Transcript Slide 1

This is in addition to your
revision!
This is a big topic
You have been warned
Microorganisms are Very Small
Biggest
FUNGI
Smallest
BACTERIA
VIRUSES
(On a needle)
When millions of
them grow in one
place then you
can see them
Colonies of Bacteria
and Fungi growing
in an agar plate.
Agar jelly is their
food.
Some microorganisms are Pathogenic
Pathogenic means they cause diseases
• Athletes foot, Thrush
• Smallpox , Flu
• Tuberculosis, Cholera
Fungal
Viral
Bacterial
If you are infected with one of
these you will show symptoms:
E.g. runny nose, high temp,
spots, sneezing etc.
Some diseases are caused by the things we do:
Over eating, cigarettes, alcohol, drugs
These are called LIFESTYLE diseases:
Obesity, Heart disease, lung cancer.
Remember: YOU can change your lifestyle
How do bacteria Grow?
Real Fast !!!
Just give them: WARMTH – FOOD – WATER (Not O2)
1 cell – 2 – 4 – 8 – 16 – 32 – 64 – 128 – 256 – 512 - In just 3 Hrs
------------ And it looks like this ------------Growth rate = death rate
(running out of food or too much
excretory products)
Getting used to
their Petri dish
food supply
Rapid growth
Lots of food,
water, warmth
and space
Time
More dying
than growing
Antimicrobials
Any substance that inhibits (slows or stops) the growth of bacteria, fungi or
bacteria,
Eg: antibiotics, vaccines, antiseptics
So why don’t we get ill all the time?
Skin, antiseptic tears, mucus in our nose
and windpipe, stomach acid, hairs &
earwax all stop them getting in to our
body.
And if that doesn’t stop them –
White Blood Cells from our
immune system will:
That’s me, the white one
MRSA
These are all the exactly the same thing,
NASTY bacteria that cannot be killed by
Antibiotics
Why are they so common?
People take AB’s for colds & flu
People don’t finish the course
click for
video
Final resistant
population
It’s just normal variation, natural selection & mutations
ALMOST FORGOT: Antibiotics don’t kill VIRUSES
The Immune System
‘’ It’s me your friendly
neighbourhood white blood cell
again. This is how we kill microbes’’
1. We find them, surround them and
digest them, BURP! (phagocytosis)
AND
2. Some of us make chemicals
called antibodies that stick to
microbes. Each microbe has
antigens ( molecules on their
surface). Antibodies recognise the
shape of each different antigen &
stick to them. Death follows
Arghhh
Foreign blood cell
being attacked
‘’OK, but what if I’m too sick and my
immune system isn’t stopping them’’?
• If it’s a bacteria take a course of antibiotics –
• And don’t stop just because you feel better
• And you might experience side effects, even
death!!
• And, they might kill all your good microbes.
‘’SO WHAT, THE ONLY GOOD MICROBE IS A DEAD MICROBE’’
If a fungus is left it will have as much food, space and
water as it wants. ‘’And what next’’? GROWTH
-- Itch Itch Scratch Scratch -And this arrow is NOT
pointing at your feet
Better get the bio
yoghurt out
‘’Ahh, that’s better’’
‘’I’ve had chickenpox, why can’t I catch it again’’?
‘’Because your now immune to it silly’’
1. First Infection How does that happen?
Antibodies attach to nasty
microbes & kill them
WBC make
antibodies
2. If there is a second similar Infection
Me
again
Yeh and I
remember
you ‘cos I’m
a memory
cell
The differences between 1 & 2 are:
1. Antibodies are made slowly and you may
feel ill before all the MO’s are all killed
2. Antibodies are made really fast and you
don’t get ill at all. You are IMMUNE
I think I’m
dying!
Once killed, the WBC’s
become MEMORY CELLS
which remember the
microbes antigens
Zap Bang Wallop!
I’m dead!
This is what an Immune Response looks like
Memory cells
become active
Antibody
numbers
Memory cells
created here
First encounter
with pathogen
Second
encounter with
pathogen
Pathogen
rapidly
destroyed
Vaccines & Vaccinations
• A vaccination make you immune from a disease
• A vaccine contains either:
• A dead MO, parts of a MO, or a weakened MO
WHY?
• They ALL contain the MO’s antigens/markers
• They all lead to memory cells being made
Some Problem Microbes
• Flu Virus – mutates rapidly (changes it’s antigens)
• HIV virus – Attacks the immune system
and also mutates rapidly…very NASTY
MO
MO
Original antigens
New antigens
Testing Drugs
• Drugs are tested for safety (side effects) and effectiveness (does it work?)
• Testing involves 3 stages:
• On human cells (relatively cheap & quick and may indicate how safe it is)
• On animals (gives information on safety and effectiveness)
• On people in a clinical trial (gives info on dosage, side effects)
Issues with Drug Tests
• Can take 10 years to get a new drug to market
• VERY expensive: staff & clinical trials, salaries,
looking after animals, hospital & lab costs, security
• Ethical issues with using live animals
• Ethical issues with testing it on humans,
especially if a placebo is involved.
• Must be approved & licensed by the government
Can you describe what's happening in the picture?
When you have written your 5 descriptions, check your
answers on the next slide. No peeking!
5. what about memory cells?
1.
4
2
3
No Peeking until you have completed the first
slide
1. Vaccine containing
weakened,
dead pathogen or parts of it.
Each of these has the
pathogens antigens (markers).
