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.
The Story: Inventor of the printing press, Henne G nsfleisch zur Laden, commonly called Johannes Gutenberg, was born about 1400 and died in 1468 at Mainz, Germany. Gutenberg was the son of Friele (Friedrich) G nsfleisch and Else Wyrich.041 Bi Sheng in China invented movable clay type 1400 Johannes Gutenberg born in Mainz, Germany 1423 Europeans use xylography (art of engraving on wood, block printing) to produce books.