Military forces have worn distinctive uniform items for centuries to create a psychological advantage and boost their esprit de corps, but the military use of berets is a relatively recent phenomenon. In the 16th and 17th centuries, the Blue Bonnet became a de facto symbol of Scottish Jacobite forces.
Muscle cells have adapted to their job by contracting and relaxing.  When calcium levels are increased the muscle cells contract. On the  other hand, when calcium levels droâ¦p the muscle cells get relaxed.
The muscular system. The muscular system is composed of specialized cells called muscle fibers. Their predominant function is contractibility. Muscles, attached to bones or internal organs and blood vessels, are responsible for movement.Nearly all movement in the body is the result of muscle contraction.Exceptions to this are the action of cilia, the flagellum on sperm cells, and amoeboid movement of some white blood cells.keletal muscle consists of voluntary muscles attached to the frame of the skeletal system enabling bodily movement. Smooth muscle is the involuntary muscle that enables the movement of internal organs.