1. Causes of Disease Flashcards
What are the features of microorganisms?
⋆ They are single-celled
⋆ Most live permanently in our bodies but cause no harm
⋆ Some are pathogens and cause disease
What is disease?
A malfunction of the body or mind which has an adverse effect on good health
What must a microorganism do to be considered a pathogen?
Gain entry to the host
Colonise their tissues
Resist the defences
Damage host tissues
How do microorganisms get inside of the body?
By penetrating one of the organism’s interfaces with the environment
What is an interface?
A boundary linking two systems e.g. internal and external environments
One interface is the skin. Why is it hard to penetrate?
It is usually very protective because it is a thick, continuous layer. It can only be passed when cut or bitten
The gas exchange system and the digestive system are easier interfaces to penetrate. Why?
⋆ These interfaces are moist and sticky
⋆ The body linings are thin, have a large SA and a good blood supply
⋆ This makes it easier for pathogens to enter the body
⋆ Pathogens that cause influenza, tuberculosis and bronchitis enter the body through gas-exchange surfaces
⋆ Food and water carry pathogens to the stomach and intestine e.g. cholera and typhoid
What are your body’s natural defences?
⋆ Mucous layer e.g. on exchange surfaces that is difficult to penetrate
⋆ Enzymes to break down pathogens
⋆ Stomach acid to break down pathogens
⋆ Skin to stop pathogens entering the body
⋆ Platelets to cover up cuts in the skin
How do pathogens cause disease?
⋆ Damaging host tissues
This stops them working properly
Viruses inhibit DNA, RNA and protein synthesis
Many pathogens break down the membranes of host cells
⋆ Producing toxins
e.g. cholera toxin leads to excessive water loss from the intestine lining
What two other factors can contribute to developing a disease?
Genetics and lifestyle
What determines how quickly symptoms show?
How quickly the pathogens divide
What is epidemiology?
The study of the incidence and pattern of a disease with a view to finding the means to preventing and controlling it
What is correlation?
When change in one of two variables is reflected by a change in the other variable (read paragraph p. 6)
What is risk?
A measure of the probability that damage to health will occur as a result of a given hazard. Risk has two elements: probability and consequence
⋆ Health risks need a timescale e.g. 70% in the next year
⋆ Risk is measured out of 100%
⋆ Risk is often measured relative to those not exposed to a hazard
What are the lifestyle factors affecting the risk of developing cancer?
⋆ Light exposure (skin cancer) ⋆ Obesity ⋆ Activity ⋆ Nutrition ⋆ Smoking
