Such a contraction is called a twitch. Thus, each motor unit is either relaxed or each presynaptic action potential causes an action potential in all of the muscle fibers of the motor unit, causing them all to contract at once.In the whole muscle, contractions of different strengths necessarily are created by activating different numbers of motor units.hus, each motor unit is either relaxed or each presynaptic action potential causes an action potential in all of the muscle fibers of the motor unit, causing them all to contract at once. In the whole muscle, contractions of different strengths necessarily are created by activating different numbers of motor units.
Johannes Gutenberg of Mainz, Germany is acknowledged as the first to invent a metal movable-type printing system in Europe, the printing press.
Building on movable type in the 1450s, German goldsmith Johannes Gutenberg transformed society with mass printing, enabling the dispersal of information to the populace. This print invention is regarded by many as the invention of the millennium.rom then on practically all important books were produced by block printing. During the Ch'ing-li period (1041-1048) the printing technique was further advanced through the invention of movable type. However, even the greatest technology is constrained by cultural circumstances.