Fig. 5. The activity of leg motor neurones during a kick and the consequent distortions of the semi-lunar processes and tibial movements. Intracellular recordings are from the fast extensor tibiae motor neurone (FETi) and from a fast flexor tibiae motor neurone. The first spikes in the flexor motor neurone move the tibia into the fully flexed position. When the FETi motor neurone starts to spike, so that the extensor and flexor muscles are now co-contracting, the semi-lunar process begins to bend. The bending continues until the flexor motor neurones are inhibited and the semi-lunar processes unfurl during the rapid extension. The apparently stepwise bending of the semi-lunar process is an artefact of the limited resolution of the measurements of each image. The cross hairs in the images show the progressive bending during FETi spiking and the rapid unfurling once tibial extension has started.