Intrinsic Conduction System

• specialized cells of the heart that pace contractions and coordinate how parts of the heart work together

Automaticity

• Cells of the intrinsic conduction system spontaneously depolarize on their own.

  • loop that keeps resetting itself

  • occurs due to a regular sodium ion (Na+) leak. These cells slowly depolarize and reach threshold regularly.

Functional Syncytium

• all parts of the heart are working together to coordinate and optimize blood movement.

  • the heart has to contract with the correct timing.

  • this is the overall product of the intrinsic conduction system

Parts of the Intrinsic Conduction System

• Sinoatrial (SA) Node

  • the Pacemaker of the heart

  • fires electrical pulses that go to the atria to cause it to contract

• Atrial Conduction Fibers

  • send action potentials through the atria

• Atrioventricular (AV) Node

  • Delays the action potential briefly

  • sits between the atria and the ventricle

  • then conducts it over to the center of the heart

• AV Bundle

  • takes action potential to interventricular septum (wall between the two ventricles)

• Bundle Branches

  • takes action potential to apex (the bottom of the heart)

• Purkinje Fibers

  • takes action potential to myocardium of ventricles

  • makes the muscle of the ventricles contract

An EKG can help us look at parts of the Intrinsic Conduction System

• if something is off with the P wave it means it has something to do with the SA node or the Atria

• if something is off with the QRS complex it means it has something to do with the AV bundle—> Purkinje fibers