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44 Cards in this Set
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Health |
A state of physical, mental and social well-being, which includes the absence of disease and infirmity (weakness of body or mind) |
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Disease |
A condition that impairs the normal functioning of an organism This can be caused by infection with pathogens or parasites |
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Pathogen |
An organism that can cause disease Bacteria, fungi and viruses are all pathogens |
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Parasite |
An organism that lives on or in another organism (host) and causes damage to that organism Tapeworms, roundworms and fleas are all examples of parasites Some parasites cause disease, so they're also pathogens |
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What can cause disease? |
An infection with pathogens or parasites Genetic defects Nutritional deficiencies Environmental factors |
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What causes malaria? |
It's cause by the eukaryotic, single-celled parasite Plasmodium It's transmitted by mosquitos Mosquitos = vectors = don't cause the disease themselves but they spread the infection by transferring the parasite from one host to another Mosquitos transfer Plasmodium into an animal's blood when they feed on them Plasmodium infects the liver and RBCs, and disrupts the blood supply to vital organs |
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What causes AIDS? |
It is caused by HIV which infects human WBCs HIV can only reproduce inside the cells of the organism it has infected because it doesn't have the equipment (e.g. enzymes) to replicate on its own After the virus has reproduced it kills the WBCs as it leaves HIV leads to AIDS (acquired immune deficiency syndrome) |
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AIDS |
A condition where the immune system deteriorates and eventually fails due to the loss of WBCs It makes the sufferer more vulnerable to other infections like pneumonia |
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What three ways can HIV be transmitted by? |
Unprotected sexual intercourse Through infected bodily fluids e.g. sharing needles From mother to fetus through the placenta, breast milk or during childbirth |
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What causes tuberculosis (TB)? |
TB is a lung disease caused by the bacterium Mycobacterium tuberculosis TB spreads by 'droplet infection' - when an infected person coughs or sneezes, tiny droplets of saliva and mucus containing the bacteria are released from their mouth and nose, these droplets are then breathed in by other people Many people with TB are infected but don't show symptoms, but when become weakened the infection can become active |
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Why are malaria, HIV and TB most common in sub-Saharan Africa and other developing countries? |
Limited access to healthcare Limited health education to inform people how to avoid infectious diseases There's limited equipment to reduce the spread of infections Overcrowded conditions (increases risk of TB) |
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Why is studying the global distribution of malaria, HIV and TB important? |
Information can be used to find out where people are most at risk Data collected can be used to predict where epidemics are most likely to occur It's important for research It allows organisations to provide aid where it's needed most |
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What are teh body's primary defences? |
The skin and mucous membranes |
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How does skin act as a primary defence? |
It acts as a physical barrier, blocking pathogens from entering the body It also acts as a chemical barrier by producing chemicals that are antimicrobial and can lower pH, inhibiting the growth of pathogens |
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How do mucous membranes act as a primary defence? |
They protect body opening that are exposed to the environment Some membranes secrete mucus - a sticky substance that traps pathogens and contains antimicrobial |
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Immune response |
This is the body's reaction to a foreign antigen |
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Antigen |
Antigens are molecules found on the surface of cells When a pathogen invades the body, the antigens on its cell surface are identified as foreign, which activates cells in the immune system |
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What are the four main stages involved in the immune response |
1. Phagocytes engulf pathogens 2. Phagocytes activate T lymphocytes 3. T lymphocytes activate B lymphocytes, which divide into plasma cells 4. Plasma cells make more antibodies to a specific antigen |
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Outline the first stage of the immune response (Phagocytes engulf pathogens) |
A phagocyte recognises the antigens on a pathogen The cytoplasm of the phagocyte moves round the pathogen, engulfing it The pathogen is now contained in a phagocytic vacuole in the cytoplasm of the phagocyte A lysosome fuses with the phagocytic vacuole, the enzymes break down the pathogen The phagocyte then presents that pathogen's antigens - it sticks the antigens on its surface to activate other immune system cells |
