B2: Keeping Healthy

  • Created by: emmacram
  • Created on: 13-06-15 12:02


  • Organisms too small to see with the naked eye.
  • Include bacteria, viruses and fungi.
  • Can be beneficial to us or they can cause us harm.
  • Once inside the body, harmful microorganisms start to reproduce.
  • As they grow in number, they start to damage cells by bursting them (lysis).
  • Sometimes they produce toxins/poisons.
  • Symptoms of a disease appear when the damage of cells or amount of toxin reaches a certain level.
  • Human bod provides ideal conditions for microorganisms - water, oxygen, food, heat and pH levels.
  • When conditions are suitable microorganisms can reproduce as quickly as every 15 minutes, others can take days to divide.
  • This form of growth is known as exponential growth.
  • A growth curve shows the realistic stages of bacterial growth.
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Immune system

  • Body has immune systems that defend it against invading microorganisms.
  • Immune systems are layered - as each defence is compromised there is a new layer for the microorganisms to try to break through.
  • Microorganisms first have to breach the physical barriers like the skin which has to be cut to allow entry and sweat which was antimicrobial properties.
  • Microorganisms can also enter through the eye and the stomach.
  • When microorganisms breach the physical barrier, the immune system is activated.
  • White blood cells play a major role in this response such as the neutrophils and the B-cells.
  • A neutrophil moves around the bloodstream looking for microorganisms, engulfs them and digests them, destroying them.
  • A B-cell makes antibodies to combat infection, this leads to B-cells targeting the same organism if it invades again (a memory cell).
  • Unique markers made out of protein on the surface of microorganisms are called antigens.
  • The antibodies produced by B-cells are specific to a particular antigen (e.g. TB antibodies will not work with the antigens from cholera).
  • When microorganisms are identified by antibodies, other white blood cells consume them.
  • Producing antibodies enables the immune response to be rapid if the same microorganism infects the body again - protects the body and gives it immunity against that microorganism.
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  • Helps the body to develop long-term immunity against a disease by producing antibodies.
  • If body is re-infected by same microorganism, memory cells produce antibodies quickly so the microorganism is destroyed before damage is done.
  • Vaccination is done by: Injecting a vaccine of a dead or weakened form of the disease-causing microorganism - the antigens on the surface cause the white blood cells to produce specific antibodies. After the vaccine, memory cells remain in the body so if the disease-causing microorganism infects the body, the white blood cells can attack very quickly.
  • Vaccinations help prevent epidemics of disease.
  • All people react to vaccines in different ways and experience different side effects.
  • Most side effects are minor compared to the disease you are preventing.
  • Antimicrobials are chemicals that kill bacteria, fungi and viruses and are used to describe chemicals that inhibit the growth of microorganisms.
  • Antibiotics are chemicals that are only effective against bacteria.
  • Over a period of time, bacteria can become resistant to antimicrobials - mutations can take place in microorganisms which leads to new strains of bacteria and fungi that are not affected by the antimicrobial which reproduce and pass on the resistance.
  • To prevent resistance to antibiotics doctors should only prescribe when necessary and patients should complete a course of them even if they are feeling better.
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Testing drugs and vaccines

  • Before drugs can be used they have to be tested for safety and effectiveness.
  • The methods for this testing can be controversial.
  • First tests are on human cells grown in labs - shows if drugs will cause damage to cells, no people or animals are harmed, doesn't show effects of drugs on whole organism, some people believe that growing human cells for testing is unnatural/wrong.
  • After, tests are on animals - shows if drugs are effective in body conditions, shows if drugs are safe for whole body, animals can suffer/die and they might react differently to humans.
  • After, clinical trials are carried out on healthy volunteers to test for safety and people with the illness to test safety and effectiveness.
  • Important to carry out long-term trials - sometimes side effects only show after time.
  • Clinical trials compare effects of new drugs with old ones - patients have to agree to do it.
  • 3 types of trial; Open-label - both the doctor and patient know they are using a new treatment, Blind - the doctor knows which treatment the patient is getting but the patient does not, this removes bias, Double-blind - neither the patient or the doctor know if the patient is receiving the treatment or the placebo.
  • Placebos are sometimes used in medical trials but they create an ethical dilemma, these can not be used on sick patients because it gives them false hope.
  • Difficult to disguise a placebo.
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The Heart

