Biology - 1.1 - Causes Of Disease - Biology And Disease

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Unit 1, Topic 1 of AQA Biology AS Level.

What are pathogens?

Microorganisms that cause disease.

How do pathogens enter the body?

By penetrating one of the organism's interfaces with the environment.

How do pathogens cause disease?

- Damaging host tissue -
Sometimes the sheer number of pathogens causes damage by, e.g. preventing tissues functioning properly. Viruses inhibit the synthesis of DNA, RNA and proteins by the host cells. Many pathogens break down the membranes of the host cells.

- Producing toxins -
Most bacterial pathogens produce toxins. The cholera bacterium produces a toxin that leads to excessive water loss from the lining of the intestines.

Why are digestive and respiratory (gas-exchange) systems often the sites of entry for pathogens?

Digestive -
Food and water may carry pathogens into the stomach and intestines via the mouth. Cholera, typhoid and dysentery pathogens enter the body by this means.

Respiratory -
Many pathogens enter the body through the gas exchange surfaces. Pathogens that cause influenza, tuberculosis and bronchitis infect in this way.

Suggest one reason why oral antibiotics are not normally used to treat gastroenteritis and other diarrhoeal diseases

A person with gastroenteritis has vomiting and diarrhoea. Both symptoms mean that the antibiotic is unlikely to remain in the body long enough to be absorbed.

How are data on disease interpreted and analysed?

- Epidemiology
This is the study of the incidence ( number of cases) and pattern of a disease with a view to finding the means of preventing and controlling it. Epidemiologists collect date on diseases and various factors in the lives of people who have them. Looking at causal links and correlation.

What is correlation and what does it mean?

What is a correlation?
- A mutual connection or relationship, between two or more things.
- Interdependence of variable quantities.

When does it occur?
- When a change in one of two (or more) variables is reflected by a change in the other variable.

How is a causal link established?

When we have sufficient experimental evidence to prove that it is a cause.

What is risk?

A measure of the probability that damage to health will occur as a risk of a given hazard.

How is risk measured?

- Percentage.
A value that ranges from 0 per cent (nothing will occur) to 100 per cent (definite).

What factors effect the risk of contracting cancer?

Lifestyle factors -
- Diet
- Exercise (physical activity)
- Smoking
- Sunlight
- Obesity

Other -
- Age
- Genetics

What single lifestyle change within the population of the UK would bring about the greatest reduction in cancer rates?

Giving up smoking/not starting smoking.

6 factors we can control to help reduce the risk of coronary heart disease (CHD)

- Smoking:
Giving up smoking is the single most effective way of increasing life expectancy.

- High blood pressure:
Excessive prolonged stress, certain diets and lack of exercise all increase blood pressure and hence the risk of CHD.

- Blood cholesterol levels:
These can be kept lower by including fewer saturated fatty acids in the diet

- Obesity:
A body mass index (BMI) of over 25 brings increased risk of CHD.

- Diet:
High levels of salt in the diet raise blood pressure while high levels of saturated fatty acids increase blood cholesterol concentration. Both therefore increase the risk of CHD. By contrast, foods such as dietary fibre reduce the risk of CHD by lowering blood cholesterol levels.

- Physical activity:
Aerobic exercise can lower blood pressure and blood cholesterol as well as helping to avoid obesity. All of which reduce the risk of CHD.

In what three ways would 30 minutes of brisk exercise a day reduce your chances of suffering coronary heart disease?

- By lowering blood pressure
- By lowering blood cholesterol
- By helping to avoid obesity

How could you improve your diet in order to live longer?

- less alcohol
- more fruit and vegetables
- reduce salt intake
- eat less red and processed meat
- reduce calorie intake if overweight (BMI over 25)

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