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    Hell im not sure, something to do with the atria contracting i think. Blood shouldnt flow backwards though...
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    (Original post by panjabiflower)
    hi i was wondering if someone could explain to me why it is an advantage for having a large amount of elastic tissue in the aorta?
    So that it can cope with the high pressure/volume of blood being pumped through it without bursting. Think about it, you want it to have elastic recoil so it's harder to break and can cope with the stresses we put upon it.
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    it smoothes out pressure changes caused by the ventricles contracting. without it, the changes in pressure could cause the artery to cave in on itself or to burst
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    (Original post by Mattisabiologist)
    So that it can cope with the high pressure/volume of blood being pumped through it without bursting. Think about it, you want it to have elastic recoil so it's harder to break and can cope with the stresses we put upon it.
    Nvm got flow direction mixed up.
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    hey i have been asked to give two ways in which cardiac output is increased during vigorous exercise and this is worth 2 marks so i need to give two reasons. I am really confused as i initially thought that the number of beats per min would increase therefore heart rate would go up. But i think this is wrong....
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    (Original post by panjabiflower)
    hi i was wondering if someone could explain to me why it is an advantage for having a large amount of elastic tissue in the aorta?
    The walls of the aorta consist of three layers. They are the tunica adventitia, the tunica media, and the tunica intima.

    These layers are composed of connective tissue, as well as elastic fibers. These fibers allow the aorta to stretch to prevent over-expansion due to the pressure that is exerted on the walls by blood flow out of the left ventricle.

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    (Original post by panjabiflower)
    hey i have been asked to give two ways in which cardiac output is increased during vigorous exercise and this is worth 2 marks so i need to give two reasons. I am really confused as i initially thought that the number of beats per min would increase therefore heart rate would go up. But i think this is wrong....
    As exercise is increased, the muscles and organs in the body use (and need) more oxygen, and they also produce more waste (CO2). The body needs to replace the amount of oxygen to these muscles and organs, the heart beats faster to pump more blood around these muscle/organs hence replacing the used oxygen and collecting the waste product. This increases your heart rate, and also your breathing rate (increasing input of oxygen to distribute around the body, and exhaling the excess amounts of CO2).

    Ahhh, Biology lesson flashbacks

    Hope this helps

    EDIT: Because an answer is worth 2 marks, it doesn't always mean that you need to give 2 reasons, it could just mean it is asking for a more detailed answer than a single sentence/word.
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    thanks unistudent what you say makes sense.
    Do you know when the pressure in the pulmonary artery is increasing is it true that both the semi-lunar valves are closed and both av valves are open.
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    (Original post by UniStudent2009)
    As exercise is increased, the muscles and organs in the body use (and need) more oxygen, and they also produce more waste (CO2). The body needs to replace the amount of oxygen to these muscles and organs, the heart beats faster to pump more blood around these muscle/organs hence replacing the used oxygen and collecting the waste product. This increases your heart rate, and also your breathing rate (increasing input of oxygen to distribute around the body, and exhaling the excess amounts of CO2).

    Ahhh, Biology lesson flashbacks



    Hope this helps

    EDIT: Because an answer is worth 2 marks, it doesn't always mean that you need to give 2 reasons, it could just mean it is asking for a more detailed answer than a single sentence/word.
    Do you know when the pressure in the pulmonary artery is increasing is it true that both the semi-lunar valves are closed and both av valves are open.
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    (Original post by panjabiflower)
    Do you know when the pressure in the pulmonary artery is increasing is it true that both the semi-lunar valves are closed and both av valves are open.
    The pulmonary valve, is the semilunar valve of the heart that lies between the right ventricle and the pulmonary artery. The pulmonic valve opens in ventricular systole (when the pressure in the right ventricle rises above the pressure in the pulmonary artery).

    At the end of ventricular systole (when the pressure in the right ventricle falls rapidly) the pressure in the pulmonary artery will close the pulmonic valve, to prevent backflow of blood back into the right ventricle. At the same time, the atrioventricular valve will open, allowing a new 'batch' of blood to flow into the right ventricle, in preperation for the next ventricular systole.
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    Expansion of the aorta also creates a 'milking action' and aids the movement of blood around the body.
 
 
 
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