1. Chapter 20, part 4
The Heart

2. Factors Affecting Heart Rate
Autonomic innervation
Cardiac reflexes
Tone
SA node
Hormones
Epinephrine (E), norepinephrine(NE), and thyroid hormone (T3)
Venous return

3. Figure 20.20 Factors Affecting Cardiac Output

4. Medulla Oblongata centers affect autonomic innervation
Cardioacceleratory center activates sympathetic neurons
Cardioinhibitory center controls parasympathetic neurons
Receives input from higher centers, monitoring blood pressure and dissolved gas concentrations

5. Figure 20.21 Autonomic Innervation of the Heart

6. Figure 20.21 Autonomic Innervation of the Heart

7. Basic heart rate established by pacemaker cells
SA node establishes baseline
Modified by ANS
Atrial reflex

8. Figure 20.22 Pacemaker Function

9. Figure 20.22 Pacemaker Function

10. Factors Affecting stoke volume
EDV
Frank-Starling principle
ESV
Preload
Contractility
Afterload

11. Figure 20.23 Factors Affecting Stroke Volume

12. Figure 20.23 Factors Affecting Stroke Volume

13. Autonomic Activity Sympathetic stimulation Positive inotropic effect
Releases NE
Parasympathetic stimulation
Negative inotropic effect
Releases ACh

14. Exercise and Cardiac Output
Heavy exercise can increase output by percent
Trained athletes may increase cardiac output by 700 percent
Cardiac reserve
The difference between resting and maximal cardiac output
PLAY
Animation: Cardiac cycle

15. Summary: Regulation of Heart Rate and Stroke Volume
Sympathetic stimulation increases heart rate
Parasympathetic stimulation decreases heart rate
Circulating hormones, specifically E, NE, and T3, accelerate heart rate
Increased venous return increases heart rate
EDV is determined by available filling time and rate of venous return
ESV is determined by preload, degree of contractility, and afterload

16. Figure 20.24 A Summary of the Factors Affecting Cardiac Output

17. SECTION 20-5 The Heart and the Cardiovascular System

18. The heart is part of the cardiovascular system
The goal of the cardiovascular system is to maintain adequate blood flow to all body tissues
The heart works in conjunction with cardiovascular centers and peripheral blood vessels to achieve this goal

19. You should now be familiar with:
The organization of the cardiovascular system.
The location and general features of the heart, including the pericardium.
The differences between nodal cells and conducting cells as well as the components and functions of the conducting system of the heart.
The electrical events associated with a normal electrocardiogram.

20. You should now be familiar with:
The events of the cardiac cycle including atrial and ventricular systole and diastole, and the heart sounds related to specific events in the cycle.
Cardiac output, heart rate and stroke volume and the factors that influence these variables.
How adjustments in stroke volume and cardiac output are coordinated at different levels of activity.