Your heart is a muscle that works continuously like a pump Each beat of your heart is set in motion by an electrical signal from within your heart muscle.

The Heart’s Electrical System

How Does Your Heart Beat?!?

The Electrical Conduction System

• Your heart is a muscle that works continuously like a pump

• Each beat of your heart is set in motion by an electrical signal from within your heart muscle

• The electrical activity can be recorded by an electrocardiogram (aka EKG or ECG)

SA node (sinoatrial node)• Each beat of your heart begins with an electrical

impulse from the sinoatrial node in the right atrium – A cluster of cells where electrical impulses are generated

• When you heart’s right atrium is full with blood, the electrical signal spreads across the cells of your heart’s right atria.

• Signal causes atria to contract or squeeze, forcing blood into the ventricles.

• The SA node sets the rate and rhythm of your heartbeat. – Known as the heart’s natural pacemaker.

SA node (sinoatrial node)

AV node (atrioventricular node)

• The signal arrives at the atrioventricular (AV) node between the atria and the ventricles.

• Here the impulse slows for an instant to allow your heart’s right AND left ventricles to fill with blood– Pumps the breaks!

AV node (atrioventricular node)

His-Purkinje Network

• The signal is released and moves to the bundle of His located in the heart’s ventricles.

• The signal fibers divided into left and right branches which run through the heart’s septum

The Bundle of His

His-Purkinje Network

• The signal leaves the left and right branches through the Purkinje fibers that connect directly to the walls of the heart’s ventricles

• The signal spreads quickly across your heart’s ventricles

Perkinje Fibers

His-Purkinje Network

• As the signal spreads, both ventricles contract, but not at exactly the same moment…– The left ventricles

contracts an instant before the right.• Right ventricle pushes

blood to the lungs• Left ventricle pushes blood

to the rest of the body

And we do it all over again!

• As the signal passes, the walls of the ventricles relax and await the next signal.

Label the ECG Diagram

How fast does the normal heart beat?

• How fast the heart beats depends on the body's need for oxygen-rich blood.

• At rest, the SA node causes your heart to beat about 50 to 100 times each minute.

• During activity or excitement, your body needs more oxygen-rich blood; the heart rate rises to well over 100 beats per minute.

Heart Rhythms on ECG

• The heart’s electrical system triggers the heartbeat. Each beat of the heart is represented on the electrocardiogram (EKG or ECG) by a wave arm.

The normal heart rhythm (normal sinus rhythm) shows the electrical activity in the

heart is following the normal pathway. The rhythm is regular and the node is normal (about 50 to 100 beats per minute).

Heart Rhythms on ECG

• Tachycardia: fast heart rhythm (greater than 100 beats per minute)

• Bradycardia: slow heart rhythm (less than 50 beats per minute)

What is an arrhythmia?

• An arrhythmia (also called dysrhythmia) is an irregular or abnormal heartbeat.

What causes arrhythmias?

• Coronary artery disease • High blood pressure • Changes in the heart muscle (cardiomyopathy) • Valve disorders • Electrolyte imbalances in the blood, such as

sodium or potassium • Injury from a heart attack • The healing process after heart surgery • Other medical conditions

What are the symptoms of an arrhythmia?

• Palpitations: A feeling of skipped heartbeats, fluttering, "flip-flops" or feeling that the heart is "running away"

• Pounding in the chest • Dizziness or feeling lightheaded • Shortness of breath • Chest discomfort • Weakness or fatigue

The Spark of Life

• http://www.pbs.org/wnet/heart/educators/video-spark.html

• http://www.pbs.org/wnet/heart/educators/video2-spark.html

• As you watch take note of the questions that accompany each clip and jot down your observations.

Types of Heart Arrhythmia Disorders

• Atrial Fibrillation• Atrial Flutter• Supraventricular

Tachycardia• Sick Sinus Syndrome• Ventricular Fibrillation• Ventricular Tachycardia• Premature Contractions• Heart Block

• You will each select one type of Heart Arrhythmia Disorders

• You will conduct research and create a presentation on one of the disorders:– Describe the disorder– What are the signs and

symptoms– What are the causes?– What remedies are there for

treating the disorder?