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.
Johann Gutenberg invented the printing press in the 1450's, and the first book to ever be printed was a Latin language Bible, printed in Mainz, Germany.Gutenbergâs Bibles were surprisingly beautiful, as each leaf Gutenberg printed was later colorfully hand-illuminated.ohann Gutenberg invented the printing press in the 1450's, and the first book to ever be printed was a Latin language Bible, printed in Mainz, Germany. Gutenbergâs Bibles were surprisingly beautiful, as each leaf Gutenberg printed was later colorfully hand-illuminated.