Cardiovascular Problem Set D

One best answer:

1. In a healthy young woman with a normal resting heart rate of 60 beats per minute, administration of a cholinergic muscarinic blocker (atropine) will:

• A. Decrease her resting heart rate by about 10%.
• B. Increase her resting heart rate by 50% or more.
• C. Lower her arterial blood pressure.
• D. Decrease her cardiac contractility.

2. In a healthy young man with a resting heart rate of 60 beats per minute., administration of a blocking dose of propranolol (β1 blocker) will:

• A. Decrease his resting heart rate by about 10%.
• B. Increase resting heart rate by 50% or more.
• C. Raise his arterial blood pressure.
• D. Increase his cardiac contractility.

For questions 3-13 answer:

• A. If the statement is only characteristic of sympathetic innervation of the heart.
• B. If the statement is only characteristic of parasympathetic innervation of the heart.
• C. If characteristic of A and B.
• D. If characteristic of neither A nor B.

3. When stimulated, the rate of cardiac muscle relaxation increases.

4. When stimulated, the interval of rapid ejection shortens.

5. When stimulated, K⁺ conductance of cardiac pacemaker tissue increases.

6. The cell bodies of the preganglionic neurons are located in the thoracic spinal cord.

7 Preganglionic neurons synapse with postganglionic neurons located in ganglia within the heart.

8. Blocking the action of its postganglionic neurotransmitter will stop the heart.

9. Binding of the transmitter to receptors in cardiac pacemaker tissue increases the inward Na⁺ and Ca²⁺ currents.

10. Alters the heart rate during the respiratory cycle on a "beat by beat" basis.

11. Is responsible for the marked decrease in cardiac contractility observed in severe hypoxia.

12. Acetylcholine is the neurotransmitter released by preganglionic neurons.

13. Increases uptake of Ca²⁺ by ventricular myocytes.

Indicate for questions 14 - 16 whether the statement is TRUE or FALSE.

14. The increased force of contraction that develops in response to an increased end-diastolic volume is a result of increased contractility.

15. Cutting all neural efferents to, and all neural afferents from the heart will produce a major mismatch in the output of the right and left ventricle.

16. The denervated heart responds to exercise with an increased heart rate and an increase in contractility.

QUESTIONS 17 - 20 ONE BEST ANSWER:

17. The "stronger beat" (more forceful contraction) that follows a premature extrasystole is a result of:

• A. longer than normal filling time for the "stronger beat".
• B. more Ca2+ is released from the sarcoplasmic reticulum during the "stronger beat".
• C. greater sympathetic stimulation during the "stronger beat".
• D. less parasympathetic stimulation during the "stronger beat".
• E. two of the above choices are correct.

In the figure below, the paired numbers at the top of the four cardiac function curves are systolic/diastolic pressures in an isolated carotid sinus of a dog. In this preparation the pressure within the sinus, whose glossopharyngeal afferent to the brain is still intact, is controlled independently of the systemic arterial pressure. Notice that lowering the carotid sinus pressure lowers left atrial pressure, and vice versa (e.g., 10 cm H₂O for 225/75 vs 3 cm H₂O for 63/47); this decrease in left atrial pressure results from increased left ventricular contractility at the lower carotid sinus pressures. Then notice (for each carotid sinus pressure) that as left atrial pressure is experimentally increased, stroke work increases; in other words, a Starling (preload) curve can be demonstrated for each level of contractility. Use the graph to answer questions 18-20. Stroke work (left ventricular stroke volume x mean aortic P) is a measure of left ventricular performance (contractility).

18. At which sinus pressures is norepinephrine asserting its maximum effect on the dog's cardiac function?

• A. 63/47
• B. 123/68
• C. 150/70
• D. 225/75

19. At which sinus pressures would the dog's heart rate be slowest?

• A. 63/47
• B. 123/68
• C. 150/70
• D. 225/75

20. At which sinus pressures would the degree of venoconstriction be maximal in the dogs femoral vein?

• A. 63/47
• B. 123/68
• C. 150/70
• D. 225/75

INSTRUCTIONS FOR QUESTIONS 21-24: Determine whether the following statements are TRUE or FALSE.

