1. BIO 265 – Human A&P
Chapter 18
The Heart

2. The Heart Size Form Location – mediastinum
Figure 18.1 and from other text

3. Heart Anatomy
Pericardium (pericardial sac)
Figures 18.1 and 18.2

4. Heart Anatomy
Heart Wall
Epicardium
Myocardium
Endocardium
Figure 18.2

5. Heart Structure and Function
What are the heart chambers?
Overview of heart function
Figure 18.5

6. Coronary Circulation
In order for the heart to function, it must have a constant supply of oxygen
The coronary arteries carry the blood to the heart
Figure 18.7

7. Heart Attack What is a heart attack or myocardial infarction?
CD Animation

8. Heart Valves
What are the 4 valves in the heart?
Figure 18.8

9. Heart Valves
Heart valve function – Figures 18.9 and 18.10

10. Heart Valves Heart sounds result from the closing of the heart valves
Heart murmurs occur when a valve does not open or close properly
CD Animation

11. Histology What are the characteristics of cardiac muscle?
Branched fibers
Mitochondria
T-tubules
Intercalated disks with gap junctions
Figure 18.11

12. Conducting System
What are the components?
Figure 18.14

13. Conducting System All cardiac muscle cells are autorhythmic
They can generate spontaneous AP
But the SA node is the pacemaker (it depolarizes faster than other areas of the heart)
Figure 18.13

14. Conducting System
Once the AP is generated it spreads through the atria to the AV node
What role does the AV node play?
Delays the AP for a split second
The AP then passes very quickly through the bundle branches
The effect is contraction at the apex first
Figure 18.14

15. Electrical Properties
Cardiac muscle has an RMP similar to skeletal muscle
Differences between cardiac and skeletal AP – Figure from other text

16. Cardiac Action Potentials
Phases of AP in contractile cells:
Depolarization
Na+ channels (fast channels) open
K+ channels are closed
Ca2+ channels (slow channels) begin to open
Early repolarization and plateau
Na+ channels close
Some K+ channels open
Ca2+ channels stay open
Figure from other text

17. Cardiac Action Potentials
Final repolarization
Ca2+ channels close
many K+ channels open
Figure from other text

18. Cardiac Action Potentials
How would the AP in cardiac muscle stimulate a contraction?
Notice that Ca2+ comes from the extracellular fluid as well as the SR
Cool CD Animations! (my CD)

19. Electrocardiogram
ECG wave patterns – Figures 18.16, 18.17, and 18.18

20. The Cardiac Cycle
The cardiac cycle refers to the repetitive pumping process that occurs in the heart
Systole – contraction of the heart
Diastole – relaxation of the heart
CD animation

21. The Cardiac Cycle Steps: Ventricular filling Ventricular Systole
Passive – during complete diastole
Active – during atrial systole
Ventricular Systole
Isovolumetric Contraction – closes AV valves and opens semilunar valves
Period of Ejection – blood leaves the ventricles
Ventricular Diastole
Isovolumetric relaxation – semilunar valves close
Figure 18.20

22. The Cardiac Cycle Assuming an average 75 bpm:
Cardiac Cycle = 0.8 s
Atrial systole = 0.1 s
Ventricular systole = 0.3 s
Diastole = 0.4 s
Awesome CD animation (my CD)

23. Cardiac Output Cardiac output (CO) = Calculations (p.698)
Heart rate (HR) x Stroke volume (SV) of one ventricle
Calculations (p.698)
Resting 75 bpm x 70 ml/beat = 5250 ml/min
Or in other words your entire volume of blood passes through each side of your heart each minute!!!
Exercise 20 liters/min to 35 liters/min

24. Regulation of the Heart
Regulation of cardiac output is critical for homeostasis
Starlings law of the heart:
The greater the venous return to the heart,
The greater the stretch of the heart wall,
This results in a more forceful contraction and therefore a greater stroke volume

25. Regulation of the Heart
Neural regulation:
The heart is innervated by both sympathetic and parasympathetic fibers
Parasympathetic – decrease heart rate by releasing acetylcholine
It opens ligand-gated K+ channels
Effect?
Figure 18.15

26. Regulation of the Heart
Sympathetic – increases heart rate and force of contraction (stroke volume)
Norepinephrine (a neurotransmitter) stimulates the opening of the slow Ca2+ channels
It works through a G-protein system that synthesizes cAMP
Figures and 18.15

27. Regulation of the Heart
Hormonal Control
Epinephrine and norepinephrine – same effect as above
Problems in Regulation:
Tachycardia – over 100 bpm
Bradycardia – under 60 bpm (can be normal in athletes)

28. Regulation of the Heart
Congestive Heart Failure – cardiac output is too low to meet body tissue needs
Blood builds up in the veins (causing the “congestion”)
Causes:
Coronary Atherosclerosis – decreases the hearts pumping ability
Hypertension (high blood pressure) – ventricles can’t push the blood out into the arteries
Myocardial infarction

29. Heart and Homeostasis How does the heart help maintain homeostasis?
Blood pressure example
Baroreceptors, the cardioregulatory center, and nerves
Figures from other text

30. The Fetal Heart
There are some interesting differences between the fetal and adult hearts
Why?
Foramen ovalis in the atrial septum
Ductus arteriosis between the pulmonary trunk and the aorta
Figures 18.4b and e