1. Ch 13: Heart
concepts:

2. SLOs Distinguish between pulmonary and systemic circuits.
Trace a drop of blood through the heart and name all structures it passes by.
Describe the cardiac cycle and explain how the pressure differences in the heart chambers account for blood flow through the heart
Diagram EC coupling in cardiac muscle and compare it to EC coupling in skeletal muscle
Distinguish between myocardial contractile cells and myocardial autorhythmic cells. Diagram the mechanisms by which APs are generated in each cell type
Describe and trace the electrical conduction system.
Describe the components of the ECG and their relationships to the cardiac cycle.

3. 13.3 Structure of the Heart 2 circuits ... 4 chambers....
Fibrous skeleton
Fig

4. Pulmonary and Systemic Circulation
3 basic components: ?
The heart is a dual pump!

5. One way flow in heart is ensured by ?
AV = _______________________________ located between
Semilunar located between
Fig

6. Heart Sounds (HS) lub....dub...
1st HS: during early, isovolumetric ventricular contraction (= ________________)  AV valves close
2nd HS: during early ventricular relaxation (= ________________)  semilunar valves close

7. Stethoscope Positions for Heart Sounds
Heart Murmurs
Clinical Application
Abnormal, turbulent blood flow produces heart murmurs upon auscultation
Stethoscope Positions for Heart Sounds
Fig

8. Many Causes for Heart Murmurs
Defective heart valves:
Stenosis, e.g.: Mitral stenosis  consequences?
Incompetent valves  Insufficiencies, e.g.: Mitral valve prolapse  regurgitation (common)

9. Many Causes for Heart Murmurs cont.
Septal defects: Holes in interventricular or interatrial septa
Ductus arteriosus
Normal
Fig
Various pathogenic

10. 13.4 Cardiac Cycle

11. Mechanical Events of Cardiac Cycle
Systole (time during which cardiac muscle contracts)
atrial
ventricular
Diastole (time during which cardiac muscle relaxes)
Fig
Heart at rest: atrial & ventricular diastole
Completion of ventricular filling: atrial systole
Ejection: ventricular systole

12. Cardiac Muscle sSR smaller than in skeletal muscle, indicates ?
Fig
Heart muscle cells:
99% contractile
1% autorhythmic pacemaker cells
sSR smaller than in skeletal muscle, indicates ?
Abundant mitochondria

13. EC Coupling in Heart Muscle
Voltage-gated Ca-channels are not directly connected to Ca-channels in SR
Ca acts as 2nd messenger to open SR Ca-channels.
Calcium-induced calcium release
Fig 12-34

14. EC Coupling

15. 13.5 Electrical Activity of the Heart and the Electrocardiogram
Pacemaker or autorhythmic cells: Anatomically distinct from contractile cells
Spontaneous AP generation  Do not need ___________
Unstable resting membrane potential = pacemaker potential

16. Pacemaker potential starts at -60mV, slowly drifts to threshold
Fig 13.18
Heart Rate = Myogenic
Skeletal Muscle contraction = ?

17. Modulation of Heart Rate by ANS
ANS alters permeability of autorhythmic cells to different ions NE/E:  flow through If (HCN) and Ca2+ channels  Rate AND force contraction  Ach:  flow through K+ channels and  flow through Ca2+ channels  Heart rate 

18. Pacemaker sets HR
SA node firing rates set HR Why? If SA node defective? ___________: 50 bpm ventricular cells: 35 bpm 
Implant
mechanical
pacemaker!

19. APs in Contractile Myocardial Cells
Similar to skeletal muscle
Stable resting pot. ~ mV
Rapid depolarization due to voltage gated Na+ channels (Na+ movement?)
Repolarization due to voltage gated K+ channels (K+ movement?)
What is different?

20. Compare to Fig 13-19

21. Refractory Period and Summation of Skeletal Muscle

22. Refractory Period and Summation of Cardiac Muscle
Fig 13.21

23. Electrocardiogram ECG (EKG)
Reflects electrical activity of whole heart not of single cell!
Surface electrodes record electrical activity deep within body - How possible?

24. Signal very weak by time it gets to skin
EC fluid = “salt solution” (NaCl)  good conductor of electricity to skin surface
Signal very weak by time it gets to skin
ventricular AP = ? mV
ECG signal amplitude = 1mV
EKG tracing =  of all electrical potentials generated by all cells of heart at any given moment
(e)

25. Depolarization = signal for contraction
Since:
Depolarization = signal for contraction
Segments of EKG reflect mechanical heart events
Mechanical events
lag slightly behind
electrical events.
Fig

26. Components of EKG
Waves: P, QRS, T Segments: PR, ST Intervals = wave-segment combos: PR, QT

27. Net electrical current in
Why neg. tracing for
depolarization ??
Net electrical current in heart moves towards + electrode EKG tracing goes up from baseline
Net electrical current in
heart moves towards
- electrode
EKG tracing goes
Down from baseline

28. Einthoven’s Triangle and the 3 Limb Leads:RA LA LL I II
III – +
Fig 13.24

29. Relationships of EKG components
Info provided by EKG: HR
Rhythm
Relationships of EKG components
each P wave followed by QRS complex?
PR segment constant in length? etc.

30. For the Expert:
Find subtle changes in shape or duration of various waves or segments.
Indicates for example:
Change in conduction velocity
Enlargement of heart
Tissue damage due to ischemia (infarct!)

31. Normal and Abnormal EKGs
In depth study in lab
Analyze this abnormal ECG:

32. ECG, Pressures and Heart Sounds
The end