1. Heart Function – Cardiac Cycle and the Electrocardiogram (ECG)

2. Pathway of Blood – Pulmonary and Systemic Circuits
R. Atrium
R. Ventricle
Pulmonary Artery
TCV
PSLV
Vena Cava
Lungs
Aorta
ASLV
BCV
L. Ventricle
L. Atrium
Pulmonary Vein
Pathway of Blood – Pulmonary and Systemic Circuits

3. Cardiac Cycle
All the changes that occur during one heartbeat – one cycle of contraction/ relaxation (systole/diastole)
Measurable changes include:
Pressure
Volume
Heart sounds
Electrical impulses
Blood flows through the heart based on pressure differences
Pressure differences caused by changes in volume
Changes in volume caused by heart contractions
Heart contractions caused by depolarization of muscle cells

4. Cardiac Cycle Electrical Changes Contraction Volume Change
Cause Contraction
Contraction
Decreases Volume
Volume Change
Increases Pressure
Pressure Change
Opens Valve
Blood Moves
High to Low Pressure

5. Cardiac Cycle Systole = contraction Diastole = relaxation
Atrial Systole = atrial contraction
atrial pressure > ventricular pressure
AV valves open
semi-lunar valves close
Ventricular Systole = ventricular contraction
ventricular pressure > atrial pressure
semi-lunar valves open
AV valves close

6. Cardiac Cycle
Describe the pressure graph using time and phase
Describe the volume graph using time and phase
Describe the ECG graph using time and phase
Describe the heart sound graph using time and phase
Figure 13.10

7. Cardiac Cycle Click here for video clip of Cardiac Cycle
Click here for a video clip of a normal heart beat

8. Heart Conduction System
Intrinsic Conduction (conduction from within)
Heart contractions occur independently of the nervous system.
Electrical stimulation begins in the SA node, the ‘pacemaker’.
The electrical pathway:
SA node AV node Right and Left Bundle Branches Purkinje Fibers
Figure 13.11

9. Heart Conduction System
Click here for video clip of Heart Conduction System

10. Heart Conduction System
How an Impulse is Conducted-The Action Potential
Outside cell
1. Heart Muscle Cell--Polarized
Inside cell
Outside cell
Heart Muscle Cell--Depolarized
*caused by movement of ions
*When cells depolarize, they contract.
*When many cells depolarize, the heart contracts.
3. Heart Muscle Cell –-(Re)polarized

11. The Electrocardiogram (ECG)
Measures electrical conduction throughout the cardiac cycle
Works by measuring electrical changes of de- and re-polarization
Sequence:
Atria contract (de-)
Atria relax (re-)
Ventricles contract (de-)
Ventricles relax (re-)
Figure 13.14

12. The Electrocardiogram (ECG)
Abnormal ECG’s
Figure 13.15

13. ECG and Cardiac Cycle
Click here for a video clip of a normal heart beat
Click here for a video clip of an abnormal heart beat – ventricular fibrillation