Electrical Conductivity of Heart Flashcards
What is an action potential (excitation signal) created by in the heart?
The sinoatrial (SA) node
What is the SA node?
A specialised clump of myocardial conducting cells located in the superior and posterior walls of the right atrium
What is the pacemaker of the heart?
The SA node
How is the impulse then spread to the AV node and myocardial contractile cells?
Via internodal pathways
What are the internodal pathways?
3 bands (anterior, middle, posterior) that lead directly from SA node to AV node
How do the cells of the AV node then transmit the action potential?
Transmit AP more slowly and delays impulse
As impulse spreads across both atria, what happens?
Atria contract –> atrial systole
Causes blood to move from atria to ventricles
What is purpose of delay caused by AV node?
Ensures atria have enough time to fully eject blood into ventricles before ventricular systole
After the AV node, where does the impulse then pass?
Into the atrioventricular bundle (bundle of His). The impulse spreads down to the ventricles along the bundle of His to the apex of the heart.
What is the bundle of His?
A continuation of the specialised tissue of the AV node and serves to transmit the electrical impulse from the AV node to the Purkinje fibres of the ventricles
At the apex of the heart, what does the bundle of His divide into?
The right bundle branch (RBB) and left bundle branch (LBB)
What is purpose of split into RBB and LBB?
Supplies left and right ventricles
What does RBB do?
Conducts the impulse to the Purkinje fibres of the right ventricle
What does the LBB do?
Conduct impulse to the Purkinje fibres of the left ventricle
What/where are Purkinje fibres?
Additional myocardial conductive fibres that spread impulse from AV to the myocardial contractile cells in the ventricles.Network of specialised cells that are abundant with glycogen and have extensive gap junctions.
