Homework

Cardiovascular Case Study

The top trace below shows two action potential recorded intracellularly from a SA node cell.

Ventricular Muscle Fiber

a. On the line labeled ventricular muscle fiber, draw an action potential from a ventricular muscle fiber cell. On the line labeled ECG, draw the ECG and label all waves. (NOTE: Both the shape and the timing are important!).

b. On the first ventricular muscle fiber and SA node tracings, draw what would happen if tetrodotoxin (inhibitor of voltage gated sodium channels) was applied to the system.

c. On the second action potential in the ventricular recording and SA node recordings, draw the changes in the action potential that would occur if you apply a Ca2+ blocker to the recorded cell.

Jane Doe is a college cross country runner looking to compete in the Olympic Trials at the end of the year. She is currently participating in a research study for to determine the efficacy of a new workout recovery pill. As part of the study, cardiac function was measured before and after training. Figure one represents some of her pre-training results.

Figure 1. Echocardiography images showing a CROSS-SECTION of the left ventricle in a contracted and relaxed state. The white line represents LV Chamber Diameter. The ECG on the bottom is taken over a period of 3 secs. Measurement of blood flow from the heart demonstrated that 60 mL of blood leaves the heart per beat. This patient has an end-diastolic volume of 140 mL.

B.

A.

In the figure above, image ________ represents end-systole, whereas _______ represents end-diastole. Why do you know this?

a. Calculate Jane’s heart rate, stroke volume, end-systolic volume and cardiac output.

b. Pulse ox testing showed an oxygen saturation of 90%. If a test shows that there are 4 million oxygen molecules bound, how many hemoglobin molecules are there?

During training, her _________________________ nervous system is activated to meet her performance needs.

a. On the graph below, draw the action potential of a cell in her SA node before training and during training (include axis label). Briefly, explain the cell signaling mechanism (receptor and signaling pathway in the cell) of why this change occurs and then what is the overall response of the heart (specific to this cell).