1. Chapter 15.4: Electrocardiogram

2. Electrocardiogram (ECG/EKG)
A recording of electrical changes in a heartbeat
Action potentials generate measurable electrical currents
Three waves (changes in electrical current):
P Wave
QRS Complex
T Wave

3. EKG Waves P wave QRS Complex T Wave Atrial depoloarization
Seconds
Millivolts (mV)
EKG Waves
P wave
Atrial depoloarization
Action potential moving throughout atria
Initiates atrial contraction
QRS Complex
Ventricular depolarization
Action potential spreading through ventricles
Initiates ventricular contraction
T Wave
Ventricular repolarization
Occurs just before ventricle relaxation

5. Chapter 15.5: The Cardiac Cycle

6. Cardiac Cycle All of the events associated with one heart beat
Three main events:
Relaxation (diastole) period
All 4 chambers relaxed
Ventricles repolarizing (T-Wave)
AV valves open and 75% of blood empties into ventricles 1
Relaxation
period 3
Ventricular
systole 2
Atrial
systole

7. Cardiac Cycle Three main events: 2) Atrial systole (contraction)
- Both atria contract
- Occurs right after P-Wave
- Forces last 25% of blood into ventricles
3) Ventricular systole (contraction)
- Both ventricles contract
- Occurs right after QRS Complex
- Pushes blood out of the ventricles 1
Relaxation
period 3
Ventricular
systole 2
Atrial
systole

9. Heart Sounds Caused by closing of valves
Lubb: a long, booming sound from AV valves closing
Occurs right as ventricular systole begins
Dupp: the second, short and sharp sound from SL valves closing
Occurs at the end of ventricular systole