
glue.
3) An acid in the stomach can help to kill
microbes that are accidentally eaten.
This acid is called...
A
B
C
D
hydrochloric acid.
nitric acid.
sulphuric acid.
carbonic acid.
4) The blood cells that will attempt to
destroy microbes that do gain entry to
our body are the...
A
B
C
D
red blood cells.
platelets.
white blood cells.
glandular cells.
5) What is happening in the diagram?
microbe
blood cell
A The white blood cell is about to bite the microbe.
B The red blood cell is about to ingest the microbe and
once the microbe has been ingested it will be
digested.
C The white blood cell is about to burst and release
digestive enzymes onto the microbe.
D The white blood cell is about to ingest the microbe
and once the microbe has been ingested it will be
digested.
Homelearning
Write a storyboard, describing how the
body reacts to an invading pathogen…..
Remember: use BBC bitesize to help…..