Cardiac Physiology—Conduction Mechanisms of the Heart

Intrinsic System

A built in system (the His-Purkinje System or Thorel's Pathway)

Sinoatrial (SA) Node (Sinus Node)

Upper wall of right atrium, bunch of cells or osciator cells?

Responsible for atrial contraction

Body’s natural pacemaker

As it gets older, pacemaker can slow down

Atrioventricular (AV) Node

Impulse pause (0.1 seconds)

Generate its own electrical activity

Response for ventricular contraction

More powerful than SA

Can take over the rate of being pacemaker but there can be a lag time

Atrioventricular (AV) Bundle (of His)

Short pathway that enters the interventricular septum from right atrium

Bundle Branches

Form from splitting of AV bundle then move to each side of heart

Responsible for pumping each side of heart

Older people can develop bundle branch block, blockage in conductive pathway

Subendocardial Conducting Network (Purkinje Fibers)

These signals help the heart beat as a whole organ

Unify contraction process

Muscular folds are contracting as well

Extrinsic System

An external system of stimulation via the ANS

Extrinsic System

Sympathetic/Parasympathetic Fibers detect blood flow rate in heart, signal is set to nervous system to speed up or slow down beats, always feed back to nervous system

Extrinsic System

Blood pressure, heart rate, and blood flow are all going to rise when increase in activity and will go down when decrease in activity

Whole purpose is meeting the oxygen demands