AQA AS Biology Chapter 5.3 - HEART DISEASE

Revision notes on chapter 5.3 of the AQA AS Biology textbook concerning heart diseases:

Coronary heart disease




Myocardial infarction

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  • Created on: 06-05-11 21:15
Preview of AQA AS Biology Chapter 5.3 - HEART DISEASE

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Chapter 5.3 ­ Heart Disease ­ Notes
Almost half of all heart disease deaths are due to coronary heart disease, which
affects the coronary arteries, which supply the heart with the components for
respiration. Blood flow through these vessels is impaired by the build-up of fatty
deposits (atheroma). This can lead to myocardial infarcation (heart attack).
A fatty deposit that forms within a wall of an artery. Begins as fatty streaks which are
accumulations of white blood cells that have taken up low-density lipoproteins
(LPLs). The streaks enlarge and form an irregular patch, known as atheromatous
plaque. This is made up of deposits of cholesterol, fibres and dead muscle cells. They
bulge into the artery's lumen, which causes it to narrow so that the flow of blood is
reduced. Atheromas increase the risk of two dangerous conditions: thrombosis and
If an atheroma breaks through the endothelium of the blood vessel, a rough surface
is formed that interrupts the smooth flow of blood. This can result in the formation
of a blood clot (thrombus). The thrombus can block the vessel, reducing the blood
supply to its tissues. The region of tissue which is deprived of the blood often dies
due to lack of oxygen, glucose and other nutrients.
Atheromas can also weaken the artery walls. These weakened points swell to form a
balloon like, blood-filled structure known as an aneurysm. When the aneurysm bursts,
it leads to a haemorrhage and therefore severe blood loss to the region of the body
served by that artery. A brain aneurysm is known as a cerebrovascular accident (CVA)
or a stroke.
Myocardial Infarcation:
More commonly known as a heart attack. Occurs due to a reduced supply of oxygen
to the heart, due to a blockage in the coronary arteries. If this occurs close to the
junction of the coronary artery and the aorta, the heart will stop beating as it will
completely lose its blood supply. If the blockage is further along the coronary artery,
then the effects will be milder.
Risk Factors:
Smoking: smokers are up to six times as likely to contract heart disease. This is
because tobacco smoke contains two constituents which increase the likelihood of
heart disease:
Carbon monoxide ­ combines irreversibly with the haemoglobin in the red
blood cells, forming carboxyhaemoglobin, which reduces the oxygen-carrying
capacity of the blood, which means the heart must work harder. This can lead
to increased blood pressure, and also the heart can find it difficult to cope
during exercise, so the patient can suffer from angina or a heart attack.
Nicotine ­ stimulates adrenalin production, which increases heart rate and
blood pressure. This means that the patient has a greater risk of suffering
from a stroke or coronary heart disease. Nicotine also makes red blood cells

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High blood pressure: lifestyle factors such as excessive, prolonged stress, diet and
lack of exercise increase the risk of high blood pressure.…read more



This is amazing!!! do you have any other revision notes for the rest of AS biology!

If you do please please put them up thanks so much

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