unit 4 - excitation pathway

How many main structures make up the heart's excitation pathway?

5

What is the main pacemaker of the heart?

The sinoatrial (SA) node.

What does the SA node contain?

The largest collection of neural tissue in the heart.

What pace or rhythm can the SA node generate?

~75 BPM = sinus rhythm

How does the SA node depolarize compared with the rest of the myocardium?

faster than any part of the myocardium.

What is the role of the atrioventricular (AV) node as a pacemaker?

pacemaker, but not the main one

How does the AV node compare with the SA node in neural cells and gap junctions?

fewer neural cells, fewer gap junctions, and smaller-diameter fibers.

What pace or rhythm can the AV node generate?

~50 BPM = junctional rhythm

What effect does the AV node have on the electrical signal?

causes a delay in the signal.

How much delay does the fibrous skeleton cause?

~ 0.1 seconds

What is the Bundle of His?

structure that connects the atria to the ventricles.

What is the function of the right and left bundles?

each bundle sends an electrical signal to its corresponding ventricle.

What are Purkinje fibers?

Fibers that innervate the ventricles and are responsible for ventricular contraction.

How fast do Purkinje fibers depolarize in the absence of signals from the AV node?

~30/min