B2 - Keeping Healthy

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Flashcards by franimal, updated more than 1 year ago
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Cambridge IGCSE Biology Flashcards on B2 - Keeping Healthy, created by franimal on 10/26/2013.

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Question Answer
What is an infectious disease? One that can be passed to another person, such as the flu.
What are microorganisms? A living organism that can only be seen through a microscope.
In good conditions how often can bacteria reproduce? Once every twenty minutes.
What three things are needed for bacteria to live? Warmth, nutrients, moisture
Describe how antibodies work. Produced by white blood cells they latch onto foreign antigen markers and clump them together so other white blood cells can digest them.
Why are we sometimes ill for days then? Antibodies have to match antigens. The body produces different antibodies until there's a match - then it makes millions of the one that works.
Why do we only catch chickenpox once? Memory cells live on in the blood stream, carrying the antibody that matches the chickenpox antigen.
Why do we catch so many colds then? The cold virus is actually hundreds of different viruses that mutate regularly. The old antibodies don't work on the new cold.
How does a vaccine work? It contains dead or inactive microorganisms that the body produces antibodies against. Memory cells stick around, so if you meet the real disease, you destroy it quickly.
Why do vaccine rates have to be almost 100% to be effective? The more people without the vaccine the more chance they'll meet someone who's infected, and the more chance it'll spread.
Why do people not have vaccines? They worry about the side effects, such as allergic reactions. They believe since everyone else has the vaccine, they don't need it.
Why are vaccines not compulsory? The government doesn't believe people should be forced to if they don't want to or if they think it dangerous.
Penicillin can be found in mouldy bread. Why is this? Bacteria and fungi produce antibodies to kill other microorganisms. Penicillin is one of these.
What is an antibiotic? A drug that kills bacteria or fungi.
Why do we have superbugs? Bacteria mutates into a superbug. Antibiotics kill most of the bacteria so the patient stops taking the drugs. The new superdrug reproduces quickly.
Why are superbugs so dangerous? They're resistant to antibiotics, and so there's nothing doctors can do. People die and become disabled because of superbugs.
Describe stage one of testing new drugs. Early tests are done on human cells to get a rough idea of the effect. This is called in vitro tests.
Describe stage 2 of testing for new drugs. The drugs are tested on animals, known as in vivo testing. This is very controversial.
Describe stage 3 of trials for new drugs. Human or clinical trials, first on healthy volunteers and then on patients.
What is a placebo and a control group? A control group is a group of people who take part in a clinical trial but are given a placebo, a drug that has no effect.
There are three types of clinical trial. Describe them. Double-blind trial - neither Doctor nor patient knows who's in the control group. Blind trial - the doctor knows. Open label trial - everyone knows.
When are open-label trials used? If the patient is near death with no hope of recovery, side effects hardly matter. No placebo's are used.
Describe the arteries. Takes blood away from the heart. Has thick outer wall and can withstand the high pressure caused by the pumping heart.
Describe veins. They bring blood back to the heart, and have thin walls that can squish blood back to the heart. Small valves stop the blood flowing backwards.
Describe capillaries. Walls one cell thick, they allow oxygen and food to diffuse to cells, and waste products back in.
What is most common cause of a heart attack? Fat building up in coronary arteries, blocking the passage of blood to the heart. Without energy the heart can't pump.
What factors cause heart disease? Name three. Fatty foods, high salt intake, genes, smoking, lack of exercise - all of these are risk factors.
What are lifestyle diseases? Diseases such as lung cancer and heart disease, caused not by infections or inheritance but the unhealthy way we live.
What is blood pressure and what is it used for? Blood pressure measurements record the pressure of the blood on the walls of the artery. A warning sign of heart disease.
What does homeostasis do? Keep the correct level of water, salt and nutrients, and rid the body of waste products.
All control systems have what three things? A receptor to detect change or stimuli, a processing centre to receive the info and decide a response and an effector that does the responding.
What is negative feedback? When there's a change in the system, an action occurs that reverses this change.
What does water homeostasis do to control water levels? Controls water input (makes you thirsty) and output (urea, sweating).
What are the two jobs of the kidneys? Water homeostasis and excretion. The kidneys control the water balance of the body.
If you have only a little water in your body, what do the kidneys do? Make a smaller volume of urine (the water bit) with the same amount of waste (urea). The urine is more concentrated.
If the body has only a little water, what do the kidneys do? Reabsorb a lot of the water, sending it back to the bloodstream.
What's the effect of alcohol on urine? Urine becomes more dilute, and people become very dehydrated.
What effect does the drug Ecstasy have on homeostasis? Makes it very, very concentrated. It also makes you overheat, so you drink more. This can make you 'drown'.
How do the kidneys know when to produce concentrated urine? The brain releases ADH, a hormone which tells the kidneys to reabsorb more water.
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