EDEXCEL Biology topic 1.1 revision notes

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Topic one biology revision notes
Topic 1.1 what is cardiovascular disease?
Cardiovascular diseases (CVD's)- diseases of the heart and circulatory systems
Coronary heart disease (CHD)- one type of CVD
Diffusion- the net movement of molecules or ions from a region of their high concentration to a
region of their low concentration by relatively random movement down a concentration
gradient.
Open circulatory systems
In insects and some other animal groups, blood circulates in large open spaces a simple heart
pumps blood out into cavities surrounding the animals organs. The substances can defuse
between the blood and cells. When the muscle relaxes, blood is drawn back to the heart.
Closed circulatory systems
Many animals, including vertebrates, have a closed circulatory system. In which blood is
enclosed within vessels. This generates high pressure as the blood is forced along fairly narrow
chambers. This means blood travels faster so the system is more efficient.
Blood leaves the heart under pressure and flows along arteries and then arterioles
(small arteries) to capillaries.
There are extremely large numbers of capillaries. These come into close contact with
most cells in the body, where substances are exchanged between blood and cells.
After passing along the capillaries, blood returns to the heart by means of venules (small
veins) and veins.
Single circulatory systems
Found in fish or other like animals.
The heart pumps deoxygenated blood to gills
Gasses exchange via diffusion
Blood then flows to the rest of the body before returning to the heart.
Double circulatory systems
Found in birds and mammals
The right ventricle of the heart pumps deoxygenated blood to the lungs where it
receives oxygen.
The oxygenated blood returns to the heart to be pumped round the body by the left
ventricle.
Textbook reference ­ page 6 +7 (salter-Nuffield advanced biology As student text book)
Snab online references- activity 1.3 and 1.4

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Checkpoint- explain why many animals have a heart and circulation
Checkpoint- relate the structure of the heart to its function
Properties of water to make it an ideal transport medium
Water molecules are unusual among small molecules, because it is liquid at room temperature
where most other small molecules are gasses. Water is a polar molecule, it has an evenly
distributed electrical charge. The hydrogen end of the molecule is slightly positive and the
oxygen end slightly negative.…read more

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How does blood move through vessels?
The heart contracts (systole), blood is forced into to the aeries, their elastic walls stretch to
accommodate the blood. During diastole, the elasticity of the walls cause them to recoil behind
the blood. This pushes the blood forward.
When the blood reaches the smaller vessels it is a steady flow, in the capillaries, this allows
exchange between the blood and body cells through the one cell thick walls, this ensues there is
rapid diffusion between cells and the blood.…read more

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White blood cells leave the blood vessel, and move to the artery wall. Cells accumulate
chemicals from the blood, particularly cholesterol. A deposit builds up called an atheroma
Calcium salts and fibrous tissues build up at the site, causing plaque formation. Artery wall loses
some of its elasticity and hardens.
Plaques cause the artery to narrow, which leads to higher blood pressure and subsequently
caused more plaque formation.…read more

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