All induce an immune response
4. Antibodies attach to
the pathogen’s antigens
(markers). They
neutralise the pathogen
or attract phagocytotic
WB Cells
2. Sometimes
there are side
effects
3.White Blood cells
produce antigens which
match the pathogens
antigens (markers)
5. Special White Blood Cells called memory cells are
produced so when you come in contact with the real
pathogen they REMEMBER IT and produce antibodies
SO FAST you don’t get sick; this is immunity.
Clinical or Human Trials
• Open label: Everyone
knows who has the drug
• Blind: Only the doctors
know who has the drug
• Double Blind: No one
knows who has the drug
Increasingly more
reliable results
(less risk of bias)
Drug Safety
• Taking any drug involves some risk & we all react
differently cos we are all genetically different
• Side effects can be minor, severe or even cause death
• Vaccinations have risks too, but the risk to the individual is
outweighed by the benefits to the rest of the population.
• If 95% of the public are vaccinated it stops a disease from
spreading and can lead to its eradication (disappearance)
•Smallpox has been completely eradicated over the whole world
Why Do Arteries and Veins Look Different?
thick layer of
muscle and
elastic fibres
Arteries carry blood at HIGH
pressure, thick walls prevent
them bursting, elastic fibres
allow them to stretch and go
back to their normal shape
Veins carry blood at LOW
pressure so only thin walls
are needed. They also have
valves which prevent blood
moving backwards
Capillaries, tiny blood
vessels that carry oxygen &
food to cells & remove
carbon dioxide from cells
ARTERY
thick outer
layer
thin outer
wall
VEIN
thin layer of
muscle and
elastic fibres
Running a Clinical Trial
• Trials have to be designed scientifically to be fair & reliable tests
• Participants put in to two groups
• Participants chosen randomly (increases reliability)
• One group gets the drug the other no drug, (the control group)
• A control group allows the groups/drugs effect to be compared
• If it’s a totally new drug the control group has a placebo
• A placebo looks exactly like the real drug but contains no drug
• Placebos raise ethical issues; if the new drug may cure a serious
disease and does work, people in the control group may die
The Circulatory System
• The heart is made of muscle cells.
• Every cell needs oxygen and glucose to make energy (respiration)
• The blood transports oxygen and glucose to every cell
• Blood leaves the heart under high pressure and returns under low pressure
• Veins carry blood into the heart
• Arteries carry blood away from the heart
• Coronary arteries supply heart cells with blood
An incubator has to control a babies
temperature just like your body
Temperature
sensor
Thermostat
Set at 37oC
Heater
This is the control system sequence
Temperature drops below 37oC
Sensor detects drop & messages thermostat
Thermostat messages heater to switch on
Temperature rises to 37oC
Temperature rises above 37oC
Sensor detects the rise & messages thermostat
Thermostat messages heater to switch off
Temperature drops
And the cycle continues
A typical
homeostasis
graph
37oC
Bad Lifestyle = Increased Risk of a Heart
Attack
• Risk factors: Smoking, lack of exercise, high salt/fat diet & family history
1. Bad
lifestyle
2. Build up of
fat in artery
3. Blood flow is now
reduced to the heart
muscle cells
A heart attack
animation
4. Cells now
starved of oxygen
heart attack simple version
6. Heart attack
takes place
5. Heart muscle
cells begin to die
Water Control
Remember Water IN = Water OUT
IN: drinks, food, respiration
OUT: Urine, faeces, breathing, sweating
(exercise is dehydrating)
All of these effect the amount of water
in the blood plasma and the kidney
controls it.
Homeostasis & Control Systems
• Your body needs to keep conditions inside
your body the same - otherwise you will feel
ill & be ill
THIS IS CALLED HOMEOSTASIS
REMEMBER IT!
•
•
•
•
What needs to be kept under control?
Levels of: glucose, water, salt, urea, CO2 & O2
-Also: temperature, pH & blood pressure
The underlined ones are in this syllabus
Control System Terms/Sequence
•
•
•
•
•
Stimulus – A factor that changes (e.g. Temp rises)
Receptor (sensor) - Detects the change
Processing Centre – Decides the action to be taken
Effector – Produces the response
Response - The change produced (e.g. Temp
drops)
• Negative Feedback – Part of a control system that
reverses changes to bring them back to normal.
Allows a quicker response & keeps the value closer
to the normal value
• You should be able to recognise these in an incubator
and in the kidney/water control system
ADH, the Kidney& Water Control
Detected by
water receptors
in the
processing
centre (brain)
Pituitary
Gland Effector
Stimulus
(brings about
the response)
Response:
Less pee,
blood water
increases
Response:
More pee,
blood water
decreases
Stimulus
Detected by
water receptors
in the processing
centre (brain)
Pituitary
Gland
Effector
(brings
about the
response)
Learn all the key words and understand how the flow chart works
Drugs and ADH
Learn This
• Alcohol makes people pee a lot of dilute
urine by lowering ADH production
• They become dehydrated
•
•
•
•
Ecstasy does the opposite
Increases ADH production
Therefore, stops you peeing
So, ecstasy users should not drink too
much water, they will dilute their blood
too much and pass out. OR WORSE!!
AND
Don’t forget to do as many past
papers as you can.
Check your answers using the mark
schemes
And if you’re aiming for an A* or B
go through each line of the
syllabus/specification (find it on the OCR web
site)
Good Luck
Not Yet or not fully covered in
this resource
• Epidemiological Studies (disease causes and
their transmission)
• Correlations
• The scientific method
• Risks and benefits (to individuals and society)
• Ethics
AND FINALLY, THE LAST SLIDE