Fighting Disease

Biology Revision fighting disease etc.

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Fighting Disease

Two main types of Pathogen- Bacteria and Viruses

Bacteria- Are very small cells, which reproduce rapidly in the body.

               They make us feel by damaging cells and producing toxins.

Viruses- Are not cells, they are 1/110th the size of bacterium.

              They replicate by invading a human cell, and using the mechanics of the cell to make copies of tthemselves; then the cell full of the copies of viruses burst and infect the body.

              The cell damage is what makes us feel ill.

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Defence System

The first line of defence is the skin, hair and mucus in the respiratory tract.

To stop pathogens entering the body through cuts, small cells called platelets help clot the blood to seal the wound, to prevent pathogens entering the bloodstream.

White Blood Cells-White blood cells are our main line of defence.

They have three lines of attack - They engulf foreign cells and digest them.

Producing antibodies, every pathogen has a unique antigen on its surface . When a white blood cell encounters a pathogen, it produces unique antibbodies that lock on to the unique antigen on the surface of the pathogen; this then kills the pathogen. Each antibody is specific to a pathogen. The white blood cells remember each pathogen they encounter, so if the body encounters the same pathogen the white blood cells produce antibodies rapidly. meaning we are immune to that pathogen.

Producing antitoxins- The white blood cells produce antitoxins which counteract the toxins produced by bacteria.

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A vaccination is when a patient is injected with a small or inactive amount of a disease, this causes our white blood cells to produce specific antibodies to kill the disease. Cause our white blood cells can remember the specific antigen on the surface of the pathogen, this means if we are infected with that specific pathogen we are immune.

Some vaccinations wear off so boosters are given to increase the level of antibodies.

Advantages- Vaccinations have controlled the amount of infectous disease around.

                     Can prevent epidemics.

Disadvantages- Dont always work.

                          Bad reaction e.g swelling.

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Painkillers- Just relieve the effects of the symptoms.

Antibiotics prevent the growth of bacteria, without damaging the human cells. This kills the harmful bacteria. Different antibiotics kill different bacteria, so its important to use the correct antibiotic. Bacteria develop resistant strains, due to natural selection (a random mutation). Antibiotics then kill the non resistant strains, leaving a stronger bacteria which is resistant to the antibiotic. An example of this is the MRSA infection, MRSA is resistant to the methicillin antibiotic. To stop developing resistant strains of a bacteria doctors must not over prescribe antibiotics.

Investigating antibiotics- Microorganisms are grown in a culture medium, usually agar jelly containing carbohydrates, minerals, proteins and vitamins they need to grow.Hot agar jelly is poured into a petri dish.When the agar jelly is set, inoculating loops are used to transfer the microorganisms. The inoculating loop has to be sterilised (passed through a flame) to prevent cross contamination. The microorganisms then multiply.Paper disks are then soaked in antibiotics and placed on the jelly. Antibiotic resistant bacteria will carry on to grow around the paper disk, and the non resistant strains will die. The petri dish must have a lid to stop any microorganisms in the air contaminating the culture. At schools this culture must be kept at  25c, to stop harmful pathogens growing..

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Vaccinations Past and Future

Ignaz Semmelweise was working in a hospital in Vienna, when he noticed women were dying during childbirth. He believed that doctors were spreading disease by not washing their hands. He told doctors to use an antiseptic solution before delivering a baby. This resulted in the death rate decreasing from 12% to 2%.

The antiseptic solution killed the bacteria on thee doctors hands .

When Semmelweise died the doctors went back to their old ways and the death rate increased again. The doctors did not believe Semmelweise as he could not prove his theory.

Antibiotic resistant strains of bacteria are becoming more common due to doctors over prescribing antibiotics.

New dangers-

Bacteria- New strains, antibiotic resistant, may cause an epidemic.

Viruses- Hard to create vaccinations, due to their DNA changing meaning the specific antigen changing; Dangerous if the virus evolves.

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