1. The Heart
Circuits
Chambers
Valves (one-way-flow)
Myocardiocytes

2. Volumes? Pressures? heart –> lungs –> heart
heart –> body –> heart
Volumes?
Pressures?

3. The Circulatory system is a "closed circulation"
Systemic
Circuit
Pulmonary
Circuit
Systemic
Circuit
Artery =
Vein =

5. Heart valves prevent back (retrograde)
The Heart has 4 Valves
Heart valves prevent back (retrograde)
flow of blood.
There are 2 atrioventricular valves (AV) –
found between the atria and ventricles.
1) Right AV (tricuspid) valve
2) Left AV (bicuspid/mitral) valve

6. There are 2 semilunar valves – found between the ventricle and the artery they leave,
1) Aortic semilunar valve
2) Pulmonary semilunar valve
Two heart sounds: “Lub” and “Dup”
1. Closure of AV valves = “Lub”
2. Closure of Semilunar valves = “Dup”

7. Disorders of Heart Valves
Stenosis -
Prolapse -
Can lead to abnormal Heart sounds,
e.g., heart murmurs.
Indicates: 1) turbulence
2) retrograde flow

12. stimulus

14. Graded Contraction of Heart
Force generated by myocardiocyte contraction is:
1. Proportional to amount of Calcium ions (Ca2+)
 [Ca2+] => more crossbridges, more force & speed.

16. Graded Contraction of Heart
Force generated by myocardiocyte contraction is:
1. Proportional to amount of Calcium ions (Ca2+)
 [Ca2+] => more crossbridges, more force & speed.
2. Modulated by Autonomic N.S.
=> Sym  HR and Force
=> Para  HR

17. Sympathetic – speeds heart rate by  Ca2+ influx.
Parasympathetic – slows rate by  K+ efflux,  Ca2+ influx.

18. Graded Contraction of Heart
Force generated by myocardiocyte contraction is:
1. Proportional to amount of Calcium ions (Ca2+)
 [Ca2+] => more crossbridges, more force & speed.
2. Modulated by Autonomic N.S.
=> Sym  HR and Force
=> Para  HR
3. Stretch-Length-Tension Relationship
 stretch, =>  Ca2+ entering =>  contraction force

19. Factors Influencing Stroke Volume

20. Electrical Conduction System
Sino Atrial (SA) Node
Atrial Ventricular (AV) Node
AV Bundle (of His)
L and R Bundle Branches
Purkinje Fibers

24. Mechanical Events of the Heart
The Cardiac Cycle
Mechanical Events of the Heart
Late Diastole: “Heart at rest” all chambers relaxed filling with blood (passive filling ~ 80% full).
2. Atrial Systole: atria contract, adds the last 20% of blood to ventricles (top off ventricles)
Occurs after P-wave on EKG
End Diastolic Volume (EDV) = Maximum ventricular volume

25. 3. Ventricular Systole (part 1):
Ventricular contraction begins - Pressure (P).
Closure of AV valves = 1st heart sound ("lub")
Sealed Compartment – all valves are closed.
Isovolumetric ventricular contraction:
=> pressure builds as volume stays the same.

26. 4. Ventricular Systole (part 2):
Ejection phase: P pushes open semilunar valves, blood forced out into artery leaving ventricle.
Pulmonary Semilunar => 25 mmHg (minimum pressure)
Aortic Semilunar => 80 mmHg (minimum pressure)
End Systolic Volume (ESV) = volume remaining in
heart after ejection (~½).
Stroke Volume = EDV - ESV (ml/beat)

27. The AV valves then open, refilling starts –
5. Ventricular Diastole:
Relaxation of ventricles, artery back flow slams semilunar valves shut = 2nd heart sound ("dup").
Sealed Compartment again – all valves are closed.
Isovolumetric ventricular relaxation:
=>  pressure as volume stays the same.
The AV valves then open, refilling starts –
back to start of cycle.

28. Break