Skeletal Muscle!

Okay, here we go with a microscopic look at the skeletal muscle. First the skeletal muscles in a human body are about 40% of the body weight according to my coloring packet. Inside the skeletal muscle you have a bundle of fibers. they are cylindrical striated cells called fibers. Next, is the cell, or muscle fiber. These can be very long because they extend from one bone to another. inside the muscle fibers is the myofibrils which are hundreds of banded cylindrical myofibrils that run the length of each cell. So this skeletal muscle is pretty much like a giant puzzle. Then of course you have actin filaments that are the proteins needed in the cell. You also have myosin filaments which are assemblies of protein molecules to make myosin. The contractile elements in the skeletal muscle are the A band, Thick filaments, I band, thin filaments (actin filaments), H zone, z line, and sacromere. The bands are responsible for the striations in the cell look. The thin filaments run vertical through the cell and the thick ones peripheral. They interact through the cross bridges which look like buds or little clams. When a muscle contracts the I band shortens and that makes the H zone shorten. Notice the thick and thin filaments do not change which means they never change length. So how exactly does it contract and where does it get the energy? For skeletal muscle fibers to contract: The fiber must be stimulated by a nerve ending, an action potential must be generated along the sarcolemma, the action potential must be propagated along the sarcolemma, and intracellular calcium levels must rise to trigger contraction. When the ACh is release it travels down the t tubules then Ach is broken down by acetylcholine esterase, which terminates stimulation of the sarcolemma. If we did not have muscle movements it could mean that we would never make our bodies warm or we would never be able to move! Some of the roles also include food digestion and the aid in blood flow so without the muscle system we would not be alive!

If you are interested in learning more visit:

My sources:
Class notes
Class coloring packet
google images


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