Chapter 5

Blood returning to the human heart in one of the pulmonary veins will drain first into the_______, after which it passes into the______ and then enters the_____ circulation

The occurrence of cardiovascular diseases depends on the country of origin. For instance, Greece has a much lower cardiovascular disease rate than the United States. List a few possible reasons for this dependence. Would it be possible to test the reasons you list and how would you test them?

During diastole, heart chambers experience a. contractions that push blood into the downstream chamber. b. a decrease in pressure, associated with muscle relaxation. c. an opening of the left and right semilunar valves. d. an increase in intracellular calcium.

Discuss the differences between the cardiac muscle and skeletal muscle. Why are the action potentials different in these two types of muscle?

Do the chordae tendineae play an active role in heart valve motion? What is the purpose of these structures?

You are sitting outside on a warm day and are losing a great deal of fluid volume through sweat. You decide to have your blood pressure taken and find that it is higher than normal. Why is this?

If your alarm clock wakes you up and you rise rapidly, why may you feel lightheaded? Under other conditions, such as voluntary waking without an alarm clock, this does not occur, why?

A patient with congestive heart failure (severe myocardial infarction) has swollen ankles and feet. What is the relationship between heart failure and fluid loss from the vascular system?

A patient has an ECG, and the physician finds that there are two \(\mathrm{P}\) waves, followed by the \(\mathrm{QRS}\) complex and then the T wave. What is a possible reason behind this?

What are the principle valves in the heart and what are their functions?

Describe the salient aspects of the cardiac cycle.

A patient has a murmur in the ventricle that produces a loud gushing sound at the beginning of systole. Which valve is most likely causing this sound and what is a possible remedy for this murmur?

Calculate and plot the radial and circumferential stress distribution in the left ventricle at the end of systole ( \(p=80 \mathrm{mmHg}\); assume that the ventricle is a spherical shell). The inner radius of the heart is \(3.2 \mathrm{~cm}\) and the outer radius of the heart is \(3.8 \mathrm{~cm}\). The external pressure surrounding the heart is \(-1 \mathrm{mmHg}\). Under a disease condition in which the heart muscle thickens, calculate the radial and circumferential stress distribution in the left ventricle at the end of systole. Under these conditions the pressure at the end of systole remains the same, but the inner wall radius is \(3 \mathrm{~cm}\) and the outer wall radius is \(4.2 \mathrm{~cm}\). Compare this to normal conditions and comment.

Use the Cartesian Navier-Stokes equations to approximate the flow through the left ventricle during peak systole. Assume that the gravitational effects on the flow are negligible and that the opening orifice for blood to flow through is \(25 \mathrm{~mm}\) (aorta). The width of the left ventricle can be approximated as \(2 \mathrm{~cm}\) and the total length from the apex of the heart to the aortic valve as \(4 \mathrm{~cm}\). Determine the maximum velocity at both the aorta and within the ventricle. Blood viscosity is \(3.5 \mathrm{cP}\); assume that the pressure gradient across this flow is \(-1 \mathrm{mmHg} / \mathrm{cm}\).

During heart valve degeneration, the thickness of the valves can decrease. Calculate the tension on the inner leaflet to maintain the valve in a closed position. Assume that during valve closure, there is a pressure difference of \(3 \mathrm{mmHg}\), with an atrial pressure of \(5 \mathrm{mmHg}\). The radii of curvature for the principal directions of the valve leaflets are \(1 \mathrm{~cm}\) and \(1.05 \mathrm{~cm}\). There is a uniform width of \(3 \mathrm{~mm}\) across the leaflets. Assume that the leaflet is approximately one-third of the sphere.