Chapter 17 Control of Cardiovascular Function

1. Essentials of Pathophysiology Chapter 17Control of Cardiovascular Function

2. The left side of the heart pumps blood to the lungs. • The venous side of the circulation contains a larger portion of the blood volume than the arterial side. • The rate of blood flow through a vessel is affected by pressure, resistance, and vessel radius. • The loose-fitting sac that surrounds the heart is called the myocardium. • The rhythmic impulse of the cardiac conduction system is generated at the AV node and is known as the pacemaker of the heart. PRE LECTURE QUIZ (TRUE/FALSE) F T T F F

3. _______________ is the result of disorganized electrical activity in the atrium or the ventricle. • Cardiac _______________ is the amount of blood the heart pumps each minute and is defined by the formula SV × HR. • The _______________ are thin-walled, distensible, and collapsible vessels that are capable of enlarging and storing large quantities of blood. • The ______________ period of the cardiac cycle is marked by ventricular relaxation and filling. • The heart valve that controls the direction of blood flow from the right atrium to the right ventricle is called the _________________ valve. PRE LECTURE QUIZ Diastolic Fibrillation output Tricuspid veins

4. 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? Path of Blood Flow

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

6. Heart Anatomy Lungs

7. True or False. The pulmonary circulation moves blood through the left side of the heart. Question

8. 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. Answer

9. The Heart Layers

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

11. 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) The Basics of Cell Firing (cont.) Action potential Threshold potential Resting membrane potential Stimulus

12. 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 The Basics of Cell Firing (cont.) Action potential Threshold potential Resting membrane potential Stimulus

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

14. 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) Cardiac Muscle Firing (cont.) Action potential Threshold potential Resting membrane potential Calcium leak

15. 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 Cardiac Muscle Firing (cont.) Action potential PLATEAU Threshold potential Calcium leak

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

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

18. 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). Answer

19. The Cell Passes the Impulse to Its Neighbors Desmosomes link cells tightly together Gap junctions pass the electrical signal to the next cells

20. 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 Heart Contraction

21. Ventricles relax Blood entering atria Blood flows through AV valves into ventricles Semilunar valves are closed Cardiac Cycle—Diastole

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

24. Systole What happens in isovolumetric contraction?

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

26. 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. Answer

27. Discussion: • Arrange these steps in the proper order: 8–Ventricles relax 4–First heart sound 1–Systole 5–Semilunar valves open 10–Diastole3–AV valves close 9–AV valves open 6–Semilunar valves close 2–Ventricles contract 7–Second heart sound Cardiac Cycle

28. 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 (R) to fluid flow • Small vessels have more resistance • More viscous fluids have greater resistance Pressure, Resistance, Flow ΔP = Pin - Pout Flow, F= ΔP ÷ R

29. 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 Pressure, Resistance, Flow of Blood

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

31. BP = CO x PR Blood pressure = cardiac output × peripheral resistance How is this related to F=P/R ? Blood Pressure

32. Tell whether the following statement is true or false. In patients with hypertension (high blood pressure), peripheral resistance is increased.(Hint: P= F x R ) Question

33. 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). Answer

34. Forces Moving Fluid In and Out of Capillaries Higher Pressure from artery Lower Pressure of the veins

35. Lymph Vessels Carry Tissue Fluid Back to the Veins Interstitial fluid not recaptured in the capillaries enters the lymphatic system and ultimately reenters the blood at the subclavian vein