Health and Diseases


Health And Diseases


this is a state of complete mental, physical and social wellbeing as well as being free from disease. this can be obtained from a balanced diet, having a positive outlook and being well integrated in society.


This is the departure of health caused by a malfunction of the mind or body. Diseases caused by organisms are called infectious. the symptoms of these are mostly physical.

parasites and pathogens.

These are MOs that live off another (a host). They can cause harm by taking nutrients away from the host. They can be external or internal. They may also cause damage by leaving the host exposed to invaders

Our bodies have good conditions for MOs to thrive some of these are beneficial. Pathogens are harmful as they take nutrients and causing damage leading to diseases.

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Transmission Of Diseases

Malaria is a disease caused by a protozoan called plasmodium. They can be found in the female anopheles mosquitoes. When as gametes sucking blood for proteins which are needed for her eggs, she also uptakes plasmodium cells. These cells then zygotes inside the mosquito's stomach and move to the salivary gland. The next time she bites someone the plasmodium cells will be injected into the body.  The cells then move to the liver where they will reproduce and be released in the blood. This process continues in the cycle. In this cycle the mosquitoes are vectors

The human immunodeficiency virus is  made up of lipids and proteins, the core contains RNA  enzymes. When someone has the virus inactive in their body they are HIV positive. when they become active they destroy t helper cells which makes people prone to pathogens and diseases. It can be transferred through: body fluids being shared, Unscreened blood transfusion, Sharing needles, across the placenta, through breast feeding.

Tuberculosis is caused by the bacterium mycobacterium tuberculosis. It is usually found in the lungs and is spread in tiny droplets of liquids. They can be spread by sneezing coughing and laughing. It takes a long period of close contact the disease. This can be affected by: overcrowding; poor ventilation , bad health, bad dieting, homelessness, migrating from a area where it is common.

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Global Impact

Malaria spreads in third world countries in which the female anopheles can survive. This is the tropical. These are in countries which are not able to afford vaccines or tablets to fight of the malaria. They may also not be able to get physical barriers that protect them from mosquitoes. This can cause it to spread easily causing many to die.

HIV can also be common in third world countries, this can be caused by a lack of education in these countries on the risks of unprotected sex and sharing needles. It is also hard to detect straight away making it spread more easily.

Since TB is spread through the air it is a global problem but it is worse in countries which have cramp unhygienic living conditions causing it to spread more easily.

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Primary Defences

skin is a physical barrier against invading bacteria and viruses. Harmful bacteria can't live on our skin as the fatty and lactic acid secreted in sweat causes the ph to be too high from them to survive. When the skin is cut blood clots around the wound sealing an entrance from which harmful MOs can enter while the skin is being repaired. its cells goes through keratinisation to harden the surface making it impermeable

substances ,oxygen and nutrients in food, have to enter our blood. this makes us prone to infections as the food an air we intake can have micro organisms. airways, lungs and the digestive system are protected by mucous membranes, goblet cells produce mucus which trap pathogens, cilia moves mucus in coordinated fashion to the back of the throat to be swallowed and the pathogen can be killed by acid in the stomach as the ph denatures the pathogens enzymes. Mucus membrane also present in guts, genitals, ears, and nose.

Our eyes and mouths have anti bacterial chemicals. Tears and saliva have substances that can break down chemicals. Ear canals have wax to trap pathogens and the vagina remains acidic so pathogens can't survive.

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Many trapped pathogens have to be killed before they can reproduce and cause symptoms this is done by phagocytes.

There are two types of phagocytes:

Neutrophils: These have multi lobed nucleus and are made in the bone marrow. they travel in the blood but can leave by being squeezed out in tissue fluid. they are also on the epithelial tissue of lungs. they are short lived and die after digesting a view pathogens but are released in large amounts to fight infection

Macrophage: They travel in the blood as macrocytes and settle in the lymph nodes and body organs where they developed into macrophages. They help the immune system produce a specific response to invading pathogens.

Pathogens are recognised as foreign due to their specific antigens. our owns cells have antigens that signal that they are ours and don't produce a response. antibodies in the blood attach to the antigen of pathogens, the phagocytes have receptors which binds to the antibodies which are attached to the pathogens. the phagocyte then envelops the pathogen by folding its membrane inwards. this traps the pathogen in a vacuole called a phagosome. Lysosomes then fuse with the 

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antibodies are produced by the lymphocytes and are known as immuno globulins. they have complementary shapes to a specific antigen, this means that our immune system has to produce a specific antibody for every antigen detected.


the antibody is a y shaped molecule made of four polypeptide chains held together by disulphide bridges. the constant region is always the same for every antigen as it allows it to attach to phagocyte during phagocytosis. the variable region is different depending on the antigen it is suppose to be complementary to the specific antigen. this region is able to bind to the antigen as it has the complementary shape, this is due to the correct sequence of amino acids. the hinge region allows flexibility so that the branches of the antibody move further apart and attach to another antigen. 


