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Infections are caused by Microorganisms (MOs) that invade the body.
MOs are viruses, bacteria and fungi
When the disease MOs get inside the body, they reproduce very quickly. This causes Symptoms
Symptoms can be caused by the damage done to your cells when MOs reproduce or by the poison made by the MOs.
Microorganisms are very small, to see bacteria you need a microscope and viruses are even smaller. They are measured in nanometres. 1nm : 1/1000000 mm
You always breath in or touch billions of MOs but you mostly stay healthy, this is because most MOs do not cause human diseases and your body has barriers to keep MOs out.
Natural Barriers: Your skin produces chemicals that make it hard for MOs to grow; chemicals in tears destroy MOs ; if MOs get in through your mouth, acid in the stomach destroys most of them; the skin is a physical barrier to MOs
Bacteria can double every 20 minutes if kept in the correct condition (e.g your skin)
Extra blood gets sent to the area, so the white blood cells can surround and digest the bacteria. The worn-out white blood cells, dead bacteria and broken cells collect together and create pus.
The parts of your body that fight the infections are called your IMMUNE SYSTEM. White blood cells are an important part of your immune system.
The main parts of your immune system is: tonsils and adenoids; thymus; lymph nodes; spleen; lymph vessels; bone marrow.
Antibiotics are chemicals which kill off bacteria and fungi
There are correlations between taking a course of antibiotics and developing thrush.
Everybody needs antibodies - not antibiotics
All cells have antigen markers on the outside, these are unique to that type of cell.
White blood cells make things called antibodies, which stick to the foreign antigen markers. Only the correct shape antibody can stick to that MO.
Other white blood cells than digest any cells that the antibodies stick to.
The antigens on every MO is different, so your body has to make a new type of antibody each time your body is infected, this takes a few days which is why you get ill again.
Once your body has made the antibody, it is not forgotten as some of the white blood cells stay in your blood, so if the same MOs invade again, these white blood cells can reproduce very quickly, destroying the antigen before it infects you. So you are IMMUNE to that disease.
There are hundreds of different cold viruses, so every cold you catch is made by a different antigen, so you need to create new antibodies each time. So we suffer the symptoms of a cold all over again.
Vaccinations insert safe MOs into your blood stream, this kick-starts your body into making antibodies to destroy the virus, making you immune without having to catch the illness first.
As HIV mutates very quickly, there is no vaccine against it. The AIDS virus damages the immune system itself, this makes the immune system very poor at fighting of other illnesses that a healthy person would fight off very easily.
An influenza (flu) vaccine has to be produced every year as it reproduces very quickly and has a high mutation rate, which means that a small change happens to the DNA, so the antibodies are helpless about fighting against the antigens and the virus.
The government encourages vaccinations at an early age, as it means that less people will get will with a disease, for example the MMR jab, it protects against , measles, mumps and rubella. It can be fatal or leave people seriously injured.
The end of antibiotics?
To begin with, Penicillin was called a ‘wonder drug’ as before the 1940s, bacterial infections had killed millions of people every year.
Within 10 years one type of bacteria could no longer be killed by penicillin, as it had become resistant. New antibiotics were discovered, but soon the bacteria was resistant to them as well.
They became known as ‘superbugs’
Superbugs developed quickly as people took antibiotics when the didn’t need them or by not finishing their course of antibiotics.
Scientists cannot stop antibiotic resistant bacteria from developing, we can only hope that scientists can develop new antibiotics quick enough to keep us one step ahead of the bacteria.
Other than new drugs you can tackle the problem by: having better hygiene in hospitals to reduce the risk of infection; only prescribing antibiotics when a person really needs them; making sure people understand why it is important to finish all their antibiotics (unless side effects develop)
Where do new medicines come from?
Clinical and Human trials are very important when developing a new drug.
People are put randomly into groups, this is important as it means the results of the study are reliable
One group will be getting the drug, and the other group called a control group will get given a placebo
A double-blind trial is when neither the doctor or the patient know who has the placebo and who has the drug
A blind trial is when the doctors know who has the drug or not
An open trial is when both the doctor and the patient know who is taking the placebo and who is taking the drug.
A double-blind trial is said to be most reliable as no-one can fiddle with the results.
In rare cases, the drug is given to all cases, so there is no control group, as there is no treatment, and the patients are on the verge of death. It would be wrong not to offer the hope of the new drug to all the patients. Penicillin is one case where this happened.
Arteries take blood from the heart to your body. They have thick outer wall and a thick layer of muscle and elastic fibres.
Veins bring blood back to the heart. They have thin outer walls and a thin layer of muscle and elastic fibres.
If a coronary artery gets clogged up with fat build-up, then the heart muscle is starved of oxygen, the cells start to die. This is a heart attack.
In the UK 270 000 people have a heart attack every year, this is one every two minutes
Heart attacks in the UK is higher then non-industrialized countries, as people in the UK do less exercise, they mainly drive everywhere and have machines to do many jobs. A typical UK diet is also very high in fat.
Heart diseases are caused by lifestyle or you genes, but mainly by both.
