The Princeton Review - Science Smart/SCIENCE.iso/mac/files/CAD.DiR/00748_Tendons (1).txt

Text File | 1995-12-08 | 1.0 KB | 14 lines

   Striated muscles are attached to bones by
means of tendons and effect the movement of
the body by bending the skeletal structure at
its moveable joints.  Where a muscle is
connected to two bones, the muscle's
contraction causes the movement of only one
of the bones; the other bone is held rigid by
other muscles.  The point where the muscle
joins the stationary bone is called the origin;
the point where the muscle joins the moving
 bone is called the insertion.  The bending of
joints is brought about by the pulling action of a muscle, never a pushing action, because muscles can only actively contract and cannot actively stretch themselves out.  In fact, all movement depends on antagonistically paired sets of muscles, where the contraction of one set causes the other set to stretch.  Whenever a stimulus is received, the nervous system sends impulses to both sets of muscles in the appropriate antagonistic pair, causing one set to contract and readying the other to contract if the initial movement need be reversed.