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Phagocyte |
A type of WBC that carries out phagocytosis They are found in the blood and in tissue and are the first cells to respond to a pathogen inside the body |
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Outline the second stage of the immune response
(Phagocytes activate T lymphocytes) |
A T lymhocyte is another type of WBC Their surface is covered with receptors The receptors bind to antigens presented by phagocytes Each T lymphocyte has a different receptor on its surface When the receptor meets a complementary antigen, it binds to it This activates the T lymphocyte (clonal selection) The T lymphocyte then undergoes clonal expansion - it divides to produce clones, which then differentiate into different types of T lymphocytes that carry out different functions |
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What different functions do the T lymphocytes produced through clonal expansion have? |
Helper T cells - release substances to activate B lymphoctyes Some T lymphocytes attach to antigens on a pathogen and kill the cell Memory cells |
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Outline the third stage of the immune response
(T lymphocytes activate B lymphocytes which divide into plasma cells) |
B lymphocytes are another type of WBC They're covered with proteins called antibodies Antibodies bind to antigens to form an antigen-antibody complex Each B lymphocyte has a different shaped antibody on its surface When the antibody on the surface meets a complementary shaped antigen it binds to it This, plus substances release for helper T cells, activates the B lymphocyte (clonal selection) The activated B lymphocyte divides by mitosis, into plasma cells and memory cells (clonal expansion) |
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Cell signalling |
This is how cells communicate A cell may release a substance that binds to the receptors on another cell - this causes a response of some kind in the other cell Cell signalling is really important in the immune response because it helps to activate all the different types of WBCs that are needed |
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Outline the fourth stage of the immune response
(Plasma cells make more antibodies to a specific antigen) |
Plasma cells are clones of the B lymphocyte They secrete loads of the antibody, specific to the antigen, into the blood These antibodies will bind to the antigens on the surface of the pathogen to form lots of antigen-antibody complexes |
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The structure of antibodies |
Variable regions - form antigen binding sites (shape is complementary to a particular antigen) Hinge regions - allows flexibility when the antibody binds to the antigen Constant regions - allow binding to receptors on immune system cells (same on all antibodies) Disulfide bridges - hold the polypeptide chains together |
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How do antibodies help to clear an infection? (Agglutinating proteins) |
Antibodies have two binding sites so can bind to two pathogens at the same time, so pathogens become clumped together Phagocytes then bind to the antibodies and phagocytose a lot of pathogens all at once |
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How do antibodies help to clear an infection?
(Neutralising toxins and preventing the pathogen binding to human cells) |
Neutralising toxins - toxins are inactivated (neutralised) so they can't affect human cells
Preventing the pathogen binding to human cells - when they bind to antigens on pathogens they may block the cell surface receptors that pathogens need to bind to the host cells |
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Why is the primary response slow? |
When the pathogen enters the body for the first time the antigen on its surface activate the immune system (primary response) It is slow because there aren't many B lymphocytes that can make the antibody needed to bind to it Eventually the body will produce enough of the right antibody to overcome the infection After being exposed to an antigen, both T and B lymphocytes produce memory cells which remain in the body for a long time Memory T lymphocytes remember the specific antigen Memory B lymphocytes remember the specific antibodies needed The person is now immune |
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Why is the secondary response faster? |
If the same pathogen enters the body, the immune response will be a lot faster Memory B lymphocytes divide into plasma cells and produce the right antibody to the antigen Memory T lymphocytes divide into the correct type of T lymphocytes to kill the cell carrying the antigen The second response often gets rid of the pathogen before any symptoms are shown |
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Active immunity |
When the immune system makes its own antibodies after being stimulated by an antigen |
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What are the two different types of active immunity? |
Natural - this is when you become immune after catching a disease Artificial - this is when you become immune after you've been given a vaccination containing a harmless dose of antigen |
