Heart Valves and the Cardiac Cycle

Chamber C:

Aorta

Valve 2:

Aortic valve (Semilunar)

Predict if the mitral (left AV) valve is open or closed during this time. Explain.

Closed. Greater ventricular pressure will force blood under the cusps of the Mitral valve, closing it. Blood can only flow in one direction then, into the aorta.

If Chamber A represents the left atrium and Chamber B represents the left ventricle, name the part of the heart represented by the following elements of the diagram in Model 1: Valve 1:

Bicuspid Valve (Atrioventricular)

Using your answer to question 4, what do you predict would happen in a person's circulatory system if valve 2 in Model 1 did not close completely?

Blood would flow back from the Aorta into the Ventricle. Less blood would get pushed out into the body.

When the left ventricle pumps blood into the aorta, is left ventricular pressure greater than, less than, or equal to aortic pressure? Explain.

Greater than. It must be greater as fluids flow according to pressure gradients, from high to low.

When the ventricle is filling with blood, is left ventricular pressure greater than, less than, or equal to left atrial pressure? Explain.

Less than. Atrial pressure must be greater again, as fluids flow according to a pressure gradient, from high to low. Higher pressure must be in the atria allowing the blood to flow into the ventricle.

Is the mitral valve open or closed during this time? Explain

Open. Greater atrial pressure will keep the valve open allowing for the blood to flow from the atria to the ventricle

Is the aortic (left semilunar) valve open or closed during this time? Explain.

Open. LV pressure > aorta pressure....valve will be open. The force of the greater ventricular pressure will open the valve, as compared to the aortic pressure.

When the pressure in Chamber C is less than the pressure in Chamber B (PC < PB), is valve 2 open or closed? Explain.

Open. Pressure in chamber B forces the valve open because there is less pressure in Chamber C. Same as in number 1, Upstream pressure > Downstream pressure, so the valve is open.

When the pressure in Chamber A is greater than the pressure in Chamber B (PA > PB), is valve 1 open or closed? Explain.

Open. Pressure is greater in chamber A forcing valves to open. Upstream pressure > Downstream pressure so valve is open.

What relationship between pressures in Chambers A, B, and C results in both valves 1 and 2 being closed?

When Pc > PB > PA

Predict if the aortic valve is open or closed during this time. Explain.

Closed, because ventricular pressure is low and not applying a force upon the aortic valve.