Infection and Response pt2


Preventing Spread of disease

1. Being hygienic
Using simple hygiene measures can prevent the spread of diseases. E.g. washing hands thoroughly before preparing food, or after sneezing can stop you infecting another person.

2. Destroying vectors
By getting rid of the organisms that spread disease, you can prevent the disease from being passed on. Vectors that are insects can be killed using insecticides or by destroying their habitat so that they can no longer breed.

3. Isolating infected individuals
If you isolate someone who has a communicable disease, it prevents them from passing it on.

4. Vaccination
Vaccinating people and animals prevents them from being infected and then pass it on to someone else.

Fighting disease

The human body has a defence system to help fight disease:

  • The skin
  • Hair and mucus in the nose
  • The trachea and bronchi secrete mucus
  • The trachea and bronchi are lined with cilia - waft the mucus up to the back of the throat.
  • The stomach produces hydrochloric acid.

Immune system fighting disease

If the pathogens get into the body, then the immune system kicks in. The white blood cells patrol the body looking out for microbes. It has three stages of attack:

1. Consuming the microbes
White blood cells engulf foreign cells and digest them - called phagocytosis

2. Producing Antibodies
Every pathogen has unique molecules on its surface. When some types of white blood cells come across a foreign antigen, they start to produce proteins called antibodies to lock on the invading cells so they can be destroyed by other white blood cells. Antibodies are rapidly produced and carried around the body. If the person is infected by the same pathogen again the white blood cells will rapidly produce the antibodies to kill it - the person is naturally immune to that pathogen.

Fighting disease - Vaccination

Vaccinations involve injecting small amounts of dead or inactive pathogens. These carry antigens, which cause your body to produce antibodies to attack them - even though the pathogen is harmless. If live pathogens then enter the body, the white blood cells can quickly mass-produce antibodies.

1. Vaccines have helped control lots of communicable diseases that were once common.
2. Big outbreaks of disease can be prevented if a large percentage of the population is vaccinated.

1. Vaccines don't always work.
2. Can sometimes have a bad reaction.

Fighting disease - Drugs

Painkillers: Drugs that relieve pain. However, don't actually tackle the cause of the disease or kill pathogens, they just help reduce the symptoms.

Antibiotics: These actually kill the bacteria causing the problem without killing your own body cells.

Antibiotics don't destroy viruses as they reproduce inside the cells where the antibiotics can't reach them. Bacteria can mutate and become resistant to antibiotics.

Many drugs originally came from plants. Plants produce a variety of chemicals to defend against pests and pathogens.

Aspirin: Chemical found in willow
Digitalis: Chemical found in foxgloves

Some are extracted from micro-organisms:
Penicillin: From mould

Developing drugs

Three main…


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