Describe how striated muscle is attached to bone and how striated muscle effects movement. How is a movement reversed? Define the terms "origin" and "insertion."
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. 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 expand. 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. 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 relative to the rest of the body 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.
