8 / 56
16
1
The Basics
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.
Atrial
conducting
system
Ventricular
conducting
system
Sinus node
Bachman’s bundle
The hard wiring of the heart.