1. Chapter 17 Control of Cardiovascular Function
Essentials of Pathophysiology
Chapter 17 Control of Cardiovascular Function

2. PRE LECTURE QUIZ (TRUE/FALSE)
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. F T

3. PRE LECTURE QUIZ
Diastolic
Fibrillation
output
Tricuspid
veins
_______________ 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.

4. 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?

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

6. Heart Anatomy
Lungs

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

8. 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.

9. The Heart Layers

10. 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 (less Negative)
Threshold potential
Resting membrane potential
Stimulus

11. 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

12. 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

13. 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

14. 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

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

16. 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

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

18. 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).

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. 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

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

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

24. What happens in isovolumetric contraction?
Systole
What happens in isovolumetric contraction?

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

26. 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.

27. Cardiac Cycle Discussion: Arrange these steps in the proper order:
8– Ventricles relax 4– First heart sound
1– Systole 5– Semilunar valves open
10–Diastole 3– AV valves close
9– AV valves open 6– Semilunar valves close
2– Ventricles contract 7– Second heart sound

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

29. 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

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

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

32. Question
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 )

33. 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).

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