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.
February 2, 1468? Johannes Gutenberg, in full Johann Gensfleisch zur Laden zum Gutenberg (born 14th century, Mainz [Germany]âdied probably February 3, 1468, Mainz), German craftsman and inventor who originated a method of printing from movable type that was used without important change until the 20th century.