Cardiovascular Problem Set B


Cardiovascular Problem Set B

 

Purpose questions 1-2: What are the major characteristics of cardiac non-pacemaker and pacemaker tissues?

 

1. The figure below displays action potentials from cardiac tissue treated with progressively larger doses of tetrodotoxin (TTX), a drug that blocks voltage-gated Na+ channels. The cardiac tissue was most likely:

Figure 23:13 from Physiology (3rd ed.) by R.M. Berne

and M. N Levy, Mosby Year Book, 1993

 

 

2. When a drug is added to an in vitro preparation of AV nodal tissue, the rate of spontaneous depolarization during phase 4 changes from that depicted by slope a to slope b (see figure below). Which of the following is most likely to have produced this change?

Figure 23:20 from Physiology (3rd ed.) by R.M. Berne

and M.N. Levy, Mosby Year Book, 1993

 

 

 

Questions 3-4: Purpose: Practice with ECG.

 

3. The ECG record shown below was most likely recorded from a person:

 

 

4. The following ECG recording is typical of a patient with:

 

 

Purpose of questions 5-21: Test your knowledge of the cardiac cycle, the concepts of cardiac preload, afterload, and contractility. INSTRUCTIONS: Use information in the figure below in solving questions 5 - 15:

 

The curves (loops) in the figure show the relationship between left ventricular pressure and left ventricular volume. Consider the loop with a bold border (MNOP) to represent the relationship in a normal resting person in a supine position.

5. For the normal loop, at point N:

 

6. For the normal loop, segment O-P represents an interval when:

 

7. For the normal loop, the heart is performing the most external mechanical work between segments:

 

8. For the normal loop, the "a" wave of jugular venous pressure will occur just prior to point:

 

9. For normal loop MNOP, what is the aortic blood pressure (mmHg) at the moment a dicrotic notch is being recorded?

 

9.5 During diastole of the cardiac cycle shown, arterial pressure (mmHg) in the person with loop MNOP :

 

10. Pulse pressure (mmHg) in the person with loop MNOP is _________.

 

11. The ejection fraction of the heart, whose PV loop has a left border at 50 ml is:

 

12. The individual whose PV loop has the highest systolic pressure also had a heart rate of 60 beats per minute. His/her cardiac output was __________.

 

13. In a normal resting individual, the time required for segment OPM is __________ the time required for segment MNO.

 

14. For the normal loop, phase zero of the action potential of ventricular muscle would occur sometime between:

 

15. For the normal loop, flow through the systemic capillaries would be greatest between:

 

 

USE THE FOLLOWING FIGURE AND CHOICES FOR QUESTIONS 16 - 21.

 

The curves (loops) shown in the figure are plots of left ventricular pressure as a function of left ventricular volume. Consider the loop with the bold border (MNOP) to represent the relationship in a normal resting person in a supine position.

 

INSTRUCTIONS: Use the choices listed below for questions 16 - 21.

 

16. Which loop represents the pressure-volume relationship during the first couple of contractions after an individual, who is lying on a "tilt" table, is raised from a supine position to an upright position?

 

17. Which loop represents the pressure-volume relationship during the first couple of contractions after the descending aorta is suddenly constricted.

 

18. Do any of the loops in the above figure correctly represent the pressure-volume relationship during the first contraction after an aortic aneurysm has burst? If not, draw a loop that does.

 

19. Which loop represents the pressure-volume relationship during the first few contractions after an individual is suddenly startled?

 

20. Do any of the loops correctly represent the pressure-volume relationship during the first few contractions after an intravenous infusion of a negative inotropic drug, e.g., propranolol? If not, draw a loop that does.

 

21. Which loop represents the pressure-volume relationship during the first contraction after a rapid intravenous infusion of blood into a normal person.

 

Purpose of questions 22-33: Understand the significance of the "Starling" forces that control movement of fluid into and out of the tissues. INSTRUCTIONS: Use information in the following figure (microcirculation of a leg muscle), as an aid in solving questions these questions. In this the plasma oncotic pressure is 25 mmHg. Unless otherwise, indicated, consider the tissue oncotic pressure and the tissue hydrostatic pressure to be negligible (zero).

