Vaccination Flashcards
What are pathogens?
Microorganisms, such as viruses or bacteria, that cause an infectious disease.
What are bacteria? (3 points)
Microscopic organisms, the largest are only 10 micrometres long. They are living cells and, in favourable conditions, can rapidly multiply. Once inside the body, they release poisons or toxins that make us feel ill.
What are some examples of diseases caused by bacteria? (5)
Food poisoning Cholera Typhoid Whooping cough Gonorrhoea
What is a virus? (6)
Viruses are many times smaller than bacteria, and are among the smallest organisms known. They consist of a fragment of genetic material inside a protective protein coat.
Viruses can only reproduce inside host cells, and they damage the cell when they do this. A virus can get inside a cell and, once there, take over and make hundreds of thousands of copies of itself. Eventually the virus copies fill the whole host cell and burst it open. The viruses are then passed out in the bloodstream, the airways, or by other routes.
What are some example of diseases caused by viruses? (7)
Influenza - flu Colds Measles Mumps Rubella Chicken pox AIDS
What are the functions of white blood cells? (3)
Ingest pathogens and destroy them
Produce antibodies to destroy pathogens
Produce antitoxins to neutralise the toxins released by pathogens
What are the two main groups of white blood cells?
Phagocytes (or macrophages) and lymphocytes
What do phagocytes do? (3)
They can easily pass through blood vessel walls into the surrounding tissue and move towards pathogens or toxins. They can then either ingest and absorb the pathogens or toxins or release an enzyme to destroy them.
Having absorbed a pathogen, the phagocytes may also send out chemical messages that help nearby lymphocytes to identify the type of antibody needed to neutralise them.
What is a toxin?
A type of natural poison produced by an organism, often as a form of protection.
What do lymphocytes do? (5)
Pathogens contain certain chemicals that are foreign to the body and are called antigens. Each lymphocyte carries a specific type of antibody - a protein that has a chemical ‘fit’ to a certain antigen. When a lymphocyte with the appropriate antibody meets the antigen, the lymphocyte reproduces quickly, and makes many copies of the antibody that neutralises the pathogen.
Lymphocytes may also release antitoxins that stick to the appropriate toxin and stop it damaging the body.
How can antibodies neutralise pathogens?
They bind to pathogens and damage or destroy them
They coat pathogens, clumping them together so that they are easily ingested by phagocytes
They bind to the pathogens and release chemical signals to attract more phagocytes
Vaccination involves putting a small amount of an inactive form of a pathogen, or dead pathogen, into the body. What different forms can vaccines contain? (4)
Live pathogens treated to make them harmless
Harmless fragments of the pathogen
Toxins produced by pathogens
Dead pathogens
What do the harmless forms of the pathogen in a vaccine act as, and what do they cause?
Antigens. When injected into the body, they stimulate white blood cells to produce antibodies against the pathogen.
Why aren’t vaccines harmful? (3)
Because the vaccine contains only a weakened or harmless version of a pathogen, the vaccinated person is not in danger of developing disease - although some people may suffer a mild reaction. If the person does get infected by the pathogen later, the required lymphocytes are able to reproduce rapidly and destroy it.
Describe how vaccination helps people to develop immunity to a disease. (6)
A dead or inactive form of the pathogen is injected into the body; this can also be fragmented, harmless parts, simply the toxin or the live pathogen treated to be harmless. Believing the body is infected, the immune system sends lymphocytes, a type of white blood cell, which releases antibodies that attack the pathogen’s antigens. These either destroy the pathogens, or clump them together and make it easier for them to be engulfed, or ingested, by phagocytes. As it is weak, the pathogen is easily destroyed, but the body stores a copy of the antibodies needed to fight the pathogen in ‘memory cells’. Now, if the body is infected with a life, harmful form of the pathogen it is easily recognised, and antibodies are produced much faster. This means the pathogen is destroyed before it harms the body.
