Myocardial cells communicate using autocrine factors, cell to cell propagation of depolarization fronts, gap junctions and adhesion complexes. The autocrine communications involved an abundant array of secretions from leptin, FGF and TGFβ family members, midkine, hepatocyte growth factor, endothelin-1, and stromal cell–derived factor 1α, which causes the myocardial cell communications.
Adhesion complexes engage in cell to cell communication with intracellular signaling that are activated by cell to cell or cell to matrix action of specific protein in the complexes. This signal results in in the myocardial reactions to growth being changed to control cardiac development and hypertrophy.
Intercalated discs are made up of two types of cell junctions: desmosomes and gap junctions. Desmosomes comprises of strong protein fibers that are very tough and securely connects the myocardial cells together. This is a significant characteristic because of the continuous pumping of the heart results in an immense amount of pressure for the networks between the cells. Myocardial cells are stimulated to create electric current that can instigate and transmit action potentials. The transmission of action potential from one myocardial cell to another myocardial cell follows the transfer of sodium ions across the gap junction or can be referred to as an electric synapse. Gap junctions connect the cytoplasm of a cell to bordering cells by small linking tubes called connexins, which allows miniature molecules and ions to easily move from one myocardial cell to another. Myocardial cells are branched and joined with other myocardial cells hence together with the gap junctions at the intercalated discs, an high intensity of correlations between the myocardial cells are produced. The myocardial cells linked to the gap junctions are all together known as a myocardium which functions as one. The entire myocardium contracts together when it is stimulated.
A myocardium is made up of two ventricles and another myocardium is from by two atria. The ventricles and the atria are dived by non-conducting fibrous skeleton. The simultaneous contraction of the myocardial cells which comprises the myocardium is essential to generate the force vital to allow pumping of blood.
“Cell Communications in the Heart .” Circulation . Accessed October 18, 2013.http://circ.ahajournals.org/content/122/9/928.full#sec-1
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