B2 Keeping Healthy MicroorganismsInfectious a disease that can be caught. The microorganism that causes it is passed from one person to another through the air, through water, or by touch.Infections are caused by some microorganisms that invade the body. Microorganisms are viruses, bacteria, and fungi.When disease microorganisms get inside the body, they reproduce very quickly. This causes symptoms the ill feelings you get when you are unwell. Symptoms of infectious diseases can be caused by:1. Damage done to your cells when the microorganisms reproduce2. Poisons (toxins) made by microorganisms. People normally stay fit because: Most microorganisms do not cause human diseases. Your body has barriers that keep most microorganisms out.VirusBacteriumFungus

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Examples of diseases causedFlu, polio, common cold, AIDS, measlesTonsillitis, TB, plague, cystitis Athletes food, thrush, ringworm

Bacteria can reproduce rapidly inside the body

In ideal conditions in a sealed container bacteria cant keep up their fastest growth. Food starts to run out, or waste products kill them off. Lag phase growth gets goingLog phase fastest increase in growth, bacteria divide every 20 minuteStationary phase steady phase, growth of new bacteria equals death of old bacteria. Death phase more bacteria die that are made.

Immune SystemThe parts of the body that fight infections are called the immune system. White blood cells are an important part of your immune system. Antibiotics antimicrobial chemicals that kill bacteria and fungi but not VIRUSES!white blood cellsOne type of white blood cell makes antibodies (specialised proteins) to label microorganisms. Some antibodies remain in the blood as long-lived memory cells, ready to fight again. This means that the body reacts faster the second time the pathogen returns, the body destroys the invaders before you become ill - immune to the disease. A different type digests the pathogen (cause the disease) -phagocytes. All cells have antigen markers on the outside that are unique to that type of cell. The antigen markers on microorganisms are foreign to the body.

A person infected twice by a disease microorganism. Their white blood cells make antibodies much faster the second time.Phagocytosis

Summary of the role of white blood cells.

Viruses have high mutation (a change in the DNA of an organism. It alters a gene and may change the organisms characteristics) rate. The body will need to make a different antibody to fight a virus. VaccinationsVaccinations make use of the bodys own defence system. They kick-start your white blood cells into making antibodies. So you become immune to a disease without having to catch it first

Vaccines can improve the health by protecting you from disease. They are tested to make sure that they are safe to use. But it is never completely safe because people are genetically different, so they react differently. Doctors decide that a treatment is safe to use when: The risk of serious harmful effects is very small The benefits outweigh any riskTo stop large outbreaks of a disease, almost everyone in the population must be vaccinated. Why does the government encourage vaccinations? Almost nobody who has a vaccine notices any harmful effects Harmful effects from the MMR vaccine can be mild, or produce a serious allergic reaction Some children who catch measles are left severely disabled Measles can be fatalFor society as a whole, vaccination is the best choice. People often perceive the risk of vaccination to be greater than the risk of measles. SuperbugsMicroorganisms can be killed by antimicrobial chemicals. Some only inhibit their reproduction. The persons immune system destroys those remaining.A tiny change in one gene a mutation can turn a bacteria cell into a superbug. Just one superbug wont do much damage. But if it reproduces rapidly, it could produce a large population of bacteria, all resistant to an antibiotic.

The risk of antibiotic-resistant superbugs developing increases if:1. People taking antibiotics they dont really need2. People not finishing their course of antibiotics. If course is finished, all bacteria is killed. But if you stop taking the antibiotics because you feel better, the bacteria that survive will reproduce quickly because there is no competition for space and food from other bacteria. How can we stop the superbugs? Create new antibiotics Have better hygiene in hospitals to reduce the risk of infection Only prescribe antibiotics when a person really needs them Make sure people understand why it is important to finish all their antibiotics (unless side-effects develop)Drug development

StageTestingTo find out

One Drug is tested on human cells grown in the laboratory How safe the drug is for human cells How well it works against the disease

TwoDrug is tested on animals If the drug works as well in whole animals as it does on cells grown in the lab

ThreeDrug is tested on people (human trials or clinical trials) Gives scientists more data about the effectiveness and safety of the drug Carried on healthy volunteers checks safety Then tested on people with the disease to test for safer and effectiveness Long-term human trials ensure safety (no adverse side-effects) and that the drug works

