On the left are the stimuli that start swimming. On the right are the stimuli that stop swimming.
Circles are groups of neurons colour coded by the transmitter they release.
Blobs and triangles are inhibitory and excitatory synapses. For outline explanation see below. During swimming these neurons all fire a single action potential on each cycle of swimming. The alternation of activity is organised by glycinergic inhibition from commissural interneurons. After initiation, swimming activity is sustained by positive feedback excitation from glutamatergic descending interneurons and cholinergic motoneurons.