thaler chapter 1

1   The Basics

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Electrical Conducting Cells Electrical conducting cells are long, thin cells. Like the wires of an electrical circuit, these cells carry current rapidly and efficiently to distant regions of the heart. They are, in effect, the electrical highway of the heart. The electrical conducting cells of the ventricles form distinct electrical pathways. The ventricular conducting fibers constitute what is called the Purkinje system . The conducting pathways in the atria have more anatomic variability; prominent among these are fibers at the top of the intra- atrial septum in a region called Bachmann’s bundle that allow for rapid activation of the left atrium from the right. Actually, every cell in the heart has the ability to behave like a pace- maker cell. This so-called automatic ability is normally suppressed unless the dominant cells of the sinus node fail or if something in the internal or external environment of a cell (sympathetic stimula- tion, cardiac disease, etc. ) stimulates its automatic behavior. This topic assumes greater importance later on and is discussed under Ectopic Rhythms in Chapter 3.

Bachman’s bundle

Sinus node

Atrial conducting system Ventricular conducting system

The hard wiring of the heart.