Please enable JavaScript.
Coggle requires JavaScript to display documents.
B3 (Pathogens and disease (Pathogens are microorganisms - such as bacteria…
B3
Pathogens and disease
-
Bacteria release toxins, and viruses damage our cells
White blood cells can ingest and destroy pathogens by producing antibodies that destroy the infectious microorganisms, and antitoxins to neutralise toxins created as a by-product.
-
-
They come in many shapes and sizes, but even the largest are only 10 micrometres long - that's 10 millionths of a metre.
Bacteria are living cells and, in favourable conditions, can multiply rapidly
Once inside the body, they release poisons or toxins that make us feel ill
Malaria
Malaria is a disease caused by a protozoan, a type of single-celled organism.
-
-
Organisms that spread disease, rather than causing it themselves, are called vectors
-
Defence Systems
The body has several defences against pathogens so that we do not fall ill with the diseases they cause.
Skin
The skin covers the whole body. It protects the body from physical damage, microbe infection and dehydration. Its dry, dead outer cells are difficult for microbes to penetrate, and the sebaceous glands produce oils that help kill microbes.
Blood clotting
microorganisms get into the body through a cut in the skin, the most important thing to do is close the wound quickly so that no more microorganisms can enter. A scab does just that. The blood contains tiny structures called platelets, and a protein called fibrin. A scab is basically platelets stuck in a fibrin mesh.
Mucus
The respiratory system is protected in several ways. Nasal hairs keep out dust and larger microorganisms. Sticky mucus traps dust and microbes, which are then carried away by cilia. These are tiny hairs on the cells that line the respiratory system.
Stomach acid
Hydrochloric acid in the stomach kills harmful microorganisms that might be in the food or drink that we swallow.
Drug Testing
Drugs are substances that cause changes to the body. Antibiotics are drugs that kill bacteria, but not viruses. Antivirals are drugs that prevent viruses reproducing.
New medical drugs have to be tested to ensure that they work, and are safe, before they can be prescribed. There are three main stages of testing.
1.The drugs are tested using computer models and human cells grown in a laboratory. Many substances fail this test because they damage cells or do not seem to work.
2.Drugs that pass the first stage are tested on animals. In the UK, new medicines have to undergo these tests. But it is illegal to test cosmetics and tobacco products on animals. A typical test involves giving a known amount of a substance to the animals, then monitoring them carefully for any side-effects.
Drugs that have passed animal tests are used in clinical trials. They are tested on healthy volunteers to check that they are safe. Very low doses of the drug are given to begin with. If there are no problems, further clinical trials are done to find the optimum dose for the drug.
Vaccinations
Vaccination causes the body to produce enough white blood cells to protect itself against a pathogen.
Antibiotics are effective against bacteria, but not against viruses.
Some strains of bacteria are resistant to antibiotics. So people can be immunised against a pathogen through vaccination.
-
-
-