The Cardiac Cycle and Conduction System

The Cardiac Cycle and Conduction System

Cardiac conduction system

Heart’s power supply

·     Heart can generate own electrical impulses

·     Control route of impulses via conduction pathway (dominoes)

·     pathway made up of 5 elements

o   sino-atrial (SA) node

o   atrio-ventricular (AV) node

o   bundle of His

o   left and right bundle branches

o   Purkinje fibre

SA Node

·     Pacemaker

·     Releases regular electrical impulses

·     Rate dictated by needs of body

·     Impulse pass through myocardial cells of atria àrapid wave of contraction 

AV Node

·     Impulse reaches AV node

·     Pause to allow ventricular filling

·     When filling complete and AV valves closed

o   Impulses passes through AV node

o   Bundle of His

o   Bundle branches (motorways)

o   Purkinje fibres (A and B roads)

Recharge (repolarisation)

·     SA and AV node can only accommodate one impulse at a time

·     Need to recharge 

o   SA node recharges whilst atria filling 

o   AV node…