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Biology help

Discussion in 'MCAT Discussions' started by ssh18, Apr 5, 2007.

  1. ssh18

    ssh18 Member 5+ Year Member

    Mar 27, 2006
    Hi! I was hoping someone could help me out with this. The TPR book is says that if the bicuspid valve is ruptured, then blood flows both towards the aorta and towards the left atrium. Then it also says that this results in elevated pulmonary blood pressure and pulmonary edema <--this part I don't get...why is this the case?

    Also, just to clarify...does one action potential result in one heart beat in the cardiac muscle?

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  3. googlinggoogler

    googlinggoogler Member 2+ Year Member

    Jul 15, 2006
    I may be wrong, but from my understanding, the bicuspid (mitral) valve is between the left atrium and the left ventricle. The purpose of the valve is to prevent backflow. So if the valve is in place, after blood flows from the left atrium to the left ventrical, it should not flow back into the left atrium during systole (when the ventricles are squeezed). However, if this valve is ruptured, then you can imagine that when the left ventricle is squeezed, the blood will go forwards (towards the aorta) and backwards (the left atrium). Since the blood from the pulmonary veins dumps into the left atrium, I imagine having the backwards flow of blood from the left ventricle into the left atrium will cause a buildup of blood there. Thus, it will be hard for the normal occurance of bloodflow from the pulmonary vein into the left atrium. Hence, this will cause elevated pulmonary blood pressure. Pulmonary edma is defined as the swelling or fluid accumulation in the lungs. So the same explanation for the elevated pulmonary blood pressure would be appropriate for the fluid accumulation in the lungs.
  4. moi

    moi Ecstatic 5+ Year Member

    Aug 5, 2006
    To answer your other question, yes. Each action potential starts in the SA node and travels to the atria (making them contract) and also to the AV node (from where it travels to the ventricles and makes them contract).
  5. AnEyeLikeMars

    AnEyeLikeMars Member 7+ Year Member

    Dec 2, 2005
    Carrboro, NC

    Agreed. Inefficient pumping is like pinching a hose, pressure will build up behind the kink.

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