S-Cool Revision Summary
Health can be defined as a person's physical, mental and social condition.
Disease is a disorder or malfunction of the mind or body, which destroys good health.
There are nine main categories of disease but some diseases are more difficult to classify and fit into more than one of them.
An infectious disease, which is always present in a population, is called endemic.
An epidemic occurs when a disease suddenly spreads rapidly and affects many people. If a disease spreads over a continent or even the world it will be termed pandemic.
Epidemiology is the study of patterns of diseases and the factors affecting its spread. Incidence, prevalence and mortality for a disease may be determined. Collecting information on the distribution of disease helps to identify the underlying causes and if it turns out to be infectious, may point to how it is transmitted.
Tobacco companies do not declare the ingredients in cigarettes, but upon analysis, they contain over 4000 different chemicals, many of which are toxic.
There are three main ingredients, which damage the gaseous exchange system or the cardiovascular system.
This is a mixture of aromatic substances, which settles on the airway linings and stimulates changes that may lead to obstructive lung disease and lung cancer.
This gas diffuses across the alveoli into the blood and onto the red blood cells, combining with haemoglobin to form carboxyhaemoglobin. This stops the haemoglobin from becoming fully saturated and so it carries 5-10% less oxygen.
This drug is absorbed readily into the blood and stimulates the nervous system to reduce the diameter of arterioles and the adrenal glands to release adrenaline. This increases heart rate and blood pressure and decreases the blood supply to the extremities - for example, the hands and feet.
After heart disease and strokes, this is the most common cause of illness and death in the UK.
Tar stimulates goblet cells and mucus glands to enlarge, producing more mucus. It destroys the cilia inhibiting the cleaning of the airways and mucus (containing dirt, bacteria and viruses) builds up blocking the smallest bronchioles.
Due to constant infection, phagocytes are attracted to the lungs where they release elastase - an enzyme that breaks down the elastin in the alveoli walls, to enable them to reach the surface where the bacteria are. Without adequate elastin, the alveoli cannot stretch, so they recoil and many burst.
Large air spaces appear, reducing the surface area for gas exchange and making sufferers breath more rapidly. As it progresses, patients become breathless and wheezy - they may need a constant supply of oxygen to stay alive.
Chronic obstructive pulmonary disease
This very disabling disease is the result of chronic bronchitis and emphysema occurring together. Troublesome breathlessness often only occurs once half of the lung tissue has been destroyed, which can only rarely be reversed. Britain has the highest death rate from this disease in the world.
Tar contains carcinogens, which react with the DNA in epithelial cells and cause mutations, which can lead to tumours.
These can be put into two groups:
Epidemiological evidence looks for patterns in the diseases, which smokers suffer from. It only shows an association and not a causal link.
Experimental evidence attempts to prove a causal link.
Cardiovascular diseases are degenerative diseases of the heart and circulatory system. They are responsible for 50% of deaths in developed countries and are multifactorial - smoking being one risk factor.
This is caused by a build-up of fatty material in artery walls, which reduces the flow of blood and therefore oxygen to the tissues. An atheroma is a build up of cholesterol, fibres, dead muscle cells and platelets and is more likely to develop upon damage to the artery wall by high blood pressure, carbon monoxide or nicotine.
Blood clots (thrombosis) become more likely and if one develops in the coronary artery a heart attack may be the result, while if it occurs in an artery supplying the brain, a stroke may result.
This is a disease of the coronary arteries, which branch from the aorta to supply the heart muscle. If atherosclerosis of these vessels occurs, then the heart has to work harder and blood pressure rises. This makes it difficult for the heart to receive the extra nutrients and oxygen it requires during exercise.
Three forms exist:
These occur if an artery in the brain burstsand blood leaks into the brain tissue or when an artery supplying the brain becomes blocked. The brain tissue becomes starved of oxygen and dies. Strokes can be fatal or very mild and may affect speech, memory and control of the body.
Smoking increases the concentration of blood cholesterol, which is a risk factor, so smokers increase the risk of having heart disease or a stroke. The risks of developing the disease increases with age and men are more at risk than women.
Being overweight increases the risk as does eating a diet high in saturated fat and salt. Diets with more antioxidants (vitamins) and soluble fibre decrease the risk as does taking regular exercise. Having diabetes raises the risks and high alcohol intake is another contributory factor.