GCSE EDEXCEL BIOLOGY HEART AND CIRCULATION

GCSE EDEXCEL BIOLOGY HEART AND CIRCULATION

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  • Created on: 28-02-10 23:58
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Heart + Circulatory System
The circulatory System transports all types of materials around the body, Oxygen, Carbon Dioxide,
Hormones and Urea. They are transported in blood, in the blood vessels and are pumped around by
the heart.
Veins - Take blood to the heart.
Arteries ­ Take blood away from the heart
Capillaries - Small vessels, connecting arteries and veins together.
Heart Cycle
Blood enters into the atrium. Bicuspid and tricuspid valves are closed to blood cannot enter ventricle.
Blood therefore builds up, increasing the pressure enabling the valves to open. This occurs in the
ventricles too; as tri + bi valves close so pressure builds up so that the semi-lunar valves open. Blood
is ejected into the pulmonary artery and aorta. Pulmonary artery carries blood to the lungs and the
aorta has branches that carry blood all over the body. As ventricles empty high pressures in the two
arteries close the valves and so the cycle starts again.
Heart Rate changes during exercise because muscles must release more energy therefore we must
have an increased supply of oxygen for aerobic respiration. To deliver more oxygen the blood must
pump round a larger volume of blood and also the beats per minute will increase.
When we are stressed (angry or afraid), our heart rate increases due to the "fight or flight"
response. The increased output supplies extra blood to the muscles, so that the release extra energy
through aerobic respiration. So we can fight or run away. This is triggered by secretion of the
hormone adrenaline from the adrenal glands.

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Veins Arteries
Deoxy ­ to heart Oxy ­ Away from
Big Lumen Small Lumen
Thin muscular Layer Thick muscular layer
Thin Wall ­ few elastic Thick wall ­ lots of
fibres elastic fibres
Under low Pressure Under high pressure
Slowly Quickly
Travels constantly Travel in a pulse rate…read more

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