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

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

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

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

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

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

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

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