Functional Syncytium and Cardiac Muscle

[Michael L Miller]

Star asked a few days ago why muscles were true syncytium, whereas cardiac muscles were functional syncytium, since in cardiac muscle, cells are not completely fused together, but instead communicate via gap junctions (at the intercalated disks).

I suggested it had something to do with regulation, insomuch that the functional states of gap junctions were not fixed, and could therefore be regulated (this happens frequently in nerve cells that are electrically coupled).  Here is further explanation from Wikipedia:

"Microscopically, the wave of depolarization propagates to adjacent cells via gap junctions located on the intercalated disk. The heart is a functional syncytium (not to be confused with a true "syncytium" in which all the cells are fused together, sharing the same plasma membrane as in skeletal muscle). In a functional syncytium, electrical impulses propagate freely between cells in every direction, so that the myocardium functions as a single contractile unit. This property allows rapid, synchronous depolarization of the myocardium. While normally advantageous, this property can be detrimental as it potentially allows the propagation of incorrect electrical signals. These gap junctions can close to isolate damaged or dying tissue, as in a myocardial infarction."

Thank you,

Michael L. Miller
Graduate Student, MSTP

Graduate School of Biological Sciences,
Mt. Sinai School of Medicine
1 Gustave L. Levy Place, Box 1022
New York, NY 10029-6574
website: http://students.mssm.edu/millem14

e-mail: michael....@mssm.edu