21. In heart muscle, adenosine acts as a vasodilator.

22. The vasculature of skeletal muscle and skin receive considerable sympathetic, but practically no parasympathetic innervation.

23. Skeletal muscle arterioles possess α1, but do not possess β2 adrenergic receptors.

24. The body's capacitance vessels respond to α1, but not to β adrenergic stimulation.

INSTRUCTIONS FOR QUESTIONS 25 - 27: Choose the one best answer.

25. If a young adult woman is administered an effective dose of an alpha-1 adrenergic blocker intravenously while she is standing, her mean arterial blood pressure will:

• A. increase, and her heart rate will increase.
• B. decrease, and her heart rate will decrease.
• C. increase, but her heart rate will decrease.
• D. decrease, but her heart rate will increase.
• E. decrease, but her heart rate will not change.

26. Sympathetic efferent activity of the medullary cardiovascular center will increase in response to:

• A. manual massage of the carotid bodies.
• B. elevating the temperature of the hypothalamus to above normal.
• C. lowering the concentration of dissolved CO2 in the brain to below normal.
• D. perfusing the carotid body with venous blood.
• E. perfusing the medulla with blood that lacks oxygen.

27. At a normal mean arterial pressure, the frequency of impulses arising from the carotid sinus baroreceptors is highest during:

• A. the rapid ejection phase of the cardiac cycle.
• B. isovolumic contraction.
• C. isovolumic relaxation.
• D. the moment when dicrotic notch is recorded in an aortic pressure recording.
• E. a time corresponding to the Q wave of the ECG.

INSTRUCTIONS FOR QUESTIONS 28 - 36: Under the circumstances given, state whether resistance to flow in the organ is primarily controlled by conditions (signals) originating in the organ itself (INTRINSIC factors) or by neural or hormonal input to the organ (EXTRINSIC factors).

28. resting skeletal muscle.

29. working skeletal muscle.

30. the sleeping brain.

31. the alert thinking brain.

32. left ventricular muscle.

33. skin on a hot humid day.

34. skin in a cold dry room.

35. small intestine while running a long distance race.

36. the kidney during a severe hemorrhage.

(Questions 37 and 38)

During an experiment in an anesthetized animal, pressures were recorded from the aorta and the right atrium, while cardiac output was simultaneously measured. The results of the experiment are indicated in the illustration below.

37. The most likely surgical procedure performed at the time indicated by the arrow above was the production of :

• A. Aortic valve insufficiency
• B. Aortic valve stenosis
• C. An arteriovenous anastomosis
• D. Pulmonary valve stenosis
• E. Bilateral vagotomy

38. In this situation, the surgical procedure would cause:

• A. Decreased right ventricular systolic pressure.
• B. Left heart output to exceed right heart output in the new steady state.
• C. Increased left ventricular systolic pressure
• D. Increased peripheral vena caval pressure

(Question 39)

39. Cardiac output curves for the right and left ventricles are shown above. In a steady-state, left ventricular end-diastolic pressure was 6 mmHg. Right ventricular end-diastolic pressure (in mmHg.) at that time was:

• A. 0
• B. 2
• C. 4
• D. 6
• E. Not determinable from these data

40. In the accompanying figure, pressures were recorded from the left ventricle and right atrium while contractile force was recorded from the right ventricle. For the question that follows, select the answer that is most logically associated with this figure. The time marker signals 1-second intervals. The most likely stimulus delivered during the time indicated by the signal was:

• A. Bilateral vagal stimulation
• B. Infusion of histamine
• C. Application of a clamp to the descending thoracic aorta
• D. Excitation of the stellate ganglion
• E. Sustained cardiac tamponade

(Questions 41-43)

An experiment is performed on an isolated, perfused hindlimb of a cat placed on a balance to measure the weight changes (as a reflection of interstitial fluid volume). The perfusion pump pressure (arterial inflow pressure) is kept constant while pressure and flow are monitored as indicated in the diagram below. The effects of several drugs are tested in the system.

The results obtained with the injection of the drugs at the arrows are plotted below:

Select the lettered drug from the diagram above that causes:

41. Venoconstriction

42. Arteriolar dilatation

43. Increased Capillary permeability