Graduate
Microanatomy, 1998
Graduate
Microanatomy, 1998
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Date page was last edited 05/14/99 |
Some definitions: Muscle fibers are cells specialized for motility. The interaction of actin and myosin filaments along with the calcium sequestering proteins are vital to functions of these cells. In skeletal muscle fiber, a single cell is long, cylinder and multinucleated. This multinucleated stated is called a syncitium. The other types of muscle cells (cardiac and smooth) each have one nucleus/cell. 1) What might be the advantage of a syncitium for the skeletal muscle fiber? 2) Body builders work a particular area of their body one day and then give it a rest, in order to promote development of more muscle mass. Do you know what is going on at the cellular level? Why would a multinucleated cell be an advantage? 3) Calcium is extremely important for contraction. (Recall Cell Biology lectures). However skeletal muscle fibers can be as wide as 70 micrometers (in diameter). What mechanism could the cells use to get the calcium to the microfilaments in the center of that huge cell? 4) If we break a leg or arm and it is in a cast for 6 weeks, often the muscle is smaller after the cast is taken off. What may be happening at the cellular level? 5) Cardiac muscle cells are connected by specialized junctions that allow them to function like a syncitium? What type(s) of junctions are in these cells. 6) Cardiac muscle cells require a pacemaker group of cells to allow contraction of the atria before the ventricles. In these cells, the microfilaments are scattered and most of the cell is filled with glycogen. Their conduction velocity is much faster than normal cardiac muscle cells (2/3 milliseconds, vs 0.6 milliseconds. What might contribute to this increased conduction velocity?
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