To reduce the likelihood of an heart attack you should cut: down on fatty foods to lower blood cholesterol; not smoke; lose weight to help reduce blood pressure and the strain on your heart; take regular exercise to increase the fitness of the heart; reduce the amount of salt eaten to help lower blood pressure.
Diseases are caused by some microorganisms, and by a person’s lifestyle, for example, smoking and a poor diet
Natural barriers help to stop harmful microorganisms entering the body
These microorganisms may reproduce very quickly in good conditions, damaging cells or producing poisons which cause symptoms of disease
White blood cells are part of the immune system to fight infections
White blood cells can destroy microorganisms by digesting them or producing antibodies
Different antibodies are needed to fight every different microorganism
Once you have made one type of antibody you can make it again very quickly, so you are immune to that disease
Vaccines trigger the body to make antibodies before it is infected with a particular microorganism
No action can be completely safe, including vaccinations and other medical treatments
Why a very high percentage of people must be vaccinated to prevent an epidemic
New vaccines must be made against flu every year as the virus changes quickly
Why it is difficult to make a vaccine against the HIV virus
Antibiotics are chemicals that kill bacteria and fungi
An antibiotic may stop working because the bacteria or fungi has become resistant to it (superbug)
Antibiotic resistant microorganisms are made because of mutations in their genes
To slow down antibiotic resistant bacteria you should: only use antibiotics when needed; always finish the course
New drugs are tested for safety on how well the work on: human cells grown in the lab; animals; human volunteers; humans with that illness
How blind, double-blind and open trials are different
Heart muscle needs its own blood supply to bring food and oxygen to the cells
How the structure of arteries and veins is suited to the jobs they do
Fatty deposits in blood vessels supplying the heart can cause a heart attack
Heart disease is usually cause by lifestyle factors.
Infectious a disease which can be caught. The microorganisms which causes it is passed from one person to another through the air, through water, or by touch
Microorganisms (Mos) Living organisms that can only be seen by looking at them through a microscope. These include bacteria, viruses, and fungi.
Fungi a group of living things, including some microorganisms, that cannot make their own food
Viruses Microorganisms that can only live and reproduce when living inside cells.
Bacteria one type of single celled microorganism. They do not have a nucleus. Some bacteria may cause a disease
Symptoms what a person has when they have a particular illness, for example, a rash, high temperature or sore throat
Lifestyle diseases diseases which are not cause by microorganisms. They are triggered by other factors, for example, smoking, diet, lack of exercise
White blood cells cells in the blood that fight microorganisms. Some white blood cells digest invading microorganisms, others produce antibodies.
Digestion Breaks down large food molecules into smaller ones. This is needed so that they can pass into your blood
Immune system A group of organs and tissues in the body that fight infections
Antibiotics Drugs that kill or stop the growth of bacteria and fungi
Correlation A link between two things. For example if an outcome happens when a factor is present, but not when it is absent. Or if an outcome increase or decrease when a factor increases
Antibodies A group of proteins made by white blood cells to fight dangerous microorganisms. A different antibody is needed to fight each type of different microorganism. Antibodies bind to the surface of the microorganism, which triggers other white blood cells to digest them.
Antigens Proteins on the surface of a cell. A cell’s antigens are unique markers
Immune Able to react to an infection quickly, stopping the microorganisms before the can make you ill, usually because you’ve been exposed to them before
Mutation A change in the DNA of an organism. It alters a gene and may change the organism’s characteristics
Vaccinations Introducing to the body a chemical (a vaccine) used to make a person immune to a disease, A vaccine contains weakened or dead microorganisms, or parts of the microorganism, so that the body makes antibodies to the disease without being ill.
Influenza A disease caused by a particular virus. Symptoms include a very high temperature, sweating, aching muscle. In some cases ‘flu’ is fatal
AIDS Acquired Immune Deficiency Syndrome, a disease caused by the HIV virus. The body’s immune system is attacked by the virus and gradually become weakened
HIV Human Immunodeficiency Virus, the virus that causes AIDS
Penicillin An antibiotic made by one type of fungus
Antibiotic resistant Microorganisms that are not killed by antibiotics
Clinical trials When a new drug is tested on humans to find out whether it is safe and whether it works
Control In a clinical trial, the control group is people taking the currently used drug. The effects of the new drug can then be compared against this group
Blind trial A clinical trial in which the patient does not know whether they are taking the new drug, but their doctor does.
Placebo Occasionally used in clinical trials, this looks like the drug being tested, but actually contains no drug
Double-blind trial A clinical trial in which neither the doctor nor the patient knows whether the patient is taking the drug.
Heart attack The coronary arteries become blocked and the supply of blood to the heart muscle is interrupted, damaging the heart muscle
Arteries Blood vessels which carry the blood away from the heart
Veins Blood vessels which carry the blood towards the heart
Risk factors A variable linked to an increased risk of disease. Risk factors are linked to disease but may not be the cause of the disease.
Match Some studies into diseases compare two group of people. People in each group are chosen to be as similar as possible (matched) so that the results can be fairly compared