Which fibers are responsible for contraction when receiving electrical impulses?

The correct answer is the Purkinje fibers. These specialized conduction fibers are part of the heart’s electrical conduction system and are crucial for maintaining synchronous contractions of the heart muscle. They are responsible for transmitting electrical impulses rapidly throughout the ventricles, ensuring that they contract in a coordinated manner after receiving signals from the atria.

While cardiac myocytes are the muscle cells that actually contract when stimulated, Purkinje fibers specifically facilitate the rapid distribution of electrical impulses that trigger this contraction. The atrioventricular nodes play a role in the conduction of electrical signals but do not directly cause contraction; instead, they delay the signal before passing it to the ventricles. Epithelial cells do not function in muscle contraction but instead serve various roles in protection and secretion within the body. This context helps clarify the unique function of Purkinje fibers in the heart's contraction process.