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Passive immunity |
When the immune system doesn't produce any antibodies of its own, it's given antibodies made by a different organism |
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What are the two different types of passive immunity? |
Natural - this is when a baby becomes immune due to the antibodies it receives from its mother, through the placenta and in breast milk Artificial - this is when you become immune after being injected with antibodies from someone else |
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How do vaccines help to control disease? |
Vaccines contain antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease This means you become immune with out any of the symptoms |
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Herd immunity |
If everyone in a community is vaccinated against a disease, the disease becomes really rare This means that even people who haven't been vaccinated are unlikely to get the disease because there is no one to get it from |
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Why do new influenza vaccines have to be developed every year? |
The influenza virus causes influenza (flu) Proteins on the surface of the influenza act as antigens, triggering the immune system These antigens can change regularly, forming new strains Memory cells produced from the vaccination with one strain will not recognise other strains with different antigens |
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Why do possible sources of medcines need to be protected? |
Many medicinal drugs are manufactured using natural compounds found in plants, animals or microorganisms Only a small proportion of organsims have been investigated so it's possible that organisms exist that contain compounds that could treat currently incurable diseases Possible sources of drugs need to be protected by maintaining biodiversity |
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How does smoking increase the risk of atherosclerosis? |
When damage occurs to the lining of the artery, WBCs move into the area Over time more WBCs, lipids and connective tissue build up and harden to form a fibrous plaque at the site of damage (atheroma) The atheroma partially blocks the lumen of the artery and restricts blood flow Atherosclerosis is the hardening of arteries due to the formation of atheromas Cigarette smoke contains nicotine, which causes an increase in blood pressure Increased blood pressure can cause damage to the arteries, leading to the formation more atheromas |
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How does smoking increase the risk of coronary heart disease? |
CHD is when the coronary arteries have lots of atheromas in them, this restricts blood flow to the heart A reduction in blood flow reduces the amount of oxygen supplied to the heart - this can cause pain or heart attack Carbon monoxide irreversibly combines with haemoglobin, reducing the amount of oxygen transported in the blood, which reduces the amount of oxygen available to tissues Nicotine make platelets sticky increasing blood clots - if clotting happens in the coronary arteries it could cause a heart attack The presence of atheromas also increases the risk of blood clots forming |
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How does smoking increase the risk of stroke? |
A stroke is a rapid loss of brain function due to disruption in the blood supply to the brain This can be caused by a blood clot in an artery leading to the brain, which reduces the amount of blood and so oxygen that reaches the brain Nicotine increases the risk of stroke because it increases the risk of clots forming Carbon monoxide also increases the risk of stroke because it reduces the amount of oxygen available to the brain by combining with haemoglobin |
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How does smoking increase the risk of lung cancer? |
Cigarette smoke contains many carcinogens These may cause mutationsin the DNA of lung cells which could lead to uncontrolled cell growth and the formation of a malignant tumour, these grow uncontrollably, blocking air flow to areas of the lung This decreases gas exchange and leads to a shortness of breath (body is struggling to take in oxygen) The tumour uses lots of nutrients and energy to grow, which causes weight loss |
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How does smoking increase the risk of chronic bronchitis? |
Chronic bronchitis is inflammation of the lungs The upper respiratory tract is lined with goblet cells that produces mucus to trap microorganisms, and it has cilia Cigarette smoke damages the cilia and causes the goblet cells to produce more mucus The mucus accumulates in the lungs which causes increased coughing to try and remove the mucus Microorganisms multiply in the mucus and cause lung infections that lead to inflammation which decreases gas exchange |
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How does smoking increase the risk of emphysema? |
Emphysema is a lung disease caused by smoking or long-term exposure to air pollution This causes inflammation which encourages phagocytes to the area, these produce an enzyme which breaks down elastin The alveolar walls are destroyed and the elasticity of the lungs is lost This reduces the surface area of the alveoli, so the rate of gaseous exchange decreases Symptoms include shortness of breath and wheezing |
