DISEASE - WordPress.com · 2015-11-05 · AIM • Can use simple physical models to show how white...

H O W A R E D I S E A S E S S P R E A D ?

DISEASE

© cgrahamphysics.com 2015

Starter: How is your body like a castle?


Our skin is like the castle walls but microbes can enter through gaps in the defences


AIM

•  Can use simple physical models to show how white blood cells engulf microbes.

•  Can describe how microbes can get into the body and some of the body defenses which help to prevent this.

•  Can explain how white blood cells defend the body against invading microbes.


MICROBES CAN CAUSE DISEASE

The diseases caused by microbes, and their severity, depend on the type of microbe:

bacteria food poisoning

sore throats

tuberculosis (TB)

tetanus

cholera

typhoid

bacterial meningitis

influenza (flu)

mumps

chickenpox

smallpox

polio

HIV / AIDS

virus

viral meningitis

fungal sinusitis

athlete’s foot

fungi

onychomycosis (causes discoloured

toe nails)

DO YOU KNOW….

•  How can microbes and disease be spread? •  Where on your body can microbes infect?


HOW DOES DISEASE SPREAD?

Why do people do this? What are they trying to stop?


An agar plate showing a mixture of microbes growing after exposure to a dirty hand.


Bacteria on skin magnified thousands of times

Our skin is coated in microbes, but it stops them getting inside. The surface layers are dead and are continually replaced from below as they rub off. So how do they get in? © cgrahamphysics.com 2015

Clean skin has less than 10 000 bacteria per cm2… …and that’s not many. 200 million would fit in that space.

Life at your fingertips


It’s like 4 people sitting in Wembley Stadium.

A microbe desert


Bacteria reproduce fast if they get inside us, so we need good defenses. How could microbes get into Will’s body? What defenses does Will have?

Defenses

*Label the diagram to show how microbes could enter the body


TASK

•  Label the diagram showing what defences the body has to stop microbes getting in


HOW DO MICROBES ENTER THE BODY?

eyes

nose

genitals

skin

ears

mouth

cuts

Microbes can enter the body in many different places:

Stomach acid destroys most of the microbes in food… …but a few may get through if you swallow enough contaminated food.

Defenses


Clots form fast to cover cuts… ..but a few microbes can dissolve their way in.

Defenses


Mucus traps microbes in your lungs, and cilia sweep them out… …but some microbes get past them.

Defenses


THE BODY’S DEFENCES


These defences are not perfect – we need a second line of defence.


These microbes got in through Will’s cut. Left unchecked they will reproduce rapidly and fill his blood and tissues with toxins. How can Will’s immune system stop them?

Destroying invaders


It looks yellow on the image, but this is a white blood cell. What is it doing?

Destroying invaders


Once the bacteria are inside the white blood cell, enzymes destroy them. The white cells eventually die and get broken down. The broken down cells ooze out of wounds as pus.

Destroying invaders


White blood cells killing bacteria


WHAT DO WHITE BLOOD CELLS DO? If harmful microbes enter the body the immune system produces white blood cells to help defend it from microbes. Some white blood cells can destroy microbes by engulfing them.

Some white blood cells are able to produce chemicals called antibodies. These pair with matching antigens on the surfaces of microbes and so help the white blood cells to engulf microbes.

white blood cell

bacteria

antigen

ENGULFING MICROBES - WHAT’S THE ORDER?


ENGULFING MICROBES - WHAT HAPPENS?


Other types of white blood cells defend the body in different ways. They make chemicals called antibodies which stick to microbes and make them easier to destroy. They work against both bacteria and viruses. This is the body’s third line of defence.

Destroying invaders


White blood cells produce antibodies


These Y-shaped particles are models of antibodies. Some antibodies destroy bacteria others just make it easier for white cells to engulf them. Each type of microbe needs a different antibody, so they aren’t made in advance. When a new microbe invades the body, it takes a couple of days to make them.

Destroying invaders


Once a white blood cell has made antibodies, it never forgets its target. If that microbe returns, it makes antibodies straight away. So the microbes are destroyed before they can reproduce and cause disease… ...which makes you immune to that disease.

Destroying invaders


PREVENTING THE SPREAD OF DISEASE

There are several methods that can help reduce the spread of disease:

l  disinfecting surfaces

l  disinfecting skin using antiseptics

l  sterilizing equipment

l  using food preservatives in food

l  personal hygiene.

The spread of disease can also be reduced by vaccinating the population and using antibiotics.

WHAT ARE ANTIBIOTICS?

Antibiotics are chemicals used to treat bacterial infections. These chemicals kill or stop the growth of bacteria.

However, some types of bacteria are no longer affected by certain antibiotics – this is called antibiotic resistance.

This can be a problem as without effective antibiotics some people might not be able to fight the infection themselves.


WHAT ARE VACCINES?

Vaccines contain dead or weakened strains of the harmful microbe that causes the disease.

Vaccines can protect people from diseases, such as measles.

Why is it important that everyone is vaccinated?

This stimulates the immune system. If the person comes into contact with the microbe again the immune system can destroy it quickly and effectively.


WHY DO WE NEED TO HAVE VACCINATIONS?


Paul is beginning to feel ill.

Bacteria have infected his throat.

He is under a lot of stress and it has weakened his immunity.

Destroying invaders


Explain what is happening in each part of the graph.

Destroying invaders


Destroying invaders

What would help Paul get better quicker?


Destroying invaders

Why doesn’t Paul notice the second infection?


Asha has AIDs. She gets a lot of infections and feels tired all the time. This white cell used to help Asha make antibodies… ..but HIV particles have stopped it working… ..so her immune system cannot protect her.

Destroying invaders


In HIV sufferers white blood cells are infected and destroyed. This stops their immune system from working

properly.

HIV

White blood cell


You are a microbe. You want to get into Will’s body. Are you lucky or unlucky?

Lucky or unlucky?


You’re with a group of salmonella bacteria in the middle of a burger. What happens next?

Lucky or unlucky?


You’re are a cold virus. You drifted into Will’s nose as he breathed. What happens next?

Lucky or unlucky?


You are a tetanus bacterium in the mud on Will’s football. He has a cut on his finger and he has just picked up the football. What happens next?

Lucky or unlucky?


Support I can use simple physical models to show how white blood cells engulf microbes. Support I can describe how microbes can get into the body and some of the body defenses which help to prevent this. Developing I can explain how white blood cells defend the body against invading microbes. Independent I can use models presented as graphs to explain why it takes time to recover from the infection. Applying I can make connections between bacterial reproduction and antibody manufacture to explain immunity to further infection by a microbe.


PRODUCING ANTIBODIES

Step 1: The white blood cell “sees” the antigen (microbe)

Step 2: The cell produces antibodies to “fit” the antigen

Step 3: The antibodies fit onto the antigens and cause them to “clump”

Step 4: The antigens are “eaten” by the white blood cells

You’re going down


MATCHING MICROBES AND ANTIBODIES


MULTIPLE-CHOICE QUIZ

DISEASE - WordPress.com · 2015-11-05 · AIM • Can use simple physical models to show how white...

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