Double blind trialsIt is important to be certain that a drug really does have positive effects, rather than people feeling better simply because they expect to feel better if they take a medicine. This is called theplacebo effect.Double blind trials aim to minimise the placebo effect. Some patients are given the drug while others are given a placebo (control group). A placebo is designed to appear exactly the same as the drug itself, but it does not actually contain any of the drug. The doctors and patients are not told who have received the drug and who have received the placebo until the trial is over.Taking placebo would not increase risk of disease but taking the new drug may bring other risks or increase chance of getting better. Many doctors do not like giving a placebo to patients with a disease because they feel the patient will not benefit from taking a fake drug and will not get better. They do not think this is fair to the patient.It may seem unfair to the control group because they may miss benefits of the new drug. If the trial shows that the risks are too great it will be stopped If the trial shows that the drug has benefits it will immediately be offered to the control groupBlind trialsDoctor is told which patients are being given the drug. This may be because they need to look very carefully for certain unwanted harmful effects. The patient does not know.Open-label trialsBoth the patient and doctor know the treatment. This happens when there is no other treatment and patients are so ill that doctors are sure they will not recover from the illness. No placebo. The drug may extend their lifespan or be a cure!CirculationThe heart is a bag of muscle. The heart is a double pump, tubes carry the blood around the circulatory system. How blood circulatesBlood enters the right-hand side of the heart from the body. It flows into the right lower chamber, which pumps it to the lungs to pick up oxygen. The blood then flows back into the upper chamber on the left-hand side of the heart, then into the left lower chamber. There it is pumped to the rest of the body to deliver oxygen. There are valves between the upper and lower chambers to make sure blood flows in the right direction. Heart AttackBlood brings oxygen and food to cells- makes energy. Without energy the heart would stop. So heart muscle cells must have their own blood supply. Sometimes fat can build in the coronary arteries. A blood clot can form on the fatty lumo. If this blocks an artery, some heart muscle is starved of oxygen. The cells start to die. This is an heart attack. Heart dieseas any illness of the heart. Heart attacks are not normaly caused by an infection. The genes, lifestyle, or most likely both, affect whether you suffer from a heart attack. There are may risk factors. The risk increase the more of these risk factors you are exposed to.

When arteries become clogged up with fatty deposits, it is more difficult for the blood to be pumped around the body. The heart has to work harder and will have to beat faster.Pulse rate measure how hard your heart is working. A more accurate way is taking your blood pressure (measures the pressure of the blood on the walls of the artery). Blood pressure is measured in millimeters of mercury,mmHg. There are two measurements: systolic pressure- the higher measurement when the heart beats, pushing blood through the arteries, and diastolic pressure- the lower measurement when the heart rests between beatsA young, fit person may have a blood pressure of about 120 over 70, which means their systolic pressure is 120 mmHg, and their diastolic pressure 70 mmHg.High blood pressure increases the risk of a heart attack. Narrowing of the arteries raises heart rate and blood pressure, and so do drugs (i.e. Ecstasy and cannabis). Lifestyle disease a disease that is not caused by microorganisms. They are triggered by other factors, i.e. smoking, lack of exercise, diet etc. It is harder to find the causes of lifestyle diseases, like heart disease.HOMEOSTASISKeeping conditions inside the body the same is homeostasis. For example, keeping the correct levels of water and salt, controlling the amounts of nutrients and getting rid of waste producs i.e. urea and carbon dioxide. All control systems have:1. receptor detects the change (stimuli)2. processing center receives the information and coordinates response3. effector produces an automatic responseNegative feedback any change in the system results in an action that reverses the change. Negative feedback systems reverse any change to the systems steady state. Changes are coordinated by both nervous and hormonal communication systems. Water Homeostasis keeping a steady water level (balancing water inputs and water outputs).Kidneys have two jobs:1. water homeostasis2. excretion- getting rid of toxic waste These two jobs are linked because you need water to flush out all the waste products. Getting the water level in cells right is important to maintain the correct chemical concentration levels for cell activity. The concentration of your blood plasma determines how much water your kidneys reabsorb, and how much you excrete in urine. The concentration of your blood can become higher than normal because of: excess sweating because of increased exercise levels not drinking enough water eating salty foodThese cases, increase ADH production, kidneys reabsorb more water, making less urine. DrugsAlcohol suppresses ADH production. This causes the kidneys to produce a greater volume of dilute urine. It can lead todehydration causing dizziness, headaches, and tiredness. Long-term dehydration can have effects on kidneys, liver, joints, and muscles. Severe dehydration can cause low blood pressure, seizures, increased heart rate, and loss of consciousness. Ecstasy increases ADH production. This causes the kidneys to reabsorb water, reducing the volume of urine. It can result in the body havingtoo muchwater (causing seizures-fatal, increase in blood pressure and heart rate, increasing the risk of a heart attack and brain damage) and affects the bodys temperature control.

Concentration of blood plasma falls- more waterConcentration of blood plasma rises- less water

Pituitary gland secretesLess ADHMore ADH

Kidney reabsorbsLessMore

Urine volumeDecreasesIncreases

Urine concentration DecreasesIncreases

Negative Feedback The moreconcentratedthe plasma, the more ADH is released into the blood. When the ADH reaches the kidneys, it causes them to reabsorb more water. This keeps more water in the body and produces concentrated urine. When the plasma is moredilute, less ADH is released into the bloodstream. This allows more water to leave the kidneys (kidneys reabsorb less), producing dilute urine.

Ideas about scienceRepeatsA scientist may take a set of measurements, or make some observations, and draw conclusions from them. If the scientist canrepeat this activity, and get similar data, this provides more evidence to support those conclusions. The conclusions are therefore more likely to be valid.Peer review Scientists report their work in scientific journals and at conferences. Before publication, the work is checked and evaluated by other experts. This process is known as 'peer review'.When scientists report their work, other scientists can see what they have done and try to repeat it. If these other scientists obtain similar data, it provides more evidence to support the conclusions that have been published.Scientific findings are only accepted once they have been evaluated critically by other scientists.CorrelationCorrelation does not prove a cause and the outcome might be caused by some other factor, e.g. ice-cream sales increase as hay fever increases, but ice-cream does no cause hay fever. Even when evidence exists that a factor is correlated to an outcome, scientists look for a causal mechanism. E.g. smoking increases the effect of heart disease because of the effects of nicotine on the body. Nicotine is the mechanisms.