1. Control of Heart Contractions
What property is unique to cardiac muscle??
It can create it’s own stimulus
Conduction System of the heart because it “conducts” an impulse causing the heart to beat

2. Control of Heart Contractions
SA (sinoatrial) NODE = PACEMAKER
It is the conductor of the heart
Located in right atrium
SA node sends out electrical impulse
Impulse spreads over atria, making them contract
Travels to AV Node

3. Control of Heart Contractions
AV (atrioventricular) NODE
Conducting cell group between atria and ventricle
“relay station”
Carries impulse to bundle of His

4. Control of Heart Contractions
BUNDLE OF HIS
Conducting fibers in septum
At bottom of septum, bundle divides into R and L branches
These branches run back up the sides of the ventricles
These branches are called the Purkinje fibers
Impulse shoots along Purkinje fibers causing ventricles to contract

5. Control of Heart Contractions
ELECTROCARDIOGRAM (EKG or ECG)
Device used to record the electrical activity of the heart.
Baseline of EKG is flat line

6. Control of Heart Contractions
ARRHYTHMIA – any change from normal heart rate or rhythm
Normal pulse range Average pulse= 72
BRADYCARDIA – slow heart rate
(< 60 bpm)
TACHYCARDIA – rapid heart rate
(>100 bpm)

7. Control of Heart Contractions
Conduction defect any interruption of the signal from the SA node to the AV node
Ectopic pacemaker an abnormal signal generated in heart tissue other than the SA node
What might these people need?
Artificial pacemaker
Ectopic pacemakers can cause:
Premature atria contractions and
Premature ventricular contractions

8. Control of Heart Contractions
The worst arrhythmia is called:
VENTRICULAR FIBRILLATION
The heart “quivers” like jello
What treatment must be provided???
You must “defibrillate” them
or use the paddles and shock them