Globalized evolution...... but I might be wrong
<span>In the "all or none" law of muscle contraction, it states that when the stimulus applied exceeds threshold then the the nerve sending signals to a few muscle fibers will give a complete response; contraction. Graded response is dependent on how many motor units have been recruited. The more motor units, the greater the force in the contraction.</span>
They have two pairs of main nerve cords organized around a number of paired ganglia. while they don't have a "true brain"-- they have somewhat of a nervous system, composed of the two, or three pairs of nerve cords contained in the visceral mass.
The correct answer is From east to west
