The Nikon MicroscopyU confocal microscopy image gallery was created with a PCM-2000 confocal scanning system interfaced to a Nikon Eclipse E600 upright microscope. Images were recorded in successive z-axis serial sections with C-Imaging Systems software with excitation illumination provided by an argon-ion and/or a helium-neon laser.

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Purkinje fibers are heart muscle tissues that are specialized to conduct electrical impulses to ventricular cells, which induce the lower chambers of the heart to contract. Enveloped in a small amount of delicate connective tissue, these electroconductive fibers are imbedded in regular cardiac muscle. Purkinje fibers are comprised of very large heart cells that are modified to rapidly transmit electrical impulses (action potentials) at a velocity of about five times greater than normal cardiac muscle.

These nerve-like conduits receive impulses from a modified muscle structure called the atrioventricular node. Impulses from the upper chambers of the heart are relayed by this node to large bundles of Purkinje fibers referred to as the Bundle of His. These bundles branch into smaller elements and eventually form terminal ends that burrow into left and right ventricular chamber muscles. As the impulse is passed to the ventricles, the muscles contract and pump blood. The contraction caused by the specialized fibers begins from the bottom of the ventricles and move upwards so that the blood leaves the lower chambers through the pulmonary arteries and the aorta.