Questions Referring to The Cardiac Cycle 1 During Ventricula

Questions Referring to The Cardiac Cycle

1. During Ventricular Filling, in terms of pressure, briefly describe why the semilunar valves are not open

2. During Isovolumetric Contration, in terms of pressure, briefly describe what closes the AV valves during this phase

3. During Isovolumetric Contraction, in terms of pressure, briefly describe why the semilunar valves are not open during this phase

4. During Ventricular Ejection, in terms of pressure briefly describe why the AV valves do not open during this phase

5. During Isovolumetric Relaxation, in terms of pressure briefly describe what opens the AV valves during this phase

Solution

1) During venricular filling, ventricles are relaxing and blood from auricles is passing into respective ventricles. During relaxation of ventricles , pressure inside ventricled falls. This fall in ventricular pressure keeps the semilunar valves closed.

2. During isovolumetric contraction, AV valves are closed by the contraction of ventricles. During venricular contraction, pressure inside ventricles rises. This rise in ventricular pressure shuts and closes the AV valves.

3. In the isovolumetric contraction, the ventricles begin depolarizing and, while ventricular pressure starts to rise owing to contraction, the atrioventricular valves close in order to prevent backflow to the atria. At this stage, the semilunar vales (aortic and pulmonary valves) are also closed. The net result is that, while contraction causes ventricular pressures to rise sharply, there is no overall change in volume because of the closed valves. The semilunar valves remain close till the pressure in ventricles rises above the pressure in pulmonary and systemic aorta.

4. During ventricular ejextion, pressure inside ventricles is higher than the pressure of relaxing auticles, therefore AV valves remains closed.

5. During the relaxation of ventricles, pressure inside ventricles falls than that inside auricles. This fall in ventricular pressure open the AV valves so blood enters from aurucles into respective ventricles.