Question

1. Explain the flow of the blood as it passes through the heart.

2. Describe the Flank-Starling law in the heart.

3. In a resting state, explain what happened to the stroke volume when the heart rate increased. Why does this occur?

4. Describe how the heart alters stroke volume under sympathetic stimulation.

Answer 1

1. The deoxygenated blood from all over the body enters to the right auricle by inferior and superior vena cava. Than the blood passes to the right ventricle through the tricuspid valve. From the right ventricle blood passes to the lungs through the pulmonary artery and after getting oxygenated it comes back to the left auricle of the heart through pulmonary vein. From the left auricle blood goes to left ventricle through bicuspid or mitral valve and than passes throughout the body through the arteries and then capillaries.

2. Flank-Starling law states that, the stroke volume of the heart increases with increase of the blood volume in the ventricles of the heart. As stroke volume is the volume of blood pumped out by each ventricle.

3. As the heart rate increases, the stroke volume also increases. When the heart rate increases, the ventricular contraction of the muscles of the ventricle also increases and more volume of blood is pumped out from the ventricles and hence the stroke volume increases. It takes place due to decrease in parasympathetic activity of SA node with increased sympathetic activity.

4. Under sympathetic stimulation the heart rate increases and as the heart rate increases the stroke volume also increases.