Purkinje fiber

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One of the specialized cardiac muscle fibers, part of the impulse-conducting network of the heart, that rapidly transmit impulses from the atrioventricular node to the ventricles.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun One of a group of fibers in the heart, consisting of specialized cardiomyocytes, that allow the heart's conduction system to create synchronized contractions of its ventricles and thus maintain a consistent rhythm.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a specialized cardiac muscle fiber that is part of the Purkinje network