The Heart: Conduction The Heart: Conduction SystemSystem

►The heart pumps blood through the body The heart pumps blood through the body

►This is accomplished by contraction and This is accomplished by contraction and relaxation of the cardiac muscle tissue in relaxation of the cardiac muscle tissue in the myocardium layer.the myocardium layer.

► Intercalated discs allow impulses to travel Intercalated discs allow impulses to travel rapidly between adjacent cells so they rapidly between adjacent cells so they function as one rather than individual cellsfunction as one rather than individual cells

Cardiac Muscle TissueCardiac Muscle Tissue

intercalated disc

intercalated disc

Conduction System Conduction System Continued….Continued….

►Cardiac conduction systemCardiac conduction system:: The The electrical conduction system controls electrical conduction system controls the heart rate the heart rate

►This system creates the electrical This system creates the electrical impulses and sends them throughout impulses and sends them throughout the heart. These impulses make the the heart. These impulses make the heart contract and pump blood. heart contract and pump blood.

Heart ContractionHeart Contraction

Components of the Conduction Components of the Conduction SystemSystem

►Sinoatrial NodeSinoatrial Node (Part I): (Part I): located in back wall of the right atrium located in back wall of the right atrium

near the entrance of vena cavanear the entrance of vena cava initiates impulses 70-80 times per minute initiates impulses 70-80 times per minute

without any nerve stimulation from brainwithout any nerve stimulation from brain establishes basic rhythm of the heartbeatestablishes basic rhythm of the heartbeat called the called the pacemakerpacemaker of the heart of the heart impulses move through atria causing the impulses move through atria causing the

two atria to contract. two atria to contract. at the same time, impulses reach the at the same time, impulses reach the

second part of the conduction systemsecond part of the conduction system

Components of the Conduction Components of the Conduction System Continued ….System Continued ….

►Atrioventricular NodeAtrioventricular Node (Part II): (Part II): located in the bottom of the right atrium located in the bottom of the right atrium

near the septum near the septum cells in the AV node conduct impulses cells in the AV node conduct impulses

more slowly, so there is a delay as more slowly, so there is a delay as impulses travel through the nodeimpulses travel through the node

this allows time for atria to finish this allows time for atria to finish contraction before ventricles begin contraction before ventricles begin contractingcontracting

Septum

Atrioventricular BundleAtrioventricular Bundle► A.K.A. “A.K.A. “Bundle of Bundle of

HisHis”” From the AV node, From the AV node,

impulses travel impulses travel through to the right through to the right and left and left bundle bundle branches branches

These branches These branches extend to the right extend to the right and left sides of the and left sides of the septum and bottom septum and bottom of the heart.of the heart.

Atrioventricular Bundle Atrioventricular Bundle Continued….Continued….

These branch a lot to These branch a lot to form the form the Purkinje fibersPurkinje fibers that transmit the that transmit the impulses to the impulses to the myocardium (muscle myocardium (muscle tissue)tissue)

The bundle of His, bundle The bundle of His, bundle branches and Purkinje branches and Purkinje fibers transmit quickly fibers transmit quickly and cause both ventricles and cause both ventricles to contract at the same to contract at the same timetime

Like a “phone tree”Like a “phone tree”

Atrioventricular Bundle Atrioventricular Bundle Continued….Continued….

►As the ventricles contract, blood is As the ventricles contract, blood is forced out through the semilunar forced out through the semilunar valves into the pulmonary trunk and valves into the pulmonary trunk and the aorta.the aorta.

►After the ventricles complete their After the ventricles complete their contraction phase, they relax and the contraction phase, they relax and the SA node initiates another impulse to SA node initiates another impulse to start another cardiac cycle.start another cardiac cycle.

1 - Sinoatrial node (SA node) 2 - Atrioventricular node (AV node) 3 – Bundle of His 4 - Right & Left Bundle Branches which lead to Purkinje Fibers