In what ways are autorhythmic fibers similar to and different from contractile fibers?anatomy-Heart

The source of the rhythmical electrical activity that
makes up the heart's lifelong beat is found in autorhytmic fibers. These fibers
"repeatedly generate action potentials that trigger heart contractions. They continue to
stimulate a heart to beat even after it is removed from the body," because unlike
contractile fibers, they are self excitable and do not require neural stimulation to
trigger contractions. "Autorhythmic fibers form the conduction system, cardiac muscle
fibers that spontaneously depolarize and generate action potentials." (p.
726)

Unlike
autorhythmic fibers, contractile
fibers have a stable resting membrane potential
that is close to - 90 mV. When a contractile fiber is brought to threshold by an action
potential from neighboring fibers, its voltage-gated fast Na+ channels open. (p.
728)

Source: Anatomy and
Physiology: From Science to Life, 2nd Edition Gail Jenkins (Montgomery College ),
Christopher Kemnitz (Lake Superior College ), Gerard J. Tortora (Bergen Community
College) January 2009, ©2010

Chapter 20: The Cardiovascular
System: The Heart