Chapter 16 Control of Cardiovascular Function

1. Chapter 16Control of Cardiovascular Function

2. Path of Blood Flow Scenario: • You inject a medication into the client’s arm • Within a few minutes, some of that drug has reached the client’s liver and is being deactivated Question: • How did it get there?

3. Simplified Path of Blood Flow body left right heart heart lungs

4. Heart Anatomy

5. Question Tell whether the following statement is true or false. The pulmonary circulation moves blood through the left side of the heart.

6. Answer False Rationale:The right side of the heart pumps blood to the lungs through the pulmonary arteries, where gas exchange takes place. The left side of the heart is considered systemic circulation because blood is pumped to all body tissues.

7. The Heart Layers

8. The Basics of Cell Firing • Cells begin with a negative charge: resting membrane potential • Stimulus causes some Na+ channels to open • Na+ diffuses in, making the cell more positive Threshold potential Resting membrane potential Stimulus

9. The Basics of Cell Firing (cont.) Action potential • At threshold potential, more Na+ channels open • Na+ rushes in, making the cell very positive: depolarization • Action potential: the cell responds (e.g., by contracting) Threshold potential Resting membrane potential Stimulus

10. The Basics of Cell Firing (cont.) Action potential • K+ channels open • K+ diffuses out, making the cell negative again: repolarization • Na+/K+ ATPase removes the Na+ from the cell and pumps the K+ back in Threshold potential Resting membrane potential Stimulus

11. Cardiac Muscle Firing • Cells begin with a negative charge: resting membrane potential • Calcium leak lets Ca2+ diffuse in, making the cell more positive Threshold potential Resting membrane potential Calcium leak

12. Cardiac Muscle Firing (cont.) Action potential • At threshold potential, more Na+ channels open • Na+ rushes in, making the cell very positive: depolarization • Action potential: the cell responds (e.g., by contracting) Threshold potential Resting membrane potential Calcium leak

13. Cardiac Muscle Firing (cont.) Action potential • K+ channels open • K+ diffuses out, making the cell negative again, but Ca2+ channels are still allowing Ca2+ to enter • The cell remains positive: plateau PLATEAU Threshold potential Calcium leak

14. Cardiac Muscle Firing (cont.) • During plateau, the muscle contracts strongly • Then the Ca2+ channels shut and it repolarizes Action potential PLATEAU Threshold potential Calcium leak

15. Question Which ion channels allow cardiac muscle to fire without a stimulus? • Na+ • K+ • Ca2+ • Cl-

16. Answer • Ca2+ Rationale:In the SA and AV nodes, resting cardiac muscle cells have open Ca2+ channels. This allows Ca2+ to leak into the cells, making them more positive (the cells reach threshold this way without the need for a stimulus).

17. The Cell Passes the Impulse to Its Neighbors

18. Heart Contraction How would each of the following affect heart contraction: • A calcium channel blocker • An Na+ channel blocker • A drug that opened Na+ channels • A drug that opened K+ channels

19. Cardiac Cycle—Diastole • Ventricles relaxed • Blood entering atria • Blood flows through AV valves into ventricles • Semilunar valves are closed

21. Cardiac Cycle—Systole • Ventricles contract • Blood pushes against AV valves and they shut • Blood pushes through semilunar valves into aorta and pulmonary trunk

23. Question Which of the following statements is true about ventricular systole? • Atria contract • Ventricles contract • AV valves are open • Semilunar valves are closed

24. Answer • Ventricles contract Rationale:During ventricular systole, the ventricles contract. Because blood is being forced from the ventricles, semilunar valves must be open and AV valves closed. The atria are in diastole (relaxation) during ventricular systole.

25. Cardiac Cycle Discussion: • Arrange these steps in the proper order: – Ventricles relax – First heart sound – Systole – Semilunar valves open – Diastole – AV valves close – AV valves open – Semilunar valves close – Ventricles contract – Second heart sound

26. Pressure, Resistance, Flow • Fluid flow through a vessel depends on: • The pressure difference between ends of the vessel • Pressure pushes the fluid through • Pressure keeps the vessel from collapsing • The vessel’s resistance to fluid flow • Small vessels have more resistance • More viscous fluids have greater resistance

27. Pressure, Resistance, Flow of Blood • Blood flow through a vessel depends on: • Heart creating pressure difference between ends of the vessel • Heart pushing the blood through • Blood pressure keeping the vessels open • The vessel’s resistance to fluid flow • Constricting arterioles increasing resistance • Increased hematocrit increasing resistance

28. Discussion How will each of these factors affect arteriole size and peripheral resistance? • Lactic acid • Low PO2 • Cold • Histamine • Endothelin • Heat • NO • Adenosine

29. Blood Pressure BP = CO x PR Blood pressure = cardiac output × peripheral resistance

30. Question Tell whether the following statement is true or false. In patients with hypertension (high blood pressure), peripheral resistance is increased.

31. Answer True Rationale:In hypertension, blood vessels are constricted/narrowed. Smaller vessels increase resistance (it’s harder to push the same amount of fluid/blood through a tube that has become smaller).

32. Forces Moving Fluid In and Out of Capillaries

33. Lymph Vessels Carry Tissue Fluid Back to the Veins