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.
One of those things you learning in history class that isnât necessarily true: It is a little-known but undisputed historical fact that Johannes Gutenberg did not invent the printing press. Though the Gutenberg Bible was certainly the first mass produced printed work, it was hardly the first printed book â nor was it even the first made using movable type.