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How Antibodies Work


the antigens of pathogens maybe used as a binding site which is used to bind to the host cell. if an antibody attatches to the antigens then it cannot bind to the host cell, this is called neutralisation.



a large antibody which ressembles a group of y molecules attatched together and have many specific variable region is used to bind to multiple pathogens. this stops the pathogens from entering the host cell as the molecule is too large. this is called agglutination

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Why Cell Signalling Is Important?

during the immune response when a pathogen is detected, different types of cells need to work to do this they need to signal each other

the pathogen is first detected by the antigen it has signalling that it is foreign to the body cells

the infected cell which is damaged by the pathogens will use lysosomes to try and fight the invaders, this causes some of the pathogens to be damaged and parts to attach to the hosts plasma membrane. this acts as a distress signal to other cells in the immune systems as well as mark the host cells to be destroyed by t killer cells

macrophages are phagocytes that engulf the pathogen and separate the antigens to present them on the membrane, this is called antigen presentation. this is to find the lymphocyte to neutralise the specific pathogen

cytokine is a hormone like chemical that binds to the receptors of cells. macrophages release monokines to attract neutrophils and stimulate B cells to differentiate and produce antibodies. macrophages and T cells produce interleukin which cause B and T cells to stimulate proliferation and differentiate. A lot of cells produce interferon to stop cells replicating and stimulate t killer cells

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T lymphocytes

T lymphocytes: attaches to the pathogen with the complimentary antigen. It then differentiates into different T killer and helper cells
T killer cells: these attach to the pathogens and kills them by injecting them and secreting chemicals like hydrogen peroxide. It is a main defence against viral diseases
T helper cells: Attach to the MO with the complementary antigen, it then sends out cytokines to signal other cells to come to destroy the cells such as neutrophils or macrophages to perform phagocytosis. Some of these cells remain as memory cells so if the same pathogen attacks the response is much faster.

B lymphocytes

B lymphocytes: the ones with the correct receptors become activated, they migrate and start to reproduce through clonal expansion. They then produce antibodies with the correct variable region complementary to the antigen. These specific antibodies can then bind to the pathogen. Some of these cells remain as memory cells which live for a long time, so if the same pathogen invades the correct antibodies can be made quickly.

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Primary And Secondary Immune Response Notes

The primary response is a lot slower and ineffective than the secondary response. This is because it takes longer for the complementary lymphocyte to bind to the antigen and therefore it is slower at producing the correct T cells and antibodies.

The secondary response is a lot faster as the memory cells remembers the pathogen and is able to produce antibodies quickly before the pathogen can cause any illness

Active natural immunity: when a person becomes immune from first getting the infection and letting the body fight it off

Active artificial immunity: when a person is injected with a dead or inactive form of a pathogens the correct lymphocytes can bind to the antigen and allow memory cells to be formed.

Passive natural immunity: this is when a person obtains antibodies from either the mother through breast milk as a baby or from across the placenta when in the womb. This helps build up the immune system.

Passive artificial immunity: when antibodies are injected to build up the immune system E.G. tetanus shots.

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Government Response

The government need to ensure that they put enough money in vaccinations this is to stop it spreading and causing a epidemic. They must also inform those whom are most at risk such as the elderly, to take vaccinations and know the precautions they should take

Biodiversity is important as new antibiotics are being found from micro organisms, such as fungi. Plants also make antibiotics to protect them from predators. New MOs have not yet been found which can contain cures to diseases e.g. Cancer.

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Effects Of Smoking

Chronic bronchitis: this is when the smoke from a cigarette causes the goblet cells to over produce mucus while the cilia are paralysed so there is a build up of mucus. This can lead to a bacterial infection in the bronchi.

Emphysema: this is when chemicals in the smoke causes the neutrophils to be stimulated to the alveoli where they will secret neutrophil elastase which breaks down the walls of the alveoli, this causes the the surface area of gaseous exchange to be greatly reduced.

Lung cancer: the cigarette contain carcinogens which can effect the genetic material in cells causing them to divide uncontrollably. These produce tumours which obstruct airways. They most likely form at the the fork which branches in to two bronchi as it is where the smoke hits.

Nicotine: this causes hyper tension which would damage the lining of the arteries. Causing plaque to build up and obstruct the arteries causing a stroke to occur as the brain is starved of oxygen. Arteries can also burst killing brain cells as its flooded with blood

Carbon monoxide: it combines with haemoglobin to form carboxyhaemoglobin as haemoglobin has a high affinity for carbon monoxide so less oxygen is transported to the heart so it is harder to do exercise

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Data shows that as the number of people who smokes increases so do the cases of lung cancer. This correlation between smoking and lung cancer is also shown  a high proportion of people with the condition of lung cancer were also smokers. This is true for both males and females.


In the 1960s an experiment was done on beagles to test the hypothesis whether letting them inhale smoke from a cigarette would increase the chances of them getting lung cancer, this proved to be positive. This experiment is now done on human cells in scientific labs

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