Compléter 109-testVersion en ligne 109-test par Farhad Key 1 way pulses modes spinal switch pattern pattern contract In animals , movement is coordinated by a cluster of neurons in the cord called the central generator ( CPG ) . This produces signals that drive muscles to rhythmically in a that produces running or walking , depending on the of . A simple signal from the brain instructs the CPG to between different , such as going from a standstill to walking .