Anatomy & Physiology: Cardiac Conduction System
What do the purkinje fibers do?
Carry impulses to the ventricular myocardium, allowing the ventricular myocardium to contract as a unit.
What causes electrical changes in the myocardium during a cardiac cycle?
Depolarization and repolarization as action potential occurs in the contracting cardiac muscle fibers.
What is an EEG pattern do?
It allows physicians to assess the heart's ability to conduct impulses.
What happens when an impulse reaches the distal end of the A.V. node?
It reaches the A.V. bundle, which devides into a left and right branches in the interventricular septum.
What is baseline on a electrocardiogram?
No detectable electrical changes, the muscle fibers remained polarized.
What is the P wave on an electrocardiogram?
Shows depolarization of the atrial fibers just before they contract, and is caused by S.A. node triggering an impulse.
What are the eight steps of a nerve impulse path?
The S.A. node, the atrial syncytium, the A.V. node, the A-V. node, the A.V. bundle, the right and left A.V. bundle branches, the purkinje fibers, and the ventricular synctium.
What is responsible for the rhythmic contractions of the heart (often referred to as the pacemaker)
The S.A. node.
Where do purkinje fibers transmit impulses to first?
The apex of the heart.
What is the path of a cardiac impulse from the S.A. node?
The atrial syncytium, fibers that are continuous with the atrial muscle fibers, A.V. node, which is located in the inferior portion of the atrioventricular septum.
What happens the the A.V. bundle about half way down the interventricular septum?
The branches give rise to enlarged purkinje fibers.
What is the QRS complex on an electrocardiogram?
The complex that appears due to depolarization of the ventricular fibers prior to the contraction of the ventricular walls.
What is the T wave on an electrocardiogram?
The wave that occurs as the ventricular muscle fibres repolarize, this is the end of the ECG pattern.
What happens in A.V. nodes?
Transmissions of impulses are delayed, allowing time for the atria to fully empty and the ventricles to fill with blood.