 

(Figure is modified from Berne and Levy)

 

22. Select the best answer: In the figure above, hydrostatic pressure was referred to as which of the following in the first cardiovascular problem set? (transmural pressure)(intraluminal pressure) (LaPlace vessel wall tension)

 

22.1. True or False: Oncotic pressure comprises a portion of the of the plasma's osmotic pressure.

 

22.2. True or False: Oncotic pressure comprises a portion of the plasma's hydrostatic pressure.

 

22.3. True or False: By the time plasma reaches the venous end of the capillary, the plasma's osmotic pressure is equal to the osmotic pressure in the interstitial space.

 

22.4 True or False: By the time plasma reaches the venous end of the capillary, the plasma's oncotic pressure is equal to the oncotic pressure in the interstitial space.

 

22. In the figure above, the net filtration pressure at the arterial end of the capillary is ________, and at the venous end of the capillary it is _______ .

 

23. If the mean hydrostatic pressure in this capillary were 23.5 mmHg, plasma in this capillary would undergo a net (gain) (loss) of water.

 

24. An α1 adrenergic drug is administered which causes the arterioles of the microcirculation in the above figure to constrict. As a result, the net filtration pressure in the capillary will (increase, decrease, not change).

 

25. The right ventricle of the person whose leg muscle capillary is shown in the figure begins to fail, (i.e., is unable to pump the blood that reaches it). As a result, the net filtration in the capillary will (increase, decrease, not change). The volume of muscle interstitial fluid will (increase, decrease, not change). If the left ventricle (but not the right) fails, where does interstitial fluid accumulate?

 

26. Hepatitis decreases the capacity of the liver to synthesize albumin and secrete it into the blood. As a result, the volume of interstitial fluid in the tissue shown in the figure (increases, decreases, does not change).

 

27. If an individual becomes dehydrated, the oncotic pressure in his/her capillaries will (increase, decrease, stay the same), and as a result, net filtration will (increase, decrease, stay the same). During dehydration, plasma osmotic pressure increases more than can be accounted for by the change in plasma oncotic pressure. What accounts for this?

 

28. A burn damages the capillary endothelium allowing increased amounts of albumin to enter the interstitial space. As a result, the volume of interstitial fluid (increases, decreases, does not change) in the affected area.

 

29. In the tissue shown in the figure there is a relatively close balance between filtration and absorption. What are typical hydrostatic pressures at the arterial (afferent) end of the renal glomerular capillaries? What are typical hydrostatic pressures at the arterial end of pulmonary capillaries? If these hydrostatic pressures were reversed, what would be the effect on renal function and on lung function.

 

30. In primary hypothyroidism, (myxedema) mucopolysaccharides accumulate in the interstitial space of subcutaneous tissues, significantly increasing tissue-oncotic pressure. As a result, the volume of subcutaneous interstitial fluid (increases, decreases, does not change).

 

31. Radical mastectomy with dissection of axillary lymph nodes sometimes destroys the major lymphatic vessels in the affected arm. As a result, the arm becomes edematous and swells considerably. What accounts for this? The swelling can sometimes be relieved by wearing a tight fitting nylon glove over much of the arm. The glove reduces swelling by increasing (capillary hydrostatic pressure, capillary oncotic pressure, tissue hydrostatic pressure, flow in the minor lymphatic vessels).

 

32. A man with congestive heart failure finds that he is dyspneic (out of breath) when he lies down to sleep. Propping up his head and shoulders on several pillows while sleeping relieves his symptoms. This technique is effective by virtue of (increasing pulmonary capillary oncotic pressure, increasing pulmonary tissue hydrostatic pressure, increasing flow in the pulmonary lymphatic vessels, decreasing pulmonary capillary hydrostatic pressure).

 

 

 

 

 

 

33. If:

Mean capillary hydrostatic pressure = 22 mmHg

Plasma colloid oncotic pressure = 24 mmHg

Tissue hydrostatic pressure = 3 mmHg

Tissue colloid oncotic pressure = 1 mmHg

According to the Starling hypothesis, the gradient for fluid movement (in mmHg) will be:

 

Purpose of questions 34 and 34.1: Practice with "baby" Poiseuille, ΔP = Q x R

 

34. A male patient has the following cardiovascular parameters.

HR = 60/min.; Cardiac Output = 5L/min.

mean pressure in ascending aorta = 100 mmHg

mean pressure in right atrium = 5 mmHg

A drug is given that speeds up the HR to 90/min., but venous return, right atrial pressure and total peripheral resistance do not change.

The patient's mean pressure in the ascending aorta is now:

 

34.1 A drug that increases heart rate will increase cardiac output only if it also increases ____________________.