Topic 1: Causes of Diseases

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  • Created on: 12-03-14 21:34
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Topic 1: Causes of Disease
1.1 Pathogens
Disease: A disorder of structure or function in a human, animal, or plant, esp. one that produces specific
signs or symptoms or that affects a specific location and is not simply a direct result of physical injury
Micro-organism: a single celled organism that cannot be seen by the naked eye, which can only be seen
through a microscope.
Pathogen: Micro-organisms that can and are likely to cause disease, such as bacteria, viruses and fungi
Transmission: the transfer of a pathogen from one individual to another.
Causing Disease
Gaining Entry to Host
Micro-organisms can gain entry into the host through an interface, such as the gas-exchange system and the
digestive system.
Both of these systems are ideal (optimum) conditions for entry, as these conditions increase the rate of
diffusion and osmosis
E.g. both environments are moist, have increased in surface area to volume ratios, thin linings.
Common pathogens that gain entry through the gas exchange system include pathogens that cause
influenza, tuberculosis and bronchitis.
Common pathogens that gain entry through the digestive system include cholera, typhoid, and dysentery
Colonising tissues
Viruses cause disease by colonising the tissues, as viruses are made up of proteins. They are therefore
unable to cause disease alone.
Resisting defence mechanisms
See Below
Causing Damage
Bacteria cause disease by releasing toxins which causes damage to the host tissues.
Viruses cause damage to the tissues by inhibiting the synthesis of DNA, RNA, and proteins. They are also
known to damage the membrane of their host cells.
Defence Mechanisms - These are natural defences the body has in order to prevent the entry of pathogens, which
Mucous linings which covers exchange surfaces, which are difficult to penetrate
Enzyme production which break down pathogens
Stomach acid production which kills the micro-organisms.
Bacteria Virus
1.2 Data and Disease
Analysis and Interpretation of Data
Epidemiology ­ the study of incidence and pattern of a disease with a view to finding a means to prevent and
control it.
Shivani Barot 13FPage 1

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Topic 1: Causes of Disease
Data on a given disease is collected, and then it is analysed to find a pattern or relationship between the
variables, e.g. which factors are a causal or correlation links.
Correlation and Causal Relationships
Causal Relationships are where the dependent variable is directly affected by the independent variable.
Correlation Relationships are where a dependent variable may be affected by the independent variable, but
there is not enough evidence to state that it is a direct cause.…read more

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Topic 1: Causes of Disease
Reduced cholesterol intake
Reduced saturated fats
Alcohol intake
Increased aerobic exercise
Increased fibre intake
Shivani Barot 13FPage 3…read more


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