Fig. 7. A simplified diagram of the spinal cord C-start neural circuit modified from Fetcho and Faber (1988). In this diagram, the stimulus would be from the right and the fish would turn to the left. The Mauthner axon synapses with interneurons and motoneurons in the spinal cord. Directly and through excitatory interneurons (multiple known pathways indicated by a dashed line), the Mauthner cell excites motoneurons to generate the C-bend. Through commissural interneurons, it inhibits motoneuron activity on the opposite side of the body. The numbers of cells indicated in the diagram do not reflect the numbers or distributions in the fish, nor do they reflect the relative numbers of different cell types. Instead, they simply illustrate regional differences along the body.