3. Cardiac muscle cells are rectangular shaped cells connected by regions called intercalated discs. The gap junctions, which are protein-lined tunnels, allow direct transmission from cell to cell, across the chambers of the heart, so that the cells contract in unison. The desmosomes hold the cardiac muscle cells together during contraction, induced by the sliding of the cardiac myofibrils. Sliding is regulated by the intracellular concentration of calcium ions released by the sarcoplasmic reticulum.

4.  Cardiac muscle is a type of involuntary striated muscle found in the walls and histological foundation of the heart.

5.  The heart cell muscles produces regular electrical impulses causing the muscle myofibrils to slide over one another and contract the cardiac muscle.  So the cells are helping the heart do their contractions, this is mainly called Cardiac

6.  http://www.astrographics.com/GalleryPri ntsIndex/GP2074.html http://www.astrographics.com/GalleryPri ntsIndex/GP2074.html  http://en.wikipedia.org/wiki/Myofibril http://en.wikipedia.org/wiki/Myofibril  http://users.rcn.com/jkimball.ma.ultranet /BiologyPages/M/Muscles.html#Cardiac Muscle