Circulation Biology AQA IGCSE Revision Notes

Here are my notes for the circulation(4.3) part of the specification.

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  • Created by: Lisa24
  • Created on: 30-05-14 17:41
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Substances are transported from where they enter the body to the cells, or from the cells to where
they are removed from the body, by the circulatory system: There are three main parts to this
1) The heart,
2) The blood vessels
3) The blood.
The heart is an organ that pumps blood around the body. It has two pumps.
1) Much of the wall of the heart is made from muscle tissue.
The heart has four main chambers
1) Right atrium
2) Left atrium
3) Right ventricle
4) Left ventricle
The natural resting heart rate is controlled by a group of cells that act as a pacemaker, located in the
right atrium.
Artificial pacemakers are electrical devices used to correct irregularities in the heart rate.
Artificial hearts are occasionally used to keep patients alive whilst waiting for a heart transplant, or to
allow the heart to rest as an aid to recovery.
Circulation of the blood:
1) Blood enters the atria (top chambers) of the heart.
2) Deoxygenated blood comes from the vena cava into your right atrium.
3) Oxygenated blood flows from your lungs through the pulmonary vein into your left atrium
4) The atria contract and force blood into the ventricles.
1) The ventricles contract and force blood out of the heart.
2) The right ventricle forces deoxygenated blood into the pulmonary artery
3) The left ventricle forces oxygenated blood around the body in a big artery called the aorta
4) Valves in the heart close ensuring that blood flows in the correct direction. (prevents
backflow of blood to the heart)
5) Blood flows from the heart to the organs through arteries and returns through veins.
6) Capillaries link the arteries and the veins
The muscle of the left ventricle is thicker than the wall of the right ventricle
1) Allows the left ventricle to develop more pressure than the right
2) The pressure is needed as the blood leaving the left ventricle has to travel through the
whole body.
3) The blood from the right ventricle only needs to make its way through the pulmonary artery
to your lungs.

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The wall of your heart is almost entirely muscle
1) The muscle is supplied with oxygen by the coronary arteries. (See above)
We have a double circulation system. There are two separate circulation systems
1) One for the lungs
2) One for all other organs of the body.
Blood vessels carry blood around your body. There are three main types:
1) Arteries have thick walls containing muscle and elastic fibres
a. They carry bright red oxygenated blood
b.…read more

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The heart valve tissue might stiffen, preventing the valve from opening fully
2) The heart valve might develop a leak.
Faulty heart valves can be replaced using:
1) Biological valves ­ valves from humans or other mammals
2) Mechanical valves.…read more

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In other organs oxyhaemoglobin splits up into haemoglobin and oxygen. (concentration of
oxygen is lower)
White blood cells
1) Have a nucleus.
2) They form part of the body's defence system against microorganisms.
3) Fewer of them
4) Some form antibodies or antitoxins
5) Some engulf and digest invading bacteria and viruses
1) Small fragments of cells.
2) They have no nucleus.
3) Platelets help blood to clot at the site of a wound.…read more

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In organ transplants a diseased organ is replaced with a healthy one from a donor.
1) The recipient's antibodies may attack the antigens on the donor organ as they do not
recognise them as part of the recipient's body.
To prevent rejection of the transplanted organ:
1) A donor organ with a `tissue-type' similar to that of the recipient is used
2) The recipient is treated with drugs that suppress their immune system.…read more


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