A motor programme is described for defensive kicking in the locust which is also probably
the programme for jumping. The method of analysis has been to make intracellular
recordings from the somata of identified motornuerones which control the metathoracic
tibiae while defensive kicks are made in response to tactile stimuli. Three stages are
recognized in the programme.(1) Initial flexion of the tibiae results from the low spike
threshold of tibial flexor motorneurones to tactile stimulation of the body.(2) Co-contraction of …

1. Neural circuits which co-ordinate the motorneurones of the meta-thoracic tibiae of the
locust in jumping and kicking have been investigated. 2. The fast extensor motorneurone is
reflexly excited by the subgenual organ, by a network of cuticle strain receptors, and by
Brunner9s organ. The subgenual organ and the cuticle strain receptors are excited by
tension in the extensor muscle and mediate a positive feedback which could help to produce
the burst of fast extensor spikes which precedes a jump or kick. Brunner9s organ is …

1. The flexor and extensor tibiae muscles of the mesothoracic leg have a constant lever ratio
of about 2: 1 throughout joint rotation. 2. The mesothoracic tibiae can only flex to 25° about
the femora, while the metathoracic tibiae, because of their specialized geometry, can flex
almost parallel to the femora. 3. Full metatibial flexion increases the mechanical advantage
of the flexor muscle relative to the extensor at full flexion, and increases the vertical
component of the thrust produced by tibial extension in a jump. 4. A region in the dorsal …