1. Cardiovascular System: Heart
General Physiology
Tony Serino, Ph.D.
Biology Department
Misericordia University

2. Heart as a Dual Pump
Cardiac muscle arranged as whorls that squeeze the blood
Twin pumps: systemic and pulmonary
Four chambers: 2 atria and 2 ventricles

3. Cardiac Muscle Cells

4. Cardiac Muscle Depolarization

5. Depolarization and Tension

6. Fig
Allows for Ca++ plateau
12.17.jpg

7. Heart: Internal Anatomy

8. Cardiac Cycle (mechanical action)
Semilunar
valves
opened
Semilunar
valves closed
AV valves
closed
AV valves
closed
Systole: Period of isovolumic contraction.
Systole: Period of ejection.
Systole: Period of isovolumic contraction. Ventricular contraction causes the AV valves to close, which is the beginning of ventricular systole. The semilunar valves were closed in the previous diastole and remain closed during this period.

9. Systole: Period of ejection.
Systole: Period of ejection. Continued ventricular contraction pushes blood out of the ventricles, causing the semilunar valves to open.
Semilunar
valves opened
AV valves
closed
Systole: Period of ejection.
Semilunar
valves closed
AV valves
closed
Diastole: Period of isovolumic relaxation.

10. Semilunar
valves closed
AV valves
closed
Semilunar
valves closed
Diastole: Period of isovolumic relaxation.
Diastole: Period of isovolumic relaxation. Blood flowing back toward the relaxed ventricles causes the semilunar valves to close, which is the beginning of ventricular diastole. Note that the AV valves closed, also.
AV valves
opened
Diastole: Passive ventricular filling.

11. Diastole: Passive ventricular filling
Diastole: Passive ventricular filling. The AV valves open and blood flows into the relaxed ventricles, accounting for most of the ventricular filling.
Semilunar
valves closed
AV valves
opened
Diastole: Active ventricular filling.
Semilunar
valves closed
AV valves
opened
Diastole: Passive ventricular filling.

12. Semilunar
valves closed
AV valves
closed
Systole: Period of isovolumic contraction.
Semilunar
valves closed
AV valves
opened
Diastole: Active ventricular filling. The atria contract and complete ventricular filling.
Diastole: Active ventricular filling.

13. Conduction System of Heart
1. Action potentials originate in the sinoatrial (SA) node and travel across the wall of the atrium (arrows) from the SA node to the atrioventricular (AV) node.
Sinoatrial (SA) node
Left atrium
Atrioventricular (AV) node 1
2. Action potentials pass through the AV node and along the atrioventricular (AV) bundle, which extends from the AV node, through the fibrous skeleton, into the interventricular septum. 2
Atrioventricular (AV) bundle
3. The AV bundle divides into right and left bundle branches, and action potentials descend to the apex of each ventricle along the bundle branches.
Left
ventricle 3
Purkinje fibers
Left and Right bundle branches 4
4. Action potentials are carried by the Purkinje fibers from the bundle branches to the ventricular walls.
Apex

14. Pacemaker Potential

15. Control of Pacemaker
12.23.jpg

16. ECG Correlates Electrical Events
12.11.jpg

17. Normal ECG

18. ECG Leads
12.15a.jpg
Einthoven’s Triangle

19. ECG
Normal Sinus Rhythm
Junctional Rhythm (AV node rhythm)

20. Second Degree Heart Block
Ventricular Fibrillation (V-fib)

21. Fig
12.16.jpg

22. Heart Sounds “Lub-dub”
Sound associated with valve closing producing turbulent blood flow

23. 12.22.jpg

24. Cardiac Cycle

25. (ml/min)

26. Factors Affecting SV
Stroke Volume (SV) = End Diastolic Volume – End Systolic Volume
SV = EDV – ESV (ml/beat)
EDV affected by:
Venous return which is dependent on venous tone, skeletal muscle pumps, etc.
ESV
As the heart fills it is stretched which allows for better overlap of the contractile proteins which will affect the force of contraction and the ESV (Starling’s Law of the Heart)
Increasing the force of contraction at any EDV will decrease the ESV and increase the SV (sympathetic stimulation and epinephrine)

27. EDV is affected by Venous Return
12.25.jpg

28. At any EDV, increased force of contraction will increase SV
12.26.jpg

29. As the heart fills, the muscle is stretched allowing for better overlap of contractile proteins which increases force of contraction
(↓ESV)

30. Sympathetic Stimulation
Leads to increase HR
Increases in Ca++ release from SR, increase Ca++ through membrane and increase myosin crossbridge cycling
Increases force of contraction

31. Heart Rate Control Sinus Rhythm = normal SA node control
Autonomic Activity
Sympathetic = accelerator (tachycardia)
Parasympathetic = brake (bradycardia)
Hormones
epinephrine
Drugs -caffeine, nicotine, atropine, etc.

32. Summary
↑ stretch
↑ Contraction Strength
12.28.jpg

33. CV Effects during Exercise

34. Exercise Benefits
Heart’s maximums are increased
Effort is decreased

35. Fig
12.07.jpg

36. 12.09.jpg