  • Muscular organ in the circulatory system.
  • Beats automaticallym pumping blood around body to provide cells with oxygen and dissolved food for respiration.
  • Blood removes carbon dioxide and water as waste products.
  • Blood from rest of body enters right atrium then moves into the right ventricle before being pumped to lungs.
  • When oxygenated blood returns to heart, it enters the left atrium and moves into the left ventricle before being pumped to the rest of the body.
  • Heart is called double pump because blood returns to it twice.
  • Mainly made up of muscle cells which require oxygen and dissolved food so the heart needs its own blood supply.
  • Arteries carry blood away from the heart, towards the organs and substances cannot pass through the thick, elastic, muscular walls which cope with high pressure in vessels.
  • Veins carry blood from organs back to the heart and substances can't pass through the walls.
  • Valves prevent the back flow of blood.
  • Capillaries are narrow, thin-walled vessels that allow blood to move through one cell at a time, dissolved gases and nutrients can move out of capillary into surrounding cells and waste products move back into the blood.
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Heart Disease

  • Abnormality of the heart that can lead to a heart attack.
  • Usually caused by lifestyle and/or genetic factors.
  • Lifestyle factors that lead to heart disease include poor diet, cigarettes, misuse of drugs & stress
  • Fatty deposits can build up in blood vessels supplying the heart, restricting blood flow and not allowing the muscle cells to get enough oxygen and nutrients which can cause a heart attack.
  • Heart disease is quite common in the UK because people in the UK tend to be less active and typical diet is high in fats and salts.
  • Health professionals can do genetic tests to see how likely it is for someone to get heart disease. If it's high risk, they should reduce risk by not smoking, reducing salt intake, maintaining a healthy body weight and monitering cholesterol levels.
  • Heart rate can be measured by taking the pulse - if it is too fast or slow, it could indicate problems.
  • Heart disease is a big killer worldwide epidemiological studies try to identify what factors cause it
  • Blood pressure is the pressure of blood against artery walls and results from two forces; systolic (pressure from heart as it contracts and pumps blood into arteries and through circulatory system) and diastolic (pressure from force of arteries as they resist flow when heart relaxes).
  • Blood pressure can be measured using a sphygmomanometer which gives two numbers and gives the force needed to move the metal mercury inside.
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  • Maintenance of constant internal environment acheived by balancing bodily inputs and outputs, using nervous system and hormones to control.
  • Body has automatic control systems which ensure that the correct, steady levels of different factors which are important for cells to be able to function properly 
  • For it to work, control systems need to have; receptors to detect changes in environment, processing centres to receive information and coordinate responses automatically and effectors that produce the response.
  • When receptors detect that the temperature has increased above certain level, the processing centre (brain) sends signal to the effectors (in this case sweat glands) to produce sweat to cool down body, this process is called negative feedback.
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Water balance

  • Water is unput from drinks, food and respiration.
  • It is output through sweating, breathing and excretion of urine and faeces.
  • Body has to balance these to ensure there is enough water inside cells for cell activity.
  • Kidneys control the balance of water in the body by adjusting the amount of urine leaving body.
  • Kidneys filter the blood to remove all waste and to balance levels of other chemicals.
  • This balance is acheived by; filtering small molecules from the blood to form urine, reabsorbing all the sugar for respiration, reabsorbing as much salt and water as the body requires, excreting remaining urine, which is stored in the bladder.
  • The brain moniters water content constantly and causes the kidneys to adjust concentration and volume of urine produced.
  • If water level is too low, more water is reabsorbed by the kidneys.
  • If water level is too high, urine becomes more dilute and watery.
  • Amount of water that needs to be reabsorbed depends on a number of factors; External temperature - high=concentrated urine, low=dilute urine, Level of exercise - high=concentrated, low=dilute, Fluid intake - high=dilute, low=concentrated, Salt intake - high=dilute, low=concentrated.
  • Concentration of urine is controlled by ADH which is released in the bloodstream by the pituitary gland. Urine is more concentrated when ADH is released when level of water too low
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Effects of drugs


  • Causes the production of a greater volume of dilute, watery urine because ADH is suppressed which can lead to dehydration.


  • Makes people feel euphoric and can increase heart rate and blood pressure.
  • Also interferes with brain, causing errors in monitoring water content.
  • Taking ecstasy makes people feel hot and drink a lot of water but, the brain fails to send messages to the kidneys to get rid of the extra water.
  • Increases ADH production so urine is concentrated instead of dilute.
  • Water can not escape which causes cells to swell up so cells in the brain squash against the skull which could cause death.

Cannabis and Nicotine

  • Increase heart rate and risk of heart attack.
  • Cannabis reduces blood pressure, nicotine increases it.
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