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The Functioning of the Circulatory System.

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Introduction

The Functioning of the Circulatory System. Haemoglobin picks up oxygen from the lungs where it is abundant and delivers it to where it is needed which is every cell within our bodies especially muscles cells which are respiring to produce enough energy for the muscles to operate. Four-subunit globular oxygen-carrying protein of. There are two alpha and two beta chains in adult humans; the haem group is an iron Fe2+ ion which is responsible for binding to the oxygen. During respiration, CO2 is produced. This diffuses into the blood plasma and into the red blood cells. Inside the red blood cells are many molecules of an enzyme called carbonic anhydrase. It catalyses the reaction between CO2 and H2O. The resulting carbonic acid then dissociates into HCO3- + H+. (Both reactions are reversible) CO2 + H2O H2CO3 carbon dioxide + water carbonic acid H2CO3 HCO3- + H+ Carbonic acid hydrogen carbonate ion hydrogen ion Therefore, the more CO2, the more the dissociation curve shifts to the right. Haemoglobin also transports carbon dioxide and has the ability to bind hydrogen ions, a property which is essential for the maintenance of blood pH. ...read more.

Middle

The waves make the muscles of the atriums contract and so forcing the blood from the atriums which come in from the Vena cava as well as the Pulmonary Vein. The blood is forced into the Ventricles. The wave of excitation is slightly delayed from reaching the ventricles by the AVN because it contains a layer of non-conducting cells. The impulse travels down the nerve in the bundle of His and starts to contract the ventricles from the bottom upwards. This is an advantage because all of the blood is forced out this way. The blood will be forced in to Pulmonary vein and the Aorta. Blood will go to the lungs and then around the body again. It returns back to the heart before going around the body because it needs a pressure boost so the Pressure filtration process in the kidneys is carried out successfully. Even though the heart can beat independently out of our bodies the heart rate needs to be controlled to suit the occasion. ...read more.

Conclusion

As soon as this happens the blood will be richer in oxygen and will be able to satisfy the oxygen demand of the respiring muscles. The medulla itself acts as a receptor because the cells of the medulla respond to increasing carbon dioxide levels. The nerves that act on the rate of the heart are antagonistic nerves because they have a reverse effect on the rate of the heart beating. They are both going from the cardiovascular centre in the medulla to the sino-atrial node in the top region of the heart. Cardiac output = stroke volume + number of beats per minute (Stroke volume is the volume pumped in one beat) Which means if a person is an athlete for example then their number of beats per minute will be less but the cardiac output will be the same therefore the athletes heart increases the stroke volume which means that at one beat of the heart the ventricles push out more blood to maintain oxygen levels in the blood. ...read more.

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